Right Ventricular Outflow Tract and Pulmonary Artery Strains During the Cardiac Cycle Prior to Pulmonary Valve Replacement

Right ventricular outflow tract and pulmonary arteries (RVOT/PAs) in surgically repaired congenital heart disease are highly dynamic structures, dilating in systole to accommodate the ejected blood volume while also elongating due to the ventricular contraction. In this study, we aim to quantify RVOT/PA circumferential and axial strains in a population of patients assessed for transcatheter pulmonary valve replacement (TPVR). 3D RVOT/PA geometries at end diastole and systole were reconstructed from 4D computed tomography images of 20 patients (35% female; 34 ± 15 years; 50% pulmonary stenosis, 40% Tetralogy of Fallot). A deformable shape model (DSM) was built to establish point-correspondence between subjects at end diastole and measure the RVOT/PA deformations of each subject to systole. The strain components were averaged over RVOT, pulmonary valve, and pulmonary trunk, and the strain ratio, describing the simultaneous deformations in the two main loading directions, was calculated. Overall, circumferential strains were smaller (range: - 0.28-0.30; area-weighted average 0.09), than axial strains (range: - 0.16-0.95; area-weighted average 0.28). Axial strains were high in the RVOT and progressively decreased toward the PA bifurcation, while circumferential strains increased instead. 90% of RVOT/PA showed positive strain ratios (0.13 ± 0.31, 0.25 ± 0.20, and 1.04 ± 0.52 in the RVOT, pulmonary valve, and pulmonary trunk, respectively). The RVOT/PA DSM computed in TPVR patients confirmed the macroscopic positive strain ratio observed during the cardiac cycle, with overall greater axial strains compared to circumferential strains. This may have implications in device/patient selection for TPVR.