Describe the timeline of histologic changes in the myocardium after an acute transmural myocardial infarction.

Describe the timeline of histologic changes in the myocardium after an acute transmural myocardial infarction.

• A. 0-12 hours: subtle changes; 12-24 hours: early coagulative necrosis; 1-3 days: extensive coagulative necrosis with neutrophil infiltration; 3-7 days: macrophage-mediated clearance and granulation tissue begins; 1-2 weeks: granulation tissue with neovascularization; >2 weeks: scar formation.
• B. 0-12 hours: edema; 12-24 hours: coagulative necrosis; 1-3 days: neutrophil infiltration; 3-7 days: granulation tissue; 1-2 weeks: scar formation; >2 weeks: none.
• C. 0-24 hours: subtle changes; 24-72 hours: early coagulative necrosis; 3-5 days: neutrophil infiltration; 5-7 days: macrophage clearance; 1-2 weeks: granulation tissue; >2 weeks: scar.
• D. 0-12 hours: edema; 12-24 hours: edema; 1-3 days: neutrophil infiltration; 3-7 days: macrophage clearance; 1-2 weeks: granulation tissue; >2 weeks: scar formation.

Answer: (A)

After a transmural myocardial infarction, healing follows a characteristic sequence of histologic changes. In the first half-day to 12 hours, you see subtle alterations such as edema and early disruption of myocytes. By 12–24 hours, early coagulative necrosis becomes evident, with loss of nuclei and increased eosinophilia in affected myocytes. From day 1 to day 3, neutrophils infiltrate the infarcted area as they respond to necrotic debris. Between days 3 and 7, macrophages arrive to phagocytose dead cells and debris, and granulation tissue begins to form at the margins. By about 1–2 weeks, granulation tissue with neovascularization is well established, reflecting ongoing repair and organization. After more than 2 weeks, scar formation predominates as collagen replaces the necrotic tissue, completing the maturation of the scar.

After a transmural myocardial infarction, healing follows a characteristic sequence of histologic changes. In the first half-day to 12 hours, you see subtle alterations such as edema and early disruption of myocytes. By 12–24 hours, early coagulative necrosis becomes evident, with loss of nuclei and increased eosinophilia in affected myocytes. From day 1 to day 3, neutrophils infiltrate the infarcted area as they respond to necrotic debris. Between days 3 and 7, macrophages arrive to phagocytose dead cells and debris, and granulation tissue begins to form at the margins. By about 1–2 weeks, granulation tissue with neovascularization is well established, reflecting ongoing repair and organization. After more than 2 weeks, scar formation predominates as collagen replaces the necrotic tissue, completing the maturation of the scar.