A 58-year-old man presents to the emergency department with acute-onset substernal crushing chest pain radiating to the left arm and jaw, accompanied by diaphoresis and dyspnea. A 12-lead ECG is obtained within 8 minutes of arrival and shows ST-segment elevation in leads V1–V6, I, and aVL, with reciprocal ST-segment depression in leads II, III, and aVF. The pattern marked **A** in the diagram is consistent with acute anterolateral STEMI. Which of the following coronary artery lesions is the most likely culprit?
A. Right coronary artery occlusion proximal to the acute marginal branch
B. Proximal left anterior descending (LAD) artery with wraparound distal segment occluding before the first diagonal and first septal perforator
C. Left main coronary artery stenosis with preserved distal flow
D. Left circumflex artery occlusion at the level of the obtuse marginal branch
Explanation
Why "Proximal left anterior descending (LAD) artery with wraparound distal segment occluding before the first diagonal and first septal perforator" is right
Anterolateral STEMI, as marked A, results from acute occlusion of a "wraparound" LAD coronary artery—one whose distal segment courses around the cardiac apex to supply the anterior septum, lateral wall, and a portion of the inferior wall. Occlusion proximal to the first diagonal and first septal perforator produces transmural ischemia of the anterior wall, septum, and apical-lateral myocardium. This manifests on the 12-lead ECG as ST-segment elevation in precordial leads V1–V6 (anterior wall) plus high lateral leads I and aVL (lateral wall), with characteristic reciprocal ST-segment depression in inferior leads II, III, and aVF—exactly the pattern described in this case. The presence of ST elevation in BOTH precordial AND high-lateral leads with reciprocal inferior depression localizes the culprit lesion to the proximal LAD before the first diagonal/first septal perforator (Braunwald Heart Disease 12e, Ch 56).
Why each distractor is wrong
Left circumflex artery occlusion at the level of the obtuse marginal branch: Circumflex occlusion produces lateral STEMI only (ST elevation in I, aVL, V5–V6) without precordial ST elevation in V1–V4 and without reciprocal inferior depression. The presence of precordial elevation rules out isolated circumflex disease.
Right coronary artery occlusion proximal to the acute marginal branch: RCA occlusion produces inferior STEMI with ST elevation in II, III, aVF and reciprocal depression in I and aVL—the opposite of the pattern seen here. There would be no precordial ST elevation in V1–V6.
Left main coronary artery stenosis with preserved distal flow: Left main stenosis typically produces global ischemia with ST elevation in most leads and profound hemodynamic collapse. The selective pattern of ST elevation in anterolateral leads with reciprocal inferior depression is not typical of left main disease and would not explain the anatomically localized infarct territory.
High-YieldNEET PG
Anterolateral STEMI = wraparound LAD occlusion proximal to first diagonal; ST elevation in V1–V6 + I + aVL + reciprocal depression in II, III, aVF = worst prognosis (largest infarct size, highest cardiogenic shock and mechanical complication rates).
Braunwald Heart Disease 12e, Ch 56
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