Análise do escoamento pulsátil em fístula arteriovenosa rígida e flexível: estudo in vitro

Abstract

Arteriovenous fistula (AVF) is the most suitable vascular access for performing hemodialysis treatment. Problems related to its manufacture, new flow conditions and vascular remodeling cause early failures in about 60% of this type of access. The current study seeks to experimentally analyze an AVF model of a specific patient with rigid and flexible walls submitted to pulsatile flow, investigating the flow conditions at points other than the access and the deformation suffered according to the imposed load. Using a computed tomography scan (HUOL - UFRN), the virtual model of the brachiocephalic AVF was extracted from a patient undergoing hemodialysis where, using the Meshmixer and Fusion 360 software (Autodesk. São Rafael, California, USA), processes of geometry correction, superficial improvement and allocation of points for the pressure intakes and fixation in the pumping system are developed. The manufacture of the rigid FAV was done directly through 3D printing and the flexible FAV was manufactured through injection molding, also manufactured through 3D printing, and this stage of the process was performed at VOID3D (Metrópole Digital - IMD - UFRN ). During the experimental tests, pressure pulses were collected at 7 different points (entrance and exit of the AVF, two points in the arterial region, two points in the venous region and one point in the anastomosis region), the flow pulse at the exit of the system and deformation in the flexible AVF model. From the results obtained, the influence of the deformation of the access walls on the damping of the pulses was observed, showing pulses with lower peaks in the flexible AVF model, with an average decrease of 21.7% in the pressure peaks and 15, 1% at peak flow pulse in flexible AVF compared to rigid. The deformation results showed regions susceptible to greater mechanical stresses, such as pseudoaneurysms and regions of marked curvature of the access, these regions being of greater care and monitoring, which may be susceptible to pathophysiological problems. It was evidenced that AVF models with greater flexibility have more damped flow, with fewer peaks and with relatively small losses when compared to the rigid ones.