Why STEMI Can Affect the AV Node
Your understanding needs correction: STEMI is not an "occlusion of the left ventricle" but rather an occlusion of a coronary artery that supplies the left ventricle, and the AV node can be affected because it receives its blood supply from these same coronary arteries—specifically the right coronary artery in 90% of people. 1
Understanding the Anatomy
The key to understanding AV node involvement in STEMI lies in recognizing the blood supply:
- Most cases of STEMI are caused by occlusion of a major coronary artery due to atherosclerotic plaque disruption with superimposed thrombus formation 1
- The AV node receives its blood supply from the AV nodal artery (AVNA), which typically arises from the right coronary artery (RCA) in approximately 90% of individuals, and from the left circumflex artery (LCx) in the remaining 10% 2
- The coronary arteries supply the myocardium of the left ventricle, not the ventricle itself being "occluded" 1
How Inferior STEMI Affects the AV Node
When the RCA is occluded (causing inferior STEMI), the AV nodal artery can be simultaneously compromised, leading to AV node ischemia and conduction abnormalities:
- RCA occlusion produces ST elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL 3, 4
- Occlusion of atrial branches including the AVNA is significantly associated with early new-onset atrial fibrillation and conduction disturbances in STEMI patients 2
- The right bundle branch also receives blood supply from the left anterior descending artery, which explains why anterior STEMI with new right bundle branch block indicates critical proximal LAD occlusion and carries worse prognosis 5
Clinical Implications
The presence of AV conduction abnormalities in STEMI indicates more extensive ischemia beyond just ventricular myocardium:
- Inferior STEMI with AV block suggests RCA occlusion with involvement of the AV nodal artery 2
- This pattern requires the same urgent reperfusion therapy as any STEMI, with primary percutaneous coronary intervention being the treatment of choice 1
- Patients with conduction system involvement have higher in-hospital adverse events and mortality 2
Common Pitfall to Avoid
Do not conceptualize STEMI as "occlusion of the left ventricle"—this is anatomically incorrect. STEMI results from occlusion of coronary arteries (LAD, RCA, or LCx) that supply blood to the left ventricular myocardium and other cardiac structures including the conduction system 1. The AV node is affected because it shares the same arterial blood supply that is compromised during the coronary occlusion.