In-Vitro Flow Validation of Third-Generation Ventricular Assist Devices: Feasibility and Challenges.

Computational fluid dynamics (CFD) is a powerful tool for the in-silico evaluation of rotodynamic blood pumps (RBPs). Corresponding validation, however, is typically restricted to easily accessible, global flow quantities. This study showcased the HeartMate 3 (HM3) to identify feasibility and challenges of enhanced in-vitro validation in third-generation RBPs. To enable high-precision acquisition of impeller torques and grant access for optical flow measurements, the HM3 testbench geometry was geometrically modified. These modifications were reproduced in silico , and global flow computations validated along 15 operating conditions. The globally validated flow in the testbench geometry was compared with CFD-simulated flows in the original geometry to assess the impact of the necessary modifications on global and local hydraulic properties. Global hydraulic properties in the testbench geometry were successfully validated (pressure head: r = 0.999, root mean square error [RMSE] = 2.92 mmHg; torque: r = 0.996, RMSE = 0.134 mNm). In-silico comparison with the original geometry demonstrated good agreement ( r > 0.999, relative errors < 11.97%) of global hydraulic properties. Local hydraulic properties (errors up to 81.78%) and hemocopatibility predictions (deviations up to 21.03%), however, were substantially affected by the geometric modifications. Transferability of local flow measures derived on advanced in-vitro testbenches toward original pump designs is challenged by significant local effects associated with the necessary geometrical modifications.

A Cavopulmonary Assist Device for Long-Term Therapy of Fontan Patients.

Treatment of univentricular hearts remains restricted to palliative surgical corrections (Fontan pathway). The established Fontan circulation lacks a subpulmonary pressure source and is commonly accompanied by progressively declining hemodynamics. A novel cavopulmonary assist device (CPAD) may hold the potential for improved therapeutic management of Fontan patients by chronic restoration of biventricular equivalency. This study aimed at translating clinical objectives toward a functional CPAD with preclinical proof regarding hydraulic performance, hemocompatibility and electric power consumption. A prototype composed of hemocompatible titanium components, ceramic bearings, electric motors, and corresponding drive unit was manufactured for preclinical benchtop analysis: hydraulic performance in general and hemocompatibility characteristics in particular were analyzed in-silico (computational fluid dynamics) and validated in-vitro. The CPAD's power consumption was recorded across the entire operational range. The CPAD delivered pressure step-ups across a comprehensive operational range (0-10 L/min, 0-50 mm Hg) with electric power consumption below 1.5 W within the main operating range. In-vitro hemolysis experiments (N = 3) indicated a normalized index of hemolysis of 3.8 ± 1.6 mg/100 L during design point operation (2500 rpm, 4 L/min). Preclinical investigations revealed the CPAD's potential for low traumatic and thrombogenic support of a heterogeneous Fontan population (pediatric and adult) with potentially accompanying secondary disorders (e.g., elevated pulmonary vascular resistance or systemic ventricular insufficiency) at distinct physical activities. The low power consumption implied adequate settings for a small, fully implantable system with transcutaneous energy transfer. The successful preclinical proof provides the rationale for acute and chronic in-vivo trials aiming at the confirmation of laboratory findings and verification of hemodynamic benefit.

Validation of Numerically Predicted Shear Stress-dependent Dissipative Losses Within a Rotary Blood Pump.

Computational fluid dynamics find widespread application in the development of rotary blood pumps (RBPs). Yet, corresponding simulations rely on shear stress computations that are afflicted with limited resolution while lacking validation. This study aimed at the experimental validation of integral hydraulic properties to analyze global shear stress resolution across the operational range of a novel RBP. Pressure head and impeller torque were numerically predicted based on Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and validated on a testbench with integrated sensor modalities (flow, pressure, and torque). Validation was performed by linear regression and Bland-Altman analysis across nine operating conditions. In power loss analysis (PLA), in silico hydraulic power losses were derived based on the validated hydraulic quantities and balanced with in silico shear-dependent dissipative power losses. Discrepancies among both terms provided a measure of in silico shear stress resolution. In silico and in vitro data correlated with low discordance in pressure (r = 0.992, RMSE = 1.02 mmHg), torque (r = 0.999, RMSE = 0.034 mNm), and hydraulic power losses (r = 0.990, RMSE = 0.015W). PLA revealed numerically predicted dissipative losses to be up to 34.4% smaller than validated computations of hydraulic losses. This study confirmed the suitability of URANS settings to predict integral hydraulic properties. However, numerical credibility was hampered by lacking resolution of shear-dependent dissipative losses.