Cardiac Syndrome X

Cardiac syndrome X is a condition where patients with no physical findings of coronary artery disease (CAD) experience angina. Patients with cardiac syndrome X have symptoms of CAD, but their coronary arteries are clear of blockages. It is not clear what causes syndrome X, but several theories are being explored. Syndrome X patients do not seem to have a higher risk of dying early or having a heart attack, but they often continue to suffer from chest pain even after treatment. Syndrome X is more common in women than men: about 70% of patients are women who are approaching or have already gone through menopause.


Patients with cardiac syndrome X experience the pain of angina. Chest pain associated with syndrome X is less predictable and can occur during exercise, after exercise, or at rest. Patients with syndrome X may experience chest pain more often, more intensely, and for longer periods than patients with stable angina. In addition, nitroglycerin usually relieves chest pain in stable angina patients but often does not work in patients with syndrome X. Strictly speaking, syndrome X is a type of unstable angina because the pain may occur at rest.

What Causes Cardiac Syndrome X?

No one knows exactly what causes syndrome X, and it is unlikely to have a single cause. Several theories exist with regard to what causes cardiac syndrome X. Some researchers attribute it to enhanced pain perception; others propose that it is linked to low levels of the female hormone estrogen. New research has shown that it is most likely caused by microvascular angina. In microvascular angina, the smallest capillaries in the heart narrow or constrict. This tightening reduces the blood flow in the heart and causes the pain of angina. But because these capillaries are so tiny, they do not increase the risk of heart attack. They are also too small to detect with the standard tests that doctors would normally use to see larger vessels. About 50% of women with syndrome X have evidence of microvascular dysfunction, but only about 20% to 25% show signs of restricted blood flow to the heart, suggesting that other factors are involved. Syndrome X patients generally have good survival rates, whereas patients with true myocardial ischemia are at increased risk of having a heart attack or dying from heart disease.


The tests that differentiate cardiac syndrome X from CAD include a baseline electrocardiogram (ECG), an exercise ECG or stress test, an exercise nuclear stress test, echocardiography, and coronary angiography. When patients with cardiac syndrome X undergo an exercise stress test, the results may look the same as patients who have CAD. But coronary angiography procedures, which look for blockages in the coronary arteries, show the arteries of patients with syndrome X as clear and normal. Patients may also be evaluated for other conditions that could be causing the symptoms, including high blood pressure or heart valve disease.


Several different types of medicine may relieve the angina pain associated with cardiac syndrome X, including nitroglycerin, beta blockers, and calcium channel blockers


Texas Heart Institute

Cardiovascular Research Foundation