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Ventricular Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy (Analysis Spanning 60 Years Of Practice): AJC Expert Panel

Open AccessPublished:August 11, 2022DOI:https://doi.org/10.1016/j.amjcard.2022.06.007
      Surgical myectomy remains the time-honored primary treatment for hypertrophic cardiomyopathy patients with drug refractory limiting symptoms due to LV outflow obstruction. Based on >50 years experience, surgery reliably reverses disabling heart failure by permanently abolishing mechanical outflow impedance and mitral regurgitation, with normalization of LV pressures and preserved systolic function. A consortium of 10 international currently active myectomy centers report about 11,000 operations, increasing significantly in number over the most recent 15 years. Performed in experienced multidisciplinary institutions, perioperative mortality for myectomy has declined to 0.6%, becoming one of the safest currently performed open-heart procedures. Extended myectomy relieves symptoms in >90% of patients by ≥ 1 NYHA functional class, returning most to normal daily activity, and also with a long-term survival benefit; concomitant Cox-Maze procedure can reduce the number of atrial fibrillation episodes. Surgery, preferably performed in high volume clinical environments, continues to flourish as a guideline-based and preferred high benefit: low treatment risk option for adults and children with drug refractory disabling symptoms from obstruction, despite prior challenges: higher operative mortality/skepticism in 1960s/1970s; dual-chamber pacing in 1990s, alcohol ablation in 2000s, and now introduction of novel negative inotropic drugs potentially useful for symptom management.

      Introduction

      The septal myectomy operation for symptomatic obstructive hypertrophic cardiomyopathy (HCM) is now 60 years old having stood the test of time based on its effectiveness in relieving marked LV outflow gradients and disabling drug-refractory symptoms with functional limitation.
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      • Wei LM
      • Thibault DP
      • Rankin JS
      • Alkhouli M
      • Roberts HG
      • Vemulapalli S
      • Yerokun B
      • Ad N
      • Schaff HV
      • Smedira NG
      • Takayama H
      • McCarthy PM
      • Thourani VH
      • Ailawadi G
      • Jacobs JP
      • Badhwar V.
      Contemporary surgical management of hypertrophic cardiomyopathy in the United States.
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      • Morrow AG
      • Reitz BA
      • Epstein SE
      • Henry WL
      • Conkle DM
      • Itscoitz SB
      • Redwood DR.
      Operative treatment in hypertrophic subaortic stenosis. Techniques and the results of pre and postoperative assessments in 83 patients.
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      Myectomy has not been immune from controversy, and has resisted periodic challenges and obstacles over 6 decades, including proclamations of its eminent demise on at least two occasions,
      • Ross J
      • Braunwald E
      • Gault JH
      • Mason DT
      • Morrow AG.
      The mechanisms of the intraventicular pressure gradient in idiopathic hypertrophic subaortic stenosis.
      • Murgo JP
      • Alter JF
      • Dorethy SA
      • Altobelli SA
      • McGranahan GM.
      Dynamics of left ventricular ejection in obstructive and nonobstructive hypertrophic cardiomyopathy.
      • Hess OM
      • Sigwart U.
      New treatment strategies for hypertrophic obstructive cardiomyopathy.
      skepticism regarding even the existence of mechanical impedance to LV outflow,
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      ,
      • Ross J
      • Braunwald E
      • Gault JH
      • Mason DT
      • Morrow AG.
      The mechanisms of the intraventicular pressure gradient in idiopathic hypertrophic subaortic stenosis.
      ,
      • Murgo JP
      • Alter JF
      • Dorethy SA
      • Altobelli SA
      • McGranahan GM.
      Dynamics of left ventricular ejection in obstructive and nonobstructive hypertrophic cardiomyopathy.
      an early period of excessive operative mortality that clouded its initial reputation,
      • Maron BJ
      • Epstein SE
      • Morrow AG.
      Symptomatic status and prognosis of patients after operation for hypertrophic obstructive cardiomyopathy: Efficacy of ventricular septal myotomy and myectomy.
      brief promotion of mitral valve replacement
      • Cooley DA
      • Wukasch DC
      • Leachman RD.
      Mitral valve replacement for idiopathic hypertrophic subaortic stenosis. Results in 27 patients.
      or dual chamber pacing as alternatives,
      • Kappenberger L
      • Linde C
      • Daubert C
      • Kappenberger L
      • Linde C
      • Daubert C
      • McKenna W
      • Meisel E
      • Sadoul N
      • Chojnowska L
      • Guize L
      • Gras D
      • Jeanrenaud X
      • Rydén L.
      Pacing in hypertrophic obstructive cardiomyopathy. A randomized crossover study.
      • Maron BJ
      • Nishimura RA
      • McKenna WJ
      • Rakowski H
      • Josephson ME
      • Kieval RS.
      Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy: a randomized, double-blind cross-over study (M-PATHY).
      • Ommen SR
      • Nishimura RA
      • Squires RW.
      • Schaff HV
      • Danielson GK
      • Tajik AJ.
      Comparison of dual-chamber pacing versus septal myectomy for the treatment of patients with hypertrophic obstructive cardiomyopathy.
      and the interventional cardiology community promoting alcohol septal ablation as a primary treatment for symptomatic obstruction.
      • Batzner A
      • Pfeiffer B
      • Neugebauer A
      • Aicha D
      • Blank C
      • Seggewiss H.
      Survival after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy.
      • Sigwart U.
      Non-surgical reduction for hypertrophic obstructive cardiomyopathy.
      • Sorajja P.
      Alcohol septal ablation for obstructive hypertrophic cardiomyopathy: A word of balance.
      Nevertheless, septal myectomy operation has evolved technically and flourished, achieving global reach with an increasing case volume shaped by the experience of multiple specialized centers in thousands of patients. With emerging interest in new medical therapies (e.g., novel negative inotropic drugs)
      • Olivotto I
      • Oreziak A
      • Barriales-Villa R
      • Abraham TP
      • Masri A
      • Garcia-Pavia P
      • Saberi S
      • Lakdawala NK
      • Wheeler MT
      • Owens A
      • Kubanek M
      • Wojakowski W
      • Jensen MK
      • Gimeno-Blanes J
      • Afshar K
      • Myers J
      • Hegde SM
      • Solomon SD
      • Sehnert AJ
      • Zhang D
      • Li W
      • Bhattacharya M
      • Edelberg JM
      • Waldman CB
      • Lester SJ
      • Wang A
      • Ho CY
      • Jacoby D.
      Mavacamten for treatment of symptomatic obstructive hypertrophic cardiomyopathy (EXPLORER-HCM): a randomized, double-blind, placebo-controlled phase 3 trial.
      for obstructive HCM patients who are otherwise candidates for invasive procedures such as myectomy, we believe that it is an opportune time to underscore and place in perspective the important continuing role of surgery in the management armamentarium of this complex often inherited disease. Myectomy surgery for obstruction is viewed comprehensively past, present and future through the prism of an extensive literature and cumulative clinical experience acquired over several decades by a broad range of experts including cardiologists and dedicated myectomy surgeons.

      Historical Perspectives (Figure 1)

      Sixty years ago when surgical myectomy was first introduced for symptomatic patients with obstructive HCM, it was viewed as a revolutionary strategy for a new disease, as part of the first comprehensive disease description by the Braunwald group at the National Institutes of Health (NIH).
      • Braunwald E
      • Lambrew E
      • Rockoff D
      • Ross Jr, J
      • Morrow AG.
      Idiopathic hypertrophic subaortic stenosis: I: A description of the disease based upon an analysis of 64 patients.
      The earliest surgical pioneer was Andrew Glenn Morrow who performed the myectomy operation from the early 1960s on 310 patients at NIH,
      • Morrow AG
      • Reitz BA
      • Epstein SE
      • Henry WL
      • Conkle DM
      • Itscoitz SB
      • Redwood DR.
      Operative treatment in hypertrophic subaortic stenosis. Techniques and the results of pre and postoperative assessments in 83 patients.
      remarkably while himself symptomatically affected by the same disease.
      • Maron BJ
      • Roberts WC.
      The father of septal myectomy for obstructive HCM, who also had HCM: The unbelievable story.
      One of the oldest open-heart procedures, septal myectomy has evolved from the classic “Morrow procedure” with removal of muscle from the proximal anterior ventricular septum, to the widely adopted more extended resection distally first described by Messmer
      • Messmer BJ.
      Extended myectomy for hypertrophic obstructive cardiomyopathy.
      ,
      • Schoendube FA
      • Klues HG
      • Reith S
      • Flachskampf FA
      • Hanrath P
      • Messmer BJ.
      Long-term clinical and echocardiographic follow-up after surgical correction of hypertrophic obstructive cardiomyopathy with extended myectomy and reconstruction of the subvalvular mitral apparatus.
      and now frequently associated with remodeling and repair of the mitral valve by some surgeons.
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      ,
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      ,
      • Balaram SK
      • Ross RE
      • Sherrid M
      • Schwartz GS
      • Hillel Z
      • Winson G
      • Swistel DG.
      Role of mitral valve plication in the surgical management of hypertrophic cardiomyopathy.
      • Varma PK
      • Krishna N
      • Ahamed H
      • Madassery S.
      Posterior mitral leaflet plication for hypertrophic obstructive cardiomyopathy.
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      Initially, myectomy operations were infrequent as cardiac surgeons were hesitant to adopt this new procedure in which exposure of the operative field is restricted by the small operative window permitted by the aortotomy approach. Also, several misconceptions became early obstacles to acceptance of surgery for HCM in the 1960s even before myectomy could achieve a clinical foothold. For example, a small series of unsuccessful operations performed in the U.K. (Hammersmith Hospital; London),
      • Cleland WP.
      The surgical management of obstructive cardiomyopathy.
      caused surgery to fall out of favor there, as early investigators came to regard myectomy as a damaging and high-risk procedure that did not resolve LV filling abnormalities. In addition, skepticism and highly visible but now long forgotten debates arose in the mid-1960s
      • Ross J
      • Braunwald E
      • Gault JH
      • Mason DT
      • Morrow AG.
      The mechanisms of the intraventicular pressure gradient in idiopathic hypertrophic subaortic stenosis.
      (and once again 20 years later)
      • Murgo JP
      • Alter JF
      • Dorethy SA
      • Altobelli SA
      • McGranahan GM.
      Dynamics of left ventricular ejection in obstructive and nonobstructive hypertrophic cardiomyopathy.
      questioning the very legitimacy and clinical significance of outflow gradients, and therefore the value of surgery
      • Murgo JP
      • Alter JF
      • Dorethy SA
      • Altobelli SA
      • McGranahan GM.
      Dynamics of left ventricular ejection in obstructive and nonobstructive hypertrophic cardiomyopathy.
      (Figure 1). Nevertheless, septal myectomy (or myotomy in some early cases) was soon adopted in a growing number of centers by other pioneers of the operation i.e, Mayo Clinic (Kirklin)
      • Kirklin JW
      • Ellis Jr, RH
      Surgical relief of diffuse subvalvular aortic stenosis.
      ; Toronto (Bigelow; Williams),
      • Williams WG
      • Wigle ED
      • Rakowski H
      • Smallhorn J
      • LeBlanc J
      • Trusler GA.
      Results of surgery for hypertrophic obstructive cardiomyopathy.
      ,
      • Bigelow WG
      • Trimble AS
      • Auger P
      • Marquis Wigle ED
      The ventriculomyotomy operation for muscular subaortic stenosis.
      New Zealand (Barrat-Boyes)
      • Agnew TM
      • Barratt-Boyes BG
      • Brandt PW
      • Roche AH
      • Lowe JB
      • O'Brien KP
      Surgical resection in idiopathic hypertrophic cardiomyopathy subaortic stenosis with a combined approach through aorta and left ventricular.
      ; Germany (Shulte; Messmer; Schoendube)
      • Messmer BJ.
      Extended myectomy for hypertrophic obstructive cardiomyopathy.
      ,
      • Schoendube FA
      • Klues HG
      • Reith S
      • Flachskampf FA
      • Hanrath P
      • Messmer BJ.
      Long-term clinical and echocardiographic follow-up after surgical correction of hypertrophic obstructive cardiomyopathy with extended myectomy and reconstruction of the subvalvular mitral apparatus.
      ,
      • Schulte HD
      • Borisov K
      • Gams E
      • Gramsch-Zabel H
      • Lösse B
      • Schwartzkopff B.
      Management of symptomatic hypertrophic obstructive cardiomyopathy–long-term results after surgical therapy.
      ; and Switzerland (Senning; Turina).
      • Schonbeck MH
      • Brunner-LaRocca HP
      • Vogt PR
      • Lachat ML
      • Jenni R
      • Hess OM
      • Turina MI
      Long-term follow-up in hypertrophic obstructive cardiomyopathy after septal myectomy.
      Figure 1
      Figure 1Evolution of the septal myectomy operation in hypertrophic cardiomyopathy. Timeline of relevant and key clinical events and landmarks. ACC = American College of Cardiology; AHA = American Heart Association; HCM = hypertrophic cardiomyopathy; NIH = National Institutes of Health; MV = mitral valve; SAM = systolic anterior motion.
      However, some resistance to surgical myectomy re-emerged, based on 3 developments:
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      transient enthusiasm for dual-chamber pacing as an alternative approach (1992-1994)
      • Kappenberger L
      • Linde C
      • Daubert C
      • Kappenberger L
      • Linde C
      • Daubert C
      • McKenna W
      • Meisel E
      • Sadoul N
      • Chojnowska L
      • Guize L
      • Gras D
      • Jeanrenaud X
      • Rydén L.
      Pacing in hypertrophic obstructive cardiomyopathy. A randomized crossover study.
      albeit highly controversial
      • Fananapazir L
      • Epstein ND
      • Curiel RV
      • Panza JA
      • Tripodi D
      • McAreavey D.
      Long-term results of dual chamber (DDD) pacing in obstructive hypertrophic cardiomyopathy. Evidence for progressive symptomatic and hemodynamic improvement and reduction of left-ventricular hypertrophy.
      with clinical effects ultimately explained largely as a placebo effect
      • Maron BJ
      • Nishimura RA
      • McKenna WJ
      • Rakowski H
      • Josephson ME
      • Kieval RS.
      Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy: a randomized, double-blind cross-over study (M-PATHY).
      ,
      • Ommen SR
      • Nishimura RA
      • Squires RW.
      • Schaff HV
      • Danielson GK
      • Tajik AJ.
      Comparison of dual-chamber pacing versus septal myectomy for the treatment of patients with hypertrophic obstructive cardiomyopathy.
      ,
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      ; recognition of early and relatively high postoperative mortality (up to 8%)
      • Maron BJ
      • Epstein SE
      • Morrow AG.
      Symptomatic status and prognosis of patients after operation for hypertrophic obstructive cardiomyopathy: Efficacy of ventricular septal myotomy and myectomy.
      , which has been reduced dramatically (to 0.6%)
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      ; and introduction in 1995 of a percutaneous alternative to surgery (alcohol septal ablation; ASA) to relieve outflow obstruction and symptoms.
      • Batzner A
      • Pfeiffer B
      • Neugebauer A
      • Aicha D
      • Blank C
      • Seggewiss H.
      Survival after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy.
      • Sigwart U.
      Non-surgical reduction for hypertrophic obstructive cardiomyopathy.
      • Sorajja P.
      Alcohol septal ablation for obstructive hypertrophic cardiomyopathy: A word of balance.
      ,
      • Liebregts M
      • Vriesendorp PA
      • Mahmoodi BK
      • Schinkel AFL
      • Michels M
      • ten Berg JM.
      A systematic review and meta-analysis of long-term outcomes after septal reduction therapy in patients with hypertrophic cardiomyopathy.
      An undesirable consequence of the competitive ASA era has been virtual abandonment of surgical myectomy in much of Europe, albeit with some recent revival in Italy,
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      essentially creating a lost generation of surgeons with myectomy expertise and also mentoring necessary to perpetuate the operation. This potentially deprives patients of access to treatment options they deserve and the opportunity to substantially improve their quality of life and prognosis.
      • Iacovoni A
      • Spirito P
      • Simon C
      • Iascone M
      • Di Dedda G
      • De Filippo P
      • Pentiricci S
      • Boni L
      • Senni M
      • Gavazzi A
      • Ferrazzi P.
      A contemporary European experience with surgical septal myectomy in hypertrophic cardiomyopathy.
      As an example, while the current German experience with myectomy is negligible, it was once one of the largest in the world when Hagen Shulte operated successfully on >500 patients in Dusseldorf until the late 1990s.
      • Schulte HD
      • Borisov K
      • Gams E
      • Gramsch-Zabel H
      • Lösse B
      • Schwartzkopff B.
      Management of symptomatic hypertrophic obstructive cardiomyopathy–long-term results after surgical therapy.
      Indeed, by year 2000, many other productive myectomy centers had virtually disappeared or were greatly reduced both in Europe: Switzerland (Zurich)
      • Schonbeck MH
      • Brunner-LaRocca HP
      • Vogt PR
      • Lachat ML
      • Jenni R
      • Hess OM
      • Turina MI
      Long-term follow-up in hypertrophic obstructive cardiomyopathy after septal myectomy.
      ; Netherlands (Rotterdam; ThoraxCenter)
      • Ten Berg JM
      • Suttorp MJ
      • Knaepen PJ
      • Ernst SM
      • Vermeulen FE
      • Jaarsma W
      Hypertrophic obstructive cardiomyopathy initial results and long-term follow-up after Morrow septal myectomy.
      , but also in some U.S. institutions: Stanford, Brigham and Women's, and Vanderbilt,
      • Robbins RC
      • Stinson EB.
      Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy.
      • Cohn LH
      • Trehan H
      • Collins Jr, JJ
      Long-term follow-up of patients undergoing myotomy/myectomy for obstructive hypertrophic cardiomyopathy.
      • Merrill WH
      • Friesinger GC
      • Graham TP
      • Byrd 3rd, BF
      • Drinkwater Jr, DC
      • Christian KG
      • Bender Jr., HW
      Long-lasting improvement after septal myectomy for hypertrophic obstructive cardiomyopathy.
      and termination of the NIH myectomy program abandoned by U.S. government in 1993.

      Principles of septal myectomy

      Pathophysiology and mechanisms of obstruction

      The mitral valve is the fundamental element in generating dynamic LV outflow gradients in most patients with the obstructive form of HCM, by virtue of systolic anterior motion (SAM) and prolonged septal contact,
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      first demonstrated by Shah et al. in 1969 with M-mode echocardiography.
      • Shah PM
      • Gramiak R
      • Kramer DH.
      Ultrasound localization of left ventricular outflow obstruction in hypertrophic cardiomyopathy.
      Contemporary imaging with advanced echocardiography and CMR
      • Rowin EJ
      • Maron BJ
      • Maron MS.
      The hypertrophic cardiomyopathy phenotype viewed through the prism of multimodality imaging: clinical and etiologic implications.
      has detailed mitral valve morphology as well as the mechanisms by which the leaflets produce dynamic obstruction
      • Maron MS
      • Olivotto I
      • Harrigan C
      • Appelbaum E
      • Gibson CM
      • Lesser JR
      • Haas TS
      • Udelson JE
      • Manning WJ
      • Maron BJ.
      Mitral valve abnormalities identified by cardiovascular magnetic resonance represent a primary phenotypic expression of hypertrophic cardiomyopathy.
      (Figure 2). For example, relevant to surgery: echocardiography,
      • Grigg LE
      • Wigle ED
      • Williams WG
      • Daniel LB
      • Rakowski H.
      Transesophageal Doppler echocardiography in obstructive hypertrophic cardiomyopathy: clarification of pathophysiology and importance in intraoperative decision-making.
      CMR
      • Rowin EJ
      • Maron BJ
      • Maron MS.
      The hypertrophic cardiomyopathy phenotype viewed through the prism of multimodality imaging: clinical and etiologic implications.
      ,
      • Maron MS
      • Olivotto I
      • Harrigan C
      • Appelbaum E
      • Gibson CM
      • Lesser JR
      • Haas TS
      • Udelson JE
      • Manning WJ
      • Maron BJ.
      Mitral valve abnormalities identified by cardiovascular magnetic resonance represent a primary phenotypic expression of hypertrophic cardiomyopathy.
      and pathology
      • Klues HG
      • Maron BJ
      • Dollar AL
      • Roberts WC.
      Diversity of structural mitral valve alterations in hypertrophic cardiomyopathy.
      have defined abnormal mitral valve structure as a primary phenotypic disease expression characterized by elongation of anterior and/or posterior leaflets up to 30-40 mm in length, most marked with obstruction.
      • Maron MS
      • Olivotto I
      • Harrigan C
      • Appelbaum E
      • Gibson CM
      • Lesser JR
      • Haas TS
      • Udelson JE
      • Manning WJ
      • Maron BJ.
      Mitral valve abnormalities identified by cardiovascular magnetic resonance represent a primary phenotypic expression of hypertrophic cardiomyopathy.
      ,
      • Klues HG
      • Maron BJ
      • Dollar AL
      • Roberts WC.
      Diversity of structural mitral valve alterations in hypertrophic cardiomyopathy.
      Figure 2
      Figure 2Mechanisms of outflow obstruction pre and post-myectomy with imaging. A-D, H. preoperative; E-G. postoperative. A. typical mechanism of outflow obstruction due to mitral valve systolic anterior motion (SAM) and anterior leaflet-septal contact (red arrow); B. Posteriorly directed mitral regurgitation jet (white arrow), secondary to outflow gradient with incomplete mitral leaflet cooptation; C. Greatly elongated anterior mitral leaflet almost 4 cm in length, responsible for subaortic obstruction; D. Anomalous insertion of anterolateral papillary muscle (small arrows) directly into anterior mitral leaflet (larger arrow) producing muscular mid-cavity obstruction; E. margins of myectomy resection (orange arrowheads), with typical marked reduction in anterior septal thickness; F. absence of mitral regurgitation after myectomy; G. plication suture in anterior mitral leaflet to restrict systolic motion (bright image; red arrow); H. apical-basal muscle bundle that can contribute to outflow obstruction.
      Abbreviations: AO = aorta; LA = left atrium; LV = left ventricle; VS = ventricular septum.
      The rationale for myectomy is to relieve mechanical subaortic obstruction and normalize LV pressures by enlarging the small cross-sectional area of the outflow tract
      • Spirito P
      • Maron BJ
      • Rosing DR.
      Morphologic determinants of hemodynamic state after ventricular septal myectomy-myectomy in patients with obstructive cardiomyopathy. M-mode and two-dimensional echocardiographic assessment.
      and abolishing or minimizing SAM. In the vast majority of instances, it is the anterior leaflet that makes septal contact, but occasionally preferential posterior leaflet apposition with the septum is responsible for subaortic obstruction.
      • Varma PK
      • Krishna N
      • Ahamed H
      • Madassery S.
      Posterior mitral leaflet plication for hypertrophic obstructive cardiomyopathy.
      ,
      • Maron BJ
      • Harding AM
      • Spirito P
      • Roberts WC
      • Waller BF.
      Systolic anterior motion of the posterior mitral leaflet: A previously unrecognized cause of dynamic subaortic obstruction in patients with hypertrophic cardiomyopathy.
      ,
      • Klues HG
      • Roberts WC
      • Maron BJ.
      Morphological determinants of echocardiographic patterns of mitral valve systolic anterior motion in obstructive hypertrophic cardiomyopathy.
      Mechanical outflow obstruction occurs when the ejection stream exerts a pushing force of flow drag on the mitral valve causing the leaflets to move forward (anteriorly) toward ventricular septum, thereby elevating LV systolic pressure associated with a mild-to-moderate posteriorly directed mitral regurgitation jet caused by incomplete leaflet coaptation (Figure 2).
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      Myectomy re-directs the blood stream away from the anteriorly positioned mitral leaflets to effectively eliminate flow drag directly on the valve mitigating SAM and mitral regurgitation. SAM and mitral- septal contact must be present before recommending myectomy in the vast majority of cases since small hyperdynamic LV with cavity obliteration can be associated with false positive Doppler velocities that do not necessarily represent true mechanical obstruction.
      Diverse patterns of SAM have been recognized
      • Klues HG
      • Maron BJ
      • Dollar AL
      • Roberts WC.
      Diversity of structural mitral valve alterations in hypertrophic cardiomyopathy.
      ,
      • Maron BJ
      • Harding AM
      • Spirito P
      • Roberts WC
      • Waller BF.
      Systolic anterior motion of the posterior mitral leaflet: A previously unrecognized cause of dynamic subaortic obstruction in patients with hypertrophic cardiomyopathy.
      ,
      • Klues HG
      • Roberts WC
      • Maron BJ.
      Morphological determinants of echocardiographic patterns of mitral valve systolic anterior motion in obstructive hypertrophic cardiomyopathy.
      as mechanisms for LV outflow obstruction, i.e., in younger patients with greatly elongated anterior mitral leaflets demonstrating the classic acute-angled bend with septal contact, or in older patients when anteriorly displaced mitral valve leaflets of normal length with flat excursion produce systolic septal contact which is facilitated by posterior excursion of septum. Recently, a shift of the anterior mitral leaflet toward the distal LV has been identified as a consequence of post-natal persistence of muscular mitral-aortic discontinuity, potentially contributing to outflow gradients.
      • Ferrazzi P
      • Spirito P
      • Binaco I
      • Zyrianov A
      • Poggio D
      • Vaccari G
      • Grillo M
      • Pezzoli L
      • Scatigno A
      • Dorobantu L
      • Mortara A
      • Bruzzi P
      • Boni L
      • Iascone M.
      Congenital muscular mitral-aortic discontinuity identified in patients with obstructive hypertrophic cardiomyopathy.

      Selection of patients

      Surgical myectomy is recommended as the primary and preferred treatment option to relieve LV outflow tract obstruction, consistent with the 2020 AHA/ACC and other management guidelines.
      • Maron BJ
      • McKenna WJ
      • Danielson GK
      • Kappenberger LJ
      • Kuhn HJ
      • Seidman CE
      • Shah PM
      • Spencer 3rd, WH
      • Spirito P
      • Ten Cate FJ
      • Wigle ED
      American College of Cardiology/European Society of Cardiology clinical expert consensus document of hypertrophic cardiomyopathy.
      • Gersh BJ
      • Maron BJ
      • Bonow RO
      • Dearani JA
      • Fifer MA
      • Link MS
      • Naidu SS
      • Nishimura RA
      • Ommen SR
      • Rakowski H
      • Seidman CE
      • Towbin JA
      • Udelson JE
      • Yancy CW.
      2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy.
      • Elliott PM
      • Anastasakis A
      • Borger MA
      • Borggrefe M
      • Cecchi F
      • Charron P
      • Hagege AA
      • Lafont A
      • Limongelli G
      • Mahrholdt H
      • McKenna WJ
      • Mogensen J
      • Nihoyannopoulos P
      • Nistri S
      • Pieper PG
      • Pieske B
      • Rapezzi C
      • Rutten FH
      • Tillmanns C
      • Watkins H.
      2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy.
      • Ommen SR
      • Mital S
      • Burke MA
      • Day SM
      • Deswal A
      • Elliott P
      • Evanovich LL
      • Hung J
      • Joglar JA
      • Kantor P
      • Kimmelstiel C
      • Kittleson M
      • Link MS
      • Maron MS
      • Martinez MW
      • Miyake CY
      • Schaff HV
      • Semsarian C
      • Sorajja P.
      2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy.
      Indications for the myectomy operation have been consistent in practice through the years, i.e., progressive heart failure disabling symptoms of exertional dyspnea (with or without chest pain) that interferes with a patient's desired lifestyle (usually NYHA class III/IV), refractory to maximum medical management and due to LV outflow gradient ≥ 50 mmHg at rest and/or with physiologic exercise provocation.
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      ,
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      ,
      • Maron BJ
      • McKenna WJ
      • Danielson GK
      • Kappenberger LJ
      • Kuhn HJ
      • Seidman CE
      • Shah PM
      • Spencer 3rd, WH
      • Spirito P
      • Ten Cate FJ
      • Wigle ED
      American College of Cardiology/European Society of Cardiology clinical expert consensus document of hypertrophic cardiomyopathy.
      • Gersh BJ
      • Maron BJ
      • Bonow RO
      • Dearani JA
      • Fifer MA
      • Link MS
      • Naidu SS
      • Nishimura RA
      • Ommen SR
      • Rakowski H
      • Seidman CE
      • Towbin JA
      • Udelson JE
      • Yancy CW.
      2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy.
      • Elliott PM
      • Anastasakis A
      • Borger MA
      • Borggrefe M
      • Cecchi F
      • Charron P
      • Hagege AA
      • Lafont A
      • Limongelli G
      • Mahrholdt H
      • McKenna WJ
      • Mogensen J
      • Nihoyannopoulos P
      • Nistri S
      • Pieper PG
      • Pieske B
      • Rapezzi C
      • Rutten FH
      • Tillmanns C
      • Watkins H.
      2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy.
      • Ommen SR
      • Mital S
      • Burke MA
      • Day SM
      • Deswal A
      • Elliott P
      • Evanovich LL
      • Hung J
      • Joglar JA
      • Kantor P
      • Kimmelstiel C
      • Kittleson M
      • Link MS
      • Maron MS
      • Martinez MW
      • Miyake CY
      • Schaff HV
      • Semsarian C
      • Sorajja P.
      2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy.
      • Maron MS
      • Olivotto I
      • Betocchi S
      • Casey SA
      • Lesser JR
      • Losi MA
      • Cecchi F
      • Maron BJ.
      Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy.
      • Maron MS
      • Olivotto I
      • Zenovich AG
      • Link MS
      • Pandian NG
      • Kuvin JT
      • Nistri S
      • Cecchi F
      • Udelson JE
      • Maron BJ.
      Hypertrophic cardiomyopathy is predominantly a disease of left ventricular outflow tract obstruction.
      This functional assessment is usually made reliably by conventional targeted history-taking, although some investigators favor supplementation with objective exercise testing.
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      ,
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Maron BJ
      • McKenna WJ
      • Danielson GK
      • Kappenberger LJ
      • Kuhn HJ
      • Seidman CE
      • Shah PM
      • Spencer 3rd, WH
      • Spirito P
      • Ten Cate FJ
      • Wigle ED
      American College of Cardiology/European Society of Cardiology clinical expert consensus document of hypertrophic cardiomyopathy.
      ,
      • Gersh BJ
      • Maron BJ
      • Bonow RO
      • Dearani JA
      • Fifer MA
      • Link MS
      • Naidu SS
      • Nishimura RA
      • Ommen SR
      • Rakowski H
      • Seidman CE
      • Towbin JA
      • Udelson JE
      • Yancy CW.
      2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy.
      In those occasional patients unable to exercise maximally for a variety of reasons, gradients estimated by Valsalva maneuver or occasionally by infusion of sympathomimetic drugs (isoproterenol or dobutamine), can be considered clinically relevant and actionable.
      • Maron BJ
      • Rowin EJ
      • Udelson JE
      • Maron MS.
      Clinical spectrum and management of heart failure in hypertrophic cardiomyopathy.
      Myectomy has been under-utilized or delayed in minorities and women, who often come to surgery with more advanced heart failure (HF) symptoms at older ages.
      • Meghji Z
      • Nguyen A
      • Fatima B
      • Geske JB
      • Nishimura RA
      • Ommen SR
      • Lahr BD
      • Dearani JA
      • Schaff HV.
      Survival differences in women and men after septal myectomy for obstructive hypertrophic cardiomyopathy.
      ,
      • Wells S
      • Rowin EJ
      • Bhatt V
      • Maron MS
      • Maron BJ.
      Association between race and clinical profile of patients referred for hypertrophic cardiomyopathy.
      Recently, some experienced centers have offered earlier surgical intervention to selected patients with less symptomatic limitation (consistent with NYHA class II) to avoid future adverse consequences of chronically elevated LV pressures and wall stress, such as diminishing functional capacity and quality of life.
      • Maron MS
      • Spirito P
      • Maron BJ.
      Case for earlier surgical myectomy in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Alashi A
      • Smedira NG
      • Hodges K
      • Popovic ZB
      • Thamilarasan M
      • Wierup P
      • Lever HM
      • Desai MY.
      Outcomes in guidelines-based class I indication versus earlier referral for surgical myectomy in hypertrophic obstructive cardiomyopathy.
      This consideration may apply to patients with unexplained syncope, or frequent paroxysmal atrial fibrillation (AF) episodes who are eligible for the Maze procedure.
      • Maron MS
      • Spirito P
      • Maron BJ.
      Case for earlier surgical myectomy in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Alashi A
      • Smedira NG
      • Hodges K
      • Popovic ZB
      • Thamilarasan M
      • Wierup P
      • Lever HM
      • Desai MY.
      Outcomes in guidelines-based class I indication versus earlier referral for surgical myectomy in hypertrophic obstructive cardiomyopathy.
      Surgical strategies (Figure 3). The septal myectomy operation to relieve LV outflow obstruction and restore normal intracavitary pressures is performed through a transaortic (aortotomy) exposure, although very occasionally with combined transapical and transaortic approaches when mid-ventricular anatomy is particularly complex.
      • Hang D
      • Schaff HV
      • Ommen SR
      • Dearani JA
      • Nishimura RA.
      Combined transaortic and transapical approach to septal myectomy in patients with complex hypertrophic cardiomyopathy.
      A wide muscular excision and trough is extended longitudinally from just below aortic anulus to mid-ventricle at papillary muscle level well beyond the site of mitral-septal contact, and often laterally; the myectomy resection does not produce intra-myocardial scarring (Figure 3).
      Figure 3
      Figure 3LV anatomy and the myectomy operation. Top. Prior to muscular resection showing hypertrophied anterior septum bulging characteristically into LV outflow tract. Anomalous fibrous attachments are evident between side of anterior mitral leaflet and basal LV free wall; A. (bottom left) classic Morrow procedure trough after muscular resection; B. (bottom center) wide and more distal myectomy, extends past the base of papillary muscles, as currently practiced (arrows). C. Muscle sample removed from ventricular septum at myectomy (weight about 6 grams). Reproduced with permission of authors.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      Surgery has the distinct advantage of affording direct visualization of the uniquely complex and heterogeneous LV chamber morphology and primary mechanisms responsible for subaortic gradients, some of which may not be anticipated by preoperative imaging, including tailoring the muscular resection and addressing mitral valve structure and function.
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      ,
      • Rowin EJ
      • Maron BJ
      • Maron MS.
      The hypertrophic cardiomyopathy phenotype viewed through the prism of multimodality imaging: clinical and etiologic implications.
      In this regard, myectomy is usually accompanied by intra-operative real time transesophageal echocardiography
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Grigg LE
      • Wigle ED
      • Williams WG
      • Daniel LB
      • Rakowski H.
      Transesophageal Doppler echocardiography in obstructive hypertrophic cardiomyopathy: clarification of pathophysiology and importance in intraoperative decision-making.
      ,
      • Ommen SR
      • Park SH
      • Click RL
      • Freeman WK
      • Schaff HV
      • Tajik AJ.
      Impact of intraoperative transesophogeal echocardiography in the surgical management of hypertrophic cardiomyopathy.
      ,
      • Nampiaparampil RG
      • Swistel DG
      • Schlame M
      • Saric M
      • Sherrid MV.
      Interoperative two and three dimensional transesophageal echocardiography in combined myectomy-mitral operations for hypertrophic cardiomyopathy.
      performed immediately before and again after the operative procedure and re-institution of cardiopulmonary bypass. At this time, the heart is interrogated for mitral regurgitation and residual obstruction either under basal conditions or after provocation with dobutamine or isoproterenol infusion. Persistent gradients due to mitral-septal contact evident by Doppler echocardiography and/or direct hemodynamic measurements are usually due to failure to adequately extend the myectomy resection distally. In such instances (<5% of operations) it is necessary to re-institute cardiopulmonary bypass to rectify persistent obstruction, usually with a more extensive myectomy.
      • Ommen SR
      • Park SH
      • Click RL
      • Freeman WK
      • Schaff HV
      • Tajik AJ.
      Impact of intraoperative transesophogeal echocardiography in the surgical management of hypertrophic cardiomyopathy.
      CMR is also useful for preoperative planning before invasive septal reduction to define outflow tract functional anatomy.
      • Spirito P
      • Binaco I
      • Poggio D
      • Zyrianov A
      • Grillo M
      • Pezzoli L
      • Rossi J
      • Malanin D
      • Vaccari G
      • Dorobantu L
      • Iascone M
      • Mortara A
      • Khouri T
      • Bruzzi P
      • Ferrazzi P.
      Role of preoperative cardiovascular magnetic resonance in planning ventricular septal myectomy in patients with obstructive hypertrophic cardiomyopathy.
      Mitral valve replacement, although briefly popular many years ago,
      • Roberts WC.
      Operative treatment of hypertrophic cardiomyopathy: the case against mitral valve replacement.
      is now largely avoided in the management of symptomatic obstructive HCM, given long-term morbidity associated with implanted prosthetic valves (including late degeneration) and chronic anticoagulation.
      • Roberts WC.
      Operative treatment of hypertrophic cardiomyopathy: the case against mitral valve replacement.
      However, valve replacement can be appropriate in selected patients with primary intrinsic mitral valve pathology when standard repair techniques are unsuccessful
      • Hong J
      • Schaff HV
      • Ommen SR
      • Abel MD
      • Dearani JA
      • Nishimura RA.
      Mitral stenosis and hypertrophic cardiomyopathy: An unusual combination.
      e.g., degeneration or excessive calcification of the leaflets and/or mitral annulus producing rare mixed mitral stenosis/regurgitation, severe myxomatous disease with prolapse or segmental flail, and in some unusual patients when basal septal thickness is particularly mild.
      • Hong J
      • Schaff HV
      • Ommen SR
      • Abel MD
      • Dearani JA
      • Nishimura RA.
      Mitral stenosis and hypertrophic cardiomyopathy: An unusual combination.
      Some expert surgeons regard valve morphology encountered in HCM (e.g., anterior leaflet elongation) as an important contributor to outflow obstruction in some patients, justifying selective remodeling,
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      ,
      • Balaram SK
      • Ross RE
      • Sherrid M
      • Schwartz GS
      • Hillel Z
      • Winson G
      • Swistel DG.
      Role of mitral valve plication in the surgical management of hypertrophic cardiomyopathy.
      • Varma PK
      • Krishna N
      • Ahamed H
      • Madassery S.
      Posterior mitral leaflet plication for hypertrophic obstructive cardiomyopathy.
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      ,
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      • McIntosh CL
      • Maron BJ
      • Cannon 3rd, RO
      • Klues HG.
      Initial results of combined anterior mitral leaflet plication and ventricular septal myotomy-myectomy for relief of left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy.
      • Vriesendorp PA
      • Schinkel AFL
      • Soliman OLL
      • Kofflard MJ
      • de Jong PL
      • van Herwerden LA
      • Ten Cate FJ
      • Michels M
      Long-term benefit of myectomy and anterior mitral leaflet extension in obstructive hypertrophic cardiomyopathy.
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      particularly when associated with mild anterior septal thickness (<18 mm).
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      Other highly successful surgeons do not favor repair of mitral valves without intrinsic valve pathology.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      ,
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      Cleveland Clinic surgeons have been aggressive (with valve repair in 25% of myectomy patients), and with 4% receiving a mitral prosthesis.
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      ,
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      In contrast, Mayo Clinic surgeons uncommonly repair the mitral valve (in <4%), and reserve value replacement for intrinsic valve disease.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      ,
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      Such differences in myectomy strategy and the heterogeneity of LV outflow anatomy underscore the principle that different operative approaches can nevertheless achieve the same desired hemodynamic and clinical result, dispelling the notion that there is a single “standard” myectomy operation.
      One specific concern is when a flexible and elongated anterior mitral leaflet >30 mm has the potential for systolic septal contact and obstruction, even after an apparently adequate muscular resection widening the outflow tract (Figure 2). Strategies designed and used to restrict valvular mobility for this purpose (since 1992)
      • McIntosh CL
      • Maron BJ
      • Cannon 3rd, RO
      • Klues HG.
      Initial results of combined anterior mitral leaflet plication and ventricular septal myotomy-myectomy for relief of left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy.
      have included: a horizontal central suture plication in the A2 segment of elongated anterior leaflet (or occasionally within the posterior leaflet)
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Varma PK
      • Krishna N
      • Ahamed H
      • Madassery S.
      Posterior mitral leaflet plication for hypertrophic obstructive cardiomyopathy.
      ,
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      ,
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      • McIntosh CL
      • Maron BJ
      • Cannon 3rd, RO
      • Klues HG.
      Initial results of combined anterior mitral leaflet plication and ventricular septal myotomy-myectomy for relief of left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy.
      • Vriesendorp PA
      • Schinkel AFL
      • Soliman OLL
      • Kofflard MJ
      • de Jong PL
      • van Herwerden LA
      • Ten Cate FJ
      • Michels M
      Long-term benefit of myectomy and anterior mitral leaflet extension in obstructive hypertrophic cardiomyopathy.
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      • Swistel DG
      • Sherrid MV.
      The surgical management of obstructive hypertrophic cardiomyopathy: the RPR procedure-resection, plication, release.
      ; excision of a residual leaflet segment to shorten length
      • Swistel DG
      • Sherrid MV.
      The surgical management of obstructive hypertrophic cardiomyopathy: the RPR procedure-resection, plication, release.
      ; or anterior leaflet stiffening by insertion of an extending pericardial patch.
      • Vriesendorp PA
      • Schinkel AFL
      • Soliman OLL
      • Kofflard MJ
      • de Jong PL
      • van Herwerden LA
      • Ten Cate FJ
      • Michels M
      Long-term benefit of myectomy and anterior mitral leaflet extension in obstructive hypertrophic cardiomyopathy.
      A variety of sub-mitral intraventricular structures identifiable with echocardiography and/or CMR can contribute importantly to LV outflow obstruction and therefore are explored at operation for possible intervention: mobilization, thinning or resection of anomalous/accessory papillary muscles; excision of fibrous and muscular attachments between mitral apparatus/anterior leaflet and head of papillary muscles, LV free wall and ventricular septum; cutting fibrotic/retracted secondary chordae of anterior mitral leaflet
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      ,
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      ,
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      ,
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      ,
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Sherrid MV
      • Balaram S
      • Kim B
      • Axel L
      • Swistel DG
      The mitral valve in obstructive hypertrophic cardiomyopathy: A test in context.
      ,
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      ,
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      (Figure 2). Particularly relevant hemodynamically is congenital anomalous insertion of anterolateral papillary muscle directly into body or free edge of anterior leaflet (in absence of interpositioned chordae tendineae) the predominant mechanism of mid-ventricular muscular obstruction,
      • Klues HG
      • Roberts WC
      • Maron BJ.
      Anomalous insertion of papillary muscle directly into anterior mitral leaflets in hypertrophic cardiomyopathy: significance in producing left ventricular outflow obstruction.
      • Lenz Carvalho J
      • Schaff HV
      • Morris CS
      • Nishimura RA
      • Ommen SR
      • Maleszewski JJ
      • Dearani JA
      Anomalous papillary muscles-implications in the surgical treatment of hypertrophic obstructive cardiomyopathy.
      • Maron BJ
      • Nishimura RA
      • Danielson GK.
      Pitfalls in clinical recognition and a novel operative approach for hypertrophic cardiomyopathy with severe outflow obstruction due to anomalous papillary muscle.
      usually managed by extended myectomy (Figure 2).
      Surgical myectomy has the flexibility to effectively address variability in phenotypic expression with a wide range of septal thicknesses including at the extremes of the morphologic spectrum i.e., massive (≥ 30 mm) to mild (≤ 15 mm).
      • Rowin EJ
      • Maron BJ
      • Maron MS.
      The hypertrophic cardiomyopathy phenotype viewed through the prism of multimodality imaging: clinical and etiologic implications.
      ,
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      ,
      • Rowin EJ
      • Maron BJ
      • Romashko M
      • Wang W
      • Rastegar H
      • Link MS
      • Maron MS.
      Impact of effective management strategies on patients with the most extreme phenotypic expression of hypertrophic cardiomyopathy.
      Notably, as the demographics of HCM change with an increasing proportion of patients showing more modest septal thickness (avg 17 mm, compared to 21-22 mm previously),
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      a novel patient subset has emerged characterized by minimal anterior basal hypertrophy but with progressive refractory HF due to typical dynamic subaortic obstruction. In this subgroup, obstruction and symptoms are reversible without valve replacement by: shallow muscular resection with remodeling/repair of mitral valve and submitral structures.
      • Swistel DG
      • Sherrid MV.
      The surgical management of obstructive hypertrophic cardiomyopathy: the RPR procedure-resection, plication, release.
      Biventricular obstruction, occasionally encountered in symptomatic children is amendable to surgery. Standard surgical myectomy relieves obstruction due to SAM, while right ventricular outflow obstruction due to excessive hypertrophy can be managed by selective resection of muscle bundles and patch enlargement of the right ventricular outflow tract.
      • Quintana E
      • Johnson JN
      • Rotes AS
      • Cetta F
      • Ommen SR
      • Schaff HV
      • Dearani JA.
      Surgery for biventricular obstruction in hypertrophic cardiomyopathy in children and younger adults: technique and outcomes.
      ,
      • Maron BJ
      • McIntosh CL
      • Klues HG
      • Cannon III, RO
      • Roberts WC.
      Morphologic basis for obstruction to right ventricular outflow in hypertrophic cardiomyopathy.
      A distal “LV debulking” operation via apical ventriculotomy has been performed by a few experienced surgeons in selected highly symptomatic nonobstructive patients with apical/mid-ventricular hypertrophy and small distal LV chamber, i.e., to improve filling and stroke volume by enlarging LV cavity, albeit with little long-term data,
      • Nguyen A
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • King KS
      • Ommen SR.
      Apical myectomy for patients with hypertrophic cardiomyopathy and advanced heart failure.
      or the opportunity to resect small apical aneurysms.
      • Nguyen A
      • Schaff HV
      • Nishimura RA
      • Dearani JA
      • Ommen SR.
      Early outcomes of repair of left ventricular apical aneurysms in patients with hypertrophic cardiomyopathy.

      Arrhythmia surgery at myectomy

      In those HCM patients with a history of paroxysmal AF, some surgeons have combined myectomy with operative ablation procedures (Cox-Maze III or IV, or pulmonary vein isolation)
      • Boll G
      • Rowin EJ
      • Maron BJ
      • Wang W
      • Rastegar H
      • Maron MS.
      Efficacy of combined Cox-Maze IV and ventricular septal myectomy for treatment of atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy.
      • Meng Y
      • Zhang Y
      • Liu P
      • Zhu C
      • Lu T
      • Hu E
      • Yang Q
      • Nie C
      • Wang S.
      Clinical efficacy and safety of Cox-Maze IV procedure for atrial fibrillation in patients with hypertrophic cardiomyopathy.
      • Seco M
      • Lau J CL
      • Medi C
      • Bannon PG
      Atrial fibrillation management during septal myectomy for hypertrophic cardiomyopathy: A systemic review.
      (Figure 4). In one center, an adjunctive bi-atrial Cox-Maze IV procedure was performed with myectomy in 100 patients,
      • Boll G
      • Rowin EJ
      • Maron BJ
      • Wang W
      • Rastegar H
      • Maron MS.
      Efficacy of combined Cox-Maze IV and ventricular septal myectomy for treatment of atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy.
      resulting in effective relief of outflow obstruction and refractory HF symptoms, as well as providing freedom from AF episodes: 91%, 73%, 49% at 1, 5, and 10 years postoperatively, including 55% of patients without symptomatic AF for up to 8 years (Figure 4). Since the Cox-Maze IV is performed only in patients undergoing myectomy for relief of outflow obstruction and normalization of LV pressures, it is difficult to definitively attribute the reduction in AF episodes solely to the Maze procedure. Long-term clinical significance of relatively brief AF episodes during the first 2-3 months after myectomy, remain incompletely resolved.
      • Tang B
      • Song Y
      • Cheng S
      • Cui H
      • Ji K
      • Zhao S
      • Wang S
      In-hospital postoperative atrial fibrillation indicates a poorer clinical outcome after myectomy for obstructive hypertrophic cardiomyopathy.
      ,
      • Ommen SR
      • Thompson HL
      • Nishimura RA
      • Tajik AJ
      • Schaff HV
      • Danielson GK.
      Clinical predictors and consequences of atrial fibrillation after surgical myectomy for obstructive hypertrophic cardiomyopathy.
      Figure 4
      Figure 4Cox-Maze IV procedure for surgical treatment of atrial fibrillation. Top panels. Schematic representation depicting the location of radiofrequency energy (white line) and cryoablation (purple lines) applied during Cox-Maze IV: A. showing epicardial surface of the posterior portion of the heart; B. endocardial surface of the left atrium; C. endocardial surface of right atrium. Ao = aorta; IV = inferior vena cava; LPV = left pulmonary veins; PA = pulmonary artery; RPV = right pulmonary veins; SVC = superior vena cava. Bottom panel Kaplan-Meier survival free from symptomatic atrial fibrillation after Cox-Maze IV combined with myectomy in 62 obstructive hypertrophic cardiomyopathy patients; Reproduced with permission of authors.
      • Boll G
      • Rowin EJ
      • Maron BJ
      • Wang W
      • Rastegar H
      • Maron MS.
      Efficacy of combined Cox-Maze IV and ventricular septal myectomy for treatment of atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy.

      Clinical Results of Surgical Myectomy

      Over the last >50 years substantial data has been assembled from high volume centers governing all aspects of surgical myectomy, including clinical outcome in thousands of patients of all ages from >25 centers in many parts of the world.
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      • Wei LM
      • Thibault DP
      • Rankin JS
      • Alkhouli M
      • Roberts HG
      • Vemulapalli S
      • Yerokun B
      • Ad N
      • Schaff HV
      • Smedira NG
      • Takayama H
      • McCarthy PM
      • Thourani VH
      • Ailawadi G
      • Jacobs JP
      • Badhwar V.
      Contemporary surgical management of hypertrophic cardiomyopathy in the United States.
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      • Morrow AG
      • Reitz BA
      • Epstein SE
      • Henry WL
      • Conkle DM
      • Itscoitz SB
      • Redwood DR.
      Operative treatment in hypertrophic subaortic stenosis. Techniques and the results of pre and postoperative assessments in 83 patients.
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Schulte HD
      • Borisov K
      • Gams E
      • Gramsch-Zabel H
      • Lösse B
      • Schwartzkopff B.
      Management of symptomatic hypertrophic obstructive cardiomyopathy–long-term results after surgical therapy.
      ,
      • Liebregts M
      • Vriesendorp PA
      • Mahmoodi BK
      • Schinkel AFL
      • Michels M
      • ten Berg JM.
      A systematic review and meta-analysis of long-term outcomes after septal reduction therapy in patients with hypertrophic cardiomyopathy.
      • Iacovoni A
      • Spirito P
      • Simon C
      • Iascone M
      • Di Dedda G
      • De Filippo P
      • Pentiricci S
      • Boni L
      • Senni M
      • Gavazzi A
      • Ferrazzi P.
      A contemporary European experience with surgical septal myectomy in hypertrophic cardiomyopathy.
      • Ten Berg JM
      • Suttorp MJ
      • Knaepen PJ
      • Ernst SM
      • Vermeulen FE
      • Jaarsma W
      Hypertrophic obstructive cardiomyopathy initial results and long-term follow-up after Morrow septal myectomy.
      • Robbins RC
      • Stinson EB.
      Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy.
      • Cohn LH
      • Trehan H
      • Collins Jr, JJ
      Long-term follow-up of patients undergoing myotomy/myectomy for obstructive hypertrophic cardiomyopathy.
      • Merrill WH
      • Friesinger GC
      • Graham TP
      • Byrd 3rd, BF
      • Drinkwater Jr, DC
      • Christian KG
      • Bender Jr., HW
      Long-lasting improvement after septal myectomy for hypertrophic obstructive cardiomyopathy.
      ,
      • Ommen SR
      • Dearani J.
      Septal myectomy in context: Clinical acumen and procedural expertise.
      ,
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      ,
      • Rowin EJ
      • Maron BJ
      • Chokshi A.
      • Kannappan M
      • Arkun K
      • Wang W
      • Rastegar H
      • Maron MS.
      Clinical spectrum and management implications of left ventricular outflow obstruction with mild ventricular septal thickness in hypertrophic cardiomyopathy.
      ,
      • Rowin EJ
      • Maron BJ
      • Romashko M
      • Wang W
      • Rastegar H
      • Link MS
      • Maron MS.
      Impact of effective management strategies on patients with the most extreme phenotypic expression of hypertrophic cardiomyopathy.
      ,
      • Desai Y
      • Bhonsale A
      • Smedira NG
      • Naji P
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Predictors of long-term outcomes in symptomatic hypertrophic cardiomyopathy patients undergoing surgical relief of left ventricular outflow tract obstruction.
      • Li H
      • Deng L
      • Liu H
      • Chen S
      • Rao C
      • Tang Y
      • Wang S
      • Liu S
      • Sun H
      • Song Y.
      Influence of operator volume on early outcomes of septal myectomy for isolated hypertrophic obstructive cardiomyopathy.
      • Ball W
      • Ivanov J
      • Rakowski H
      • Wigle ED
      • Linghorne M
      • Ralph-Edwards A
      • Williams WG
      • Schwartz L
      • Guttman A
      • Woo A.
      Long-term survival in patients with resting obstructive hypertrophic cardiomyopathy: Comparison of conservative versus invasive treatment.
      • Firoozi S
      • Elliott PM
      • Sharma S
      • Murday A
      • Brecker SJ
      • Hamid MS
      • Sachdev B
      • Thaman R
      • McKenna WJ.
      Septal myotomy-myectomy and transcoronary septal alcohol ablation in hypertrophic obstructive cardiomyopathy: a comparison of clinical, haemodynamic and exercise outcomes.
      • Woo A
      • Williams WG
      • Choi R
      • Wigle ED
      • Rozenblyum E
      • Fedwick K
      • Siu S
      • Ralph-Edwards A
      • Rakowski H.
      Clinical and echocardiographic determinants of long-term survival after surgical myectomy in obstructive hypertrophic cardiomyopathy.
      • Vriesendorp PA
      • Liebregts M
      • Steggerda RC
      • Schinkel AF
      • Willems R
      • Ten Cate FJ
      • van Cleemput J
      • Ten Berg JM
      • Michels M
      Long-term outcomes after medical and invasive treatment in patients with hypertrophic cardiomyopathy.
      • Nguyen A
      • Schaff HV
      • Ommen SR
      • Gersh BJ
      • Dearani JA
      • Geske JB
      • Lahr BD
      • Nishimura RA.
      Late health status of patients undergoing myectomy for obstructive hypertrophic cardiomyopathy.
      • Wang S
      • Luo M
      • Sun H
      • Song Y
      • Yin C
      • Wang L
      • Hui R
      • Hu S.
      A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China.
      • Noven J
      • Stagmo M
      • Wierup P
      • Nozohoor S
      • Bjursten H
      • Sjogren J
      • Zindovic I
      • Ragnarsson S.
      Exercise echocardiography following septal myectomy for hypertrophic cardiomyopathy.
      • Parry DJ
      • Raskin RE
      • Poynter JA
      • Ribero IB
      • Bajona P
      • Rakowski H
      • Woo A
      • Ralph-Edwards A.
      Short and medium term outcomes of surgery for patients with hypertrophic obstructive cardiomyopathy.
      This experience extends over several clinical eras incorporating a maturing understanding of the heterogeneous disease expression and diverse LV outflow tract anatomy, and aided by major advances in cardiac imaging, expertise in surgical techniques, intraoperative myocardial preservation, and postoperative care.
      Much of contemporary myectomy experience and accumulated data come from established high volume North American and consortium centers that have been the largest and most consistent proponents of surgical management for obstructive disease over many years: Mayo Clinic (Dearani; Schaff; Danielson)
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      ,
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Meghji Z
      • Nguyen A
      • Fatima B
      • Geske JB
      • Nishimura RA
      • Ommen SR
      • Lahr BD
      • Dearani JA
      • Schaff HV.
      Survival differences in women and men after septal myectomy for obstructive hypertrophic cardiomyopathy.
      ; Cleveland Clinic (Lytle; Smedira)
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      ,
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      ,
      • Desai Y
      • Bhonsale A
      • Smedira NG
      • Naji P
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Predictors of long-term outcomes in symptomatic hypertrophic cardiomyopathy patients undergoing surgical relief of left ventricular outflow tract obstruction.
      ; New York University (Swistel; previously Roosevelt-St. Lukes Hospitals)
      • Swistel DG
      • Sherrid MV.
      The surgical management of obstructive hypertrophic cardiomyopathy: the RPR procedure-resection, plication, release.
      ; Toronto General Hospital (Williams; Ralph-Edwards)
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      ,
      • Ball W
      • Ivanov J
      • Rakowski H
      • Wigle ED
      • Linghorne M
      • Ralph-Edwards A
      • Williams WG
      • Schwartz L
      • Guttman A
      • Woo A.
      Long-term survival in patients with resting obstructive hypertrophic cardiomyopathy: Comparison of conservative versus invasive treatment.
      ,
      • Woo A
      • Williams WG
      • Choi R
      • Wigle ED
      • Rozenblyum E
      • Fedwick K
      • Siu S
      • Ralph-Edwards A
      • Rakowski H.
      Clinical and echocardiographic determinants of long-term survival after surgical myectomy in obstructive hypertrophic cardiomyopathy.
      ; Tufts Medical Center (Boston from 2003 until its closing in 2021; Rastegar)
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ; Policlinico di Monza (Monza, Italy from 1996; Ferrazzi)
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      ; Fuwai Hospital (Beijing from 2009; S. Wang)
      • Wang S
      • Luo M
      • Sun H
      • Song Y
      • Yin C
      • Wang L
      • Hui R
      • Hu S.
      A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China.
      ; Sweden (from 1998; Ragnarsson)
      • Noven J
      • Stagmo M
      • Wierup P
      • Nozohoor S
      • Bjursten H
      • Sjogren J
      • Zindovic I
      • Ragnarsson S.
      Exercise echocardiography following septal myectomy for hypertrophic cardiomyopathy.
      ; Barcelona (from 2015; Quintana)
      • Quintana E
      • Johnson JN
      • Rotes AS
      • Cetta F
      • Ommen SR
      • Schaff HV
      • Dearani JA.
      Surgery for biventricular obstruction in hypertrophic cardiomyopathy in children and younger adults: technique and outcomes.
      ; Kiev, Ukraine (from 2016; Rudenko); Bucharest, Romania (from 2015; Dorobantu) and Lahey Hospital and Medical Center, Burlington MA (Shekar).
      Data from these centers is replete with evidence of salutary short-term and long-term benefit following myectomy in adults of all ages including the elderly
      • Wong L-Y
      • Alver N
      • Dewey EN
      • Bhamidipati C
      • Lantz G
      • Tibayan FA
      • Heitner S
      • Masri A
      • Song HK.
      Septal myectomy for obstructive hypertrophic cardiomyopathy in the elderly.
      • Alashi A
      • Smedira NG
      • Popovic ZB
      • Fava A
      • Thamilarasan M
      • Kapadia SR
      • Wierup P
      • Lever HM
      • Desai MY.
      Characteristics and outcomes of elderly patients with hypertrophic cardiomyopathy.
      • Maron BJ
      • Rowin EJ
      • Maron MS
      • Braunwald E.
      Achieving extended longevity and quality of life for senior patients with hypertrophic cardiomyopathy: What is possible.
      and also children
      • Minakata K
      • Dearani JA
      • O'Leary PW
      • Danielson GK
      Septal myectomy for obstructive hypertrophic cardiomyopathy in pediatric patients: early and late results.
      • Zhu C
      • Wang S
      • Ma Y
      • Wang S
      • Zhou Z
      • Song Y
      • Yan J
      • Meng Y
      • Nie C.
      Childhood hypertrophic obstructive cardiomyopathy and its relevant surgical outcome.
      • Stone CD
      • McIntosh CL
      • Hennein HA
      • Maron BJ
      • Clark RE.
      Operative treatment of pediatric obstructive hypertrophic cardiomyopathy: a 26-year experience.
      i.e., abolition of SAM and relief of peak resting or provocable outflow obstruction and mitral regurgitation that is immediate, complete and permanent (non-recurring) with preoperative gradients reduced from ≥50 mmHg (and up to ≥ 100mmHg) to zero or negligible (<10 mmHg) post-operatively
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      • Wei LM
      • Thibault DP
      • Rankin JS
      • Alkhouli M
      • Roberts HG
      • Vemulapalli S
      • Yerokun B
      • Ad N
      • Schaff HV
      • Smedira NG
      • Takayama H
      • McCarthy PM
      • Thourani VH
      • Ailawadi G
      • Jacobs JP
      • Badhwar V.
      Contemporary surgical management of hypertrophic cardiomyopathy in the United States.
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Desai Y
      • Smedira NG
      • Bhonsale A
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Symptom assessment and exercise impairment in surgical decision making in hypertrophic obstructive cardiomyopathy: Relationship to outcomes.
      ,
      • Desai Y
      • Bhonsale A
      • Smedira NG
      • Naji P
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Predictors of long-term outcomes in symptomatic hypertrophic cardiomyopathy patients undergoing surgical relief of left ventricular outflow tract obstruction.
      ,
      • Wang S
      • Luo M
      • Sun H
      • Song Y
      • Yin C
      • Wang L
      • Hui R
      • Hu S.
      A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China.
      ,
      • Noven J
      • Stagmo M
      • Wierup P
      • Nozohoor S
      • Bjursten H
      • Sjogren J
      • Zindovic I
      • Ragnarsson S.
      Exercise echocardiography following septal myectomy for hypertrophic cardiomyopathy.
      ,
      • Cui H
      • Schaff HV
      • Nishimura RA
      • Dearani JA
      • Geske JB
      • Ommen SR.
      Latent outflow tract obstruction in hypertrophic cardiomyopathy: Clinical characteristics and outcomes of septal myectomy.
      (Figure 5). Significant residual gradients requiring reoperation are rare (about 2% in experienced centers),
      • Cho YH
      • Quintana E
      • Schaff HV
      • Nishimura RA
      • Dearani JA
      • Abel MD
      • Ommen S.
      Residual and recurrent gradients after septal myectomy for hypertrophic cardiomyopathy-mechanisms of obstruction and outcomes of reoperation.
      usually attributable to inadequate length of muscular septal excision.
      Figure 5
      Figure 5Hemodynamic improvement post-myectomy in symptomatic obstructive hypertrophic cardiomyopathy patients and followed for 10 years (N=118). Comparison of LV outflow gradients at rest: preoperative, 2 months postoperative, and postoperatively at last follow-up (8 ± 3 years). Tufts Medical Center, Boston (2003-2010) (H. Rastegar, surgeon).
      Amelioration of HF symptoms is evident with improvement by ≥1 NYHA functional class in >90% of patients with 75% becoming asymptomatic (i.e., strikingly from NYHA functional class III/IV to class I) without outcome differences evident between men and women and with continued postoperative drug treatment unnecessary
      • Maron BJ.
      Clinical course and management of hypertrophic cardiomyopathy.
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      • Wei LM
      • Thibault DP
      • Rankin JS
      • Alkhouli M
      • Roberts HG
      • Vemulapalli S
      • Yerokun B
      • Ad N
      • Schaff HV
      • Smedira NG
      • Takayama H
      • McCarthy PM
      • Thourani VH
      • Ailawadi G
      • Jacobs JP
      • Badhwar V.
      Contemporary surgical management of hypertrophic cardiomyopathy in the United States.
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      • Maron BJ
      • Maron MS
      • Wigle ED
      • Braunwald E.
      The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy: From idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy.
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      ,
      • Ten Berg JM
      • Suttorp MJ
      • Knaepen PJ
      • Ernst SM
      • Vermeulen FE
      • Jaarsma W
      Hypertrophic obstructive cardiomyopathy initial results and long-term follow-up after Morrow septal myectomy.
      • Robbins RC
      • Stinson EB.
      Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy.
      • Cohn LH
      • Trehan H
      • Collins Jr, JJ
      Long-term follow-up of patients undergoing myotomy/myectomy for obstructive hypertrophic cardiomyopathy.
      • Merrill WH
      • Friesinger GC
      • Graham TP
      • Byrd 3rd, BF
      • Drinkwater Jr, DC
      • Christian KG
      • Bender Jr., HW
      Long-lasting improvement after septal myectomy for hypertrophic obstructive cardiomyopathy.
      ,
      • Meghji Z
      • Nguyen A
      • Fatima B
      • Geske JB
      • Nishimura RA
      • Ommen SR
      • Lahr BD
      • Dearani JA
      • Schaff HV.
      Survival differences in women and men after septal myectomy for obstructive hypertrophic cardiomyopathy.
      ,
      • Cho YH
      • Quintana E
      • Schaff HV
      • Nishimura RA
      • Dearani JA
      • Abel MD
      • Ommen S.
      Residual and recurrent gradients after septal myectomy for hypertrophic cardiomyopathy-mechanisms of obstruction and outcomes of reoperation.
      ,
      • Maron MS
      • Rastegar H
      • Dolan N
      • Carpino P
      • Koethe B
      • Maron BJ
      • Rowin EJ.
      Outcomes over follow-up ≥ 10 years after surgical myectomy for symptomatic obstructive hypertrophic cardiomyopathy.
      This is judged by personal and targeted history-taking, and also supported by objective measures i.e., increased treadmill exercise duration and markers of ischemia e.g., workload coronary flow and myocardial metabolism, and oxygen consumption (peak VO2 to 3-7mL/kg/min).
      • Ommen SR
      • Nishimura RA
      • Squires RW.
      • Schaff HV
      • Danielson GK
      • Tajik AJ.
      Comparison of dual-chamber pacing versus septal myectomy for the treatment of patients with hypertrophic obstructive cardiomyopathy.
      ,
      • Diodati JG
      • Schenke WH
      • Waclawiw MA
      • McIntosh CL
      • Cannon 3rd, RO
      Predictors of exercise benefit after operative relief of left ventricular outflow obstruction by the myectomy-myectomy procedure in hypertrophic cardiomyopathy.
      There is also evidence for myectomy-related reversed remodeling of left atrium with potential for reducing left atrial size and AF episodes,
      • Nguyen A
      • Schaff HV
      • Nishimura RA
      • Dearani JA
      • Geske JB
      • Lahr BD
      • Ommen SR.
      Determinants of reverse remodeling of the left atrium after transaortic myectomy.
      as well as possible mild regression of LV hypertrophy related to relief of loading conditions.
      • Deb SJ
      • Schaff HV
      • Dearani JA
      • Nishimura RA
      • Ommen SR.
      Septal myectomy results in regression of left ventricular hypertrophy in patients with hypertrophic obstructive cardiomyopathy.
      In addition to improved quality of life, there is also evidence that surgery reduces frequency of AF and favorably impacts longevity,
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Li H
      • Deng L
      • Liu H
      • Chen S
      • Rao C
      • Tang Y
      • Wang S
      • Liu S
      • Sun H
      • Song Y.
      Influence of operator volume on early outcomes of septal myectomy for isolated hypertrophic obstructive cardiomyopathy.
      ,
      • Wang S
      • Luo M
      • Sun H
      • Song Y
      • Yin C
      • Wang L
      • Hui R
      • Hu S.
      A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China.
      ,
      • Maron MS
      • Rastegar H
      • Dolan N
      • Carpino P
      • Koethe B
      • Maron BJ
      • Rowin EJ.
      Outcomes over follow-up ≥ 10 years after surgical myectomy for symptomatic obstructive hypertrophic cardiomyopathy.
      ,
      • Ciu H
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • Lahr BD
      • Ommen SR.
      Conduction abnormalities and long-term mortality following septal myectomy in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Wells S
      • Rowin EJ
      • Boll G
      • Rastegar H
      • Wang W
      • Maron MS
      • Maron BJ.
      Clinical profile of nonresponders to surgical myectomy with obstructive hypertrophic cardiomyopathy.
      with a long-term survival benefit, indistinguishable from that expected in the general population over 1, 5 and 10 years (and unrelated to gender) (Figure 5): freedom from all-cause mortality 98%, 96% and 83%, and freedom from HCM-related mortality 99%, 98%, 95%
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ,
      • Woo A
      • Williams WG
      • Choi R
      • Wigle ED
      • Rozenblyum E
      • Fedwick K
      • Siu S
      • Ralph-Edwards A
      • Rakowski H.
      Clinical and echocardiographic determinants of long-term survival after surgical myectomy in obstructive hypertrophic cardiomyopathy.
      ; these data are similar to the limited number of long-term follow-up analyses ≥10 years after myectomy
      • Maron MS
      • Rastegar H
      • Dolan N
      • Carpino P
      • Koethe B
      • Maron BJ
      • Rowin EJ.
      Outcomes over follow-up ≥ 10 years after surgical myectomy for symptomatic obstructive hypertrophic cardiomyopathy.
      (Figure 6).
      Figure 6
      Figure 6Demographics and outcome after surgical myectomy. A. Change in annual rate of myectomy operations (blue bars) compared to alcohol septal ablation procedures (red bars) 2003-2019 inclusive, assembled from 5 major North American HCM centers: Mayo Clinic; Cleveland Clinic; Tufts; Toronto General; NYU. B. Survival free from all-cause mortality after surgical myectomy compared to age and sex-matched general US population
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      ; C. Low operative mortality for septal myectomy (red) compared to other common cardiac operations. AV = aortic valve; MV = mitral valve; TV = tricuspid valve; CABG = coronary artery bypass grafting; D. HCM-related survival free from all-cause mortality in 3 patient subgroups in a non-randomized study: Surgical myectomy (n=289); nonoperated with obstruction (n=228) and nonobstructive (n=820). Overall log-rank, p<0.001.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      Although myectomy is highly effective for relief of symptoms in the vast majority of patients, about 5% nevertheless experience persistent functional limitation, remaining in or returning to NYHA class III despite successful relief of gradient. Myectomy non-responders (either with or without systolic dysfunction) require consideration for advanced heart failure management, including cardiac resynchronization therapy in appropriate candidates with left bundle branch block, or ultimately heart transplant. Most common determinants of failure to respond to myectomy appear to be co-morbidities
      • Wells S
      • Rowin EJ
      • Boll G
      • Rastegar H
      • Wang W
      • Maron MS
      • Maron BJ.
      Clinical profile of nonresponders to surgical myectomy with obstructive hypertrophic cardiomyopathy.
      ,
      • Sun D
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • Lahr BD
      • Ommen SR.
      Impact of body mass index on outcome of septal myectomy for obstructive hypertrophic cardiomyopathy.
      (prominently obesity),
      • Sun D
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • Lahr BD
      • Ommen SR.
      Impact of body mass index on outcome of septal myectomy for obstructive hypertrophic cardiomyopathy.
      massive LV hypertrophy, or in some patients pulmonary hypertension. There is no definitive evidence, however, that myectomy per se causes or predisposes to development of the end-stage.
      • Rowin EJ
      • Maron BJ
      • Carrick RT
      • Patel PP
      • Koethe B
      • Wells S
      • Maron MS.
      Outcomes in patients with hypertrophic cardiomyopathy and left ventricular systolic dysfunction.
      The vast majority of patients incur left bundle branch as a result of the operative resection which does not influence later clinical course.
      • Ciu H
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • Lahr BD
      • Ommen SR.
      Conduction abnormalities and long-term mortality following septal myectomy in patients with obstructive hypertrophic cardiomyopathy.
      Surgeons performing myectomy after an unsuccessful ASA report less consistent operative results and a higher rate of complete heart block,
      • Yang Q
      • Zhu C
      • Cui H
      • Tang B
      • Wang S
      • Yu Q
      • Zhao S
      • Song Y
      • Wang S.
      Surgical septal myectomy outcome for obstructive hypertrophic cardiomyopathy after alcohol septal ablation.
      • Quintana E
      • Sabate-Rotes A
      • Maleszewski JJ.
      Septal myectomy after failed alcohol ablation: Does previous percutaneous intervention compromise outcomes of myectomy.
      • Zhu C
      • Tang B
      • Cui H
      • Wang S
      • Xiao M
      • Chen Z
      • Meng Y
      • Zhao S
      • Song Y
      • Yu Q
      • Wang S
      Predictors of long-term outcome after septal myectomy in symptomatic hypertrophic obstructive cardiomyopathy patients with previous alcohol septal ablation and residual obstruction.
      underscoring that myectomy is the preferred initial procedure to avoid myocardial scarring, heart block and other potential adverse consequences of ASA.
      Sudden death events remote from myectomy are uncommon
      • Maron BJ
      • Rowin EJ
      • Maron MS.
      Evolution of risk stratification and sudden death prevention in hypertrophic cardiomyopathy: Twenty years with the implantable cardioverter-defibrillator.
      ,
      • McLeod CJ
      • Ommen SR
      • Ackerman MJ
      • Weivoda PL
      • Shen WK
      • Dearani JA
      • Schaff HV
      • Tajik AJ
      • Gersh BJ.
      Surgical septal myectomy decreases the risk for appropriate implantable cardioverter defibrillator discharge in obstructive hypertrophic cardiomyopathy.
      and there is some evidence that surgery offers a measure of protection from arrhythmic events, presumably by normalizing LV pressures. However, in one study, >10% of patients with successful myectomy implanted with primary prevention ICDs (based on AHA/ACC risk markers)
      • Ommen SR
      • Mital S
      • Burke MA
      • Day SM
      • Deswal A
      • Elliott P
      • Evanovich LL
      • Hung J
      • Joglar JA
      • Kantor P
      • Kimmelstiel C
      • Kittleson M
      • Link MS
      • Maron MS
      • Martinez MW
      • Miyake CY
      • Schaff HV
      • Semsarian C
      • Sorajja P.
      2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy.
      experienced appropriate device therapy postoperatively (4%/year).
      • Maron BJ
      • Rowin EJ
      • Maron MS.
      Evolution of risk stratification and sudden death prevention in hypertrophic cardiomyopathy: Twenty years with the implantable cardioverter-defibrillator.
      These observations underscore the principle that in HCM sudden death risk can represent an adverse disease pathway separate from progressive HF, and emphasizing the prudence of risk stratification even in a surgical population.
      • Maron MS
      • Rastegar H
      • Dolan N
      • Carpino P
      • Koethe B
      • Maron BJ
      • Rowin EJ.
      Outcomes over follow-up ≥ 10 years after surgical myectomy for symptomatic obstructive hypertrophic cardiomyopathy.
      ,
      • Maron BJ
      • Rowin EJ
      • Maron MS.
      Evolution of risk stratification and sudden death prevention in hypertrophic cardiomyopathy: Twenty years with the implantable cardioverter-defibrillator.
      Pulmonary hypertension is not uncommon in obstructive patients referred for surgical myectomy (50% of patients in one study),
      • Covella M
      • Rowin EJ
      • Hill NS
      • Preston IR
      • Milan A
      • Opotowsky AR
      • Maron BJ
      • Maron MS
      • Maron BA.
      Mechanism of progressive heart failure and significance of pulmonary hypertension in obstructive hypertrophic cardiomyopathy.
      and can contribute to symptoms. In one report, pulmonary hypertension was associated with all-cause mortality although myectomy appeared to reduce the adverse effect of elevated pulmonary arterial pressures.
      • Ong KC
      • Geske JB
      • Hebl VB
      • Nishimura RA
      • Schaff HV
      • Ackerman MJ
      • Klarich KW
      • Siontis KC
      • Coutinho T
      • Dearani JA
      • Ommen SR
      • Gersh BJ.
      Pulmonary hypertension is associated with worse survival in hypertrophic cardiomyopathy.

      Experience of Consortium Centers (Tables 1 and 2)

      To characterize the major cardiac surgeons currently practicing myectomy internationally, survey data were systematically collected and assembled from a cadre of 10 multi-disciplinary HCM centers in 6 countries over the last 15 years. Together, this group has performed almost 11,000 largely isolated myectomy operations (average, 800/year), with some programs now reporting >200 procedures annually (Tables 1 and 2). Average age at surgery was 54 years, reflecting the cumulative effect of the LV pressure load over time leading to the myectomy decision; men were predominant (55:45). Pacemaker implantation for heart block was 4%,
      • Ciu H
      • Schaff HV
      • Nishimura RA
      • Geske JB
      • Dearani JA
      • Lahr BD
      • Ommen SR.
      Conduction abnormalities and long-term mortality following septal myectomy in patients with obstructive hypertrophic cardiomyopathy.
      iatrogenic ventricular septal defect was 0.3% and mitral valve replacement was 1.8%. Unsuccessful ASA preceded myectomy in 1-2% with generally less satisfactory surgical results including increased arrhythmic and operative risk and likelihood of pacemaker implantation. Notably, much of the experience with myectomy in lower volume centers remains largely undocumented.
      Table 1Tabulated data for surgical myectomy at 10 consortium HCM centers
      VariableTotal number myectomyAge at myectomy (years)MaleVSDPPM
      can include patients with preoperative conduction disease.
      MVR as sole operative strategyOperative (30-day) mortality, nOperative mortality
      Clevland Clinic285156 ± 1453%0.1%4.1%153
      predominantly in patients with mild anterior septal thickness (<18 mm) and LV outflow tract obstruction, usually after mitral valve repair unsuccessful in satisfactorily relieving outflow gradient with or without papillary muscle reorientation.
      210.7%
      Mayo Clinic278257 ± 1654%0.1%6.6%0140.5%
      Fuwai222047 ± 1560%0.5%0.9%0110.5%
      Tufts82554 ± 1554%0.7%6.0%050.6%
      Toronto74055 ± 1461%0.3%6.6%1470.9%
      Monza/Bergamo66553 ± 1655%0.2%3.2%030.4%
      NYU51557 ± 1351%0.6%2.7%340.8%
      UCLA17141 ± 2950%08.8%2410.6%
      Barcelona14461 ± 1445%1%4.8%810.6%
      Sydney6052 ± 1846%5%15.0%000
      Total10,9735455%0.3%4%202 (1.8%)670.6%
      Abbreviations: MVR = mitral valve replacement; NYU: New York University; PPM= permanent pacemaker; UCLA: University of California Los Angeles; VSD: (iatrogenic) ventricular septal defect; Y: years
      low asterisk predominantly in patients with mild anterior septal thickness (<18 mm) and LV outflow tract obstruction, usually after mitral valve repair unsuccessful in satisfactorily relieving outflow gradient with or without papillary muscle reorientation.
      can include patients with preoperative conduction disease.
      Table 2NYHA functional class and LV outflow gradient before and after surgical myectomy in obstructive HCM patients reported in the literature from major centers, 1972-2017.
      CenterYearNYHA III/IV: preoperativeNYHA III/IV: postoperativePeak LVOT gradient: preop (mmHg)Peak LVOT gradient: postop (mmHg)
      Mayo Clinic
      • Kotkar KD
      • Said SM
      • Dearani JA
      • Schaff HV.
      Hypertrophic obstructive cardiomyopathy: The Mayo Clinic experience.
      • Ommen SR
      • Maron BJ
      • Olivotto I
      • Maron MS
      • Cecchi F
      • Betocchi S
      • Gersh BJ
      • Ackerman MJ
      • McCully RB
      • Dearani JA
      • Schaff HV
      • Danielson GK
      • Tajik AJ
      • Nishimura RA.
      Long-term effects of surgical myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.
      1983-200189%6%67 ± 413 ± 8
      Tufts
      • Rastegar H
      • Boll G
      • Rowin EJ
      • Dolan N
      • Carroll C
      • Udelson JE
      • Wang W
      • Carpino P
      • Maron BJ
      • Maron MS
      • Chen FY.
      Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience.
      2003-201698%6%56 ± 421.2 ± 6.8
      Cleveland Clinic
      • Hodges K
      • Rivas CG
      • Aguilera J
      • Borden R
      • Alashi A
      • Blackstone E
      • Desai M
      • Smedira N.
      Surgical management of left ventricular outflow tract obstruction in a specialized hypertrophic obstructive cardiomyopathy center.
      • Desai Y
      • Bhonsale A
      • Smedira NG
      • Naji P
      • Thamilarasan M
      • Lytle BW
      • Lever HM.
      Predictors of long-term outcomes in symptomatic hypertrophic cardiomyopathy patients undergoing surgical relief of left ventricular outflow tract obstruction.
      1997-200761%5%61 ± 411 ± 7
      Netherlands
      RC Steggerda et al., JACC Cardiovasc Interventions 2014; 7: 1227-34
      1981-201076%18%5010
      Toronto
      • Vanderlaan RD
      • Woo A
      • Ralph-Edwards A.
      Isolated septal myectomy for hypertrophic obstrutive cardiomyopathy: An update on the Toronto General Hospital experience.
      • Woo A
      • Williams WG
      • Choi R
      • Wigle ED
      • Rozenblyum E
      • Fedwick K
      • Siu S
      • Ralph-Edwards A
      • Rakowski H.
      Clinical and echocardiographic determinants of long-term survival after surgical myectomy in obstructive hypertrophic cardiomyopathy.
      2001-201179%16%64 ± 365 ± 5
      Stanford
      • Robbins RC
      • Stinson EB.
      Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy.
      1972-199472%5%67 ± 398 ± 14
      NYU
      • Swistel DG
      • Sherrid MV.
      The surgical management of obstructive hypertrophic cardiomyopathy: the RPR procedure-resection, plication, release.
      1985-201196%2%65 ± 423 ± 9
      Bergamo
      • Iacovoni A
      • Spirito P
      • Simon C
      • Iascone M
      • Di Dedda G
      • De Filippo P
      • Pentiricci S
      • Boni L
      • Senni M
      • Gavazzi A
      • Ferrazzi P.
      A contemporary European experience with surgical septal myectomy in hypertrophic cardiomyopathy.
      1996-201078%3%95 ± 3612 ± 6
      Monza
      • Ferrazzi P
      • Spirito P
      • Iacovoni A
      • Calabrese A
      • Migliorati K
      • Simon C
      • Pentiricci S
      • Poggio D
      • Grillo M
      • Amigoni P
      • Iascone M
      • Mortara A
      • Maron BJ
      • Senni M
      • Bruzzi P.
      Transaortic chordal cutting: mitral valve repair for obstructive hypertrophic cardiomyopathy with mild septal hypertrophy.
      2011-201382%082 ± 439 ± 5
      Fuwai
      • Wang S
      • Luo M
      • Sun H
      • Song Y
      • Yin C
      • Wang L
      • Hui R
      • Hu S.
      A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China.
      2009-201186%092 ± 2514 ± 13
      Sweden
      • Noven J
      • Stagmo M
      • Wierup P
      • Nozohoor S
      • Bjursten H
      • Sjogren J
      • Zindovic I
      • Ragnarsson S.
      Exercise echocardiography following septal myectomy for hypertrophic cardiomyopathy.
      1998-201745%658015
      Abbreviations: NYHA= New York Heart Association functional class; NYU: New York University; LVOT: left ventricular outflow tract
      RC Steggerda et al., JACC Cardiovasc Interventions 2014; 7: 1227-34
      Accessing data from 5 selected high volume North American HCM centers, surgical myectomy procedures performed over the last 15 years have progressively increased by almost 300% in a steep linear fashion (Figure 6). This trend is in sharp contrast to the volume of ASA procedures at the same institutions which have remained essentially unchanged over the same 15 year period; the ratio of myectomy to ASA is 9:1.
      Increase in referrals for myectomy in the U.S. probably reflects enhanced clinical awareness regarding the consequences of outflow obstruction, and growing acceptance of myectomy, paradoxically stimulated by introduction and interest in ASA. Notably, the number of myectomy (and ASA) procedures currently performed probably under-represents the potential patient pool, given the proportion of patients who would be expected to have obstruction to LV outflow (i.e., 70%).
      • Maron MS
      • Olivotto I
      • Zenovich AG
      • Link MS
      • Pandian NG
      • Kuvin JT
      • Nistri S
      • Cecchi F
      • Udelson JE
      • Maron BJ.
      Hypertrophic cardiomyopathy is predominantly a disease of left ventricular outflow tract obstruction.
      Operative (30 day) mortality rate is low (0.6%), consistent with prior reports
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      and not significantly different with respect to gender or age (including children or the elderly) and remarkably similar among major high volume centers.
      • Maron BJ
      • Dearani JA
      • Ommen SR
      • Maron MS
      • Schaff HV
      • Nishimura RA
      • Ralph-Edwards A
      • Rakowski H
      • Sherrid MV
      • Swistel DG
      • Balaram S
      • Rastegar H
      • Rowin EJ
      • Smedira NG
      • Lytle BW
      • Desai MY
      • Lever HM.
      Low operative mortality achieved with surgical septal myectomy: Role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction.
      Of note, myectomy-related operative mortality is now >10-fold less than that experienced 30 years ago, 5-fold less than for other open-heart procedures, including coronary artery bypass grafting (2.5%) and/or valve replacement (i.e., 3%)
      • O'Brien SM
      • Feng L
      • He X
      • Xian Y
      • Jacobs JP
      • Badhwar V
      • Kurlansky PA
      • Furnary AP
      • Cleveland Jr, JC
      • Lobdell KW
      • Vassileva C
      • Wyler von Ballmoos MC
      • Thourani VH
      • Rankin JS
      • Edgerton JR
      • D'Agostino RS
      • Desai ND
      • Edwards FH
      • Shahian DM
      The Society of Thoracic Surgeons 2018 adult cardiac surgery risk models: Part 2 – Statistical methods and results.
      and arguably one of the safest current open heart procedures (Figure 6).
      In addition, when performed in high volume dedicated HCM center environments, in-hospital operative mortality for myectomy (0.5%) is 12-fold less in experienced centers compared to surgery performed largely for convenience in community hospitals by surgeons much less familiar with myectomy (i.e., 6% and up to 15%).