Myocardial Infarction

Myocardial infarction (MI) or acute myocardial infarction (AMI), commonly known as a heart attack, results from the partial interruption of blood supply to a part of the heart muscle, causing the heart cells to be damaged or die. This is most commonly due to occlusion (blockage) of a coronary artery following the rupture of a vulnerable atherosclerotic plaque, which is an unstable collection of cholesterol and fatty acids and white blood cells in the wall of an artery. The resulting ischemia (restriction in blood supply) and ensuing oxygen shortage, if left untreated for a sufficient period of time, can cause damage or death (infarction) of heart muscle tissue (myocardium).

Typical symptoms of acute myocardial infarction include sudden retrosternal chest pain (typically radiating to the left arm or left side of the neck), shortness of breath, nausea, vomiting, palpitations, sweating, and anxiety (often described as a sense of impending doom). Women may experience fewer typical symptoms than men, most commonly shortness of breath, weakness, a feeling of indigestion, and fatigue. A sizeable proportion of myocardial infarctions (22–64%) are "silent", that is without chest pain or other symptoms.

Among the diagnostic tests available to detect heart muscle damage are an electrocardiogram (ECG), echocardiography, cardiac MRI and various blood tests. The most often used blood markers are the creatine kinase-MB (CK-MB) fraction and the troponin levels. Immediate treatment for suspected acute myocardial infarction includes oxygen, aspirin, and sublingual nitroglycerin.

Most cases of myocardial infarction with ST elevation on ECG (STEMI) are treated with reperfusion therapy, such as percutaneous coronary intervention (PCI) or thrombolysis. Non-ST elevation myocardial infarction (NSTEMI) may be managed with medication, although PCI may be required if the patient's risk warrants it. People who have multiple blockages of their coronary arteries, particularly if they also have diabetes mellitus, may benefit from bypass surgery (CABG). The European Society of Cardiology guidelines in 2011 proposed treating the blockage causing the myocardial infarction by PCI and performing CABG later when the patient is more stable. Rarely CABG may be preferred in the acute phase of myocardial infarction, for example when PCI has failed or is contraindicated.

Ischemic heart disease (which includes myocardial infarction, angina pectoris and heart failure when preceded by myocardial infarction) was the leading cause of death for both men and women worldwide in 2004. Important risk factors are previous cardiovascular disease, older age, tobacco smoking, high blood levels of certain lipids (low-density lipoprotein cholesterol, triglycerides) and low levels of high density lipoprotein (HDL) cholesterol, diabetes, high blood pressure, lack of physical activity and obesity, chronic kidney disease, excessive alcohol consumption, the use of illicit drugs (such as cocaine and amphetamines), and chronic high stress levels.