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.

[Treatment of a massive tracheal bleeding with percutaneous cardiopulmonary support]

A 69-year-old woman was admitted to our hospital with heart failure. Echocardiography demonstrated severe mitral valve regurgitation due to chordae rupture of the posterior mitral leaflet. Although she was intubated and ventilation was initiated, her condition did not improve. On the 17th hospital day, she was scheduled to undergo mitral valve plasty. After induction of anesthesia, massive bleeding occurred from the tracheal granuloma (diameter, 3 cm), which had developed at the tip of the tracheal tube, and the airway was obstructed. Emergency percutaneous cardiopulmonary support (PCPS) was then introduced. Thereafter, endoscopic hemostasis was performed, followed by the excision of the granulation tissue using a gastric fiberscope. After excising the tissue, the patient could be ventilated; therefore, she was weaned from PCPS. The maximum PCPS flow was 4.0 l/min, and it was conducted for a 210-minutes duration. Her respiratory condition improved, and she was weaned from the ventilator 3 days after surgery. Mitral valve plasty was performed 55 days after the first operation, and she was discharged from the hospital in good health.

[Reoperation due to failure of a Freestyle bioprosthesis]

We report re-do aortic valve and ascending aorta replacements by using the valve-on-valve technique for primary tissue failure of a Freestyle bioprosthesis. A 74-year-old male, who had had a 25 mm Freestyle bioprosthetic valve implanted by the sub-coronary method 5 years previously for aortic valve regurgitation due to congenital bicuspid valve, was referred to our hospital for dyspnea and palpitation. He presented with heart failure secondary to aortic regurgitation due to primary tissue failure, and computed tomography demonstrated an enlarged ascending aorta (5 cm in diameter). The operative findings revealed that the Freestyle bioprosthetic valve had a leaflet tear at the left coronary cusp. We replaced the degenerated Freestyle bioprosthesis with a 19 mm Mosaic aortic bioprosthesis by using the valve-on-valve technique, and ascending aorta replacement was performed simultaneously. This technique can be useful for re-do surgery for degenerated stentless valves to avoid potential risks of complete excision of the bioprosthesis.

[Unruptured aneurysm of the sinus of Valsalva associated with right ventricular outflow tract stenosis; report of a case]

A 51-year-old female was referred to our hospital for heart murmur and was diagnosed with right ventricular outflow stenosis by echocardiography. Six years later, follow-up echocardiogram revealed that the stenosis was caused by an aneurysm of the sinus of Valsalva (2 cm in diameter) originated from the right coronary sinus. Resection and patch closure of the aneurysm were carried out under complete cardiopulmonary bypass. The aneurysm was not associated with ventricular septal defect and was categorized as Sakakibara-Konno type I. Postoperative state was uneventful. Systolic murmur disappeared and pressure difference in the right ventricular outflow was normalized.

[Hemolysis after ascending and arch replacement of the aorta; report of a case]

A 60-year old man presented with hemolytic anemia, heart failure, and renal dysfunction 4 years after ascending and total arch replacement for Stanford type A aortic dissection. The hemolysis was caused by graft compression by a pseudoaneurysm arising from a proximal anastomosis. Reoperation of resection of pseudoaneurysm and repair of ascending aorta and arch successfully resolved these problems.

[Left circumflex coronary aneurysm with separated left main trunk]

We report a left circumflex coronary aneurysm associated with separated left main coronary trunks (LMT). A 66-year-old man was admitted to our hospital for further examination of dyspnea on effort. He has been performed maintenance hemodialysis since 1999 for chronic renal failure. Coronary angiography and multislice spiral computed tomography (CT) revealed an unusual coronary anatomic variance in which separate origins of the left anterior descending (LAD) and left circumflex (LCx) coronary arteries arose from the left coronary aortic sinus. Furthermore, these images of the LCx revealed an aneurysm 2 cm in diameter and 99% stenosis at the proximal of side of the aneurysm. Under cardioplegic arrest, the aneurysm was ligated and coronary artery bypass grafting (left thoracic artery to posterolateral branch) was performed. The patient was discharged at the 20th postoperative day without any complication.

[Acute aortic regurgitation by spontaneous rupture of a fibrous strand in fenestrated aortic valve; report of a case]

Although fenestration of the aortic valve cusps is a common anatomic finding, it rarely causes aortic regurgitation. We describe acute aortic regurgitation by spontaneous rupture of a fibrous strand in fenestrated aortic valve. A 65-year-old man was referred with sudden onset of dyspnea and cough. He diagnosed acute heart failure due to severe aortic valve regurgitation. After medical therapy, the aortic valve replacement was performed. Operative findings reviewed that a fibrous strand in the fenestrated non-coronary cusp was ruptured, which caused severe aortic regurgitation. Pathological examination showed the myxomatous degeneration. The postoperative course was uneventful, and the patient was discharged on postoperative day 11 with good health.

[Effects of intra-coronary and intra-graft administration of nicorandil for coronary spasm after coronary artery bypass grafting]

Coronary artery spasm after coronary artery bypass grafting (CABG) is relatively rare, but when it occurs, it is fatal. In cases of circulatory collapse just after surgery, coronary spasm should be suspected, and immediate diagnosis by coronary angiography is necessary. We conducted a study to assess the clinical characteristics of coronary spasm after CABG and the usefulness of intra-coronary and intra-graft administration of nicorandil. Study subjects were 7 patients (6 men and 1 woman, mean age 60.4 years) in whom coronary spasm after CABG was diagnosed angiographically from January 1992 to December 2003. Off-pump CABG (OPCAB) had been performed in 2 patients. Despite continuous administration of nitroglycerin and diltiazem hydrochloride during surgery, sudden circulatory collapse occurred during surgery or within 24 hours after CABG in all 7 patients. All required mechanical circulatory support, and emergency coronary angiography revealed severe graft and native coronary spasms. Intracoronary and/or intra-graft administration of diltiazem hydrochloride or nitroglycerin was not very effective, however, administration of nicorandil was effective for vasodilatation. One patient suffered brain damage and died, but the other 6 patients recovered and were discharged without complication. In conclusion, intra-coronary and/or intra-graft administration of nicorandil appears to be useful for the treatment of coronary spasm after CABG.

[Papillary fibroelastoma of the right atrium; report of a case]

Papillary fibroelastoma is a rare benign tumor commonly arising from a heart valve. We describe an unusual papillary fibroelastoma that arose from the right side of the interatrial septum. An intracardiac tumor was discovered by routine echocardiography in an asymptomatic 68-year-old woman. The echocardiographic examination revealed a 20 mm mobile tumor in the right atrium. Tricuspid obstruction was not observed, nor was regurgitation. The tumor was resected through a right atriotomy. It had multiple papillary fronds and arose from the interatrial septum. Pathologic examination confirmed papillary fibroelastoma. The postoperative course was uneventful, and the patient was discharged on postoperative day 13.

[Repair of thoracic and thoracoabdominal aortic aneurisms by the use of hypothermic circulatory arrest]

From 1993 to 2003, repair of thoracic and thoracoabdominal aortic aneurysms using hypothermic circulatory arrest via the left thoracotomy was performed in 115 patients at our hospital. Ninety-one of them were elective cases and 24 of them were emergent cases. Hospital mortality rate was 3.3% in elective cases and 12.5% in emergent cases. Over all hospital mortality rate was 5.2%. Ischemic spinal cord injury was occurred in 2 patients (1.7%). Both of them needed total replacement of thoracoabodominal aorta by the graft. In the near future, Adamkiewicz artery may be detected by the imaging technology preoperatively and we expect the repair of thoracoabdominal aortic aneurysm may become safer operation avoiding spinal cord injury. Hypothermic circulatory arrest is a relatively safe and reliable method for the repair of thoracic and thoracoabdominal aortic aneurysms.

[Prognosis and percentage of employment after the surgery in Marfan syndrome]

The percentage of employment in the Marfan patient after the Bentall procedure was studied. Eighteen of 20 patients (90%) returned to their daily life and are working well after the surgery. Seven patients (35%) needed the second operation due to the enlargement of false lumen during the follow-up period. Fatal cardiovascular accidents occurred in 7 their families (35%) in our series. Careful follow-up, adequate selection of medical and surgical treatment including second operation, medical examination of their families are important to keep the good quality of life in the Marfan patient.

[Long-term surgical outcomes of aortic arch aneurysm]

Between January 1990 and October 2001, arch replacement was performed in 99 patients with aortic arch aneurysm at Omiya Medical Center. For brain protection during surgery, antegrade selective cerebral perfusion was performed. There were 11 (11.1%) hospital death, and causes were heart failure (3), pneumonia (2), respiratory failure (1), mediastinitis (1), cerebral infarction (1), sepsis (1), myocardial infarction (1), and bleeding (1). During follow-up, 24 patients died, and causes were pneumonia (4), malignancy (3), heart failure (2), cerebral infarction (2), rupture of residual aneurysm (2), asthma (1), myocardial infarction (1), sepsis (1), multiple organ failure (1), traffic accident (1), and unknown (6). Postoperative survival was 75.2% at 3 years, 61.5% at 5 years, and 35.3% at 8 years. Event free ratio was 71.8% at 3 years, 58.6% at 5 years, and 30.8% at 8 years. Surgery of the aortic arch using selective cerebral perfusion is a safe and demonstrated acceptable short- and long-term outcomes.

Long-Term surgical outcomes following intraluminal sutureless graft insertion for type A aortic dissection

The long-term outcome of sutureless intraluminal graft insertion remains unclarified. Therefore, we reviewed the late surgical outcomes of patients who underwent this procedure for acute type A dissection. Between March 1990 and May 2000, 80 patients aged from 36 to 92 years underwent isolated replacement of the ascending aorta for type A acute aortic dissection. The surgical procedures performed were replacement with an intraluminal sutureless graft in 18 patients (group 1) and suturing of the aorta with a conventional Dacron prosthesis in 62 patients (group 2). The cross-clamp, extracorporeal circulation, circulatory arrest, and operation times were significantly shorter in group 1 than in group 2, and the amount of total blood transfusion was also significantly less in group 1 than in group 2. The hospital mortality rates were 11.1% (2/18) in group 1 and 9.7% (6/62) in group 2 (P > 0.999). The 5-year actuarial survival rates (including operative mortality) were 71% +/- 11% in group 1 and 77% +/- 9% in group 2 (P = 0.268). The event-free survival rates at 5 years were 80% +/- 10% in group 1, and 67% +/- 13% in group 2 (P = 0.780). Regarding graft-related complications, long-term follow-up revealed one graft-related death and one reoperation in group 1 (12.5%), and no graft-related complications in group 2 (0%) (P = 0.047). In conclusion, intraluminal sutureless grafts required less blood transfusion, and shorter cross-clamp, extracorporeal circulation, circulatory arrest, and surgery times. However, the procedure did not improve the hospital mortality or long-term outcome. In fact, the rate of graft-related complications was significantly higher in the intraluminal sutureless group than in the sutured group. Therefore, the intraluminal graft insertion technique should be used only under exceptional circumstances.

Percutaneous extracorporeal life support for treatment of fatal mechanical complications associated with acute myocardial infarction

Mechanical complications of acute myocardial infarction (AMI), such as free wall rupture, ventricular septal perforation (VSP), and mitral regurgitation due to papillary muscle rupture, are associated with high mortality rates. These complications result in extreme deterioration and increased risk of death in patients who do not receive timely resuscitation and surgical treatment. We studied the effectiveness of percutaneous extracorporeal life support (ECLS) for fatal mechanical AMI complications. Nine patients (7 men and 2 women, mean age 69 +/- 6 years) who suffered circulatory collapse refractory to conventional resuscitation were treated with ECLS. Circulatory collapse was caused by free wall rupture in 4 patients, VSP in 4, and mitral regurgitation due to papillary muscle rupture in 1. All patients were successfully resuscitated by ECLS and underwent surgical repair with conventional cardiopulmonary bypass. Eight patients required ECLS after surgery. Four of the 9 patients (2 with free wall rupture, 1 with VSP, and 1 with papillary muscle rupture) were successfully weaned from ECLS and were discharged. Three of the 4 survivors had no major complications, but the remaining survivor suffered neurological deficit. Four patients died while on devices. The duration of ECLS was from 13 to 167 h (mean 76 +/- 57 h) with a maximum bypass flow of 2.0 to 3.9 L/min (mean 2.9 +/- 0.6 L/min). There were no device-related complications during the support period. Total weaning rate was 56% (5/9), and survival was 44% (4/9). We conclude that ECLS can provide appropriate circulatory support during resuscitation and subsequent postoperative circulatory support for cardiovascular collapse associated with AMI complications.

Platelet damage caused by the centrifugal pump: laser-light scattering analysis of aggregation patterns

Platelets are damaged by shear force during centrifugal pumping; however, the mechanism of this damage has not been fully investigated. A new laser-light scattering (LS) assay method enables quantification of real-time changes in the number of platelet aggregates of different sizes. Using this method, we assessed the kinetics of platelet damage caused by the centrifugal pump from the standpoint of platelet aggregation capacity. Conventional optical density (OD) and LS methods were used to measure platelet aggregation with a Kowa AG-10 aggregometer. Platelet aggregation in fresh human blood was evaluated in a mock circuit for 3 h under a flow rate of 5.0 L/min and a pressure head of 100 mm Hg. Test samples were obtained before pumping for control, and at 1, 2, and 3 h after the start of pumping. The test series was begun 8 times. Aggregation after stimulation by 2.0 microg/ml collagen was determined; small (9 to 25 microm), medium (25 to 50 microm), and large (50 to 70 microm) aggregates were counted by the LS method. OD measurement at hourly intervals showed significant reduction in platelet aggregation. The LS method showed that generation of small and medium aggregates was not suppressed during pumping, but that generation of large aggregates was significantly reduced at 2 and 3 h of pumping. Platelet aggregation is significantly suppressed during centrifugal pumping, and the resulting platelet dysfunction is due mainly to inhibited development of small aggregates into larger aggregates.

Preoperative risk factors for hospital mortality in acute type A aortic dissection

BACKGROUND

Acute type A dissection is associated with postoperative complications and a high mortality rate. This study was performed to determine the perioperative risk factors leading to hospital mortality in patients with acute type A aortic dissection.

METHODS

One hundred twenty-two patients with acute type A aortic dissection treated surgically within 48 hours after onset were enrolled in this study. Thirty-two perioperative risk factors were used in statistical analysis for prediction of mortality. Risk factors for hospital death were investigated with univariate and multiple logistic regression analysis.

RESULTS

The in-hospital mortality rate including operative death was 12.3% (15 of 122 patients) and the actuarial survival rate (including in-hospital death) was 72%+/-6% at 5 years. Univariate analysis revealed 10 risk factors to be statistically significant predictors of hospital death: age, year of operation (1990 to 1995), Marfan syndrome, preoperative ST segment elevation, heart failure from aortic regurgitation, preoperative shock, preoperative coma, long operation time (> 6 hours), long cardiopulmonary bypass time (> 4 hours), and massive blood transfusion (> 20 units) (p < 0.05). Multiple logistic regression analysis confirmed preoperative ST-T segment elevation and massive blood transfusion to be statistically significant independent risk factors for hospital death (p < 0.05).

CONCLUSIONS

Preoperative ST-T elevation and massive blood transfusion during operation were identified as significant independent risk factors for hospital mortality after operation for acute type A aortic dissection. Our findings should contribute to estimation of operative risk in individual patients.

Platelet activation and aggregation during normothermic cardiopulmonary bypass

OBJECTIVE

The usefulness of heparin-bonded circuits under normothermic cardiopulmonary bypass has not been elucidated. We studied platelet activation and aggregation differences between heparin-bonded and nonheparin-bonded circuits in patients undergoing surgery involving normothermic cardiopulmonary bypass.

METHODS

Eight patients underwent coronary artery bypass grafting with non heparin-bonded circuits (controls) and 7 the same with heparin-bonded circuits (heparin group). Heparin bonding was applied to the blood contact surface of our system, including the oxygenator and connecting tubes. Patient body temperature was kept between 36 and 37 degrees C. Beta-thromboglobulin and platelet factor 4 were measured before, during, and after cardiopulmonary bypass, and platelet aggregation was evaluated by laser-light scattering.

RESULTS

Changes in beta-thromboglobulin and platelet factor 4 during and after cardiopulmonary bypass were similar in both groups. Small particle formation was the primary aggregate induced during and after cardiopulmonary bypass in both groups, and serial changes in particle formation up to 24 hours after cardiopulmonary bypass were similar in both groups.

CONCLUSIONS

Our results indicate that in 2-3 hours of normothermic cardiopulmonary bypass, heparin-bonded circuits are similar to nonheparin-bonded ones in platelet compatibility.

Cytokine mediated endothelial activation during and after normothermic cardiopulmonary bypass: heparin-bonded versus non heparin-bonded circuits

Studies evaluating cytokine production under normothermic cardiopulmonary bypass (CPB) are limited. We evaluated cytokine production, levels of thrombomodulin (TM), and soluble endothelium-derived adhesion molecules (ICAM-1) under normothermic CPB with and without heparin-bonded circuits. Nine patients treated with non heparin-bonded circuits (control group), and seven patients treated with heparin-bonded circuits (heparin group) were the subjects. Granulocyte elastase (G-E), and interleukin (IL) -6 and IL-8 were chosen as proinflammatory mediators, and TM and ICAM-1 served as indicators for endothelial damage. Blood samples were obtained before CPB, 30 minutes after initiation of CPB, at the termination of CPB, and 2 and 24 hours after CPB. G-E values in the heparin group were lower than those in the control group after 30 minutes of CPB. A G-E surge occurred at the end of CPB, and IL-6 and IL-8 surges were observed 2 hours after CPB in both groups. TM and ICAM-1 values, which were reduced at the initiation of CPB, returned to initial levels 2 hours after CPB, and exceeded them 24 hours after CPB compared with preCPB levels. Both groups showed similar changes. We conclude that there are no significant differences in serial G-E, IL-6, IL-8, TM, or ICAM-1 levels between the heparin and control groups during or after normothermic CPB for 2 to 3 hours.

Early and late surgical outcomes of acute type A aortic dissection in patients aged 75 years and older

BACKGROUND

With the general increase in human lifespan, aortic surgeons are faced with an increasing prevalence of acute type A aortic dissection in the elderly. In this study, we reviewed early and late surgical outcomes of acute type A dissection (operation within 48 hours after onset) in patients aged 75 years and older.

METHODS

Between 1990 and 1999, 109 patients underwent emergency operation for acute type A dissection at Omiya Medical Center. Twenty-three patients were aged 75 years and older (elderly group, mean age, 79.1 +/- 4.7 years) and 86 were younger than 75 years old (younger group, mean age, 58.7 +/- 10.8 years). Early and late outcomes of both groups were compared.

RESULTS

The hospital mortality rates were 13.0% (3 of 23) in the elderly group and 10.5% (9 of 86) in the younger group (p = 0.71). In the elderly, actuarial survival rate (including the operative mortality rate) at 1, 3, and 5 years was 78% +/- 9% for each point. In the younger group, the rates were 88% +/- 4% at 1 year, 83% +/- 4% at 3 years, and 81% +/- 5% at 5 years (p = 0.57). Actuarial event-free rates were 84% +/- 8% at 1 year, 77% +/- 11% at 3 years, and 77% +/- 11% at 5 years in the elderly group. In the younger group, the rates were 96% +/- 2% at 1 year, 88% +/- 4% at 3 years, and 81% +/- 7% at 5 years (p = 0.27).

CONCLUSIONS

No significant differences in the hospital mortality, actuarial survival, or event-free rates were observed between the two groups. Operation for type A acute aortic dissection in patients aged 75 years or older can be performed with acceptable risk of death, and long-term results are satisfactory.

Platelet activation in the gyro C1E3 centrifugal pump: comparison with the terumo capiox and the Nikkiso HPM-15

The Gyro C1E3 was developed as a cardiopulmonary bypass pump incorporating the sealless double pivot bearing system. In this study, we evaluated platelet activation induced by the Gyro C1E3 in vitro and in comparison to that of other centrifugal pumps. Rates of increase (RI) for beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) in the Gyro C1E3 were calculated from in vitro data and compared with the rate of increase in the Capiox (Terumo) and HPM-15 (Nikkiso) pumps. Fresh human blood was used, and a flow of 5.0 L/min with a DeltaP (pressure difference between the outlet and inlet of the pump) of 100 mm Hg employed. RI = Deltabeta-TG/DeltaN and DeltaPF4/DeltaN were used where Deltabeta-TG is the increase in beta-TG, DeltaPF4 is the increase in PF4, and DeltaN is the increase in the passing number and where N = Qt/V (t = time, V = priming volume, and Q = flow rate). The mean RI for beta-TG was 0.26 +/- 0. 05 in the Gyro C1E3, 0.20 +/- 0.07 in the Capiox, and 0.15 +/- 0.02 in the HPM-15. The mean RI for PF4 was 0.15 +/- 0.03 in the Gyro C1E3, 0.12 +/- 0.05 in the Capiox, and 0.09 +/- 0.04 in the HPM-15. While there was no difference in RI for beta-TG and PF4 between the Gyro C1E3 and Capiox, RI for beta-TG and PF4 were significantly higher in the Gyro C1E3 than in the HPM-15 (p = 0.006 and 0.029). In vitro evaluation using RI for beta-TG and PF4 showed platelet damage caused by the Gyro C1E3 and the Capiox to be nearly equal while the HPM-15 was less traumatic to platelets than the Gyro C1E3.

Transient rise in serum soluble Fas (APO-1/CD95) in patients undergoing cardiac surgery

The Fas molecule, also designated APO-1/CD95, belongs to the tumor necrosis factor (TNF) receptor family. It is a widely expressed membrane-anchored protein that induces apoptosis by Fas/Fas ligand (Fas-L) mediation. It was reported that Fas-mediated apoptosis plays an important role in regulation of the immune system, systemic inflammatory response, and ischemia/reperfusion injury. A soluble form of Fas (sFas) is produced either through the proteolytic cleavage of membrane-bound receptors or by alternative splicing, and sFas is thought to be implicated in apoptosis. In addition, sFas released damaged cells, and elevated serum levels of sFas reflect systemic tissue damage. To examine the specificity of sFas production during cardiac surgery with cardiopulmonary bypass, we serially measured the serum sFas levels in 13 patients during and after surgery. Blood samples were obtained before surgery, at the end of cardiopulmonary bypass, at the end of surgery, and at 12 h after surgery. Levels of serum sFas were determined by sandwich ELISA. Seven patients undergoing other types of surgeries served as controls. Although increased sFas was not observed in the control group, a significantly higher sFas level was detected in cardiac surgical patients at the end of surgery than before surgery (p = 0. 028), and the level decreased at 12 h after surgery. A significant correlation was observed between the maximum sFas values and the length of surgery (r = 0.659, p = 0.012) and cardioplegic arrest (r = 0.559, p = 0.046). Elevated serum sFas levels were observed in patients undergoing cardiac surgery, and these serum sFas levels reflect the severity of a surgery. sFas may play an important role in the pathophysiology of surgical damage caused by cardiac surgery with cardiopulmonary bypass.

[Results of valve surgery combined with CABG]

During recent 8 years, combined procedures of valve surgery and coronary artery bypass grafting (CABG) were performed in fifty-five patients at Omiya Medical Center. AVR (31 cases), MVR (12 cases), MVP (8 cases), DVR (1 case), TVR (1 case), TAP (2 cases) were performed with the average of 2.0 bypass graftings in this series. Five patients died due to organ ischemia (3 cases), cerebral embolism and heart failure. Organ ischemia occurred in dialysis patients and the results of combined surgery in dialysis patients were unsatisfactory (3/5 cases, mortality rate is 60%). On the other hand, the results of combined surgery in non-dialysis patient is reasonable (2/50 cases, mortality rate is 4%). Before the combined surgery in dialysis patient, careful analysis of surgical risk including organ ischemia is needed and avoiding the prolonged perfusion time is important to achieve a successful surgical result.

Resuscitation and circulatory support using extracorporeal membrane oxygenation for fulminant pulmonary embolism

Fulminant pulmonary embolism (PE) with circulatory collapse is associated with a high mortality rate due to acute right ventricular failure and hypoxia. Immediate and appropriate resuscitation and circulatory support in the perioperative period is mandatory to prevent sudden death. Extracorporeal membrane oxygenation (ECMO) was recently introduced for extracorporeal life support in patients with circulatory collapse and has provided an excellent outcome. We report on the effectiveness of ECMO support for fulminant PE. Seven patients were placed on veno-arterial ECMO for circulatory collapse caused by fulminant PE refractory to conventional treatment. After resuscitation, all patients underwent pulmonary angiography, and thrombolytic therapy was administered in all 7 patients under ECMO support. Three patients who did not improve by thrombolysis underwent embolectomy with standard cardiopulmonary bypass. Two thrombolysis and 2 surgery patients were weaned from bypass and survived. The duration of support ranged from 18-168 h (mean = 67.8 +/- 67.1 h), with maximum bypass flow rates of 2.0-4.5 (mean = 3.5 +/- 0.9). There were no device-related complications during support. In total, 4 patients (57%) were successfully weaned from support and discharged from the hospital in good condition. All patients who survived required prolonged support (27, 82, 151, and 168 h). We conclude that resuscitation and circulatory support using ECMO can be effective, life-saving measures in cases of circulatory collapse caused by fulminant PE.

Enhanced responsiveness of circulatory neutrophils after cardiopulmonary bypass: increased aggregability and superoxide producing capacity

Cardiac surgery with cardiopulmonary bypass (CPB) induces a whole body inflammatory response that sometimes leads to postoperative organ dysfunction, and neutrophil activation plays an important role in this reaction. Neutrophil priming has been described as a change in neutrophil status such that neutrophils show enhanced responsiveness to a second activating stimulus. We hypothesized that neutrophil priming occurs by cardiac surgery with CPB and is temporally related to the neutrophilia after surgery. To evaluate primed circulatory neutrophil status, we measured aggregation activity stimulated by N-formyl-methyl-leucyl-phenyl-alanine (FMLP) and free radical producing activity by tumor necrosing factor (TNF) alpha in peripheral blood samples. Eleven adult patients undergoing elective cardiac surgery with CPB were studied. Blood samples were taken before surgery, at the end of bypass, 12 h after surgery, and 7 days after surgery. Aggregation activity and superoxide generation were significantly elevated 12 h after surgery when compared to presurgery values, indicating that cardiac surgery is associated with circulatory neutrophil priming. The number of neutrophils markedly increased at the end of cardiopulmonary bypass and reached a peak 12 h after surgery. The circulatory neutrophils of cardiac surgical patients become primed after surgery, coincident with the peak neutrophil count. These results suggest that circulatory neutrophils after cardiac surgery with CPB have enhanced responsiveness and are predisposed to systemic inflammation.

Influence of surgical procedures on interleukin-6 and monocyte chemotactic and activating factor responses: CABG vs. valvular surgery

Interleukin-6 (IL-6) and monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1) play pivotal roles in systemic inflammation, immune response, and tissue damage after cardiopulmonary bypass (CPB). Previous reports have described transient rises in IL-6 and MCAF after CPB, but the data seem to vary according to the different surgical procedures used. To evaluate the influence of the different surgical procedures on the proinflammatory cytokine responses, we compared perioperative serum IL-6 and MCAF release in coronary artery bypass grafting (CABG) and valvular surgery cases. Eighteen CABG (CABG group) and 7 single valvular cardiac surgery patients (valve group) were included in this study. Blood samples were taken to measure the serum concentrations of IL-6 at the induction of anesthesia, at the removal of the aortic cross-clamp, at the end of CPB, at the end of surgery, and 24 h after the termination of surgery. Serum IL-6 and MCAF were assayed by ELISA. Serum IL-6 increased immediately after aortic declamping and reached its peak at the end of surgery in both groups. Serum IL-6 concentrations at the end of surgery and 24 h after surgery were significantly higher in the valve group than in the CABG group (123.9 +/- 21.7 pg/ml vs. 79.7 +/- 10.4 pg/ml, p = 0.049; 113.6 +/- 25.0 pg/ml vs. 39.9 +/- 11.5 pg/ml, p = 0.006, respectively). Serum MCAF increased immediately after aortic declamping, and the MCAF level at the end of surgery was significantly higher in the valve group than in the CABG group (1118.4 +/- 353.9 pg/ml vs. 241.0 +/- 71.2 pg/ml, p = 0.002, respectively). IL-6 and MCAF may play important roles in the pathophysiology of surgical damage with CPB, and the different surgical procedures appear to affect the proinflammatory cytokine release after cardiac surgery differently.

Conduction disturbances after superior septal approach for mitral valve repair

BACKGROUND

The superior septal approach sacrifices the sinus node artery, and it requires more invasive incisions into the right and left atria. Therefore, postoperative rhythm disturbances could be troublesome in patients with SSA. In this study, we evaluated perioperative and midterm conduction disturbances in the cardiac rhythms of patients who had a SSA for mitral valve repair.

METHODS

Fifty-two patients had mitral valve operations by the superior septal approach, and cardiac rhythm status was assessed. The mean follow-up period was 15 +/- 8 months. In patients with normal sinus rhythms preoperatively, serial changes in PR intervals were also assessed. Holter electrocardiograms were used 6 to 12 months postoperatively. Twelve patients who had mitral valve operations by conventional left atriotomy from the right side of the left atrium served as the control group.

RESULTS

There were no operative deaths, but one patient in the experimental group died of cerebral hemorrhage 4 months postoperatively. No intractable arrhythmias occurred. Of the 25 patients who maintained sinus rhythms, preoperative PR interval on electrocardiogram was 155 +/- 20 milliseconds. Postoperative PR intervals increased for 1 week, had decreased within 2 weeks postoperatively, and returned to the normal range by 6 months postoperatively. Holter electrocardiograms of 17 patients did not show supraventricular arrhythmias exceeding 3% of the total beats. None of the patients needed pacemaker implantation. The PR intervals of 5 patients with normal sinus rhythms in the control group did not show significant changes perioperatively.

CONCLUSIONS

The superior septal approach is excellent for mitral valve operations because it overcomes postoperative dysrhythmias.

Assessment of the myocardial protective effect of antegrade warm blood cardioplegia by measuring the release of biochemical markers

Intermittent warm blood cardioplegia has been reported as a valuable alternative for myocardial protection in cardiac surgery; however, conflicting experimental data have been published. To assess the clinical effectiveness of intermittent warm cardioplegia, we measured the release of troponin-T (Tn-T), a highly sensitive and specific marker of myocardial damage, and creatine kinase MB isoenzyme (CK-MB), in 12 patients who underwent elective coronary artery bypass grafting (CABG) with antegrade intermittent warm blood cardioplegia (37 degrees C) being the warm group, in comparison with 16 patients who underwent CABG with antegrade intermittent cold blood cardioplegia (4 degrees C) being the cold group. Blood samples were taken to determine the serum concentrations of CK-MB and Tn-T, at the induction of anesthesia, then 3, 6, 12, and 24h after the termination of cardiopulmonary bypass (CPB). The peak increase in serum CK-MB levels, 3h after CPB, was significantly lower in the warm group than in the cold group, at 27.8+/-7.8 IU/l vs. 40.8+/-12.6 IU/l, respectively (P = 0.0042). The serum Tn-T 12 h after CPB was significantly lower in the warm group than in the cold group, at 1.40+/-0.71 ng/ml vs. 2.06+/-0.95 ng/ml, respectively (P = 0.049). In conclusion, intermittent antegrade warm blood cardioplegia showed effective myocardial protection in elective CABG.

Platelet aggregation during cardiopulmonary bypass evaluated by a laser light-scattering method

BACKGROUND

In regard to postoperative bleeding, the most important consequence of cardiopulmonary bypass (CPB) is the loss of aggregability. However, the mechanism of platelet aggregation loss during CPB is unclear. Newly developed particle-counting methods that use light scattering can be used to quantify changes in the number of platelet aggregates of different sizes after application of an aggregating stimulus. Using a light-scattering method, we investigated changes in platelet aggregation during cardiac operation.

METHODS

Nineteen patients undergoing CPB were evaluated. Blood samples were obtained before the operation, 1 hour after initiation of CPB, at the end of CPB, at the end of the operation, and on day 1 after the operation. Platelet aggregation after stimulation by 2.5 micromol/L adenosine diphosphate and 2.0 microg/mL collagen was determined; small (9 to 25 microm), medium (25 to 50 microm), and large (50 to 70 microm) aggregates were counted.

RESULTS

Generation of medium and large aggregates after stimulation with adenosine diphosphate and collagen were significantly decreased with CPB, whereas, in spite of hemodilution, the quantity of the small aggregates was maintained at the elevated level.

CONCLUSIONS

These results reflect the fact that CPB does not affect the first phase of aggregation. It suggests that platelet dysfunction associated with CPB is mainly caused by an inhibition in the development of small aggregates into larger aggregates.

Usefulness of extracorporeal membrane oxygenation for treatment of fulminant myocarditis and circulatory collapse

Prognosis for fulminant myocarditis with cardiogenic shock refractory to conventional therapy is poor. This report describes mechanical circulatory support with extracorporeal membrane oxygenation as an effective alternative for treating fulminant myocarditis with circulatory collapse.

Right coronary artery dissection and acute infarction due to blunt trauma: report of a case

Coronary artery dissection occurring after a nonpenetrating chest trauma is extremely rare. We describe herein the case of a 43-year-old man who suffered traumatic myocardial infarction after an intimal tear of the right coronary artery had been inflicted by a horse stepping on his back.

Evaluation of platelet damage in two different centrifugal pumps based on measurements of alpha-granule packing proteins

Mechanical trauma caused by centrifugal pumps is usually evaluated in terms of hemolysis. However, platelet damage caused by centrifugal pumps has not been studied well. We evaluated platelet damage in 2 different centrifugal pumps, the Medtronic BioMedicus BP-80 and the Terumo Capiox, in vitro and compared the results in terms of hemolysis. To evaluate platelet damage, the rate of increase (RI) for beta-thromboglobulin (beta-TG) and platelet factor-4 (PF-4) were measured by enzyme immunoassay. RI was defined as follows: RI for beta-TG is deltabeta-TG/deltaN and RI for PF-4 is deltaPF-4/deltaN where deltabeta-TG is the increase in beta-TG, deltaPF-4 is the increase in PF-4, and deltaN is the increase of the passing number, which is defined in the following equation: N = Qt/V (t, time; V, priming volume; Q, flow rate). Each pump was tested in a mock circuit for 3 h under a flow rate of 5 L/min and a pressure head of 100 mm Hg using fresh human heparinized blood (n = 5). For comparison, the normalized index of hemolysis (NIH) values were calculated for both pumps. The NIH values did not indicate a significant difference between the Capiox and the BP-80 pumps (Capiox vs. BP-80, 0.0021 +/- 0.0004 vs. 0.0034 +/- 0.0007, NS). However, the RI values for beta-TG and PF-4 in the Capiox were significantly lower than in the BP-80 (beta-TG, 0.198 +/- 0.047 vs. 0.376 +/- 0.049; PF-4, 0.080 +/- 0.014 vs. 0.268 +/- 0.043, p < 0.05). In conclusion, although there was no significant difference between the 2 pumps in terms of hemolysis, the Capiox centrifugal pump induced less platelet damage than the BP-80. The results suggest that measurements of RI for beta-TG and PF-4 are more sensitive parameters than NIH values for evaluating blood cell damage.

Platelet protective effect of TAK-029, a novel glycoprotein IIb/IIIa antagonist: an in vitro study

Previous studies have indicated that exposure of fibrinogen receptors associated with the glycoprotein IIb/IIIa complex contributes to platelet loss during cardiopulmonary bypass. TAK-029 is a newly developed reversible, nonpeptide inhibitor of platelet glycoprotein IIb/IIIa receptors. In this study, we tested the platelet preserving effect of TAK-029 in an in vitro model. The methods included the comparison of the release of beta-thromboglobulin (beta-TG) between a TAK-029 group (n = 5) and a control group (n = 5) in a mock circulation under a shear force generated by a centrifugal pump. To evaluate the degree of beta-TG release, deltabeta-TG/deltaT was calculated where deltabeta-TG is the increase in beta-TG and deltaT is the time. The results showed that the value of deltabeta-TG/deltaT in the TAK-029 group was significantly lower than it was in the control group (4.22 +/- 0.27 x 10(2) ng/ml vs. 7.33 +/- 0.66 x 10(2) ng/ml, respectively). In conclusion, TAK-029 reduced the platelet activation under the shear forces of an in vitro model, suggesting that TAK-029 is a potential candidate for platelet protection during cardiopulmonary bypass.

Recovery from lymphocytopenia and prognosis after adult extracorporeal membrane oxygenation

Extracorporeal circulation severely impairs the host immune system. Also decreases in circulatory lymphocytes correlate with greater degrees of surgical damage. In this study, the pattern of recovery from lymphocytopenia after extracorporeal membrane oxygenation was retrospectively evaluated from a prognostic viewpoint. The results showed that the circulatory lymphocyte count of survivors returned to normal levels within 5 days after their being weaned from extracorporeal membrane oxygenation, while the circulatory lymphocyte count of nonsurvivors remained at low levels. Because it is easy to measure the number of peripheral lymphocytes, the changing pattern of the circulatory lymphocytes might be a simple and reliable prognostic factor after extracorporeal membrane oxygenation.

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.

Platelet damage caused by the centrifugal pump: in vitro evaluation by measuring the release of alpha-granule packing proteins

Platelets are more vulnerable to damage than erythrocytes because platelets are easily activated by contact with extracorporeal circuits and by exposure to shear forces. However, the degree of platelet damage caused by centrifugal pumps is unclear. To evaluate platelet damage in different pumping conditions, the rates of increase for specific proteins in platelet alpha-granules, beta-thromboglobulin (beta-TG), and platelet factor 4 (PF-4) were measured in both in vitro simulated left ventricular assist device (LVAD) and cardiopulmonary bypass (CPB) conditions and compared with the erythrocyte trauma. A flow of 5.0 L/min with deltaP of 100 mm Hg for LVAD (low pressure head condition) and a flow of 5.0 L/min with deltaP of 350 mm Hg for CPB (high pressure head condition) were investigated. Each condition was tested 4 times for 3 h in a mock circuit with a Capiox (Terumo, Tokyo, Japan) centrifugal pump using fresh human blood. Blood was sampled at 1 h intervals, measuring plasma free hemoglobin (fHb), beta-TG, and PF-4. To evaluate the degree of damage, the rates of increase of fHb, beta-TG, and PF-4 were calculated for each condition as deltafHb/deltaN, deltabeta-TG/deltaN, and deltaPF-4/deltaN where deltafHb is the increase in plasma free hemoglobin, deltabeta-TG is the increase in beta-TG, deltaPF-4 is the increase in PF-4, and deltaN is the increase in the passing number. The passing number is defined in the following equation: N = Qt/V where t is the time, V is the priming volume, and Q is the flow rate. There was no significant difference between the 2 conditions (low pressure head condition versus high pressure head condition) in the rate of increase of fHb (0.0035+/-0.0004 vs. 0.0034+/-0.0010 g/100 L, NS). Contrary to this, the rates of increase for specific proteins in platelet alpha-granules in the high pressure head condition demonstrated a significantly higher rate of increase than in the low pressure head condition. The mean rate of increase for beta-TG in the low pressure head condition was 0.22+/-0.03 ng/ml and in the high pressure head condition was 0.51+/-0.05 ng/ml (p < 0.05). The rate of increase for PF-4 in the low pressure head condition was 0.11+/-0.02 ng/ml and in the high pressure head condition was 0.30+/-0.06 ng/ml (p < 0.05). These results suggest that measurements of beta-TG and PF-4 may be more sensitive parameters than hemolysis for evaluating blood cell trauma and that platelets are more vulnerable to mechanical damage by a centrifugal pump than erythrocytes.

Comparison of the Gyro C1E3 and BioMedicus centrifugal pump performances during cardiopulmonary bypass

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

Hemolysis in different centrifugal pumps

Different types of centrifugal pumps cause different amounts of hemolysis based on shear stress and blood exposure time. However, the hemolytic characteristics of centrifugal pumps in each clinical condition are not always clear. We compared the hemolytic characteristics of one cone-type centrifugal pump (Medtronic BioMedicus BP-80) and 2 impeller-type centrifugal pumps (Nikkiso HMS-12 and Terumo Capiox) under experimental conditions simulating their use in cardiopulmonary bypass (CPB), extracorporeal membrane oxygenation (ECMO), and percutaneous cardiopulmonary support (PCPS) as well as their use as left ventricular assist devices (LVADs). The normalized indexes of hemolysis (NIHs; grams free plasma hemoglobin per 100 L blood pumped) during use as LVADs were not significantly different among the 3 pumps. The BP-80 pump produced almost 3-fold more hemolysis than the HMS-12 and Capiox pumps during CPB, 3- to 4-fold more hemolysis during ECMO, and 5.5-fold more hemolysis during PCPS. The 2 impeller-type centrifugal pumps will therefore cause less hemolysis under high flow, high pressure difference (as in CPB) and low flow, high pressure difference (as in ECMO and PCPS) conditions than the cone-type pump.

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 non-pulsatile permanent rotary blood pump

For many years, a common belief was that non-pulsatile perfusion produced physiological and circulatory abnormalities. Since 1977 our group has reported, if a 20% higher blood flow was used more than required for a pulsatile blood pump, there would be no circulatory or physiological abnormalities. These experimental findings confirmed that there was no difference in clinical outcome when using a pulsatile or non-pulsatile blood pump. Furthermore, the non-pulsatile rotary blood pump has demonstrated efficient and reliable performance in various clinical situations. The non-pulsatile blood pump is a simple and reliable design, that can be easily manufactured, and has the following desirable features. There is no need to incorporate heart valves, a large orifice inflow conduit, or a compliance volume-shifting chamber. Since an electrical motor operates continuously, the on-and-off motion required for a pulsatile pump is not necessary; therefore, it becomes a more efficient and durable system. Further, the control algorism is simpler and more reliable than a pulsatile pump. Considering these factors, the non-pulsatile blood pump can be selected for a permanently implantable assist device. To develop an implantable non-pulsatile cardiac device, it is necessary to incorporate seven features in the system such as: small size, atraumatic features, anti-thrombogenic features, anti-infection features, durable and simple design, and low energy requirement with easy controllability.

Transient rise in serum cytokines during coronary artery bypass graft surgery

In order to examine the specificity of cytokine production during coronary artery bypass graft (CABG) surgery, we serially measured serum levels of monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), interleukin-6 (IL-6), interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF), in twenty patients between 52 and 80 years of age, during surgery and 2 days afterwards. Serum MCP-1, as well as IL-8 and IL-6, increased significantly during the surgery (P < 0.05), while IL-1 beta and TNF did not. MCP-1, IL-8 and IL-6 concentrations were not different in the sera of three patients tested at three different sites, i.e., the hepatic vein, pulmonary artery and radial artery. They increased in parallel in each patient, although the actual timing of the increase relative to the surgical step varied among individuals. In complicated patients, MCP-1, IL-8 and IL-6 showed higher peaks and persisted longer than in patients without complications. The universal and simultaneous appearance of MCP-1, IL-8 and IL-6 could indicate that these three cytokines may be stimulated by a yet undiscovered stimulus (or stimuli) which occurs systemically despite the independent pathways of production.

Ex vivo evaluation of the NASA/DeBakey axial flow ventricular assist device. Results of a 2 week screening test

The authors investigated the antithombogenicity of the NASA/DeBakey axial flow ventricular assist device in an ex vivo calf model. The device is 3 inches in length and 1 inch in largest diameter. The pump weighs 53 g and displaces 15 ml. The unit consists of three major components: a flow straightener, a spinning inducer/impeller, and a diffuser. The impeller has rod shaped permanent magnets embedded within the six blades and is activated magnetically by a motor stator that is positioned outside the flow tube. Previous 2 day screening tests demonstrated an antithrombogenic configuration in short-term implantation. Based on the results of these 2 day screening tests, five pumps with the best configuration were implanted into a calf for 2 weeks for anti thrombogenicity confirmation. Pumps were implanted paracorporeally, and heparin was used to maintain activated clotting time to approximately 250 sec. Each pump was changed every 2 weeks as planned. During the experiment, all pumps demonstrated stable pumping. The required electric power was 7 to 8 watts and pump flow was maintained at 4 L/min. The calf was in excellent condition. Liver and renal function were maintained, plasma free hemoglobin was kept at less than 4 mg/dl (3.3 +/- 0.3 mg/dl), and lactate dehydrogenase was 1043 +/- 36 units/L. In this experimental series, all five pumps passed the 2 week implantation. Two week ex vivo test results indicated very slight thrombus in the hub areas of some pumps. For the next phase of the implantation study, minor design optimization is necessary to completely eliminate thrombus formation. According to our step by step approach, the in vivo test aiming for long-term implantation is ongoing.

Acute occlusion of the descending thoracic aorta: report of a case

This report describes the unusual case of an acute occlusion of the descending thoracic aorta in a 52-year-old woman. The patient underwent successful extraanatomical bypass with intraoperative hemodialysis.

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.