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Myocardial Infarction

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Diagram of a myocardial infarction

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to a part of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat, or feeling tired. About 30% of people have atypical symptoms, with women more likely than men to present atypically. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms.

Pathophysiology

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Illustration showing the blockage of a coronary artery

Myocardial infarction results from the interruption of blood supply to a part of the heart, causing heart cells to die. This is most commonly due to blockage of a coronary artery following the rupture of a vulnerable atherosclerotic plaque, an unstable collection of lipids (fatty acids) and white blood cells (especially macrophages) in the wall of an artery. The resulting ischemia and oxygen shortage, if left untreated for a sufficient period of time, can cause damage or death (infarction) of heart muscle tissue (myocardium).

Diagnosis

The diagnosis of myocardial infarction is based on the patient's history, a physical examination, and the results of electrocardiogram (ECG) and blood tests. The ECG is used to identify the presence of ST elevation, which indicates a STEMI (ST-Elevation Myocardial Infarction). Blood tests are used to measure cardiac biomarkers such as troponin and creatine kinase-MB (CK-MB).

Treatment

Immediate treatment for a suspected myocardial infarction includes aspirin to prevent further blood clotting, nitroglycerin to relieve chest pain, and oxygen therapy if the patient is hypoxic. Reperfusion therapy is the mainstay of treatment for STEMI, which includes thrombolysis or percutaneous coronary intervention (PCI). For NSTEMI (Non-ST-Elevation Myocardial Infarction), treatment may include antiplatelet drugs, anticoagulants, and PCI.

Prevention

Prevention of myocardial infarction involves lifestyle changes and medications to reduce risk factors. This includes smoking cessation, maintaining a healthy diet, regular exercise, and controlling hypertension, diabetes, and hyperlipidemia. Medications such as statins, beta blockers, and ACE inhibitors may be prescribed to lower the risk of future heart attacks.

Related pages

• Coronary artery disease
• Cardiac arrest
• Heart failure
• Atherosclerosis