Increased Arteriovenous Oxygen Difference After Physical Training in Coronary Heart Disease

Abstract

A preliminary study of 12 male patients (mean age, 47.8 years) with coronary heart disease (six with angina pectoris and six with prior myocardial infarction but without angina) was conducted according to a common protocol in Seattle, Washington, and Louvain, Belgium. Maximal oxygen intake (Vo_o2 max) and hemodynamic studies at rest and at two or three levels of submaximal exercise in the upright position were obtained before and after a 3-month physical training program that involved three sessions of 45 min/week. "Vo_o2 max" increased 22.5% (P < 0.0001) with physical training. Changes in maximal heart rate occurred in the patients with angina (+8.4%) but not in those without angina (+0.8%). At rest and at each submaximal exercise, heart rate, mean blood pressure, and cardiac output decreased after training, whereas stroke volume was unchanged and arterio-mixed venous oxygen (A-Vo_o2) difference increased. The pressure-rate product and the left ventricular work decreased after training. The classic posttraining bradycardia was compensated not by a higher stroke volume but by an increased A-Vo_o2 difference which resulted from both a higher arterial oxygen content and an increased peripheral oxygen extraction. The latter was more apparent when exercises of the same relative intensity were compared. Thus, benefits with physical training in coronary patients result at submaximal exercise level from enhanced arterial oxygen content and peripheral extraction and secondarily from lower hemodynamic stress on ischemic myocardium. Increased maximal A-Vo_o2 difference probably explains most of the increase in "Vo_o2 max" with physical training in coronary patients not limited by angina pectoris.