We describe the spontaneous long-term changes in right (RV) and left (LV) ventricular performance during a 7-year period after acute myocardial infarction (AMI). Radionuclide ventriculography was performed in the second week after AMI in 201 patients. RV and LV ejection fractions, and LV end-diastolic and end-systolic volumes were determined. A follow-up after 7 years was performed in 55 survivors. Of these, 16 patients were also examined after 1 year. During the 7-year follow-up period, LV ejection fraction decreased from 0.49 to 0.45 (p < 0.01). LV end-diastolic volume increased from 161 to 210 ml (30%) (p < 0.01), and LV end-systolic volume from 83 to 123 ml (48%) (p < 0.01). In patients without recurrent AMI, coronary artery bypass grafting surgery, or angiotensin-converting enzyme inhibitor therapy (n = 37) during follow-up, no change in average LV ejection fraction was observed. Nevertheless, this subgroup had substantial increases in LV end-diastolic volume, from 157 to 190 ml (21%) (p = 0.002) and in LV end-systolic volume, from 80 to 105 ml (31%) (p < 0.001). In a subgroup of patients also reinvestigated after 1 year (n = 16), there was a 15% increase in LV end-diastolic volume the first year after AMI with an additional 10% increase in LV end-diastolic volume between years 1 and 7. Corresponding figures for LV end-systolic volume were 20% and 12%, respectively. Hardly any association was apparent between LV ejection fraction, LV end-diastolic volume, and LV stroke volume at discharge for subsequent LV dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)