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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.