Mechanical cavopulmonary assistance of a patient-specific Fontan physiology: numerical simulations, lumped parameter modeling, and suction experiments.

This study investigated the performance of a magnetically levitated, intravascular axial flow blood pump for mechanical circulatory support of the thousands of Fontan patients in desperate need of a therapeutic alternative. Four models of the extracardiac, total cavopulmonary connection (TCPC) Fontan configuration were evaluated to formulate numerical predictions: an idealized TCPC, a patient-specific TCPC per magnetic resonance imaging data, and each of these two models having a blood pump in the inferior vena cava (IVC). A lumped parameter model of the Fontan physiology was used to specify boundary conditions. Pressure-flow characteristics, energy gain calculations, scalar stress levels, and blood damage estimations were executed for each model. Suction limitation experiments using the Sylgard elastomer tubing were also conducted. The pump produced pressures of 1-16 mm Hg for 2000-6000 rpm and flow rates of 0.5-4.5 L/min. The pump inlet or IVC pressure was found to decrease at higher rotational speeds. Maximum scalar stress estimations were 3 Pa for the nonpump models and 290 Pa for the pump-supported cases. The blood residence times for the pump-supported cases were shorter (0.9 s) as compared with the nonsupported configurations (2.5 s). However, the blood damage indices were higher (1.5%) for the anatomic model with pump support. The pump successfully augmented pressure in the TCPC junction and increased the hydraulic energy of the TCPC as a function of flow rate and rotational speed. The suction experiments revealed minimal deformation (<3%) at 9000 rpm. The findings of this study support the continued design and development of this blood pump.

Uniquely shaped cardiovascular stents enhance the pressure generation of intravascular blood pumps.

OBJECTIVE: Advances in the geometric design of blood-contacting components are critically important as the use of minimally invasive, intravascular blood pumps becomes more pervasive in the treatment of adult and pediatric patients with congestive heart failure. The present study reports on the evaluation of uniquely shaped filaments and diffuser blades in the development of a protective stent for an intravascular cavopulmonary assist device for patients with a single ventricle. METHODS: We performed numeric modeling, hydraulic testing of 11 stents with an axial flow blood pump, and blood bag experiments (n = 6) of the top-performing stent geometries to measure the levels of hemolysis. A direct comparison using statistical analyses, including regression analysis and analysis of variance, was completed. RESULTS: The stent geometry with straight filaments and diffuser blades that extended to the vessel wall outperformed all other stent configurations. The pump with this particular stent was able to generate pressures of 2 to 32 mm Hg for flow rates of 0.5 to 4 L/min at 5000 to 7000 RPM. A comparison of the experimental performance data to the numeric predictions demonstrated an excellent agreement within 16%. The addition of diffuser blades to the stent reduced the flow vorticity at the pump outlet. The average and maximum normalized index of hemolysis level was 0.0056 g/100 L and 0.0064 g/100 L, respectively. CONCLUSIONS: The specialized design of the stents, which protect the vessel wall from the rotating components of the pump, proved to be advantageous by further augmenting the pressure generation of the pump, reducing the flow vorticity at the pump outlet, and enhancing flow control.