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Peripheral embolization provides evidence for microvascular collaterals in hearts with chronic coronary artery
H F Downey1, H Murakami, S J Kim
1Department of Physiology, Texas College of Osteopathic Medicine, Fort Worth 76107.
Insights
Microscopic coronary collateral vessels, smaller than 84 microns, significantly perfuse heart muscle in dogs with chronic artery blockages. Larger emboli were dislodged, indicating the functional importance of these smaller vessels.
Area of Science:
- Cardiovascular Research
- Coronary Artery Disease
- Myocardial Perfusion
Background:
- Macroscopic coronary collateral vessels are considered the main blood source for collateral-dependent myocardium.
- The functional significance of microscopic coronary collateral vessels remains controversial.
Purpose of the Study:
- To investigate the functional significance of microscopic coronary collateral vessels in myocardial perfusion.
- To determine the contribution of different-sized collateral vessels to blood flow in chronically occluded coronary arteries.
Main Methods:
- Experiments were conducted on 18 anesthetized dogs with chronic coronary artery occlusions.
- Retrograde flow was measured before and after embolization with 13-micron or 84-micron spheres.
- Antegrade flow was assessed after retrograde flow diversion.
Main Results:
- Embolization with 13-micron spheres increased retrograde flow by 43%.
- Embolization with 84-micron spheres had no effect on retrograde flow and spheres were found in retrograde flow.
- Antegrade flow increased by 250% after retrograde flow diversion, dislodging 84-micron spheres.
Conclusions:
- Collateral vessels less than 84 microns in diameter significantly contribute to the perfusion of chronically collateral-dependent myocardium.
- Microscopic coronary collateral vessels play a crucial functional role in maintaining myocardial blood supply.
Abstract:
Macroscopic collateral vessels are widely regarded as the primary source of blood flow to collateral-dependent myocardium. Microscopic coronary collateral vessels have also been described, but their functional significance is controversial. Experiments were conducted in 18 anesthetized dogs with chronic coronary artery occlusions. Indices of collateral function demonstrated that all hearts were well-collateralized. The previously occluded coronary artery was cannulated distal to the obstruction for measuring retrograde flow before and after injection of either 13 microns or 84 microns emboli. Mean arterial pressure and heart rate were not altered by coronary embolization. Embolization with 13 micron spheres caused retrograde flow to increase by 43% (n = 11), whereas embolization with 84 micron spheres had no effect on retrograde flow (n = 7). Retrograde flow dislodged occlusive 84 micron spheres, since these spheres were found in the retrograde flow, and since antegrade flow increased by 250% after retrograde flow diversion. These findings demonstrate that collateral vessels less than 84 micron diameter contribute significantly to perfusion of chronically collateral-dependent myocardium.