Abstract

To better characterize the relationship between left ventricular volume response and improved ventricular ejection and output during supine exercise in normal subjects, 36 healthy volunteers (39+-17 yr) were studied with radionuclide ventriculography during recumbent bicycle ergometry. Relative changes in left ventricular end-diastolic and end-systolic volume were measured at rest and during exercise by a modification of the radionuclide counts-based method that accounted for variability in stress blood pool counts. A biphasic response was noted in left ventricular end-diastolic volume with an initial increase in early exercise followed by a progressive and significant decline at peak exercise. There was substantial variation in end-diastolic volume response at peak exercise in the group as a whole, which could be more closely related to changes in end-systolic volume than in heart rate or age of the subjects. Despite the decline in ventricular filling, systolic function appeared to improve dramatically at peak exercise. Although not directly related to increasing systolic ejection, end-diastolic volume was directly related to the percent change in stroke volume at peak exercise in the subjects. We conclude that progressive supine exercise is characterized by marked augmentation of left ventricular ejection, which is not directly related to increased left ventricular preload. In contrast, left ventricular end-diastolic volume was directly related to the change in stroke volume noted during progressive recumbent exercise. Verf.-Ref.