For quick and safe introduction of left atrial (LA) cannula for left heart bypass(AAB) using transseptal puncture technique, weexamined effectiveness of transesophageal echocardiography (TEE) guidance. Transseptal puncturewas performed on 24 patients (age=48.6±10.9, 8 males and 16 females) during percutaneous-transseptal mitral commissurotomy by TEE guide. The entire image of Brockenbrough needle tipwas clearly observed by longitudinal image of biplane TEE in all (100%). Transseptal puncture was also performed on 4 dogs (8-13kg) by TEE guide and AAB was performed using LA cannulaspecially designed for transatrial cannulation. AAB support was also performed on 3 patients with percutaneous introduction of LA cannula utilizing the same technique. 2 patients weresurvived with effective support of single AAB (63 year-old, male) or combined support of AAB and veno-arterial bypass (43 year-old, male). In conclusion, transseptal LA cannulation can be performed easily by TEE guide. Thus, percutaneous left heart bypass can be set-up veryquickly and safely even in the intensive care unit without X-ray equipment.

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A new left ventricular (LV) assist device, Integrated Cardioassist Catheter (ICAC) has been developed for pulsatile left ventricular flow support. This device is made up of a transaortic valve LV draining tube and a concomitant intraaortic balloon as a single apparatus. The draining tube is inserted from the femoral artery percutaneously into the LV via the aortic valve, and the blood is returned by another cannula inserted percutaneously from the opposite side femoral artery. Pulsatile flow could be added to LV bypass by means of a synchronously operated balloon in the descending aorta.
As for an instanteneous insertion of this ICAC, a pig-tail catheter with an internal guide wire is first passed through the lumen of the draining tube into the LV. When the pig-tail catheter is confirmed to be in an ideal position with portable fluoroscopy, the tube is advanced. As soon as the tip of the ICAC is inserted into the LV, it is connected to a centrifugal pump and IABP console. It took only 3-4 minutes to insert and then drive, after the arteries are exposed in canine experiment. Application of pig-tail catheter made insertion easier without any complications.
With this method, the device can be applied by percutaneous insertion emergently for patients with severe LV dysfunction in the ICU, the CCU or the operating room.

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Usefulness of electromyography (EMG) to monitor fatigue of latissimus dorsi muscle (LDM) for cardiomyoplasty was investigated in an animal study. After Cardiomyoplasty, the monitoring of LDM fatigue independently from myocardium is necessary to control conditions of LDM pacemaker. Graded fatigue of canine LDM after vascular delay without electrical preconditioning were obtained by frequency change of electrical stimulation for ten minute driving. During electrical stimulation EMG was recorded with intramuscular platinum electrodes and studied by a signal processor. Patterns and parameters of EMG were significantly different, depending on graded fatigue of LDM.

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The present study addressed the optimal application of the MCAD. Using the canine unconditioned and minimally dissected latissimus dorsi muscle, MCAD (full stroke: 60ml) was assembled with driving dome for counterpulsation (CP) or driving chamber for ventricular bypass (VB) and set up in the mock circuit. At systemic afterload, MCAD functioned as CP with 60mmHg preload, resulted in maximum stroke work of 4.4×10⁶ erg, however did not as left side VB. On the other hand, at pulmonary afterload, the greater stroke work of 1.3×10⁶ erg than that of canine right ventricle was obtained using bellows chamber. The key issues for augmentation of MCAD performance are a sufficient muscle stretch during pump diastole, good filling sensitivity and efficient power transmission from muscle to the pump diaphragm. In conclusion, CP and right ventricular support are optimal for MCAD application, while left ventricular support is marginal. To circumvent the disadvantage, active filling assist mechanism and booster ejection pump will be necessary.

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Chronic phase problems cardiomyoplasty were examined using 7 canine models. We have transferred a latissimus dorsi muscle flap to the heart through the second intercostal space and subsequently wrapped around both ventricles in a counterclockwise manner. After 2-4 months electrical conditioning, change of hemodynamics with latissimus dorsi stimulation were examined in varying muscle stimulation parameters. As a stimulating generator we used ambulatory extracorporeal burst-pulse generator (Juntendo type, model MC 4102) which we have developed. Ventricular pressure increasing was more significant at right ventricle which has thinner wall. However, for left ventricular assist, we should increase higher voltage stimulation, which goes beyond physiologically normal range. Moreover, impedance between stimulating leads steadily increased. It is suggested that special modification in pacing wire leads is needed.

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Left heart bypass and arterial bypass using a centrifugal pump were performed as an auxiliary technique for treatment of disease of the thoracic aorta in 34 cases, and hemodynamic differences during aortic clamping were compared. Peripheral blood pressure, urinary output and bypass flow during aortic clamping showed no significant difference between left heart bypass and arterial bypass, But it seemed that arterial bypass was easier to support stable hemodyanmic status than left heart bypass. However, the indications of arterial bypass are ristricted by modality or region of the lesion in thoracic aorta. Left heart bypass is usually not affected by modality or region of lesion in thoracic aorta. But it is not easy to approach to the left atrium in cases of severe left ventricular hypertrophy, and we experienced two cases with complications of pericardial effusion related to the bypass technique. It is necessary to select, arterial bypass or left heart bypass, based on as understanding the merits of each bypass technique, and also for provide careful management to prevent complications related to the bypass technique.

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Between November 1987 and July 1991, 12 cases of descending thoracic or tioraco-abdominal aortic aneurysm were operated with the aid of temporary left heart bypass. Left heart bypass was performed using a centrifugal pump with minimal heparinization. There were 2 hospital deaths (17%) due to renal failure and multiple organ failure in the cases of rupture of aneurysm. Since cerebral embolism occurred in a case of distal arch aneurysm during aortic cross-clamping between the left carotid and left subclavian artery, left heart bypass seems to have a limitation for graft replacement of distal arch aneurysm. When optimal bypass flow was maintained during aortic cross-clamping, serum ketone body ratio and serum bilirubin showed normal values after operation. Postoperative renal function was influenced by clamping of renal artery during operation. Although it was difficult to save a case of aneurysmal rupture, centrifugal pump was useful for graft replacement of the descending thoracic or thoraco-abdominal aneurysm.

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Left heart bypass with the Bio Medicus centrifugal pump was used to treat 14 patients with aneurysms confined to the segment of the descending thoracic aorta. The study included 14 patients ranged 44 to 76 years of ages. The lesion was replaced by a woven Dacron tube in 9 patients, by a woven Dacron tube with Ivaron sponge occulusionmethod in 3, by a woven Dacron patch in 2. Minimal systemic heparinization was used just before aortic cross-clamping. Activated clotting times were maintained on an average of 241.9 s. During repair, the proximal and distal aortic pressures were monitored, and was maintained the systemic pressures at over 100mmHg in the upper extremities and 60mmHg in the lower extremities. The pump flow was adjusted accordingly between 1.65 and 2.68L/min. Urine volume was kept at 5.98ml/min during clamping. An intraoperative autotransfusion system for blood conservation was used in all patients to return the shed blood. Average intraoperative blood loss was 1073ml. The average intraoperative autotransfusion volume was 2191ml. Three patients were treated without blood transfusion. No deaths occurred in this series. One patient developed paraplegia and one renal failure, but both were cured. We believe that the BioMedicus centrifugal pump is a simple and safe method for perfusion of the lower body during surgery on the descending thoracic aorta.

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In our institute, we had the 215 clinical cases that were supported by two types of assisted circulation, (IABP: 199, VAD: 16), after severe cardiac operation. Post-operative courses and the complication were examined, in detail, and post-operative management for these cases was studied. The prognosis in early application cases of assist device was better than that in late application cases. The dead cases that had been complicated multiple organ failure (MOF) were suffered from low cardiac out-put, and had the tendency of the right ventricular failure. In addition, MOF cases had the deterioration of major organ failure, even in during support. Opportunistic infection of VAD cases occured after the removal of VAD. These results suggest that, in order to get the long survival of assisted circulation cases, early application, prevent MOF, and the management for infection are necessary.

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The effects of three different driving modes of LVAD for peripheral circulation were studied. Peripheral circulation, especially renal and hepatic blood flow distribution was evaluated in each driving mode (diastolic driving, systolic driving mode, fixed rate driving mode) during left ventricular assist. Proper hepatic and renal arterial flow and regional blood flow were measured 2 hours after LVAD was started. The results showed that significant change of hepatic blood flow distribution was not seen in each driving mode. But the imbalance of intrarenal blood flow distribution was recognized under the fixed rate driving mode.

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We designed a new device that incorporated a VAD out let with a membrane oxygenator, and examined the result. In the mock circulation study, a sufficient inlet flow from the membrane oxygenator for oxygenation and removal of carbon dioxide was obtained. Sufficient flow and pressure to maintain systemic circulation were also obtained. In the hypoventilation and heart failure models' study, with this device, hemodynamics were improved and recovered from heart failure. This device was also able to maintain systemic circulation. And the data of blood gas analysis was also improved These results suggest that this new assisted-circulation system is possibly a superior circulation assist method which has circulatory assist effects and respiratory assistance capabilities. Moreover, we suspect that these findings can be put to use in clinical cases that include heart failure associated with respiratory failure.

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Prolonged normothermic global ischemia in the canine model is generally fatal. To determine whether Ca²⁺-ATPase activity in such injured cardiac myocyte is recoverable with biventricular assist support (BVAS), we subjected 15 canines to 45 minutes of global ischemia at normothermia. After ischemia and further 20 minutes of reperfusion (G2), the animals were supported for 3 hours with BVAS (G3). Mean BP, developed pressure and LVmaxdp/dt in G2 significantly reduced compared with control (G1) and those in G3 were significantly recovered after 3 hours with BVAS compared with G2. Kinetics of Ca²⁺-ATPase activity of the failing cardiac myocyte with BVAS was estimated using a lead citrate method. Electromicroscopic findings of Ca²⁺-ATPase activity in G2 showed noactivities in sarcoplasmic reticula (SR) and myofilaments (MF) but showed less activity in mitochondria (MT) compared with G1. At 3 hours with BVAS in G3, Ca²⁺-ATPase activity of MT was recovered but those of SR and MF remained low. In conclusion, our data indicate that BVAS makes a contribution to the recovery of Ca²⁺-ATPase activity of MT in the failing canine heart due to normothermic global ischemia for 45 minutes.

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In order to evaluate the effect of left ventricular assistance on cardiac dysfunction due to the induced stunned myocardium after the reperfusion, acute experiments using adult goats was performed. After the implantation of our TH-7B pneumatically driven VAD as left heart bypass, left anterior discending artery (LAD) was reperfused after short time occulusion to constitute the model of the stunned myocardium. Pressure-Volume curve (P-V curve) and E_max of left ventricle were obtained by our newly developed automatic hemodynamics analysing system to evaluate the recovery time from the transient left ventricular dysfunction. The recovery time were significantly decreased by the use of VAD. These results suggest that VAD is useful also for the transient ischemia to avoid to have heart muscle destroyed.

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From January 1989 to August 1991, 145 cases underwent intra-aortic balloon counterpulsation with a new type balloon catheter (TMP balloon) deviced for Japanese. Statistical analysis on complications was carried out between these cases and 109 cases undergone conventional balloon (Datascope Balloon) placement during the same period. There was a significant difference in frequency of balloon rupture between TMP (0/145; 0%) and Datascope balloon (6/109; 5.5%). Vascular complications were found in 2 cases of TMP balloon, which were loss of distal pulses of inserted leg. However, severe peripheral arteriosclerosis existed in both cases and one had bilateral arteriosclerosis obliterans. Symptomatic abdominal complications including thrombo-embolism of aortic branches were not observed. It would be concluded that the concept of TMP balloon was fed back to the clinical outcome and especially to its safety.

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Hemodynamic and hormonal changes were studied in 11 sheep with electrically fibrillated heart. Their circulation was maintained by the biventricular bypass with pneumatic driven pusher-plate pumps. Periods of survival ranged from 2 to 48 days with average of 11.3 days. Hemodynamic parameters except for central venous pressure (CVP) were kept physiological range, and CVP slightly elevated to 10-13mmHg. Adrenaline did not change significantly. Serum levels of triiodothyronine and thyroxine decreased significantly, and did not return to control level. Atrial natriuretic polypeptides increased significantly 4 days after the mild CVP elevation. In conclusion, biventricular bypass in the animal with ventricular fibrillated heart altered hormonal situation while hemodynamic parameters were maintained within almost normal range.

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The predictor of mean aortic or left atrial pressure (mAoP or mLAP) under LVAD driving was investigated in acute animal experiments. The relationship between mAoP (or mLAP) and mean bypass flow (mBF) was assessed by using a time-series model. Based on these data, the parameters for prediction of mAoP or mLAP for given mBF were determined. The predictor was applied to mongrel dogs with LVAD. Vacuum pressure of LVAD was changed every 30-60 beats, then LVAD was stopped. The changes of mAoP, mLAP and mBF were recorded. Using the data in the period of LVAD-on, mAoP or mLAP in no BF was predicted and these values were compared with the measured values in LVAD-off state. The differences in mLAP were under 1mmHg in most cases. There were a few cases that mAoP followed the change of mBF in the experiments. Prediction of mAoP with these data showed the differences few mmHg. The predictor was feasible for prediction of mLAP and mAoP for given BF. The predicated pressures may be useful information to control LVAD. And the predicted value in no BF can be used as a simple indicator for the weaning of LVAD.

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Feasibility of a ferrofluidic actuator for an artifical heart was studied. A ferrofluidic actuator moves magnetic fluids by applying a magnetic field to magnetic fluids. When magnetic flux of 0.32T was applied to the interface of the ferrofluid and air, the ferrofluid was displaced and a pressure of 7.58kPa (57mmHg) was obtained. An array of four poles of solenoids was mounted near a U-shaped glass cylinder. Two solenoids were alternately activated. A pressure of 8.65kPa (65mmHg) was obtained. Calculations indicate magnetic flux of 0.49T is enough for obtaining a pressure of 13.3kPa (100mmHg). A ferrofluidic actuator is a promising actuator for an implantable artificial heart.

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Our 8 patients' experience with centrifugal pump ventricular assist device (VAD) was analized to determine variables influencing the outcome. Biventricular bypass was performed in 2 patients, and right ventricular bypass in 2, and other 4 received left VAD. Patients were deviled into 2 groups: Group A consisted of 4 patients who were either weaned from VAD (3) or died on VAD from cerebral death (1), Group B consisted of 4 patients who were not waened from VAD. Although the mean pump flow rate was more than 3.0L/min in both groups, mean aortic pressure (m-AoP) was lower in Group B. Group B showed lower SvO₂ and higher level of VO₂I. Blood lactate level and temperature difference between central and peripheral sites were useful to assess the perfusion state. Main complications during ventricular support were bleeding which required reoperation in 5 patients, renal failure with dialysis in 5. From our experience with centrifugal pump VAD, in patients with postoperative profound shock in whom it was difficult to maintain m-AoP≥60mmHg, weaning from VAD was not possible.

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Emergency coronary angiography, emergency reperfusion therapy and intra-aortic balloon pumping improved clinical results of acute myocardial infarction. But patients with sever pump failure need more effective mechanical assist. Percutaneous cardiopulmonary support (PCPS) is an useful alternative procedure in such situation. Two of 5 patients who were resuscitated by PCPS survived after coronary angioplasty. Twenty-five cases of 31 emergency or urgent surgical cases were salvaged but left heart bypass by assist device was necessary in 2 cases. Thirty-seven old man who was suffering from acute occlusion of left main trunk underwent emergency bypass surgery, but he died after 3 months from heart failure and infection in spite of being weaned from left heart assist after 10 days from its application. This patient was considered to be a candidate for heart transplantation.

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Sixteen patients received circulatory support using centrifugal pump for the purpose of either left ventricular assist(6 cases), or veno-arterial bypass ( VAB, 10 cases). Out of six LV-assisted patients, two could be weaned but only one was the long survivor. Out of ten VAB assisted patients, four could be weaned and two were the long survivors. Percutaneous approach of VAB had the advantage to minimise bleeding from the cannulation sites. Although, circulatory assist using the centrifugal pump has some disadvantages in durability and antithrombogenesity, it seems to be useful for circulatory assist in patients with right ventricular failure who requires a relatively short term mechanical support.

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To evaluate the function of left ventricular assist device (LVAD) hemodynamically, seven patients were devided into three groups according to the assisted period and clinical course. Three patients were weaned from the LVAD within 48 hours (early recovered group: R), two were assisted for 74 to 127 hours (intermediate group: M) and two were assisted for 252 to 329 hours (delayed group: S). R group showed significant higher total cardiac output (more than 3 l/min/ m²) and lower pulmonary wedge pressure and right atrial pressure (less than 10 mmHg) than the other two groups. Mean assist flow by LVAD was 2.47±0.3 l/min during 48 hours in 4 cases with the Sac type LVAD and this value was not changed by driving condition, both atrial pressures and native cardiac output. To prevent multiple organ failure after application of LVAD, it is necessary to maintain the sufficient total cardiac output (more than 3 l/min/ m²) and assist flow (more than 4 l/min).

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Emergency bridge to heart transplantation was applied for four patients with acute irreversible cardiac failure at Stanford University. All patients had cardiogenic shock and/or fatal ventricular arrhythmia refractory to intensive medical therapy and intraaortic balloon pumping. Bridge duration of the Novacor LVAS was 26-62(mean 41.3) days. Coagulopathy, infection of LVAD pocket, leg ischemia and multiple organ insufficiency occurred as complications of mechanical circulatory support. These four patients were successfully bridged to cardiac transplantation. All patients were discharged three or four weeks after transplantation and doing well in the postoperative 2-27 months. We conclude that emergency bridge to heart transplantation can be a surgical treatment of choice for acute irreversible cardiac failure.

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We have built a new compact control drive unit (CDU) which can be used for a ventricular assist system (VAS) or intraaortic balloon pumping (IABP). This CDU has an installed air compressor, a vacuum unit, a battery, full alarm and backup systems, an automatic level control of flow and atrial pressure for VAS, and a full-fill to full-empty drive mode controlled by air flow. This CDU exhibited satisfactory and stable performance in mock circulation, animal studies and clinical cases. This new compact CDU is thought to be useful in clinical setting.

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As a centrifugal pump was widely used for eltracorporeal circulation in recent years, the clarification of the influences of nonpulsatile blood flow on physiological function has become more important, especially in pulmonary function. To analyze the influences, nonpulsatile pulmonary blood flow by a centrifugal pump was established in chronic animal models. A pulsatile RVAS was implanted to draw the blood from both the right atrium and ventricle and to send to the pulmonary artery in 4 goats. Two weeks after implanted, the pulsatile pump was quickly replaced by a centrifugal pump without anesthesia and a 100% nonpulsatile pulmonary blood flow was obtained. Cardiac output was kept at 80-120 ml/kg/min during the experiments and no changes were observed in hemodynamic parameters after the immediate depulsation of the pulmonary flow. Blood gas data and serum levels of angiotensin converting enzyme were maintained within normal range. There was no significant change in the ventral to dorsal blood perfusion ratio of the lower lobe of right lung which was calculated by the colored microsphere method, between pulsatile and nonpulsatile pulmonary flow. These results suggested that pulmonary functions including gas exchange and metabolism of vasoactive agent and lung tissue perfusion were not affected by nonpulsatile pulmonary circulation.

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A viblating electro-magnetic pump (VEMP), which generates viblating flow at the frequency of 3-50Hz, was utilized to analyse the effect of each frequency element composing the pulsatile flow and pressure patterans on the peripheral blood flow distribution in the condition of hypoperfusion. In 7 adult goats in which a VEMP was applied as a total left heart bypass, carotid artery flow (CAF), subclavian artery flow and total peripheral resistance were changed according to the drive frequency of the VEMP. CAF showed a significant increase at the drive frequency of 7 and 15Hz compared with conventional artificial heart driving at the rate of 120 b. p. m. These results suggest that each frequency component of blood flow affects the peripheral blood flow distribution in the condition of hypoperfusion.

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A continuous, real-time monitoring method for the cardiac output during assistance with left ventricular assist device (LVAD) was developed based on time series analysis. During ejection of LVAD, parametric model for arterial load was identified by least square algorithm. Natural heart flow was estimated in its ejection period with use of the identified model inversely assuming the estimated parameters to be invariable during the cardiac cycle. Classical windkessel model with some modification was used for the estimation. In animal experiments cardiac output were changed by abrupt loading and unloading with 500ml of blood. Natural heart flow were well estimated with the counter pulsation with the delay time of 50%. However, the waveforms showed oscillation compared with measured ones. It is concluded that stroke volume of natural heart and cardiac output could be predicted well by this method.

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The purpose of this study is to identify the participation of the blood pressure to the heart rate variability which reflects the autonomic nerve response to the systemic ventricular assistance. For this purpose, the coherence of the blood pressure fluctuation against the heart rate was analyzed in long-term animal experiments using adult goats under the ventricular assistance of different driving modes. A high coherence was observed in 0.1Hz (Mayer wave) and 0.3 Hz (respiratory arrhythmia) under both synchronous and asynchronous modes. Especially, the coherence of systolic and pulse blood pressure was very high. The coherence of blood pressure against the heart rate reflects the participation of the blood pressure to the autonomic cardiovascular control mechanism. Therefore, this evidence indicates that the blood pressure has an influence on the autonomic nervous system which oscillates the heart rate. In addition, the power spectrum of systemic resistance, calculated from the cardiac output and the blood pressure, had only one spectral peak (0.05Hz) with high coherence against heart rate and blood pressure. It was concluded that the coherence spectral analysis could reveal the mechanism of the heart rate variability under ventricular assistance and furnish useful information concerning the driving mode of the ventricular assistance.

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Continuous monitoring of pump performance is essential and effective for optimal driving of pulsatile type blood pump. For this purpose, real-time measurement of blood volume in a pump (Vb) is necessary. We contrived a practical method for continuous Vb estimation by measuring electrical impedance (Z) in the blood chamber of pump. This method was evaluated with our air-driven diaphragm type pump. Z was measured by charging the alternating current (50kHz, 0.4mA) between two connectors of pump as electrodes. In vitro tests, Z showed maximum value at full-empty state and minimum at full-fill, respectively. The Vb calculated by an exponential equation of Z was linearly related to real Vb (r=0.99). In vivo tests with goats, pump output (Op) estimated by this method was linearly related to Op measured with electromagnetic flow meter, and was effective to evaluate pump performance. For calibration, this method needed only to measure Z at full-fill state. This method was more useful for the trigger system of full-fill full-empty drive than the other system because of direct measurement of Vb. We conclude that this method is practical to estimate pump performance even if implantable type pumps were used, and easily applicable to any kind of pulsatile type pumps.

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In order to determine the optimal drive condition of total artificial heart, renal sympathetic nerve activity (RSNA) were analysed by the use of power spectrum and coherence function. Two pneumatically actuated sac type ventricular assist devices were implanted, and after the both pump driving, natural heart was electrically fibrillated to constitute the biventricular bypass (BVB) type TAH model. After the left frank was opened, bipolar electrode was attached to the left renal sympathetic nerve. Values of the squared coherence between the arterial pressure and RSNA were measured. Largest peak coherency was observed when BVB was driven at the same frequency of the natural heart beat before fibrillation, suggesting that that this frequency was the optimal for the baroreflex system.

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Performance and characteristics are compared among the artificial hearts made in Hiroshima University. A brushless dc motor, Harmonic Drive reduction gears, and a cylindrical cam are used in one artificial heart, an ultrasonic motor and a crank chain in the second artificial heart, a brushless dc motor with a worm gear or with a gear head and a link mechanism in the third. Blood chambers made of Biomer are cylindrical or lenticular in accordance with the form of the pushers. An ultrasonic motor has large torque with slow speed, but the test result shows that the ultrasonic motor at present is not so powerful as to meet the demand of our artificial heart. Camfollowers used with the cylindrical cam are worm out in some extent. The motion of the pusher is linear reciprocation with the crank chain or with the cylindrical cam, but it is swing motion with the link mecha-nism. The motor is required as small as possible, of which speed and power are 40-150rpm and 15W, respectively.

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To supply power for driving a totally implantable artificial heart, one of the most advantageous methods is to transmit it through the skin in the form of electromagnetic energy from outside the body. In principle, such transcutaneous energy trans-mission is possible by means of electromagnetic induction between two coils placed face to face on each side of the skin. With such a construction, however, the coils are liable to dislocate themselves by the movement of the body, resulting in the reduction of the energy transmission and efficiency. In the externally coupled coil system proposed in this paper, part of the internal coil is protruded out from the body in the form of an arch, but with the skin completely covering it. Into the hole of the arch is inserted a ferrite core, and on the core is closely wound the external coil. This coil configuration not only assures stability of operation, but also a greater coupling between the coils. Results of in vitro measurement showed that the average transmission efficiency (DC to DC)is 79% with the load changing from 5Ωto 50Ω. Also, reduction of efficiency due to dislocation of coils was found to be less than 1%, showing that this new system can be used without the necessity of coil alignment.

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We examined the effects of the sizes of the inlet port and the outlet port of the pump on its output characteristics. The maximum output power can be obtained at the diameter of the inlet port of 12mm and at the width of the outlet port of 5mm. The most critical part of the pump in durability is the seal membrane. Therefore stress distribution in the seal membrane was analyzed using Finite Element Method. It was revealed by these analysis that the maximum tensile and compressive stresses were generated around the junction of the oscillating rod. About eighty percent of these maximum stress was due to the deformation by the declining of the oscillating rod. About twenty percent of them was due to the torsional moment of the rod. Less than one percent of them was due to the pressure in the blood chamber.

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A new pulse generator for experimental cardiomyoplasty was developed. The size and weight of this pulse generator were 115×60×23mm and 197 grams. Cardiomyoplasty using the lattissimus dorsi muscle flap (LDMF) was carried out on 7 mongrel dogs' normal heart and the LDMF was driven by this pulse generator. The hemodynamic changes were evaluated during stimulation. The arterial, pulmonary arterial, pulmonary capillary wedge and the right atrial pressures significantly ascended, and the cardiac index increased with a statistical significance. The newly developed pulse generator worked well for stimulation of the LDMF in acute experiments and chronic experimental use was warranted.

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For cardiac assistance using skeletal muscles, wrapping the heart with the latissimus dorsi muscle is mainly used. When making a latissimus dorrsi muscle graft, only the thoracodorsal artery is preserved. Using 3 anatomic cadavers, we examined whether the entire blood circulation of the graft can be maintained with the thoracodorsal artery alone by measuring the ratio of the area supplied by the artery to the entire area. The area supplied by the thoracodorsal artery occupied about 25% of the entire area. Collateral circulation in the remaining area may be a study subject hereafter.

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Cardiomyoplast (CMP) has been performed for heart failure patients. The evaluation of cardiac function under CMP, however, was difficult and the performance of CMP was unclear in clinical cases. In order to clarify the effect of CMP, we applied left ventricular pressure-volume loops relationship using a conduct-ance catheter (CC) in acute animal expert-ments. In normal heart goats (n=5), electrically preconditioned latissimus dorsi muscle flap (LDMF) was sutured around the ventricle counterclockwise and was stimulated synchronously by the electrical stimulator with bursts. The left ventricular volume was measured using a CC with and without LDMF stimulation. Maximal end-systolic volume elastance (Ees) was determined from multiple pressure-volume loops obtained during a brief preload reduction by occlusion of an inferior vena cava. There are no significant differences in Ees, stroke volume, left ventricular(LV) end-diastolic pressure, LV end-systolic pressure and end-diastolic volume between, with and without LDMF stimulation. These data showed that the CMP did not affect LV performances of normal heart in goats. However, a CC was useful to evaluate LV functions and to avoid the limitation of cardiac diastolic movement with CMP.

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We made a right-heart-failure model by ligating all branches supplying right ventricular free wall. Then we wrapped the right ventricle with left latissimus dorsi muscle (dynamic cardiomyoplasty). After electrical training the muscle for six months, we evaluated the performance of right ventricular cardiomyoplasty on chronic phase by stimulating skeletal muscle with amplitude 5V, width 0.5 msec, duration 200 msec, and 20 Hz frequency. Left ventricular systolic pressure, right ventricular systolic pressure, cardiac output, and right ventricular stroke work increased significantly with muscle stimulation. Left ventricular end diastolic pressure, right ventricular end diastolic pressure, and central venous pressure were decreased. The augmentation of right ventricular function by cardiomyoplasty was observed for at least four hours without fatigue of skeletal muscle. We also examined the anatomical and histological changes of right ventricular free wall infarction. The right ventricle chamber became enlarged and the free wall was very thin. Vacuole necrosis and fibrosis were detected on right ventricular free wall, indicating that our method of making right ventricle infarction was successful. Thus right ventricle dynamic cardiomyoplasty was effective for the augmentation of ventricular performance on an akinetic right ventricle.

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We have studied three-dimensionally (3-D) reconstructed images of atrioventricular (AV) annuli based on four-chamber magnetic resonance (MR) images for total artificial heart (TAH) implantation. To assess the interrelationship among the AV annuli and the thorax, we applied the frame of reference of the vertebral canal to these images. The Z-axis was along the vertebral canal, the Y-axis in the anteroposterior direction. The angle alpha was defmed as the angle between the X-axis and the intersection between the plane of the annulus and the X-Y plane. The angle beta was defined as the angle between the Z-axis and the intersection between the plane of annulus and X-Z plane. The angle gamma was defined as the angle between the plane of the annulus and the anterior thoracic wall. We determined each angle for the mitral annulus (MVA) and tricuspid annulus (TVA) in four normal subjects to be as follows: alpha-MVA, 20.5-393 degrees;alpha-WA, 26.1-43.5 degrees;beta-MVA, 4.7-49.4 degrees;beta-WA, 4.4-40.9 degrees;and gamma-WA, 35.2-44.1 degrees.
It is suggested that reconstruction of the thoracic wall and AV annuli using the frame of reference of the diaphragmatic surface of the heart would facilitate evaluation of the spacial requirements for TAH implantation. Research to define this new frame of reference is in progress.

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A vibrating electromagnetical ly driven artificial heart which had an unique structure and pumping mecha-nism, was developed in our team. In order to analyze the blood flow patterns inside the pump incorporated with the Jellyfish valve, flow visualization study was performed by the tracer-methods. When Jellyfish valve opend, inflow to the valve chamber constitute to cause the large swirl, which washed out the blood in the central point of the Jellyfish valve. These results ofthis study indicate that the vibrating electromagnetically driven artificial heart with jellyfish valve has the thrombo resistant properties which is very im-portant facter in the clinical use of tortal artificial heart.

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A design concept of hybrid artificial endocardium, which is incorporated into biomechanical pump using skeletal muscle, was proposed and its prototype model was devised. The hybrid artificial endocardium is constituted of polyurethane porous membrane as a structural matrix, fragmented blood vessel and collagen gel. Supposed that tissue regeneration is promoted by cells outgrown from fragmented vessel embedded in collagen fel, blood vessel like structure could be formed, which may function as an endocardium. Polyurethane porous membrane was prepared by solvent co-casting with fine sodium chloride powder, resulting in elastomeric substrate with 150-500μm pore. Fragmented and trapped adult goat aorta in collagen gel was cultured in 5% C0₂, 37°C. Endothelial cells and smooth muscle cells outgrew from tissue fragments at 4th day. After 21 days, outgrown cells on a collagen gel surface tended to regenerate the endothelium-like monolayer sheet and aligned in collagen gel. It is concluded that the vessel wall regeneration technique coupled with a microporous elastomeric membrane could provide a basis for hybrid artificial endocardium.

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GAL PUMP. Ventricular support with a centrifugal pump (CFP) has been used increasingly for the treatment of cardiogenic shock. However cannulae and tubes for CFP are those of pneumatic ventricular assist system or usual extracorporeal circulation, being not proper to CFP. We developed new cannulae for ventricular support using CFP (BP-80). The new cannulae have inner diameter of 6 mm and maintain a pump flow of 2.0-4.2 L/min at pump speed of 1500-2750 RPM. The new cannulae may be useful to quick introduction of ventricular assist and stable maintain of a pump flow.

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A new method of right ventricular assistance in which the right ventricle was bypassed by centrifugal pump without thoracotomy was designed. In order to insert the outtlow cannula into the pulmonary artery, we used Swan-Ganz catheters inside of it. Acute experiments were performed in 11 adult mongrel dogs. Biventricular assistance using this newly designed right ventricular assistance was instituted jointly with pneumatically driven left ventricular assist device. After that, biventricular failure was induced by normothermic myocardial ischemia by both aortic cross-clamping and ventricular fibrillation for 30 minutes. Initiating biventricular assistance described above for failed heart, we could maintain cardiac output 77.4±33.2ml/min/kg and reduce the systolic and enddiastolic pressure of the right ventricle, while left ventricular assistance alone was not enough because of the right ventricular failure. If regurgitation via the pulmonary or the tricuspid valve was present, right ventricular unloading effects were also well maintained. We conclude that this new technique is very useful for the treatment of acute right ventricular failure especially after institution of LVAD.

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A magnet coupling type centrifugal pump for Percutaneous V-A Bypass was developed and evaluated in IN VITRO and EX VIVO. A newly designed centrifugal pump is a ”straight path centrifugal pump(SPC. Pump)”, which has a rotating disk with six blood paths and a coupling magnet. Each blood path of the disk is almost straight. Priming volume of the pump is only 46cc. Under pump rotational speed of 2500 rpm, output pressure of the pump was 560mmHg. Generation and growth of gaseous cavitation was not seen under negative pressure about 200mmHg. Hemolysis tests were performed with fresh bovine blood at flow rate of 3L/min against pressure load of 400 mmHg. Hemolysis of the SPC. Pump was approximately 30% lower than the cone type centrifugal pump. We performed the 29 hours V-A bypass experiment using a mongrel dog. At the end of the experiment, there was no apparant thrombus formation in the pump.

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The valvo-pump, an axial nonpulsatile blood pump implanted at the heart valve position, has been developed. The valvo-pump consists of an impeller and a motor which are encased in a housing. An impeller with 5 vanes (22.0 mm in diameter) is used. The impeller is connected to a samarium-cobalt-rare-earth magnet direct current (DC) brushless motor measuring 21.3 mm in diameter and 24.9 mm in length. Sealing is achieved by means of a ferrof luidic seal. A pump flow of 16.1 L/min was obtained at a pump differential pressure of 7.7 kPa (58 mmHg), and a flow of 5.0 L/min at 18.4 kPa (138 mmHg). Sealing was kept perfect against a pressure of 29.3 kPa (220 mmHg) at 9000 RPM.

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To evaluate the fibrinolysis therapy using urokinase as an anticoagulant for LVAD, coagulative study was made comparing with protease inhibitor (nafamostat mesilate).
U rokinase administration as a sole anticoagulant causes marked fibrinogen decrease and significant α₂-plasmin inhibitor decrease. It is considered that urokinase cannot prevent the activation of the blood coagulation system. So sole administration of urokinase is not an appropreate anticoagulation therapy for LVAD. Some conbination therapy is desirable for urokinase.

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We conducted and examined two experimental studies about eicosapentaenoic acid ethyl emulsion(EPA-E) in order to reduce the destruction of blood cells. We used the closed circuit(1), and the left heart bypass by centrifugal pump in mongrel dogs (2). Both studies, the main groups, we devided into two groups. One group was administrated EPA-E before examination (”EPA-E group”). Another group was not done (”control group”). We show the results as follows: 1.) In the closed circuit experiments, there was no significant difference between EPA-E group and control group. 2.) When EPA-E was administrated in left heart bypass in dogs, the level of erythro-aggregation was significantly lower, the increase of plasma free hemoglobin and decrease of platlet count were suppressed compared with control group. In addition, during aortic clamp, the reduction of urine output in EPA-E group was less than control group. And the recovery of urine output after aortic declamp was more quickly in EPA-E group.

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Thrombus formation in the left ventricle is a serious complication which cause fatal systemic thromboembolism. We experienced 3 patients who complicated left ventricular thrombus during circulatory support after open heart surgery. In one patients who underwent with pneumatically driven left ventricular assist system heparin was administered intermittently keeping activated coagulation time (ACT) around 150seconds. In two patients with V-A by-pass (centrifugal pump, heparin coating tube and membrane oxygenator) we used continuous infusion of heparin and FUT controlling ACT around 200 seconds. Artificial materials implanted in the ventricle and stagnation of the blood stream seemed to be major risk factors of the left ventricular thrombus formation during circulatory support. We suggested that local heparinization by continuous heparin infusion into left ventricle or left atrium and promotion of natural heart ejection by administration of catecholamine were useful for prevention of the left ventricular thrombus formation.

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Long-term Results of Valve Replacement with Bioprosthesis: Evalution of Prosthetic Valve Function by Echography. Between May, 1988 and June, 1991, bioprosthetic valves in the mitral position were valuted echocardiograohically in 30 patiants. Of the 30 patiants, 15 (replacement group)underwent replacement of the bioprosthesis in this period, because of primary tissue failure of the bioprosthesis. The other 15 patiants (nonsurgical group) have not required replacement of the bioprosthesis. There were no significiant differences in left ventliculer dimention, and mitral valve area on the echocardio-gram between non-surgical group and re-opera-ted group. However, peak-flow veloci-ty through the bioprosthesis was significantly high in the replacement group than non-surgical group, and the peak-flow velocity in the 15 of the replacement group was more than 1.95m/sec. We conclude that echocardiography, especially Doppler echocardiography is an effective and reliable method to determine the timing of replacement of bioprosthesis with primary tissue failure.

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From February 1975 to August 1981, 19 patients had tricuspid valve replacement, either isolated (6) or combined with replacement of other valves (13) by means of a standard, glutaral-dehyde-preserved Hancock porcine bioprosthesis. Follow-up ranged from 0.2 to 16.2 years (mean, 9.0±4.6 years) and was completed in 100%. Primary tissue failure (PTF) of the tricuspid Hancock valve was noticed in one patient of 9 years-old boy 40 months after implantation. Actuarial freedom from PTF at 10 yars was 94±6%. Five couples of mitral-tricuspid Hancock valves explanted simultaneously from the same patient after 97 to 166 months (mean, 136±25 months). Gross examination showed no significant changes in the explants from the tricuspid position but degenerative changes with dysfunction in those from the mitral and aortic positions (p<0.03). There were 4 tricuspid prosthesis-related events except prophylactic removal; valve thrombosis, prosthetic valve endocarditis, PTF, and periprosthetic leak. Actuarial freedom from these events at 10 years was 74±10%. Selection of tissue valve in the tricuspid position is acceptable because low incidence of prosthesis-related complications and good durability for more than 120 months in not only adults but children.

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One hundred and twenty-six Medotronic Hall(MH) valves were implanted in 117 patients between October 1982 and January 1990. MH valves were implanted in 102 patients for initial valve replacement, and in the 15 for redo replacement. In the 102 initial group, early mortality was 9.8% and late was 3.9%. Redo replacement was done in 5 patients due to prosthetic valve endocarditis, thrombosed valve, open stuck, and closed stuck. In the 15 redo group, early mortality was 40%. Thromboembolic episode was occurred in 4 patients; cerebrovascular arteries were involved in all and only one had persisted disturbance of visual field. According questionaries, 62.5% of patients with MH valves expressed their satisfaction with the results. Patients with MH valves showed relatively good postoperative results and almost similar results of patients with St. Jude Medical valves.

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