## SA Node Blood Supply **Key Point:** The sinoatrial (SA) node is supplied by the SA nodal artery, which arises from the right coronary artery (RCA) in approximately 60% of individuals and from the left circumflex artery in 40%. ### Arterial Supply Pattern **High-Yield:** In the majority (60%) of the population, the SA nodal artery is a branch of the right coronary artery. This is the most commonly tested fact about SA node blood supply in NEET PG. ### Anatomical Course The SA nodal artery: 1. Originates from the proximal right coronary artery 2. Courses posteriorly around the junction of the superior vena cava and right atrium 3. Penetrates the atrial wall to supply the SA node 4. May anastomose with branches from the left circumflex artery ### Clinical Significance **Clinical Pearl:** Occlusion of the right coronary artery can lead to SA node ischemia, resulting in sinus bradycardia, sinus arrest, or sinoatrial block. This is particularly important in inferior wall myocardial infarction. ### Coronary Artery Supply to Conduction System | Structure | Primary Supply | Secondary Supply | Frequency | |-----------|----------------|------------------|----------| | SA node | Right coronary artery | Left circumflex | 60% RCA, 40% LCx | | AV node | Right coronary artery | Left circumflex | 90% RCA | | Bundle of His | LAD and RCA | — | Dual supply | | Right bundle branch | LAD | — | — | | Left bundle branch | LAD | — | — | **Mnemonic:** **RCA Rules the Node** — Right Coronary Artery supplies the SA node in the majority of cases and almost always supplies the AV node. [cite:Clinically Oriented Anatomy 8e Ch 1] 
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