To determine the effect of thrombolytic therapy on the frequency of right ventricular (RV) dysfunction, and whether RV dysfunction is a risk factor for morbidity and mortality after discharge from the hospital, 1,110 patients in the Thrombolysis in Myocardial Infarction (TIMI) II trial with acute inferior wall left ventricular myocardial infarction were studied. RV dysfunction was defined as an RV wall motion abnormality on equilibrium radionuclide ventriculography performed a mean of 9 days after admission to the hospital. Fifty-eight patients (5%) had RV dysfunction. Baseline clinical characteristics among patients with and without RV dysfunction were similar. However, patients with RV dysfunction had a lower mean left ventricular ejection fraction (51.2 +/- 1.2% vs 55.5 +/- 0.3%; p < 0.001) and a greater frequency of in-hospital complications. Angiographic data from patients undergoing protocol catheterization 18 to 48 hours after hospital admission show that the infarct-related artery was more likely to be occluded in those with RV dysfunction (48% [15 of 31] vs 14% [68 of 495]; p < 0.001). There was no difference in the frequency of multivessel disease between the 2 groups. In patients with RV dysfunction in whom radionuclide ventriculography was repeated 6 weeks after hospital discharge, RV wall motion abnormalities persisted in only 18% (8 of 45). Mortality in the year after discharge was 3.5% (2 of 58) among patients with RV dysfunction compared with 1.7% (18 of 1,052; p = NS) among those without RV dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)