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

Purpose: The heart-to-mediastinum ratio (H/M-ratio) of ¹²³iodo-metaiodobenzylguanidine (¹²³I-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 ¹²³I-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 ¹²³I-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 ¹²³I-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 ¹²³I-MIBG uptake without segment-specific reduction in the RV.

Conclusion: Quantitative ¹²³I-MIBG SPECT in ARCV patients offers robust potential for clinical reporting and demonstrates a strong correlation with RV function. Segmental RV analysis needs to be evaluated in larger samples. In summary, cardiac ¹²³I-MIBG imaging using SUV could facilitate image-guided therapy in patients diagnosed with ARVC.

Clinical Perspective

Quantitative cardiac ¹²³I-MIBG SPECT/CT is technically feasible for image-guided surveillance of ARVC patients. RV-SUV values correlates well with functional echocardiographic parameters.

The assessment of the left and right ventricle separately offers a promising novel diagnostic opportunity of moving from the current clinical standard of H/M ratio to absolute quantification of ¹²³I-MIBG SPECT/CT imaging.