What is Prinzmetal's angina?
Prinzmetal's angina is a form of chest pain, pressure, or tightness (angina) caused by spasms in the arteries that supply blood to the heart. It is a form of unstable angina, meaning that it occurs at rest, often without a predictable pattern. This is in contrast to stable angina, in which chest pain occurs in a predictable pattern during exertion or exercise.1
Episodes of chest pain caused by Prinzmetal's angina usually occur in clusters, with periods of frequent episodes lasting for a few months followed by weeks or months with no chest pain episodes. The pain usually occurs between midnight and approximately 8:00 AM.2 Prinzmetal's angina may have no identifiable trigger, or may be brought on by hyperventilation, exposure to cold, or extreme emotional stress.
Prinzmetal's angina is named after the researcher who first noted that coronary artery spasms were to blame. It is also called variant angina because of the unusual pattern of chest pain episodes.
What causes Prinzmetal's Angina?
The chest pain of Prinzmetal's angina is caused by coronary artery spasm—an abnormal or involuntary constriction of the muscle in an artery of the heart. This spasm makes the diameter of the artery smaller, restricting the supply of blood and oxygen to the heart, causing chest pain. In rare cases if the spasm is not stopped it can lead to a heart attack.
How common is Prinzmetal's Angina and who is likely to have it?
Prinzmetal's angina is relatively rare and the actual number of cases is not well documented. Some estimate that 4 out of every 100,000 Americans have it, or about 2% to 3% of people with chest pain who undergo an X-ray of the heart called a cardiac catheterization (also known as an angiogram).3 Men are more likely to suffer Prinzmetal's angina than women: about 70% to 90% of patients are male. It also seems to be more common among Japanese people than Caucasians.3 However, Caucasian women are more likely than Japanese women to have Prinzmetal's angina.4 People with Prinzmetal's angina are generally younger than those with stable angina1; the average Prinzmetal's angina patient is between 51 and 57 years old.3 They also have fewer risk factors for heart disease with the exception of smoking, which is the most significant risk factor for coronary artery spasm.5
The majority of people with Prinzmetal's angina also have coronary artery disease, characterized by atherosclerosis (“hardening of the arteries”). This means there is a buildup of fatty plaque in the arteries of the heart, making the arteries stiffer, thus making it more difficult for blood and oxygen to reach the heart. Prinzmetal's angina alone rarely causes a heart attack, but heart attacks may occur more often in patients with severe underlying heart disease. There is also a very slight risk of sudden death (about 2%) in people with Prinzmetal's angina.3 Coronary artery spasms can also be “silent” – meaning they occur without any symptoms.
What are the symptoms of Prinzmetal's angina?
The chest pain from Prinzmetal's angina often has the following characteristics:
- Located under the chest bone
- Described as squeezing, constricting, tightness, pressure, or crushing, which is usually severe and may radiate to the neck, jaw, shoulder, or arm
- Often occurs at rest
- May occur at the same time each day, usually between 12:00 midnight and 8:00 AM
- Lasts from 5 to 30 minutes
- Relieved by nitroglycerin
- Can cause fainting or loss of consciousness
What causes coronary spasms?
It is not known exactly what causes coronary spasms. They may be due to problems with the thin lining of the blood vessels called the endothelium. Usually the artery lining produces a chemical (nitric oxide) that widens the blood vessel allowing blood to flow through with ease. If the artery lining is damaged or isn't working properly, the blood vessels may narrow more easily, which may cause a coronary spasm. This idea is supported by research done in women. Levels of the artery-widening chemical are higher when estrogen levels are also high at certain stages of the menstrual cycle. Studies have shown that during these times when estrogen levels are high, women have fewer chest pain attacks.6, 7 In addition, smokers tend to have lower levels of nitric oxide in their blood vessels than nonsmokers, and smoking is a major risk factor for coronary spasm.
However, there is also research suggesting that the nitric oxide theory doesn't fully explain Prinzmetal's angina. Atherosclerosis, the hardening of the arteries caused by the buildup of fatty plaque, impairs the release of the artery-widening nitric oxide, but not everyone with atherosclerosis develops coronary artery spasms. Other suggested causes include problems in part of the nervous system (brain and spinal cord) or the muscle tissue involved in making the arteries narrow and widen. Another possibility is that injuries to the lining of the arteries expose the muscle to chemicals that cause the blood vessels to narrow.