Acute Myocardial Infarction and Complete Bundle Branch Block at Hospital Admission: Clinical Characteristics and Outcome in the Thrombolytic Er

Objectives. We sought to assess the outcome of patients with acute myocardial infarction (MI) and bundle branch block in the thrombolytic era. Background. Studies of patients with acute MI and bundle branch block have reported high mortality rates and poor overall prognosis. Methods. The North American population with acute MI and bundle branch block enrolled in the Global Utilization of Streptokinase and t-P [tissue-type plasminogen activator] for Occluded Coronary Arteries (GUSTO-I) trial was matched by age and Killip class with an equal number of GUSTO-I patients without conduction defects. Results. Of all 26,003 North American patients in GUSTO-I, 420 (1.6%) had left (n = 131) or right (n = 289) bundle branch block. These patients had higher 30-day mortality rates than matched control subjects (18% vs. 11%, p = 0.003, odds ratio [OR] 1.8) and were more likely to experience cardiogenic shock (19% vs. 11%, p = 0.008, OR 1.78) or atrioventricular block/asystole (30% vs. 19%, p < 0.012, OR 1.57) and to require ventricular pacing (18% vs. 11%, p = 0.006, OR 1.73). Bundle branch block also carried an independent 53% higher risk for 30-day mortality. Thirty-day mortality rates for patients with complete, partial and no reversion of the bundle branch block were 8%, 12% and 20%, respectively (two-tailed chi-square test for trend 5.61, p = 0.02, OR 0.34 for complete reversion, OR 0.55 for partial reversion). Conclusions. Bundle branch block at hospital admission in patients with acute MI predicts in-hospital complications and poor short-term survival.