Anatomy - Occlusion in the left main coronary artery

An occlusion at the left main coronary artery before its bifurcation results in ischemia in both the LAD and RCx distributions. The ischemia vector points to the right and superiorly predominantly in the direction of the positive pole of aVR. Consequently, the amplitude of ST elevation is greatest in lead aVR. Also this occlusion results in:

  • ST elevation in V1 (less in amplitude than the ST elevation in aVR)
  • ST depression in leads II, III, and aVF (reciprocal ST depression as a result of ischemia of the heart base)
  • ST depression in precordial leads V3-V6, greatest in V4 (reciprocal ST depression as a result of posterior wall ischemia).

In some cases, right bundle branch block or bifascicular block may be seen due to ischemia of the conduction system.

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