Residual flow to the infarct zone was assessed by coronary angiography during the acute phase of myocardial infarction in 130 patients. In 36 patients, the infarct-related coronary artery was not completely obstructed, thereby providing residual anterograde flow to the infarct area (Group I). Complete obstruction of the infarct vessel with residual flow to the infarct zone by means of collateral circulation was observed in 56 patients (Group II). Complete obstruction of the infarct vessel without residual flow was seen in 38 patients (Group III). Ejection fraction during the acute phase of infarction was found to be significantly higher in Group I (55 +/- 13%) than in either Group II (48 +/- 13%) or Group III (50 +/- 10%) (p less than 0.05). Group II patients had a longer history of angina pectoris (14.2 +/- 21.4 months) than did Group III patients (0.7 +/- 3.1 months) (p less than 0.01). Patients in Group I and Group II were more likely to be taking antianginal medication (56 and 54%, respectively) than were the patients in Group III (16%) (p less than 0.01). Thirty-seven patients in whom reperfusion techniques were not employed had repeat angiography in the chronic phase of infarction, enabling assessment of spontaneous changes in left ventricular function and coronary morphology.(ABSTRACT TRUNCATED AT 250 WORDS)