Review Question - QID 104059

This patient with chest pain and an ECG demonstrating ST segment elevation in leads I and aVL likely had an acute myocardial infarction. The most likely cause of death within hours of symptoms onset is a ventricular arrhythmia, often ventricular fibrillation.

ST segment elevation myocardial infarction (STEMI) occurs most commonly due to atherosclerotic plaque rupture resulting in complete occlusion of a coronary artery. As a result, myocardial tissue supplied by the artery becomes ischemic, and will eventually become necrotic if perfusion is not reestablished. Patients with acute myocardial infarction are at risk for a number of complications. In the first several hours after myocardial tissue becomes ischemic, ventricular arrhythmias may arise as ventricular tissue becomes infarcted. Mechanical complications, such as ventricular septal rupture, papillary muscle rupture and mitral regurgitation, and pericarditis, generally do not occur until days to weeks later as myocardial tissue becomes necrotic and structurally weaker.

Weiss et. al review ventricular arrhythmias in ischemic heart disease. They discuss the pathophysiology behind the development of ventricular arrhythmia such as ventricular tachycardia and ventricular fibrillation in the setting of myocardial ischemia. They note ventricular arrhythmia as a leading cause of death in patients with acute myocardial infarction.

Figure A shows an ECG with ST segment elevation in leads I and aVL, and reciprocal ST segment depression in the precordial leads. This is typical of a lateral wall infarction, often with a culprit lesion in the left circumflex artery.

Incorrect Answers:
Answer 1: Cardiac tamponade may develop secondary to ventricular free wall rupture after myocardial infarction. This typically occurs several days to weeks after myocardial infarction.

Answer 2: Chordae tendineae rupture may develop secondary to myocardial infarction as papillary muscles become necrotic, resulting in mitral regurgitation. This typically occurs several days after myocardial infarction.

Answer 3: Heart block may occur secondary to myocardial infarction. It is more common with inferior wall infarctions. This patient's lateral wall infarction is less likely to cause heart block.

Answer 5: Ventricular septum rupture may occur after myocardial infarction as the septal myocardium becomes necrotic. This typically occurs several days to weeks after myocardial infarction.

Bullet Summary:
In the first several hours after myocardial infarction, ventricular arrhythmias are a common complication that may lead to death.