Diastolic Time in Coronary Artery Disease: Postexercise Compromise and Compensation

Abstract

To evaluate left ventricular performance during recovery from exercise, 13 men with coronary artery disease, no history of infarction and normal systolic function (group 1) and 25 normals (group 2) were studied by ear densitography immediately, and at 2, 5 and 10 min after exercise in the upright position. Reference left ventricular ejection time-heart rate and electromechanical systole (EMS)-heart rate regression equations during the recovery period were obtained from group 2. Diastolic time (cardiac cycle - EMS) was calculated. Percent diastole (diastolic time/cardiac cycle X 100) increased significantly at 2 min after exercise compared to immediately after, while it decreased significantly from 2 to 5 min after exercise in group 1. Immediately after exercise, EMS in group 1 was significantly longer than expected from the reference regression equation, whereas there were no differences at 2 and 5 min postexercise. Consequently, diastolic time shortened immediately after exercise, but at 2 min postexercise diastole duration increased disproportionately in group 1, a response permitting prolonged myocardial perfusion. This would increase myocardial oxygen supply, while corresponding relative shortening of the duration of systole would decrease oxygen demand, together promoting recovery from ischemia.