No abstract

While Fontan palliation in the form of the total cavopulmonary connection has improved the management of congenital single ventricle physiology, long-term outcomes for patients with this disease are suboptimal due to the lack of two functional ventricles. Researchers have shown that ventricular assist devices (VADs) can normalize Fontan hemodynamics. To minimize blood contacting surfaces of the VAD, we evaluated the use of an external compression device (C-Pulse Heart Assist System, Sunshine Heart Inc.) as a Fontan assist device. A mock circulation was developed to mimic the hemodynamics of a hypertensive Fontan circulation in a pediatric patient. The Sunshine C-Pulse compression cuff was coupled with polymeric valves and a compressible tube to provide nonblood-contacting pulsatile flow through the Fontan circulation. The effect of the number, one or two, and placement of valves, before or after the compression cuff, on inferior vena cava pressure (IVCP) was studied. In addition, the effect of device inflation volume and compression rate on maintaining low IVCP was investigated. With one valve located before the cuff, the device was unable to maintain an IVCP below 15.5 mm Hg. With two valves, the C-Pulse was able to maintain IVCP as low as 8.5 mm Hg. The C-Pulse provided pulsatile flow and pressure through the pulmonary branch of the mock circulation with a pulse pressure of 16 mm Hg and 180 mL/min additional flow above unassisted flow. C-Pulse compression reduced IVCP below 12 mm Hg with 13 cc inflation volume and compression rates above 105 bpm. This application of an external compression device combined with two valves has potential for use as an artificial right ventricle by maintaining low IVCP and providing pulsatile flow through the lungs.

The large operating range of FREE-D system extends the use of VAD for nearly all patients without being affected by the depth of the implanted pump. Our in-vivo results with the FREE-D system may offer a new perspective on quality of life for patients supported by implanted device.

Frequency-leveraged electrohydraulic and piezohydraulic pumps represent an alternative technology to traditional electromagnetic motors. The development of a 45 cm 3 piezohydraulic pump utilizing a 2 g low-voltage piezoelectric stack is presented. The piezohydraulic pump flow rate and performance were measured and compared to existing pumps in the literature. The flow rate produced by piezohydraulic pump was a non-linear function of pump operational frequency showing multiple peaks. These flow rate peaks were a function of accumulator size and hydraulic line resonance. The piezohydraulic pump was capable of producing a 125 kPa stall pressure, 186 mL/min no-load flow rate, and 0.14 W of power. This pump constitutes one of the two miniature piezohydraulic pumps capable of outputting useful mechanical work. In addition, these results demonstrate that the external hydraulic lines and hydraulic accumulators have a significant effect on the flow and power output of this technology.

Piezohydraulic pumps are high power density motors, which can be theoretically miniaturized with minimal loss in power output. The feasibility of using piezohydraulic pumps in pulsatile pediatric ventricular assist devices is presented in this study. A theoretical analysis is presented to calculate the piezohydraulic pump dimensions needed to meet flow and pressure requirements. In addition, an existing piezohydraulic pump was incorporated into a ventricular assist device driver to drive a pulsatile pediatric 30-mL stroke ventricular assist device as a proof of concept. The driver was tested at heart rates ranging from 50 to 110 beats per minute in an in vitro mock circulation to characterize its performance. The maximum drive pressure was 33 kPa with a peak flow rate of 6 L/min against a 10-kPa back pressure. The maximum mean flow rate from the ventricular assist device outlet was 3 L/min at 100 beats per minute operation. These results compare well to commercially available systems that output between 25 and 40 kPa drive pressure and flows between 0 and 10 L/min against 10–16 kPa pressures.