## Site of AV Block in Acute Anterior MI ### Anatomical Basis In acute anterior wall MI, the left anterior descending (LAD) artery is occluded. The LAD supplies the **bundle of His** and the proximal bundle branches directly, making this region the most common site of conduction block in anterior infarction. ### Comparison: Anterior vs. Inferior MI | Feature | Anterior MI | Inferior MI | | --- | --- | --- | | **Vessel occluded** | LAD | RCA (usually) | | **Most common AV block site** | Bundle of His / proximal bundle branches | AV node | | **Type of block** | Infranodal (often complete, abrupt onset) | Nodal (often transient, gradual) | | **Prognosis** | Worse (broad QRS escape rhythm) | Better (narrow QRS escape rhythm) | | **Pacing requirement** | Often needed | Rarely needed | ### Key Point: **Bundle of His is the most common site of AV block in anterior MI** because it lies in the territory of the LAD. This results in infranodal block with a wide QRS escape rhythm and poor prognosis. ### Clinical Pearl: In contrast, **AV nodal block is most common in inferior MI** because the AV node is supplied by the AV nodal artery (branch of RCA in ~90% of people). Inferior MI blocks are usually transient and have better outcomes. ### High-Yield: When you see "anterior MI + complete heart block," think **bundle of His** as the site. When you see "inferior MI + AV block," think **AV node**. This distinction is crucial for prognosis and management decisions.
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