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Kiyoyuki Eishi - One of the best experts on this subject based on the ideXlab platform.

  • Twelve years of experience with the ATS Mechanical Heart Valve prostheses
    General Thoracic and Cardiovascular Surgery, 2012
    Co-Authors: Shinichiro Taniguchi, Koji Hashizume, Tsuneo Ariyoshi, Yoichi Hisata, Kazuyoshi Tanigawa, Takashi Miura, Tomohiro Odate, Seiji Matsukuma, Shun Nakaji, Kiyoyuki Eishi
    Abstract:

    Objective The ATS Open Pivot Mechanical Heart Valve has been implanted routinely at our institution since 1999. The objective of this study is to retrospectively analyze our 12-year clinical results with ATS prostheses. Methods ATS Open Pivot Mechanical Valves were implanted in 268 adult patients between May 1999 and August 2010. We selected 259 subjects who could be adequately followed (follow-up rate 96.6 %). Aortic Valve replacement was performed in 157 patients, mitral Valve replacement (MVR) in 71, and double (aortic and mitral) Valve replacements (DVR) in 31. Mean age at the time of implant was 58.8 ± 10.6 years. The gender ratio was 128 males/131 females. Mean follow-up was 4.4 ± 7.8 years, and the cumulative follow-up was 1144 patient-years (pt-yr). Results Early death within 30 days after the operation occurred in 5 (2.5 %) patients. Late death occurred in 27 patients including Valve-related deaths in 13. The 10-year survival rate after the operation was 82.7 ± 2.9 %. The rate of freedom from Valve-related death was 92.2 ± 2.2 %. The incidence of Valve-related complications was 2.19 %/pt-yr. Of these, the incidence of thromboembolic events and that of bleeding complications were 1.22 and that 0.87 %/pt-yr. The incidence of Valve thrombosis was 0.09 %/pt-yr. No structural Valve deterioration was observed in any of the three operative procedure groups. Conclusions Our 12-year experience with aortic and MVR using the ATS Mechanical Heart Valve demonstrated low incidences of thromboembolic events, bleeding complications, and Valve thrombosis.

  • Twelve years of experience with the ATS Mechanical Heart Valve prostheses
    General thoracic and cardiovascular surgery, 2012
    Co-Authors: Shinichiro Taniguchi, Koji Hashizume, Tsuneo Ariyoshi, Yoichi Hisata, Kazuyoshi Tanigawa, Takashi Miura, Tomohiro Odate, Seiji Matsukuma, Shun Nakaji, Kiyoyuki Eishi
    Abstract:

    Objective The ATS Open Pivot Mechanical Heart Valve has been implanted routinely at our institution since 1999. The objective of this study is to retrospectively analyze our 12-year clinical results with ATS prostheses.

Yoshiyuki Taenaka - One of the best experts on this subject based on the ideXlab platform.

  • Observation of cavitation pits on Mechanical Heart Valve surfaces in an artificial Heart used in in vitro testing.
    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, 2010
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Akihiko Homma, Yoshiyuki Taenaka
    Abstract:

    Our group has developed an electrohydraulic total artificial Heart (EHTAH) with two diaphragm-type blood pumps. Cavitation in a Mechanical Heart Valve (MHV) causes Valve surface damage. The objective of this study was to investigate the possibility of estimating the MHV cavitation intensity using the slope of the driving pressure just before Valve closure in this artificial Heart. Twenty-five and twenty-three-millimeter Medtronic Hall Valves were mounted at the inlet and outlet ports, respectively, of both pumps. The EHTAH was connected to the experimental endurance tester developed by our group, and tested under physiological pressure conditions. Cavitation pits could be seen on the inlet Valve surface and on the outlet Valve surface of the right and left blood pumps. The pits on the inlet Valves were more severe than those on the outlet Valves in both blood pumps, and the cavitation pits on the inlet Valve of the left blood pump were more severe than those on the inlet Valve of the right blood pump. The longer the pump running time, the more severe the cavitation pits on the Valve surfaces. Cavitation pits were concentrated near the contact area with the Valve stop. The major cause of these pits was the squeeze flow between the leaflet and Valve stop.

  • Observation of cavitation pits on a Mechanical Heart Valve surface in an artificial Heart used in in vivo testing.
    Journal of Artificial Organs, 2009
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Akihiko Homma, Yoshiyuki Taenaka
    Abstract:

    Our group has developed an electrohydraulic total artificial Heart (EHTAH) with two diaphragm-type blood pumps. Cavitation in a Mechanical Heart Valve (MHV) causes Valve surface damage. The objective of this study was to investigate the possibility of estimating the MHV cavitation intensity using the slope of the driving pressure just before Valve closure in this artificial Heart. Twenty-five and twenty-three-millimeter Medtronic Hall Valves were mounted at the inlet and outlet ports, respectively, of both pumps. The EHTAH was connected to the experimental endurance tester developed by our group, and tested under physiological pressure conditions. Cavitation pits could be seen on the inlet Valve surface and on the outlet Valve surface of the right and left blood pumps. The pits on the inlet Valves were more severe than those on the outlet Valves in both blood pumps, and the cavitation pits on the inlet Valve of the left blood pump were more severe than those on the inlet Valve of the right blood pump. The longer the pump running time, the more severe the cavitation pits on the Valve surfaces. Cavitation pits were concentrated near the contact area with the Valve stop. The major cause of these pits was the squeeze flow between the leaflet and Valve stop.

  • Characteristics of cavitation intensity in a Mechanical Heart Valve using a pulsatile device: synchronized analysis between visual images and pressure signals
    Journal of Artificial Organs, 2008
    Co-Authors: Eiki Akagawa, Eisuke Tatsumi, Yoshiyuki Taenaka
    Abstract:

    To investigate the characteristics of cavitation intensity, we performed a synchronized analysis of the visual images of cavitation and the pressure signals using a pulsatile device. The pulsatile device employed was a pneumatic ventricular assist device (PVAD) that is currently being developed by our group. A 23-mm Medtronic Hall Valve (M-H Valve) and a 23-mm Sorin Bicarbon bileaflet Valve (S-B Valve) were mounted in the inlet port of the PVAD after the sewing ring had been removed. A function generator provided a square signal, which was used as the trigger signal, via Electrocardiogram R wave (ECG-R) mode, of the control — drive console for circulatory support. The square signal was also used, after a suitable delay, to synchronize operation of a pressure sensor and a high-speed video camera. The data were stored using a digital oscilloscope at a 1-MHz sampling rate, and then the pressure signal was band-pass filtered between 35 and 200 kHz using a digital filter. The Valve-closing velocity, visual cavitation time, and root mean square (RMS) pressure of the M-H Valve were greater than those of the S-B Valve. Both the visual cavitation time and RMS pressure represent the cavitation intensity, and this is a very important factor when estimating Mechanical Heart Valve cavitation intensity in an artificial Heart.

  • Effect of systolic duration on Mechanical Heart Valve cavitation in a pneumatic ventricular assist device: using a monoleaflet Valve.
    Asaio Journal, 2008
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Yoshiyuki Taenaka
    Abstract:

    : The cavitation intensity of a Mechanical Heart Valve (MHV) may differ according to the geometry of the blood pump and driving mechanism. Our group is currently developing a pneumatic ventricular assist device (VAD), and the effects of different operating conditions on MHV cavitation in our pneumatic VAD were investigated. Tests were conducted under physiological pressure at Heart rates ranging from 60 to 90 beats/min and at a systolic duration ranging from 38% to 43%. The Valve-closing velocity was measured using a charge-coupled device (CCD) laser displacement sensor, and images of MHV cavitation were recorded using a high-speed video camera. A miniature pressure sensor was mounted 10 mm away from the inlet Valve surface. The data were stored at a 1-MHz sampling rate using a digital oscilloscope. The pressure signal was band-pass filtered between 35 and 200 kHz using a digital filter. The cavitation bubbles were concentrated at the inlet Valve stop, and were caused mainly by the squeeze flow. The band-pass filtered root mean squared (RMS) pressure and cavitation cycle duration increased with the closing velocity of the inlet Valve. At a low Heart rate and low systolic duration, the inlet Valve closed before the outlet Valve opened, which caused no cavitation bubbles to form around the Valve stop.

  • Observation and quantification of cavitation on a Mechanical Heart Valve with an electro-hydraulic total artificial Heart.
    The International journal of artificial organs, 2006
    Co-Authors: Hwansung Lee, Yoshiyuki Taenaka
    Abstract:

    In previous studies, we investigated the cavitation phenomenon in a Mechanical Heart Valve using an electro-hydraulic total artificial Heart. With this system, a 50% glycerin solution kept at 37 degrees C was used as the working fluid. We reported that most of the cavitation bubbles were observed near the Valve stop and were caused by the squeeze flow. However, in these studies, the effect of the partial pressure of CO(2) on the Mechanical Heart Valve cavitation was neglected. In this study, in order to investigate the effect of the partial pressure of CO(2) on Mechanical Heart Valve cavitation using an electro-hydraulic total artificial Heart, we controlled the partial pressure of the CO(2) in vitro. A 25-mm Medtronic Hall Valve was installed in the mitral position of an electro-hydraulic total artificial Heart. In order to quantify the Mechanical Heart Valve cavitation, we used a high-speed camera. Even though cavitation intensity slightly increased with increases in the PCO(2) at Heart rates of 60, 70 and 100 bpm, throughout the experiment, there was no significant difference between the PCO(2) and cavitation intensity.

Shinichiro Taniguchi - One of the best experts on this subject based on the ideXlab platform.

  • Twelve years of experience with the ATS Mechanical Heart Valve prostheses
    General Thoracic and Cardiovascular Surgery, 2012
    Co-Authors: Shinichiro Taniguchi, Koji Hashizume, Tsuneo Ariyoshi, Yoichi Hisata, Kazuyoshi Tanigawa, Takashi Miura, Tomohiro Odate, Seiji Matsukuma, Shun Nakaji, Kiyoyuki Eishi
    Abstract:

    Objective The ATS Open Pivot Mechanical Heart Valve has been implanted routinely at our institution since 1999. The objective of this study is to retrospectively analyze our 12-year clinical results with ATS prostheses. Methods ATS Open Pivot Mechanical Valves were implanted in 268 adult patients between May 1999 and August 2010. We selected 259 subjects who could be adequately followed (follow-up rate 96.6 %). Aortic Valve replacement was performed in 157 patients, mitral Valve replacement (MVR) in 71, and double (aortic and mitral) Valve replacements (DVR) in 31. Mean age at the time of implant was 58.8 ± 10.6 years. The gender ratio was 128 males/131 females. Mean follow-up was 4.4 ± 7.8 years, and the cumulative follow-up was 1144 patient-years (pt-yr). Results Early death within 30 days after the operation occurred in 5 (2.5 %) patients. Late death occurred in 27 patients including Valve-related deaths in 13. The 10-year survival rate after the operation was 82.7 ± 2.9 %. The rate of freedom from Valve-related death was 92.2 ± 2.2 %. The incidence of Valve-related complications was 2.19 %/pt-yr. Of these, the incidence of thromboembolic events and that of bleeding complications were 1.22 and that 0.87 %/pt-yr. The incidence of Valve thrombosis was 0.09 %/pt-yr. No structural Valve deterioration was observed in any of the three operative procedure groups. Conclusions Our 12-year experience with aortic and MVR using the ATS Mechanical Heart Valve demonstrated low incidences of thromboembolic events, bleeding complications, and Valve thrombosis.

  • Twelve years of experience with the ATS Mechanical Heart Valve prostheses
    General thoracic and cardiovascular surgery, 2012
    Co-Authors: Shinichiro Taniguchi, Koji Hashizume, Tsuneo Ariyoshi, Yoichi Hisata, Kazuyoshi Tanigawa, Takashi Miura, Tomohiro Odate, Seiji Matsukuma, Shun Nakaji, Kiyoyuki Eishi
    Abstract:

    Objective The ATS Open Pivot Mechanical Heart Valve has been implanted routinely at our institution since 1999. The objective of this study is to retrospectively analyze our 12-year clinical results with ATS prostheses.

Hwansung Lee - One of the best experts on this subject based on the ideXlab platform.

  • Observation of cavitation pits on Mechanical Heart Valve surfaces in an artificial Heart used in in vitro testing.
    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, 2010
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Akihiko Homma, Yoshiyuki Taenaka
    Abstract:

    Our group has developed an electrohydraulic total artificial Heart (EHTAH) with two diaphragm-type blood pumps. Cavitation in a Mechanical Heart Valve (MHV) causes Valve surface damage. The objective of this study was to investigate the possibility of estimating the MHV cavitation intensity using the slope of the driving pressure just before Valve closure in this artificial Heart. Twenty-five and twenty-three-millimeter Medtronic Hall Valves were mounted at the inlet and outlet ports, respectively, of both pumps. The EHTAH was connected to the experimental endurance tester developed by our group, and tested under physiological pressure conditions. Cavitation pits could be seen on the inlet Valve surface and on the outlet Valve surface of the right and left blood pumps. The pits on the inlet Valves were more severe than those on the outlet Valves in both blood pumps, and the cavitation pits on the inlet Valve of the left blood pump were more severe than those on the inlet Valve of the right blood pump. The longer the pump running time, the more severe the cavitation pits on the Valve surfaces. Cavitation pits were concentrated near the contact area with the Valve stop. The major cause of these pits was the squeeze flow between the leaflet and Valve stop.

  • Observation of cavitation pits on a Mechanical Heart Valve surface in an artificial Heart used in in vivo testing.
    Journal of Artificial Organs, 2009
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Akihiko Homma, Yoshiyuki Taenaka
    Abstract:

    Our group has developed an electrohydraulic total artificial Heart (EHTAH) with two diaphragm-type blood pumps. Cavitation in a Mechanical Heart Valve (MHV) causes Valve surface damage. The objective of this study was to investigate the possibility of estimating the MHV cavitation intensity using the slope of the driving pressure just before Valve closure in this artificial Heart. Twenty-five and twenty-three-millimeter Medtronic Hall Valves were mounted at the inlet and outlet ports, respectively, of both pumps. The EHTAH was connected to the experimental endurance tester developed by our group, and tested under physiological pressure conditions. Cavitation pits could be seen on the inlet Valve surface and on the outlet Valve surface of the right and left blood pumps. The pits on the inlet Valves were more severe than those on the outlet Valves in both blood pumps, and the cavitation pits on the inlet Valve of the left blood pump were more severe than those on the inlet Valve of the right blood pump. The longer the pump running time, the more severe the cavitation pits on the Valve surfaces. Cavitation pits were concentrated near the contact area with the Valve stop. The major cause of these pits was the squeeze flow between the leaflet and Valve stop.

  • Effect of systolic duration on Mechanical Heart Valve cavitation in a pneumatic ventricular assist device: using a monoleaflet Valve.
    Asaio Journal, 2008
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Yoshiyuki Taenaka
    Abstract:

    : The cavitation intensity of a Mechanical Heart Valve (MHV) may differ according to the geometry of the blood pump and driving mechanism. Our group is currently developing a pneumatic ventricular assist device (VAD), and the effects of different operating conditions on MHV cavitation in our pneumatic VAD were investigated. Tests were conducted under physiological pressure at Heart rates ranging from 60 to 90 beats/min and at a systolic duration ranging from 38% to 43%. The Valve-closing velocity was measured using a charge-coupled device (CCD) laser displacement sensor, and images of MHV cavitation were recorded using a high-speed video camera. A miniature pressure sensor was mounted 10 mm away from the inlet Valve surface. The data were stored at a 1-MHz sampling rate using a digital oscilloscope. The pressure signal was band-pass filtered between 35 and 200 kHz using a digital filter. The cavitation bubbles were concentrated at the inlet Valve stop, and were caused mainly by the squeeze flow. The band-pass filtered root mean squared (RMS) pressure and cavitation cycle duration increased with the closing velocity of the inlet Valve. At a low Heart rate and low systolic duration, the inlet Valve closed before the outlet Valve opened, which caused no cavitation bubbles to form around the Valve stop.

  • Observation and quantification of cavitation on a Mechanical Heart Valve with an electro-hydraulic total artificial Heart.
    The International journal of artificial organs, 2006
    Co-Authors: Hwansung Lee, Yoshiyuki Taenaka
    Abstract:

    In previous studies, we investigated the cavitation phenomenon in a Mechanical Heart Valve using an electro-hydraulic total artificial Heart. With this system, a 50% glycerin solution kept at 37 degrees C was used as the working fluid. We reported that most of the cavitation bubbles were observed near the Valve stop and were caused by the squeeze flow. However, in these studies, the effect of the partial pressure of CO(2) on the Mechanical Heart Valve cavitation was neglected. In this study, in order to investigate the effect of the partial pressure of CO(2) on Mechanical Heart Valve cavitation using an electro-hydraulic total artificial Heart, we controlled the partial pressure of the CO(2) in vitro. A 25-mm Medtronic Hall Valve was installed in the mitral position of an electro-hydraulic total artificial Heart. In order to quantify the Mechanical Heart Valve cavitation, we used a high-speed camera. Even though cavitation intensity slightly increased with increases in the PCO(2) at Heart rates of 60, 70 and 100 bpm, throughout the experiment, there was no significant difference between the PCO(2) and cavitation intensity.

  • Closing behavior of the Mechanical Heart Valve in a total artificial Heart.
    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, 2003
    Co-Authors: Hwansung Lee, Eisuke Tatsumi, Yoshiyuki Taenaka, Akihiko Homma, Tomonori Tsukiya, Hisateru Takano
    Abstract:

    Recently, cavitation on the surface of Mechanical Heart Valves has been studied as a cause of fractures occurring in implanted Mechanical Heart Valves. The cause of cavitation in Mechanical Heart Valve was investigated in both 25-mm Bjork–Shiley and 25-mm Medtronic Hall Valves. The closing events of these Valves in the mitral position were simulated in an electrohydraulic total artificial Heart with a stroke volume of 85 ml. The tests were conducted under physiologic pressures at Heart rates of 60, 70, 80, and 90 beats/min with cardiac outputs of 4.5, 5.5, 6.4, and 7.5 l/min, respectively. The disk closing behavior was measured by a laser displacement sensor. The closing behaviors were investigated under various atrial and aortic pressures. In both Valves, the duration of closing decreased with an increase in the cardiac output. The greater the amount of atrial pressure, the shorter the closing duration of both Valves. The maximum closing velocity of the Medtronic Hall monostrut Valve ranged from 0.8 to 0.9 m/s, and that of the Bjork–Shiley monostrut Valve ranged from 0.73 to 0.78 m/s. In both Valves, the maximum closing velocities were less than the reported cavitation thresholds. This suggests that there should be no possibility of occurrence of cavitation in an electrohydraulic total artificial Heart with Mechanical Heart Valve.

Anders Själander - One of the best experts on this subject based on the ideXlab platform.