Weaning from CPB and indications for LVAD are performed considering hemodynamic parameters measured during CPB. But these measuring values contain some problems at the points of reliability and predictability. Our clinical investigations on V5 of ECG revealed that the increasing height of R wave of QRS in V5 between 30 ms and 50 ms and 50 ms from initial potential of QRS indicates the improvement of myocardial contractility and conduction system of the left ventricle. The same results were made sure using 45 min. global ischemic dog heart under normothermia. The difficult cases on weanig from CRB was 1% of our cases during 10 years. The analysis of ECG V5 is useful for dicision of weaning from CPB.

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The goal of this study is to clarify the effects of nonpulsatile perfusion on pulmonary circulation compared with pulsatile perfusion. Method: Right heart was totally (100%) bypassed between RA+RV and PA using a nonpulsatile (NP) or a pulsatile (P) blood pump in 14 dogs. The main PA was ligated, the bypass flow was maintained at the prebypass level throughout the experiment, and the systemic circulation was kept by natural beating heart. The parameters measured were such: extravascular lung water (EVLW), PAP, LAP, colloid osmotic pressure (COP), blood gas, cardiac output (CO), AoP, and CVP. Results: 1) A significant increase in EVLW was observed in the NP group after bypass (p<0.05). 2)Arterial PaO₂ in the NP group had a tendency to be lower than the P group, although no statistical significance was observed. 3)No significant difference was observed between the NP and P groups on PAP, LAP, COP, and CO. The results suggest that nonpulsatile perfusion in pulmonary circulation has a higher tendency to accumulate lung water, although it does not differ significantly from pulsatile perfusion in gas exchange.

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This study i s to evaluate the hemodynamic effects for the acute right heart failure of RVAD of which outlet conduit is inserted into the pulmonary trunk and inlet conduit is inserted right atrium via anonyma vein, in comparison with the effects of volume loading alone. We used 16 mogrel dogs. Six dogs were studied without RVAD(cgroup-1) and 10 were with RVAD group-II). In this study, cardiac output was maintained at 100me/kg/min, and the bypass flow ratio in group-II was maintained about 50%. Acute right heart failure was prepared by producting tricuspid regur etation. The result was that the right ventricular stroke work index was increased in group-I, but decreased in group-II despite pulmonary stenosis caused by insertion of outlet conduit. This is because the right ventricular preload(volume) was reduced and therefore systolic right yentricular pressure was not significantly increased. Mean right atrial pressure in group-II is significantly less than in group-I. his suggests that RVAD inserted via veins without thoracotomy can assist right ventricle enough under right ventricular failure.

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We examined and compared the hemorrhagic factor, pen- and postoperatively, between surgery employing femoro-femoral bypass (using the roller pump), and that by left heart bypass (using the centrifugal pump and a heparine-coated tube). Both of these procedures were administered as extracorporeal circulation in the surgery of the descending thoracic aorta in our department. Out of 38 cases, 28 underwent femoro-femoral bypass (FF group), and in 10 cases, left heart bypass was employed (LH group). As a result, in the FF group, 5 cases (17.9%) showed pen- or postoperative complications; two of the cases succumbed perioperatively because of blood loss and two cases hospital death from intrapulmonary bleeding. In contrast, in the LB group, no fatality has been reported, although intrapulmonary bleeding was observed in 1 case (10.0%). The average amount of postoperative blood loss tended to be lower in the LH group. Moreover, the postoperative minimum platelet count averaged 7.1 × 10⁴/mm³ in the FF group against 12.6 × 10⁴/mm³ in the LH grouip. Thus, the LH group encountered only a mild reduction in platelet count, which we regard as one of the factors which reduced postoperative blood loss. On the basis of these findings, it is our conclusion that the left heart bypass by centrifugal pump is an effective technique which ameliorates fatal pen- and postoperative hemorrhagic complications.

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During the last year, we performed circulatory and respirarory assist using centrifugal pump (Biopump) and membrane oxygenator. 2 patients with adult respiratory distress syndrome were treated with venovenous bypass utilizing percutaneous catheters. We achieved 3.0 liters in these patients. The other 2 patients developing circulatory failure following open heart surgery were treated with left heart bypass and/or venoarterial bypass. One of them were able to wean from circulatory assist and survived. Biopump and percutaneous cannula appear to be effective mechanical support devices.

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Left heart bypass with the Bio-pump was used for thoracic aortic aneurysm operation in 7 cases. The patients were ranged 43-75years(mean age 58.6 years), 5 were males and 2 were females. All the patients underwent graft replacement with use of intraoperative autotransfusion. Of the three were the dissecting aneurysm and were added the Ivalon Sponge Occulsion method. During the LHB, systemic hepriniz ation was undergone to maintain ACT's about 200 sec. FPA and FDP levels were elevated during operation, so that evidence of intravascular coagulopathy was suspected. But clinical evidence of bleeding tendency or microaggregation was not appreared in all cases.

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Clinical use of the Bio-pump as a left ventricular assist device for 5 patients with profund postoperative heart failure was reported. One of them could wean off from LVAD on 9th POD, but died one day later with severe hepatic failure.
Bio-Pump has a problem of thrombus formation in inside corn. We discussed about a appropriate anticoagulant therapy during LVAD.

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Cardiac allograft failure can be caused various factors. Of 304 cardiac transplant patients, 10 received mechanical circulatory support for allograft failure. Five received IABP and one was weaned from LABP. Three received a ?newly developed intraarterial axial-flow blood pump(Hemopump) and all patients were able to wean from Hemopump. Ttio received right heart bypass (RHB) with a centrifugal pump and were weaned from RHB. In cardiac allograft failure, temporary mechanical support is a reliable option during allograft recovery and early implementation and less invasive methods are preferable in these immunosuppressed patients.

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Intraaortic balloon pumping (IABP) has been clinically employed for the patients with profound cardiac failure before and after cardiac surgery. However, there were a few patients who could notbe cured from the failing heart in spite of IABP assistance. Until now, mechanical circulatory assistance (MCA) such as IABP, IABP+V -A bypass and left ventricular assistdevice (LVAD) has been utilized in 188 cases with cardiogenic shock and low cardiac output syndrome. They consisted of 169 cases of IABP, 15 cases with IABP+V -A bypass and 4 cases of LVAD. Consequ -ently, 134 cases have been weaned from the MCA. That is, 125 out of 169 cases with IABP, 7 out of 15 cases with IABP+V -A bypass and 2 out of 4 cases with LVAD for ventricular septal ruture or combined valvular heart disease were weaned from each circulatory support. From these clinical experiences, the effects of LVAD were obviously confirmed hemodynamically in comparison with two others of IABP and IABP+V -A bypass. Selection of the MCA should be based on the severity of the patients conditions, and multiple organ failure should also be prevented during the MCA. LVAD was available as a bridge use to the heart transplant.

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The efficacy of the latissimus dorsi muscle (LDM) cardiomyoplasty was evaluated experimentally in eight mongrel dogs. Using the anesthetized open-chest dogs, the electrically pre-conditioned LDM was sutured around the entire ventricle, and was stimulated synchronously by the pulse train stimulator. (synchronization ratio 2:1). The pulmonary artery pressure and the left ventricular pressuve were measured, and the left ventricular volume was also estimated continuously with a multi-electrode volume-conductance catheter. Emax was determined from multiple pressure volume loops obtained during a brief preload reduction by balloon occlusion of inferior vena cava. When the LDM was stimulated synchronously, the pulmonary pressure demenstrated a systolic augmentation, and the left ventricular stroke volume and ejection fraction improved significantly. The pressure volume loops of the left ventricle shifted to the left, and an increase in Emax was clearly observed. These results showed that the contractility of the left ventricle was improved by the synchronous contraction of the LDM wrapped around both ventricles.

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Changes in skeletal muscle fiber construction after low frequency electrical conditioning were histochemically analyzed with image analyzer. Elecrtrical conditioning (10Hz) for 2 weeks induced the followings in the muscle fiber construction: decrease in weight, increase in fatigue resistant fibers, and alteration to smaller and rounder fibers. These findings indicate that aerobic metabolism is increased and skeletal muscle obtains fatigue resistance by this electrical conditioning.

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Thrombus formation is one of the most difficult problems in total artificial heart experiment. Hypercoagulability showing a marked decrease in platelet count and antithrombin III level, and increase in fibrinopeptide A and Bβ15-42 levels, relates closely to thrombus formation. Hypercoagulability develops not only during and immediate after surgery, but also during postoperative complication such as sepsis. We concluded the necessity of anticoagulation therapy during a hypercoagulable state after total artificial heart replacement.

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Comparative study was made to establish an ideal anticoagulation therapy for LVAD. Protease inhibitor (FUT-175) can prevent the activation of intrinsic blood coagulation system by the anti-thrombin and anti-plasmin effect, and is considered to be more effective anticoagulant for LVAD than thromboxane A₂ synthetase inhibitor (OKY-046).

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It has been recently reported that the stagnation of the blood in the left ventricle of severe myocardial damage under the condition of the left atrio-aortic bypass. The effct of the anti-thrombus formation in the left atrio-left ventricular combination bypass has been tested in 10 dogs. Results obtained suggested that the hemodynamic effct and the anti-thrombus formation in this combination bypass is much better than in the left atrio-aortic bypass.

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The effect of synchronized coronary venous retroperfusion (SRP) was studied in 20 dogs with coronary occlusion. Ten other dogs served as untreated controls. At 6 hours after occlusion, the left ventricular end diastolic pressure (LVEDP) significantly decreased in the treated group, the cardiac index increased in the treated group as compared with the control group at 6 hours of occlusion. Myocardial necrosis (TTC) expressed as percentage of the ventricle (5.9±3.1% vs. 13.8±5.1%) was significantly lower in the SRP group relative to the untreated group. Synchronized retroperfusion has been shown to be an effective treatment of experimental myocardial ischemia.

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Three different ECG synchronous driving modes of LVAD were performed in nine anesthetized dogs: diastolic driving mode (D), systolic driving mode (S), systolic driving mode in combination with IABP (SI). In both S and SI, the assist flow was significantly higher and the stroke work was significantly lower than those in D. The aortic pressure at the beginning of left ventricular (LV) ejection (APej) was higher in the order of D, S, and SI. The peak LV pressure was significantly lower in SI than those in S and D. The LCX flow in SI was similar to that in D. We concluded that synchronous systolic driving of LVAD became more effective by combination with IABP in terms of systolic unloading and diastolic augmentation.

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Current circulatory assist methods, such as intra-aortic balloon pumping (IABP), are not always adequate to save acute circulatory failure patients. Therefore, a stronger, percutaneously accessible assist method is reqiured. We found that the combination of IABP and CP generated a profound circulatory assist effet, and we have consequently developed a new assist system in this study Asac type blood pump wiht a volume of 20ml and a single Port without a valve, was daveloped for CP. In the mock circulatorytest, the relationrhips among the driving conditions of the CP, the diameter of the cannula, and flow through the blood pump were evaluated. The pump flow increased proportionary with the increase in positive and negatdve air pressure. However, it did not respond to change in pulse rate. The maximun pump flow was obtained in the 40-50% S/D range.

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Its effectiveness was experimentally studies by using LV mongrel dogs with left ventricular failure. The results were as follows: Hemodynamics had improved and the anti-arrhythemic effect could be recognized electrocardiographically, however, free hemoglobin concentration had increased. It was therefore suggested that clinical application would be possible provided that a better material for the catheter was selected.

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The effect of a left ventricular assist device (LVAD) was studied in eight goats whose coronary arteries were artificially occluded. Subendocardial blood flow (ENDO-MBF) and oxygen partial pressure (ENDO-MPO2), subepicardial blood flow (EPI-MBF) and oxygen partial pressure (EPI-MPO2) were measured serialy in ischemic myocardium with or without LVAD driving. ENDO-MBF, EPI-MBF and ENDO-MPO2 were not changed by LVAD. The decrease of EPI-MPO2 was slightly prevented by LVAD.

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We had 14 cases which we used conventional hemodynamic parameters for determing the timing of wening frome IABP, and weaned frome IABP. In examine the SDR of these 3 unsuccessful case, all 3 had the SDR of less than 1.0. Therefore, accordingly, we feel that using SDR in determing the timing of weaning frome IABP is very useful.

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The Omnicarbon prosthetic valves (OC) were implanted in the mitral position in 26 cases. The early clinical and hemodynamic results were evaluated comparing with those of St Jude Medical (SJM), the Duromedics (DM), and the Bjork-Shiley prostheses. The serum LDH and bilirubin levels in OC group were significantly lower than those of the other groups. Hemodymamic study was assessed with continuous wave doppler. There was no significant difference in peak velocity suggesting mitral pressure were similar in all groups. The pressure half times, however, were significantly decreased in DM and OC groups than SJM and/or B-S group, indicating that effective prosthetic valve orfice areas were larger in DM and OC groups.

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Functional property of the Björk-Shiley prosthetic valve implanted in the mitral position of 38 patients (20 convexo-concave valve and 18 monostrut valve) was investigated by cineradiography. The maximum opening angle of the tilting disc was 58±2° of convexo-concave valve and 70±4° of monostrut valve, There was no change in the maximum opening angle, opening time and closing time of the disc observed during follow up period. It is noteworthy that the maximum tilting angle of the valve ring is over 10° in most case with the valve size of 31mm. This result suggest that choice of 31mm prosthetic valve is improper.

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The hemodynamics of various mechanical valves were studied in the mock circulation system by analysis of flow-pressure gradient and opening angle. All valves were tested in the simulative states of normal hemodynamics, low output, arrhythmia, hypovolemia and vasoconstriction. The St. Jude Medical valve showed the best flow-pressure gradient curves of all valves. The photosensor system revealed full opening of each valve in the mock circulation. Clinically, from 1984 to 1989, 48 St. Jude Medical valves were implanted in patients aged 30 to 75 years. There were three early deaths and two late deaths. Follow-up has been 100% for a total of 97.3 patient-year. At five years and six months, the actuarial survival rate, excluding early deaths, is 95.9%. The total incidence of various valve-related complications was 1.0%/patient years. Post-operative continous wave Doppler echocardiography revealed the valve function in mitral position as follows; peak flow velosity 1.29±0.39m/sec, pressure half time 74.9±21.0 msec and pressure gradient 6.7±3.2mmHg. These data were better than other mechanical valves implanted in the same period and corresponded well to the in vitro analysis.

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Follow-up studies were made on 48 cases. Incidence of cuspal thickening was noted on 38%, 61% of cases for 5 and 7 years Max. velocity at the LV inflow tract was 1-1.5m/s so long as the valve was functioning normally. Pressure half time (PHT) was gradualy prolonged year by year. In the patients with stenosis, PHT was prolonged and Max. V was increased. In the patients with regurgitation, PHT was remained within normal rainge while max. V was increased.

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Comparative studies were made between 33 cases replaced aortic valve with monostrut valve and 24 cases replased with sphrical valve. Actual survival rate at 4 years after operation was 100% in monostrut group and 91.7% in sphrical group. It was not significantly different to the actual survival rates of these groups. Serum LDH level of monostrut group were significantly increase after operation (P>0.01). But, results of this new valve is satisfactory clinically.

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Between Oct. 1984 and May 1989, 84 bileaflet mechanical prosthees, such as Duromedics (DM) and St. Jude Medical (SJM) valve were implated in mitral position. On the basis of this expriense, the differensces between both prostheses on early and long-term complications were reported. Hospital mortality (Within 30 days post-operatively) was 4.8% (4/84 patients) for overall. There were 6 additionallatedeaths. The actuarial survival rate at 4 years, hospital mortality excluded, is 90.3% for DM, 87.4% for SJM, between which we didn't find anysignificant difference, and 89.6% for overall, satisfactory. 5 patients suffered thromboemboism (2.9%/pt. -yr.), and event-free rate from thromboembolism was 91.7% for DM, 86.5% for SJM, 90.2% for overall, Furthermore, we encountered 3 thrombosed DM, valve (2.4%/pt.-yr.), suggesting that incomplete anti-coagulant therapy seems to be the cause of thrombotic complications, In order to improve the long-term result, strict and careful anti-coagulant therapy should de used.

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A new bioprosthetic cardiac valve cross-linked with glycerol polyglycidyl ether (polyepoxy compound=PC) was developed. It was evaluated in animal studies. Aortic valves harvested from mongrel dogs were treated with PC (PC valve). RV-PA bypasses were made in 7 dogs with a conduit composed of a PC valve and two vascular grafts attached to the inflow and outflow sides of the valve (PC-valved conduit). The main PA was ligated. The pressure gradient across the PC valve was 5mmHg and the diastolic pressure of the PA was 19mmHg, which indicated almost no stenosis nor regurgitation of the PC valve. RVG performed at 36 days (1 dog) and 37 days (1 dog) showed the PC valve in good function and no visible thrombus in the valve. Biologic materials cross-linked with PC increase in strength as do those cross-linked with glutaraldehyde (GA). While biologic materials cross-linked with GA become yellowish, hard and hydrophobic, those cross-linked with PC maintain their original white color and pliability, and become hydrophilic and hydrated. The hydrophilicity and hydration, compared with hydrophobicity and less hydration, provide sufficient antithrombogenicity and better characteristics for infiltration and diffusion of water which includes nutrition, oxygen and electrolytes, etc., leading to inhibition of material degeneration. As the PC-treated vascular graft is reported to have shown no calcification in long-term results, the PC-treated bioprosthetic cardiac valve should also not calcify with long-term use. Therefore, the PC valve displays good valve function and sufficient antithrombogenicity and is expected to have excellent durability without calcification or degeneration.

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A consecutive series of 299 mitral valve replacements was performed from 1967 to December, 1988. There were 120 men and 179 women, whose age ranged from 9 to 74 years (mean 46.7). The cumulative follow-up was 1, 675 patients-years. The follow-up rate was 98.3%. A mechanical valve was implanted in 105 patients (8 Starr-Edwards disc, 8 Starr-Edwards ball, 2 Bjork-Shiley, and 87 St. Jude Medical valves) and a bioprosthetic valve in 194 patients (112 Hancock, 22 Ionescu-Shiley, and 50 Carpentier-Edwards pericardial valves). A concomitant operative procedure was performed in 184 patients (62%). Early mortality was 3.8% for the mechanical valve group and 3.6% for the bioprosthetic valve group. The long-term survival rate was similar in patients who received a mechanical valve and a bioprosthesis (73±8% versus 73±4% at 10 years). The incidence of thromboembolism and anticoagulant-related hemorrhage was not significantly higher in the mechanical valve group (free rate of 64±13% versus 82±4% at 10 years). Structural valve failure was significantly more common in the bioprostheses (free rate of 97±3% versus 79±5% at 10 years; p<0.05). Reoperation was significantly more cannon in the bioprostheses (2.9% versus 0.6% per patient-years) (p<0.05). The rate of endocarditis was similar in the two groups. All valverelated morbidity and mortality was 2.6% per patient-years for the mechanical valve group and 5.4% per patient-years for the bioprosthetic valve group (p=ns). Structural valve failure is the main disadvantage of mitral bioprosthetic valves, with a probability of dysfunction of about 20% at 10 years.

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Mitroflow (M-F) valve was implanted on 33 cases between 1983 and 1988, and Björk-Shiley (B-S) valve was implanted on 126 cases from 1975 to 1988. The clinical results of cardiac valve replacement, incidence of postoperative valve failure and thrombo-embolism, and effective valvuler orifice area measured during surgery were analyged in both M-F valve and B-S valve groups. From these results, it may be concluded that M-F valve had better hemodynamics and lower thrombogenesity than B-S valve, but as far as durability was concerned it was not satisfactory.

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Since 1966 several kinds of valve prostheses have been utilized for the patients with severe valvular heart diseases in our department. In the recent years, mechanical valve prosthesis with tiliting or leaflet function has been preferably employed to prevent valve-related complications. In this paper, our clinical experience of 71 patients who underwent valve replacement with Medtronic Hall valvular prosthesis was presented in detail. The patients consisted of 43 cases with mitral valvular diseases, 24 cases of aortic valvular diseases and 4 cases of combined valvular diseases. Valvular size from 25 to 31mm was used in the mitral position and 21 or 23mm was replaced in the aortic position. Mean value of the valve pressure gradient was 4.3mmHg in the mitral position and 11.5mmHg in the aortic position. These were no significant differences of pressure gradient in each group. In conclusions, the long-term experience with the Medtronic Hall valve demonstrated excellent hemodynamic performance with wider valvular orifice area as well as good durability and low risks of thromboembolism.

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A plastic ball valve which is aimed to have quantity production, lower cost and antithrombogenicity for a ventricular assist device (VAD) was designed and evaluated in the mock circulation and in chronic animal experiments using adult goats. This silastic ball valve is placed in the polycarbonate-made connector between inflow and outflow cannulae and the air driven sac. The prosthesis showed same flow volume characteristics as a same size of Bjork-Shiley (BS) valve. In the durability test using the mock circulation, 100 bpm drive maintained over 13 months without any dehiscence or abnormality of the prosthesis. Intensity of prosthetic clicks also minimized as compared to B-S valve during pump cycle. Results of 23 chronic animal experiments revealed no thrombus formation in the prosthesis without any antithrombogenic drugs administration. Hematologic data, such as free serum hemoglobin and LDH remained same level as a prior value of the operation. These results reveal clinical usefulness and readiness of the plastic ball valve for VAD which is made with our simplified manufacturing procedure.

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It is very important to grasp the fluid-mechanical property of a prosthetic valve on the various driving conditions, in order to develop a ventricular assist device (VAD). Therefore, the flow characteristics of a newly designed ball valve which consisted of a silicone ball and a polycarbonate housing was analized by means of the quantitative flow visualization technique and was compared with the Björk-Shiley prosthetic valve (BS-19ABP, spherical). The flow visualizations were carried out on the four different flow rate conditions (3.0, 2.0, 1.5 and 1.0L/min). It was observed that the decrease of flow rate effected neither on the maximum velocity nor on the velocity vector distributions of a ball valve in comparison with the Björk-Shiley valve. Furthermore, even on the low flow rate condition(1.0L/min), the decreases of the flow velocity and the shear rate, which could cause the thrombus formation, were not observed in the lower part of a ball valve. In conclusion, a newly designed ball valve has the fluid-mechanical property which meets the requirement of VAD.

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Relation between oxygen uptake and workload in bicycle ergometer exercise stres test was studied in eighty three patients who were received or scheduled prosthetic valve replacement. Oxygen uptake and workload at AT and peak achieved workload were assesed by percent attainment of perdicted normal value calculated from sex, age, weight and height. Percent attainment of VO₂ and work load at AT were closely related in patients with NYHA functional class I, II and III. Those at peak achieved workload were also closely related in patients with NYHA functional class I and II.

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In the cases of prosthetic valve replacement, aspirin 81mg/day (Group-A:10 cases) and ticlopidine 300mg/day (Group-T:10 cases) were administrated. In both Group, platelet count increased significantly at 14 pod. ADP aggregation in Group-T and arachidonic acid aggregation in Group-A were significantly suppressed at 14 pod. β-TG significantly increased and PF-4 tended to increase in both group at 14 pod. But the data of β-TG and PF-4 divided by platelet count were analyzed, and we found the increase of platelet release at 14 pod was based on the increase of platelet count rather than the increase of each platelet release.

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The Omnicarbon valve prostheses (O-C valve) were used in 30 patients, 8 underwent aortic valve replacement, 23 had mitral valve replacement. Follow-up was achieved for a mean of 22.7±14.1 months and a maximum 4 years. Thrombotic complications were not difined. Postoperative clinical status improved for all patients, in NYHA classification to 1.2 degree from 2.9 degree. The maximum open angle by cineradiography was 70±4.08°for aortic valve and 56±1.37° for mitral valve. The net flow area/orifice area ratio of mitral valve by cineradiography was 85.4±1.6%. Peak valve pressure gradients by doppler echocardiography was 18.38±3.0mmHg and 6.99±1.2mmHg for aortic and mitral valve. In mitral valve replacement, LAD by echocardiography and Q-I time improved significantly (P<0.01, 0.002) after the operation. Our data indicate that the O-C valve is safe, has good function and gives satisfactry clinical results.

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To analyze motion of the implanted tilting disk valves, the LAMA (Computer Aided Motion Analysis) system had been developed. With this system an open angle and the other complicated motion properties can be measured three dimensionally. Since it is a time-consuming process to analyze all the frames of the cinefilm manually, semi-automatic data acquisition and image processing system was newly developed to shorten data analysis time of the CAMA system. The image processing technique with binarization method realized to acquire the valve contour data semi-automatically, and shortened 20 min to analyze 90 frames compared to a manual procedure.

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One of the causes of the valve failures of the artificial heart was the high pressure gradient which appeared across the valve at the moment of valve closing by water hammer phenomenon. In order to decrease the pressure gradient across the valve, the shock absorbent material was used in the valve holding ring, then the pressure gradient was measured by using Mock circulation. An experimental model was developed, in which the shock absorbent material was used in the valve holding ring. The pressure gradients were compared among the control without any shock absorbent material (the valve was mounted in a rigid ring), Silicone, and the special shock absorbent material. The pressure gradient across the valve increased along with the increase of the % systole of the driving of the artificial heart. Maximum pressure gradient was measured at the moment of valve closing just after the valve opened completely. The maximum pressure gradient across the valve by the water hammer phenomenon was highest in the control, lowest in the model in which the special shock absorbent material was used in the valve holding ring. It became obvious that the special shock absorbent material was effective to decrease the pressure gradient across the valve by the water hammer phenomenon.

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In the January/1983 to March/1988, 1512 patients were submitted to valve replacement, 28 patients (1.85% ) for prosthetic valve endocarditis. Seventeen patients were males, their ages varying from 18 to 67 years old (36.7± 12.9). Eight patients (28.5%) were operated under emergent conditions. The blood cultures were positive in 14 (50%), the agent most commonly found being Streptococcus viridans in five cases. Hospital mortality was 28.5% (eight patients), one death occuring later. Mortality was significantly higher in the cases under emergent conditions, the cases in which the time from valve replacement to oncet of the endocarditis was less than one year, and the cases whose blood cultures were negative.

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Disc opening angle (OA) of OMNICARBON prosthetic valve at aortic position was measured cineradiographically in early postoperative, and long term periods. In early postoperative period, maximum opening angle (MOA) was 71.5±7.7°and incomplete disc opening under 60°(OA, 55.8±1.9°) was found by 13% and abnormal disc motion caused at 55.2±3.4°OA was observed by 730% Disc opening failure at same OA caused abnormal disc motion early postoperatively occured newly in long term period. MOA decreased significantly (P<0.0005) to 61.7±8.7°. These results suggest that a structural defect of OMNICARBON prosthetic valve may cause disc opening failure and abnormal disc motion.

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To evaluate in vivo performance of prosthetic valves in the aortic position, we measured intraoperative hemodynamic variables related to the valves and analyzed the valve function using a computer. After terminating cardiopulmonary bypass in 10 patients (7 Carpentier-Edwards bovine pericardial valves and 3 St. Jude Medical valves), left ventricular and ascending aortic pressures were measured by micromanometers and instantaneous ascending aortic flow was also measured by an electromagnetic flowmeter. Cycle length, mean pressure gradient, stroke volume and effective orifice area for each cardiac cycle were calculated using a computer. The change of the hemodynamics was induced by rapid atrial pacing or inflow occlusion. This computer analysis of each cardiac cycle enabled us to construct the prosthetic valve function curves which were useful for evaluating the performance under the changing hemodynamic conditions.

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Two cases of acute valve dysfunction after mitral and aortic replacement with the Bjork-Shiley monostrut type valve were experienced. ECG and arterial pressure monitor and echo-cardiography were available in the diagnosis. This complication is not a usual one, but it occurs, an urgent re-operation must be performed as soon as possible And two cases of chronic valve disfunction after mitral replacement with the Bjork-Shiley convexo-concave type valve were experienced. They were fracture of the minor strut of the Bjork-Shiley valve. The only way of survival is immediate judgment of the eituatian and subsequent urgent operation for the valve dysfunction.

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Retrospective follow-up data on 8 patients of prosthetic valve endocarditis (PVE) were reviewed over the last 9 years. 5 out of 8 patients underwent surgical management on their active phase. There was no early mortality (<30 day). However, long-term follow-up revealed that actuarial survival rate at 3 years of PVE (60.0%) was much lower than that of NVE (81.9%). Early initiation of surgical treatment was considered to be of primary importance, and eradicative procedure seemed necessary for prevention NVE from shifting to PVE.

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98 patients underwent valve replacement with Medtronic Hall valve (57 MVR, 23 AVR, 18 MVR+ AVR)from June, 1983 to March, 1988. We examined late results of those patients and the exercise tolerance in 29 cases.There were 8 operative deaths, of which the valve related death was one case of a stuck valve. The mean follow-up periods were 3.0 years(270 ptyrs).There were 8 cases of late deaths but no valve related death. The incidence of valve related complications was 1.5%/pt-ys:thromboembolism, 0.4%/pt-ys;PVE, 1.1%/pt-ys. Cardiac function were studied between well and poorly tolerant groups by exercise test. Postop.LVEDVI decreased to normal levels in both groups, but preop. EDVI was high in poorly group compared to well group (49.5±7.4, 33.0±11.5, p<0.005).

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