Quantitative assessment of cardiac 123 iodo-metaiodobenzylguanidine SPECT/CT in patients with arrhythmogenic right ventricular cardiomyopathy: Novel insight in disease monitoring

The heart-to-mediastinum ratio (H/M-Ratio) of iodo-metaiodobenzylguanidine ( I-MIBG) represents state-of-the-art assessment for sympathetic dysfunction in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). This study aims to evaluate quantitative reconstruction of I-MIBG uptake and to demonstrate its correlation with echocardiographic parameters. Cardiac innervation was assessed in 23 patients diagnosed with definite ARVC or borderline ARVC and 12 patients with other cardiac disease presenting arrhythmia, using quantitative I-MIBG Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) imaging. Tracer uptake was evaluated in the left (LV) and right ventricle (RV) based on a CT scan after quantitative image reconstruction. The relationship between tracer uptake and echocardiographic parameter data was examined. Absolute quantification of I-MIBG uptake in the LV and RV is feasible and correlates accurately with the gold standard H/M Ratio. When comparing sensitivity and specificity, the area under the curve (AUC) favors standardized uptake value (SUV) of the RV over the right-ventricle-to-mediastinum-ratio (RV/M-Ratio) for diagnosing ARVC. A reduced RV-SUV in patients with definite ARVC is associated with reduced RV function. RV polar maps revealed globally reduced I-MIBG uptake without segment-specific reduction in the RV. Quantitative I-MIBG SPECT in ARCV patients offers robust potential for clinical reporting and demonstrates a significant correlation with RV function. Segmental RV analysis needs to be evaluated in larger samples. In summary, cardiac I-MIBG imaging using SUV could facilitate image-guided therapy in patients diagnosed with ARVC.