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Effects of cardiac contraction on segmental coronary resistances and collateral perfusion
Insights
This study reveals how coronary arteries and microvessels react to changes in left ventricular pressure. Increased pressure can impair coronary collateral circulation, primarily affecting postcollateral microvessels.
Area of Science:
- Cardiovascular Physiology
- Coronary Circulation Research
Background:
- Understanding coronary circulation dynamics is crucial for managing cardiovascular diseases.
- The role of microvessels and collateral pathways in response to altered cardiac pressures requires further elucidation.
Purpose of the Study:
- To investigate the response of coronary arteries and microvessels to changes in left ventricular pressure.
- To assess the impact of these pressure changes on collateral circulation.
- To determine the localization of resistance changes within the coronary vasculature.
Main Methods:
- Measurement of collateral perfusion pressure in anesthetized dogs using microsphere embolization.
- Determination of segmental coronary resistances in arteries and microvasculature.
- Manipulation of left ventricular pressure via aortic clamping during autoregulation and maximal vasodilation.
Main Results:
- During autoregulation, increased left ventricular pressure decreased resistance in postcollateral microvessels.
- During maximal vasodilation, increased left ventricular pressure increased resistance in postcollateral microvessels.
- Ventricular fibrillation markedly decreased postcollateral microvasculature resistance.
Conclusions:
- Metabolic regulation and cardiac contraction predominantly influence postcollateral microvessels.
- Increased left ventricular pressure may impair coronary collateral circulation.
- Coronary microvasculature plays a key role in regulating coronary blood flow under varying pressures.
Abstract:
This study examined the reactions of coronary arteries and microvessels to changes in left ventricular pressure, as well as their significance for collateral circulation. Collateral perfusion pressure was measured as peripheral coronary pressure of an occluded coronary artery after embolisation of its terminal vascular bed with 20 micron microspheres in 9 anesthetized dogs. With measurement of collateral perfusion pressure it was then possible to determine the segmental coronary resistances of the coronary arteries and the microvasculature. Left ventricular pressure was increased by aortic clamping during autoregulation and after maximal pharmacological dilation of the coronary circulation. During autoregulation, the increase in left ventricular pressure induced a resistance decrease mainly in the postcollateral microvessels. With maximal vasodilation, the increase in left ventricular pressure induced a resistance increase mainly in the postcollateral microvessels. Finally with ventricular fibrillation, the resistance of the postcollateral microvasculature was markedly decreased. We conclude that both metabolic regulation of coronary blood flow and extravascular compression of coronary circulation by cardiac contraction act predominantly on postcollateral microvessels. Coronary collateral circulation may be impaired at increased left ventricular pressure.