Fluid dynamics of a pediatric ventricular assist device

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Pediatric Medical Devices

Background:

• Mechanical circulatory support is increasingly vital for pediatric patients undergoing cardiac procedures and transplantation.
• Current salvage rates for pediatric patients requiring circulatory support remain low, highlighting a critical unmet need.
• Existing adult-sized pneumatic ventricular assist devices demonstrate high success rates, but pediatric versions face significant challenges.

Purpose of the Study:

• To investigate the fluid dynamic factors contributing to thrombus formation in a scaled-down (15 cc) pediatric ventricular assist device.
• To understand why a smaller version of a successful adult device failed in animal experiments.
• To identify design modifications for improved pediatric mechanical circulatory support.

Main Methods:

• Dimensional analysis to compare key dimensionless parameters (Reynolds and Strouhal numbers) between successful and unsuccessful pumps.
• Two-component laser Doppler velocimetry to quantitatively characterize internal flow fields.
• Comparative analysis of flow field data with established data from a successful 70 cc device.

Main Results:

• Significant differences in Reynolds (Re) and Strouhal (St) numbers were identified between the 70 cc and 15 cc pumps.
• The 15 cc pump exhibited reduced wall shear stress and lower turbulence levels compared to the 70 cc pump.
• These altered fluid dynamic conditions in the smaller pump create an environment conducive to thrombus deposition.

Conclusions:

• The failure of the 15 cc pediatric ventricular assist device is attributed to altered fluid dynamics resulting from size reduction, not material or operational principles.
• Reduced pump size leads to suboptimal flow conditions that promote clot formation, compromising device efficacy.
• Further research into pediatric ventricular assist device design must prioritize fluid dynamics to mitigate thrombus risk and improve patient outcomes.