Twenty patients with a first acute myocardial infarction (AMI) (15 anterior, 5 inferior) who received successful reperfusion therapy underwent tomographic imaging with technetium-99m (Tc-99m) sestamibi and radionuclide ventriculography at discharge, 6 weeks, and 1 year after AMI. Patency of the infarct-related artery after reperfusion (thrombolysis, 8 patients; coronary angioplasty, 12 patients) was confirmed by angiogrpahy in all patients. Tc-99m sestamibi perfusion defect at discharge (a measure of infarct size) was quantitated using previous methods and expressed as a percentage of the left ventricle (28 +/- 19%, range 0 to 59%). This perfusion defect size correlated closely with ejection fraction at discharge (r = -0.87), 6 weeks (r = -0.81) and at 1 year (r = -0.78, all p less than 0.0001). Perfusion defect size at discharge also correlated closely with end-systolic volume index at discharge (r = 0.71, p less than 0.0005), 6 weeks (r = 0.63, p less than 0.005) and at 1 year (r = 0.76, p less than 0.0001). Perfusion defect size at discharge did not correlate significantly with end-diastolic volume index at discharge or at 6 weeks, but did correlate at 1 year (r = 0.66, p less than 0.005). There was no significant group change in end-systolic or end-diastolic volume indexes from discharge to 1 year later, although 7 patients had definite individual changes in end-diastolic volume index (3 increased and 4 decreased). There was no relation between defect size and late changes in end-systolic volume index, but there was a weak correlation between defect size and late changes in end-diastolic volume index (r = 0.42, p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)