Q. A 50 year old man presents with severe crushing chest pain radiating to left arm. His ECG showed dominant R waves in V1 and V2 leads. The T waves were upright and tall along with ST segment depressions. Which artery is most likely to be occluded? A. Right coronary artery B. Septal branch of left anterior descending artery C. Circumflex artery D. Left main coronary artery Answer: C. Circumflex artery Explanation: The ECG changes are suggestive of posterior wall MI. Posterior myocardial infarction usually results from occlusion of the left circumflex coronary artery but the anatomy can vary a little. Occlusion of the right coronary artery may also result in a posterior MI. The changes of posterior myocardial infarction are seen indirectly in the anterior precordial leads. Leads V1 to V3 face the endocardial surface of the posterior wall of the left ventricle. As these leads record from the opposite side of the heart instead of directly over the
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