Positron emission tomography predicted recovery of complete A-V nodal dysfunction in a patient with cardiac sarcoidosis.

A36-year-old man was admitted to our hospital because of exertional dyspnea and syncope. The ECG showed complete A-V block (Figure 1A), and a pacemaker was implanted. Although his chest X-ray did not detect bilateral hilar lymph node enlargement, his acute clinical course with complete A-V block suggested cardiac sarcoidosis. Thus, we performed thoracic computed tomography, which revealed multiple enlarged paratracheal lymph nodes. Pathological examination of one lymph node showed noncaseating granulomas, consistent with sarcoidosis (Figure 2). Radionucleotide scintigram of myocardium showed decreased uptake of thallium in the basal septal segment. Cardiac fluorine-18deoxyglucose (18FDG)/nitrogen-13-ammonia (13NH3) positron emission tomography (PET) also showed strongly enhanced 18FDG uptake in the basal septal segment, which is a site of the A-V nodal pathway, and reduced 13NH3 uptake in the same region (Figures 3A and 3B). Ga-citrate wholebody scintiscan revealed increased activity in the inferoposterior myocardial segment but not in the basal septal segment. Given these results, we diagnosed cardiac sarcoidosis and administered prednisolone acetate (40 mg daily). Thirty days after the initiation of steroid therapy, we performed a second cardiac PET scan. Surprisingly, the elevated 18FDG uptake in the basal anteroseptal segment had clearly disappeared and the reduced 13NH3 uptake in this region normalized, indicating that steroid therapy had improved the flow metabolism mismatch (Figures 3C and 3D). However, the 201-thallium scintiscan on nearly the same day of the second PET scan showed no definitive change. Ga-citrate scintiscan revealed that the increased uptake in the inferoposterior myocardium disappeared at the time of the second PET scan; however, abnormal Ga uptake or changes in Ga uptake pattern were seen in the basal septal segment, which is the site of the A-V nodal pathway. Complete A-V block did not change at the time of the second cardiac PET scan, but surprisingly, it had improved to a first degree A-V block 20 days after the second PET scan (Figures 1B and 1C). This case strongly suggests that 18FDG/13N-ammonia PET is a useful tool, not only for the diagnosis of cardiac sarcoidosis, but also for the predication of improvement of A-V nodal dysfunction, which is sometimes associated with this disease along with left ventricular dysfunction.