Strain analysis by feature-tracking CMR helps to objectively quantify global and regional RV dysfunction and RV dyssynchrony in patients with ARVC and provides incremental value over conventional cine CMR imaging.

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Background: Quantification of RV volumes is problematic owing to variable reproducibility. CMR has the ability to more comprehensively survey the entire RV, including the RVOT, which commonly contributes to RV dilatation in ToF and is often less well seen on echocardiography.Aims: We aimed to determine the inter-observer reproducibility of CMR-derived RV volumes generated by two independent and experienced (SCMR Level III) observers in ToF patients with varying degrees of RV dilatation.Methods: We performed a retrospective analysis of 120 consecutive patients with repaired ToF who underwent CMR. Two blinded observers calculated RV volumes in each oblique short axis slice independently. Bland-Altman analysis and inter-observer correlation coefficients (ICC) were assessed.Results: Patients were either: 1) mild-moderate RV dilatation with indexed RV end-diastolic volume RVEDVi<150ml/m 2 (n=71, 50%male, mean age 24±10 years); or 2) severe RV dilatation with RVEDVi>150ml/m 2 (n=49, 59%male, mean age 27±12 years). Between observers the mean RVEDVi difference in group 1 was 1.8±3.9ml/m 2 (95% limit of agreement -5.7 to 9.4, ICC 0.97). For group 2, the RVEDVi mean difference was 3.4±6.1ml/m 2 (95% limit of agreement -8.6 to 15.4, ICC 0.98). Good agreement was also observed for indexed RV end-systolic volume (2.5±5.7, 95% limit of agreement -8.6 to 13.65, ICC 0.98) and RV ejection fraction (-0.7±2.3, 95% limit of agreement -5.3 to 3.9, ICC 0.97).Conclusions: In patients with repaired ToF and variable degrees of RV dilatation, CMR assessment of RV volumes and function has high inter-observer reproducibility. This has implications for decisions about the timing of pulmonary valve replacement.