Biomedical subjects

K Horiuchi

Publications and source records attributed to K Horiuchi.

349 records · Page 20Linked to original sources

PubMedDate not supplied

Recent progress in the development of Terumo implantable left ventricular assist system.

The research group of the Terumo Corporation, the NTN Corporation, and Setsunan University (T. Akamatsu) has been developing an implantable left ventricular assist system (ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The impeller of the MSCP is suspended by a magnetic bearing, providing contact-free rotation of the impeller inside the pump housing. Thus the MSCP is expected to provide years of long-term durability. Ex vivo chronic sheep experiments using the extracorporeal model (Model I) demonstrated long-term durability, nonthrombogenicity, and a low hemolysis rate (plasma free Hb <6 mg/dl) for more than 2 years. The prototype implantable model (Model II; 196 ml, 400 g) was evaluated ex vivo in 2 sheep and intrathoracically implanted in a small sheep (45 kg). These experiments were terminated at 70, 79, and 17 days, respectively, because of blood leakage through the connector system within the housing of Model II. There was no thrombus formation on the retrieved pump surfaces. A new connector system was introduced to the Model II pump (modified Model II), and the pump was intrathoracically implanted in a sheep. Pump flow rate was maintained at 3-7 L/min at 1700-1800 rpm. The temperature elevation on the surfaces of the motor and the electromagnet inside the pump casing was kept less than 6 degrees C. The temperature of the tissue adjacent to the pump casing became normal 10 days postoperatively. The sheep survived for more than 5 months without any sign of mechanical failure or thromboembolic complication. In vitro real-time endurance tests of motor bearings made of stainless steel and silicone nitride have been conducted for more than 1 year without any sign of bearing wear. The next prototype system (Model III), with an implantable controller and a new MSCP with reduced input power, has been developed with a view toward a totally implantable LVAS.

Alanine Transaminase↗

PubMedDate not supplied

Terumo implantable left ventricular assist system: results of long-term animal study.

The research group of Terumo Corporation, NTN Corporation, and the Setsunan University have been developing an implantable left ventricular assist system (T-ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The present study describes results of chronic animal experiments using the MSCP. The MSCP has been tested ex vivo and in vivo in 6 sheep as a left heart bypass between the left ventricular apex and descending aorta. Ex vivo chronic sheep experiments using Model I demonstrated long-term durability, nonthrombogenicity, low hemolysis (<6 mg/dl), and excellent stability of the magnetic bearing with long-term survival for up to 864 days. Average pump flow rate was 4 L/min at a fixed rotational speed of 2000 rpm. Power spectral analyses of heart rate, aortic pressure, and blood temperature maintained normal 1/f fluctuation during the study. The retrieved pump was completely free from thrombus formation and there was no evidence of infarct in major organs. The implantable Model II was evaluated ex vivo in two sheep and intra-thoracically implanted in a sheep. These experiments were terminated at 70, 79, and 17 days due to blood leakage through the connector system within the housing. No thrombus formation was observed in any of the retrieved pumps. A modified Model II with a new connector system was subsequently intra-thoracically implanted in a sheep. The sheep survived for 482 days without any sign of thromboembolic complication or hemolysis at a fixed rotational speed of 1700 rpm and an average pump flow rate of 5 L/min. There was no intra-device thrombus formation or infarct in major organs. The Model III system, consisting of an implantable controller and a new MSCP with a reduced input power of 13 W, has been developed and implanted in a chronic sheep model. The MSCP was implanted in the left pleural space and the controller in the abdominal wall. The experiment is still in progress for more than 30 days without any significant complication to date. These animal studies strongly suggest the feasibility of the MSCP for use as long-term circulatory assist.

Animals↗

PubMedDate not supplied

Simultaneous recording of early and middle components of auditory electric response.

The auditory brain stem response (ABR) and the auditory middle response (AMR) were simultaneously recorded in 19 normal adults and 29 patients with hearing loss. The test was performed using tone pips at 0.5, 1, 2, and 4 kHz with intensity levels of 0, 10, 20, and 30 dB above the individual's behavioral threshold. A wide pass-band of 0.5 Hz to 3 kHz was used for recording the response. The typical waveform of the response provided six peaks that were successively labeled as P10, N15, P20, N25, P35, and N45. P10 was a large positive deflection in the ABR. N15-P20-N25, P35, and N45 corresponded to the Na peak complex, Pa, and Nb of the AMR, respectively. Of all components recorded, P10 was detected most consistently. However, because N25 and P35 of the AMR also gave important information for the assessment of hearing, simultaneous recording of the ABR and AMR is considered a useful clinical technique for estimating hearing in normal as well as in hearing-impaired subjects.

Acoustic Stimulation↗

PubMedDate not supplied

Gadolinium-phthalein complexone as a contrast agent for hepatobiliary MR imaging.

Gadolinium-phthalein complexone (Gd-PC) was developed as a hepatobiliary magnetic resonance (MR) contrast agent. Phthalein complexone is one of the iminodiacetic acid derivatives and a structural analogue of bromosulfophthalein. Gadolinium-PC substantially enhanced signal intensity of normal functioning livers on T1-weighted MR images. Contrast enhancement of rabbit liver and gradual accumulation of high intensity bile in the gallbladder were observed after intravenous injection of 0.05 and 0.1 mmol/kg Gd-PC. However, 0.1 mmol/kg of Gd-DTPA caused little effect on liver MR.

Animals↗

PubMedDate not supplied

Immediate loading of Brånemark system implants following placement in edentulous patients: a clinical report.

The purpose of this study was to evaluate the immediate loading of Brånemark System implants following placement with a screw-retained provisional prosthesis in edentulous patients. Twelve mandibular and 5 maxillary arches were treated from December 1997, including 3 bimaxillary patients. The provisional prosthesis, made of heat-polymerizing resin, had an inner casting of cobalt-chromium alloy to provide rigidity. The implants whose placement torque was more than 40 Ncm were immediately loaded. Implants that were placed with placement torque of less than 40 Ncm or that were associated with bone grafting were submerged. Following abutment connection, temporary cylinders were incorporated into the provisional prosthesis intraorally with autopolymerizing resin. After the provisional prosthesis was completed extraorally, it was screw-retained. After a 4- to 6-month healing period, a definitive prosthesis was fabricated and placed. Of the 140 immediately loaded implants, 136 osseointegrated during an 8- to 24-month follow-up period (97.2%). All 17 submerged implants osseointegrated. The results suggest that immediate loading of Brånemark System implants at the time of placement in edentulous patients can be a valuable adjunct to therapy and as predictable as delayed loading, in both mandibular and maxillary arches.

Adult↗

PubMedDate not supplied

Arterial and venous thrombus imaging using Ga-67 DFO-DAS-fibrinogen: its clinical applicability.

The purpose of this study was the clinical application of 67Ga-DFO-DAS-fibrinogen 67Ga-fibrinogen in normal volunteers and patients with arterial or venous therombus, or bypass graft. DFO-DAS-fibrinogen was available as a lyophilized product and easily labeled by simple mixing with 67Ga-fibrinogen solution (2 mCi/2 ml). Images were taken by a scintillation camera 72 hours after the venous injection of 67Ga-fibrinogen (2 mCi). Ga-67 fibrinogen accumulated well in the liver and kidney in normal volunteers at the early stage, and radioactivity in the kidney, lung, and heart decreased after noticeably after 48 hours postinjection. Ga-67 fibrinogen clearly visualized fresh and old arterial thrombi localized in the thorax or abdomen of all patients suffering aneurysm, and in occlusive bypass graft, contrary to past observations with labeled fibrinogen. In venous thrombus, with the pulmonary artery included, visualization was limited to fresh thrombi of up to one month old. No adverse side effects were observed in any case.

Aged↗

PubMedDate not supplied

More than 1 year continuous operation of a centrifugal pump with a magnetically suspended impeller.

The authors have been developing a centrifugal pump with a magnetically suspended impeller (MSCP) designed for total artificial heart and long-term ventricular support. The MSCP consists of a magnetic bearing, an impeller and housing, and a driving motor. The impeller is suspended by a magnetic bearing, therefore providing contact free rotation of the impeller inside the pump. This study was designed to evaluate long-term durability and nonthrombogenicity of the MSCP in a chronic sheep model. The blood contacting surfaces of the pump and conduits were completely modified by a heparin immobilization technique (Hepaface). The MSCP was placed paracorporeally as a left heart bypass between left ventricle and descending aorta in three adult sheep. Coumadin was given orally to maintain prothrombin time at 15-20 sec. The coagulation and hematologic parameters, including plasma free hemoglobin, were periodically monitored throughout the experiment. Under daily movement in the cage, the pump could produce average flow rates of 3-6 L/min (50-100 ml/kg) at 1,700-2,000 rpm. Although the arterial pulse contour decreased, there was no physiologic deterioration. The axial impeller excursion monitored by a position sensor was < 25 microns. Plasma free hemoglobin level remained at < 5 mg/dl throughout the experiment. There was no increase in the motor current, which indicates no massive thrombus formation around the impeller. One experiment was terminated at 70 days due to Hall sensor dysfunction of the motor. The retrieved pump was entirely free from thrombus formation. There was no detectable thrombus formation inside the pump or the inflow and outflow conduits. Hematologic, renal, and hepatic parameters remained within the normal range throughout the experiment. The other two sheep have survived for more than 395 and 41 days without major complication. These studies demonstrated that the MSCP has significant potential for long-term use.

Animals↗