Angina could be a tip off.

A heart attack, or myocardial infarction, occurs when the blood supply to part of the heart muscle (the myocardium) is reduced severely or stopped. This occurs when one of the coronary arteries (the arteries that supply blood to the heart muscle) is blocked by an obstruction, such as a blood clot that has formed on plaque due to atherosclerosis. Such an event sometimes is called a coronary thrombosis or coronary occlusion.

If the blood supply is cut off drastically or for a long time, muscle cells suffer irreversible injury and die. Disability or death can result, depending on how much heart muscle is damaged.

When a coronary artery temporarily contracts or goes into spasm, it narrows and blood flow to part of the heart muscle decreases or even stops. What causes a spasm is unclear, but it can occur in normal blood vessels as well as those partially blocked by atherosclerosis. If a spasm is severe, a heart attack may result.

Chest pain called angina pectoris is another result of coronary artery disease. Angina is a symptom of a condition called myocardial ischemia, which occurs when the heart muscle (myocardium) doesn't get as much blood (hence as much oxygen) as it needs for a given level of work. Lack of blood supply is called ischemia.

Angina pectoris can occur when blood circulation to the heart is enough for normal needs, but not sufficient when the heart's needs increase, such as during physical exertion or emotional excitement. Running to catch a bus. for example, could trigger an attack of angina, while walking to a bus stop might not. Some people, such as those with a coronary artery spasm, may have angina when they are resting. Angina can be a warning sign that someone is at risk of heart attack.

Angina pectoris can be treated with drugs that affect the supply of blood to the heart muscle or the heart's demand for oxygen. Some drugs, called coronary vasodilators, cause blood vessels to relax. When this happens, the opening inside the vessels gets bigger. Blood flow improves, allowing more oxygen and nutrients to reach the heart muscle. Nitroglycerin is the drug most often used to relax the veins (reducing the amount of blood returning to the heart and thus lessening the work of pumping) and the coronary arteries (increasing the blood supply to the heart).

Alternatively, the heart's demand for oxygen can be modified. For example, a drug can be prescribed to reduce blood pressure and thus reduce the heart's workload and need for...