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Interrelationships between left ventricular volume and output during exercise in healthy subjects
K F Adams1, S M McAllister, H el-Ashmawy
1Department of Medicine, University of North Carolina School of Medicine, Chapel Hill 27599.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 11, 1992
Summary
During supine exercise, left ventricular end-diastolic volume initially increases then declines, while ejection fraction significantly improves. Stroke volume changes are closely linked to end-diastolic volume variations in healthy individuals.
Area of Science:
- Cardiology
- Exercise Physiology
- Medical Imaging
Background:
- Understanding the dynamic changes in left ventricular (LV) volume during exercise is crucial for assessing cardiac function.
- Previous studies have explored LV response to exercise, but the precise relationship between volume changes and improved ejection/output requires further characterization.
Purpose of the Study:
- To investigate the relationship between left ventricular volume response and enhanced ventricular ejection and output during supine exercise in healthy subjects.
- To characterize the biphasic response of left ventricular end-diastolic volume during graded exercise.
Main Methods:
- Utilized radionuclide ventriculography in 36 healthy volunteers during recumbent bicycle ergometry.
- Employed a modified radionuclide counts-based method to measure relative changes in LV end-diastolic and end-systolic volumes at rest and during exercise.
- Accounted for variability in stress blood pool counts for accurate volume assessment.
Main Results:
- Observed a biphasic response in left ventricular end-diastolic volume: initial increase followed by a significant decline at peak exercise (P < 0.05).
- Found substantial variation in end-diastolic volume response at peak exercise, strongly correlated with end-systolic volume changes (r = 0.84, P < 0.0001).
- Demonstrated a dramatic improvement in systolic function, evidenced by a significant increase in left ventricular ejection fraction (P < 0.0001), despite reduced ventricular filling.
Conclusions:
- Left ventricular end-diastolic volume exhibits a complex biphasic response during supine exercise in healthy individuals.
- Improved systolic function (ejection fraction) during exercise is not directly dependent on increasing ventricular filling (end-diastolic volume).
- The percent change in stroke volume at peak exercise is directly related to end-diastolic volume, highlighting its importance in cardiac output regulation.
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