Prognostic significance of chronic versus acute bundle branch block in acute myocardial infarction.

Of 1125 patients with acute myocardial infarction admitted to Mount Sinai Medical Center in 1971 and 1972, 292 (28.8 percent) had intraventricular conduction defects. In 210 of the 292 patients with intraventricular conduction defect, it was possible to determine if the conduction defect, was present before the infarction (Group 1, 123 patients) or developed acutely with the infarction (Group 2, 87 patients). Of the 210 patients, 52.8 percent died (mean age 72.1 years). Fifty-three patients in Group 1 and 18 patients in Group 2 had isolated left axis deviation (LAD). The mortality was 35 percent and 28 percent respectively. This difference was not significant (p greater than 0.60). Sixty-four of the 210 patients presented with a left bundle branch block (LBBB) pattern. The overall mortality of 54 percent was the same in both groups. Right bundle branch block(RBBB), with either normal axis, left (LAD) or right axis deviation (RAD), was found in 74 patients. Of 40 patients in Group 1, 62 percent died, and of 35 patients in Group 2, 80 percent expired. Again this difference was not significant (p greater than 0.10). In 13 of 25 patients with RBBB in Group 1, death was possible related to progression of the conduction defect. The use of prophylactic temporary pacing is suggested for these patients.