Heart attacks are the most common cause of death in the US. Each year there are about 300,000 new heart attacks, which are fatal in 50% of cases.

A heart attack is the result of a blockage in one of the coronary arteries carrying oxygen-rich blood to the heart muscle. When the blood supply is cut off, a part of the heart muscle dies - or infarcts. A heart attack is also known as a myocardial infarction (MI), coronary thrombosis or, simply "a coronary".

Causes of a heart attack

The underlying cause of most heart attacks is atherosclerosis, a disease of the coronary arteries that usually develops over many years.

Atherosclerosis involves the formation of fatty deposits (plaques) on the walls of the coronary arteries. These plaques can rupture, releasing substances that cause blood flowing in the coronary artery to clot. Combined, the plaque and blood clot (thrombus) can block the coronary artery altogether, resulting in the symptoms of heart attack.

Lesser degrees of narrowing, without complete blockage, of a coronary artery may cause angina

Who is affected?

Heart attacks are more common in elderly people and, up to the age of 50, are more common in men than women. After that age, the difference between men and women narrows.

In addition to age and sex, doctors have identified a number of factors that may occur together to make atherosclerosis, and so a heart attack, more likely. These include:

• smoking,
• a family history of heart disease,
• an inactive lifestyle (less than 30 minutes per day, on most days, of physical activity),
• diabetes,
• obesity,
• high blood pressure,
• high blood cholesterol.

Symptoms

Most heart attacks cause severe pain in the center of the chest. However, sometimes there may be no symptoms at all (silent MI), especially in the elderly and people with diabetes.

The central chest pain is often described as heaviness, squeezing or crushing, and may come on suddenly causing the person to collapse. It may spread to the arms, neck, jaw, face, back or stomach. A person having a heart attack may appear pale, sweaty and breathless. They may feel or be sick. The symptoms can come on suddenly, but sometimes the pain comes on more slowly.