The clinical utility of new or “presumably new” left bundle branch block (LBBB) as
an electrocardiographic criterion equivalent to ST-segment elevation myocardial infarction
in contemporary practice is not well established. The aim of this study was to investigate
the hypothesis that new or presumably new LBBB in symptomatic patients frequently
leads to an overdiagnosis of acute myocardial infarction (AMI). A retrospective analysis
of data from consecutive patients in the Mayo Clinic's ST-segment elevation myocardial
infarction network from July 2004 to August 2009 was conducted among 892 patients,
36 (4%) of whom had new LBBB. The frequency, clinical characteristics, serum troponin
levels, coronary angiographic findings, and outcomes of patients with new LBBB suspected
of having AMI were evaluated. Compared with patients without LBBB (n = 856), those
with new LBBB were older (64.5 vs 72.9 years, p <0.001), had higher Thrombolysis In
Myocardial Infarction (TIMI) risk scores (22.7 vs 31.0, p <0.005), were less likely
to undergo primary percutaneous coronary intervention (86% vs 22%, p <0.001), and
had longer door-to-balloon times. Only 14 patients (39%) had final diagnoses of acute
coronary syndromes, of which 12 were AMI, while 13 (36%) had cardiac diagnoses other
than acute coronary syndrome and 9 (25%) had noncardiac diagnoses. Of the patients
with AMI, 5 had occluded culprit arteries, of which 2 involved the left anterior descending
coronary artery. A Sgarbossa score ≥5 had low sensitivity (14%) but 100% specificity
in diagnosing AMI in the presence of new LBBB. In conclusion, new or presumably new
LBBB in patients suspected of having AMI identifies a high-risk subgroup, but only
a small number have AMI. Two thirds of these patients are discharged from the hospital
with alternative diagnoses. The Sgarbossa criteria appear to have limited utility
in clinical practice because of their low sensitivity.
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Article Info
Publication History
Published online: February 08, 2011
Accepted:
December 10,
2010
Received in revised form:
December 10,
2010
Received:
October 16,
2010
Identification
Copyright
© 2011 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
