Arterial supply of heart; arise from ascending aorta just above aortic valve; run in subepicardial fat.

Origin

Posterior aortic sinus = non-coronary sinus

Right Coronary Artery (RCA)

Course: anterior aortic sinus → forwards between pulmonary trunk + right auricle → right AV groove → around inferior border → posterior AV groove towards crux → (right dominant) gives posterior interventricular artery

Branches:

Left Coronary Artery (LCA)

• Larger than RCA, short main trunk
• Course: left aortic sinus → between pulmonary trunk + left auricle → divides into anterior interventricular (LAD) + circumflex

LAD (anterior interventricular artery)

Most commonly occluded coronary artery = “widow maker”

Circumflex artery

Distribution

RCA: right atrium (most/all), right ventricle (greater part, except strip near anterior IV groove), LV (small inferior/posterior part), IVS posterior 1/3; SA node (60%), AV node (usual), AV bundle/branches largely

LCA: left atrium (most/all), LV (greater part), RV (narrow strip near anterior IV groove), IVS anterior 2/3; SA node (40%), bundle branches mainly via LAD septal branches

Conducting System Supply

RCA → SA + AV node; LAD → anterior 2/3 septum + bundle branches RCA occlusion → nodal arrhythmias; LAD occlusion → bundle branch block + large anterior MI

Coronary Dominance

• Defined by which artery gives posterior interventricular artery + reaches crux

Right dominance: RCA occlusion → inferior MI + AV block Left dominance: circumflex/LCA occlusion → larger LV territory, may affect AV node

Anastomoses

• At apex (anterior/posterior IV arteries), IVS (septal branches), AV grooves (terminal RCA/circumflex), small extracardiac channels (pericardial, bronchial, internal thoracic, phrenic)
• Functional end-arteries — sudden occlusion: insufficient collateral flow; gradual narrowing: collaterals may enlarge

Applied Anatomy

Angina Pectoris

Myocardial Infarction

Common Occlusion Sites

Referred Pain — cardiac afferents enter T1–T5 → referred to left precordium, left shoulder, medial left arm/forearm, neck, jaw, epigastrium

Intervention

Common grafts: left internal thoracic artery (esp. to LAD), great saphenous vein, radial artery

The coronary arteries are the arterial supply of the heart. They arise from the ascending aorta just above the aortic valve and run in the subepicardial fat on the surface of the heart.

Exam logic:

Origin → course → branches → distribution → dominance → conducting system → applied anatomy

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Origin

The remaining posterior aortic sinus is the non-coronary sinus.

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Right Coronary Artery

Course

The right coronary artery (RCA):

1. Arises from the anterior aortic sinus.
2. Passes forwards between the pulmonary trunk and right auricle.
3. Descends in the right atrioventricular groove.
4. Turns around the inferior border of the heart.
5. Runs in the posterior atrioventricular groove towards the crux.
6. In right dominant hearts, gives the posterior interventricular artery.

Branches

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Left Coronary Artery

The left coronary artery (LCA) is larger than the RCA but has a short main trunk.

Course

1. Arises from the left aortic sinus.
2. Passes between the pulmonary trunk and left auricle.
3. Divides into:
   • Anterior interventricular artery
   • Circumflex artery

Anterior Interventricular Artery / LAD

The anterior interventricular artery is also called the left anterior descending artery (LAD).

The LAD is the most commonly occluded coronary artery and is clinically called the widow maker.

Circumflex Artery

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Areas of Distribution

Right Coronary Artery

Left Coronary Artery

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Arterial Supply of Conducting System

Standard exam rule:

• RCA commonly supplies the SA node and AV node.
• LAD supplies the anterior two-thirds of the septum and bundle branches.
• Therefore RCA occlusion commonly causes nodal arrhythmias, while LAD occlusion commonly causes bundle branch block and large anterior MI.

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Coronary Dominance

Coronary dominance is determined by which artery gives the posterior interventricular artery and usually reaches the crux of the heart.

Clinical importance:

• In right dominance, RCA occlusion may cause inferior wall MI and AV block.
• In left dominance, circumflex/LCA occlusion can compromise a larger left ventricular territory and may affect the AV node.

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Coronary Anastomoses

Anatomical anastomoses exist between coronary arteries, especially:

• At apex between anterior and posterior interventricular arteries
• In interventricular septum between septal branches
• In atrioventricular grooves between terminal RCA and circumflex branches
• Through small extracardiac channels from pericardial, bronchial, internal thoracic, and phrenic vessels

Functional point:

• Coronary arteries are not absolute anatomical end-arteries.
• They are functional end-arteries because sudden occlusion does not allow enough collateral flow.
• Gradual narrowing may allow collateral channels to enlarge.

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Applied Anatomy

Angina Pectoris

Myocardial Infarction

MI results from sudden severe or complete occlusion of a coronary artery.

Common Sites of Occlusion

Referred Pain

Cardiac pain fibres enter spinal segments T1-T5. Pain is referred to areas supplied by the same segments:

• Left precordium
• Left shoulder
• Medial side of left arm and forearm
• Neck and jaw
• Epigastrium

Coronary Angiography and Intervention

Common grafts:

• Left internal thoracic / internal mammary artery, especially to LAD
• Great saphenous vein
• Radial artery

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