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 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 and calcium channel blockers are also used.

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