Coronary Circulation and Myocardial Supply
Coronary circulation and myocardial supply describes how the heart feeds itself. The right and left coronary arteries arise from the aortic root and branch over the heart's surface and into the muscle, and their flow is continuously adjusted so that oxygen delivery matches the high and varying metabolic demand of the working myocardium.
Definition
Coronary circulation and myocardial supply refers to the arterial supply, venous drainage, and regulation of blood flow to the heart muscle that maintains the balance between myocardial oxygen demand and delivery.
Scope
The topic covers the anatomy of the coronary arteries and veins, the unusual timing of coronary flow within the cardiac cycle, the matching of supply to myocardial oxygen demand, autoregulation, and metabolic and endothelial control of coronary tone. It is descriptive physiology and does not provide guidance on ischemic heart disease.
Core questions
- How are the coronary arteries arranged and what regions do they supply?
- Why does most left-ventricular coronary flow occur during diastole?
- How is coronary flow matched to myocardial oxygen demand?
- What mechanisms autoregulate coronary blood flow?
Key concepts
- Right and left coronary arteries and their branches
- Coronary dominance
- Diastolic timing of coronary flow
- Myocardial oxygen demand and supply
- Coronary autoregulation
- Metabolic and endothelial control of coronary tone
Mechanisms
The left main coronary artery divides into the left anterior descending and circumflex branches, while the right coronary artery supplies the right heart and, in most people, the inferior wall and posterior descending artery (right dominance). Because contraction compresses the intramural vessels, perfusion of the left ventricle occurs predominantly during diastole. The myocardium extracts a high fraction of oxygen at rest, so increased demand must be met chiefly by raising flow. Local metabolic signals, endothelial mediators, and autoregulatory adjustment of arteriolar tone keep flow matched to demand across a range of perfusion pressures (Duncker & Bache, 2008).
Clinical relevance
The distribution of the coronary arteries and the supply-demand balance are the reference concepts behind understanding myocardial ischemia and the territory affected by a given vessel. This topic describes the normal coronary circulation and is educational; it does not provide diagnosis or treatment recommendations.
Evidence & guidelines
Coronary physiology is grounded in comprehensive reviews of coronary flow regulation (Duncker & Bache, 2008) and standard cardiovascular physiology texts (Katz, 2010; Klabunde, 2011). This topic summarizes normal physiology and is not a clinical guideline.
History
The pattern of the coronary vessels has been described since early anatomical study, but the modern physiology of coronary flow — its diastolic timing, its tight coupling to oxygen demand, and the mechanisms of autoregulation — was elucidated through twentieth-century experimental work and synthesized in detailed reviews of coronary regulation.
Key figures
- Dirk J. Duncker
- Robert J. Bache
- Carl J. Wiggers
Related topics
Seminal works
- duncker-bache-2008
Frequently asked questions
- Why does coronary flow to the left ventricle occur mainly in diastole?
- During systole, contraction of the left-ventricular wall compresses the vessels running through it and limits flow, so most left-ventricular perfusion happens in diastole when the muscle relaxes.
- What is coronary dominance?
- Coronary dominance refers to which artery gives rise to the posterior descending artery; in most people the right coronary artery does, which is termed right dominance.