Hemodynamic-based virtual surgery design of double-patch repair for pulmonary arterioplasty in tetralogy of Fallot

Background and objective: Surgical correction of pulmonary artery stenosis (PAS) is essential to the prognosis of patients with tetralogy of Fallot (TOF). The double -patch method of pulmonary arterioplasty is usually applied in case of multiple stenosis in TOF patients' pulmonary artery (PA) and when PAS cannot be relieved by the singlepatch method. The surgical planning for the double -patch design remains challenging. The purpose of this study is to investigate the double -patch design with different angulations between the left pulmonary artery (LPA) and the right pulmonary artery (RPA), and to understand postoperative hemodynamic alterations by the application of computer -aided design (CAD) and computational fluid dynamics (CFD) techniques. Methods: The three-dimensional model of the PA was reconstructed based on preoperative computed tomography imaging data obtained from the patient with TOF. Three postoperative models with different designs of doublepatch were created by "virtual surgery" using the CAD technique. Double -Patch 120 Model was created with double patches implanted in the main pulmonary artery (MPA) and the PA bifurcation and without changing the spatial position of PA. The angulation between the LPA and the RPA was defined as theta, which equaled to 120 degrees in Pre -Operative Model and Double -Patch 120 Model. Based on Double -Patch 120 Model, Double -Patch 110 Model and Double -Patch 130 Model were generated with theta equaled to 110 degrees and 130 degrees, respectively. Combined with CFD, the differences of velocity streamlines, wall shear stress (WSS), flow distribution ratio (FDR), and energy loss (EL) were compared to analyze postoperative pulmonary flow characteristics. Results: The values of velocity and WSS decreased significantly after virtual surgery. Obvious vortices and swirling flows were observed downstream of the stenosis of RPA and LPA in Pre -Operative Model, while fewer vortices developed along the anterior wall of the expanded lumens of RPA, especially in Double -Patch 110 Model. With the relief of PAS, two relatively higher WSS regions were observed at the posterior walls of RPA and LPA. The maximum WSS values in these regions of Double -Patch 110 Model were lower than those in DoublePatch 120 Model and Double -Patch 130 Model. Furthermore, the FDRs were elevated and the ELs were greatly reduced. It was found that Double -Patch 110 Model with the angulation between the LPA and the RPA equaled to 110 degrees showed relatively better properties of hemodynamics than other models. Conclusions: The angulation between the LPA and the RPA is an important factor that should be integrated in the double -patch design for TOF repair. Virtual surgery based on patient -specific vascular model and computational hemodynamics can be used to provide assistance for individualized surgical planning of double -patch arterioplasty.