Abstract 4317: Does a New or Presumed New Left Bundle Branch Block Have Equivalent Mortality to an Acute ST-Elevation Myocardial Infarction?
Background: The ACC/AHA Guidelines for Management of Patients with ST-Elevation Myocardial Infarction give a Class I recommendation for immediate reperfusion therapy for patients presenting with either ST elevations or a new or presumed new LBBB. However, the evidence supporting the recommendation for treatment of a new or presumed new LBBB is limited.
Objective: To determine if a new or presumed new left bundle branch block carries the same in-hospital mortality as a STEMI.
Methods: This retrospective study of the National Registry of Myocardial Infarction database compared the in-hospital mortality of 444,198 non-transfer patients presenting with new or presumed new LBBB, NSTEMI, STEMI, or anterior STEMI. Patients with old LBBB were excluded. A multivariate linear regression model adjusted for 53 independent variables representing patient demographics, previous medical history, clinical presentation, and treatments received, including reperfusion therapy.
Results: The unadjusted mortality for patients presenting with new or presumed new LBBB (19.1%) was significantly higher than STEMI (10.2%, p<0.001), anterior STEMI (12.2%, p<0.001), and NSTEMI (10.5%, p<0.001). However, patients with new or presumed new LBBB were older with more comorbidities and were less likely to receive aspirin, beta blockers, or anticoagulation. After adjusting for patient demographics, medical history, clinical presentation, and treatments received, the in-hospital mortality for new or presumed new LBBB patients was actually lower than both STEMI (OR 0.610, 95% CI 0.577 to 0.646) and anterior STEMI (OR 0.612, 95% CI 0.571 to 0.655), but higher than NSTEMI (OR 1.395, 95% CI 1.332 to 1.460).
Conclusions: A new or presumed new LBBB is associated with significantly lower in-hospital mortality than a STEMI. The marked discrepancy in prognosis suggests that a new or presumed new LBBB is not equivalent to a STEMI. The ACC/AHA recommendation for immediate reperfusion therapy for these patients should be reconsidered.