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Afterloading increases the left ventricular end-systolic force-length relation slope in dogs
R Kadota1, K Takeda, T Shimizu
1Department of Medicine, Dokkyo University School of Medicine, Tochigi, Japan.
Japanese Heart Journal
|September 1, 1991
Summary
Gradual aortic occlusion significantly enhances left ventricular (LV) myocardial contractility. This pressure loading effect, observed in dogs, may involve length-dependent calcium activation, improving cardiac function.
Area of Science:
- Cardiology
- Physiology
Background:
- Left ventricular (LV) myocardial contractility is crucial for cardiac function.
- Understanding how pressure loading affects contractility is vital for cardiovascular research.
Purpose of the Study:
- To evaluate the impact of gradual aortic occlusion on LV myocardial contractility.
- To assess changes in the LV end-systolic force-diameter (Fes-Des) relation under pressure loading.
Main Methods:
- Utilized ultrasonic crystals and a micromanometer in eleven adult mongrel dogs.
- Measured LV diameter and pressure during vena caval occlusion (VCO) for preload reduction and aortic occlusion (AOO) for afterload increase.
- Determined the slope (Ec) and extrapolated diameter intercept (Do) of the LV Fes-Des relation.
Main Results:
- Heart rate remained relatively stable during both VCO and AOO.
- Both Ec and Do values were significantly increased during AOO compared to VCO (p < 0.001).
- Specifically, Ec increased from 62.8 +/- 15.6 g/cm to 122.6 +/- 18.6 g/cm, and Do from 1.20 +/- 0.36 cm to 1.66 +/- 0.38 cm.
Conclusions:
- Gradual aortic occlusion leads to increased LV myocardial contractility in anesthetized, open-chest dogs under autonomic blockade.
- The observed enhancement in contractility may be attributed to length-dependent calcium activation.
- This finding provides insights into the mechanisms of cardiac adaptation to increased afterload.