Abstract 14559: Utility of New Left Bundle Branch Block as a Diagnostic Criterion for Acute Myocardial Infarction
Background: The clinical utility of new or ‘presumably new’ left bundle branch block (LBBB) as a ST-elevation myocardial infarction (STEMI)-equivalent ECG diagnostic criterion in contemporary practice is not well established. Aims: We evaluated the frequency, clinical characteristics, and outcomes of patients with new LBBB suspected of acute myocardial infarction (AMI).
Methods: We retrospectively analyzed the data from consecutive patients in the Mayo Clinic STEMI network.
Results: There were 36 (4%) patients with new LBBB. Compared to patients with STEMI but without LBBB (n=856), those with new LBBB were older (64.5 vs 72.9 years, p<0.001), had higher modified TIMI risk scores (22.7 vs 31.0, p<0.005), were less likely to undergo primary PCI (86% vs 22%, p<0.001), had longer door-to-balloon times, and a higher 6-month mortality (37% vs 12%, p<0.01) (Figure 1). Of the 36 patients with LBBB, only 14 (39%) had a final diagnosis of acute coronary syndrome (ACS) of which 12 were AMI, while 13 (36%) had cardiac diagnoses other than ACS, and 9 (25%) had non cardiac final diagnoses. Of the patients with AMI, 5 had an occluded culprit artery of which 3 involved the left anterior descending artery. A Sgarbossa score of ≥ 5 had poor sensitivity (14%) but 100% specificity in diagnosing AMI in the presence of new LBBB.
Conclusions: New or presumably new LBBB, among contemporary patients suspected of an AMI, identifies a high risk subgroup. However, only a minority have an AMI. Two-thirds of these patients are discharged from the hospital with an alternative diagnosis. The Sgarbossa criteria are not useful in clinical practice due to low sensitivity.
- © 2010 by American Heart Association, Inc.