Bundle-Branch Block Complicating Acute Myocardial Infarction

Nineteen patients with right bundle-branch block (RBBB) and 20 with left bundle-branch block (LBBB) were treated in a coronary care unit for acute myocardial infarction during a 4 1/2-year period. Twenty-six percent of patients with RBBB developed cardiogenic shock, 32% had complete atrioventricular block, and 26% had ventricular asystole. Mortality was 37%, primarily from myocardial failure rather than asystole or arrhythmia. Pacemaker therapy was generally unsuccessful in reducing mortality. In contrast, 70% of the group with LBBB suffered life-threatening ventricular arrhythmia during or in close proximity to the acute phase of myocardial infarction. Mortality was 35%. Electrophysiologic mechanisms may influence ventricular irritability in patients with LBBB and ischemic heart disease. Consideration should be given to prophylactic antiarrhythmic therapy in these patients at least during hospitalization for acute myocardial infarction.