[Evaluation of the effects of coronary artery bypass grafting on left ventricular function in patients with previous myocardial infarction].

The present study was designed to assess a left ventricular function following coronary artery bypass grafting (CABG) in patients with previous myocardial infarction (MI). The subject was consisted of 10 patients with MI (MI(+) group) and 6 without it (MI(-) group). Both groups underwent complete revascularization. Stroke index (SI), ejection fraction (EF), systolic pressure/end-systolic volume index (SP/ESVI) and end-diastolic volume index (EDVI) were evaluated utilizing radionuclide angiography at rest and during exercise (Ex) before and after CABG. The influence of size of myocardial infarction on left ventricular function were also analyzed. Preoperatively during Ex, EF showed decrease, SP/ESVI no change and EDVI increase in both MI(+) and MI(-) group compared with those at rest. Postoperatively during Ex, SI, EF and EDVI showed no change and SP/ESVI increase in both MI(+) and MI(-) group compared with those at rest. Ejection fraction and SP/ESVI during Ex in MI(+) group had significant differences compared with those in both MI(-) group and control group. Ejection fraction and SP/ESVI during Ex in MI(-) showed no difference compared with those in control group. The size of MI suggested by ECG scoring system (proposed by Wagner GS et al, Circulation '82) had negative correlations with both Ex-induced increment of postoperative EF and Ex-induced increase ratio of postoperative SP/ESVI. These data indicated that complete revascularization improved EF and SP/ESVI in patients with MI, and moreover normalized those in patients without MI. But in the case of extensive MI, even complete revascularization might not recover poor functional reserve during Ex.