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ABSTRACT: MagScrew total artificial heart (TAH) external battery pack (EBP) cycle bench testing was conducted on two Wilson Greatbatch (Clarence, NY, USA) lithium ion EBPs over a period of 22 months during continuous charge and discharge cycles under a simulated TAH system current requirement. A custom electronic load was developed to simulate the MagScrew current waveforms typically observed during nominal operation. These current load profiles were applied to the EBP under test during a voltage-defined discharge cycle. EBP endurance indicated a 240-min discharge cycle on a new battery diminishing linearly to 175 min after 800 cycles. A second linear trend started at this knee with 150 min of discharge time at 850 cycles until 10 min at 1600 cycles. Even at 1300 cycles, the EBP could still provide enough power for 60 min of nominal operation. In conclusion, the endurance performance of this EBP was satisfactory while exhibiting a predictable wear-out trend.
Artificial Organs 10/2007; 31(9):698-702. · 2.00 Impact Factor
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Keiji Kamohara,
Stephan Weber,
Ryan S Klatte, Viviane Luangphakdy,
Christine R Flick,
Yoshio Ootaki,
Masatoshi Akiyama,
Faruk Cingoz,
Chiyo Ootaki,
Michael W Kopcak,
Jenny Liu,
Ji-Feng Chen,
Jose L Navia,
William A Smith,
Kiyotaka Fukamachi
[show abstract]
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ABSTRACT: To evaluate the effects of downsizing of the total artificial heart (TAH), we compared the anaerobic threshold (AT) values in calves with two different types of TAH (Cleveland Clinic-Nimbus TAH and the downsized MagScrew TAH). Exercise studies were performed using a treadmill in 12 calves. During the exercise, parameters to obtain the AT were measured. To evaluate the determinants of the AT, a linear regression analysis was performed between AT and potential variables. AT values from 29 studies revealed no significant differences between the two different TAHs, with no significant differences in hemodynamic or oxygen metabolic parameters. AT values correlated well with pump flow/body weight (Q) multiplied by the hemoglobin level, regardless of the TAH used. In conclusion, downsizing of the original TAH design did not reduce AT without any significant differences in hemodynamic or oxygen metabolic parameters during exercise in calves.
Artificial Organs 10/2007; 31(9):667-76. · 2.00 Impact Factor
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Soren Schenk,
Stephan Weber, Viviane Luangphakdy,
Ryan S Klatte,
Christine R Flick,
Ji-Feng Chen,
Michael W Kopcak,
Yoshio Ootaki,
Keiji Kamohara,
Gordon B Hirschman,
Nicholas G Vitale,
Peter A Chapman,
William A Smith,
Kiyotaka Fukamachi
[show abstract]
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ABSTRACT: Downsizing pulsatile devices requires an increase of beat rate if flow capacity is to be maintained. We applied this concept to the preclinical MagScrew total artificial heart (TAH).
The device fills passively with a stroke volume of 45 ml and beat rates up to 250 beats per minute (bpm).
Stable hemodynamics were observed during a 30-day bovine implant with a flow of 8.7 +/- 1.2 L/min at beat rates of 204 +/- 18 bpm. Device filling was exceptional up to 250 bpm generating flow of greater than 12 L/min. Beat rate adapted to preload in a way similar to a Frank-Starling response. Left and right atrial pressures were balanced. The aortic pulse pressure was 49-70 mm Hg, which translates to a pulsatility index of 0.49-0.77. Organ functions were preserved and blood damage did not occur.
Increasing the beat rate while downsizing the MagScrew TAH was successful with strong flow generation by passive filling. Pulsatility was maintained at high beat rates. This innovative approach may be used to develop small pulsatile pumps.
The Annals of thoracic surgery 05/2005; 79(4):1378-83; discussion 1383. · 3.74 Impact Factor
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Soren Schenk,
Stephan Weber, Viviane Luangphakdy,
Christine R. Flick,
Ji-Feng Chen,
Masahiro Inoue,
Michael W. Jr. Kopcak,
Yoshio Ootaki,
Kazuyoshi Doi,
Raymond Dessoffy,
Gordon B. Hirschman,
Nicholas G. Vitale,
Peter A. Jr. Chapman,
William A. Smith,
Kiyotaka Fukamachi
[show abstract]
[hide abstract]
ABSTRACT: Currently available ventricular assist devices (VADs) have limitations in long-term durability and blood compatibility. We evaluated a prototype of a pulsatile MagScrew VAD for in vivo hemodynamic performance and biocompatibility. The device is composed of an actuator, blood pump housing, diaphragm, pusher plate, and bioprosthetic valves. Its protein-coated (biolized) blood-contacting surface inhibits clot formation. Forces between moving parts of the actuator are transmitted magnetically, eliminating a primary source of friction and wear. The pump fills passively and is highly preload sensitive. The device was implanted into three calves for 90, 10, and 57 days, respectively. No anticoagulants were given postoperatively. The device functioned without technical problems during the entire course of each experiment, with mean device flow ranging between 5.4 and 9.0 L/min. Autopsy of the first two calves revealed no sign of embolization and clean blood-contacting surfaces of the devices. The third experiment was complicated by a prosthetic valve endocarditis with infectious embolization, and a few small depositions were found in the pump. In conclusion, the MagScrew VAD has demonstrated a high level of performance and biocompatibility in three calves studied for 10-90 days. Vigorous development is in progress to bring this device to preclinical readiness and thus provide surgeons with the VAD of choice for permanent implantation.
Mechanical circulatory support by ventricular assist devices (VADs) has been shown to improve survival, quality of life, and functional status in patients with end-stage congestive heart failure who are ineligible for heart transplantation. However, device failure was a common cause of death (17%), and the probability of device failure at 24 months was 35%. In addition, a high incidence of bleeding and thromboembolic events was seen in those patients, suggesting limited blood compatibility. 1 Studies have further demonstrated that the coagulation and fibrinolytic systems are activated during VAD support, resulting in a prothrombic environment and hemorrhagic complications. 2,3
The implantable, pulsatile MagScrew VAD, intended for long-term circulatory support, was developed in cooperation between the Cleveland Clinic Foundation (CCF, Cleveland, OH) and Foster-Miller Technologies, Inc. (Albany, NY). The actuator and blood pump share key components with the MagScrew total artificial heart (TAH), 4,5 allowing for a considerable reduction of costs in development and production. Forces are transmitted magnetically rather than mechanically, eliminating friction and wear in the conversion of rotational motion to translational actuation. The pump fills passively with a highly preload sensitive response. All blood-contacting surfaces are biolized by coating with a cross-linked gelatin layer, which inhibits clot formation in the absence of anticoagulation. This report describes our initial experience with the in vivo performance and biocompatibility of the MagScrew VAD.
ASAIO Journal 08/2003; 49(5):594-598. · 1.39 Impact Factor
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ABSTRACT: Incompetent inflow valves have been reported with clinical pulsatile left ventricular assist devices that use bioprosthetic valves. Suspected as the cause of premature valve failure within these devices, absolute pressures and instantaneous pressure changes were evaluated in the MagScrew total artificial heart (TAH). The MagScrew TAH is a passively filling pulsatile pump which uses a reciprocating magnetic actuating mechanism under various control modes to propel blood into circulation. Both right and left ejection speeds were modulated and optimized at the onset of hydraulic eject. These various speed profiles were evaluated in vitro at 220 beats per minute (bpm), 100% pump fill, mean aortic pressure of 100 mm Hg and mean pulmonary artery pressure of 20 mm Hg. The pressure inside the left and right pump chambers was measured with Millar Mikro-Tip catheter and captured using Power Lab at a rate of 40 kHz. The pump chamber peak pressure, operating with unmodified eject speeds, measured on average 183 mm Hg for the left and 133 mm Hg for the right. Eject speed profiling for both pumps reduced the peak pressure by 10% and 28% for the left and right pump, respectively. Future studies will assess software controlled optimization of the eject speed profiles under any operating condition and how effective it is in vivo.
ASAIO journal (American Society for Artificial Internal Organs: 1992) 54(1):58-63. · 1.39 Impact Factor
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Keiji Kamohara,
Stephan Weber,
Ryan S Klatte,
Yoshio Ootaki,
Masatoshi Akiyama,
Michael W Kopcak, Viviane Luangphakdy,
Christine R Flick,
Ji-Feng Chen,
Jose L Navia,
William A Smith,
Kiyotaka Fukamachi
[show abstract]
[hide abstract]
ABSTRACT: The MagScrew total artificial heart (TAH) is under development. Despite its anticipated durability and reliability, the possibility of a bioprosthetic valve malfunction exists. As a result, the potential for valve replacement surgery, instead of device replacement, would be desirable after a TAH implant. In two of our 90-day animal experiments, we successfully replaced the left-side valves through a left thoracotomy opposite to the right-sided incision site for the initial TAH implant. The results of these cases suggest that the left-side valves could also be replaced through a left thoracotomy approach in humans. To confirm the ability to access the left-side valves in humans, four human cadaver studies were performed with the use of a mock pump designed for human application. This report describes the operative techniques for left-side valve replacement in animals and discusses the advantages of a left thoracotomy in clinical situations, based on results from the human cadaver studies.
ASAIO Journal 52(4):368-72. · 1.39 Impact Factor
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Soren Schenk,
Stephan Weber, Viviane Luangphakdy,
Christine R Flick,
Ji-Feng Chen,
Masahiro Inoue,
Michael W Kopcak,
Yoshio Ootaki,
Kazuyoshi Doi,
Raymond Dessoffy,
Gordon B Hirschman,
Nicholas G Vitale,
Peter A Chapman,
William A Smith,
Kiyotaka Fukamachi
[show abstract]
[hide abstract]
ABSTRACT: Currently available ventricular assist devices (VADs) have limitations in long-term durability and blood compatibility. We evaluated a prototype of a pulsatile MagScrew VAD for in vivo hemodynamic performance and biocompatibility. The device is composed of an actuator, blood pump housing, diaphragm, pusher plate, and bioprosthetic valves. Its protein-coated ("biolized") blood-contacting surface inhibits clot formation. Forces between moving parts of the actuator are transmitted magnetically, eliminating a primary source of friction and wear. The pump fills passively and is highly preload sensitive. The device was implanted into three calves for 90, 10, and 57 days, respectively. No anticoagulants were given postoperatively. The device functioned without technical problems during the entire course of each experiment, with mean device flow ranging between 5.4 and 9.0 L/min. Autopsy of the first two calves revealed no sign of embolization and clean blood-contacting surfaces of the devices. The third experiment was complicated by a prosthetic valve endocarditis with infectious embolization, and a few small depositions were found in the pump. In conclusion, the MagScrew VAD has demonstrated a high level of performance and biocompatibility in three calves studied for 10-90 days. Vigorous development is in progress to bring this device to preclinical readiness and thus provide surgeons with the VAD of choice for permanent implantation.
ASAIO Journal 49(5):594-8. · 1.39 Impact Factor
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Stephan Weber,
Keiji Kamohara,
Ryan S Klatte, Viviane Luangphakdy,
Christine Flick,
Ji-Feng Chen,
Fernando Casas,
Yoshio Ootaki,
Michael Kopcak,
Masatoshi Akiyama,
Gordon B Hirschman,
Peter A Chapman,
Arthur Donahue,
William Wetterau,
Charles Prisco,
Roy Mast,
Craig Sherman,
Kiyotaka Fukamachi,
William A Smith
[show abstract]
[hide abstract]
ABSTRACT: The MagScrew Total Artificial Heart (TAH) system is the result of a close collaboration among the Cleveland Clinic Foundation, Foster Miller Technologies, Wilson Greatbatch Ltd, and Whalen Biomedical Inc. The system components are the thoracic blood pumping unit with attached compliance chamber and refill port, implantable electronic control unit, implantable battery pack, transcutaneous energy transmission system, external battery pack, and a telemetry system for communication with the electronic control unit. System in vitro tests are underway for system characterization and durability demonstration, whereas in vivo tests were conducted to evaluate system performance and biocompatibility under physiologic conditions. The passively filling pump uses a left master alternate left and right ejection control mode and has a Starling law-like response to venous pressure. The in vitro tests documented excellent hydraulic pump performance with high device output of over 9 l/min at left atrial pressures below 12 mm Hg. Atrial balance was well maintained under all test conditions. The in vivo tests demonstrated good biocompatibility without use of anticoagulant therapy. Experimental durations have ranged between 0 and 92 days. Postexplant evaluation of tissue samples did not reveal any sign of thromboembolic events or tissue damage due to device operation.
ASAIO Journal 51(6):xxxvi-xlvi. · 1.39 Impact Factor
