Computational Fluid Dynamics-Based Design Optimization for an Implantable Miniature Maglev Pediatric Ventricular Assist Device

Abstract

Computational fluid dynamics (CFD)-based design optimization was applied to achieve the finalized design of the PediaFlow® PF4, a magnetically levitated rotodynamic pediatric ventricular assist device. It features a streamlined blood-flow path with a single annular fluid passage between the rotor and the stationary housing. The resulting impeller is composed of a first-stage mixed-flow section having four blades at the conical nose region followed by a second-stage fully axial-flow section with three blades within the annular gap region. A stator with three inwardly-directed vanes is provided at the conical tail region to recover pressure and straighten the flow. CFD predictions of head and efficiency characteristics agreed remarkably well with the validation experimental data: with overprediction of head by <7 mmHg over the entire operational range and a slight overprediction in best efficiency by ∼1%. The new optimized PF4 extended the maximum flow range of the previous PF3 device by more than 100% to over 2.3 liter per minute (LPM) for the same range of operating speeds, and doubled the maximum hydraulic efficiency to ∼27%. Evaluation of hemolysis was performed by a Lagrangian particle-tracking technique with analysis of regional contributions to the overall blood damage. The simulation revealed that hemolysis increases with an increase in both the flow rate and rotor speed but not necessarily with just an increase in flow rate at a constant rotor speed. At the flow rate of 1.0 LPM and a head of 138 mmHg, PF4 has a hemolysis index of 0.0032 compared to 0.0058 produced by PF3 at the same flow rate with a head of 48 mmHg. Numerical simulation of radial fluid forces performed by the CFD model with an eccentric rotor revealed the presence of negative fluid stiffness that was monotonically related to both flow and speed. Finally, conjugate heat transfer analysis predicted temperature rise adjacent to the motor to be inversely proportional to the length, but not exceeding ∼2 °C over the intended range of operation. In conclusion, CFD-based design optimization greatly expedited and facilitated the completion of the PediaFlow® flow path and contributed to the system-wide optimization to produce a miniature maglev pump with exceptional hemocompatibility.

High fidelity computational simulation of thrombus formation in Thoratec HeartMate II continuous flow ventricular assist device

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Preclinical performance of a pediatric mechanical circulatory support device: The PediaFlow ventricular assist device

“…Intended to provide up to six months of circulatory support for patients between 3 to 15 kg at flow rates of 0.3–1.5 L/min, the 4 th generation PediaFlow® pediatric VAD (PF4) is the result of over 10 years of biomedical, mechanical, electrical, and computational engineering. Representing the latest pump topology designed to achieve the target flow rates, the PF4’s optimized blood-flow path consists of a tapered cylindrical impeller with four blades on the conical inlet face, leading to a single 1.5 mm annular fluid gap region, before passing through a three vane flow straightener machined into the aft-housing upon exit 24 . Integrated ‘quick-connect’ coupling mechanisms, recessed within the housing, enable direct attachment to the pump inlet and outlet (Figure 1-inset).…”

Systematic Design of a Magnetically Levitated Brushless DC Motor for a Reversible Rotary Intra‐Aortic Blood Pump

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