Clinical and electrocardiographic features of 227 patients who died of an acute myocardial infarction (AMI) were compared with those of 150 survivors of a first AMI. Left ventricular (LV) free wall rupture was found in 93 patients aged > 50 years, but not in 134. The incidence of healed infarct (4 [4%] vs 50 [37%], p < 0.001), heart failure (11 [12%] vs 112 [84%], p < 0.001), and bundle branch block (11 [12%] vs 54 [40%], p < 0.001) was lower in patients with than without LV rupture. In patients with anterior AMI and early rupture (1 day), admission ST elevation was higher than in those with late LV rupture (> 1 day, 6.8 +/- 4.0 vs 4.0 +/- 2.7 mm, p < 0.01). However, lateral wall AMI had minimal ST elevation and accounted for 10% of ruptures. On day 2, the decrease in ST segment in patients with late LV rupture was less than in survivors (0.5 +/- 1.6 vs 3.2 +/- 2.9 mm, p < 0.001). Admission systolic blood pressure in patients who had early rupture was higher than in survivors (155 +/- 22 vs 137 +/- 22 mm Hg, p < 0.001) and in those with late rupture (135 +/- 23 mm Hg, p < 0.001). Late rupture was associated with infarct thinning and triggered by a physical strain in 18 of 45 patients (40%); infarct thinning, however, was present only in 4 of 48 patients (8%) with early rupture (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)