Prinzmetal's variant angina (PVA) is characterized by recurrent episodes of chest pain (angina) that usually occur when a person is at rest, between midnight and early morning. Typical angina, by contrast, is often triggered by physical exertion or emotional stress. Episodes of PVA can be very painful, and may last from several minutes to thirty minutes. In some cases the pain may spread from the chest to the head, shoulder, or arm. The pain associated with PVA is caused by a spasm in the arteries that supply blood to the heart muscle (coronary arteries). This results in an obstruction of blood flow. In some people, persistent spasms increase the risk for serious complications such as a life-threatening arrhythmia or heart attack. PVA most commonly occurs in people who smoke and people who have high cholesterol or high blood pressure. In many cases it occurs for unknown reasons in otherwise healthy people. In some cases it may be triggered by alcohol withdrawal, stress, exposure to cold, certain medications, or use of stimulants such as cocaine. The diagnosis of PVA involves findings on an electrocardiogram, evidence of the spasms on angiogram, and relief of sudden symptoms with medicines called nitrates.