Discussion
Sarcoidosis is a multisystem granulomatous disease, which predominantly affects 20- to 30-year olds of both sexes. Most patients present with pulmonary involvement. In addition to the lungs, other affected organs are, in decreasing order of frequency, skin, liver, gastrointestinal tract, eyes and nervous system. Cardiac involvement is one of the least common manifestations. In a recent review, the incidence of clinical heart involvement was reported as approximately 5%, whereas at autopsy the incidence was considerably higher (20 to 25%).
The course of sarcoidosis can be indolent; however, acute complications in cardiac sarcoidosis can lead to sudden cardiac death. Non-caseating granulomas serve as foci for abnormal automaticity and cause changes in the ventricular activation and recovery process, which explains the reentry mechanism that is thought to lead to VT in cardiac sarcoidosis.
Ante mortem diagnosis of cardiac sarcoidosis is difficult because of its wide-ranging clinical manifestations and the limitations of available diagnostic tests. Guidelines for the diagnosis of cardiac sarcoidosis have been published by the Japanese Ministry of Health and Welfare although they have not been validated (see section Guidelines for the diagnosis of cardiac sarcoidosis). Although possible cases of cardiac sarcoidosis should initially have an echocardiogram to look for supportive findings such as regional wall motion abnormalities, thickening of IVS with bright shadow consistent with infiltration and impaired left ventricular EF, these findings are not specific. Cardiac MRI with gadolinium enhancement and PET scanning are valuable aids in the diagnosis of myocardial sarcoidosis and are considered superior to gallium-labeled or technetium-labeled nuclear scans. Reports suggest that the sensitivity of detecting sarcoid granuloma on endomyocardial biopsy is around 20%; hence a negative biopsy does not exclude the disease.
Sarcoidosis that involves the heart warrants prompt treatment with corticosteroids with or without other immunosuppressive agents. A recent study showed that corticosteroids are more helpful in patients with mild to moderate left ventricular function impairment (left ventricular EF of 30 to 50%), whereas those with a severely reduced left ventricular EF of less than 30% in the late stage of disease did not benefit (probably because of irreversible myocardial damage and fibrosis). This is in keeping with our case where the patient presented in the late stages and did not show a response to steroids.
Ventricular arrhythmias are common in cardiac sarcoidosis but are often refractory to antiarrhythmic drugs including amiodarone. Most authorities recommend placement of an electronic pacemaker for complete heart block and an automatic implantable cardioverter-defibrillator for ventricular fibrillation or tachycardia and markedly reduced left ventricular EF. Cardiac transplantation is a useful option in cardiac sarcoidosis refractory to medical management, however, some studies have shown a trend towards increased mortality. However, with progress in prevention and treatment of ventricular arrhythmias, the primary cause of death in cardiac sarcoidosis has changed from sudden death to congestive heart failure.