Vignette: A 60-year-old man is brought to the emergency department with severe chest pain that started an hour ago. His medical history is significant for hypertension and hyperlipidemia. An electrocardiogram (ECG) shows ST-segment elevation in leads II, III, and aVF. He is diagnosed with acute myocardial infarction and treated immediately. Which of the following pathophysiologic processes is most likely responsible for the ST-segment elevation seen in this patient's ECG?
A) Decreased potassium efflux from myocardial cells
B) Increased calcium influx into myocardial cells
C) Increased sodium influx into myocardial cells
D) Transmural ischemia of the myocardium
E) Ventricular hypertrophy
D) Transmural ischemia of the myocardium
This patient's presentation of severe chest pain and ST-segment elevation in leads II, III, and aVF is characteristic of an acute inferior wall myocardial infarction, which is typically caused by occlusion of the right coronary artery. ST-segment elevation on ECG is indicative of transmural ischemia, a process in which the entire thickness of the myocardial wall is deprived of oxygen due to occlusion of a coronary artery. This severe and extensive ischemia alters the electrical properties of the myocardial cells, leading to changes in repolarization that manifest as ST-segment elevation on ECG. The other options listed do not directly cause ST-segment elevation.
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