Coronary arteries

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Rim Halaby, M.D. [2]

Overview

The coronary arteries supply oxygenated blood to the heart muscle itself. Although blood fills the chambers of the heart, the muscle tissue of the heart, or myocardium, is so thick that it requires coronary blood vessels to deliver blood deep into it. There are two primary arteries supplying the heart, the left coronary artery and the right coronary artery. These two epicardial coronary arteries course along the surface of the heart and this is why they are called "epicardial" (on top of the heart) arteries. Smaller arteries dive deep into the heart muscle and are called subendocardial coronary arteries. The cardiac veins are the vessels that remove the deoxygenated blood from the heart muscle and return it to the right atrium.

Coronary Arteries

There are two main coronary arteries: the left coronary artery and the right coronary artery. Both of these arteries originate from the beginning (root) of the aorta, immediately above the aortic valve: The left coronary artery originates from the left aortic sinus, and the right coronary artery originates from the right aortic sinus.

Below is an image showing the coronary arteries:

Left Coronary Artery

• The left coronary artery arises from the left aortic sinus.
• It is shorter than the right coronary artery; however, it supplies a larger portion of the myocardium.
• The left coronary artery branches into:
  • Left anterior ascending LAD (also called anterior interventricular artery)
    • It supplies the anterior part of the left ventricle: anterolateral myocardium, apex, anterior interventricular septum, anterolateral papillary muscle.
  • Left circumflex LCX
    • It supplies the posterolateral side of the left ventricle.

Right Coronary Artery

• The right coronary artery branches into:
  • SA branch
    • It supplies the SA node.
  • Acute marginal artery
    • It supplies the right ventricular wall.
  • Posterior descending artery
    • It supplies the inferior wall, posterior interventricular septum and posteromedial papillary muscle.

Coronary Artery Dominance

• The dominance of coronary circulation is determined by the type of arteries that supply the posterior and inferior wall of the left ventricle.
• The artery that supplies the posterior descending artery (PDA) and the posterolateral artery (PLA) determines the coronary dominance.
  • Right-dominant circulation: The right coronary artery (RCA) supplies both these arteries.
  • Left-dominant circulation: The circumflex artery (CX), a branch of the left artery, supplies both these arteries.
  • Co-dominant circulation: The RCA supplies the PDA and the CX supplies the PLA.

• Approximately 60% of the general population are right-dominant, 25% are co-dominant, and 15% are left-dominant.

Blood Supply to the Papillary Muscles

• The papillary muscles tether the mitral valve (the valve between the left atrium and the left ventricle) and the tricuspid valve (the valve between the right atrium and the right ventricle) to the wall of the heart.
• If the papillary muscles are not functioning properly, the mitral valve leaks during contraction of the left ventricle and causes some of the blood to travel "in reverse", from the left ventricle to the left atrium, instead of forward to the aorta and the rest of the body.
• This leaking of blood to the left atrium is known as mitral regurgitation.

• The anterolateral papillary muscle:
  • It receives two blood supplies: the LAD and LCX.
  • It is therefore somewhat resistant to coronary ischemia (insufficiency of oxygen-rich blood).
• The posteromedial papillary muscle:
  • It is supplied only by the PDA.
  • This makes the posteromedial papillary muscle significantly more susceptible to ischemia.
• The clinical significance of the nature of blood supply to the papillary muscles is that a myocardial infarction involving the PDA is more likely to cause mitral regurgitation.

References

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