WBR0771

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 57 year old man is brought to the emergency department with acute substernal chest pain that radiates to his left shoulder, associated with nausea and diaphoresis. Following appropriate work-up, he is diagnosed with ST-segment elevation myocardial infarction (STEMI). He undergoes coronary revascularization and is discharged from the hospital the next day. A histopathological analysis of his heart will show which of the following findings on light microscopy 12 days after his STEMI?]]
Answer A	AnswerA::Contraction bands
Answer A Explanation	AnswerAExp::Contraction bands, necrotic changes, and neutrophil migration starts 12 hours after onset of myocardial infarction. Neutrophilic migration persists for a few days after onset.
Answer B	AnswerB::Normal pathological specimen
Answer B Explanation	AnswerBExp::A normal pathological specimen may be seen in 2 cases: Normally perfused heart or within very early stages (only 0-4 hours) post-MI.
Answer C	AnswerC::Necrotic cells and neutrophil migration
Answer C Explanation	AnswerCExp::Contraction bands, necrotic changes, and neutrophil migration starts 12 hours after onset of myocardial infarction. Neutrophilic migration persists for a few days after onset.
Answer D	AnswerD::Edema, hemorrhage, and wavy fibers
Answer D Explanation	AnswerDExp::Edema, hemorrhage, and wavy fibers are seen in early coagulative necrosis at the early stages (4-12 hours) of MI
Answer E	AnswerE::Macrophage infiltration and granulation tissue
Answer E Explanation	AnswerEExp::Macrophage infiltration and granulation tissue are seen starting 3 days post-MI and persist to approximately 15 days post-MI.
Right Answer	RightAnswer::E
Explanation	[[Explanation::Following a myocardial infarction, the heart undergoes gross and microscopic changes that are collectively referred to as the evolutionary process of MI. Very early after MI, within 0-4 hours, the heart undergoes no gross of microscopic changes. In contrast, the infarcted area shows dark mottling within 4-12 hours. Microscopically during that period, there is edema, coagulative necrosis, hemorrhage, and wavy fibers. Then 12 hours post-MI, neutrophilic infiltration begins and contraction bands appear due to repercussion injury. Necrotic changes are also seen during that time because cells release their necrotic material. One day post-MI, the infarcted area becomes hyperemic and coagulative necrosis becomes more extensive with more inflammatory changes and neutrophilic migration. These changes persist for 3 days. 3-15 days post-MI, the border of the infarcted area becomes hyperemic and shows a soft yellowish infarcted region on gross pathology, and macrophage infiltration followed by granulation tissue on light microscopy. Finally, the infarcted area turns grayish and a contracted scar is formed starting 2 weeks; these changes persist for several months post-MI. Educational Objective: 3-15 days post-MI, light microscopy of the heart shows infiltration of macrophages and formation of granulation tissue. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::evolution, WBRKeyword::myocardial infarction, WBRKeyword::MI, WBRKeyword::STEMI, WBRKeyword::chest, WBRKeyword::pain, WBRKeyword::neutrophil, WBRKeyword::neutrophilic, WBRKeyword::inflammation, WBRKeyword::infiltration, WBRKeyword::macrophage, WBRKeyword::granulation tissue, WBRKeyword::gross, WBRKeyword::section, WBRKeyword::light, WBRKeyword::microscopy, WBRKeyword::post-MI, WBRKeyword::post, WBRKeyword::change, WBRKeyword::changes
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