Raymond K. Newswanger

Development of an inlet pressure sensor for control in a left ventricular assist device.

A Tesla type continuous flow left ventricular assist device (VAD) has been designed by Penn State and Advanced Bionics, Inc. (ABI). When a continuous flow device is used, care must be taken to limit low pressures in the ventricle, which can produce an obstruction to the inlet cannula or trigger arrhythmias. Design of an inexpensive, semiconductor strain gauge inlet pressure sensor to detect suction has been completed. The research and design analysis included finite element modeling of the sensing region. Sensitivity, step-response, temperature dependence, and hysteresis tests have been performed on prototype units. All sensors were able to withstand the maximum expected strain of 82 &mgr;m/in at 500 mm Hg internal pressure. Average sensitivity was 0.52 ± 0.24 &mgr;V/mm Hg with 0.5 V excitation (n = 5 units). Step-response time for a 0- to 90-mm Hg step change averaged 22 msec. Hysteresis was measured by applying and holding 75 mm Hg internal pressure for 4 hours, followed by a zero pressure measurement, and ranged from −15 to 4.1 mm Hg (n = 3 units). Offset drift varied between 180 and −140 mm Hg over a 4-week period (n = 2 units). Span temperature sensitivity ranged from 18 to −21 &mgr;V/°C (n = 5 units). Gain temperature sensitivity ranged from −7.4 to 4.9 &mgr;V/°C (n = 5 units). With the inherent drift, it is currently not possible to use the transducer to measure actual pressures, but it can easily be used to measure pressure changes throughout the cardiac cycle. This signal can then be used in the control system to avoid ventricular suction events.

A Passively-Suspended Tesla Pump Left Ventricular Assist Device

The design and initial test results of a new passively suspended Tesla type left ventricular assist device blood pump are described. Computational fluid dynamics (CFD) analysis was used in the design of the pump. Overall size of the prototype device is 50 mm in diameter and 75 mm in length. The pump rotor has a density lower than that of blood and when spinning inside the stator in blood it creates a buoyant centering force that suspends the rotor in the radial direction. The axial magnetic force between the rotor and stator restrain the rotor in the axial direction. The pump is capable of pumping up to 10 L/min at a 70 mm Hg head rise at 8,000 revolutions per minute (RPM). The pump has demonstrated a normalized index of hemolysis level below 0.02 mg/dL for flows between 2 and 9.7 L/min. An inlet pressure sensor has also been incorporated into the inlet cannula wall and will be used for control purposes. One initial in vivo study showed an encouraging result. Further CFD modeling refinements are planned and endurance testing of the device.

Tesla-Based Blood Pump and Its Applications

A continuous flow left ventricular assist device (LVAD) that the Penn State University has developed utilizes Tesla turbomachinery technology. Tesla pumping technology patented by Nikola Tesla in the early 20th century has multiple intriguing characteristics such as simpler manufacturing process, reduced turbulent-related stress, less cavitation due to viscous flow distribution over larger surface areas, and less hemolysis by smooth transition of fluid energy. We successfully tested the 1st version of the Penn State Tesla LVAD [1, 2]. We recently tested the 2nd version of the Tesla pump; to make the pump usable in a wide range of patients, the size of the pump was significantly reduced while trying to avoid any degradation of hemodynamic and hemolytic characteristics.Copyright

Targeting Cholesterol Transport in Circulating Melanoma Cells to Inhibit Metastasis

Despite recent breakthroughs in targeted‐ and immune‐based therapies, rapid development of drug resistance remains a hurdle for the long‐term treatment of patients with melanoma. Targeting metastatically spreading circulating tumor cells (CTCs) may provide an additional approach to manage melanoma. This study investigates whether targeting cholesterol transport in melanoma CTCs can retard metastasis development. Nanolipolee‐007, the liposomal form of leelamine, reduced melanoma metastasis in both a novel in vitro flow system mimicking the circulating system and in experimental as well as spontaneous animal metastasis models, irrespective of the BRAF mutational status of the CTCs. Leelamine led to cholesterol trapping in lysosomes, which subsequently shut down receptor‐mediated endocytosis, endosome trafficking, and inhibited the major oncogenic signaling cascades important for survival such as the AKT pathway. As pAKT is important in CTC survival, inhibition by targeting cholesterol metabolism led to apoptosis, suggesting this approach might be particularly effective for those CTCs having high levels of pAKT to aid survival in the circulation system.

Rotary blood pump control using integrated inlet pressure sensor

Due to improved reliability and reduced risk of thromboembolic events, continuous flow left ventricular assist devices are being used more commonly as a long term treatment for end-stage heart failure. As more and more patients with these devices are leaving the hospital, a reliable control system is needed that can adjust pump support in response to changes in physiologic demand. An inlet pressure sensor has been developed that can be integrated with existing assist devices. A control system has been designed to adjust pump speed based on peak-to-peak changes in inlet pressure. The inlet pressure sensor and control system have been tested with the HeartMate II axial flow blood pump using a mock circulatory loop and an active left ventricle model. The closed loop control system increased total systemic flow and reduced ventricular load following a change in preload as compared to fixed speed control. The increase in systemic flow occurred under all operating conditions, and maximum unloading occurred in the case of reduced ventricular contractility.