In vivo evaluation of the NEDO biventricular assist device with an RPM dynamic impeller suspension system

Ten-year NEDO BVAD development program: moving forward to the clinical arena

Since 1995, the Baylor Group has been developing a totally implantable NEDO BVAD system. This 10-year program was completed in March 2005, and preparation for clinical trials is underway. This article summarizes the entire 10-year NEDO program and describes the strategy for clinical trials. The project aimed to achieve: (1) dual centrifugal pumps with the ability of full biventricular support, (2) a compact system implantable into small adults, (3) a totally implantable system with transcutaneous energy transmission system (TETS), (4) a durable system with a lifetime of over 5 years, and (5) a system free of thrombus and with minimal hemolysis. The final goals are to complete preclinical system evaluations and commence the clinical trials in the near future. In vitro studies have demonstrated a pump capacity of over 8.5 l/min and an Index of Hemolysis of <0.004 g/100 l. The pump-bearing life expectancy was over 5 years. To date, eight pumps endured in vivo studies of over 3 months without complications, including thromboembolic events. The in vitro endurance studies of eight pumps are longer than 1 year. There were no mechanical malfunctions or pump failure. A stepwise clinical trial is being planned: Step1, a wearable BVAD/VAD will be clinically studied; Step 2, the BVAD/VAD will be implanted intracorporeally without TETS; and, Step 3, a totally implantable system will be clinically evaluated. The NEDO BVAD system has completed preclinical testing. Clinical trial preparation is underway.

Multiscale analysis of surface thrombosis in vivo in a left ventricular assist system

Thrombosis limits the success of ventricular assist devices as the demand for alternatives to heart transplants is increasing. This study mapped the occurrence of thrombosis in a left ventricular assist system (LVAS) to better understand the biologic response to these devices. Nine calves divided into two groups were implanted with LVAS for 28 to 30 days. One group was anticoagulated, whereas the second group received no long-term anticoagulation. The blood-contacting poly(urethane urea) surfaces of blood sacs in the LVAS were examined for macroscopic thrombi upon retrieval. The sac was partitioned into eight sections and imaged for thrombi by scanning electron microscopy. No difference in thrombosis was observed macroscopically between the groups. Anticoagulation appeared to result in reduction of platelet-like structures, but the presence of fibrin-like structures remained similar between groups. Regional differences correlating with high and low shear stress regions were observed. At the macroscale, fewer thrombi were recorded in the high shear stress ports. At the microscale, features resembling fibrin were observed primarily in the ports and platelet-like features were common in lower shear stress regions. These variations in thrombosis with anticoagulation and location are likely due to varied fluid dynamics within the LVAS blood sac.

Real-time studies of the pivot bearings in the NEDO Gyro PI-710 centrifugal blood pump

The NEDO Gyro PI-710 centrifugal pump (Gyro PI-710 pump) incorporates a double pivot bearing system of which the male pivot and female bearings are fabricated from Al2O3 ceramic and ultrahigh molecular weight polyethylene. The top female bearing is a critical component because the impeller is levitated by hydraulic force and is maintained in the top contact position. A long-term in vitro examination of the pivot bearings was conducted using a biventricular assist model. In 7 animal experiments, the depth change of the top female bearing was examined. Animal experiments up to 90 days revealed that there was no noticeable depth increase in the top female bearing. According to the in vitro study, the life of the pivot bearings of the left and right pump was estimated to be approximately 3 and 7 years, respectively. Further improvement of this pivot bearing system is currently underway.

Development of a flexible inflow cannula with titanium inflow tip for the NEDO biventricular assist device

A newly designed flexible inflow cannula has been developed for a biventricular assist device (BVAD). The inflow tip was designed for long-term ventricle drainage. Considering the anatomic differences between the right and left ventricles, a flexible inflow cannula, as a mass production model with a titanium tip, was developed and investigated in chronic BVAD animal experiments using the NEDO permanently implantable centrifugal blood pump. These flexible inflow cannulae consist of flexible plastic tubing with wire supported, titanium left and right tips. The right titanium inflow tip was designed with inner and outer stoppers to be inserted into the right ventricle wall and a beak shape to avoid sucking. The left tip was designed to be inserted into the left ventricle cavity. Five chronic BVAD bovine studies were performed to investigate the new beak shaped titanium tip. In these studies, the new beak shaped titanium tip and cannula prevented stenosis by a proliferation of pseudoneointimal, and supplied adequate blood flow to the pump without sucking. This newly designed inflow cannula with the beak shaped titanium tip was successfully implanted for 90 days.