Purpose of Study: Availability of mechanical circulatory support of both sides of the heart for pediatric patients has been limited due to size constraints. By combining 2 scaled down ventricular assist devices (VADs), one centrifugal and one axial, into a single compact BiVAD unit, it is possible that a full heart replacement will be able to fit into pediatric patients.

Methods Used: A scaled-up model of the final design has been constructed with some modifications to test the centrifugal pump and compatibility of the combination. A previously developed VAD was used as an inner axial pump. The outer pump consisted of a centrifugal pump using a slice motor design. A copper wound cast iron armature surrounded the housing, and drove permanent magnets in the pump rotor base. The pump housing and rotor were made using SLA 3D printing. The coils were driven by an RC speed controller and battery. The centrifugal pump’s performance was tested using a closed loop of water. A clamp provided resistance, differential pressure was measured by a pressure sensor, and flow rate was measured using a clamp-on ultrasonic flow meter.

Results: Tests show the centrifugal pump, which will support the left ventricle, generates 63-67 mmHg pressure increase at 0.5-5 L/min of flow at 1500 rpm. The axial pump, which will support the right ventricle generates 10-25 mmHg at 0.5-5 L/min of flow. Figure 1 shows the BiVAD configuration.

Summary: The testing of a scaled up centrifugal pump showed promising results. In addition, the incorporation of the axial pump has allowed preliminary testing of the BiVAD system. Future work will focus on the miniaturization and levitation of the device.