Extensive myocardial infarction: causes and consequences
Author Ольга Кияница
Myocardial infarction (MI, i.e., heart attack) is an irreversible death (necrosis) of the cardiac cells, which occurs again due to a prolonged lack of oxygen (ischemia).
Approximately 1.5 million cases of myocardial infarction are recorded annually in the United States of America.
Severe consequences, which lead to MI, require timely diagnosis and medical therapy. Often, a delay of only half an hour can lead to death. Particularly unfavorable prognosis with extensive myocardial infarction, when there is a lesion of a large area of the heart tissue or all layers of the myocardium.
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Causes of extensive myocardial infarction
Atherosclerosis is a disease that is primarily responsible for the development of acute coronary syndrome.Approximately 90% of myocardial infarctions are the result of acute thrombosis, which is formed against the background of an atherosclerotic coronary disease. Destruction and erosion of plaques are considered the main triggers of coronary thrombosis. After erosion or plaque rupture, platelet activation and aggregation occur, activation of the coagulation process and endosial vasoconstriction, which leads to coronary thrombosis and closure of the vessel.
The formation of a vulnerable plaque within the coronary vasculature leads to a stressful endothelial tension. A large amount of evidence indicates that in many cases, vessel stenosis is less than 70% and they are located in the proximal areas of the coronary mesh. [1 - Falk E; Shah PK; Fuster V. Coronary plaque disruption. Circulation. 1995; 92 (3): 657-71]. Coronary atherosclerosis is particularly noticeable in the branching of vessels.
Unmodifiable (non-amenable) risk factors for atherosclerosis include the following:
- Family predisposition to coronary heart disease
- Male Hair Loss
Modifiable risk factors for the development of atherosclerosis, which can be affected, include the following:
- Smoking, including passive
- Hypercholesterolemia and hypertriglyceridemia, including hereditary disorders of lipoproteins
- High blood pressure
- Obesity (abdominal form)
- Psychosocial stress
- Sedentary lifestyle and / or lack of exercise
- Reducing the consumption of fruits and vegetables
- Poor hygiene of the oral cavity
- Increased level of homocysteine
- The presence of peripheral vascular disease
In addition to atherosclerosis, there are other reasons why myocardial infarction may occur. For non-atherosclerotic reasons, MI includes:
- Coronary occlusion, which develops most often against the background of vasculitis
- Hypertrophy of the ventricles (eg, left ventricular hypertrophy, hypertrophic cardiomyopathy)
- Embolism of the coronary artery, arising from the excess of foreign inclusions in the blood (cholesterol, air or sepsis products)
- Coronary Injury
- Primary coronary vasospasm (variant angina)
- Drug use (for example, cocaine, amphetamine, ephedrine)
- Coronary anomalies, including coronary artery aneurysms
- Conditions in which the need for oxygen increases, such as severe physical stress, fever, or hyperthyroidism
- Diseases that reduce oxygen delivery, such as hypoxemia in severe anemia
- Ruptured aorta with retrograde coronary artery involvement
- Respiratory infections, especially the flu
In addition, extensive MI can be the result of hypoxia due to carbon monoxide poisoning. Often develops with acute pulmonary disorders.
In rare cases, in children, coronary artery disease leading to extensive MI may be associated with Marfan syndrome, Kawasaki disease, Takayasu arteritis, progeria and cystic medial necrosis.
Consequences of extensive myocardial infarction
Acute myocardial infarction is associated with a 30% mortality rate; about 50% of deaths occur before arriving at the hospital. Another 5-10% of survivors die within the first year after myocardial infarction. Approximately half of all patients with MI are re-hospitalized within the first year after a heart attack.
In general, the course of the disease varies greatly and largely depends on the degree of myocardial necrosis, the residual functionality of the left ventricle, and whether the patient has been revascularized.
The most favorable effects are expected in the following cases:
- Successful early reperfusion (the patient was fibrinolized for 30 minutes or percutaneous coronary intervention within 90 minutes after the onset of a heart attack)
- Preserved left ventricular function
- Short-term and long-term treatment with beta-blocker inhibitors, aspirin and angiotensin-converting enzyme (ACE)
Less favorable effects are based on the following impact factors:
- Elderly age
- Presence of diabetes mellitus
- Presence in the anamnesis of vascular diseases (for example, cerebrovascular diseases or peripheral vascular diseases)
- Delayed or unsuccessful reperfusion
- Poorly preserved function of the left ventricle (the strongest predictor of death)
- Determination of congestive heart failure or pronounced pulmonary edema
- Increased level of natriuretic peptide B-type
- Increased highly sensitive C-reactive protein, which is a nonspecific inflammatory marker
Complications also relate to the consequences of extensive myocardial infarction. They can arise immediately after a heart attack, then they are called early, or after a while, defined as late complications.
The most common complications of extensive MI:
- Ventricular aneurysm - severe damage to the heart muscle can lead to myocardial scarring and a weakened area of scar tissue that is capable of bursting.
- Severe forms of arrhythmia by type of ventricular tachycardia or ventricular fibrillation that occur due to impaired electrical impulses.
- Heart failure is when the heart is so damaged that it can no longer adequately pump blood to all parts of the body, resulting in stagnant phenomena.
- Smoothing of the mitral valve, because of which the mitral orifice is not completely closed. Occurs when a heart attack causes a disturbance of the papillary muscle.
- Atrial fibrillation is when the upper parts of the heart are chaotically contracted; which complicates the normal blood flow in the ventricles.
- Pericarditis is an inflammation of the pericardial sac.
- Pulmonary embolism is a blood clot that clogged the vessel in the lungs.
- Stroke - a blood clot that blocked blood flow in the brain vessel.
- Cardiac tamponade is the accumulation of fluid in the pericardial sac, which leads to cardiac arrest.
In nosocomial conditions, cardiogenic shock most often develops, which leads to fatal consequences.
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