P2743Right ventricular size in repaired tetralogy of Fallot: correlations between transthoracic echocardiography and cardiovascular magnetic resonance

Abstract

Abstract Introduction Right ventricular (RV) size informs about prognosis and need for pulmonary valve replacement in patients with repaired tetralogy of Fallot (rTOF). Cardiac magnetic resonance (CMR) is considered the reference standard for measurement of RV volumes. Despite known limitations for RV evaluation, 2D transthoracic echocardiography (TTE) remains the primary and most available imaging modality in the rTOF population. Purpose To determine which TTE RV size parameters best correlate with CMR-derived indexed RV end-diastolic (RVEDVi) and end-systolic (RVESVi) volumes in the rTOF population. We sought to determine the best TTE measurement thresholds to predict normal RV volume (RVEDVi ≤110 mL/m2) and significant RV dilatation by CMR (RVEDVi ≥150ml/m2). Method We retrospectively enrolled all rTOF patients followed at a single-center between 2010 and 2018 who had both TTE and CMR exams performed within a 12-month interval. All TTE exams were reviewed by an observer measuring RV areas, RV inlet and RV outlet at end-diastole and end-systole. Analyses of CMR studies were performed by 3 observers who measured RV area, RV inlet, RV outlet and RV volumes at end-diastole and end-systole. Correlations between TTE and CMR parameters were performed using Pearson correlation coefficients. Using the TTE RV parameters with the strongest correlation with CMR, we subsequently determined thresholds to predict a CMR RVEDVi ≤110ml/m2 and ≥150ml/m2 using ROC analysis. Results We enrolled 130 patients (59 women [45%], mean age 43±12.8 years). Median age at TOF repair was 4 [3–6] years; 18 patients (14%) had subsequent pulmonary valve replacement. Median interval between TTE and CMR exams was 114 [59–239] days. There were significant correlations between all TTE parameters and CMR RVEDVi. TTE indexed RV end-diastolic area (RVEDAi) most strongly correlated with CMR RVEDVi (r=0.73, p<0.0001). All TTE RV parameters significantly correlated with CMR RVESVi but indexed RV end-systolic area had the strongest correlation (r=0.77, p<0.0001). ROC analysis performed to predict RVEDVi of ≤110ml/m2 and ≥150ml/m2 using TTE RVEDAi revealed areas under the curve of 0.86±0.04 and 0.90±0.03, respectively. A TTE RVEDAi ≤17cm2/m2 predicted a normal CMR RV volume (≤110ml/m2) with a sensitivity of 90% and a specificity of 74%. A TTE RVEDAi ≥19cm2/m2 predicted a CMR RVEDVi ≥150 mL/m2 with a sensitivity of 93% and a specificity of 76%. Conclusion In rTOF patients, both diastolic and systolic TTE RV area best correlate with CMR-derived RV end-diastolic and end-systolic volumes. A cut-off value of TTE RVEDAi of 19cm2/m2 is 93% sensitive and 76% specific to predict a CMR RVEDVi ≥150ml/m2. Simple RV size measurement using TTE may help inform the need and frequency of CMR evaluations in rTOF patients.