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Cardiopulmonary Limited Ultrasound Examination for “Quick-Look” Bedside Application

      Although taking a “quick look” at the heart using a small ultrasound device is now feasible, a formal ultrasound imaging protocol to augment the bedside physical examination has not been developed. Therefore, we sought to evaluate the diagnostic accuracy and prognostic value of a cardiopulmonary limited ultrasound examination (CLUE) using 4 simplified diagnostic criteria that would screen for left ventricular dysfunction (LV), left atrial (LA) enlargement, inferior vena cava plethora (IVC+), and ultrasound lung comet-tail artifacts (ULC+) in patients referred for echocardiography. The CLUE was tested by interpretation of only the parasternal LV long-axis, subcostal IVC, and 2 lung apical views in each of 1,016 consecutive echocardiograms performed with apical lung imaging. For inpatients, univariate and multivariate logistic regression analyses were performed to assess the relations between mortality, CLUE findings, age, and gender. In this echocardiographic referral series, 78% (n = 792) were inpatient and 22% (n = 224) were outpatient. The CLUE criteria demonstrated a sensitivity, specificity, and accuracy for a LV ejection fraction of ≤40% of 69%, 91%, and 89% and for LA enlargement of 75%, 72%, and 73%, respectively. CLUE findings of LV dysfunction, LA enlargement, IVC+, and ULC+ were seen in 16%, 53%, 34%, and 28% of inpatients. The best multivariate logistic model contained 3 predictors of in-hospital mortality: ULC+, IVC+ and male gender, with adjusted odds ratios (95% confidence intervals) of 3.5 (1.4 to 8.8), 5.8 (2.1 to 16.4), and 2.3 (0.9 to 5.8), respectively. In conclusion, a CLUE consisting of 4 quick-look “signs” has reasonable diagnostic accuracy for bedside use and contains prognostic information.
      A cardiopulmonary limited ultrasound examination (CLUE) could provide the foundation for an “ultrasound-assisted” physical examination
      • Kimura B.J.
      • DeMaria A.N.
      Hand-carried ultrasound: evolution, not revolution.
      • Popp R.L.
      The physical examination of the future: echocardiography as part of the assessment.
      • Roelandt J.R.T.C.
      A personal ultrasound imager (ultrasound stethoscope): a revolution in the physical cardiac diagnosis!.
      and can be derived using data that already exist within the fields of echocardiography and chest ultrasonography. However, the distillation of these 2 disciplines into 1 simplified examination for general use should be guided by evidence and practical considerations. Systolic left ventricular (LV) dysfunction, left atrial (LA) enlargement, pulmonary edema, and elevated central venous pressures have bedside prognostic and diagnostic importance in patients with suspected cardiopulmonary disease and are reasonable evidence-based targets to include in a modern-day ultrasound cardiac physical examination, just as they have been targets of physical examination for centuries. Moreover, these findings can be screened by subjective interpretation of only 4 ultrasound views: the cardiac parasternal long-axis view of the left ventricle, 2 longitudinal anterior views of the lung apices, and a subcostal longitudinal view of the inferior vena cava (IVC). Therefore, we sought to test the diagnostic accuracy and prognostic importance of a simple CLUE on patients already referred for echocardiography.

      Methods

      Data were obtained retrospectively from consecutive comprehensive transthoracic echocardiograms performed using conventional, fully featured echocardiographs (Philips iE33, Philips Healthcare, Andover, Massachusetts) and low-frequency 3-MHz phased-array cardiac transducers, during a 3-month period in a 300-bed tertiary medical center. Repeated, follow-up, or limited examinations were not included. The echocardiographic evaluation included parasternal, apical, and subcostal imaging using 2-dimensional, color, and spectral Doppler and M-mode according to published guidelines
      • Armstrong W.F.
      Feigenbaum's Echocardiography.
      and 2 views of the lung apices to evaluate for lung comet tail artifacts as a part of the institution's routine standard echocardiographic imaging protocol. Each echocardiogram was acquired by 1 of 7 randomly available experienced registered cardiac sonographers, and interpreted by 1 of 12 board-certified cardiologists rotating as reader-of-the-day. The Scripps Institutional Review Board for Scripps Mercy Hospital (San Diego, California) approved the study.
      CLUE was defined a priori to consist of 4 video-looped views (Figure 1) within the comprehensive echocardiographic study. The 4 specific CLUE views were interpreted by 1 cardiologist-echocardiographer who was unaware of the results of the comprehensive study and based his interpretation using the predetermined subjective “quick-look” criteria as follows. The first CLUE view was the standard echocardiographic parasternal LV long-axis view for the evaluation of LV systolic dysfunction and LA enlargement. LV dysfunction was defined as present by quick-look subjective estimation if the anterior leaflet of the mitral valve during diastole did not appear to encroach on the LV outflow tract and approach the septum to within 1 cm.
      • Massie B.M.
      • Schiller N.B.
      • Ratshin R.A.
      • Parmley W.W.
      Mitral-septal separation: new echocardiographic index of left ventricular function.
      • Silverstein J.R.
      • Laffely N.H.
      • Rifkin R.D.
      Quantitative estimation of left ventricular ejection fraction from mitral valve E point to septal separation and comparison to magnetic resonance imaging.
      • Kimura B.J.
      • Amundson S.A.
      • Willis C.L.
      • Gilpin E.A.
      • DeMaria A.N.
      Usefulness of a hand-held ultrasound device for bedside examination of left ventricular function.
      LA enlargement was defined as present if the LA anteroposterior diameter appeared larger than the anteroposterior diameter of the overlying ascending aorta at the sinuses of Valsalva, throughout the cardiac cycle.
      • Kimura B.J.
      • Kedar E.
      • Weiss D.E.
      • Wahlstrom C.L.
      • Agan D.L.
      A hand-carried ultrasound sign of cardiac disease: the left atrium-to-aorta diastolic ratio.
      The second CLUE view was the standard echocardiographic subcostal longitudinal view of the proximal intrahepatic inferior vena cava as it entered the right atrium. Elevated central venous pressures were considered present (IVC+) if the IVC subjectively appeared plethoric and dilated, as noted by parallel vessel walls and a luminal diameter reduction of <50% with respiratory motion of the diaphragm, without forced “sniffing”.
      • Kircher B.J.
      • Himelman R.B.
      • Schiller N.B.
      Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava.
      • Brennan J.M.
      • Blair J.E.
      • Goonewardena S.
      • Ronan A.
      • Shah D.
      • Vasaiwala S.
      • Kirkpatrick J.N.
      • Spencer K.T.
      Reappraisal of the use of inferior vena cava for estimating right atrial pressure.
      The final 2 CLUE views were bilateral longitudinal views taken with the transducer probe in the midinfraclavicular region in the second intercostal space of each lung apex demonstrating the pleural line, typically framed by both rib shadows. An ultrasound lung comet tail artifact was considered present (ULC+) if, in this view, ≥3 vertical hyperechoic lines were seen to emanate from the pleural line in the near field and reach the far field, moving with respiration.
      • Lichtenstein D.
      • Meziere G.
      • Biderman P.
      • Gepner A.
      • Barre O.
      The comet-tail artifact: an ultrasound sign of alveolar-interstitial syndrome.
      The data were recorded as whether ULCs were demonstrated in either lung, noted as “any ULC+,” or both lungs, noted as “bilateral ULC+.”
      Figure thumbnail gr1
      Figure 1CLUE with normal findings (Upper) and abnormal findings (Lower) for each view (see text for “quick-look” diagnostic criteria). Probe positions seen within insets (black bars). Parasternal long-axis view (Left) shown in mid-diastole and demonstrates LV systolic dysfunction and LA enlargement. Longitudinal subcostal view (Center) shown in end-inspiration and demonstrates IVC+. Lung apical view (Right) shown at end-expiration and demonstrates 3 normal horizontal reverberation artifacts compared to ULC+ examination with ≥3 vertical linear artifacts.
      The accuracy of the CLUE findings of LV dysfunction or LA enlargement were assessed using the results reported from the corresponding reference standard echocardiogram. As is common in standard “real-world” practice, multiple techniques provided estimates of the LV ejection fraction and LA size to the reader during the comprehensive study, each with a perceived accuracy dependent on the known limitations of the technique, patient body habitus, and the specific quality of the study data. For the ejection fraction, the techniques included Teicholz-based M-mode,
      • Teicholz L.E.
      • Kreulen T.
      • Herman M.V.
      • Gorlin R.
      Problems in echocardiographic volume determinations: echocardiographic-angiographic correlations in the presence or absence of asynergy.
      the Simpson's biplane method of disks (modified Simpson's rule),
      • Lang R.M.
      • Bierig M.
      • Devereux R.B.
      • Flachskampf F.A.
      • Foster E.
      • Pellikka P.A.
      • Picard M.H.
      • Roman M.J.
      • Seward J.
      • Shanewise J.
      • Solomon S.
      • Spencer K.T.
      • St John Sutton M.
      • Stewart W.
      Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a Branch of the European Society of Cardiology.
      and subjective estimates by the sonographer. For LA size, the standard anteroposterior LA diameter was obtained from M-mode and the LA volume index was routinely measured using the area-length method,
      • Lang R.M.
      • Bierig M.
      • Devereux R.B.
      • Flachskampf F.A.
      • Foster E.
      • Pellikka P.A.
      • Picard M.H.
      • Roman M.J.
      • Seward J.
      • Shanewise J.
      • Solomon S.
      • Spencer K.T.
      • St John Sutton M.
      • Stewart W.
      Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a Branch of the European Society of Cardiology.
      with mild LA enlargement considered present when >4.0 cm and >28 ml/m2, respectively. The final interpretation of the LV ejection fraction and LA size was according to the discretion of the reader-of-the-day after the synthesis and review of all available data and subjective determinations and was included in the echocardiographic final report. Because CLUE acquisition and interpretation of the IVC+ and ULC+ findings used the same method as in the comprehensive echocardiogram, no separate reference standard echocardiographic assessment existed for validation of these parameters. The final standard echocardiographic reports were scrutinized for the presence of LV systolic dysfunction defined as a LV ejection fraction of ≤40% or any mention of greater than moderate systolic dysfunction. The presence of LA enlargement was considered present if any mention of its enlargement was found in the report or, in the absence of such, if the LA anteroposterior diameter using M-mode was >4.5 cm.
      A comprehensive echocardiogram was considered “technically inadequate” if technically poor, limited, or difficult images were mentioned, and no interpretation of the LV ejection fraction or LA size was provided in the final report. Technically inadequate studies were excluded from the diagnostic analysis. CLUE images were thought to be technically inadequate if the data acquired were of such poor target resolution that they did not permit subjective evaluation by the predefined criteria or if the data were nonexistent owing to an inability to access the proper window because of bandages, wounds, or patient discomfort.
      Inpatient echocardiographic mortality was defined as the ratio of the number of deaths of inpatients who had undergone echocardiography during their admission divided by the total number of inpatients undergoing echocardiography during the 3-month study period. Deaths that occurred within the emergency department were considered inpatient deaths. Outpatients were not included in the mortality analysis, because their outcomes were not known. The total inpatient mortality, a value calculated for comparison to the inpatient echocardiographic mortality, was estimated as the number of total deaths divided by the total number of unique patient admissions during the study period.
      Patient age is expressed as the mean ± SD and categorical data as percentages. Statistical analysis was performed by a statistician (T.W.) using R software (R Foundation for Statistical Computing, Vienna, Austria). The inpatient and outpatient groups were compared using chi-square tests and t tests, depending on the data. The diagnostic sensitivity, specificity, accuracy, and positive and negative predictive values were derived for the CLUE diagnostic criteria for LV systolic dysfunction and LA enlargement by comparing the interpretation of technically adequate CLUE views with the results of LV ejection and LA enlargement from the reference standard echocardiogram.
      For the mortality outcome analysis, only inpatient CLUE studies in which all 4 views were technically adequate were considered. The relation between inpatient mortality and CLUE variables of LV systolic dysfunction, LA enlargement, ULC+, and IVC+ and standard echocardiographic variables of LV ejection fraction of ≤40% and LA enlargement, and patient gender was examined using Pearson chi-square tests, and the relation with age examined using univariate logistic regression analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were computed for each variable of interest. Multivariate logistic regression analysis examined the joint effect of these predictors on mortality. The best-fit multivariate model using CLUE findings, patient age, and gender variables was selected using the Akaike Information Criterion.
      • Akaike H.
      A new look at the statistical model identification.
      Significance was assessed at α = 0.05.

      Results

      Data consisted of 1,016 echocardiograms, of which 224 (22%) were outpatient and 792 (78%) were inpatient. The overall patient age was 65.6 ± 16.8 years (range 16.0 to 97.0), and 51% were male. Outpatients, compared to inpatients, were significantly younger (61.7 ± 17.0 years, range 18.0 to 94.0, vs 66.5 ± 16.6 years, range 16.0 to 97.0, p = 0.0002), and 48% were male compared to 52% of the inpatients (p = NS).
      Regarding only the assessment of LV ejection fraction and LA enlargement, comprehensive echocardiography showed technical inadequacy in 2 (0.2%) and 28 (2.8%) final reports, respectively, and these were excluded from the diagnostic accuracy analysis. Because the CLUE findings were limited to an assessment from a single view, as expected, the rates at which each CLUE finding could not be delineated owing to technical limitations were greater: LV systolic dysfunction, 5.4%; LA enlargement, 4.3%; IVC+, 17%; and ULC+, 5.7%. Overall, the LV ejection fraction was 62.3 ± 13.8% (inpatients 61.6 ± 9.9% and outpatients 64.9 ± 14.7%, p = 0.0001), and the LA size was 3.9 ± 0.8 cm (inpatients 4.0 ± 0.9 cm and outpatients 3.8 ± 0.7 cm, p <0.0001). As expected, all CLUE findings were significantly more prevalent in the inpatients than in the outpatients (Table 1).
      Table 1Prevalence and mortality analysis (univariate)
      VariableOutpatientsInpatientsORs for Inpatient Mortality (95% CI)
      Age >65 years103/224 (46%)447/792 (56%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      0.68 (0.35–1.33)
      Men108/224 (48%)415/792 (52%)2.5
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
       (1.2–5.2)
      CLUE results
       LV dysfunction16/219 (7%)117/742 (16%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      1.65 (0.69–3.95)
       LA enlargement85/221 (38%)398/751 (53%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      0.77 (0.37–1.61)
       IVC+27/199 (14%)222/648 (34%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      6.36
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
       (2.66–15.21)
       ULC+ (any)19/215 (9%)209/743 (28%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      4.6
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
       (2.21–9.56)
       ULC+ (bilateral)9/215 (4%)115/743 (16)%
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      5.3
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
       (2.58–11.01)
      Echocardiographic findings
       LV ejection fraction ≤40%10/224 (5%)89/790 (11%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      2.47
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
       (1.08–5.62)
       LA enlargement79/218 (36%)396/770 (51%)
      p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      1.0 (0.5–2.0)
      Total represents number of adequate studies for each entity; for correlation with inpatient mortality, only CLUE studies with all 4 components adequate were used (n = 576).
      low asterisk p ≤0.05 (outpatient vs. inpatient; univariate ORs).
      For the finding of LV ejection fraction of ≤40%, the sensitivity, specificity, accuracy, and positive and negative predictive value for CLUE was 69% (95% CI 58% to 79%), 91% (95% CI 89% to 93%), 89% (95% CI 86% to 91%), 51% (95% CI 41% to 60%), and 96% (95% CI 94% to 97%), respectively. For LA enlargement, the sensitivity, specificity, accuracy, and positive and negative predictive value of CLUE was 75% (95% CI 70% to 79%), 72% (95% CI 66% to 76%), 73% (95% CI 70% to 77%), 75% (95% CI 70% to 79%), and 72% (95% CI 67% to 77%), respectively.
      The overall inpatient mortality rate was 1.8% (101 of 5,665). The inpatient echocardiographic mortality rate was 4.9% (39 of 792) and significantly greater (p <0.0001), reflecting the greater acute mortality of inpatients with known or suspected cardiovascular disease referred for echocardiography. Of the 39 inpatients who died, 28 men versus 11 women (p = 0.010) died, with a male decedent mean age of 66 ± 14 years versus 60 ± 16 years for women (p = NS). CLUE studies that were technically adequate in all 4 views were obtained for 576 inpatients (73%). An analysis of the inpatient CLUE studies with any 1 technically inadequate view (n = 216) versus technically adequate 4-view CLUE studies (n = 576), showed a mortality of 7.9% versus 3.8% (OR 2.2; p = 0.03), likely representing the more frequent instrumentation and difficult imaging of the critically ill patient. The presence of all 4 CLUE signs was seen in 24 inpatients (4.2%) and was associated with a high mortality rate of 21%. The absence of all 4 CLUE signs was seen in 176 inpatients (31%) and was associated with a minimal mortality rate of 1%. In considering the presence of any ULC+ (n = 209) versus bilateral ULC+ (n = 115), the OR for inpatient mortality was 4.6 (95% CI 2.21 to 9.60) versus 5.3 (95% CI 2.6 to 11.0), respectively. The univariate ORs (with 95% CIs; Table 1) and the best multivariate logistic model (Table 2) were significant for the presence of IVC+, any ULC+, and male gender.
      Table 2Best fit multivariate regression model
      VariableCoefficientOR95% CIp Value
      Male gender0.8202.2700.889–5.7990.08656
      IVC+1.7655.8422.079–16.4140.00081
      ULC+ (any)1.2573.5151.409–8.7710.00705

      Discussion

      The present observational study investigated a cardiopulmonary-limited ultrasound examination designed for quick-look application and found diagnostic accuracy for LV dysfunction and LA enlargement and prognostic value for the 2 ultrasound signs of apical lung comet tail artifacts and plethora of the IVC. The examination required only 4 images, used simplified subjective interpretation, and could be obtained in acutely ill patients.
      The development of an ultrasound-assisted physical examination with a pocket-size or hand-carried device has the potential to augment the detection of clinically important entities,
      • Kimura B.J.
      • Gilcrease G.
      • Showalter B.K.
      • Phan J.N.
      • Wolfson T.
      Diagnostic performance of a pocket-sized ultrasound device for quick-look cardiac imaging.
      particularly those not well detected by expert practice of physical techniques.
      • McGee S.
      Evidence-Based Physical Diagnosis.
      • Kobal S.L.
      • Atar S.
      • Siegel R.J.
      Hand-carried ultrasound improves the bedside cardiovascular examination.
      Up to this point, however, it has been difficult to project the efficacy of ultrasound-assisted bedside examination owing to the heterogeneity in imaging protocols, each of which require varying degrees of expertise in echocardiography. The present investigation demonstrated a conceptual framework for construction of a simplified examination prototype, in which evidence-basis is used from conventional ultrasound fields to derive an imaging protocol limited to specific findings fundamentally important to the initial diagnosis.
      Systolic LV dysfunction to an ejection fraction of ≤40% is an important clinical entity for detection at the bedside. In addition to the possible initiation of evidence-based, antiadrenergic therapies
      The SOLVD Investigators
      Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions.
      • Packer M.
      • Bristow M.R.
      • Cohn J.N.
      • Colluci W.S.
      • Fowler M.B.
      • Gilbert E.M.
      • Shusterman N.H.
      U.S. Carvedilol Heart Failure Study Group
      The effect of carvedilol on morbidity and mortality inpatients with chronic heart failure.
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      The effect of spironolactone on morbidity and mortality in patients with severe heart failure Randomized Aldactone Evaluation Study Investigators.
      to improve the prognosis, the discovery of LV systolic dysfunction can cause immediate changes in the management plan in unexplained hypotension, dyspnea, or in newly diagnosed arrhythmias. Using a subjective criterion, the present study found that a single parasternal long-axis view has an accuracy of 89% for the detection of LV ejection fraction of ≤40%. LA enlargement detected by echocardiography is a marker for the presence of significant cardiac pathologic features
      • Kimura B.J.
      • Kedar E.
      • Weiss D.E.
      • Wahlstrom C.L.
      • Agan D.L.
      A hand-carried ultrasound sign of cardiac disease: the left atrium-to-aorta diastolic ratio.
      • Kimura B.J.
      • Fowler S.J.
      • Fergus T.S.
      • Minuto J.J.
      • Amundson S.A.
      • Gilpin E.A.
      • DeMaria A.N.
      Detection of left atrial enlargement using hand-carried ultrasound devices: Implications for bedside examination.
      and also has prognostic implications.
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      • Wolf P.A.
      • Levy D.
      Left atrial size and the risk of stroke and death: the Framingham Heart study.
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      • Bailey K.R.
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      Prediction of risk for first age-related cardiovascular events in an elderly population: the incremental value of echocardiography.
      • Douglas P.S.
      The left atrium: a biomarker of chronic diastolic dysfunction and cardiovascular risk.
      In the present study, CLUE subjectively compared the LA diameter to that of the overlying aorta in the parasternal long-axis view, a method that has been shown to relate to the LA volume index.
      • Kimura B.J.
      • Kedar E.
      • Weiss D.E.
      • Wahlstrom C.L.
      • Agan D.L.
      A hand-carried ultrasound sign of cardiac disease: the left atrium-to-aorta diastolic ratio.
      LA enlargement found using the CLUE had a greater prevalence in inpatients compared to outpatients (53% vs 38%, respectively, p = 0.0002) and an accuracy of 73% compared to standard echocardiography. Subjective recognition of LA enlargement is simple, had the least technically difficult data in the present investigation (4.3% of studies), and, similar to the recognition of LV systolic dysfunction,
      • Kimura B.J.
      • Amundson S.A.
      • Willis C.L.
      • Gilpin E.A.
      • DeMaria A.N.
      Usefulness of a hand-held ultrasound device for bedside examination of left ventricular function.
      can be performed by novices to improve bedside diagnosis.
      • Kimura B.J.
      • Fowler S.J.
      • Fergus T.S.
      • Minuto J.J.
      • Amundson S.A.
      • Gilpin E.A.
      • DeMaria A.N.
      Detection of left atrial enlargement using hand-carried ultrasound devices: Implications for bedside examination.
      The presence of pulmonary edema is critical in respiratory failure or shock and is related to a worse prognosis whether cardiogenic
      • Gray A.
      • Goodacre S.
      • Newby D.E.
      • Masson M.
      • Sampson F.
      • Nicholl J.
      3CPO Trialists
      Noninvasive ventilation in acute cardiogenic pulmonary edema.
      or noncardiogenic.
      • Reynolds H.N.
      • McCunn M.
      • Borg U.
      • Habashi N.
      • Cottingham C.
      • Bar-Lavi Y.
      Acute respiratory distress syndrome: estimated incidence and mortality rate in a 5 million-person population base.
      The ULC artifact has recently been described as a sign of pulmonary edema
      • Lichtenstein D.
      • Meziere G.
      • Biderman P.
      • Gepner A.
      • Barre O.
      The comet-tail artifact: an ultrasound sign of alveolar-interstitial syndrome.
      • Jambik Z.
      • Monti S.
      • Coppola V.
      • Agricola E.
      • Mottola G.
      • Miniati M.
      • Picano E.
      Usefulness of ultrasound lung comets as a nonradiologic sign of extravascular lung water.
      and is easily detected by novice users
      • Bedetti G.
      • Gargani L.
      • Corbisiero A.
      • Frassi F.
      • Poggianti E.
      • Mottola G.
      Evaluation of ultrasound lung comets by hand-held echocardiography.
      but can also be present as a normal finding in the lung bases.
      • Lichtenstein D.
      • Meziere G.
      • Biderman P.
      • Gepner A.
      • Barre O.
      The comet-tail artifact: an ultrasound sign of alveolar-interstitial syndrome.
      Similar to results from an outcome study that used a complex 28-site lung imaging protocol on 290 inpatients,
      • Frassi F.
      • Gargani L.
      • Tesorio P.
      • Raciti M.
      • Mottola G.
      • Picano E.
      Prognostic value of extravascular lung water assessed with ultrasound lung comets by chest sonography in patient with dyspnea and/or chest pain.
      the present study observed a significant relation between the comet tail artifacts and inpatient mortality but with a larger sample of 792 inpatients and using a simpler, 2-site protocol.
      The IVC diameter response to inspiration has been shown to relate to the right atrial pressures.
      • Kircher B.J.
      • Himelman R.B.
      • Schiller N.B.
      Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava.
      • Brennan J.M.
      • Blair J.E.
      • Goonewardena S.
      • Ronan A.
      • Shah D.
      • Vasaiwala S.
      • Kirkpatrick J.N.
      • Spencer K.T.
      Reappraisal of the use of inferior vena cava for estimating right atrial pressure.
      In a recent study of hand-carried ultrasonography used by briefly trained resident physicians, the noncollapsible IVC demonstrated prognostic value in 75 patients with acute decompensated heart failure by its relation to hospital readmission.
      • Goonewardena S.N.
      • Gemignani A.
      • Ronan A.
      • Vasaiwala S.
      • Blair J.
      • Brennan J.M.
      • Shah D.P.
      • Spencer K.T.
      Comparison of hand-carried ultrasound assessment of the inferior vena cava and N-terminal pro-brain natriuretic peptide for predicting readmission after hospitalization for acute decompensated heart failure.
      In the present study in which all inpatients referred for echocardiography were included, IVC plethora was present in 34% and demonstrated a very strong relation (OR 6.36, 95% CI 2.66 to 15.21) to inpatient mortality, perhaps as a general sign reflecting severe respiratory failure. The present study did not analyze whether tachypnea, positive pressure ventilation, greater intra-abdominal pressures, or diminished mental status were present during the echocardiogram, all factors that could have confounded the relation of the IVC to right atrial pressure but could have still contributed to a worse prognosis.
      The present study was limited by its use of a retrospective review of standard echocardiograms and was not a validation of CLUE when performed by new users with pocket-size devices during the initial patient examination. Because device capabilities and teaching curriculum are still in development, we used the “best-case scenario” of optimal acquisition and expert interpretation of data to investigate the ultimate potential of the CLUE. The CLUE was designed as a grossly simplified, 2-dimensional general-purpose ultrasound examination and should be differentiated from a “limited” or “focused” echocardiogram in which a specific clinical or follow-up question is fully answered using an abbreviated imaging protocol and conventional echocardiographs. In the future, it might be possible for the more advanced practitioner of bedside ultrasonography to diagnose other less common entities from the acquired CLUE views or expand CLUE to include the use of Doppler in specific clinical circumstances.

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