A myocardial infarct showing early granulation tissue has most likely occurred:

Changes in myocardial infarction Time Gross Features Light Microscope Electron Microscope Reversible injury 0- 1/2 hr None None Relaxation of myofibril; glycogen loss; mitochondrial swelling Irreversible injury 1/2 - 4 hr None Usually none; variable waviness of fibrous at border Sarcolemmal disruption; mitochondrial amorphous densities 4-12 hr Dark mottling (occasional) Early coagulation necrosis; edema; hemorrhage 12-24 hr Dark mottling Ongoing coagulation necrosis; pyknosis of nuclei; myocyte hypereosinophilia; marginal contraction band necrosis; early neutrophilic infiltrate 1-3 days Mottling with yellow - tan infarct center Coagulation necrosis, with loss of nuclei and striations, brisk 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; granulation tissue at margins 10-14 days Red - grey depressed infarct borders Well - established granulation tissue with new blood vessels and collagen deposition 2-8 w Gray - white scar, progressive from border toward core of infarct Increased collagen deposition, with decreased cellularity >2 mo Scarring complete Dense collagenous scar