Computational Pre-surgical Planning of Arterial Patch Reconstruction: Parametric Limits and In Vitro Validation

Abstract

Surgical treatment of congenital heart disease (CHD) involves complex vascular reconstructions utilizing artificial and native surgical materials. A successful surgical reconstruction achieves an optimal hemodynamic profile through the graft in spite of the complex post-operative vessel growth pattern and the altered pressure loading. This paper proposes a new in silico patient-specific pre-surgical planning framework for patch reconstruction and investigates its computational feasibility. The proposed protocol is applied to the patch repair of main pulmonary artery (MPA) stenosis in the Tetralogy of Fallot CHD template. The effects of stenosis grade, the three-dimensional (3D) shape of the surgical incision and material properties of the artificial patch are investigated. The release of residual stresses due to the surgical incision and the extra opening of the incision gap for patch implantation are simulated through a quasi-static finite-element vascular model with shell elements. Implantation of different unloaded patch shapes is simulated. The patched PA configuration is pressurized to the physiological post-operative blood pressure levels of 25 and 45 mmHg and the consequent post-operative stress distributions and patched artery shapes are computed. Stress–strain data obtained in-house, through the biaxial tensile tests for the mechanical properties of common surgical patch materials, Dacron, Polytetrafluoroethylene, human pericardium and porcine xenopericardium, are employed to represent the mechanical behavior of the patch material. Finite-element model is experimentally validated through the actual patch surgery reconstructions performed on the 3D printed anatomical stenosis replicas. The post-operative recovery of the initially narrowed lumen area and post-op tortuosity are quantified for all modeled cases. A computational fluid dynamics solver is used to evaluate post-operative pressure drop through the patch-reconstructed outflow tract. According to our findings, the shorter incisions made at the throat result in relatively low local peak stress values compared to other patch design alternatives. Longer cut and double patch cases are the most effective in repairing the initial stenosis level. After the patch insertion, the pressure drop in the artery due to blood flow decreases from 9.8 to 1.35 mmHg in the conventional surgical configuration. These results are in line with the clinical experience where a pressure gradient at or above 50 mmHg through the MPA can be an indication to intervene. The main strength of the proposed pre-surgical planning framework is its capability to predict the intra-operative and post-operative 3D vascular shape changes due to intramural pressure, cut length and configuration, for both artificial and native patch materials.Electronic supplementary materialThe online version of this article (10.1007/s10439-018-2043-5) contains supplementary material, which is available to authorized users.

Generation of a Purified iPSC-Derived Smooth Muscle-like Population for Cell Sheet Engineering

“…Mouse iPSC-derived Acta2 hrGFP+ cell sheets had significantly higher elastic modulus compared with the MOVAS control cell sheets but were not significantly different from that of Acta2 hrGFP− cell sheets. The moduli of the samples were in the 50- to 250-kPa range, which is in the range of elastic moduli of bovine vascular SMC sheets previously reported by our group (Backman et al., 2017a, Rim et al., 2018); however, this range of moduli is on the lower end of reported stiffnesses for blood vessels and engineered vascular grafts (0.1–50 MPa) (Guo and Kassab, 2003, Lashkarinia et al., 2018, Wagenseil and Mecham, 2009). The Acta2 hrGFP+ cell sheets did, however, have significantly higher max stress at failure when compared with Acta2 hrGFP− cell sheets and MOVAS cell sheets.…”

“…The elastic moduli of the iPSC-derived cell sheets in this study were lower than in our previously reported work (Backman et al., 2017a, Rim et al., 2018), which may be due to the lack of treatment with ascorbic acid, an additive used in previous studies. The moduli of the iPSC-derived cell sheets was also lower than the modulus of blood vessels (Guo and Kassab, 2003, Lashkarinia et al., 2018, Wagenseil and Mecham, 2009); however, blood vessels have a complex architectural structure composed of multiple aligned SMC layers oriented in different directions, while only single-layer cell sheets were tested in this study. Previous work from our group (Rim et al., 2018) explored mechanical properties of multi-layered bovine vascular SMC sheets; future work will need to focus on characterizing mechanical properties of stacked iPSC-derived cell sheets.…”

Computational Analysis of the Pulmonary Arteries in Congenital Heart Disease: A Review of the Methods and Results

“…Most of these papers—nine, respectively—were published in cardiovascular surgical journals [ 13 , 21 , 22 , 25 , 27 – 30 , 43 ]. The other 21 studies were published in technical journals, for example, focusing on biomedical engineering or numerical methods in medicine [ 12 , 14 , 15 , 17 , 19 , 23 , 26 , 31 – 42 , 44 ].…”

“…Shunt anatomy was mostly represented by one aortic or shunt inlet and two or three outlets representing the RPA, LPA, and/or the descending aorta [ 14 – 16 , 23 , 25 – 27 , 31 , 42 , 44 ]. In three studies, the flow in the main PA was computed using a model with one inlet and one outlet [ 13 , 19 , 20 ]. Kong et al analyzed a model with one inlet and 274 outlets, making it the biggest PA anatomy studied [ 36 ].…”

Role of flow preference in decision making for Blalock-Taussig shunt

“…I believe that the use of new tools to mimic and analyze hemodynamic problems can be useful to decrease morbidity and mortality, especially in challenging cases. Recently, CFD has become a popular tool for elucidating physiopathology to prevent certain possible complications of congenital heart surgery ( 5 ). I suggest that surgeons should make an effort to optimize the results with the routine use of CFD in clinical practice.…”