A 45-year-old man comes to the emergency department because of severe chest pain, diaphoresis, and palpitations. The patient dies two hours after the onset of his symptoms. Autopsy reveals 100% occlusion of the left anterior descending artery. At the time of the patient's death, light microscopy of the affected myocardium would most likely demonstrate which of the following?

Question

A 45-year-old man comes to the emergency department because of severe chest pain, diaphoresis, and palpitations.  The patient dies two hours after the onset of his symptoms.  Autopsy reveals 100% occlusion of the left anterior descending artery.  At the time of the patient's death, light microscopy of the affected myocardium would most likely demonstrate which of the following?

Quizplus · Accepted Answer

11ec160b_38da_13a5_9249_af595dc684b7_MD0001_00 The cause of death was most likely an acute myocardial infarction. In myocardial infarction, changes on light microscopy are usually not apparent until 4 hours after the onset of severe ischemia. Although a variable waviness of myofibrils at the border of the infarct (due to myofibril relaxation) might be observed before this, more definite signs of early coagulative necrosis, such as cytoplasmic eosinophilia and nuclear pyknosis, take at least 4 hours to develop. Other potentially lethal causes of chest pain, diaphoresis, and palpitations/tachycardia include aortic dissection and/or rupture, massive pulmonary embolism, and tension pneumothorax. The chest pain of aortic dissection is typically tearing in nature and often radiates to the back. Dyspnea is typically the most prominent symptom in the event of a pulmonary embolus or tension pneumothorax. (Choices A & B) Cytoplasmic hypereosinophilia on light microscopy is one of the earliest signs of coagulative necrosis of cardiac myocytes. It begins approximately 4 hours after the onset of lethal ischemia. Light microscopy may also reveal edema and punctate hemorrhages in infarcted myocardium starting also at about 4 hours after the ischemic event. (Choice C) An interstitial infiltrate of neutrophils around a zone of myocardial infarction is not seen until 1 to 3 days after the onset of severe ischemia. (Choice D) Extensive macrophage phagocytosis of the dead cells generally does not develop until at least 5 days after myocardial infarction, and is most prominent during post-infarction days 7 to 10. (Choice E) Fibrovascular granulation tissue with neovascularization generally begins to develop 7 days after myocardial infarction, and is most prominent on post-infarction days 10 to 14. (Choice F) Increased collagen deposition and decreased cellularity in a zone of infarcted myocardium is not generally evident until 2 weeks post-infarction. Fibrosis continues during weeks 2 to 8, producing a dense collagenous scar by two months post-infarction. Educational objective: After the onset of severe ischemia leading to myocardial infarction (MI), early signs of coagulative necrosis do not become apparent on light microscopy until 4 hours after the onset of MI.

A 45-Year-Old Man Comes to the Emergency Department Because of Severe