Variant angina, and less commonly Prinzmetal angina, vasospastic angina, angina inversa, coronary vessel spasm, or coronary artery vasospasm, is a syndrome typically consisting of angina (cardiac chest pain) in contrast to stable angina which is generally triggered by exertion or intense exercise, commonly occurs in individuals at rest or even asleep and is caused by vasospasm, a narrowing of the coronary arteries due to contraction of the heart's smooth muscle tissue in the vessel walls.