Sarcoidosis is an inflammatory disease involving any organs of the body characterized by non-caseating granuloma. Lung involvement is most common and followed by skin and lymph node.
Cardiac sarcoidosis (CS) can be diagnosed as a part of systemic sarcoidosis or detected alone. Several studies described variable range of myocardial involvement in patients with systemic sarcoidosis; 2-5% in retrospective study of systemic sarcoidosis patients and 25-75% in autopsy studies. Disease spectrum is wide from incidental finding to life-threatening complications, such as high degree atrioventricular (AV) block, heart failure and sudden cardiac death.
CS can cause various arrhythmias and heart failure. Asymptomatic cardiac involvement is detected by work up of systemic sarcoidosis involving other organs.
Complete AV block is most common finding in clinically evident CS and has been reported in 23-30% of CS. Ventricular tachycardia is one of the most frequent arrhythmia reported in CS patients. Complete AV block and ventricular tachycardia is caused by myocardial infiltration of granuloma, which account for the high prevalence of sudden cardiac death in CS patients. Heart failure is a consequence of extensive cardiac infiltration of granuloma, and accounts for 25-75% of cardiac deaths in patients with CS. Pericardial effusion, secondary mitral regurgitation due to left ventricular involvement, ventricular aneurysm and pulmonary hypertension can be detected.
When CS is suspected in patients with systemic sarcoidosis, electrocardiogram (ECG) and echocardiography are the first diagnostic test. Abnormal ECG such as AV block and bundle branch block is found in 50% of patients with systemic sarcoidosis, but is often nonspecific. Echocargiography is a key diagnostic tool to diagnose CS, because endomyocardial biopsy showed low sensitivity for non-caseating granuloma. Regional wall motion abnormality inconsistent with coronary artery territory is a clue for the diagnosis of CS, and basal septum, posterior and lateral wall is most commonly involved. Global left ventricular dysfunction mimicking dilated cardiomyopathy can be seen in end-stage CS. Cardiac magnetic resonance and positron emission can also assist the diagnosis of CS. Endomyocardial biopsy is needed for the definite diagnosis of CS. However, the diagnostic yield of non-caseating granuloma is about 20%.
Figure 1. Echocardiography of 56-year old male diagnosed with cardiac sarcoidosis. Dyskinesia of basal anteroseptal wall is shown.
Figure 2. Myocardium involved with cardiac sarcoidosis showing non-caseating, multinucleated giant cell granuloma (Modified from Heart.2006;92(2):282–288.)
The mainstay of CS treatment is immunosuppression, and prednisolone is commonly used. In addition, implantable cardioverter-defibrillator is needed in patients who experienced sudden cardiac arrest or ventricular tachyarrhythmia for secondary prevention. Medication for heart failure is also important in CS with systolic dysfunction.
Once symptom is revealed in patients with CS, the prognosis is poor.