146. Myocardial infarction: definition, causes, classification, pathogenesis. Stages of development and outcome.

Myocardial infarction is an ischemic necrosis of the heart muscle, the so—called ischemic (white) infarction with a hemorrhagic corolla.

Classification 1. In size – microscopic, small focal, large focal, total, 2. In relation to the wall of the heart: subendocardial, transmural, intramural, subepicardial. 3. Downstream — acute, acute (up to 4 weeks), recurrent (within 4 weeks), repeated (after 4 weeks). from 4. By localization — anteroposteroid, lateral wall, posteroposteroid, total.

Pathogenesis

The course of myocardial infarction goes through 3 stages: ischemic, necrotic and scarring stage.

The ischemic stage is the development of acute ischemia, fatty and protein dystrophy, turning into myocardial necrobiosis.

In the necrotic stage, during histological examination, the infarction area is a necrotic tissue in which islets of unchanged myocardium are preserved perivascularly. This stage is characterized not only by necrosis in the focus of a heart attack, but also by deep dyscirculatory and metabolic disorders of the heart muscle outside the focus.

The stage of scarring (organization) of myocardial infarction begins with the replacement of leukocytes by macrophages and young fibroblastic cells. Leukocytes and macrophages are involved in the resorption of necrotic masses. There is an organization of a heart attack, which lasts about 4 weeks. Thus, when organizing a heart attack, a dense, shapeless scar forms in its place, and postinfarction large-focal cardiosclerosis develops. The preserved myocardium, especially along the periphery of the scar, undergoes regenerative hypertrophy.

Stages of acute myocardial infarction 1. Early - up to 18 hours after the onset of clinical manifestations. 2. Necrotic 18 hours – 3-7 days after the onset of clinical manifestations. 3. Stage of organization – 3-7 days – 4 weeks

Outcomes of myocardial infarction

A. Favorable - organization, formation of a heart aneurysm

B. Unfavorable - heart rupture, parietal thrombosis, pericarditis

147. . Complications of myocardial infarction: early and late, pathological anatomy, causes of death of patients.

Complications of myocardial infarction: cardiogenic shock, ventricular fibrillation, asystole, acute heart failure, myomalacia, acute aneurysm and rupture of the heart, parietal thrombosis, pericarditis.

Myomalacia, or melting of necrotic myocardium, occurs when autolysis of dead tissue prevails. It leads to a rupture of the heart and hemorrhage into the pericardial cavity, hemopericardium and tamponade of the heart cavity develop.

An acute aneurysm of the heart — a bulging of its necrotic wall — is formed with an extensive heart attack. The aneurysm cavity is usually thrombosed, endocardial tears appear in its wall, blood penetrates into these tears, exfoliates the endocardium and destroys the necrotized myocardium. There is a rupture of the heart and hemopericardium.

Parietal thrombi are formed in subendocardial and transmural myocardial infarction, they are dangerous for thromboembolic complications. Fibrinous pericarditis is often found in subepicardial and transmural myocardial infarction.

Death in myocardial infarction is associated with necrosis of the heart muscle and its complications. The immediate causes of death in the early period of a heart attack are ventricular fibrillation, asystole, cardiogenic shock, acute heart failure. Fatal complications of myocardial infarction in the late period are a rupture of the heart or its acute aneurysm with hemorrhage into the pericardial cavity, thromboembolism from the cavities of the heart (for example, cerebral vessels). The source of thromboembolism is thrombi on the endocardium in the area of infarction, in an acute aneurysm, in the ears of the heart