|Old Myocardial Infarct|
Atherosclerotic coronary stenosis +/- thrombosis.
Less common causes: emboli from mural thrombi, paradoxical embolism, or endocarditis; coronary spasm; polyarteritis; Takayasu's disease; Kawasaki syndrome (infancy and childhood); extension of dissecting aortic aneurysm.
Anomalous origin of left coronary artery from pulmonary trunk.
Endothelium lining atheromatous plaque torn by ulceration, plaque hemorrhage, or fissuring.
Activated platelets adherent to exposed collagen and plaque contents yield ADP boosting massing of platelets, which produce coagulant factors thromboxane A2, serotonin, and platelet factors 3 & 4 with expanding occlusive thrombosis, abetted by tissue thromboplastin release.,
The same risk factors as for atherosclerosis, fatty diets, hypertension, diabetes, smoking, etc.
1,500,000 cases yearly, with 30% mortality.
May occur at any age, but frequency rises with advancing age, 5% occurring under age 40, and only 45% under age 65.
Low incidence in women rises in postmenopausal years, when estrogen relacement is protective.
|General Gross Description|
Lesions not visible before 18-24 hours after onset.
Size variable up to entire transverse sectional area.
May involve partial (subendocardial) or full (transmural) thickness of left ventricular wall.
Earliest change is a poorly defined pale area, some with hemorrhagic changes. Area defined better with time, turning yellow with a pink margin of organizing tissue, and, finally, a discrete scar.
|General Microscopic Description|
Earliest changes, at 4-12 hrs., are nuclear necrosis, muscle coagulative necrosis, neutrophils, and non-contracting (dead) marginal wavy fibers, which may appear histologically viable.
Frank coagulative necrosis at 24-72 hours, loss of fiber nuclei, and heavy neutrophilic infiltrate.
Macrophagic phagocytic activity and early organization at 3-7 days; healed scar by 7 weeks.
Cotran RS etal. Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 495, 524-41
Harrison's Principles of Internal Medicine, 13th Ed: Isselbach et. al. (eds). New York, McGraw-Hill, 1994, p.1066
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|Old Myocardial Infarct
||Synopsis by: J. Hasson M.D. (T33010M54750)