PATHOGENESIS, SYMPTOMS, AND DIAGNOSTIC METHODS OF MYOCARDIAL INFARCTION

Аннотация

Acute myocardial infarctions are one of the leading causes of death in the developed world, with prevalence approaching three million people worldwide, with more than one million deaths in the United States annually. This statistic reviews the presentation, evaluation, and management of patients with acute myocardial infarctions and highlights the role of the interprofessional team in caring for these patients. Key words: Myocardial infarction, heart attack, cardiac troponin, electrocardiogram, upper reference limit. A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle.¹ Myocardial infarction is defined as sudden ischemic death of myocardial tissue. In the clinical context, myocardial infarction is usually due to thrombotic occlusion of a coronary vessel caused by rupture of a vulnerable plaque. Ischemia induces profound metabolic and ionic perturbations in the affected myocardium and causes rapid depression of systolic function. Prolonged myocardial ischemia activates a “wavefront” of cardiomyocyte death that extends from the subendocardium to the subepicardium. Mitochondrial alterations are prominently involved in apoptosis and necrosis of cardiomyocytes in the infarcted heart. The adult mammalian heart has negligible regenerative capacity, thus the infarcted myocardium heals through formation of a scar. Infarct healing is dependent on an inflammatory cascade, triggered by alarmins released by dying cells. Clearance of dead cells and matrix debris by infiltrating phagocytes activates anti-inflammatory pathways leading to suppression of cytokine and chemokine signaling. Activation of the renin- angiotensin-aldosterone system and release of transforming growth factor-β induce conversion of fibroblasts into myofibroblasts, promoting deposition of extracellular matrix proteins. Infarct healing is intertwined with geometric remodeling of the chamber, characterized by dilation, hypertrophy of viable segments, and progressive dysfunction. ² Risk factors Most MIs occur due to coronary artery disease.³ Risk factors include : high blood pressure, https://scientific-jl.com/wsrj 2 2 7 Volume-39_Issue-1_May-2025 World scientific research journal smoking, diabetes, lack of exercise, obesity, high blood cholesterol, poor diet and excessive alcohol intake. The complete blockage of a coronary artery caused by a rupture of an atherosclerotic plaque is usually the underlying mechanism of an MI.³ MIs are less commonly caused by coronary artery spasms, which may be due to cocaine, significant emotional stress (commonly known as Takotsubo syndrome or broken heart syndrome) and extreme cold, among others.⁴ A number of tests are useful to help with diagnosis, including electrocardiograms (ECGs), blood tests and coronary angiography. An ECG, which is a recording of the heart's electrical activity, may confirm an ST elevation MI (STEMI), if ST elevation is present. Commonly used blood tests include troponin and less often creatine kinase MB. Symptoms Symptoms of a heart attack vary. Some people have mild symptoms. Others have severe symptoms. Some people have no symptoms. Common heart attack symptoms include: Chest pain that may feel like pressure, tightness, pain, squeezing or aching Pain or discomfort that spreads to the shoulder, arm, back, neck, jaw, teeth or sometimes the upper belly Cold sweat Fatigue Heartburn or indigestion Lightheadedness or sudden dizziness Nausea Shortness of breath Women may have atypical symptoms such as brief or sharp pain felt in the neck, arm or back. Sometimes, the first symptom sign of a heart attack is sudden cardiac arrest. Some heart attacks strike suddenly. But many people have warning signs and symptoms hours, days or weeks in advance. Chest pain or pressure (angina) that keeps happening and doesn't go away with rest may be an early warning sign. Angina is caused by a temporary decrease in blood flow to the heart. Clinical criteria for MI The clinical definition of MI denotes the presence of acute myocardial injury detected by abnormal cardiac biomarkers in the setting of evidence of acute myocardial ischaemia. https://scientific-jl.com/wsrj 2 2 8 Volume-39_Issue-1_May-2025 World scientific research journal Criteria for myocardial injury Detection of an elevated cTn value above the 99th percentile URL is defined as myocardial injury. The injury is considered acute if there is a rise and/or fall of cTn values. Criteria for type 1 MI Detection of a rise and/or fall of cTn values with at least one value above the 99th percentile URL and with at least one of the following: Symptoms of acute myocardial ischaemia; New ischaemic ECG changes; Development of pathological Q waves; Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischaemic aetiology; Identification of a coronary thrombus by angiography inclu