Sometimes a coronary artery (one of the vessels supplying blood to the heart muscle) goes into spasm. This is also called vasospasm, and doctors are unsure of its cause. The spasm briefly narrows the coronary artery, so your heart does not get enough blood. Coronary artery spasm usually happens in a coronary artery that has been blocked or has fatty buildup (atherosclerosis), but it may happen in a normal coronary artery as well.

Coronary artery spasm causes a rare type of angina pectoris called variant angina pectoris (or Prinzmetal's angina ). Angina pectoris is a squeezing, suffocating, or burning feeling in the chest. Unlike typical angina, variant angina usually happens during times of rest. Some patients find that the attacks happen more often between midnight and 8 in the morning. Often, the attacks happen at the same time each day. These attacks may be very painful.

A medicine called nitroglycerin can relieve an episode of angina. Patients may also receive medicines called calcium channel blockers.

Patients with variant angina have a greater risk of heart attack, an irregular heartbeat (arrhythmia), and even sudden death.

See also on this site:

Coronary Artery Disease

See on other sites:

MedlinePlus Medical Encyclopedia
www.nlm.nih.gov/medlineplus/ency/article/000159.htm
Coronary Artery Spasm