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Time-dependent increase in left ventricular contractility following acute volume loading in the dog
1Department of Medicine, Veterans Administration Medical Center, San Diego, CA 92161.
Circulation Research
|September 1, 1988
Summary
Acute volume loading increases left ventricular contractility, demonstrating a volume-dependent component. This effect, measured by end-systolic pressure-length relations, indicates enhanced cardiac muscle function following volume alterations.
Area of Science:
- Cardiology
- Physiology
Background:
- Left ventricular contractility is crucial for cardiac output.
- The influence of acute volume changes on contractility requires further elucidation.
Purpose of the Study:
- To investigate whether left ventricular contractility is partially dependent on acute volume alterations.
Main Methods:
- Acute volume loading was induced in anesthetized dogs via dextran infusion or vena cava occlusion.
- Left ventricular pressures and regional midwall function were monitored using micromanometry and sonomicrometry.
- Regional end-systolic pressure-length relations (ESPLR) were analyzed following interventions, with reflex responses prevented.
Main Results:
- Acute volume loading led to a time-dependent, leftward shift in the regional ESPLR, indicating increased contractility.
- This enhancement in contractility was observed even after preventing reflex responses and was not due to catecholamine increase.
- A transient decrease in venous return resulted in a rightward shift of the ESPLR, suggesting volume dependency.
Conclusions:
- Left ventricular contractility exhibits a partial, acute volume-dependent component.
- Acute volume loading can enhance myocardial contractility through mechanisms independent of reflex or hormonal influences.