Coronary artery spasm is a temporary, abrupt, and focal (restricted to one location) contraction of the muscles in the wall of an artery in the heart, which constricts the artery. This spasm slows or stops blood flow through the artery.

Coronary artery spasm is a cause of inadequate oxygen levels (ischemia) of the heart. It affects approximately 4 out of 100,000 people, and affects approximately 2% of patients with angina.

The spasm may occur in arteries that appear normal or it may take place in arteries that have turned hard due to plaque build up (atherosclerosis). 

Spasm may be "silent" -- without symptoms -- or it may result in stable angina or unstable angina. The most typical manifestation of coronary spasm is variant angina (see below). Prolonged spasm may even cause a heart attack.

Variant angina is a type of chest pain that is thought to be due to endothelial dysfunction, a condition in which the coronary artery may appear normal, but does not function normally. 

Coronary artery spasm may occur spontaneously, or it may be caused by exposure to cold, emotional stress, alcohol withdrawal, or vasoconstricting medications. Cocaine use and cigarette smoking can cause severe spasm of the arteries while at the same time increasing the energy requirements of the heart. In many people, coronary artery spasm may occur without any other heart risk factors (such as smoking, diabetes, high blood pressure, and high cholesterol).

The main symptom is angina (a type of chest pain), with these characteristics:

• Under the chest bone
• Described as squeezing, constricting, tightness, pressure, crushing -- it is usually severe and may radiate to the neck, jaw, shoulder, or arm
• It often occurs at rest
• May occur at the same time each day, usually between midnight and 8:00 AM
• Pain lasts from 5 to 30 minutes
• Pain is relieved by nitroglycerin
• Syncope (loss of consciousness) can accompany the angina

Tests to diagnose coronary artery spasm may include:

• Coronary angiography
• ECG