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Intrinsic left ventricular contractility in normal subjects
M W Kronenberg1, J P Uetrecht, W D Dupont
1Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
The American Journal of Cardiology
|March 1, 1988
Summary
Autonomic tone does not significantly influence resting left ventricular (LV) contractility in healthy individuals. However, LV contractility, measured by pressure-volume relations, is sensitive to exercise and reproducible in serial studies.
Area of Science:
- Cardiology
- Physiology
Background:
- Autonomic tone plays a role in cardiovascular regulation.
- Understanding left ventricular (LV) contractility is crucial for assessing cardiac function.
Purpose of the Study:
- To investigate the influence of autonomic tone on LV contractility in normal subjects.
- To determine the range of normal LV contractility values.
- To assess the effects of exercise on LV contractile state and the reproducibility of measurements.
Main Methods:
- LV contractility assessed using LV peak-systolic pressure to end-systolic volume relation (pressure-volume relation) and pressure/volume ratio.
- Measurements taken at rest, during exercise, and pharmacologic pressure-afterloading.
- Vagal and beta-adrenergic blockade performed before and after interventions.
- Cuff blood pressure and radionuclide ventriculography utilized.
Main Results:
- Both pressure/volume ratio and ejection fraction increased significantly during exercise (p ≤ 0.008).
- Autonomic blockade did not alter the linearity or slope of pressure-volume relations.
- Serial studies demonstrated high reproducibility of pressure-volume relations (r = 0.95 ± 0.05).
Conclusions:
- Resting LV contractility in normal subjects is not significantly supported by vagal or sympathetic tone.
- The pressure-volume relation and pressure/volume ratio are reproducible, supporting serial studies.
- Exercise significantly impacts LV contractility, as evidenced by changes in pressure/volume ratio and ejection fraction.