Sarcoidosis is a rare inflammatory condition, where clusters of inflammatory cells, known as 'granulomas' form in various organs in the body and cause organ dysfunction. Common organs involved include the lungs, lymph nodes and the nervous system.

In a minority of patients with sarcoidosis, these clusters of inflammatory cells form in the heart tissue, resulting in 'cardiac sarcoidosis'. The granulomas that form in the heart tissue can disrupt normal electrical impulse conduction within the heart, or cause weakening of the heart muscles.

The cause of sarcoidosis is currently not known but is probably related to immune system overreacting to various external triggers (such as viruses, foreign allergens). 

• Palpitations (sensation of 'abnormal heartbeats')
• Unexplained giddiness/ fainting spells
• Unexplained fatigue
• Shortness of breath
• Chest pain
• Fluid retention in legs/ abdomen

The symptoms of cardiac sarcoidosis are notoriously non-specific, posing a diagnostic challenge for doctors seeing the patient.

Cardiac sarcoidosis is diagnosed by cardiologists, by integrating various clinical information, including

• Patient symptoms
• Clinical examination findings
• Signs of heart failure/ irregular heart rate
• Electrocardiogram ('ECG')
• Electrical tracing of the heart, looking for signs of abnormalities in the heart electrical conduction system
• Chest radiograph
• X-ray examination of the lungs, looking for sarcoidosis of the lungs/ chest lymph nodes
• Echocardiogram
• Ultrasound examination which allows doctors to assess heart function and look for typical features of cardiac sarcoidosis
  
• Cardiovascular magnetic resonance imaging ('Cardiac MRI')
• Specialised scan looking specifically at the heart muscles, to look for evidence of heart muscle inflammation in a pattern consistent with cardiac sarcoidosis
  
• Positron emission tomography (PET) scan
• Specialised nuclear scan to look for areas of active inflammation in the heart, which can suggest active sarcoidosis
  
• Endomyocardial biopsy
• Invasive procedure performed through a vein puncture, which allows for sampling of heart muscles. The heart muscle samples will then be examined under the microscope to look for granulomas, which can be diagnostic of cardiac sarcoidosis

​Management of patient's heart complications

In patients with cardiac sarcoidosis causing electrical conduction abnormalities, a permanent pacemaker or implantable cardiac defibrillator might be necessary. In patients with heart muscle weakness and fluid retention, specific medications for heart failure might be started, with the hope of improving heart function.

Treatment of inflammation

The definitive treatment of cardiac sarcoidosis would be to stop the active inflammation mediated by the granulomas present in the heart. Medications that suppress the overactive immune system are often started in patients with cardiac sarcoidosis, to reverse the disease process.

The Cardiomyopathy Clinic at the National University Heart Centre, Singapore (NUHCS) provides a comprehensive evaluation and treatment service for patients diagnosed with cardiac sarcoidosis.

Panel A: Positron emission tomography (PET) scan showing inflammation in the heart muscle (black arrows), in a patient with cardiac sarcoidosis.

Panel B: Regression of the active inflammation (white arrow) in the same patient, following a period of treatment with medications that suppress the immune system.