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Inhibitory effect of cardiac contraction on coronary collateral blood flow
Insights
Cardiac contraction significantly reduces blood flow in collateral-dependent areas, especially in the ischemic mid-wall. This effect is more pronounced in ischemic regions compared to normally perfused ones.
Area of Science:
- Cardiovascular Physiology
- Myocardial Blood Flow
- Collateral Circulation
Background:
- Understanding blood flow dynamics in the heart is crucial for treating ischemic conditions.
- Collateral vessels play a vital role in supplying blood to ischemic areas.
- The impact of cardiac contraction on collateral flow distribution requires further elucidation.
Purpose of the Study:
- To investigate the effect of cardiac contraction on blood flow distribution within ischemic and normally perfused myocardial regions.
- To quantify the gradient of blood flow inhibition across the ventricular wall during beating versus cardiac arrest.
Main Methods:
- Created an ischemic region in the left ventricle by ligating the left anterior descending artery.
- Perfused the main left coronary artery at a constant pressure using a servo pump.
- Injected radiomicrospheres during normal beating and cardiac arrest (vagal arrest) to measure regional blood flow.
- Analyzed blood flow distribution across the epicardium, mid-wall, and endocardium.
Main Results:
- Cardiac contraction induced a gradient of blood flow inhibition, from near zero at the epicardium to approximately 50% at the endocardium.
- Blood flow inhibition in the ischemic mid-wall (71%) was significantly greater than in the normally perfused mid-wall (33%).
- Contraction markedly reduced collateral blood flow to the ischemic region, with magnified inhibition at the mid-wall.
Conclusions:
- Cardiac contraction inhibits collateral blood flow to ischemic myocardial regions.
- The inhibitory effect of contraction on collateral flow is significantly amplified in the mid-wall of ischemic zones.
- These findings highlight the detrimental impact of cardiac mechanical activity on perfusion in compromised heart areas.
Abstract:
The present study was undertaken to determine the effect of contraction on overall flow in an area supplied by collateral vessels. Changes in the distribution of blood flow across the wall of ischemic and normally perfused regions of the left ventricle were observed during normal beating and during vagal arrest. The main left coronary artery was cannulated and perfused at constant pressure (125 mmHg) using a servo pump apparatus. An ischemic area supplied by collaterals was created by ligating the left anterior descending artery. Radiomicrospheres (15 micrometer) were injected into the perfusion apparatus during beating. Then spheres with a different label were administered to the same heart during arrest. The results revealed that beating caused a gradient of blood flow inhibition from near zero at the epicardium to about 50% at the endocardium in both zones. Inhibition to flow at the mid wall of the ischemic zone, 71%, was significantly greater than that seen at the corresponding depth in the normally perfused region, 33%. These results indicate that contraction not only inhibits collateral blood flow to an ischemic region, but also that the inhibition is actually magnified at the mid wall.