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Effects of perfluorochemical hemodilution on coronary blood flow distribution in dogs
J G Kingma1, J R Rouleau, J Magrina
1Quebec Heart Institute, Laval Hospital, Laval University, School of Medicine, Ste-Foy, Canada.
Insights
Perfluorocarbon (PFC) hemodilution enhances myocardial autoregulation, particularly in endocardial vessels. This improves oxygen transport to the heart muscle during low-pressure conditions.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Myocardial Autoregulation
Background:
- Perfluorocarbon (PFC) hemodilution is a technique used to increase oxygen-carrying capacity.
- Understanding its effects on coronary circulation is crucial for therapeutic applications.
Purpose of the Study:
- To investigate the impact of PFC hemodilution on the heart's ability to regulate its own blood flow (autoregulation).
- To assess changes in coronary pressure-flow relationships before and after PFC administration.
Main Methods:
- Studies were conducted on anesthetized dogs, examining circumflex coronary artery pressure-flow relations.
- Measurements were taken under conditions of maximal vasodilation and autoregulation, with and without PFC, and varying oxygen levels.
Main Results:
- PFC did not alter coronary conductance or zero-flow pressure during vasodilation.
- PFC shifted the lower pressure limit of autoregulation leftward, preserving endocardial blood flow.
- Endocardial blood flow was maintained at higher levels relative to epicardial flow with PFC.
Conclusions:
- PFC hemodilution enhances the autoregulatory capacity of myocardial vessels, especially in the endocardium.
- PFC improves endocardial oxygen transport during reduced coronary perfusion pressures, suggesting potential therapeutic benefits.
Abstract:
To determine the effect of perfluorocarbon (PFC) hemodilution on myocardial vessel capacity to autoregulate, circumflex coronary artery pressure-flow relations were studied in anesthetized dogs under three conditions: maximal vasodilatation before and after PFC; autoregulation before and after PFC with 100% oxygen supplemented with room air ventilation, and autoregulation with PFC hemodilution during either room air or 100% oxygen supplemented with room air ventilation. During coronary vasodilatation, PFC did not modify coronary conductance or zero-flow pressure. During autoregulation after PFC, the lower pressure limit of the autoregulatory pressure-flow relation was shifted leftward. This leftward shift occurred because endocardial blood flow was maintained at a lower coronary perfusion pressure with PFC while epicardial blood flow was unchanged. Endocardial blood flow was also preserved at 50% of control blood flow levels as evidenced by the higher endocardial-epicardial blood flow ratio with PFC. After PFC with 100% oxygen supplemented with room air ventilation, oxygen transport increased significantly when coronary perfusion pressure was below the lower pressure limit; the effect was most prominent in the endocardial tissue layer. Thus, PFC shifts the lower pressure limit to the left because of the increased ability of the endocardial vessel to autoregulate. Consequently, PFC can be considered a useful intervention for improving endocardial oxygen transport at low coronary perfusion pressures.