Numerical modelling of redo of the prosthetic heart valve: hemodynamics

Abstract

<p><strong>Aim.</strong> In this article, we report a numerical analysis of the causes and haemodynamic effects of paraprosthetic regurgitation during redo transcatheter prosthesis of the aortic valve with the “valve-in-valve” technique with respect to the predictive value of computer modelling.<br /><strong>Methods.</strong> We used numerical analysis of haemodynamics for a patient-specific simulation of blood flow in the “valve-in-valve” complex formed from a failed framed and transcatheter self-expanding aortic valve bioprosthesis. The three-dimensional computer models of the aortic root, the frame, and the transcatheter bioprosthesis were reconstructed using the multislice computed tomographic data of patient T. aged 61 years who underwent “valve-in-valve” implantation of a self-expanding valve (CoreValve™; Medtronic, Dublin, Ireland). Computer modelling was performed with the immersed boundary method, considering the haemodynamic characteristics of the patient which were obtained by postoperative transthoracic echocardiography. Qualitative and quantitative indicators of blood flow average and peak blood flow velocities, wall shear, viscous stress, and Reynolds stress were analysed, as were the distributions of these indicators in the blood flow volume of the model. Particular attention was paid to these indicators with regard to the area of observation of the first-degree paraprosthetic regurgitation in the zone of mitral–aortic contact; such regurgitation was clinically observed at 6 months.<br /><strong>Results.</strong> In numerical simulations, high blood flow velocities in the region of interest (the area of the paraprosthetic blood leakage) as well as stresses (viscous and Reynolds stresses) do not generally cause substantial mechanical destruction of red blood cells because of the short exposure time. In the wall of the fistula, the high shear stress that results from the simulation of high blood flow velocities can initiate thrombosis with the participation of von Willebrand factor in the case of endothelial inflow of the primary bioprosthesis with dysfunction. However, these effects were not clinically observed.<br /><strong>Conclusion.</strong> As a result of clinically observed first-degree paraprosthetic regurgitation caused by the low position of the CoreValve™ transcatheter prosthesis in relation to the primary frame bioprosthesis, the contact area of the prosthesis-in-prosthesis was reduced. The patient-specific methods used to assess haemodynamic effects arising from transcatheter prosthetics satisfactorily reproduced the clinical picture of paraprosthetic regurgitation and can form the basis of numerical prognostic models of similar interventions.</p><p>Received 12 June 2019. Revised 31 October 2019. Accepted 6 November 2019.</p><p><strong>Funding:</strong> The research is supported by a grant of the Russian Science Foundation (project No. 18-75-10061).</p><p><strong>Conflict of interest:</strong> Authors declare no conflict of interest.</p>