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The coronary circulation: quo vadis?
1Dalhousie University, Division of Cardiology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada. gklass@glinx.com
Insights
Understanding coronary circulation requires further study of its microcirculation and venous systems. New methods reveal independent regulation of oxygen delivery, impacting coronary artery disease understanding and future treatments.
Area of Science:
- Cardiovascular Physiology
- Medical Imaging
- Biomedical Engineering
Background:
- The coronary circulation's structure and function in health and disease are complex.
- Existing knowledge gaps exist in the coronary microcirculation and venous systems.
- Future research requires a deeper understanding for effective interventions.
Purpose of the Study:
- To review current understanding of coronary circulation.
- To identify areas needing further investigation, specifically the microcirculation and venous systems.
- To propose future research directions for improved understanding and treatment.
Main Methods:
- Review of past and present observations on coronary circulation.
- Presentation of data from laser Doppler velocimetry within the myocardium.
- Analysis of red cell flux and its relation to oxygen delivery.
Main Results:
- Tissue hematocrit and oxygen delivery can be independently regulated from epicardial arterial flow.
- Laser Doppler velocimetry provides continuous measurement of red cell flux.
- These findings have implications for understanding coronary artery disease pathophysiology.
Conclusions:
- Further study of the coronary microcirculation and venous circulation is crucial.
- Advanced measurement techniques are needed to pose the right questions for research.
- Improved knowledge of coronary circulatory dynamics is essential for developing new interventions for ischemic myocardium.
Abstract:
This review examines past and present observations concerning the structure and function of the coronary circulation in health and disease. These observations are considered in the context of how we might proceed to increase understanding of this circulation in the future. The coronary microcirculation with its intimate relationship of capillaries and myocytes and the coronary venous circulation are identified as parts of the coronary circulation in need of further study. Observations using a laser Doppler velocimeter placed within the beating myocardium are presented. Such devices measure the velocity of red cells continuously (red cell flux) and can demonstrate that tissue hematocrit and hence oxygen delivery can be regulated independently of total epicardial arterial volume flow. Implications for the understanding of the pathophysiology of coronary artery disease are presented. As considerations are given to molecular genetic techniques to revascularize the ischemic myocardium we will require a more complete knowledge of coronary circulatory dynamics, myocardial support tissues' responses, and cardiac myocyte interactions to design appropriate interventions. The clinical trial is an appropriate clinical tool to measure effectiveness but a blunt instrument to determine pathophysiology. The purpose of the review is to suggest that advances in measurement of end points are required to permit the right question to be posed.