[Cardiac response to exercise before and after coronary artery bypass grafting: evaluation by continuous ventricular...

Cardiac response to exercise was evaluated with continuous ventricular function monitor (VEST) with cadmium telluride detector. Thirty-nine patients (30 male and 9 female, aged 57 +/- 8, 23 had old myocardial infarction) were monitored with VEST during and after supine ergometer exercise before and 4 weeks after coronary artery bypass grafting (CABG). Left ventricular ejection fraction (EF) responses were classified into 4 types; type A showed EF increase greater than 5% till end of exercise, type B demonstrated initial increase followed by decrease in EF, type C revealed no significant EF change, type D showed continuous EF decrease. Before CABG, each EF response type A, B, C, and D consisted of 4, 2, 12, 21 patients respectively and after CABG each type included 18, 10, 9, 2. The EF change from rest to peak exercise (delta EF-Ex) improved from -6.4 +/- 8.8% to 5.0 +/- 7.4% (p less than 0.001) after CABG. All patients showed rapid EF increase after exercise or "EF overshoot" (EF-OS). After CABG, the EF change from rest to EF-OS (delta EF-OS) and time to EF-OS (T-OS) were improved from 9.9 +/- 5.2% to 14.9 +/- 5.3% (p less than 0.001) and 162 +/- 86 sec to 80 +/- 48 sec (p less than 0.001) respectively. Type A, B patients showed higher delta EF-OS and shorter T-OS than type C, D patients, suggesting EF overshoot was contingent upon cardiac function during exercise. After CABG, in patients with myocardial infarction, T-OS shortened but delta EF-OS showed less improvement than patients without infarction, suggesting loss of myocardium hampered EF-OS.