The sinoatrial (SA) node receives its blood supply primarily from which coronary artery?

Explanation

## Blood Supply to the SA Node **Key Point:** The 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%. ### SA Nodal Artery Origin | Artery | Frequency | Clinical Note | |--------|-----------|---------------| | **Right coronary artery (RCA)** | ~60% | Most common origin | | Left circumflex artery (LCx) | ~40% | Dominant in some individuals | | Left anterior descending (LAD) | Rare | Unusual variant | **High-Yield:** Although the SA node has variable blood supply, the **right coronary artery is the predominant source** in the majority of the population. This is the answer expected in NEET PG exams. **Clinical Pearl:** Occlusion of the RCA can lead to SA node ischemia, causing sinus bradycardia, sinus arrest, or sick sinus syndrome. This is particularly relevant in inferior wall myocardial infarction (IWMI), where RCA occlusion is common. ### Conducting System Blood Supply Summary ```mermaid flowchart TD A[Coronary Arteries]:::action --> B[SA Node]:::outcome A --> C[AV Node]:::outcome A --> D[Bundle of His]:::outcome B -->|RCA 60%| E[Right Coronary Artery]:::action B -->|LCx 40%| F[Left Circumflex]:::action C -->|AV nodal artery| G[RCA or LCx]:::action D -->|Septal perforators| H[LAD or RCA]:::action ``` **Mnemonic:** **RCA-SA** = Right Coronary Artery supplies the SA node (in most people).