A 51-year-old man is brought to the emergency department due to chest tightness that started 30 minutes prior to arrival. His chest discomfort is associated with shortness of breath and nausea. The patient was shoveling snow off his driveway when his symptoms began. He has a history of hypertension and type 2 diabetes mellitus. Initial ECG shows ST elevation in leads I and aVL. Cardiac enzymes are elevated. Emergent cardiac catheterization in this patient will most likely show occlusion of which of the following arteries?

Question

A 51-year-old man is brought to the emergency department due to chest tightness that started 30 minutes prior to arrival.  His chest discomfort is associated with shortness of breath and nausea.  The patient was shoveling snow off his driveway when his symptoms began.  He has a history of hypertension and type 2 diabetes mellitus.  Initial ECG shows ST elevation in leads I and aVL.  Cardiac enzymes are elevated.  Emergent cardiac catheterization in this patient will most likely show occlusion of which of the following arteries?

Quizplus · Accepted Answer

11ec160b_355b_c2d9_9249_61a98c8fd2fd_MD0001_00 This patient with ST elevations in leads I and aVL most likely has an acute lateral myocardial infarction (MI) due to occlusion of the left circumflex artery. ECGs are useful in the diagnosis of MI and may help localize the area of infarction. ST elevations typically represent acute MI, whereas prominent Q waves are suggestive of old MI. Leads I and aVL correspond to the lateral limb leads on ECG; therefore, ST elevation or Q waves in these leads are indicative of infarction involving the lateral aspect of the left ventricle. Because the chest leads V5-V6 are also laterally placed, they may also show ST elevation during a lateral infarction. The lateral aspect of the left ventricle is supplied by the left circumflex artery, which originates from the left main coronary artery. (Choices A and D) The left anterior descending artery (LAD) primarily supplies the anterior aspect of the left ventricle and interventricular septum (septal branches), which corresponds to the anterior chest leads (V1-V4). Proximal occlusion of the LAD may involve all of these leads; however, distal LAD occlusion typically spares the septal leads (V1-V2). (Choice C) The left main coronary artery gives rise to the LAD and left circumflex arteries. Therefore, left main coronary artery occlusion typically results in anterolateral infarction, which corresponds to ST elevation in the anterior (eg, V1-V4) and lateral (V5-V6, I, and aVL) leads. (Choice E) The right coronary artery typically supplies the right ventricle and inferior aspect of the left ventricle. Occlusion of this vessel therefore results in inferior MI, which corresponds to ST elevation in the inferior leads (II, III, and aVF). Educational objective: Leads I and aVL correspond to the lateral limb leads on ECG. Therefore, ST elevation or Q waves in these leads are indicative of infarction involving the lateral aspect of the left ventricle, which is supplied by the left circumflex artery. __________ References: The electrocardiogram in ST elevation acute myocardial infarction: correlation with coronary anatomy and prognosis. (http://www.ncbi.nlm.nih.gov/pubmed/13679544) Electrocardiographic localization of coronary artery narrowings: studies during myocardial ischemia and infarction in patients with one-vessel disease. (http://www.ncbi.nlm.nih.gov/pubmed/7139896)

A 51-Year-Old Man Is Brought to the Emergency Department Due