myocardial infarction

myocardial infarction. A myocardial infarction, commonly known as a heart attack, is a life-threatening event characterized by the interruption of blood flow to a part of the heart, leading to necrosis of cardiac muscle. It represents a major manifestation of coronary artery disease and is a leading cause of morbidity and mortality worldwide. Rapid diagnosis and intervention are critical to limit damage and improve outcomes.

Definition and classification

The universal definition was established by a joint task force of the European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Heart Federation. It is typically classified based on electrocardiographic findings into ST elevation myocardial infarction and non-ST elevation myocardial infarction. Other systems consider the anatomical region affected, such as an anterior wall myocardial infarction or inferior wall myocardial infarction. The pathological classification differentiates between a Type 1 event, caused by atherosclerotic plaque rupture, and a Type 2 event, related to an imbalance in myocardial oxygen supply and demand.

Signs and symptoms

The classic symptom is severe chest pain, often described as pressure or squeezing, which may radiate to the left arm, jaw, or back. Patients frequently experience associated symptoms such as dyspnea, nausea, diaphoresis, and a sense of impending doom, known as angor animi. Atypical presentations are more common in certain populations, including individuals with diabetes mellitus, the elderly, and women, who may present primarily with fatigue or epigastric pain. Silent myocardial infarctions, with minimal or no symptoms, are also recognized and often detected incidentally on subsequent electrocardiogram testing.

Causes and pathophysiology

The predominant cause is the acute thrombosis following rupture or erosion of an atherosclerotic plaque within a coronary artery. This process is driven by complex interactions between inflammatory cells, lipids, and the vascular endothelium. The resulting thrombus obstructs blood flow, leading to ischemia and, if prolonged, irreversible cell death. Less common etiologies include coronary artery spasm, embolism from conditions like atrial fibrillation, dissection of the coronary artery, or a severe mismatch in oxygen supply and demand, as seen in septic shock or anemia.

Diagnosis

Diagnosis relies on a combination of clinical assessment, electrocardiogram findings, and measurement of biomarkers. The electrocardiogram may show characteristic changes such as ST segment elevation or new pathological Q waves. The cardinal biomarker is troponin, a protein released from damaged myocytes, with assays standardized by organizations like the International Federation of Clinical Chemistry. Imaging modalities such as echocardiography can identify regional wall motion abnormalities, while coronary angiography remains the gold standard for visualizing the location and extent of coronary artery obstruction.

Treatment

Immediate management focuses on restoring perfusion. For ST elevation myocardial infarction, primary percutaneous coronary intervention is the preferred strategy, often performed at specialized cardiac catheterization laboratory facilities. If unavailable promptly, fibrinolytic therapy with agents like alteplase is administered. Adjunctive medical therapy includes dual antiplatelet therapy with aspirin and a P2Y12 inhibitor, anticoagulants, beta blockers, angiotensin-converting enzyme inhibitors, and high-intensity statins. The American Heart Association and European Society of Cardiology guidelines also emphasize cardiac rehabilitation for secondary prevention.

Prognosis and epidemiology

It remains a leading cause of death globally, with significant burden reported by the World Health Organization. Prognosis is influenced by factors such as the extent of necrosis, the success of revascularization, the development of complications like heart failure or ventricular fibrillation, and the management of risk factors. Epidemiological studies, including the Framingham Heart Study and INTERHEART study, have identified key modifiable risk factors including hypertension, dyslipidemia, smoking, and diabetes mellitus. Mortality rates have declined in many regions due to advances in acute care and preventive strategies. Category:Cardiovascular diseases