Continuous ventricular dimensions in man during supine exercise and recovery. An echocardiographic study

Ten healthy men aged 18 to 23 years performed supine bicycle ergometer exercise during continuous echocardiographic recording. Beat to beat analysis of ventricular dimensions revealed that during constant work load exercise end-diastolic dimension did not change and end-systolic dimension decreased insignificantly by 4 percent. The stroke dimension and fractional shortening of the ventricular dimension rose 7 and 5 percent, respectively. During recovery, end-diastolic dimension and stroke dimension increased above the resting value, beginning 26 seconds (range 16 to 45) after cessation of exercise, whereas heart rate fell promptly to resting levels by 37 seconds. The peak increase in end-diastolic dimension and stroke dimension averaged 11 and 35 percent, respectively. Endsystolic dimension coincident with peak end-diastolic dimension decreased 11 percent in 6 of 10 subjects, and was unchanged in four. Fractional shortening of the ventricular dimension increased 8 percent (P < 0.025) in parallel with end-diastolic dimension. These dimensional changes indicate a significant increase in end-diastolic dimension and stroke dimension in all 10 subjects during the recovery phase of supine exercise with a parallel rise in the percent shortening of the ventricular dimensions. During exercise a clear Frank-Starling effect is masked, whereas during recovery the continuing high level of venous return is dissociated from the decreasing heart rate, resulting in a transient increase in end-diastolic volume and a measurable Frank-Starling effect.