22 - morphological changes in myocardial infarction

Evolution of Morphologic Changes in Myocardial Infarction

Time	Gross Features	Light Microscopic Findings
0-½ hr	None	None
½-4hr	None	Usually none; variable waviness of fibers at border
4-12hr	Occasionally dark mottling	Beginning coagulation necrosis; edema; hemorrhage
12-24hr	Dark mottling	Ongoing coagulation necrosis; pyknosis of nuclei; myocyte hypereosinophilia; marginal contraction band necrosis; beginning neutrophilic infiltrate
1-3 days	Mottling with yellow-tan infarct center	Coagulation necrosis, with loss of nuclei and striations; interstitial infiltrate of neutrophils
3-7 days	Hyperemic border; central yellow-tan softening	Beginning disintegration of dead myofibers, with dying neutrophils; early phagocytosis of dead cells by macrophages at infarct border
7-10 days	Maximally yellow-tan and soft, with depressed red-tan margins	Well-developed phagocytosis of dead cells; early formation of fibrovascular granulation tissue at margins
10-14 days	Red-gray depressed infarct borders	Well-established granulation tissue with new blood vessels and collagen deposition
2-8wk	Gray-white scar, progressive from border toward core of infarct	Increased collagen deposition, with decreased cellularity
More Than 2mon- ths	Scarring complete	Dense collagenous scar