M01.05.019 Vasculature of the Heart

The circulatory system ensures that the entire body, including the heart, is supplied with oxygen and nutrients. Coronary circulation specifically refers to the blood vessels that supply and drain the heart. The coronary arteries encircle the heart, resembling a crown, and are essential for cardiac function.

This article provides an overview of the coronary arteries, their distribution, and clinical relevance for medical students.

1. Coronary Arteries

The coronary arteries supply the heart muscle with oxygen-rich blood. There are two main coronary arteries that arise from the aorta: the left coronary artery (LCA) and the right coronary artery (RCA).

Naming and Branches of the Coronary Arteries

Left Coronary Artery (LCA)

• Origin: Arises from the left aortic sinus.
• Branches:
  • Left Anterior Descending (LAD) artery: Also called the anterior interventricular artery, it supplies the anterior part of the heart.
  • Left Circumflex (Cx) artery: Circles the left border of the heart, supplying the left atrium and left ventricle.
  • Left Marginal Artery (LMA): A branch of the circumflex artery, it supplies the left ventricle.
  • In about 20-25% of individuals, the circumflex artery contributes to the Posterior Interventricular (PIv) artery.

Right Coronary Artery (RCA)

• Origin: Arises from the right aortic sinus.
• Branches:
  • Right Marginal Artery (RMA): Supplies the right ventricle.
  • Posterior Interventricular Artery (PIv): In 80-85% of individuals, this artery arises from the RCA and supplies the posterior part of the heart.

Key Points

• Aortic Sinuses: Small openings in the aorta behind the aortic valve where the coronary arteries arise.
• The coronary arteries are named due to their circular pattern around the heart, resembling a crown.

2. Cardiac Venous Drainage

The heart’s venous drainage is primarily through the coronary sinus, which empties into the right atrium. The venous blood is drained by several cardiac veins.

Main Cardiac Veins

• Great Cardiac Vein: Drains the anterior heart and runs in the anterior interventricular groove.
• Small Cardiac Vein: Located along the right border of the heart and drains into the coronary sinus.
• Middle Cardiac Vein: Drains the posterior part of the heart and ascends in the posterior interventricular groove.
• Posterior Cardiac Vein: Drains the left ventricle and empties into the coronary sinus.

3. Distribution of the Coronary Arteries

Each coronary artery supplies specific regions of the heart, with the areas of perfusion largely corresponding to the paths of the arteries.

Coronary Artery Distribution

4. Clinical Relevance

Coronary Artery Disease (CAD)

Coronary artery disease (CAD) is a leading cause of morbidity and mortality globally. It results from the narrowing or blockage of coronary arteries, leading to reduced blood flow to the myocardium.

Causes of CAD

• Atherosclerosis: Fatty plaque buildup in the arteries.
• Thrombosis: Blood clots obstructing the arteries.
• Hypertension: High blood pressure causing vessel damage.
• Diabetes and Smoking: Both contribute to vascular damage.

Consequences of CAD

• Angina Pectoris: Chest pain due to lack of oxygen in the heart during exertion, resolved by rest.
• Myocardial Infarction (MI): Heart attack caused by complete occlusion of a coronary artery, leading to necrosis of the myocardium.

Myocardial Infarction and ECG

Different parts of the heart can be affected depending on which artery is occluded. Changes in specific ECG leads help locate the site of the occlusion.

5. Diagnosis and Treatment of CAD

Diagnosis

• Coronary Angiography: A catheter is inserted into the aorta, and a contrast dye is used to visualize blockages in coronary arteries.

Treatment

• Coronary Angioplasty: A balloon is inflated within the blocked artery to restore blood flow. A stent may be placed to maintain artery patency.

Points to Remember

• The heart is supplied by the left and right coronary arteries.
• The coronary arteries encircle the heart and are named for their crown-like distribution.
• Venous drainage primarily occurs via the coronary sinus, which empties into the right atrium.
• Coronary artery disease can result in angina pectoris and myocardial infarction.
• ECG changes can help pinpoint the location of a coronary artery blockage.
• Coronary angiography and angioplasty are key diagnostic and treatment tools for CAD.