Partial bilateral bundle branch block in acute myocardial infarction.

The relationship of partial bilateral bundle branch Mock to hospital mortality from acute myocardial infarction (MI) was studied concerning the need for prophylactic temporary transvenous pacemakers. Factors examined for their contributions to hospital mortality in 156 consecutive patients with acute MI were: age, sex, race, infarct location, number of prior infarctions, heart failure class (1-4), bundle branch Mock (BBB), and partial bilateral BBB (right BBB with an abnormal superior or rightward mean QRS axis, or both right and left BBB). Partial bilateral BBB occurred in 12 patients (8 percent) with 50 percent mortality. None of these deaths was attributable to sudden complete heart block or asystole. The prognosis of patients with partial bilateral BBB and acute MI is related to the extent of myocardial damage, not to complete heart Mock or electrical instability. Thus, prophylactic temporary transvenous pacing may not be beneficial in patients with acute myocardial infarction and partial bilateral bundle branch block.