Effect of myocardial ischaemia on left ventricular function and adaptability to exercise training

Purpose: We evaluated the possible interaction between exercise-induced myo cardial ischemia and abnormalities in left ventricular function in 72 patie nts with coronary artery disease at entry and upon discharge from a 6-month exercise training program. Methods: Twenty-two patients with myocardial is chemia (MIS) defined by electrocardiographic and radionuclide imaging crite ria constituted our experimental group (EG). Fifty patients without MIS wer e assigned to the control group for exercise training (CG-ET) and 31 health y subjects to the control group for measures of left ventricular function ( CG-LV). Results: Both groups EG and CG-ET showed significant and comparable increases in peak oxygen uptake (EG: 25.2 +/- 5.1 to 26.9 +/- 5.4 mL.kg(-1 ).min(-1), P < 0.02; CG-ET: 25.1 +/- 0.6 to 27.4 +/- 0.7 mL.kg(-1).min(-1), P < 0.001) after exercise training, but only CG-ET showed significant redu ctions in heart rate, systolic blood pressure, and rate-pressure product du ring submaximal exercise. A significant increase in end-diastolic volume co ntributed to the increase in cardiac output during exercise in patients wit h MIS. Heart rate or treadmill time at onset of ST segment depression faile d to increase as a result of training, and stroke counts and the product of stroke counts and heart rate showed a trend toward a decrease in response to exercise, suggesting progression of disease. Conclusions: Patients with myocardial ischemia showed improvements in maximal exercise capacity but fa iled to elicit physiologic adaptations during submaximal exercise or to inc rease the threshold for ischemia after exercise training. It is possible th at the main emphasis in the management of this type of patient in a cardiac rehabilitation setting should be placed more on coronary risk factor modif ication to slow progression of disease than on improving cardiovascular eff iciency.