What is a coronary artery spasm?
The heart muscle gets its blood supply from blood vessels called the coronary arteries.  When and if these coronary arteries spasms blood flow to part of the heart is reduced, and sometimes even stopped. This spasm is also referred to as a vasospasm. 

What causes coronary artery spasms?
The cause of these spasms is not known, but it is known that they tend to occur in both normal coronary arteries or in arteries that may be blocked by fatty buldups. Spasms typically occur during rest, not while people are exerting themselves in activities such as exercise, etc.

What are the signs and symptoms of coronary artery spasms?
Chest pain and/or discomfort are common symptoms of coronary artery spasms. Spasms are typically treated with calcium channel blockers, but if they get severe they can lead to heart attack.