What Is Cardiac Sarcoidosis?
Cardiac sarcoidosis is a rare disease in which clusters of white blood cells, called granulomas, form in the tissue of the heart. Any part of the heart can be affected, though these cell clusters most often form in the heart muscle where they can interfere with the heart’s electrical system (conduction defects) and cause irregular heartbeats (arrhythmias). Cardiac sarcoidosis can also result in heart failure.
The disease tends to affect younger people, generally between 25 and 45 years old.
Most people diagnosed with cardiac sarcoidosis also have granulomas in other organs of the body, most commonly in the lungs (pulmonary sarcoidosis).
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Causes
The causes of cardiac sarcoidosis are not currently known. The disease may be triggered by an over-reaction of the immune system after exposure to an infectious agent (such as bacteria or viruses), chemical, or allergen. It is thought that this causes excessive inflammation and the clustering of white blood cells.
Cardiac sarcoidosis and other types of sarcoidosis may have a genetic component. People who have a parent or sibling with sarcoidosis are about five times more likely to contract sarcoidosis as people without an affected family member.
Diagnosis
Cardiac sarcoidosis can be very difficult to diagnose. The heart is affected in about 5% of patients who have systemic sarcoidosis. Tests that may be used to diagnose cardiac sarcoidosis include:
- Echocardiogram: to look for abnormalities in the heart muscle and heart valves
- Electrocardiogram: to identify problems with heart rhythm
- Holter monitor: to continuously monitor the heartbeat over one or two days to look for rhythm disturbances
- Nuclear imaging, such as positron emission tomography (PET): to measure inflammation and activity in different areas of the heart, using tiny amounts of radioactive compounds
- Cardiac magnetic resonance imaging (MRI): to look for abnormalities in the heart
- Tissue biopsy: to look for the presence of granulomas. This is done by taking a small tissue sample from the heart through a vein
Treatments
Sarcoidosis is usually a benign, self-limiting disease that requires no treatment. When needed, treatment for cardiac sarcoidosis focuses on reducing inflammation in the body and managing the heart problems caused by the granulomas. The disease cannot be cured, but its effects often can be successfully managed. Treatment for cardiac sarcoidosis includes:
Corticosteroids
These drugs suppress the immune system to reduce inflammation. Some patients diagnosed with cardiac sarcoidosis may need to take corticosteroids for the rest of their lives, while some may be able to taper off the drugs after an initial treatment period.
Other Immunosuppressive Drugs
These drugs can include methotrexate and cyclophosphamide.
Anti-arrhythmic Drugs
These drugs reduce the occurrence or severity of arrhythmias.
Catheter Ablation
Some arrhythmias caused by cardiac sarcoidosis may need to be treated with a minimally invasive technique called radio-frequency ablation to block abnormal electrical signalling pathways in the heart.
Implantable Cardioverter Defibrillator (ICD)
An ICD is similar to a pacemaker but can deliver an electrical shock, when needed, to restore normal heart rhythms. An ICD may be necessary for patients with more dangerous arrhythmias which can stop the heartbeat, such as ventricular fibrillation.