What Causes A Heart Attack?

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By Dr Ananya Mandal, MD

A heart attack is a medical emergency caused by a blockage occurring in one or more of the coronary arteries that supply blood to the heart muscles. The obstruction usually takes the form of a blood clot that prevents part of the heart tissue being supplied with oxygen.

This lack of blood supply and oxygen can cause injury to the heart muscle and if supply is prevented for more than 20 minutes, the part of the muscle tissue failing to receive blood may die. This restricted blood flow and oxygen supply is referred to medically as ischemia and the tissue death that occurs as a result is called infarction. A heart attack is also called myocardial infarction.

Causes of heart attack

One of the most common causes of heart attack is coronary artery disease, where the coronary arteries become hardened and narrowed due to atherosclerosis. Atherosclerosis refers to the build-up of fatty plaques or atheromas in the walls of the arteries. These plaques are made up of platelets, clots and cholesterol. Over time, the thickened walls reduce blood flow through the coronary artery or completely block the artery in cases where a blood clot forms. This leads to a heart attack.
Another cause of heart attack is sudden severe spasm or tightening of the coronary artery that blocks the blood supply. This can occur irrespective of whether coronary artery disease is present. Spasm of the coronary arteries can occur due to severe emotional stress, cigarette smoking, exposure to extreme cold or the use of illicit drugs.

Risk factors

Some factors that can increase the risk for heart attack are described below:

Factors that cannot be changed
- Age over 45 years in men and over 55 years in women
- Those with a family history of early heart disease
- Those with a history of angina and other heart conditions
- Certain ethnicities such as African and African-Caribbean
Modifiable risk factors:
- Smoking
- Obesity or overweight
- Lack of physical activity
- Diet rich in saturated fatty acids and trans fatty acids
- Diabetes
- High blood pressure
- High blood cholesterol
- Metabolic syndrome, which refers to the presence of combined high blood cholesterol, diabetes, obesity and high blood pressure. A person with metabolic syndrome is twice as likely to develop heart disease as a person without the syndrome.