Numerical modelling of redo of the prosthetic heart valve: hemodynamics

Aim. In this article, we report a numerical analysis of the causes and haemodynamic effects of paraprosthetic reauraitation durina redo transcatheter prosthesis of the aortic valve with the "valve-in-valve” technique with respect to the predictive value of computer modellina. Methods. 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-expandina aortic valve bioprosthesis. The three-dimensional computer models of the aortic root, the frame, and the transcatheter bioprosthesis were reconstructed usina the multislice computed tomoaraphic data of patient T. aged 61 years who underwent "valve-in-valve” implantation of a self-expandina valve (CoreValve™; Medtronic, Dublin, Ireland). Computer modellina was performed with the immersed boundary method, considerina the haemodynamic characteristics of the patient which were obtained by postoperative transthoracic echocardioaraphy. Qualitative and quantitative indicators of blood flow averaae 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 reaard to the area of observation of the first-dearee paraprosthetic reauraitation in the zone of mitral-aortic contact; such reauraitation was clinically observed at 6 months. Results. In numerical simulations, high blood flow velocities in the reaion of interest (the area of the paraprosthetic blood leakaae) as well as stresses (viscous and Reynolds stresses) do not aenerally 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. Conclusion. As a result of clinically observed first-dearee paraprosthetic reauraitation 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 arisina from transcatheter prosthetics satisfactorily reproduced the clinical picture of paraprosthetic reauraitation and can form the basis of numerical proanostic models of similar interventions.