Cardiac syndrome X is a condition in which patients have symptoms of coronary artery disease (CAD), including chest pain, but no evidence of blockages in the coronary arteries (e.g., atherosclerosis, or hardening and narrowing of the coronary arteries). Patients essentially suffer the pain of angina without CAD. The syndrome is more common in women, particularly those who are postmenopausal, and often occurs in relatively younger patients than those suffering from actual CAD.
There are a number of diagnostic tests that can help determine if an individual’s chest pain is due to cardiac syndrome X or CAD. These tests include an electrocardiogram (EKG), echocardiogram, stress test and coronary angiography. These tests can assess blood flow through the arteries and heart function to check for other possible causes of chest pain.
Treatment for cardiac syndrome X is aimed towards relieving chest pain. Patients may be prescribed cardiac medications such as nitrates, beta-blockers or channel blockers.
A number of possible causes have been proposed, but further research is necessary to understand the syndrome more completely. Possible causes include lack of blood flow to the heart (ischemia), hormone deficiencies and autonomic system imbalance.
Although the condition can affect patients physically and emotionally, cardiac syndrome X does not cause damage to the heart muscle and is not life-threatening.
About cardiac syndrome X
Like patients who have coronary artery disease (CAD), cardiac syndrome X patients report chest pain, often with exercise. They typically also experience pain during an exercise stress test, including bouts of chest pain that last longer than typical angina. However, this chest pain is not accompanied by any corresponding blockage in their coronary arteries, as confirmed by a cardiac catheterization. In other words, they show symptoms typical of CAD, but are not actually suffering from heart disease and are not at increased risk of heart attack or other cardiovascular conditions.
The causes and mechanisms of cardiac syndrome X are still largely unknown and can vary from patient to patient. However, researchers have identified certain patients who seem more prone to developing cardiac syndrome X. These include postmenopausal women and individuals who are younger than the typical patients with CAD. It may also be associated with psychiatric disorders, including anxiety.
Currently, there are several leading theories that attempt to explain the causes of cardiac syndrome X. It is important to note, however, that data on all of these possible causes is conflicted. At this time, the underlying causes Cardiac Syndrome X remain a mystery to researchers but some studies have linked it to conditions including:
Cardiac ischemia. A lack of oxygen-rich blood flow to part of the heart. Although there are conflicting data linking ischemia to cardiac syndrome X, this theory may explain why some people suffer from chest pain without actually having heart disease. According to some studies – although not all – the ischemia may be caused by problems with tiny vessels in the heart that are so slight they do not show up on normal cardiac tests such as the electrocardiogram (EKG). This hypothesis led to the use of the term microvascular angina as an alternative to cardiac syndrome X. Other nontraditional causes of cardiac ischemia may be spasm in the coronary arteries or abnormal constriction of the blood vessels due to high levels of a natural vasoconstrictor (endothelin). Physicians may be able to assess this type of ischemia with a relatively new imaging technique, myocardial-perfusion cardiovascular magnetic resonance imaging.
Abnormal pain perception. Another leading theory to explain cardiac syndrome X is enhanced pain sensitivity. In certain patients, cardiac pain is reported during procedures or situations that do not cause cardiac pain in healthy people. This might include exercise, or even the movement of a catheter in the right atrium or right ventricle, which should not cause ischemia or chest pain. Despite the pain, many patients do not show any other signs of heart disease, such as abnormal motions in the heart wall, a decline in function of the left ventricle or decreased blood flow to the heart.
Ischemia plus abnormal pain perception. Still other studies have suggested that cardiac syndrome X may be caused by a combination of the two previous conditions.
Autonomic system imbalance. The autonomic nervous system regulates all involuntary bodily functions, such as heart rate, sweating and digestion. It is divided into the sympathetic nervous system, which prepares the body for action, and the parasympathetic nervous system, which calms the body after a stress response. When functioning normally, the two systems are in balance. Cardiac syndrome X patients, however, often have an increased sympathetic drive, causing their bodies to be in “high gear” for prolonged periods of time. The precise reason for this and its connection to cardiac syndrome X is not known.
Metabolic syndrome. The link, if any, between cardiac syndrome X and metabolic syndrome (formerly known as metabolic syndrome X) is not yet known. One component of metabolic syndrome is insulin resistance, which has been found in some patients with cardiac syndrome X and other heart diseases.
Estrogen deficiency. For females, cardiac syndrome X could be linked to lower than normal estrogen levels in the body. This theory is partly due to the relationship between a lack of estrogen and abnormal levels of endothelin in the body. In addition, a significant number of patients with cardiac syndrome X are menopausal or post-menopausal women, who experience significant drops in estrogen levels. In addition, the exposure of women’s blood vessels to varying hormonal levels may increase the chances of microvascular changes in their vessels or arteries.
Diagnosis methods for cardiac syndrome X
A physician might suspect cardiac syndrome X in patients who suffer from prolonged bouts of chest pain (angina), sometimes as long as 10 minutes. These bouts of chest pain may occur after exercise or at rest. They may or may not respond to nitrates. From there, the diagnosis of cardiac syndrome X is a matter of ruling out coronary artery disease and other non-cardiac causes of the chest pain.
Typically, tests will be ordered, often beginning with an electrocardiogram (EKG) or exercise stress test. These tests may, or may not, have abnormal results.
The essential test to diagnose cardiac syndrome X is the cardiac catheterization test, including a coronary angiogram. A cardiac catheterization is used to examine the interior of the coronary arteries by inserting a catheter into a blood vessel in the body (usually in the groin) and advancing it to the heart. In CAD patients, the test reveals blockage of an artery that interferes with blood flow to the heart. Syndrome X patients, however, have no evidence of narrowing or blockage at cardiac catheterization. In general, a positive exercise stress test and a normal cardiac catheterization can confirm the diagnosis of Cardiac Syndrome X.
One new diagnostic approach is a 64 multislice CT scan, which utilizes a non-invasive approach to visualize the coronary artery. This test is very sensitive and reliable when the coronary arteries have no calcification present to interfere with the scan. However, 64-slice CT scanners are relatively rare and the coronary angiogram remains the gold standard test.
As part of the diagnostic approach, the following factors (which are associated with angina or chest discomfort and normal coronary arteries) are usually ruled out as causes or contributors before a diagnosis of cardiac syndrome X is made:
High blood pressure (hypertension).
Left ventricular hypertrophy. An increase in the size of the left ventricle due to growth of muscle tissue.
Valvular heart disease. Any dysfunction or abnormality in one or more of the heart’s four valves.
Esophageal spasm. An involuntary and abnormal contraction of the muscle fibers of the esophagus (the passageway from the throat to the stomach).
Treatment and prevention
During treatment for cardiac syndrome X, a physician will typically reassure patients that their condition is not dangerous. Chest pain can be a frightening condition, which may lead to elevated stress levels. It is important for patients with cardiac syndrome X to understand that their condition is not damaging their heart or life-threatening.
Studies have shown no or very minimal elevated risk of heart attack or heart disease due to cardiac syndrome X even after following patients for almost a decade. Additionally, studies have confirmed the positive health benefits of reassurance to patients who might be tempted to feel stress over their chest pain.
Beyond reassurance, the physician might prescribe certain medications to reduce or relive the chest pain:
Beta blockers slow the heart’s resting rate, as well as the rate during exercise, reduce the force of heart muscle contraction, thus lessening the heart’s workload.
Nitrates widen, or dilate, the walls of the blood vessels, allowing more blood (and therefore oxygen) to reach the heart. Nitrates have been found to relieve the symptoms of only 40 to 50 percent of cardiac syndrome X patients.
Calcium channel blockers (calcium antagonists) inhibit the influx of calcium into the cells. This reduces the concentration of calcium, which opens the coronary arteries and increases the heart’s blood flow. Calcium antagonists appear to be effective for many cardiac syndrome X patients.
Hormone replacement therapy may be prescribed for postmenopausal women. These medications are typically a form of estrogen and/or progestin and can be taken in a variety of forms, such as pills or skin patches. The relative risks and benefits of long-term use of HRT in cardiac syndrome X patients are unknown.
ACE inhibitors and statins may be prescribed in tandem. One small study has shown that the combination of these medications may improve cardiac blood flow and reduce symptoms of cardiac syndrome X, although exactly why is not fully understood.
Imipramine therapy may be used to control the chest pain. Imipramine is typically used to manage chronic pain and has been shown to reduce the pain associated with cardiac syndrome X.
Exercise may be recommended to reduce the symptoms and improve the patient’s physical conditioning. Some studies have suggested that cardiac syndrome X is linked with poor physical conditioning.
Due to the unpredictable nature of cardiac syndrome X, patients should be prepared to undergo trial-and-error treatments to find the one that produces the best result.
While not enough is known about cardiac syndrome X to list specific prevention techniques, adopting heart-healthy habits can be a good start. These include monitoring cholesterol and blood pressure levels, maintaining a low-fat diet, exercising regularly, quitting smoking, avoiding recreational drugs, and moderating alcohol intake. Patients should consult their physician before beginning a diet and/or exercise program.
Early studies suggest that individuals with cardiac syndrome X have no higher risk of suffering a heart attack or dying from cardiovascular conditions. However, the syndrome can negatively affect the quality of life. Chest pain may continue despite attempts at treatment, resulting in higher levels of anxiety, stress and depression among cardiac X syndrome patients.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to cardiac syndrome X:
Is my chest pain caused by a blockage in a coronary artery?
Do you suspect cardiac syndrome X based on my symptoms?
What tests will be used to confirm my diagnosis?
How soon do I need to have the tests?
Will the tests detect any other possible causes for my chest pain?
What are my treatment options?
What are the benefits and risks of these treatments?
What types of medications can you recommend for treating my condition?
Can I take cardiac medication and HRT at the same time?
How soon can I expect to get relief from treatment?
Will altering my lifestyle affect this condition in any way?
What symptoms would indicate a true heart emergency?
Can cardiac syndrome X interfere my pregnancy or delivery?
Will I have this condition for my entire life?
Does syndrome X place me at higher risk for other heart problems?
