A Pivot Bearing-Supported Centrifugal Pump for a Long-Term Assist Heart

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 1 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 PI-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-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.

[Sweet's syndrome after off-pump coronary artery bypass grafting]

We report a 73-year-old man with myelodysplastic syndrome (MDS) who developed Sweet's disease after off-pump coronary artery bypass grafting (OPCAB). Coronary angiography showed severe 3 vessel disease. We conducted OPCAB on triple vessels using bilateral internal thoracic artery and saphenous vein grafts. He had a high fever and rubor around the median skin incision on 5 postoperative day. Skin biopsy demonstrated acute febrile neutrophilic dermatitis (Sweet's disease). The cutaneous lesions improved gradually by corticosteroids. A careful attention should be paid postoperatively in a patient with hematological disorders such as MDS, aplastic anemia, and malignancy.

[Aortic valve replacement through right anterolateral thoracotomy for aortic stenosis after mediastinal radiation therapy]

A 76-year-old woman had severe aortic stenosis on transthoracic echocardiography [aortic valve area (AVA): 0.7 cm2, max pressure gradient (PG): 108 mmHg]. Since she was on radiation therapy for breast cancer, we considered that median sternotomy was a risk factor for mediastinitis, and right thoracotomy was chosen for aortic valve replacement. The operation was performed through a right anterolateral thoracotomy. Cardiopulmonary bypass was established with right femoral artery cannulation, right atrial cannulation, and right superior pulmonary vein cannulation for venting. The patient's postoperative course was uneventful. This method appears to be an alternative approach for aortic valve replacement in patients that are not suitable candidates for median sternotomy.

Endovascular treatment of experimental cerebral aneurysms using thermoreversible liquid embolic agents

SUMMARY

We have developed a new embolic agent, thermoreversible gelation polymer (TGP). This polymer is unique in that solidification occurs at body temperature. The utility of this new liquid embolic agent for the treatment of large experimental aneurysms was evaluated angiographically. TGP remains liquid at temperatures below the sol-gel transition temperature (TT) and becomes gelatinous above the TT. TGP can also be used to slowly deliver biologically active substances such as growth factors or engineered cells. In this study, TGP was mixed with radiopaque material without solvent. Bilateral common carotid arteries of swine (n=5) were used for surgical creation of lateral aneurysms, then 1 aneurysm in each animal was embolized using TGP without any protection device. The remaining untreated aneurysm in each animal was used as a control. All aneurysms were successfully embolized using TGP. No distal migration of TGP was observed when aneurysms were embolized without using protection devices. TGP can be safely used to embolize experimental aneurysms. Embolization of aneurysms with a protection device needs to be evaluated. Further modifications such as mechanical stability and use as a drug delivery system will be necessary prior to the clinical application of TGP.

[Aortic root reconstruction in elderly patients]

Operative indications for aortic root reconstruction generally include aortic root aneurysm, root destruction in acute dissection, extensive annular abscess in infective endocarditis, and small aortic annuls. In elderly patients, Bentall operation with bioprosthesis should be one of the standard operation because bioprosthesis in aortic position demonstrated excellent long-term valve durability. Freestyle aortic bioprosthesis has been increasingly implanted as a full root replacement in elderly patients with small aortic annuls and carcified aortic root. When aortic valve is nearly normal, valve-sparing aortic root replacement can be an ideal operation without need for prosthetic valve. Indication for valve-sparing operation should be considered when the patient is physically and socially active and does not carry significant comorbidity.

[Novel strategy for thoracoabdomianl aortic aneurysm repair; intraoperative selective perfusion of the Adamkiewicz artery]

We report our method for delineating the Adamkiewicz artery using multidetector row computed tomography (MDCT) with selective perfusion using a distal perfusion cannula that is clinically available for off-pump coronary artery bypass (OPCAB). The tip of a distal perfusion catheter (Medtronic Quickflow, Minneapolis) designed for OPCAB was applicable for selective perfusion of the segmental arteries. The femoro-femoral venoarterial bypass was branched off into selective perfusion of the segmental arteries, using an independent roller pump and heat exchanger. Our method of visualization of the Adamkiewicz artery was MDCT scanning with injection of contrast medium directly into the proximal descending aorta: namely, "CT during aortography". Lower descending aorta to abdominal aorta (the range involving the aneurysm) was scanned in a cephalad-to-caudal direction using a detector collimation of 4 x 1.25 mm with a table speed of 9.4 mm/sec, pitch of 6, and image thickness of 1.25 mm. All images were reviewed on a workstation to investigate the continuity between the Adamkiewicz artery and its proximal segmental artery with paging, mulitplanar reformation and curved planar reformation. Distal perfusion cannulae of 2.0 mm in diameter were inserted into the respective intercostal arteries. 4-0 polyethylene sutures were placed to tourniquet the catheters. Segmental arteries were perfused with total flow of approximately 80 ml/min at a circuit pressure of 120 mmHg. Reattachment of the ninth intercostal arteries related to the Adamkiewicz artery was carried out. A total of 6 consecutive 6 patients with thoracoabdominal aortic aneurysm (TAAA) have undergone graft replacement by the methods described, since April 2002. All patients survived surgery without any neurological complications. This method is expected to minimize the ischemic time of the spinal cord and attenuate the reperfusion injury.

Angiogenesis after sintered bone implantation in rat parietal bone

We studied the effect of bone substitutes on revascularization and the restart of blood supply after sintered bone implantation in comparison with synthetic hydroxyapatite implantation and fresh autogenous bone transplantation (control) in rat parietal bones. Methods for the study included the microvascular corrosion cast method and immunohistochemical techniques were also used. The revascularization of the control group was the same as that for usual wound healing in the observations of the microvascular corrosion casts. The sintered bone implantation group was quite similar to that of the control group. In the synthetic hydroxyapatite group, immature newly-formed blood vessels existed even on the 21st day after implantation and the physiological process of angiogenesis was interrupted. Immunohistochemically, vascular endothelial growth factor (VEGF), which activates angiogenesis, appeared at the early stages of both the control group and the sintered bone implantation group. VEGF reduced parallel with the appearance of the transforming growth factor factor-beta-1 (TGF-beta-1), which obstructs angiogenesis, and the angiogenesis passed gradually into the mature stage. In the hydroxyapatite implantation group, TGF-beta-1 appeared at the early stage of the implants. The appearance of VEGF lagged and it existed around the pores of hydroxyapatite even on the 21st day of the implantation. Proliferation and wandering of endothelial cells continued without any maturing of the vessels. These findings suggest that the structure and the components of the implant material affect angiogenesis after implantation as well as new bone formation.

[Combined carotid endarterectomy and off-pump coronary artery bypass grafting]

Patients with angina undergoing carotid endarterectomy have a high mortality. A 74-yaer-old man who has severe carotid stenosis was performed combined carotid endarterectomy and off-pump coronary artery bypass grafting successfully. At first, carotid endarterectomy was performed with Jamieson's specially designed dissector, which allow simultaneous dissection and removal blood from the surgical field. Secondly, then off-pump CABG was performed. Skeletonized internal mammary artery was harvested with ultrasound dissector. The advantage of that the dissected artery is not only long and greater blood flow, but also less damage to sternal blood flow which prevent infection and complications. Then internal mammary artery was anastomosed to left anterior discending artery with Octopus II stabilizer. After the operation, he recovered uneventfully without neurological complication. Combined single staged carotid endarterectomy and off-pump CABG appears to be a safe method.

Leukocyte-depleted reperfusion after long cardioplegic arrest attenuates ischemia-reperfusion injury of the coronary endothelium and myocardium in rabbit hearts

OBJECTIVE

Cardiopulmonary bypass activates leukocytes, which should injure the coronary endothelium and myocardium during reperfusion especially after long cardioplegic arrest with long cardiopulmonary bypass time. The present study was designed to determine the protective efficacy of leukocyte-depleted reperfusion in blood-perfused parabiotic isolated rabbit hearts as a surgically relevant model with long cardioplegic arrest.

METHODS

Each isolated rabbit heart, with a latex balloon inserted in the left ventricle, was parabiotically blood-perfused using a modified Langendorff column. The left ventricular developed pressure (DP), rate of pressure development (dP/dT), and coronary flow with a left ventricular end-diastolic pressure of 10 mmHg were measured before ischemia and after 15, 30, 45, and 60 min reperfusion after 4 h cardioplegic arrest kept at 20 degrees C (control, n=10). Leukocyte-depleted reperfusion was done in the test group (n=10). The endothelium of the coronary artery was observed by scanning electron microscopy (SEM) with percent injured area of endothelial cells measured to evaluate the extent of endothelial ischemia-reperfusion injury.

RESULTS

The control hearts showed 53.3, 54.3, 48.4, and 39.0% recovery of DP compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began respectively. Leukocyte-depleted reperfusion enhanced the recovery of DP at 45 min (81.3%, P=0.0021) and 60 min (85.8%, P=0.0005) after reperfusion compared with that in the control group. The control hearts revealed 58.8%, 59.8%, 52.6%, and 43.4% recovery of dP/dT compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began, respectively. Leukocyte-depleted reperfusion also enhanced the recovery of dP/dT at 45 min (93.2%, P=0.0071) and 60 min (98.8%, P=0.0011) after reperfusion compared with that in the control group. There was also improvement of the recovery of coronary flow by leukocyte-depleted reperfusion (97.2%) compared with that in the control group (58.3%) after 60 min reperfusion (P=0.0121). Scanning electron microscopy showed that 69. 7% of coronary endothelial cells were morphologically injured in the control group. In contrast, leukocyte-depleted reperfusion prevented the extent of coronary endothelial damage with less injured area (0. 5%, P=0.0002).

CONCLUSIONS

Leukocyte-depleted reperfusion improved functional recovery with reduced coronary endothelial injury after long cardioplegic arrest.

Successful valve-sparing in aortic root reconstruction under endoscopic guidance

OBJECTIVE

Aortic insufficiency (AI) associated with ascending aneurysm can be corrected by valve-sparing aortic root reconstruction ('David' reimplantation, 'Yacoub' remodeling). Intraoperative endoscopic evaluation in the aortic root may help to clarify the procedure and to access competence of the preserved valve.

METHODS

Following cross-clamping of the ascending aorta, an endoscopy was inserted into the proximal aortic root. Perfusion of crystalloid cardioplegia enabled the visualization of the pressure-loaded valve in the closed position. Conventional macroscopic evaluation would have overlooked valve prolapse because of a release from perfusion pressure. Valve coaptation was imaged directly before and after the valve-sparing procedure. A total of 17 patients underwent aortic root reconstruction under endoscopic guidance. Indications of the valve-sparing were determined with endoscopic findings. The degree of AI before and after the surgery was evaluated by aortography and scored (0, none; 1 trivial; 2, mild; 3, moderate; 4, severe).

RESULTS

Remodeling was employed to eight patients and reimplantation to four. The other five patients were replaced with prosthetic valved-conduit. There was no early and late mortality. Before and after the valve-sparing surgery, grades of AI were significantly reduced. Three patients who underwent reimplantation procedure required late valve replacement for late progression of AI, however, none of the patients with remodeling required reoperation.

CONCLUSION

Introduction of an endoscopy successfully reduced postoperative AI and clarified indications and limitations of valve-sparing aortic root operations.

[Influence of acute aortic dissection on long-term results of aortic root reconstruction in patients with Marfan's syndrome]

Objective of this study is to evaluate influence of acute aortic dissection on long-term results of aortic root reconstruction in patients with Marfan's syndrome. 19 patients who underwent consecutive aortic root reconstruction between 1985 May to 1998 February were retrospectively reviewed. Patients who associated acute aortic dissection at the time of operation (group D, n = 7) were compared long-term results with those who did not (group non-D, n = 12). Mean follow-up period was 5.1 +/- 3.2 years and longest follow-up term was 12.5 years. In each group early postoperative death was found in one patient. In-hospital mortality in each group were respectively; 14.2% and 8.3%. Late deaths were found in four patients who all belonged to group D, respectively caused by; rupture of thoracoabdominal aneurysm, DIC after subsequent thoracoabdominal surgery, sepsis due to prosthetic valve endocarditis, and sudden death. Actuarial overall survival rate including operative death in D and non-D group were respectively; 0.0 +/- 0% at 6.6 years and 91.1 +/- 8.0% at 12 years. Overall cumulative survival rate was 56.6 +/- 14.0%. Freedom from cardiovascular events, in D and non-D group were respectively; 0.0 +/- 0% at 6.6 years and 60.0 +/- 25.3%, and freedom free form dilatation of residual aorta were respectively; 0.0 +/- 0% at 6.6 years and 100.0 +/- 0% at 12 years. Freedom from subsequent cardiovascular surgery in group D, group non-D and over-all patients were respectively; 0.0 +/- 0% at 6.6 years, 60.0 +/- 25.3% at 12 years and 42.6 +/- 20.2%. In this study, acute aortic dissection in Marfan's syndrome significantly increased late cardiovascular events including dilatation of residual aorta, subsequent aortic surgery and late mortality. On the other hand, excellent long-term results after aortic root reconstruction were found in non-dissection Marfan's syndrome. Considering high incidence of late dilatation of residual aorta, simultaneous total arch replacement with aortic root reconstruction is recommended in acute dissecting Marfan's syndrome. Whereas, preventive simultaneous arch replacement is not required in non-dissecting Marfan's syndrome because of less postoperative vascular events.

[A case of fulminant myocarditis treated by ABIOMED BVS 5000 biventricular support]

Reported is a case of acute fulminant myocarditis with profound circulatory compromise. The patient was supported with biventricular assist devices (BVS 5000 ; ABIOMED Inc., Danvers, Mass.). The patient had remarkable recovery of ventricular function, which allowed for the removal of the device after 269 hours of support and the recovery to the normal quality of life. This case shows the success of mechanical support to treat potentially fatal disease process.

[Initial clinical experiences of the ABIOMED BVS SYSTEM 5000 in Japan]

The initial clinical experience of the ABIOMED BVS SYSTEM 5000 in Japan is reported. The system is a paracorporeal pulsatile assist device intended for temporary ventricular support. It consists of a pneumatic drive console, a blood pump, and the atrial and arterial cannulas. The pump is of a dual chamber design, with the upper chamber as a passive, gravity filled resevoir and the lower chamber as a pumping chamber. Since the system is designed to be simple, safe and automatically controlled, no additional personnel is required to control perfusion. This report describes our initial clinical experiences with the ABIOMED BVS SYSTEM 5000 in Japan. This device was used in three patients with post cardiotomy cardiogenic shock and fulminant myocarditis. The first patient developed acute occlusion of left main coronary artery who required emergent surgical revascularization following PTCA and stent implantation. He couldn't wean from CPB and required the insertion of an LVAD. The second case suffered from a cardiac arrest after CABG and could not be resuscitated. The ABIOMED BVS 5000 was inserted and the patient successfully weaned from support. The third patient developed fulminant myocarditis and was supported with the system for 269 hours and was successfully weaned after near complete myocardial recovery. Our initial experience with the ABIOMED BVS SYSTEM 5000 indicates that the system can provide complete cardiac support allowing full recovery from a cardiac variety of causes of dysfunction. The device has the potential to improve the survival rate of patients with severe acute recoverable myocardial damage. It is expected that this device can be a viable tool for treatment of intractable heart diseases.

[Reoperation after aortic valve replacement and root reconstruction]

Between 1984 and 1997, 127 patients in our institution underwent single aortic valve replacement (AVR) with the St. Jude Medical valve (group S) and 11 patients with a porcine pericardial valve (group T). In the same period, 45 patients underwent aortic root reconstruction, among which 39 patients underwent the Bentall procedure using Carrel patch coronary reanastomosis (group B). The other 6 patients were treated with valve-sparing aortic root reconstruction (group V), among which the reimplantation method was used in 4 patients and the remodeling method in 2. The mean and total follow-up periods of the AVR and aortic root reconstruction groups were 6.9 +/- 1.9 year/735 patient-years and 4.9 +/- 3.9/years/196 patient-years respectively. The actuarial overall survival rates in group S and T at 10 years were; 73.8 +/- 7.0% and 85.7 +/- 13.0%, respectively The probabilities of freedom from reoperation at 12 years in group S and T were 97.7 +/- 2.3% and 62.5 +/- 21.3%, respectively. Only one patient in group S required reoperation because of valve thrombosis, while 2 patients in group T underwent reoperation for prosthetic valve endocarditis. The actuarial overall survival rate after aortic root reconstruction at 10 years was 62.6 +/- 9.6%, while that of patients with acute aortic dissection and those who did not were 44.4 +/- 15.7% and 71.7 +/- 11.5%, respectively. The event-free rate at 12 years after aortic root reconstruction (group V+B) was 79.1% +/- 20/9%. The reason for reoperation in the 2 patients who underwent the Bentall procedure were prosthetic valve endocarditis in one and psuedoaneurysm at the right coronary anastomosis in the other. The reason for reoperation in one patient who formed a pseudoaneurysm was likely due to an oversized conduit hole for the Carrel patch coronary anastomosis. One patient in whom the native valve was preserved using the David reimplantation procedure required reoperation because of valve degeneration 17 months after the initial surgery, possibly due to valve rubbing on the vascular conduit because of a modified geometry of the Valsalva sinuses. In conclusion, because of the low rate of long-term mortality and reoperation, the St. Jude Medical valve is an excellent prosthesis for AVR. AVR with a porcine pericardial valve yields favorable results in terms of the low long-term mortality although the incidence of reoperation remains high. Aortic root reconstruction with the Bentall procedure using the Carrel patch method yields acceptable results in terms of long-term mortality and low rate of reoperation, although acute aortic dissection is an incremental preoperative risk factor. The early results of aortic valve-sparing root reconstructive surgery are encouraging, with excellent clinical outcomes and patient quality of life. Nevertheless, the indications for the procedure must be carefully considered.

Initial experience with the Nikkiso centrifugal pump during thoracoabdominal aortic aneurysm repair

PURPOSE

Several centers use atriodistal bypass (ADB) as a protective adjunct against distal ischemia during extensive thoracoabdominal aortic aneurysm (TAAA) repair. Most current ADB circuits use indirect-drive centrifugal pumps. The purpose of this report is to describe our initial clinical experience with the Nikkiso pump, a more compact direct-drive centrifugal pump recently developed at Baylor, for ADB during TAAA repair.

METHODS

The Nikkiso pump was used for ADB perfusion in 10 consecutive patients during graft repair of TAAAs (six Crawford extent I and four extent II). Two patients had aortic dissection. In the four patients who had extent II repairs, selective renal and visceral perfusion was also performed with the Nikkiso pump.

RESULTS

No mechanical pump malfunctions or adverse events related to the device occurred. All 10 patients survived and were discharged from the hospital. No patient had paraplegia after surgery. Two patients had delayed lower extremity weakness after undergoing extent I repairs; both recovered and were ambulating at the time of discharge. No complications were associated with bleeding or cerebral, respiratory, renal, or hepatic function.

CONCLUSIONS

Our initial experience with the Nikkiso centrifugal pump during TAAA repair demonstrated excellent pump function that provided sufficient flow for both distal aortic and selective organ perfusion. The prevention of permanent spinal cord injury and distal organ failure was successful in this group.

Recent advances in the gyro centrifugal ventricular assist device

The gyro pump was developed as an intermediate-term assist pump (C1E3) as well as a long-term centrifugal ventricular assist device (VAD). The antithrombogenic design concept of this pump was confirmed throughout three 1 month ex vivo studies. The normalized index of hemolysis (NIH) of this gyro C1E3 model was lower than that of the BP-80. In the next step, a miniaturized centrifugal blood pump (The Gyro permanently implantable model PI-601) has been developed for use as a permanently implantable device after design optimization. A special motor design of the magnet circuit 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, 65 mm in diameter, 145 ml of displacement volume, and 305 g in weight. This pump can provide 5 L/min against 120 mm Hg total pressure head at 2,000 rpm. The NIH value of this pump was comparable to that of the BP-80. The gyro PI-601 model is suitable for a VAD. The expected life from the endurance study is approximately 8 years. The evolution from C1E3 to the PI-601 converts this pump to a totally implantable centrifugal pump. Recent technologic advances in continuous flow devices are likely to realize a miniaturized and economical totally implantable VAD.

The simple in vitro thrombogenic test: modified methods for same priming pumps

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 ml, without pump) were constructed and tested with the same priming volume of Nikkiso centrifugal pumps, noncoated verus heparin-coated. Two pumps were run simultaneously using the same source of fresh heparinized human blood (activated clotting time [ACT] 150-250 s) 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.

Reconsideration of total erythrocyte destruction phenomenon

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 O2 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.

Development and initial testing of a permanently implantable centrifugal pump

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 Hg 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 Hg. 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.

The hemolysis test of the Gyro C1E3 pump in pulsatile mode

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 a 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 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 two different impeller speed (the lower 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 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 mode advantages.

Therapeutic and physiological artificial heart: future prospects

Current left ventricular assist devices (LVADs) have demonstrated admirable results. However, approximately one-fourth of the patients who require LVADs suffer from right heart failure and require additional right ventricular (RV) assist devices (RVADs). The RV failure impairs the splanchnic circulation, subsequently developing into multiorgan failure (MOF). An aggressive application of a biventricular assist device (BVAD) is the best way to avoid and treat MOF because the BVAD reduces splanchnic congestion. Also, because the BVAD allows retention of the natural heart, recovery of the heart function can be expected after long-term assist. This benefit cannot be expected from conventional total artificial hearts. Although there are no implantable clinical BVAD systems in existence today, present advanced technologies in rotary blood pumps can enable these systems to be totally implantable. So, we should focus on developing a totally implantable BVAD system. The implantable BVAD will be a therapeutic and physiological total artificial heart, and it will be a common home health care device in the near future.

In vitro thrombogenic evaluation of centrifugal pumps

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.

A pivot bearing-supported centrifugal pump for a long-term assist heart

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 1 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 P1-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-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.

Improved flow straighteners reduce thrombus in the NASA/DeBakey axial flow ventricular assist device

A small axial flow ventricular assist device (VAD) measuring 3 inches long and 1 inch in diameter is in development. The pump consists of a spinning inducer/ impeller, a flow straightener (FLS), and a diffuser enclosed in a cylindrical flow tube. The impeller has rod-shaped permanent magnets embedded within its 6 blades and is activated magnetically by the motor stator which is positioned outside the flow tube. At the completion of a previous study, the FLS was identified as a thrombogenic area. The aim of the present study was to evaluate the thrombogenicity of redesigned FLSs (swept-back and bulbous types), compared with standard type (STD) FLS. A total of 15 pumps (STD, n = 7; swept-back, n = 4; and bulbous, n = 4) were sequentially implanted into 4 calves paracorporeally in a short-term ex vivo test. The STD and bulbous FLSs experienced thrombus formation, but the swept-back FLS was thrombus free during a 48 h screening test.

Development of a pivot bearing supported sealless centrifugal pump for ventricular assist

Since 1991, in our laboratory, a pivot bearing-supported, sealless, centrifugal pump has been developed as an implantable ventricular assist device (VAD). For this application, the configuration of the total pump system should be relatively small. The C1E3 pump developed for this purpose was anatomically compatible with the small-sized patient population. To evaluate antithrombogenicity, ex vivo 2-week screening studies were conducted instead of studies involving an intracorporeally implanted VADs using calves. Five paracorporeal LVAD studies were performed using calves for longer than 2 weeks. The activated clotting time (ACT) was maintained at approximately 250 s using heparin. All of the devices demonstrated trouble-free performances over 2 weeks. Among these 5 studies, 3 implantations were subjected to 1-month system validation studies. There were no device-induced thrombus formations inside the pump housing, and plasma-free hemoglobin levels in calves were within the normal range throughout the experiment (35, 34, and 31 days). There were no incidents of system malfunction. Subsequently, the mass production model was fabricated and yielded a normalized index of hemolysis of 0.0014, which was comparable to that of clinically available pumps. The wear life of the impeller bearings was estimated at longer than 8 years. In the next series of in vivo studies, an implantable model of the C1E3 pump will be fabricated for longer term implantation. The pump-actuator will be implanted inside the body; thus the design calls for substituting plastic for metallic parts.

Comparison of centrifugal and roller pump hemolysis rates at low flow

We compared in vitro rates of hemolysis for a recently developed centrifugal pump with a conventional roller pump (10-10-00; Stöckert, Munich, Germany). Flow rates of 0.3 L/min and 1 L/min and a pressure of 200 mm Hg were chosen to simulate conditions during neonatal extracorporeal membrane oxygenation (ECMO). There was no significant difference in hemolysis rates between centrifugal and roller pumps (p = 0.57) nor between high and low flow (p = 0.86). The centrifugal pump caused no more blood trauma than the roller pump at the low-flow/high-pressure conditions required for neonatal ECMO. The Nikkiso pump is superior to roller pumps in size and priming volume (25 ml) and may permit development of a smaller and simpler ECMO system.

Clinical comparative study of cardiopulmonary bypass with Nikkiso and BioMedicus centrifugal pumps

The Nikkiso centrifugal pump was evaluated in elective adult open heart surgery in comparison with the BioMedicus pump. Ten patients using the Nikkiso pump (Group N), and 10 patients using the BioMedicus pump (Group B) were examined for (or to determine) hematobiologic parameters and patient outcome data as well as pump controllability. During cardiopulmonary bypass (CPB), both pumps maintained systemic perfusion satisfactorily without any mechanical adverse event. Rotation speed of the Nikkiso centrifugal pump (3,580 +/- 100 rpm) was significantly higher than that of the BioMedicus pump (3,170 +/- 100 rpm; p < 0.05) whereas changes in free plasma hemoglobin, platelet count, blood urea nitrogen, and creatinine levels showed no significant differences between the two groups. Urine output in Group N for 20 min after the initiation of CPB (7.10 +/- 1.50 ml/kg/h) was significantly higher than that in Group B (3.23 +/- 0.46 ml/kg/h; p < 0.05). Patient outcome data were similar in both groups, such as duration of intensive care unit stay, hospital stay, postoperative intubation time, amount of postoperative bleeding, and amount of blood transfused. These equivalent results with the BioMedicus pump suggested that the Nikkiso pump can be used in open heart surgery as a reliable and atraumatic CPB pump.

Morphological changes of autoclaved autogenic bone implantation and autoclaved autogenic bone supplemented with allogenic demineralized bone matrix in rat parietal bone

The healing process of resected, autoclaved (121 degrees C, 20 minutes) and re-implanted bone in the rat parietal bone was compared with that of autoclaved bone that was supplemented with allogenic bone matrix (AAA-bone), using a scanning electron microscope and a light microscope. In the implant without AAA-bone, bone union and replacement of the autoclaved bone was seen at 2 weeks after implantation. There was no evidence of any inflammatory reaction around the autoclaved bone. The implant was gradually replaced by the new bone. In the implant with AAA-bone, the new bone formation around the implanted bone was more abundant than that of the implant without AAA-bone. An inflammatory reaction was also observed after 1 week. The replacement of the implant with AAA-bone was inferior to the nonsupplemented group. The reason for the poor replacement was the disturbance of the blood supply in the implant by abundant new bone formation. In these results, the autoclaved bone re-implantation was an excellent bone substitute with osteoconductive ability and biocompatibility. The implantation with AAA-bone was good for the new bone formation, but the position and the technique of supplement with AAA-bone have to be more deeply investigated.

Initial clinical experience with the Baylor-Nikkiso centrifugal pump

Recently, a newly developed centrifugal pump, the Baylor-Nikkiso pump, was approved for clinical use in the United States. This pump is the most compact centrifugal pump with a priming volume of only 25 ml. Although it is small, this pump can provide a flow of 4 L/min against a total pressure head of 300 mm Hg at 3,000 rpm. In vitro and in vivo validation of the Baylor-Nikkiso pump has proved that this pump could effectively reduce blood trauma even under high total head pressure. In addition, 48-h durability tests with biventricular bypass using calves verified the reliability of shaft sealing and antithrombogenicity. Clinical trials of the Baylor-Nikkiso pumps have been initiated in our department. This pump provides flows of 60-70 ml/kg/min with stable hemodynamic conditions. No leakage of thrombus formation was observed. The results of the initial clinical experience of the Baylor-Nikkiso pump suggest that it is suitable for cardiopulmonary bypass surgery.

Scanning electron and light microscopic observations on the healing process after sintered bone implantation in rats

The healing process after implantation of sintered bone in the rat parietal bone was compared with that of synthetic hydroxyapatite using both scanning electron and light microscopy. The results showed that the differences between the sintered natural bone and the synthetic hydroxyapatite implantations were in the states of bone union and the bioresorbability of the implanted materials, even though both materials consist of the same hydroxyapatite. In the sintered bone implantation, the newly formed bone invaded into the material at 1 to 2 weeks after implantation. The sintered bone surface on the dura mater side was completely covered by the new bone at 5 weeks. It is noteworthy that bone resorbing areas characterized by Howship's lacunae were observed on the sintered bone surface at 2 weeks and the material was replaced by new bone. Light microscopy, which revealed the invasion and the development of the new bone into the sintered bone, supported the scanning electron microscopic observations. In the synthetic hydroxyapatite, the new bone adhered closely to the material just like the sintered bone implantation. The new bone did not invade into the synthetic hydroxyapatite. There was no evidence of the resorption of the hydroxyapatite. This shows that the natural and the biological structures of the sintered bone offer an advantageous environment to fluid circulation and ingrowth after implantation.

[Congenital isolated tricuspid insufficiency in an elderly woman]

Isolated congenital tricuspid insufficiency due to primary malformation of the tricuspid valve is rare. The patient was a 70-years-old woman complaining of exertional dyspnea. Cardiac echo-sonography and catheterization showed severe TR with no other cardiac abnormality. At surgery, the anterior leaflet of the tricuspid valve was hypoplastic and attached to the right ventricle with shortened chorda. Tricuspid valve replacement was successfully performed with a 31 mm Carpentier-Edwards pericardial valve. The postoperative clinical course was smooth. This is the oldest known reported case of a successful operation for congenital tricuspid insufficiency.

[A case of acute postinfarction mitral regurgitation and cardiogenic shock caused by a total rupture of the papillary muscle]

We report a case of mitral regurgitation caused by a total rupture of the posterior papillary muscle that had occurred after acute myocardial infarction. A 72-year-old woman was transferred to our hospital for cardiogenic shock. Echocardiogram revealed massive mitral regurgitation and prolapse of posterior mitral leaflet presumably due to a rupture of a papillary muscle. Cardiac catheterization demonstrated a total occlusion in the segment 2 of the right coronary artery. She had developed progressively increasing heart failure even though the patient had received a successful PTCA for a total occlusion of the right coronary artery. She underwent an emergency mitral valve replacement with preservation of the posterior leaflet using a SJM prosthetic valve. Intraoperative findings were confirmative of total rupture of the posterior papillary muscle. A postoperative course was uneventful. This case is the seventh case which has been reported as the successful operation of a total rupture of the papillary muscle in Japan.

[Syphilitic coronary ostial obstruction and aortic regurgitation associated with advanced gastric cancer: successful 2-stage surgery]

We report a case of syphilitic coronary ostial obstruction and aortic regurgitation associated with advanced gastric cancer for which subtotal curative gastrectomy and AVR with CABG was successfully performed in a two-stage operation. A 65-year-old male was admitted complaining of tarry stool and angina. A serological test for syphilis was strongly positive and angiography demonstrated a left coronary ostial obstruction accompanied by moderate aortic regurgitation. An endoscopic examination of the stomach revealed a Borrmann type II advanced gastric cancer with active bleeding. In the first stage, a subtotal gastrectomy with wide margin was performed, under hemodynamic monitoring because of the active tumoral bleeding. After the second-stage AVR, the postoperative course was uneventful.

Comparison of acetate utilization among strains of an aceticlastic methanogen, Methanothrix soehngenii

The kinetics of acetate utilization by concentrated suspensions of cells was examined in five strains of Methanothrix soehngenii. The rate of acetate utilization by all strains was dependent on the initial acetate concentration and followed simple Michaelis-Menten kinetics. The ability to utilize acetate differed among the various strains of M. soehngenii and was highest in the strain designated MTAS.

[Marfan's syndrome with annulo-aortic ectasia and ruptured mitral chorda--a case report of combined composite valve graft replacement of the aortic root and mitral valve replacement]

We report a case of Marfan's syndrome with acute heart failure caused by a ruptured mitral chorda that was successfully treated by one operation of combined composite valve graft replacement of aortic root and mitral valve replacement (MVR). A 23-year-old man was admitted to our hospital presenting severe dyspnea and chest pain. Echocardiography and cardiac catheterization studies demonstrated marked annulo-aortic ectasia, aortic regurgitation and significant mitral regurgitation due to a ruptured chorda. In operation, it was found that a chorda of the mitral posterior leaflet had been torn, with the leaflet completely prolapsed to the left atrium, and that the aortic root was dilated to 90 mm in diameter. The ascending aorta was extensively resected leaving those areas of aortic tissue involving the coronary ostia. Then the mobilized coronary arteries were reattached to the composite graft. MVR was performed with preservation of the whole anterior and posterior mitral valve apparatus except for that small part with the torn chorda. Histopathological findings of the aortic wall and mitral valve were compatible with those of Marfan's syndrome.

Aortic regurgitation and aneurysm of Sinus of Valsalva associated with osteogenesis imperfecta

A case of osteogenesis imperfecta with aortic regurgitation is described. The patient had a dilated aortic valve ring and an aneurysm of the Sinus of Valsalva. The patient manifested severe hemodynamic abnormalities and underwent aortic root reconstruction using a valved conduit. The operative problems and the pathological findings are discussed.

Germanium myopathy: clinical and experimental pathological studies

Pathological examinations were carried out on the skeletal muscle of a patient with germanium intoxication. The prominent histochemical finding was vacuolar myopathy with lipid excess, increased acid phosphatase activity and decreased cytochrome c oxidase activity. Ultrastructural lesions revealed a mitochondrial abnormality, autophagic vacuoles and accumulation of high electron-dense materials in deformed mitochondria and at the periphery of lipid droplets. Furthermore, the toxic effect of germanium on skeletal muscle was confirmed by the experimentally induced germanium myopathy, which showed autophagic degeneration, decreased cytochrome c oxidase activity and a mitochondrial abnormality with high electron-dense materials.

Primary structure of limulus anticoagulant anti-lipopolysaccharide factor

A potent anticoagulant, anti-lipopolysaccharide (LPS) factor, found in limulus hemocytes inhibits the LPS-mediated activation of limulus coagulation cascade and shows an antibacterial action against R-types of Gram-negative bacteria (Morita, T., Ohtsubo, S., Nakamura, T., Tanaka, S., Iwanaga, S., Ohashi, K., and Niwa, M. (1985) J. Biochem. (Tokyo) 97, 1611-1620). The complete amino acid sequence of this substance was determined by sequencing the peptides obtained by selective proteolytic cleavage. The NH2-terminal end of anti-LPS factor was pyroglutamic acid. Anti-LPS factor had two variant residues at position 36 and the COOH-terminal end, respectively. The following sequence was assigned to anti-LPS factor, and it was also confirmed by fast atom bombardment mass spectrometry. less than EGGIWTQLALALVKNLATLWQSGDFQFLGHE (formula; see text) Limulus anti-LPS factor consisted of a single chain of 102 residues with 2 half-cystines in disulfide linkage. Its NH2-terminal region up to 20 residues was highly hydrophobic, and positively charged residues were clustered mainly within the disulfide loop. By searching the homologous sequence in known protein sequences with that of anti-LPS factor, we found a structural homology between anti-LPS factor and alpha-lactalbumin/lysozyme family.

Isolation and biological activities of limulus anticoagulant (anti-LPS factor) which interacts with lipopolysaccharide (LPS)

Exposure of limulus hemocytes to bacterial endotoxins (lipopolysaccharide, LPS) results in the activation of the intracellular clotting system, consisting of several protein components. During the separation of these components, a potent anticoagulant, named anti-LPS factor, which inhibits the endotoxin-mediated activation of the coagulation cascade, was found in hemocytes from both Tachypleus tridentatus and Limulus polyphemus (Tanaka, S., et al. (1982) Biochem. Biophys. Res. Commun. 105, 717-723). The principle isolated from the Tachypleus hemocyte lysate by column chromatographies on dextran sulfate-Sepharose CL-6B and Sephadex G-50 under sterile conditions was a simple basic protein with an apparent molecular weight of 15,000. It consisted of a single chain polypeptide containing a total of 128 amino acids. The COOH-terminal end was presumed to be histidine, but no NH2-terminal end reactive to phenylisothiocyanate was detected. The isolated anti-LPS factor specifically inhibited the endotoxin-mediated activation of factor C, which has recently been identified as an LPS-sensitive serine protease zymogen in the hemocytes. This inhibition appeared to be due to the binding of anti-LPS factor with LPS. Moreover, anti-LPS factor had an antibacterial effect on the growth of Gram-negative bacteria (Salmonella minnesota R595 and 1114W) but not on that of Gram-positive bacteria (Staphylococcus aureus 209P). These biological activities of the isolated anti-LPS factor suggest an important role in cellular defence of limulus against microbial invasion.