A novel transaortic microaxial ventricular assist device
B B Bulut, R B Buran, M Yigit, K A K KadipasaogluAbstract
Introduction
Despite proven benefits, micro-axial ventricular assist devices (µVADs) remain clinically limited by hemocompatibility-related complications (1) and anatomical access limitations, (2) motivating the ongoing search for alternative turbine geometries.
Purpose
We tested the in-silico performance of a novel half-blade geometry on a µVAD.
Methods
An innovative half-blade concept was used in µVAD design using 3-D CAD. Steady-state and transient simulations were run to evaluate flow characteristics and hemodynamics, with blood modeled as a Newtonian fluid (Density, 1,050 kg·m⁻³; Viscosity, 3.5 mPa·s). Rotor motion was represented using a rotating reference frame, upon which speed and inlet flow conditions were imposed. Pressure rise (ΔP) at diffuser outlet and net torque (T) were quantified to calculate hydraulic efficiency (η). In transient simulations, 4.76 × 10⁻⁶ sec/timestep, 1800 steps/1° rotation and 20 iterations/timestep were used. The Hemolysis Index (HI) was quantified using the Eulerian approach with the power law coefficients provided by Wu et al. (3)
Results
The 20 mm-long rotor with a diameter increasing from 1.6 at inlet to 4 mm at outlet was mounted on a 17×3 mm (length×dia) shaft (Fig. 1). Together with the diffuser (12 ×4 mm), overall turbine dimensions reached 37×7 mm (21 FR). At nominal operation (5 L/min@31 krpm), ΔP, T, η were 96.46 mmHg, 1.58 mN.m and 20.88%, respectively. Stagnation was not seen within the flow domain; flow was laminar without separation over the blades (Fig. 2, top) and more streamlined at diffuser outlet than published results. (4) Average wall shear stress was 659 Pa at the shroud (Fig. 2, bottom). Resulting HI was calculated as 0.037%.
Conclusions
Novel half-blade design demonstrated acceptable hydraulics and open flow architecture with minimal hemolysis. We concluded that bench-top tests are warranted to develop the concept into a competitive technology for use in cardiogenic shock or high-risk PCI settings.Computer-aided design of μVADFor image description, please refer to the figure legend and surrounding text.CFD visualization of μVADFor image description, please refer to the figure legend and surrounding text.