Magnetic resonance imaging (MRI) is essential to assess right ventricular enlargement and function as well as the severity of pulmonary regurgitation before pulmonary valve replacement. Transcatheter pulmonary valve replacement (TPVR) has emerged as an alternative to surgical replacement but limited by the size of the right ventricular outflow tract (RVOT).

The aim of the study was to compare the measurements of native RVOT between different MRI imaging sequences and catheterization findings.

Single-center retrospective study of patients who underwent TPVI for severe pulmonary regurgitation assessed by 4D flow MRI, without significant residual RVOT obstruction. Balloon calibration was used as the reference.

Nine adult with repaired tetralogy of Fallot and one patient with Ross procedure were included (mean age: 43.9±12.9). One patient had a too large RVOT to achieve a TPVR, 1 patient had TPVR with Edwards XT 29mm valve, 7 patients had Melody valve implantation procedure. Mean RVOT measured 25.1±3.0mm by balloon calibration, 25.0±3.2mm and 22.5±3.0mm 4D flow MRI, in respectively in systole and diastole, 22.7±2.4mm in 2D SSFP MRI. Interventional angiograms dimensions were 26.7±3.3mm and 24.4±1.3mm respectively in systole and diastole. No statistical differences were found comparing different measurements dimensions. Good correlation was found between balloon calibration and MRI 4D flow in systole (r=0.794, P=0.01), while no correlation existed between balloon calibration, 2D MRI and 4D flow MRI in diastole. Balloon calibration was also well correlated to angiograms measurements (r=0.881; P=0.0002 and r=0.775; P=0.024, respectively).

4D flow MRI sequence allowing 3D measurement through the cardiac cycle, appears as an interesting technique to measure RVOT in daily practice and therefore to plan TPVI.