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Myocardial infarction (MI) occurs when blood flow to a part of the heart muscle is blocked, leading to tissue damage. The progression of MI can be categorized by time, gross findings, microscopic findings, and potential complications.
Time (Post-Infarction) | Gross Findings | Light Microscopy | Complications |
---|---|---|---|
0-24 hours | Dark mottling, occluded artery | Early coagulative necrosis, edema, hemorrhage, wavy fibers | Reperfusion injury (free radicals, increased Ca2+ influx) leading to hypercontraction of myofibrils (dark eosinophilic stripes) Ventricular arrhythmia, heart failure (HF), cardiogenic shock |
1-3 days | Hyperemia | Extensive coagulative necrosis, neutrophil infiltration | Postinfarction fibrinous pericarditis |
3-14 days | Hyperemic border, central yellow-brown softening | Macrophages, granulation tissue at margins | Free wall rupture (leading to tamponade), papillary muscle rupture (mitral regurgitation), interventricular septal rupture (left-to-right shunt) LV pseudoaneurysm (risk of rupture) |
2 weeks to several months | Recanalized artery, gray-white scar | Contracted scar | Dressler syndrome, heart failure, arrhythmias, true ventricular aneurysm (risk of mural thrombus) |