Myocardial infarction (MI) is the most common result of coronary heart disease (CHD), and often result from atherosclerotic plaque rupture. The rupture of a coronary atherosclerotic plaque can block or dramatically restrict the blood flow to the myocardium, causing parts of the myocardium to become infarcted. This initiates a cascade of cellular and molecular changes that alter the tissue properties and function of the myocardium. Among these are pronounced cardiomyocyte necrosis, inflammation and increased extracellular matrix (ECM) protein formation. These processes further limit the heart’s capacity and can lead to heart failure. There are two clinical manifestations of MI, ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI). STEMI leads to detectable changes in the heart rhythm using electrocardiogram (ECG), whereas NSTEMI does not.
Most MIs occur as a result of CHD. The risk factors include increasing age, high blood pressure, smoking, diabetes, high blood cholesterol, unhealthy dietary habits and lack of exercise, alcohol consumption and obesity. MI is a major cause of mortality and cardiovascular-related admission to hospital, and it often leads to heart failure. MI is therefore considered a major health concern.
How many suffer from myocardial infarction?
MI is a frequent event in cardiovascular patients suffering from CHD, with more than 10 million events registered annually worldwide and 1.5 million cases in the United States. MI is considered to be the leading cause of morbidity and mortality worldwide and incidence rates are expected to increase over the coming years. STEMI occurs roughly twice as often in women compared to men, and STEMI patients generally have a worse prognosis than NSTEMI patients.
How is myocardial infarction diagnosed?
Patients experiencing MI often complain about chest pain and discomfort in the chest, shoulders and arms. Patients can also experience shortness of breath, nausea, and feeling faint. However, these symptoms are not unique for cardiovascular diseases, and further diagnostic measures are applied.
Because MI leads to tissue damage, cardiac-specific biomarkers are released such as troponin, and can be measured in the blood of patients. ECG is the most common non-invasive tool used for diagnosis of MI and it is often used repeatedly over minutes to hours to monitor changes in the cardiac rhythm after admission to hospital. ECG also enables separation of STEMI and NSTEMI. Imaging techniques, such as angiography, are also frequently used as these provide information on the heart structure and potential abnormalities.
How is myocardial infarction treated?
Early treatment of MI is crucial for patient outcome. In general, treatment strategies aim at unblocking the occluded artery to restore blood supply to the infarcted area(s) of the heart. Aspirin is commonly used to reduce blood coagulation and clotting, resulting in a reduction of mortality upwards of 50% in acute MI patients. Heparin, a blood thinner, is also commonly administered. Both STEMI and NSTEMI patients are treated with percutaneous coronary intervention (PCI) in combination with stents to increase blood flow through the affected artery(ies). Following an MI, lifestyle modifications are recommended to reduce the burden of risk factors, and long-term treatment may include aspirin, beta blockers and statins.