Cardiac Sarcoidosis

Sarcoidosis is an autoimmune disease that produces granulomas—clumps of abnormal cells similar to scar tissue—in various organs, including the heart. When granulomas develop in the heart, they are known as cardiac sarcoidosis.

While cardiac sarcoidosis may be a relatively benign condition, sometimes it can cause severe clinical problems, including heart failure or sudden death. Diagnosing cardiac sarcoidosis and instituting appropriate treatment is critically important in these cases.

This article explores the symptoms, causes, and treatment of cardiac sarcoidosis and its impact on life expectancy.

What Is Sarcoidosis?

Researchers believe that sarcoidosis develops when the body’s immune system responds abnormally to some unknown substance (probably something that is inhaled), resulting in the formation of granulomas. Women are affected more frequently than men and Black people are much more likely to develop sarcoidosis than white people. A propensity for sarcoidosis can also run in families.

The symptoms of sarcoidosis are quite varied. Some people develop a flu-like condition with fatigue, fever, and weight loss. Others will have predominantly pulmonary symptoms such as cough, dyspnea (shortness of breath), or wheezing. Eye problems include redness, pain, blurred vision, and light sensitivity. Skin lesions may include a painful rash, sores on the face, changes in skin coloration, and nodules.

Any combination of these symptoms may occur. Some people with sarcoidosis develop no symptoms whatsoever, and the condition is diagnosed incidentally when a chest X-ray is done for some other reason.

What Is Cardiac Sarcoidosis?

Cardiac sarcoidosis occurs when sarcoid granulomas develop in the heart. As with other types of sarcoidosis, the manifestations of cardiac sarcoidosis vary from person to person. In some people, cardiac sarcoidosis causes no problems whatsoever; in others, it can be fatal.

The severity of cardiac sarcoidosis depends on the extent and the location of granuloma formation within the heart. About 5% of people with sarcoidosis are diagnosed with cardiac involvement during their lifetimes.

However, in autopsy studies, as many as 70% of people with sarcoidosis turn out to have at least some cardiac granulomas. This suggests that cardiac sarcoidosis usually does not produce identifiable clinical problems.

However, When sarcoidosis produces cardiac problems, those problems can be severe.

Cardiac Sarcoidosis Symptoms

The problems produced by cardiac sarcoidosis depend on where granulomas appear in the heart. The most common manifestations of cardiac sarcoidosis include:

• Heart block: Complete heart block, producing severe bradycardia (slowing of the heart rate), can occur when granulomas are formed within the heart's specialized conducting tissues. Symptoms of heart block may include severe lightheadedness, syncope (transient loss of consciousness), or even sudden death. 
• Cardiac arrhythmias: Premature ventricular complexes (PVCs) or ventricular tachycardia are common in cardiac sarcoidosis. Atrial arrhythmias, including atrial fibrillation, can also occur. These arrhythmias develop due to granulomas that form in the heart muscle.
• Sudden death: Because of either heart block or ventricular tachycardia, sudden death is disturbingly common in cardiac sarcoidosis and accounts for roughly 50% of the deaths caused by this condition.
• Heart failure: Heart failure can develop in cardiac sarcoidosis when granuloma formation within the heart muscle becomes extensive.
• Pericardial disease: Pericarditis or pericardial effusions can occur due to granulomas in the pericardial lining of the heart. 
• Valvular heart disease: Granulomas affecting the heart valves may cause mitral regurgitation, tricuspid regurgitation, or, more rarely, aortic regurgitation. 
• Heart attacks: Sarcoid granulomas may affect the coronary arteries, producing the death of portions of the heart muscle—heart attacks. 
• Right-sided heart failure: Severe pulmonary sarcoidosis can cause pulmonary hypertension, leading to right-sided heart failure.

Diagnosing Cardiac Sarcoidosis

Making a diagnosis of cardiac sarcoidosis is often tricky. The most definitive test is a positive cardiac biopsy. However, not only is a biopsy an invasive procedure but also (because sarcoid granulomas are randomly distributed), a biopsy may come back “normal” even when cardiac sarcoidosis is present.

This means that, typically, the diagnosis of cardiac sarcoidosis is made by weighing the evidence from several different diagnostic approaches.

First, doctors need to know when they should look for cardiac sarcoidosis. Looking for cardiac sarcoidosis is essential for people known to have sarcoidosis, which affects other body organs. Also, cardiac sarcoidosis should be thought of in any young person (under age 55) who develops heart block, ventricular arrhythmias, or heart failure for unexplained reasons.

If cardiac sarcoidosis is a diagnosis that ought to be considered, doing an echocardiogram is typically the first noninvasive test performed. This test often reveals important clues if cardiac sarcoidosis is present, including, in some cases, characteristic echo signals produced by granulomas within the cardiac muscle.

However, a cardiac MRI scan is much more likely to show evidence of sarcoid granulomas within the heart and is typically the noninvasive test of choice. PET scans of the heart are also quite sensitive for detecting cardiac sarcoid granulomas, but PET scans are less readily available than MRI scans.

The gold standard for diagnosing cardiac sarcoidosis is a heart muscle biopsy, which can be performed during cardiac catheterization. However, as already noted, detecting granulomas by this method, even when they are present, is accomplished less than half the time.

In most cases, based on a combination of clinical signs and symptoms, noninvasive and invasive testing, determining the presence or absence of cardiac sarcoidosis can be accomplished with a high degree of confidence.

Cardiac Sarcoidosis Treatment

If cardiac sarcoidosis is present, treatment aims to slow or stop the progression of the sarcoidosis itself and to prevent or treat the direst cardiac consequences of this disease.

Preventing Granulomas

Therapy aimed at the sarcoidosis itself attempts to suppress the immune reaction that causes the formation of granulomas. In sarcoidosis, this is usually done with glucocorticoid (steroid) therapy, most commonly with prednisone. Often, high doses are prescribed initially (40-60 milligrams per day). Over the first year, this dose is gradually reduced to 10-15 milligrams daily and continued for at least one or two years.

If re-evaluation shows that the sarcoidosis has become stable (that is, there is no further evidence of granuloma formation anywhere in the body and resolution of any symptoms caused by the sarcoidosis), it may be possible to eventually stop steroid therapy.

In people who do not appear to respond to steroid therapy, other immunosuppressants may be necessary, such as chloroquine, cyclosporine, or methotrexate.

Treating Cardiac Sarcoidosis

The most dreaded consequence of cardiac sarcoidosis is sudden death, caused either by heart block or ventricular tachycardia. A permanent pacemaker should be implanted in anyone with cardiac sarcoidosis in whom signs of developing heart block are seen on an electrocardiogram.

Implantable cardioverter-defibrillators (ICDs) may be used to prevent sudden death from ventricular arrhythmias. However, professional societies have been unable to develop clear-cut guidelines regarding which people with cardiac sarcoidosis should receive ICDs. Most experts recommend them for people with sarcoidosis who have significantly reduced left ventricular ejection fractions or who have survived episodes of sustained ventricular tachycardia or ventricular fibrillation.

In addition, performing an electrophysiology study can help in determining which people with cardiac sarcoidosis are at exceptionally high risk for sudden death from ventricular arrhythmias and, thus, who ought to have an ICD.

If valvular heart disease caused by cardiac sarcoidosis is present, surgery ought to be considered using the same criteria employed for anyone else with heart valve problems.

If heart failure occurs, people with cardiac sarcoidosis should receive the same aggressive treatment for heart failure that is used for anyone with this condition. If their heart failure becomes severe and does not respond any longer to medical therapy, they should receive the same consideration for heart transplantation given to anyone else with heart failure. Their outcomes after cardiac transplantation appear to be better than the outcomes reported for people having transplantation for other underlying causes.

Summary

Cardia sarcoidosis is a potentially serious, but also sometimes benign condition where granulomas form on heart tissue.

As is the case with sarcoidosis in general, sarcoidosis affecting the heart can have a range of manifestations, from entirely benign to lethal. If there is a reason to suspect cardiac sarcoidosis, it is essential to do the testing necessary to make or rule out the diagnosis. Early and aggressive therapy (both for the sarcoidosis and its cardiac manifestations) can significantly improve the outcome for a person with cardiac sarcoidosis.