Four-Dimensional Computed Tomography–Guided Valve Sizing for Transcatheter Pulmonary Valve Replacement

Background: Measurements of the right ventricle and pulmonary artery are highly variable for the optimal selection of prosthesis size of transcatheter pulmonary valve replacement, (TPVR). Traditional measurement methods by 2D/3D imaging for device size prediction are insufficient to assess the displacement of the right ventricular outflow tract and pulmonary artery which could increase the risks of stent misplacement, paravalvular leak, and device embolization. We aim to provide a dynamic model to visualize and quantify the anatomical structure of the RVOT to PA over the entire cardiac cycle with 4D cardiac CT reconstruction to achieve an accurate quantitate evaluation of needed valve size.

Method: In this pilot study, three-dimensional cardiac CT was obtained from preclinical trials in a sheep model and then imported into 3D slicer to build a 4D sequence which was divided into 11 frames throughout the cardiac cycle to show the deformation of the heart. Diameter, cross-sectional area, and circumference of five imaging planes at the main pulmonary artery, sinotubular junction, sinus, basal plane of the pulmonary valve (BPV), and RVOT were measured throughout every 10% of the cardiac cycle in 4D straightened models prior to valve implantation to predict the valve size. Meanwhile, the dynamic changes of the volume in the right ventricle were also performed to evaluate the right heart function. 2D measurements at the end of the diastolic phase (60% of the cardiac cycle) were achieved to compare with 4D measurement.

Results: In sheep J, 4D CT measurements from straightened model had the same selection of valve sizing as 2D measurements for TPVR (30 mm), with the advantages of remarkably virtual reality and reliable results. There were significant differences in the measured cross-area (RVOT: 3.42 cm² in 4D vs. 4.28 cm² in 2D, BPV: 2.96 cm² in 4D vs. 3.92 cm² in 2D) and circumferences (RVOT: 76.1 mm in 4D vs. 87.06 mm in 2D, BPV: 67.65 mm in 4D vs. 75.73 mm in 2D) in RVOT and the basal plane of the pulmonary valve. The right ventricular ejection fraction of sheep J from pre-CT was 62.1%.

Conclusion: In contrast with the 3D CT, the straightened 4D reconstruction model could not only enable accurate prediction for valve size selection of TPVR but also could provide ideally virtual reality which would be a promising method applied for TPVR.

Publication History

Article published online:
12 February 2022