]> 2026-07-31T09:41:02+00:00 WBR0771 0 en Formation of contraction bands Contraction bands, necrotic changes, and neutrophil migration starts 12 hours following the onset of myocardial infarction. Neutrophilic migration persists for a few days. Normal pathological specimen A normal pathological specimen may be observed in 2 cases: Either in a normally perfused myocardium or within very early stages (0 to 4 hours) post-MI. Necrotic cells and neutrophil migration Contraction bands, necrotic changes, and neutrophil migration starts 12 hours following the onset of myocardial infarction. Neutrophilic migration persists for a few days. Edema, hemorrhage, and formation of wavy fibers Edema, hemorrhage, and presence of wavy fibers on microscopy are all observed in early coagulative myocardial necrosis during the early stages (4 to 12 hours) post-MI Macrophage infiltration and formation of granulation tissue Macrophage infiltration and granulation tissue are observed starting 3 days post-MI. These findings persist to approximately 15 days post-MI. Following a myocardial infarction, the heart undergoes gross and microscopic changes that are collectively referred to as the evolutionary process of MI:<br> *0 to 4 hours post-MI: Very early following MI, the heart undergoes no gross or microscopic changes.<br> *4 to 12 hours post-MI: The infarcted area starts to demonstrate dark mottling. During that period also, there is edema, coagulative necrosis, and hemorrhage. Wavy fibers are observed microscopically.<br> *12 hours post-MI: Neutrophilic infiltration begins and contraction bands appear, signaling reperfusion injury. Necrotic changes are also observed during that time because cells release their necrotic material.<br> *1 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.<br> *3 to 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 is evident on light microscopy.<br> *2 weeks post-MI: The infarcted area turns grayish and a contracted scar is formed. These changes persist for several months post-MI.<br/> '''Educational Objective:''' At 3 to 15 days post-MI, light microscopy of the heart typically shows infiltration of macrophages and formation of granulation tissue.<br/> '''References:''' Pathology A 57-year-old man is brought to the emergency department with acute-onset substernal chest pain for the past 2 hours. He explains that his pain radiates to his left shoulder and is 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 this patient's myocardium will show which of the following findings on light microscopy 12 days following his STEMI? E Cardiology 2020-10-28T01:39:06Z 2459150.5688194 WBR0771