We assessed the predictive value of 99Tcm-sestamibi gated single photon emission tomography (SPET) for changes in perfusion and functional outcome after an acute myocardial infarction and compared the findings on functional recovery with echocardiography using low-dose dobutamine. Gated 99Tcm-sestamibi SPET and radionuclide angiocardiography were performed in 17 patients 4-10 days after an acute myocardial infarction. Six months later, both isotopic studies and rest-dobutamine echocardiography were performed to assess outcome. Perfusion improved in six of seven severely hypoperfused segments (positive predictive value = 85.7%) that showed wall thickening but not in any of 28 segments (negative predictive value = 100%) without wall thickening. The mean ejection fraction improved from 47.7 to 52.3% (P = 0.018). Furthermore, there was a greater improvement in ejection fraction in the group of patients in whom wall thickening predicted a recovery in perfusion (9.0 vs 3.7%, P = 0.01). A comparison of the assessment of functional recovery between gated SPET and dobutamine echocardiography showed good agreement (81.4%). We conclude that the presence of wall thickening in severely hypoperfused segments on 99Tcm-sestamibi gated SPET is predictive of changes in perfusion and functional recovery after acute myocardial infarction, thus identifying the presence of viable myocardium. In contrast, segments showing hypoperfusion and dysfunction after an acute myocardial infarction probably contain scar tissue only.