Clinical significance of quantitative assessment of right ventricular amyloid burden with [^99mTc]Tc-DPD SPECT/CT in transthyretin cardiac amyloidosis

Purpose: To evaluate right ventricular (RV) uptake measured by quantitative [^99mTc]Tc-DPD SPECT/CT to investigate its role in predicting and evaluating prognosis and therapeutic outcomes in patients with transthyretin amyloid cardiomyopathy (ATTR-CA).

Methods: Patients with ATTR-CA were consecutively enrolled for quantitative [^99mTc]Tc-DPD SPECT/CT. Ventricular amyloid burden was quantified by SUV_max and TBR. Differences in RV uptake (focal or diffuse) and associations with clinical characteristics and CMR data were evaluated. The primary endpoint was major adverse cardiac events (MACEs), including all-cause deaths, heart failure hospitalizations, complete atrioventricular block, sustained ventricular tachycardia, and atrial fibrillation/flutter. Prognostic associations were evaluated using Cox regression and Kaplan-Meier survival analysis. A secondary endpoint involved a longitudinal SPECT/CT analysis during Tafamidis therapy.

Results: The study included 76 patients, all showing both RV and LV uptake on SPECT imaging. Compared with patients with focal RV uptake, patients with diffuse RV uptake had higher serum troponin T levels (P < 0.05), septal thickness (P < 0.01), and external cardiac circulation volume (ECV) (P < 0.05). RV uptake was correlated with septal thickness, ECV, LV uptake, NT-proBNP and troponin-T (all P < 0.05). Among 53 patients, high LV and RV uptake significantly predicted MACEs (P < 0.001), with a median follow-up time of 16 months. A subgroup of 20 patients showed significant reductions in LV and RV uptake after Tafamidis treatment (P < 0.001).

Conclusion: Increasing RV amyloid burden quantified by SPECT/CT is associated with advanced disease stage and predicts MACEs, serving as valuable markers for prognosis and treatment monitoring in ATTR-CA.