Currently available mechanical circulatory support systems are limited for adolescent and adult patients with a Fontan physiology. To address this growing need, we are developing a collapsible, percutaneously-inserted, axial flow blood pump to support the cavopulmonary circulation in Fontan patients. During the first phase of development, the design and experimental evaluation of an axial flow blood pump was performed. We completed numerical modeling of the pump using computational fluid dynamics analysis, hydraulic testing of a plastic pump prototype, and blood bag experiments (n=7) to measure the levels of hemolysis produced by the pump. Statistical analyses using regression were performed. The prototype with a 4-bladed impeller generated a pressure rise of 2-30 mmHg with a flow rate of 0.5-4 L/min for 3000-6000 RPM. A comparison of the experimental performance data to the numerical predictions demonstrated an excellent agreement with a maximum deviation being less than 6%. A linear increase in the plasma-free hemoglobin (pfHb) levels during the 6-h experiments was found, as desired. The maximum pfHb level was measured to be 21 mg/dL, and the average normalized index of hemolysis was determined to be 0.0097 g/100 L for all experiments. The hydraulic performance of the prototype and level of hemolysis are indicative of significant progress in the design of this blood pump. These results support the continued development of this intravascular pump as a bridge-to-transplant, bridge-to-recovery, bridge-to-hemodynamic stability, or bridge-to-surgical reconstruction for Fontan patients.

To provide a viable bridge-to-transplant, bridgeto-recovery, or bridge-to-surgical reconstruction for patients with failing Fontan physiology, we are developing a collapsible, percutaneously inserted, magnetically levitated axial flow blood pump to support the cavopulmonary circulation in adolescent and adult patients. This unique blood pump will augment pressure and thus flow in the inferior vena cava through the lungs and ameliorate the poor hemodynamics associated with the univentricular circulation. Computational fluid dynamics analyses were performed to create the design of the impeller, the protective cage of filaments, and the set of diffuser blades for our axial flow blood pump. These analyses included the generation of pressure-flow characteristics, scalar stress estimations, and blood damage indexes. A quasi-steady analysis of the diffuser rotation was also completed and indicated an optimal diffuser rotational orientation of approximately 12°. The numerical predictions of the pump performance demonstrated a pressure generation of 2-25 mm Hg for 1-7 L/min over 3000-8000 rpm. Scalar stress values were less than 200 Pa, and fluid residence times were found to be within acceptable ranges being less than 0.25 s. The maximum blood damage index was calculated to be 0.068%. These results support the continued design and development of this cavopulmonary assist device, building upon previous numerical work and experimental prototype testing. Key Words: Ventricular assist device(s)-Single ventricle physiology-Cavopulmonary assist device-Fontan conversion-Heart pump-Blood pump-Artificial right ventricle-Pediatric circulatory support-Intravascular blood pump-Mechanical cavopulmonary assist.Pediatric cardiovascular malformations contribute to 6-10% of all infant deaths and are one of the two leading causes of neonatal death. These malformations occur in approximately one to eight of every 1000 live births with a significant incidence of one in six infants being born preterm (1,2). The occurrence of multiple and significant cardiac malformations, such as tricuspid atresia and hypoplastic left heart syndrome, requires corrective surgery (3,4). The only chance of survival for these patients is the threestaged surgical palliative procedure known as the Fontan procedure, which results in the patients having a single functional ventricle to drive blood flow through the systemic and pulmonary circulations.Care must be taken in operating on these infants at such a short time after birth since the pulmonary vascular beds are reactive from prenatal stages of development and may induce elevated vascular resistance by contractions of smooth muscle lining. The first operation, known as the Norwood procedure, provides blood flow to the lungs through an artery-topulmonary-artery shunt. This operation occurs within 2 weeks of age. After the risk of elevated pulmonary vascular resistance has decreased, the conversion is continued with the second stage known as the Glenn, in which the Norwood shunt is disconnected and the superior v...

To provide hemodynamic support to patients with a failing single ventricle, we are developing a percutaneously inserted, magnetically levitated axial flow blood pump designed to augment pressure in the cavopulmonary circulation. The device is designed to serve as a bridge-to-transplant, bridge-to-recovery, bridge-to-hemodynamic stability, or bridge-to-surgical reconstruction. This study evaluated the hydraulic performance of three blood pump prototypes (a four-bladed impeller, a three-bladed impeller, and a three-bladed impeller with a four-bladed diffuser) whose designs evolved from previous design optimization phases. Each prototype included the same geometric protective cage of filaments, which stabilize the rotor within the housing and protect the housing wall from the rotating blades. All prototypes delivered pressure rises over a range of flow rates and rotational speeds that would be sufficient to augment hemodynamic conditions in the cavopulmonary circulation. The four-bladed impeller outperformed the two remaining prototypes by >40%; this design was able to generate a pressure rise of 4-28 mm Hg for flow rates of 0.5-10 L/min at rotational speeds of 4,000-7,000 RPM. Successful development of this blood pump will provide clinicians with a feasible therapeutic option for mechanically supporting the failing Fontan.

We are developing a collapsible, percutaneously inserted, axial flow blood pump to support the cavopulmonary circulation in infants with a failing single ventricle physiology. An initial design of the impeller for this axial flow blood pump was performed using computational fluid dynamics analysis, including pressure-flow characteristics, scalar stress estimations, blood damage indices, and fluid force predictions. A plastic prototype was constructed for hydraulic performance testing, and these experimental results were compared with the numerical predictions. The numerical predictions and experimental findings of the pump performance demonstrated a pressure generation of 2-16 mm Hg for 50-750 ml/min over 5,500-7,500 RPM with deviation found at lower rotational speeds. The axial fluid forces remained below 0.1 N, and the radial fluid forces were determined to be virtually zero due to the centered impeller case. The scalar stress levels remained below 250 Pa for all operating conditions. Blood damage analysis yielded a mean residence time of the released particles, which was found to be less than 0.4 seconds for both flow rates that were examined, and a maximum residence time was determined to be less than 0.8 seconds. We are in the process of designing a cage with hydrodynamically shaped filament blades to act as a diffuser and optimizing the impeller blade shape to reduce the flow vorticity at the pump outlet. This blood pump will improve the clinical treatment of patients with failing Fontan physiology and provide a unique catheter-based therapeutic approach as a bridge to recovery or transplantation.

An intravascular axial flow blood pump has suitable hydraulic characteristics for use to augment pressure in the cavopulmonary circulation in Fontan patients. This study presents the experimental hydraulic performance testing of six flexible-bladed and one rigid-bladed pump prototypes for mechanical cavopulmonary assist. Unique in design, six of these prototypes were manufactured using varying grades of polyurethane material to reduce blade hardness. The hydraulic performance of these prototypes were measured and quantitatively compared to a rigid-bladed prototype through a regression analysis. To shield the vessel wall from the rotating impeller blades, two novel protective cage designs were also evaluated for additional energy augmentation. The pumps with no protective cage produced pressure rises of 1-12 mmHg for flow rates of 0.5-4 L/min at rotational speeds of 4000-7000 rpm. The flexible-bladed prototypes generated pressure rises within 12% of the rigidbladed pump design. The most flexible prototype (F-15) was able to generate pressure rises within 4.1% of the rigidbladed impeller. The partially twisted and fully twisted protective cage designs also functioned as desired by augmenting energy transfer in range of 5-15 mmHg, respectively. This study dispels the assumption that rigid-impeller blades are absolutely necessary to maintain the pressure generation of rotary blood pumps and demonstrates the potential of uniquely shaped cage filaments to augment the energy transfer of an axial flow blood pump for mechanical cavopulmonary assistance. The successful development of this blood pump will provide clinicians with a therapeutic option for mechanically supporting the failing Fontan physiology in adolescent and adult patients.