Short-Axis Diastolic Ventricular Area Ratio as a New Index in Screening Patients with Repaired Tetralogy of Fallot

Right ventricular (RV) end-diastolic volume measured by cardiovascular magnetic resonance imaging (CMR) is a criterion for pulmonary valve replacement in patients with tetralogy of Fallot (TOF). We sought to determine if the ratio of echocardiographic, short-axis RV-to-left ventricular (LV) end-diastolic areas (EDA) could be used to predict RV volume on CMR. We retrospectively reviewed the echocardiograms of all patients with repaired TOF who underwent CMR at our institution from 2011 to 2015 and also had an echocardiogram within 6 months of the CMR. The short-axis RV and LV EDAs were measured and the ratio of the two was calculated. Results were compared with CMR RV end-diastolic volume index (RVEDVi) and RV:LV end-diastolic volume ratio. The sensitivity and specificity values predicting RV volumes > 150 ml/m² were calculated. Fifty-eight studies met inclusion criteria. There were 47 studies with RVEDVi < 150 ml/m² and 11 with RVEDVi > 150 ml/m². RV:LV EDA and CMR RV:LV end-diastolic volume ratio correlated strongly (r = 0.76, p < 0.0001). An RV:LV EDA ≥ 1.57 had a 90% sensitivity to predict RVEDVi > 150 ml/m² (area under the curve = 0.74, 95% CI 1.5–27.9; p = 0.012). An RV:LV EDA ≥ 1.88 had an 81% specificity to detect RV volume index > 150 ml/m². Short-axis RV:LV EDA correlates well with an increased RVEDVi as measured by CMR. This new and simple measure can be used to predict optimal timing for CMR in anticipation of pulmonary valve replacement in repaired TOF.