Seventy-eight necropsy patients with transmural acute myocardial infarction (AMI) were studied to correlate the mode of death, the interval between onset of AMI and death and the presence or absence of coronary thrombus with the extent of the infarct. Infarct size was assessed quantitatively as a percentage of total left ventricular (LV) mass. Death was caused by cardiogenic shock in 16 patients (21%), arrhythmia in 31 patients (40%) and cardiac rupture in 24 patients (31%). The mean interval between the onset of AMI and death was 12 +/- 13 days. Infarct size averaged 23 +/- 14% of LV mass. Patients who died in cardiogenic shock had the largest infarcts (37 +/- 11%) and those who died of cardiac rupture had the smallest infarcts (15 +/- 9%) and the shortest interval between onset of AMI and death (7 +/- 8 days). Coronary thrombi were present in 58 patients (74%). When present, thrombus was observed in the coronary artery that had supplied the infarct area and was superimposed on advanced atherosclerotic plaque, but no relation was found between extent of luminal obstruction by thrombus and AMI size. The absence of coronary thrombus at necropsy was associated with either small infarcts or prolonged survival after AMI.