Prinzmetal’s angina (also known as variant angina) is a clinical syndrome characterized by episodes of anginal chest pain without provocation, usually at rest. It occurs more in women and is associated with a transient ST-segment elevation on ECG (electrocardiography). It was described as a variant form of angina in 1959 by the American cardiologist Myron Prinzmetal.
The only symptom of Prinzmetal’s angina is recurrent episodes of chest pain. Chest pain is often extremely severe. It usually occurs at rest, rather than on exertion (thus attacks often occur at night or early morning) and is promptly relieved by nitroglycerin. Rarely, syncope or even cardiac arrest may present along with chest pain because patients with Prinzmetal’s angina may experience dangerous arrhythmia during their attacks.
Prinzmetal’s angina is caused by a transient focal spasm of a major coronary artery. Focal spasm causes a marked, but temporary reduction in coronary artery luminal diameter that significantly obstructs the coronary blood flow. As a result, heart muscle gets inadequate oxygen and produces severe chest pain.
Focal spasm is more common in right coronary artery and may occur at one or more places in one artery or in multiple arteries simultaneously. It may occur in either a normal or diseased coronary artery. In about half the patients there is an associated atherosclerotic plaque at the site of the spasm.
The exact cause of focal coronary spasm is not well established. Vascular smooth muscle hyper-contractility is thought to be central to the pathogenesis of Prinzmetal’s angina. In some cases it is a presentation of a vasospastic disorder such as Raynaud’s phenomenon, migraine headache or aspirin induced asthma.
Some factors may increase the risk of developing Prinzmetal’s angina that are –
- Cigarette smoking
- Exposure to cold weather
- Use of cocaine
- Use of vasoconstricting drug.
Patients with Prinzmetal’s angina are generally younger and chest pain is often extremely severe. Physical examination findings of the heart are often normal. The clinical diagnosis is made by observing transient ST-segment elevation on ECG during the attack of chest pain.
Figure: ECG finding of Prinzmetal’s angina
Small elevations of cardiac markers such as troponin and CK-MB may occur in patients with prolonged attack. ETT (exercise tolerance test) is of no value in the diagnosis of Prinzmetal’s angina.
The gold standard test is coronary angiography with administration of provocative agent into the coronary artery. Usually, ergonovine is used as a provocative agent (methylergonovine or acetylcholine can also be used). Ergonovine 50 microgram at 5-minute intervals is given intravenously until a positive result or a maximum dose of 400 microgram has been administered. Exaggerated spasm of coronary artery is the diagnostic hallmark of Prinzmetal’s angina.
Following complications may occur:
(1) Myocardial infarction – It may develop if the coronary spasm cannot be reversed.
(2) Arrhythmias – Patients with Prinzmetal’s angina may develop life threatening arrhythmias during episodes of pain.
Immediate and adequate treatment greatly reduces the risk of above complications.
Treatment of Prinzmetal’s angina includes:
Nitrate – Nitrate is a vasodilator drug. It dilates the coronary artery and relief symptom immediately. Short-acting nitrate especially sublingual or intravenous nitroglycerine is used for acute episodes whereas the long-acting nitrate is used to prevent recurrences.
Calcium channel blocker – Calcium channel blocker such as amlodipine, nifedipine, verapamil or diltiazem is extremely effective in preventing the spasm of coronary artery in Prinzmetal’s angina.
Potassium channel activator – Potassium channel activator, nicorandil is a vasodilating drug. It is effective in preventing the episodes of coronary artery spasm.
Rho-kinase inhibitor – Fasudil hydrochloride is a rho-kinase inhibitor and has a vasodilator property. It has also been shown to be effective in preventing the episodes of coronary artery spasm in Prinzmetal’s angina.
Use of a beta-blocker is contraindicated in Prinzmetal’s angina.
The prognosis of Prinzmetal’s angina is good when there is no significant coronary artery blockage by atherosclerosis. It is a chronic condition. Therefore, regular follow up is needed. When it is associated with coronary artery atherosclerosis, prognosis is determined by the severity of underlying heart disease.