F-FDG PET scan as follow-up tool for sarcoidosis with symptomatic cardiac conduction disturbances requiring a pacemaker.

A 45-year-old man presented to the emergency room after three syncopes. ECG showed sinus rhythm with complete right bundle branch block and left anterior fascicle block. Echocardiography and 24 h ECG monitoring were normal. Chest radiography showed small patchy infiltrations and spiro-ergometry tests showed normal carbon monoxide transfer factor but a reduction in physical capacity (maximum oxygen consumption 70%) associated with an effort-related grade II atrioventricular block. An MRI scan of the heart using gadolinium showed enhancement at the anteroseptal level (fig 1A), and 18F-FDG positron emission tomography (PET) showed focal uptake at exactly the same location (fig 1B). Transbronchial biopsy specimens showed typical granulomas and bronchoalveolar lavage revealed lymphocytosis of 26% and a CD4/CD8 quotient of 7.5, both compatible with sarcoidosis. Figure 1 (A) Gadolinium-enhanced MRI scan of the heart (short axis) showing delayed enhancement in the anteroseptal myocardium. (B) 18F-FDG positron emission tomography (PET) scan of the heart (short axis) showing focal uptake in the anteroseptal wall (same location ... A DDD pacemaker was implanted and steroid treatment was started. Since MRI was no longer feasible because of the pacemaker, an 18F-FDG PET scan was performed at 3 months follow-up (fig 1C) which showed complete disappearance of the focal uptake. These changes correlated with disappearance of the chest radiographic findings and recovery from the grade II effort-dependent atrioventricular block with an increase in maximum oxygen consumption from 24.9 to 33.3 ml/kg/min. Learning points Monitoring cardiac involvement of sarcoidosis without clear structural changes can be difficult and, if a pacemaker is needed, an MRI scan of the heart cannot be used as a follow-up tool. An 18F-FDG PET scan seems to correlate very closely with the granulomatous inflammation and is therefore promising as a follow-up tool to guide immunosuppressive treatment.