Arterial Supply of the Conducting System of the Heart
Overview
The conducting system of the heart is supplied predominantly by the right coronary artery (RCA). This is clinically important because occlusion of the RCA frequently causes arrhythmias.
Component-wise Supply
| Component | Primary Supply | Notes |
|---|---|---|
| SA node | RCA in ~60% | LCA (circumflex) in ~40% |
| AV node | RCA (almost always) | Supplied by the artery that crosses the crux — usually the RCA |
| AV bundle (Bundle of His) | RCA | Runs along the posteroinferior border of the membranous septum |
| Right branch of AV bundle | RCA | Runs down the right side of the interventricular septum |
| Left branch of AV bundle | RCA (mostly) + LCA (partly) | The posterior fascicle of the left branch is supplied by the LCA |
Key Rule
The whole of the conducting system is supplied by the RCA, except for a part of the left branch of the AV bundle, which receives supply from the left coronary artery.
Clinical Significance
- RCA occlusion → may affect SA node, AV node, and bundle branches → sinus bradycardia, heart block, or arrhythmias.
- LCA (LAD) occlusion → may affect the bundle branches (especially the left bundle branch) → bundle branch block.
- Because the left bundle branch has dual supply (RCA + LCA), isolated left bundle branch block is less common from a single-vessel occlusion than right bundle branch block.
- Vascular lesions of the coronary arteries are a common cause of cardiac arrhythmias.
Why the Conducting System is Vulnerable
The conducting system lies within the myocardium and receives its blood supply from small branches of the coronary arteries. Because coronary arteries are functionally end-arteries, sudden occlusion deprives the conduction tissue of all blood supply without time for collateral compensation.