M01.05.019 Vasculature of the Heart

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Learning Objective

Describe the origin, branches, distribution, venous drainage, and clinical relevance of the coronary circulation.

The entire body must be supplied with oxygen and nutrients via the circulatory system, and the heart is no exception. The coronary circulation refers to the vessels that supply and drain the heart. The coronary arteries encircle the heart like a crown.

Naming: Coronary Arteries

There are two main arteries: the Left Coronary Artery (LCA) and the Right Coronary Artery (RCA). They arise from the left and right aortic sinuses of the ascending aorta. The aortic sinuses are dilatations located behind the cusps of the aortic valve. During diastole, backflow of blood fills these sinuses, allowing coronary perfusion.

Branches of the LCA:

Left anterior descending (LAD) – also called the anterior interventricular artery
Left marginal artery (LMA)
Left circumflex artery (Cx)
In 20–25%, the circumflex contributes to the posterior interventricular artery (PIv)

Branches of the RCA:

Right marginal artery (RMA)
In 80–85%, gives rise to the posterior interventricular artery (PIv)

Cardiac Veins

Venous drainage occurs mainly via the coronary sinus, located on the posterior aspect of the heart It drains into the right atrium. Main tributaries of the coronary sinus:

Great cardiac vein (anterior interventricular vein)
Small cardiac vein
Middle cardiac vein (posterior interventricular vein)
Posterior cardiac vein

Activity

Distribution of the Coronary Arteries

In general, the region over which an artery travels corresponds to the myocardium it perfuses.

Course of the RCA:

Runs in the coronary sulcus
Gives off the right marginal artery
Forms the posterior interventricular artery (in most individuals)

Course of the LCA:

Divides into the LAD and Circumflex
LAD runs in the anterior interventricular groove
Circumflex runs in the coronary sulcus

Activity

Clinical Relevance

Coronary Artery Disease (CHD)

Coronary artery disease is caused by reduced myocardial blood flow due to the narrowing or blockage of the coronary arteries. Common causes include atherosclerosis, thrombosis, hypertension, diabetes, and smoking.

Angina Pectoris

Angina is transient chest pain due to myocardial ischaemia during exertion. During exercise, diastole shortens, reducing coronary perfusion time.

Myocardial Infarction (MI)

Complete occlusion of a coronary artery leads to myocardial infarction and necrosis.

ECG localisation (High Yield):

Inferior MI – II, III, aVF → RCA
Anteroseptal MI – V1, V2 → LAD
Anterolateral MI – I, aVL, V5–V6 → Circumflex

Diagnosis and Treatment

A coronary angiogram visualises arterial narrowing using contrast dye. Treatment includes coronary angioplasty with balloon dilation and stent placement.