A 60 year old male presented with acute chest pain of 4 hours duration. Electrocardiographic examination revealed new Q wave with ST segment depression. He suffered to his illness within 24 hours of admission. The hea revealed presence of a transmural hemorrhagic area over the septum and anterior wall of the left ventricle. Light microscopic examination is most likely to reveal:
Answer is B (Necrotic myofibres with presence of neutrophils) The patient in question succumbed to myocardial infarction after about 24 hours of the attack. Characteristic morphological changes evolve in the hea of patients with MI depending on duration since the attack. After twenty four hours of the attack light microscope shows coagulative necrosis of myofibrils with loss of nuclei and striations along with an interstitial infiltrate of neutrophils. Evolution of morphologic changes in myocardial infarction Time Gross Features Light Microscope Electron Microscope Reversible Injury 0 to '/2 hr None None Relaxation of myofibrils; glycogen loss; mitochondria! swelling Irreversible injury 1/2 - 4 hr None Usually none; variable waviness of fibres at border Sarcolemmal disruption; mitochondrial amorphous densities 4-12 hr Occassionally dark mottling Beginning coagulation necrosis; edema; hemorrhage 12-24 hr Dark mottling Ongoing coagulation necrosis; pyknosis of nuclei; myocyte hypercosinophilia; marginal contraction band necrosis; beginning neutrophilic infiltrate 1-3 days Mottling with yellow-tan Coagulation necrosis, with loss of infarct center nuclei and striations; interstitial infiltrate of neutrophils 3-7 days Hypermic border; central Beginnig disintegration of dead yellow-tan softening myofibers, with dying neutrophils; early phagocytosis of dead cells by -macrophages at infarct border 7-10 days Maximally yellow tan and Well-developed phagocytosis of dead soft, with depressed red- ells: early formation offibrovascular tan margins granulation tissue at margins 10-14 days Red-gray depressed infarct Well-established granulation tissue borders with new blood vessels and collagen deposition 2-8 wks Gray-white scar, progressive from border toward core of infarct Increased collagen deposition, with decreased cellularity > 2 'no Scarring complete Dense collagen scar
Edema in between normal myofibrils
Necrotic myofibrils with presence of neutrophils
Coagulative necrosis of the myocytes with presence of granulation tissue
Infiltration by histiocytes with hemosiderin laden macrophages