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Left main coronary artery occlusion
9%
34/380
Right main coronary artery occlusion
38%
144/380
Left circumflex artery occlusion
14%
54/380
Left anterior descending artery occlusion
34%
128/380
Coronary vasospasm
1%
3/380
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The most likely diagnosis is an inferoposterior wall ST elevated myocardial infarction (STEMI) which is most likely caused by a right coronary artery occlusion. This patient’s presentation of substernal chest pain/pressure that radiates to the jaw and down the left arm is the classic presentation of a myocardial infarction in a man. His past medical and family histories support this diagnosis. EKG shows ST segment elevations on leads 2, 3, and aVF showing an infarction in the inferior wall. There are ST depressions in leads V1 – V4 which indicates there is involvement of the posterior aspect of the heart as well, as electrical current moves from away from those leads. The right coronary artery is the artery that supplies blood to the right ventricle, SA/AV nodes, and the posterior aspect of the heart via the posterior descending artery in around 70-80% of individuals (“right dominant heart”). Illustration A shows the same EKG as Figure A with annotations demonstrating the findings of ST segment elevations on leads 2, 3, and aVF and depressions in V1 - V4. Illustration B shows the anatomy of coronary vessel blood supply. Incorrect Answers Answer 1: Occlusion of the left main coronary artery leads to ischemia of the anterior and lateral walls of the heart. EKG would show ST elevations in leads 1, 2, aVL, and V1 – V6. Answer 3: Occlusion of the left circumflex artery leads to infarction of the lateral wall of the heart. EKG would show ST elevations in leads 1, aVL, and V5 – V6. Answer 4: Occlusion of the left anterior descending artery would lead to infarction of the anterior wall of the heart. EKG would show ST elevations in leads V1 – V4. Answer 5: Coronary vasospasm (vasospastic angina/ Prinzmetal angina) can present similarly to STEMIs as the myocardium becomes ischemic during episodes. Symptoms improve on their own as vasospasm stops. Vasospastic angina occurs more often in younger patients without a history of coronary artery disease. Given this patient’s history of diabetes, hypertension, and positive family history, STEMI is more likely than vasospastic angina. Bullet Summary: Inferoposterior wall STEMIs are due to a lack of blood flow through the posterior descending artery which is a branch of the right coronary artery in a majority of people. The right coronary artery also supplies blood to the SA/AV nodes. ST elevations in leads 2 and aVR combined with ST depression in leads V1 – V2 are suggestive of a posterior wall MI.
3.9
(17)
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