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The effect of cardiac contraction on collateral resistance in the canine heart
Insights
Coronary collateral resistance is minimally affected by systole. However, increased left ventricular end-diastolic pressure directly correlates with higher collateral resistance, impacting blood flow dynamics.
Area of Science:
- Cardiovascular Physiology
- Coronary Circulation Research
Background:
- The coronary vascular bed exhibits increased resistance during systole.
- The behavior of coronary collateral vessels during systole is not well understood.
Purpose of the Study:
- To investigate whether coronary collateral vessels develop increased resistance to blood flow during systole.
- To determine the relationship between left ventricular end-diastolic pressure and collateral resistance.
Main Methods:
- Coronary collateral resistance was estimated by measuring retrograde flow rate in the left anterior descending coronary artery.
- Constant pressure perfusion of the main left coronary artery was maintained.
- Retrograde flow was measured during normal cardiac cycles and during vagal arrest (prolonged diastole).
- Left ventricular end-diastolic pressure was manipulated by altering afterload and contractility.
Main Results:
- Systole, indicated by prolonged diastole during vagal arrest, had no significant effect on collateral resistance.
- A direct relationship was observed between altered left ventricular end-diastolic pressure and collateral resistance.
Conclusions:
- Coronary collateral vessels show minimal resistance changes during systole.
- Left ventricular end-diastolic pressure is a significant determinant of coronary collateral resistance.
Abstract:
We determined whether the coronary collateral vessels develop an increased resistance to blood flow during systole as does the cognate vascular bed. Collateral resistance was estimated by measuring retrograde flow rate from a distal branch of the left anterior descending coronary artery while the main left coronary artery was perfused at a constant pressure. Retrograde flow rate was measured before and during vagal arrest. We found that in 10 dogs the prolonged diastole experienced when the heart was stopped caused no significant change in the retrograde flow rate, which indicated that systole has little effect on the collateral resistance. However, when left ventricular end-diastolic pressure was altered by changing afterload or contractility, a direct relationship between end-diastolic pressure and collateral resistance was noted.