In recent years, two pathophysiological conditions--stunned and hibernating myocardium--have been described showing how function may be depressed in myocardium that remains viable. The aims of the present study were postoperative assessment of LV function at rest and during exercise after CABG in patients with established previous myocardial infarction and impaired preoperative LV function and evaluation of preliminary experience with positron emission tomography (PET) in the preoperative identification of reversible ischaemic myocardium and its predictivity in postoperative functional improvement. We studied 23 patients with preoperative LV function under 45%. Echocardiography and complete heart catheter were performed pre- and postoperatively. PET was performed in all patients preoperatively. In 21 patients with patent grafts, CABG significantly improved systolic and diastolic function during exercise and at rest. EF improved from 34% +/- 14% to 52% +/- 11% at rest and from 31% +/- 14% to 58% +/- 13% during exercise (P less than 0.01). Time constant of diastolic relaxation was significantly reduced after revascularization. In 2 patients with pathological findings on postoperative coronarangiography, EF remained unchanged. Both global and regional contractility improved following surgery. Regional analysis indicated that improved EF at rest occurred in regions developing ischaemia during exercise before CABG and in regions showing typical mismatch in 82Rubidium-2-fluoro-2-desoxyglucose suggesting the presence of hibernating myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)