[Imaging diagnostics of cardiac sarcoidosis]

Cardiac involvement is clinically apparent in approximately 5% of all patients with systemic sarcoidosis, whereas evidence of cardiac involvement by imaging studies can be found in approximately 20% of cases. Occasionally, isolated cardiac sarcoidosis is encountered and is the only sign of the disease. The most frequent cardiac manifestations of the multifocal granulomatous inflammation include atrioventricular (AV) blocks and other conduction disorders, ventricular arrhythmias, sudden cardiac death and left and right ventricular wall disorders. Accordingly, symptoms that should raise suspicion include palpitations, lightheadedness and syncope. The diagnostic approach to cardiac sarcoidosis is not straightforward. Typical echocardiographic findings include regional thinning and contraction abnormalities particularly in basal, septal and lateral locations. Infrequently, myocardial hypertrophy may be present; however, the sensitivity of echocardiography is low and cardiac sarcoidosis can be present even when an echocardiogram is unrevealing. Cardiac magnetic resonance imaging (MRI) frequently shows late gadolinium enhancement (LGE) in a multifocal pattern often involving the basal septum and lateral walls. The sensitivity and specificity of MRI for detecting cardiac sarcoidosis are high. Fluorodeoxyglucose positron emission tomography (FDG-PET) plays an important role in the diagnostic algorithm due to its ability to visualize focal inflammatory activity both in the myocardium and in extracardiac locations. This may help target the optimal location for biopsy in order to obtain histologic proof of sarcoidosis and can also be used to follow the response to anti-inflammatory treatment. Notably, the sensitivity of endomyocardial biopsy is poor due to the patchy nature of myocardial involvement. In clinical practice, either histologic evidence of noncaseating granulomas from the myocardium or evidence from extracardiac tissue in combination with typical cardiac imaging findings are required to establish the diagnosis.