To determine the spectrum and prognostic implications of left and right ventricular (LV and RV) ejection fractions (EFs) in acute myocardial infarction (AMI), radionuclide ventriculography was performed in 114 consecutive patients, admitted without (Killip class I, 78 patients) or with (killip class II, 36 patients) clinical signs of pulmonary congestion within 24 hours of onset of symptoms of a transmural AMI. Mean LVEF was significantly lower in patients in Killip class II than in those in class I (0.32 +/- 0.11 vs 0.46 +/- 0.15, p less than 0.001) and in patients with anterior than inferior AMI (0.34 +/- 0.11 vs 0.52 +/- 0.14, p less than 0.001). Of the 36 patients with a severely depressed (0.30 or less) LVEF, 15 (42%) were in Killip class I. Mean RVEF did not differ significantly between Killip class I and II patients (0.42 +/- 0.11 vs 0.40 +/- 0.12, difference not significant) but was significantly lower in patients with inferior than anterior AMI (0.38 +/- 0.09 vs 0.44 +/- 0.11, p = 0.005). In patients with inferior AMI, a depressed RVEF (0.38 or less) was associated with a normal LVEF in 30% and a depressed LVEF in 20%, whereas in those with anterior AMI, a depressed RVEF, observed in 25% of patients, occurred only in association with a depressed LVEF.(ABSTRACT TRUNCATED AT 250 WORDS)