This study clarified the effects of residual stenosis following successful thrombolysis in acute myocardial infarction on infarct size and cardiac function in the chronic stage. Subjects consisted of 24 patients with acute anteroseptal myocardial infarction within six hours after the onset of symptoms, in whom thrombolysis was performed, and additional coronary angioplasty was performed in 10 patients. Great cardiac venous flow (GCVF) at a point 30 min after thrombolysis and angioplasty was examined by continuous thermodilution, and the minimal cross-sectional area (MCSA) was determined at a stenotic lesion using an orthogonal angiographic view. As an index of infarct size, we measured abnormally contracting segments (ACS) and perfusion defects (PD) in 201T1 single photon emission computed tomograms four weeks after the onset. We determined anterior regional ejection fraction (rEF) as an index of left ventricular performance in the chronic stage. The patients with thrombolysis alone and the patients with angioplasty were comparable as to age, gender elapsed time, GCVF, MCSA, ACS, PD and rEF. In all the patients, MCSA did not correlate significantly with GCVF. In the patients with additional angioplasty, MCSA significantly increased (from 0.3 +/- 0.3 mm2 to 2.5 +/- 1.6 mm2). However, GCVF did not necessarily increase in all the angioplasty patients. In four patients having delays in angiographic flow, and MCSA less than 0.1 mm2, there was a significant increase in GCVF after angioplasty (41.3 +/- 32.0 vs 82.0 +/- 60.7 ml/min). GCVF correlated significantly with ACS, PD, and rEF, but MCSA did not correlate significantly with them. We concluded that in patients with successful thrombolysis but without angiographic filling delay, emergency angioplasty for residual stenosis has no effect on further limitation of infarct size.