Overview of Cardiac Sarcoidosis

Sarcoidosis is a disease of unknown cause that produces granulomas—clumps of abnormal cells similar to scar tissue—in various organs in the body. These granulomas can interfere with the normal functioning of the affected organs, and thus can produce a dizzying array of symptoms and medical problems. Because the sarcoid granulomas can be so widespread, people with this condition can experience symptoms involving the lungs, eyes, skin, nervous system, gastrointestinal system, endocrine glands—and the heart.

When cardiac sarcoidosis occurs it can be difficult to diagnose. While cardiac sarcoidosis may be a relatively benign condition, sometimes it can cause severe clinical problems, including heart failure or sudden death. In these cases, making the diagnosis of cardiac sarcoidosis, and instituting appropriate treatment is critically important.

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, or wheezing. Eye problems can 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 is the case with sarcoidosis in general, the manifestations of cardiac sarcoidosis are quite variable 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. Generally, fewer than 10% of people with sarcoidosis are diagnosed with cardiac involvement during their lifetimes.

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

When sarcoidosis does produce cardiac problems, however, those problems can be severe.

Signs and Symptoms

The problems produced by cardiac sarcoidosis depend on where in the heart the granulomas appear. 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 specialized conducting tissues of the heart. Symptoms of heart block may include severe lightheadedness or 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 as a result of 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 or 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.

Diagnosis

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 as “normal” even when cardiac sarcoidosis is actually present.

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

First, it is important for doctors to know when they should look for cardiac sarcoidosis. Looking for cardiac sarcoidosis is important in people who are known to have sarcoidosis affecting other organs of the body. 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 non-invasive 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 non-invasive 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 biopsy of the heart muscle, which can be performed during cardiac catheterization. However, as already noted, detecting granulomas by this method, even when they are present, is successfully accomplished less than half the time.

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

Treatment of Cardiac Sarcoidosis

If cardiac sarcoidosis is present, treatment is aimed both at slowing or stopping the progression of the sarcoidosis itself, and at preventing or treating the direst cardiac consequences of this disease.

Treating the Sarcoidosis Itself: 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 mg per day). Over the first year, this dose is gradually reduced to 10-15 mg per day and is continued for at least one or two years.

If re-evaluation shows that the sarcoidosis has become stable (that 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 the Cardiac Manifestations of 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. Professional societies have been unable to develop clear-cut guidelines regarding which people with cardiac sarcoidosis should receive ICDs. However, most experts recommend them in 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 particularly 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, people with sarcoidosis should receive the same consideration for heart transplantation given to anyone else with heart failure. In fact, their outcomes after cardiac transplantation appear to be better than the outcomes reported for people having transplantation for other underlying causes.

A Word From Verywell

As is the case with sarcoidosis in general, sarcoidosis affecting the heart can have a whole range of manifestations, from completely benign to lethal. If there is a reason to suspect cardiac sarcoidosis, it is important to do the testing necessary to make or rule out the diagnosis. For a person who has cardiac sarcoidosis, early and aggressive therapy (both for the sarcoidosis itself and for its cardiac manifestations) can greatly improve the outcome.