Between April 1988 and November 1998, 82 patients underwent isolated coronary artery bypass grafting within 30 days of acute myocardial infarction. The infarct-related artery was the proximal right coronary artery (27 patients; group 1) and the left coronary artery (55 patients; group 2). In group 2 the infarct-related artery was the left main coronary artery (8 patients), the left anterior descending coronary artery (33 patients), and the left circumflex coronary artery (14 patients). There was no difference between groups 1 and 2 with regard to sex, age (65 +/- 9 vs 66 +/- 10, respectively), presence of diabetes, renal insufficiency, previous myocardial infarction, and preoperative use of an intraaortic balloon pump (67% vs 71%, respectively). Compared with group 2, group 1 patients more often had three-vessel or left main disease (93% vs 65%, respectively; p = 0.018), a higher number of bypass grafts (3.0 +/- 0.8 vs 2.5 +/- 0.7, respectively; p = 0.014), and a greater incidence of postoperative complete atrioventricular (AV) block (30% vs 6%, respectively; p = 0.005). The hospital mortality rate for patients who underwent surgery within 48 hours after acute myocardial infarction did not differ between groups 1 and 2 (22% vs 18%, respectively). However, patients in both groups who underwent surgery between 48 hours and 30 days after infarction had significantly different mortality rates (22% vs 0%, respectively; p = 0.037). Patients with postoperative complete AV block had high mortality rates of 38% in group 1 and 67% in group 2. We conclude that patients who undergo coronary bypass surgery within 30 days of acute inferior myocardial infarction have a high incidence of postoperative complete AV block, which result in increased mortality.