Angina pectoris is the medical term for chest pain due to coronary heart disease. This is a condition in which the heart muscle doesn't receive enough blood, resulting in pain in the chest.

Angina is a symptom of a condition called myocardial ischemia. It 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. Insufficient blood supply is called ischemia.

When does angina pectoris occur?

Angina pectoris can occur when blood flow to the heart is enough for normal needs but not enough when the heart's needs increase. It may happen during physical exercise, strong emotions, or extreme temperatures. 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're resting. (See Prinzmetal's or variant angina pectoris below.)

• Angina is a sign that someone is at risk of heart attack.

What is variant angina pectoris (Prinzmetal's angina)?

Variant angina pectoris is also called Prinzmetal's angina. It differs from typical angina in that it occurs almost exclusively when a person is at rest, and it doesn't follow a period of physical exertion or emotional stress. Attacks can be very painful and usually occur between midnight and 8 a.m. It's associated with:

• acute myocardial infarction (heart attack).
  
• severe cardiac arrhythmias. These may include ventricular tachycardia and fibrillation.
  
• sudden cardiac death.

Many people with Prinzmetal's angina go through an acute, active phase. Anginal and cardiac events may occur frequently for six months or more. During this time, nonfatal myocardial infarction occurs in up to 20 percent of patients; death occurs in up to 10 percent. People who develop serious heart rhythm disturbances (arrhythmias) at this time are at greater risk of sudden death.

Most people who survive an infarction or this initial three- to six-month period stabilize, and symptoms and cardiac events tend to diminish over time. Long-term survival is excellent, ranging from 89 to 97 percent at five years. Patients without significant obstructive coronary artery disease have an excellent long-term outlook.

The ergonovine test is the most sensitive and useful test for coronary spasm. In this, the drug ergonovine is administered to induce coronary spasm. Hyperventilation and coronary injections of acetylcholine are other means used to provoke variant angina.