Scenario: A 71-year-old white woman with vague complaints of dyspnea while gardening. She is presenting within 4 hours of onset of symptoms to the emergency department and has an unremarkable medical history.

Interpretation: Normal sinus rhythm with inferior posterior ST-elevation myocardial infarction with apical extension.

The most common cause of ST-elevation myocardial infarction is a complete thombotic occlusion in a major coronary artery causing transmural injury. Striking ST-segment elevation is present in leads II, III, and aVF, all of which are inferior leads, suggesting that the right coronary artery is the infarct-related artery. Myocardial ischemia tends to be a regional event. When both ST-segment elevation and depression are observed on the 12-lead ECG, the ST elevation is usually considered primary and the ST depression changes are considered reciprocal. When the distal right coronary artery blood supply is inadequate, the posterior wall may become involved. Because there are no electrodes facing...

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