髙味 良行

The improvement of antithrombogenicity is one of the major objectives for the development of blood pumps. Previously we reported that an in vitro thrombogenic test was useful as a pilot study, especially to predict thrombogenic areas. In this study we modified the method for testing pumps with identical priming volumes by eliminating the blood reservoir. Identical compact mock loops (priming volume of 53 mi, without pump) were constructed and tested with the same priming volume of Nikkiso centrifugal pumps, noncoated versus heparin-coated. Two pumps mere run simultaneously using the same source of fresh heparinized human blood (activated clotting time [ACT] 150-250 a) for 4 or 6 h. Results indicated that the heparin-coated pump had a longer thrombus free period than the noncoated one. The thrombi location and forms were consistently in the same places the in vivo study had identified. It is suggested that this modified in vitro thrombogenic test is a feasible pilot study, as well as the one previously reported. The minimal priming volume will allow evaluation of multiple pumps simultaneously with the same source blood.

Centrifugal pumps are generally employed as nonpulsatile blood flow pumps; however, these pumps can produce pulsatile flow by periodically alternating the impeller rotation speed, This study investigates blood trauma due to the effect of pulse frequency and various ranges of pump speed. The hemolysis tests were conducted using the Gyro C1E3 pump. The study was divided into the following categories: Group 1 in a nonpulsatile mode: Group 2 operated at 40 bpm with 30% of speed variance; Group 3, 60 bpm with 30% of speed variance: Group 4, 40 bpm with 70% of speed variance; and Group 5, 60 bpm with 70% of speed variance. A flow rate of 3 L/min and a total pressure head of 200 mm Hg were employed in all groups to simulate a percutaneous cardiopulmonary support condition. There were no significant differences in the hemolysis levels among Groups 1, 2, and 3. However, Groups 4 and 5 exhibited a significantly higher hemolysis rate compared to the other groups. These results indicate that a high rate of speed variance increases hemolysis: however, a range of less than 30% does not affect hemolysis. The pulse rate has no significant effect on hemolysis. In conclusion, the higher speed variance increases the hemolysis level when a pulsatile mode is applied with a centrifugal pump at the given test conditions. However, a speed variance of less than 30% or a pulse rate of less than 60 bpm does not affect hemolysis.

Due to the fact that centrifugal and axial pumps do not require valves, there is a possibility of back flow when the pump speed is low. To estimate the minimum required pump speed to prevent this regurgitation: an in vitro simulation test was conducted. A pulsatile pump simulated the natural heart while a centrifugal pump simulated the continuous flow left ventricular assist device (LVAD). The LVAD flow was attained from the left atrial (LA) drainage or left ventricular (LV) drainage, The minimum or regurgitate flow was observed in the systolic phase with LA drainage and in the diastolic phase with LV drain age. LV drainage always provided higher now than LA drainage at the same pump speed. These differences are due to the various total pressure heads of the LVAD. To prevent the regurgitation, the LVAD should maintain a certain pump speed which can create positive flow against the aortic systolic pressure with LA drainage and against the aortic diastolic pressure with LV drainage. These required pump speeds can be identified by the LVAD flow pressure curve.

The Gyro C1E3 pump has been developed as a completely sealless centrifugal pump driven by a magnetic coupling system for long-term usage. The Gyro C1E3 pump is a pivot bearing-supported pump in which the impeller is supported with the top and bottom pivot bearings, In the Gyro C1E3 pump, the impeller spinning is affected by the force balance between the floating force (Ff[N]) of the hydrodynamic effect and the magnetic thrust force (Tf[N]). The authors quantitatively investigated the floating force of the impeller in vitro to determine the magnetic coupling distance (MCD[mm]) that would result in stable impeller spinning, In vitro tests were performed using a loop filled with 37% glycerin solution to obtain the relationship between the MCD and floating speed (RS; rotational speed when the impeller starts floating [rpm]) and the relationship between the MCD and Tf. From the obtained relationships, we calculated FS and determined the relationship between the Ff and the rotational speed (R),Furthermore, we determined the relationship between d (minimum required MCD [mm]) and R from the results of determining the relationship of the MCD and Tf and of the Ff and R. The following relationships were obtained: Rf = 6.24.10(4).MCD-1.35; Tf = 5.27.10(3).MCD-2.29; Ff = 4.71.10(-6).RPM1.69; and d = 9.02.RPM-0.85 where RPM is the rotational speed. It was demonstrated that the floating force of the impeller is a function only of the rotational speed in the pivot bearing-supported Gyro C1E3 pump. The floating force is estimated to be 10 N to 40 N al rotational speeds of 1,500 rpm to 3,000 rpm at which the Gyro pump may be used in most clinical situations. It would be possible to control the impeller position of the Gyro pump automatically at the stable spinning condition by controlling the adequate magnetic coupling distance based upon its relationship with the rotational speed which was obtained in this study.

It is acknowledged that pulsatile Bow enhances the gas exchange performance of membrane oxygenators. However, the data for currently developed oxygenators are limited. In this study, the effect of pulsatile flow was assessed utilizing the MENOX EL-4000 oxygenator. The in vitro test was performed following the Association for the Advancement of Medical Instrumentation (AAMI) standards. Pulsatile flow was produced by the Gyro C1-E3 centrifugal pump with periodical changing of the impeller speed. In Study 1: the following 3 groups were created and examined: nonpulsatile flow, pulsatile now of 40 bpm; and pulsatile flow of 60 bpm. The blood flow rate was maintained at 3 L/min, and the V/Q ratio was I. In Study 2, four groups were examined, nonpulsatile flow with V/Q = 1, nonpulsatile with V/Q = 2, pulsatile with V/Q = 1, and pulsatile with V/Q = 2. The blood flow rate was maintained at 4 L/min, and the pulse frequency was set at 40 bpm. In study 1, although O-2 transfer was not enhanced, CO2 transfer was significantly improved (40-50%) by pulsatile now, regardless of pulse frequency. Study 2 demonstrated that pulsatile now resulted in improved CO, transfer as did higher ventilation (V/Q = 2). Furthermore, even after applying higher ventilation, the pulsatile mode enhanced CO2 transfer more than the nonpulsatiIe mode. It was considered that the pulsatile mode induced an active secondary flow and enhanced mixing effects, and consequently CO2 transfer was improved. In conclusion, the pulsatile flow significantly enhanced the CO2 transfer of the MENOX oxygenator. It is indicated that applying the pulsatile mode is a unique and effective method to improve the gas exchange performance for a current membrane oxygenator.

A miniaturized pivot bearing-supported centrifugal blood pump (Gyro PI) has been developed as a long-term biventricular assist system (BiVAS). In this study we determined the anatomical configuration of this system using a bovine model. Under general anesthesia, a left lateral thoracotomy was performed to open the chest. Two Gyro PI-601 pumps for left and right assists were placed in the preperitoneal pocket by a subcostal abdominal incision. The left pump could be placed along the dome of the diaphragm just beneath the apex of the left ventricle. The right pump could be placed next to the left pump. The inlet and outlet ports of both pumps penetrated the diaphragm. The inlet port of the left pump, with a length of 55 mm, was inserted directly into the apex of the left ventricle. A woven Dacron graft (150 mm long, 11 mm inner diameter) was placed between the outlet port of the left pump and the descending aorta. As for the right pump, a 100 mm long and 120 degree angled inflow conduit was placed between the inlet port and the right ventricular infundibulum. The outlet port of the right pump was connected to the main trunk of the pulmonary artery using a 90 mm long. II mm inner diameter Dacron graft. We could perform biventricular assistance to confirm the anatomical feasibility of the Gyro implantable centrifugal BiVAS.

Because pump efficiency is closely related to heat generation and blood trauma in a centrifugal blood pump, it is quite important to study pump efficiencies in a variety of conditions. In the present study, pump efficiencies were mapped on the pressure head-flow rate curves of 4 different pumps; BioMedicus BioPump (BP-80), Nikkiso (NK), Gyro C1E3, and Gyro PI601 (diameter of the impeller, NK: 50 mm, C1E3: 65 mm, and PI601: 50 mm). The mapping of pump efficiency revealed the following findings. First, the cone type (BP-80) has less pump efficiency than the impeller type (NK and C1E3); second, the miniaturization of the C1E3 to the PI601 has resulted in an increase in pump efficiency; and third, the diameter of the impeller may contribute to the pump efficiency of an impeller type pump. The mapping of the pump efficiency, as demonstrated in this study, is useful for the analysis of hydraulic pump performance in a wide range of clinically applied conditions.

To clarify the correlation between vibration and thrombus formation in a centrifugal blood pump, a preliminary simulated thrombus study was conducted for possible detection of thrombus formation inside a pump. Additional in vitro thrombogenesis studies were performed to confirm the results of the preliminary study. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, Endevco, San Juan Capistrano, CA, U.S.A.), a digitizing oscilloscope (TDS 420, Tektronix, Inc., MA, U.S.A.), and pivot bearing centrifugal pumps. The accelerometer was mounted to the top of the pump casing to sense radial and axial accelerations. For the preliminary study, a piece of Silastic was adhered to each of the 3 common areas of thrombus formation inside the pump. The results provided baseline information to speculate on the possibility of detecting thrombus formation by vibration signal changes. For the next studies, fresh bovine blood was harvested under sterile conditions and with strict avoidance of air contact. adding 1.0 U/ml of heparin. The sterilized test circuit consisted of 3/8 inch tubing (Tygon) and a soft reservoir. During the operating time, the activated clotting time (ACT) was maintained between 150 to 300 s using protamin. A restrictor on the outflow tube maintained the flow rates at about 4.5 L/min. The pumps ran continuously for 6 h. Possible blood clot formation inside the pump was monitored by observing the vibration signal from the device for 6 h. These studies revealed that it was possible to distinguish between an impeller that did not form thrombus and ones that formed fibrogenous thrombus using vibration signal assessment. Vibration assessment is worthwhile as a thrombus monitoring tool for a centrifugal blood pump.

While a centrifugal pump is generally used for nonpulsatile blood flow, it can also produce a pulsatile flow by alternating the impeller rotational speed (rpm) periodically. However, there is concern that this centrifugal pump pulsatile mode may induce added hemolysis as a result of the repeated acceleration and deceleration of rpm. Thus, a hemolysis study of the pulsatile modes of the Gyro C1E3 centrifugal pump (Gyro-P) was conducted. The results were then compared with the nonpulsatile mode of the same Gyro pump (Gyro-N) and the nonpulsatile BioMedicus BP-80 (Bio-N) pump. Three different conditions were simulated: left ventricular assist device (LVAD), cardiopulmonary bypass (CPB), and percutaneous cardiopulmonary support (PCPS). The beating rate of the Gyro-P was set at 40 bpm, with repetition of 2 different impeller speeds (the lower rpm being 70% of the higher speed). The 2 impeller speeds were set to obtain the same average flow as that of the nonpulsatile mode. The hemolysis results of the Gyro-P were comparable to or better than those of the Bio-N, and no excessive hemolysis was observed, compared to the Gyro-N. In conclusion, the Gyro-P had an excellent hemolytic characteristic and generated no excessive hemolysis in most clinical usage conditions. With the concern of hemolysis eliminated, this pulsatile mode may have various possible advantages.

To be able to salvage heart failure patients, the need for an economical permanent ventricular assist device is increasing. To meet this increasing demand, a miniaturized centrifugal blood pump has been developed as a permanently implantable device. The Gyro permanently implantable model (PI-601) incorporates a sealless design with a blood stagnation free structure. The pump impeller is magnetically coupled to the driver magnet in a sealless manner. This pump is atraumatic and antithrombogenic and incorporates a double pivot bearing system. A miniaturized actuator was utilized in this system in collaboration with the University of Vienna. The priming volume of this pump is 20 ml. The overall size of the pump actuator package is 53 mm in height and 65 mm in diameter, 145 ml of displacement volume, and 305 g in weight. Testing to date has included in vitro hydraulic performance and hemolysis. This pump can provide 5 L/min against a 110 mm Kg total pressure head at 2,000 rpm and 8 L/min against 150 mm Hg at 2,500 rpm. The normalized index of hemolysis (NIH) value of this pump was 0.0028 g/100 L at 5 L/min against 100 mm Kg. A preliminary anatomical study revealed the possibility of the implantability of 2 such systems in biventricular bypass at a preperitoneal location. This system is feasible for use as a permanently implantable biventricular assist device.

During a particular long-term in vitro hemolysis test, the plasma free hemoglobin suddenly increased even though the hemolysis level had risen linearly for the previous several hours. This phenomenon was dubbed the total destruction of erythrocytes (TDE) phenomenon, and it was hypothesized that this was the result of the accumulation of sublethal damage to erythrocytes. It was suggested that the TDE might demonstrate the hemolytic characteristics of a pump more sensitively than a conventional hemolysis test. However, the previous report did not consider the effects of temperature or contamination, To study these effects, 3 long-term hemolysis tests were concluded under the following conditions. For Study 1 blood temperature was maintained at 27 degrees C (n = 2); for Study 2, at 37 degrees C (n = 4): and for Study 3, at 37 degrees C with gentamicin (n = 4). The BioMedicus and Nikkiso pumps were used as they were in our previous report. Gas sterilization of all circuits and pumps preceded experimentation. In Studies 1 and 3, hemolysis increased linearly for 29 h. However, in Study 2 a sudden increase of hemolysis occurred for both pumps. Possible causes of this were the dramatic changes in environmental factors such as severe acidosis, high O-2 and glucose consumption, and CO2 accumulation. In contrast, neither Study 1 nor Study 3 showed a sudden increase in hemolysis. The plasma free hemoglobin increased linearly in both groups until 29 h of pumping. The environmental changes resulting from contamination were considered to be the cause of the sudden increase in hemolysis. In conclusion, the TDE did not reflect mechanical blood cell damage, but rather different environment situations. Hemolysis increased linearly up to 29 h in either 27 degrees C or germ-free conditions.

The compact eccentric inlet port (C1E3) centrifugal blood pump was developed as a cardiopulmonary bypass (CPB) pump. The C1E3 pump incorporated a seal-less design with a blood stagnation free structure. The pump impeller was magnetically coupled to the driver magnet in a seal-less manner. To develop an atraumatic and antithrombogenic centrifugal pump without a shaft seal junction, a double pivot bearing system was introduced. Recently, a mass production model of the C1E3 was fabricated and evaluated. The ratio of the normalized index of hemolysis (NIH) of the C1E3 was 0.007 g/100 L, in comparison to the NIH of the BP-80, 0.018 g/100 L, each in a CPB condition of 5 L/min against 325 mm Hg. Both pumps were compared in identical in vitro circuits. To further evaluate the pumps during cardiopulmonary bypass for reliability and function, 6 h of CPB was performed on each of 8 bovines using either the C1E3 or BP-80 centrifugal pump. The BP-80 and C1E3 provided pump flows of 50-60 ml/kg/min without incident. The hemodynamics were stable, and the hematology and biochemistry data were within normal ranges. There were no statistically significant differences between the 2 groups. Concerning the plasma free hemoglobin values, a mass production model of the C1E3 pump had the same hemolysis levels as the BP-80. Our preliminary studies reveal that the C1E3 pump is reliable. Also, the C1E3 will satisfy clinical requirements as a cardiopulmonary bypass pump.

The present study investigates how the surface roughness of an impeller affects hemolysis in the pivot bearing supported Gyro C1E3 pump. This study focuses on particular areas of the impeller surface in the impeller type centrifugal pump. Seven Gyro C1E3 pumps were prepared with smooth surface housings and different impeller parts with different surface roughnesses. The vanes, top side, and backside of the impeller were independently subjected to vapor polishing, fine sand blasting, or coarse sand blasting to produce three different grades of surface roughness. These surfaces were then examined by a surface profile instrument. Using these pumps with different impellers, in vitro hemolysis tests were performed simulating cardiopulmonary bypass (5 L/min, 350 mm Hg). The findings of this study conclusively proved that surface roughness of the back side of the impeller has the greatest effect on hemolysis, followed by the top side and then the vanes. The following are reasons for these findings. First, the shear rate may be greater on the back side than on the top side because of the smaller gap between the back and the housing and the greater relative speed against the impeller. Second, the fluid beneath the impeller may have a longer exposure time because there is little chance for the fluid to mix beneath the impeller. Third, the shear rate may be greater on the top side of the impeller than on the vanes because a vortex formation occurs behind the vanes.

One of the major considerations in the development of a circulatory assist device is its antithrombogenecity. Although the precise evaluation should be accomplished by in vivo tests, these tests are costly and require a relatively long period. In this study, we established a simple in vitro test and assessed feasibility using 2 clinically available centrifugal pumps, the BioMedicus and Nikkiso pumps. Two identical mock loops were fabricated, and fresh heparinized human blood (activated clotting time of 150-250 s) was circulated at 5 L/min against a total pressure head of 100 mm Hg. After 3 h of pumping, only the BioMedicus pumps had thrombi while the Nikkiso pumps were thrombus free. Following 6 h of pumping, thrombi were observed in both pumps. Clotting patterns and locations were reproducible in each pump and similar to the results of clinical or ex vivo studies. This simple in vitro test was considered to be feasible as a pilot study, particularly to predict thrombogenic sites.

The surface roughness of artificial blood contacting devices is an important surface property that is closely related to blood cell trauma. The present study investigated the effect of the surface roughness of a pump housing on hemolysis in an impeller-type centrifugal blood pump, a pivot bearing supported Gyro C1E3 pump. The purpose of the study was to determine which part of a housing has the greatest surface roughness effect on hemolysis in a centrifugal pump. Seven Gyro C1E3 pumps were prepared, each with a smooth surface impeller and a housing with differing areas of altered surface roughness. Both top and bottom housings were divided into half subregions, each with the same area. Seven test pumps were produced by subjecting various subregions of the housings to vapor polishing and sandblasting. The treated surfaces were then examined by a surface profile instrument. Using these 7 pumps with different areas of altered housing roughness, in vitro hemolysis tests were performed simulating cardiopulmonary bypass (5 L/min, 350 mm Hg). The results of this study are as follows. First, the surface roughness of the top housing had a greater effect on hemolysis than that of the bottom housing. Second, on the surface of the top housing, the surface roughness of the outer half area had a greater effect on hemolysis than that of the inner half area. Third, on the surface of the bottom housing, the surface roughness of the inner half area had a greater effect on hemolysis than that of the outer half area. These findings concur with previous studies of now patterns in pumps. Thus, it is expected that the method in this study, comparative in vitro hemolysis tests of the pumps with surfaces of the same roughness but different locations, can be used to detect the high shear area inside a pump.

To clarify the correlation of vibration and thrombus formation inside a rotary blood pump, 40 preliminary vibration studies were performed on pivot bearing centrifugal pumps. No such studies were found in the literature. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, ENDEVCO, San Juan Capistrano, CA, U.S.A.), digitizing oscilloscope (TDS 420, Tektronix Inc., Pittsfield, MA, U.S.A.), and pivot bearing centrifugal pumps. The pump impeller was coupled magnetically to the driver magnet. The accelerometer was mounted on the top of the pump casing to sense radial and axial accelerations. To simulate the 3 common areas of thrombus formation, a piece of silicone rubber was attached to each of the following 3 locations as described: a circular shape on the center bottom of the impeller (CI), an eccentric shape on the bottom of the impeller (EI), and a circular shape on the center bottom casing (CC). A fast Fourier transform (FFT) method at 5 L/min against 100 mm Hg, with a pump rotating speed of 1,600 rpm was used. The frequency response of the vibration sensors used spans of 40 Hz to 2 kHz. The frequency domain was already integrated into the oscilloscope, allowing for comparison of the vibration results. The area of frequency domain at a radial direction was 206 +/- 12.7 mVHz in CI, 239.5 +/- 12.1 mVHz in EI, 365 +/- 12.9 mVHz in CC, and 163 +/- 7.9 mVHz in the control (control vs. CI p = 0.07, control vs. EI p < 0.001, control vs. CC p < 0.001, EI vs. CC p < 0.001, CI vs. CC p < 0.001). Three types of imitation thrombus formations were roughly distinguishable. These results suggested the possibility of detecting thrombus formation using vibration signals, and these studies revealed the usefulness of vibration monitoring to detect thrombus formation in a centrifugal pump.

A pivot bearing-supported centrifugal blood pump has been developed it is a compact, cost effective, and anti-thrombogenic pump with anatomical compatibility. A preliminary evaluation of five paracorporeal left ventricular assist studies were performed on pre-conditioned bovine (70-100 kg), without cardiopulmonary bypass and aortic cross-clamping. The inflow cannula was inserted into the left ventricle (LV) through the apex and the outflow cannula affixed with a Dacron vascular graft was anastomosed to the descending aorta, All pumps demonstrated trouble free performance over a two-week screening period. Among these five studies; three implantations were subjected for one month system validation studies. All the devices were trouble free for longer than ir month. (35, 34, and 31 days). After achieving one month studies, all experiments were terminated There was no evidence of device induced thrombus formation inside the pump. The plasma free hemoglobin levels were within normal ranges throughout all experiments. As a consequence of these studies a mass production model C1E3 of this pump was fabricated as a short-term assist pump This pump has a Normalized Index of Hemolysis of 0.0007 mg/100L and the estimated wear life of the impeller bearings is longer than 8 years. The C1E3 will meet the clinical requirements as a cardiopulmonary bypass pump. For the next step, a miniaturized pivot bearing centrifugal blood pump Pl-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the Pl-601 converts this pivot bearing centrifugal pump as a totally implantable centrifugal pump. A pivot bearing centrifugal pump will become an ideal assist pump for the patients with failing heart.

An eccentric inlet port is a unique feature of the pivot bearing supported Gyro Compact-1 Eccentric Inlet Port Model 3 (C1E3) centrifugal pump, a completely sealless centrifugal pump. The latest C1E3 has an eccentric inlet port with a 30 degree vertical angle. To investigate the adequacy of this 30 degree angle, flow visualization studies and in vitro hemolysis tests were performed, comparing 4 pumps, each with a different angle of the eccentric inlet port (0, 30, 60, and 90 degrees). The flow visualization study utilizing a tracer method focused on the flow pattern just distal to the inlet port of each pump, and each pump was operated at 5 L/min against 100 mm Hg and 5 L/min against 350 mm Hg. In the pumps with angles of 90 and 60 degrees, the flow direction changed horizontally, causing a vortex formation. In the pump with the 30 degree angle, the inflow did not change its course, resulting in minimal space for vortex formation. In the pump with the 0 degree angle, the inflow collided with the pump housing, resulting in a small vortex formation along the housing surface. The in vitro hemolysis tests at 5 L/min against 350 mm Hg revealed that the pump with the 30 degree angle was the least hemolytic and the pump with the 90 degree angle was the most hemolytic among the 4 pumps. These results suggest that the angle of the eccentric inlet port of the Gyro C1E3 pump should be 30 degrees to have less vortex formation and less red blood cell trauma.

A double pivot bearing system is adopted for the Gyro C1E3 centrifugal blood pump to achieve a completely sealless structure that prevents blood leakage and thrombus formation around the shaft. The double pivot bearing system is also a critical factor for blood trauma and durability of the C1E3 pump. This study focuses on the double pivot bearing material. The pump with the male ceramic and female polyethylene pivots (PE) was compared with the pump with the male ceramic and female ceramic pivots (CRM), pertaining to stability of the impeller spinning motion, hemolysis, and durability. At first, the wear rate of the pivots was recorded after operating the pumps in various rotational speeds. As for hemolysis, in vitro tests were carried out using fresh bovine blood in 2 conditions (5 L/min, 350 mm Hg and 5 L/min, 100 mm Hg). Then, stability of the spinning motion was investigated by evaluating the vibration of the pump. The two pumps with different female pivots were operated identically at 2,700 rpm, and the vibration signals were measured using an accelerometer that was mounted on the top of the pump housing. The following findings were obtained in this study. The wear sites were different between the PE and CRM. Most of the wear occurred at the top female poly ethylene pivot in the PE. In contrast, most of the wear occurred at the top male ceramic pivot in the CRM. In addition, the amount of the initial wear was less and the wear rate was lower in the PE than in the CRM. The hemolysis caused by the PE was less than the hemolysis caused by the CRM. The vibration signals of the PE had less amplitude and a narrower range of frequency than the vibration signals of the CRM. In conclusion, the combination of materials male ceramic-female polyethylene are superior to the male ceramic-female ceramic for the double pivot bearing system of the Gyro C1E3 centrifugal pump because of less vibration, less hemolysis, and less wear.

Mechanical trauma of white blood cells (WBC) due to the operation of a rotary blood pump was examined, using a simple method of trypan blue dye exclusion test for a cell viability measurement. The degree of WBC trauma was investigated using a roller pump (RP) and 3 commercially available centrifugal pumps (Bio-Medicus [BP], Capiox [CP], Nikkiso [NK]), and compared with the red blood cell (RBC) trauma. Each pump was operated 3 times at a flow rate of 5 L/min against the total pressure head of 350 mm Hg for 6 h in a mock circuit viith 400 ml of fresh bovine blood. Blood was sampled at 2 h intervals measuring plasma free hemoglobin concentration and the percentage of damaged WBC in the trypan blue dye exclusion test. Each pump demonstrated a linear increase in the degree of WBC trauma, and there were differences among the tested pumps (RP > BP > CP > NK). These findings were similar to those of the free hemoglobin measurements. To compare the degree of RBC and WBC trauma, the probability (gamma,omega) of RBC and WBC to be damaged was calculated, respectively. gamma = Delta D-RBC/Delta N, omega = Delta D-WBC/Delta N where D-RBC and D-WBC are the ratios of the damaged RBC and WBC, respectively, and N is the passing number defined as Qt/V (Q, flow rate; t, time; V, circulating volume). The data of this study demonstrated that the omega value was approximately 20 times or more greater than the gamma equally in all the tested pumps. This suggests that a WBC is more vulnerable to mechanical damage by a rotary blood pump than a RBC.

A compact eccentric inlet port centrifugal blood pump (C1E3) has been perfected for a long-term centrifugal ventricular assist device as well as a cardiopulmonary bypass pump. The C1E3 pump incorporates a sealless design and a blood stagnation free structure. The pump's impeller is magnetically coupled to the driver magnet in a sealless manner. The latest hemolysis study reveals that hemolysis is affected by the magnetic coupling distance between the driver and impeller magnet. Furthermore, a floating phenomenon can be observed in a pivot bearing supported pump. Attention was focused on the relationship between the floating phenomenon's characteristics and the magnetic coupling design in the C1E3 pump. Studies were conducted to evaluate the hydromechanical performance in the floating phenomenon. In this study, the relationship between the magnetic coupling design and the floating phenomenon was verified with a smooth spinning condition. The optimized magnetic coupling distance for the floating mode was estimated to be 12 mm for left ventricular assist device and 9 mm for cardiopulmonary bypass pump. Obtaining an optimal spinning condition is required for regulating the magnetic coupling force. To develop a double pivot bearing pump, it is necessary to establish an optimal spinning and/or floating condition and to determine the proper magnetic coupling and magnetic force between the impeller and driver.

The Kyocera Gyro pump has been developed as a completely seal-less centrifugal pump to overcome the problems of the conventional centrifugal pumps. The Gyro pump is a double pivot bearing-supported centrifugal pump with several specific design features, including its eccentric inlet port. We investigated the feasibility of the Gyro pump for cardiopulmonary bypass (CPB) in a bovine model, comparing it with the BioMedicus pump (BP-80). Ten healthy calves (5: Gyro pump, 5: BP-80) underwent 6 h of mildly hypothermic CPB at approximately 33°C. Both pumps provided more than 50 ml/kg/min without any incidents. The haemodynamics of both groups remained stable within the normal range. All haematology and biochemistry data demonstrated no significant differences between the two groups. However, values of plasma-free haemoglobin and lactate dehydrogenase were less throughout the experiments of the Gyro pump than those of the BP-80. To obtain flow equivalent to that of the BP-80, the Gyro pump needed less rotational speeds than the BP-80 (2749.7 ± 233.3 versus 3170.6 ± 300.8 rpm, p &lt 0.05). Less rotational speed in addition to the difference in operating principle may contribute to less blood damage during the CPB of the Gyro pump. After pumping for CPB, no leakage or thrombus formation was observed in either pump. The present study indicated that the Kyocera Gyro pump can be applied as a centrifugal pump for CPB with the same performance as the BP-80 and with relatively less haemolysis than the BP-80.

As the clinical application of LVADs has increased, attempts have been made to develop smaller, less expensive, more durable and efficient implantable devices using rotary blood pumps. Since chronic circulatory support with implantable continuous-flow LVADs will be established in the near future, we need to determine the flow characteristics through an implantable continuous-flow LVAD. This study describes the flow characteristics through an implantable centrifugal blood pump as a left ventricular assist device (LVAD) to obtain a simple non-invasive algorithm to control its assist flow rate adequately. A prototype of the completely seal-less and pivot bearing-supported centrifugal blood pump was implanted into two calves, bypassing from the left ventricle to the descending aorta. Device motor speed, voltage, current, flow rate, and aortic blood pressure were monitored continuously. The how patterns revealed forward how in ventricular systole and backward flow in diastole. As the pump speed increased, an end-diastolic notch became evident in the flow profile. Although the flow rate (Q [l/min]) and rotational speed (R [rpm]) had a linear correlation (Q = 0.0042R - 5.159; r = 0.96), this linearity was altered after the end-diastolic notch was evident. The end-diastolic notch is considered to be a sign of the sucking phenomenon of the centrifugal pump. Also, although the consumed current (I [A]) and how rate had a linear correlation (I = 0.212Q + 0.29; r = 0.97), this linearity also changed after the end-diastolic notch was evident. Based upon the above findings, we propose a simple algorithm to maintain submaximal flow without inducing sucking. To maintain the submaximal flow rate without measuring flow rate, the sucking point is determined by monitoring consumed current according to gradual increases in voltage.

The blood contacting surface quality is an important pump parameter for blood compatibility and cell damage. This study investigates the surface roughness and the effect it has on hemolysis in a centrifugal blood pump. In vitro hemolysis tests were performed with a pivot bearing supported Gyro centrifugal pump (C1E3) simulating cardiopulmonary bypass (CPB; 5 L/min, 350 mm Hg) and left ventricular assist device (LVAD; 5 L/min, 100 mm Hg) conditions. To produce 4 different grades of surface roughness, the impellers and housings were subjected to vapor polishing, sand papering, fine sand blasting, or coarse sand blasting. Seven pumps were assembled with different impeller and housing surfaces. These surfaces were then examined by a surface profile instrument and a scanning electron microscope. The results of this study are as follows. First, the effect of surface roughness on hemolysis was significantly greater in the CPB condition than in the LVAD condition, Second, surface roughness, regardless of whether it is the impeller or pump housing, had little effect on hemolysis in the LVAD condition. Third, in the CPB condition, the surface roughness of the pump housing has a greater effect on hemolysis than does that of the impeller, From a hemolytic point of view, an extremely smooth pump housing is required for use of an impeller type centrifugal pump as a CPB device. In contrast, it is conceivable that a smooth surface is not always essential for an impeller type centrifugal pump that is used as an LVAD.

Centrifugal blood pumps are playing a key role in circulatory mechanical assist systems including cardiopulmonary bypass (CPB), right and left ventricular assist devices (RVAD and LVAD), percutaneous cardiopulmonary support (PCPS) and extracorporeal membrane oxygenation (ECMO). Each of these circulatory assist systems requires specific flow and pressure conditions, In vitro hemolysis tests were performed using five compact mock loops with flow and pressure set equivalent to clinical conditions. These studies determined the hemolytic characteristics and clinical applicability of the pivot bearing-supported Gyro centrifugal pump with an eccentric port (C1E3) compared with the Bio-Medicus pump (BP-80). Normalized index of hemolysis (NIH) values of the C1E3 were less than those of the BP-80 under all conditions in particular, they were significantly Less in the CPB, LVAD, and RVAD conditions. In addition, linear correlation was observed between NIH values, rotational pump speed (RPM), total pressure head (Delta P), and flow rate (Q) with both the C1E3 and BP-80: NIH = a(RPM/Q) + b, NIH = c(Delta P/Q) + d. However, the slopes (a and c) of these equations were smaller with the C1E3 than those with the BP-80, which suggests that the C1E3 has decreased hemolytic characteristics when increasing the RPM and Delta P. In other words, the increase of RPM and Delta P results in less shear stress with the C1E3 than with the BP-80. One cause of these decreased hemolytic characteristics of the C1E3 is thought to be less pump power loss against an increase of RPM and Delta P than with the BP-80. Furthermore, the average exposure time is shorter with the C1E3 than with the BP-80 because the priming volume of the C1E3 (30 ml) is smaller than that of the BP-80 (80 ml). From the point of both shear stress and exposure time, the C1E3 has less hemolytic features than the BP-80.

The pivot bearing-supported Gyro C1E3 centrifugal pump is driven by magnetic coupling. The magnetic coupling distance (MCD) between the impeller magnet and the driver magnet affects both hydraulic performance and hemolysis. Although a greater MCD causes less hemolysis, it increases the risk of decoupling of the impeller magnet. Therefore, it is important to consider the effect of the MCD on both hemolysis and decoupling when the C1E3 pump is applied in various circulatory assist conditions. This study investigates the effect of the MCD on decoupling in a C1E3 pump that is driven by the Nd-Fe-B composite ring-shaped magnets. The results will determine which MCD is the most practical in all assist device conditions, The MCD of the C1E3 pump was varied from 9.5 to 14.5 mm by inserting spacers between the bottom pump housing and the driver magnet. At a rotational speed just before the decoupling occurred, the flow rate and total pressure head were measured. The results revealed that a MCD between 9.5 and 14.5 mm was enough to produce a flow rate of more than 10 L/min without decoupling, and a MCD of less than 11.5 mm was required when the total pressure head was more than 500 mm Hg. Thus, the limiting factor for the MCD of the C1E3 pump is the total pressure head rather than the flow rate. An MCD of less than 11.5 mm is required to prevent decoupling of the impeller of the C1E3 pump with the specific Nd-Fe-B magnets in the full range of clinical circulatory assist conditions.

Pump power loss is defined as input power that is not used for the output work of the pump. Less pump power loss means a higher pump efficiency, A common opinion is that the pump power loss is closely related to heal generation of the pump, which may affect not only the endurance of pump materials, but also blood damage in a blood pump, In this study, the relationship between pump power loss and heat generation in centrifugal blood pumps was investigated using the pivot-bearing supported Gyro C1E3 pump (C1E3) and Bio-Medicus pump (BP-SO) under four different total pressure head/flow conditions, A single special torque measuring driver motor was used for operating both the C1E3 and BP-SO in the four conditions, The pump power loss was calculated from the measured motor torque and hydraulic power. The changes in blood temperature were measured while the pump was operated at room temperature (25 degrees C) to obtain the following findings: First, the C1E3 caused less pump power loss and less temperature increase in blood than the BP-80 in all clinical simulated conditions that were tested; and second, the pump power loss and heat generation had a linear correlation with temperature rise from 22 to 25 degrees C in both the C1E3 and BP-80. During this period, approximately 30% of the pump power loss was transformed to heat, independent of the centrifugal blood pump type. provided that heat conduction through the pump housing and tubing was negligible during this particular period.

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 pump was estimated for various pumping conditions. The lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

The pivot bearing centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. This pivot bearing supported centrifugal pump with an eccentric port (C1E) incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 12 L/min against 650 mm Hg total pressure head at 3,600 rpm, and in a CPB condition 5 L/min against 350 mm Hg total pressure head at 2,600 rpm. Very recently, the pivot bearing system was modified to obtain a stable and smooth spinning movement. The material of the female pivot was changed from ceramic to polyethylene. Three kinds of bearings were tested simultaneously with bovine blood in two types of in vitro circuits to determine the blood damage from the bearings. Pressure differences across the pump (total head pressure, Delta P) of 140 mm Hg (n = 12) and 330 mm Hg (n = 12) were examined. The normalized index of hemolysis (NIH) was slightly higher in a ball bearing (BB) pump than in a polyethylene bearing (PB) pump and statistically higher than the BioMedicus Pump (BP-80) on Delta P of 140 mm Hg. When the Delta P was at 330 mm Hg, a comparison between the three types of pumps revealed no difference in NIH. In addition, the primary vane of the impeller was redesigned to obtain an atraumatic structure. In the second study (n = 14), there was no difference in the NIH between BP-80 and the current model when the Delta P was 300 mm Hg (0.019 +/- 0.002 vs. 0.027 +/- 0.006, p = 0.3) and/or when the Delta P was 100 mm Hg (0.0008 +/- 0.0001 vs. 0.0014 +/- 0.0002, p = 0.07). The modified pivot bearing had an improved spinning condition and no change in hemolysis. A proper selection of pivot bearing materials is important to develop an atraumatic centrifugal pump. The modification of the bearing system and redesign of the vane enabled a compact centrifugal pump to become a reality.

Blood trauma is one of the important performance parameters of centrifugal pumps. To investigate the blood trauma induced by these pumps, in vitro hemolysis tests have become an important procedure and are increasingly used for pump development and comparisons. The Baylor compact eccentric inlet port (C1E) centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump (CPB). The Baylor C1E pump incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 5 L/min against 350 mm Hg of total pressure head at 2,600 revolutions per minute. The pump impeller is magnetically coupled to the driver magnet in a seal-less manner. The latest hemolysis study revealed that hemolysis may be affected by the gap distance between the driver and the impeller magnet. The purpose of this study was to verify the effect of the magnetic coupling distance on the normalized index of hemolysis (NIH) with the C1E model and to obtain an optimal gap distance. The NIH value was clearly decreased by alteration of the magnetic coupling distance from 7.7 to 9.7 mm in CPB and left ventricular assist device (LVAD) conditions. The NIH, when using the pump as an LVAD condition, was reduced to a level of 0.0056 from 0.095 when the magnetic coupling distance was extended. The same results were also obtained when the pumps were used in a CPB condition. The magnetic coupling distance is an important factor for the C1E model in terms of hemolysis. Different coupling forces effect the bearings and impeller stability, These results suggest that an optimal driving condition with a proper magnetic coupling and an optimal force between the impeller and driver is necessary to develop an atraumatic centrifugal pump.

A double chamber ventricular assist device (VAD) with a roller screw linear muscle actuator (RSLMA) driven by the left and right latissimus dorsi muscles was developed. The inflow port of each chamber was connected to form the compound inflow port, and the outflow ports were connected to form the compound outflow port. The advantages of this system include 1) the contraction of each muscle contributes to ejection from each ventricle into the common outflow port, thus doubling the net outflow; 2) through proper adjustment of muscle length, the preload to each muscle can he optimized to yield the maximum muscle force; 3) muscle can be stimulated at a lower rate to reduce fatigue and to optimize muscle performance; and 4) the compliance cham her needed in the implantable VAD system is not required with this system. In vitro evaluation in the mock loop with the human arm actuating the RSLMA revealed that the double chamber VAD can provide pump flows of 2-4 L/min against an afterload of 100 mmHg at a stimulation rate of 35-50 beats per minute. The power requirement for each muscle ranged from 2.5 to 3 W at a muscle stroke length of 4 cm. These results verify that the double chamber VAD with the RSLMA driven by the left and right latissimus dorsi muscles can meet the design requirements of a muscle driven VAD to assist the left heart.

冠動脈疾患の心機能評価では,収縮機能のみならず,拡張機能も対象としなければならない.今回我々は,CABGの前後で左室拡張機能がいかに変化するかを,CABG施行症例25例(男25例・女5例)にドップラー心エコー法を施行し,検討した.<BR>左室流入波形から,左室拡張機能の指標として1)E:拡張早期ピーク速度,2)A:心房収縮ピーク速度,3)E/A,4)Earea:拡張早期の時間流速積分値,5)A area:心房収縮期の時間流速積分値,6)E/Aarea:4)と5)の比,7)1/3TVI:時間流速積分値の1/3,8)IVRT:等容性弛緩時間,9)AT:収縮早期の加速時間,10)DT:収縮早期の減速時間,11)DR:減速率,12)NPFR:normalized peak fillingrateを用いた.また,対象を術後造影で中隔枝がバイパスグラフトから灌流される群(G群)と,左冠動脈から灌流される群(N群)とに分け,心エコーのデータを比較した.<BR>E,E/A,E area,E/A areaは術後有意に増加し,A,A areaは術後有意に減少し,IVRTは,有意差はないものの,術後正常範囲に入り,減少する傾向にあった.術前後の変化率で比較すると,G群の方がN群より有意に改善していた.<BR>虚血により障害されていたhibernating myocardiumの左室拡張機能は,CABGにより改善するといえる.またCABGによる左室拡張機能の改善の本質は,心臓の中で最も血流を要し,右室・左室の機能上重要な役割を果たす心室中隔の血行の改善であると考えられた.

名古屋掖済会病院において1987年から1991年の4年間で84例に対しMedtronic-Hall弁を用い弁置換手術を行った。大動脈弁置換(AVR)29例、僧帽弁置換(MVR)40例、大動脈弁、僧帽弁置換(DVR)14例、肺動脈弁置換1例で平均年齢53才であった。手術死亡(病院死亡)は4例、AVR3例(10%)、DVR1例(7%)で83例(98.8%)の患者が追跡可能で平均追跡期間は33ヶ月であった。実測生存率は4年でAVR;76±10%、MVR;70±14%、DVR;93±7%、血栓塞栓症非発生率は4年でAVR;92±5%、MVR;95±4%、DVR;100%であった。弁関連死非発生率は4年でAVR、DVRともに100%、MVR;82±13%であった。<br>僧帽弁位で3例のclosed stuck valveを経験したが、手技の改善により解決した。<br>溶血は少なく、約1/3の症例でハプトグロビンは正常域にあった。Medtronic-Hall弁による弁置換術の臨床成績は良好であった。

大動脈弁置換術後65症例に連続波およびパルスドップラー心エコー法を施行し、大動脈弁位人工弁の評価法としての連続の式を用いた指標:有効弁口面積(EOA), Doppler velocity index(DVI=V 1max/V 2max), 大動脈弁狭窄率(aortic stenotic ratio(ASR)=EOA/LVOTA=V1 flow integral/V2 flow integral)の有用性について、Bernoulliの式を用いた圧較差(maxPG)と比較し検討した。(1) maxPG, EOAは、弁のサイズに強く影響され、DVI, ASRは、弁のサイズと無関係であった。(2) EOA, DVI, ASRは、maxPGと有意に負の相関を示した。(3) 種々の理由で人工弁を通過する血流量が少ないために、lnaxPGが低く算出され、連続の式の指標との間で不一致を示す例で、人工弁の開放角の低下が示された。(4) 人工弁の機能異常を示唆する指標として、DVI<0.25, ASR<0.27が得られた。以上より大動脈弁位人工弁の機能評価には、影響因子が多いInaxPGよりも、連続の式を用いたDVI, ASRが簡便かつ有用と考えられた。

肝臓の動静脈奇形 (AVM) はまれな疾患であり主に遺伝性出血性毛細血管拡張症に合併し, 国内では画像診断に関する報告を散見するのみである. 症例は69歳女性, 心不全を主訴に来院し肝の両葉に多発したAVMによる高拍出性心不全と診断された. 診断にはドップラー法を含めたエコー検査と血管造影, 心臓カテーテル検査が有効であった. 金属コイルによる肝動脈塞栓術を二回に分けて施行し心不全症状の改善をみた. 塞栓療法の方法につき検討し報告する.

Abstract The maze procedure may be performed in combination with valve operations to treat chronic atrial fibrillation associated with valve dysfunction. Although we initially used the modified Cox maze III procedure, a more limited partial maze procedure is now preferred because the left atrium might be considered as the electrical impetues for atrial fibrillation. In this study we compared the results of 30 patients (group I) who underwent the full biatrial modified Cox maze III and 20 (group II) patients the partial maze procedure. While the rates of restored sinus rhythm were the same in both groups at 6‐month follow‐up (I: 83.3%, vs II: 80%), the following advantages were noted in the patients undergoing the partial maze procedure: shorter operative times, lesser elevations of creatine phosphokinase, lower rate of blood transfusion, lower rate of junc‐tional rhythm soon after the operation, and a higher P wave in those patients with restored sinus rhythm. The effectiveness of the partial maze procedure seems equal to that of the biatrial modified Cox maze III procedure for atrial fibrillation associated with valve disease. The partial maze procedure is simple and less invasive, and thus might be applied more frequently as an additional procedure to valve operations without additional risk. Copyright © 1985, Wiley Blackwell. All rights reserved