Tissue engineering lamb heart valve leaflets

Tissue engineered lamb heart valve leaflets (N - 3) were constructed by repeatedly seeding a concentrated suspension of autologous myofibroblasts onto a biodegradable synthetic polymeric scaffold composed of fibers made from polyglycolic acid and polylactic acid. Over a 2-week period the cells attached to the polymer fibers, multiplied, and formed a tissue core in the shape of the matrix. The tissue core was seeded with autologous large-vessel endothelial cells that formed a monolayer which coated the outer surface of the leaflet. The tissue engineered leaflets were surgically implanted in place of the right posterior pulmonary valve leaflet of the donor lamb while on cardiopulmonary bypass. Pulmonary valve function was evaluated by two-dimensional echocardiography with color Doppler which demonstrated valve function without evidence of stenosis and with only trivial regurgitation under normal physiologic conditions. Histologically, the tissue engineered heart valve leaflets resembled native valve leaflet tissue.

[Repair for atrioventricular valve regurgitation using autologous pericardium: report of a case]

A 13-year-old boy with [SLL] single left ventricle first underwent ventricular septation using a dacron patch at 3 years of age. Eight years after the first surgery, he presented with general fatigue on exertion as the chief complaint. Right-sided atrioventricular valve regurgitation, and dilatation of the right heart were diagnosed. Eleven years after surgery, right heart failure was uncontrollable by medicine, and 2nd surgery was performed. At operation, the right-sided heart valve leaflet was tightly adherent to the dacron septation patch, and valve plasty was judged impossible. We repaired the right-sided atrioventricular valve using an autologous pericardial valve leaflet and sub-valvular tissue. The postoperative course was uneventful, and he has been free from any complication for 33 months.

Double-Switch operation for congenitally corrected transposition

Double-switch operation was performed in 76 patients with congenitally corrected transposition of the great arteries at the Heart Institute of Japan, Tokyo Women's Medical University. Detailed surgical techniques of Mustard and Senning procedures for inlet switch, as well as arterial switch operation, pulmonary reconstruction by direct right ventricular-pulmonary arterial anastomosis, and external conduit repair for outlet switch are described in detail.

Double switch operation for superior-inferior ventricles

Superior-inferior ventricles are a rare cardiac malformation characterized by the two ventricles lying one above the other instead of side by side. Consequently, the interventricular septum that separates such ventricles is horizontal, and anomalies of the atrioventricular valves and the ventriculoarterial relations are almost always present. This complex anomaly is difficult to manage with an operation, so few cases have been reported. We describe a successful experience in which we performed a double switch operation, consisting of the Senning and Jatene procedures, for this rare malformation accompanied by double-outlet right ventricle [S,L,L]. This is the first report we have been able to locate of a double switch operation for superior-inferior ventricles.

Coarctation of the aorta and ventricular septal defect: should we perform a single-stage repair?

BACKGROUND

Optimal management for coarctation of the aorta and ventricular septal defect remains controversial. The current study was undertaken to determine outcome, including recoarctation after 2-stage repair, at our institution.

METHODS

Between 1984 and 1998, 79 patients younger than 3 months with coarctation and ventricular septal defect underwent 2-stage repair at our institution. The first-stage operation consisted of subclavian flap angioplasty and pulmonary banding. The median age at the time of first operation was 28 days (range, 4-90 days), and median weight was 3.2 kg (range, 1.2-5.1 kg). Hypoplastic aortic arch was present in 27 patients, and coexisting anomalies were present in 13 patients. After a mean interval of 10.4 +/- 9.6 months, they underwent a second-stage repair, with closure of the ventricular septal defect and pulmonary debanding.

RESULTS

There were 2 hospital deaths and 4 late deaths. Mean follow-up was 9.2 +/- 4.9 years (range, 2.0-18.3 years), and actuarial survival was 92.3% at 10 years (95% confidence interval, 86.6%-98.3%). Age at first operation, body weight, hypoplastic arch, and coexisting anomalies had no significant influence on overall mortality. Freedom from recoarctation rate was 90.4% at 10 years (95% confidence interval, 83.7%-97.2%).

CONCLUSION

To diminish mortality and the recoarctation rate and also to decrease the possibility of complications related to circulatory arrest and allogeneic blood transfusion, 2-stage repair is still an effective technique for coarctation of the aorta associated with ventricular septal defect.

Tissue-engineered vascular autograft: inferior vena cava replacement in a dog model

Tissue-engineered vascular autografts (TEVAs) were made by seeding 4-6 x 10(6) of mixed cells obtained from femoral veins of mongrel dogs onto tube-shaped biodegradable polymer scaffolds composed of a polyglycolid acid (PGA) nonwoven fabric sheet and a copolymer of L-lactide and caprolactone (n = 4). After 7 days, the inferior vena cavas (IVCs) of the same dogs were replaced with TEVAs. After 3, 4, 5, and 6 months, angiographies were performed, and the dogs were sacrificed. The implanted TEVAs were examined both grossly and immunohistologically. The implanted TEVAs showed no evidence of stenosis or dilatation. No thrombus was found inside the TEVAs, even without any anticoagulation therapy. Remnants of the polymer scaffolds were not observed in all specimens, and the overall gross appearance similar to that of native IVCs. Immunohistological staining revealed the presence of factor VIII positive nucleated cells at the luminal surface of the TEVAs. In addition, lesions were observed where alpha-smooth muscle actin and desmin positive cells existed. Implanted TEVAs contained a sufficient amount of extracellular matrix, and showed neither occlusion nor aneurysmal formation. In addition, endothelial cells were found to line the luminal surface of each TEVA. These results strongly suggest that "ideal" venous grafts with antithrombogenicity can be produced.

[Cryopreservation of vascular mixed cell for tissue engineering in cardiovascular surgery]

Tissue engineering (TE) is a new discipline that offers the potential to create replacement structures from autologous cells and biodegradable polymer scaffold. Various vascular and valvular grafts have been tried to create with this TE approach. In clinical use of this technique, harvested and cultured cells have to keep viability until implantation as tissue engineered tissue. But few research for cryopreservation of vascular mixed cells has been performed. So, we investigated the proper method for cryopreservation of vascular mixed cells harvested from femoral artery and vein of dogs. Cells were cultured and divide into three groups, A: cryopreserving in 5% dimethylsulfoxide (DMSO), hydroxyethyl starch (HES), and fetal bovine serum (FBS) with -80 degrees C freezer; B: cryopreserving in 10% DMSO and FBS with programmed freezer; C: control (continuous culture in media). After rapid thawing at 40 degrees C, group A showed higher viability than group B with flow cytometry. The results means that vascular mixed cells can be successfully cryopreserved in the DMSO/HES mixture simply and inexpensively, without rate controlled freezing.

Surgical intervention for anomalous origin of the left coronary artery from the pulmonary artery: the Tokyo experience

BACKGROUND

Few studies after surgical repair of the anomalous origin of the left coronary artery have reported the importance of the mitral annuloplasty or the long-term results.

METHODS

Between January 1982 and March 2000, 29 patients with anomalous origin underwent surgical intervention at our institution (direct aortic reimplantation in 19 and Takeuchi procedure in 10). Age at the time of operation ranged from 2 months to 24 years (median, 29.3 months), and 9 patients were infants. Twenty-four patients had varying degrees of mitral incompetence. Simultaneous mitral annuloplasty at the anterolateral commissure was performed in all 24 patients with incompetence.

RESULTS

There were 2 hospital deaths among the infants, and no late deaths. Mean follow-up was 100 +/- 57 months, and the actuarial survival was 93.1% at 10 years (70% confidence limits, 87-99). Cardiothoracic ratio at discharge was not decreasing significantly (P =.35); however, this value 5 years after the operation showed the significant decrease (P =.003) versus preoperative value. Preoperative mitral incompetence decreased in all but one of the operative survivors with mitral annuloplasty at the last follow-up. The left ventricular fractional shortening z-score was not normalized at discharge but was normalized in the late period.

CONCLUSION

These data demonstrate that impaired left ventricular function normalized in the long term (even if it was below normal immediately after operation) after 2-coronary repair. We recommend that the simultaneous mitral annuloplasty should be performed at the time of operation for patients who have mitral incompetence with anomalous origin of the left coronary artery.

Definite improvement in left ventricular function at six years after the Takeuchi procedure

We report a case of a six-year-old girl who underwent the Takeuchi procedure for anomalous origin of the left coronary artery from the pulmonary artery at the age of 4 months. The left ventricular function was severely deteriorated before the initial operation and at 6 years after the procedure showed a remarkable improvement. Mitral regurgitation disappeared during the 6 years. The intrapulmonary tunnel was sufficiently patent to provide adequate blood flow for the anomalous coronary artery. This patient showed supravalvular stenosis due to shrinkage and thickening in the equine pericardium used for reconstruction of the pulmonary artery, and this stenosis was successfully released by autologous pericardial patch angioplasty.

[Heparin monitoring during cardiopulmonary bypass in congenital heart surgery]

The Hepcon/HMS system automatically provides the activated clotting time and a whole blood heparin concentration. It also provides the adequate protamine dose by titration of protamine to heparin. 45 patients undergoing congenital heart surgery with cardiopulmonary bypass (CPB) were studied by the Hepcon/HMS device. We measured the heparin dose response before heparin administration, and the ration between the dose of protamine (ml) which was necessary for heparin neutralization at the termination of CPB and the dose of total heparin (ml) in each patient. The value of heparin dose response ranged 120-390 (mean 228) IU/kg. The ratio between protamine dose and heparin dose varied 0.11-0.99 (mean 0.55). There was a statistically significant correlation between the duration of CPB and this ratio (r = -0.51, n = 45, p = 0.0005). From the standpoint of variances in the value of heparin dose response, conventional way of the heparin administration according to the patient's body weight alone may cause inadequacy of anticoagulation during CPB. A dose of protamine determined by Hepcon device that is smaller than a conventional dose of protamine prevents inadvertent overdose and, therefore, can reduce the adverse effects excessive protamine has.

[Cerebral oxygenation during non-blood prime cardiopulmonary bypass in congenital heart surgery]

To analyze oxygen delivery to the brain and cerebral cellular oxygenation during non-blood prime and blood prime cardiopulmonary bypass (CPB), 22 patients undergoing cardiac surgery with CPB were studied by near infrared spectroscopy (NIRS) monitor (NIRO 500, Hamamatsu Photonics). NIRS can assess continuously cytochrome oxidase (Cyt.aa 3) which is the terminal enzyme of the intramitochondrial respiratory chain. Patients were grouped according to conditions of CPB management: one group underwent repair with non-blood prime (group A, n = 12); the second group underwent with blood prime (group B, n = 10). Body weights ranged from 5.5 kg to 58 kg in group A, and 2.9 kg to 16 kg respectively. CPB was maintained at flow rates between 100 to 150 ml/kg/min. and the acid-base management strategy was alpha stat in all patients. No neurological complication was observed. NIRS date were expressed as changes from baseline where cannulation was prepared. The lowest value of Cyt.aa 3 was -2.7 +/- 0.7 mumol/l in the group A, and -3.9 +/- 1.0 mumol/l in the group B. From the standpoint of changes in Cyt.aa 3, non-blood prime cases we studied were speculated to be within a safety limit. In order to define the definite safety limits, however, further studies including the reduction velocity of Cyt.aa 3 signal as well as the absolute value of the lowest Cyt.aa 3 concentration are required.

[Pulmonary outflow tract reconstruction with autologous tissue during the Ross procedure: right ventricular characteristics in mid-term follow-up]

BACKGROUND

The Ross procedure requires the interposition of prosthetic or homograft extracardiac conduits to establish ventricle-pulmonary artery connection (RV-PA). These materials usually require multiple reoperations because of conduit failure. To avoid the re-replacement of currently available conduits, usage of autologous tissue may be preferable to reconstruct RV-PA connection during the Ross procedure, especially in the pediatric age group.

METHOD

Ten patients (mean age 8.7 years, range 2-23) with congenital aortic valve disease underwent the Ross procedure between June, 1996 and July, 1998. To establish RV-PA continuity, autologous aortic wall including aortic valve with a gusset of pericardial tissue was used in six patients, rolled pericardial conduit with fresh pericardial bicuspid valve in three and one direct anastomosis of pulmonary posterior wall onto the right ventricle with a fresh pericardial monocusp valved patch. All patient's postoperative courses were uneventful. All patients were followed up (mean follow-up period: 21.6 +/- 6.6 months) and postoperative right ventricular characteristics, cardio-thoracic ratio (CTR) on chest X-ray and pulmonary valve function were evaluated.

RESULTS

Postoperative right ventricular end-diastolic volume, right ventricular ejection fraction and right ventricular end-diastolic pressure did not change significantly (RVEDV: 128 to 113% of normal, RVEF: 56.4 to 51.5%, RVEDP: 5.9 to 10.1 mmHg). Pulmonary regurgitation during follow-up was mild in six patients and moderate in four. However, CTR decreased significantly over time (preop.: 56.5% postop.: 58.5%, late period: 53.4%).

CONCLUSION

Our results support the concept of the reconstruction of pulmonary outflow tract without foreign materials during the Ross procedure. Longer follow-up are necessary to define the possible limitation of this technique.

Utility of near-infrared spectroscopic measurements during deep hypothermic circulatory arrest

BACKGROUND

Near-infrared spectroscopy (NIRS) is used to monitor cerebral oxygenation during cardiac surgery. However, interpretation of the signals is controversial. The aim of the study was to determine which NIRS variable best correlated with brain damage as assessed by animal behavior and neurohistologic score and to compare the accuracy of NIRS and magnetic resonance spectroscopy (MRS) in predicting brain injury.

METHODS

Forty 5-week-old piglets underwent 60 minutes of deep hypothermic circulatory arrest (DHCA) at 15 degrees C. Changes in brain adenosine triphosphate (ATP), phosphocreatine (PCr), and intracellular pH (pHi) were determined by MRS and correlated to changes in oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), and oxidized cytochrome a,a3 (CytOx) NIRS signals. Brains were fixed on day 4 and examined using a neurohistologic score.

RESULTS

Reductions in CytOx and HbO2 values were correlated closely with decreases in ATP, PCr, and pHi. The changes in CytOx and PCr showed the strongest correlation (r = 0.623). Maximal CytOx reduction during DHCA of more than -25 microM * differential pathlength factor (DPF) predicted brain damage with a sensitivity of 100% and a specificity of 75%. The histologic score was also correlated with a decrease in ATP (r = -0.52 for CytOx; r = -0.32 for ATP); HbO2, PCr, and pHi showed no correlations.

CONCLUSIONS

Reduction in CytOx correlates with decreased brain energy state and predicts histologic brain injury after DHCA with a high sensitivity. These data suggest that the level of CytOx could be a very important predictor of brain damage during DHCA.

Oxygenation strategy and neurologic damage after deep hypothermic circulatory arrest. I. Gaseous microemboli

OBJECTIVES

Recent studies suggest that myocardial reperfusion injury is exacerbated by free radicals when pure oxygen is used during cardiopulmonary bypass. Partial replacement of the oxygenator gas mixture with nitrogen, however, such as has already been adopted clinically in many centers, could increase the risk of gaseous nitrogen microembolus formation and therefore of brain damage because of the low solubility of nitrogen, particularly under conditions of hypothermia.

METHODS

Ten 7- to 10-kg piglets were cooled for 30 minutes to 15 degrees C on cardiopulmonary bypass and then rewarmed for 40 minutes to 37 degrees C. In 5 piglets cardiopulmonary bypass was normoxic and in 5 it was hyperoxic. In each group 3 bubble oxygenators without arterial filters and 2 membrane oxygenators with filters were used. Cerebral microemboli were monitored continuously by carotid Doppler ultrasonography (8 MHz) and intermittently by fluorescence retinography.

RESULTS

Embolus count was greater with lower rectal temperature (P <.001), use of a bubble oxygenator (P <.001), and lower oxygen concentration (P =.021) but was not affected by the temperature gradient between blood and body during cooling or rewarming.

CONCLUSIONS

Gaseous microemboli are increased with normoxic perfusion, but this is only important if a bubble oxygenator without a filter is used.

Oxygenation strategy and neurologic damage after deep hypothermic circulatory arrest. II. hypoxic versus free radical injury

OBJECTIVES

Laboratory studies suggest that myocardial reperfusion injury is exacerbated by free radicals when pure oxygen is used during cardiopulmonary bypass. In phase I of this study we demonstrated that normoxic perfusion during cardiopulmonary bypass does not increase the risk of microembolic brain injury so long as a membrane oxygenator with an arterial filter is used. In phase II of this study we studied the hypothesis that normoxic perfusion increases the risk of hypoxic brain injury after deep hypothermia with circulatory arrest.

METHODS

With membrane oxygenators with arterial filters, 10 piglets (8-10 kg) underwent 120 minutes of deep hypothermia and circulatory arrest at 15 degrees C, were rewarmed to 37 degrees C, and were weaned from bypass. In 5 piglets normoxia (PaO2 64-181 mm Hg) was used during cardiopulmonary bypass and in 5 hyperoxia (PaO2 400-900 mm Hg) was used. After 6 hours of reperfusion the brain was fixed for histologic evaluation. Near-infrared spectroscopy was used to monitor cerebral oxyhemoglobin and oxidized cytochrome a,a3 concentrations.

RESULTS

Histologic examination revealed a significant increase in brain damage in the normoxia group (score 12.4 versus 8.6, P =.01), especially in the neocortex and hippocampal regions. Cytochrome a,a 3 and oxyhemoglobin concentrations tended to be lower during deep hypothermia and circulatory arrest in the normoxia group (P =.16).

CONCLUSIONS

In the setting of prolonged deep hypothermia and circulatory arrest with membrane oxygenators, normoxic cardiopulmonary bypass significantly increases histologically graded brain damage with respect to hyperoxic cardiopulmonary bypass. Near-infrared spectroscopy suggests that the mechanism is hypoxic injury, which presumably overwhelms any injury caused by increased oxygen free radicals.

A novel sialyl Lewis X analog attenuates cerebral injury after deep hypothermic circulatory arrest

BACKGROUND

The initial step in the inflammatory process, which can be initiated by cardiopulmonary bypass and by ischemia/reperfusion, is mediated by interactions between selectins on endothelial cells and on neutrophils. We studied the effects of selectin blockade using a novel Sialyl Lewis X analog (CY-1503) on recovery after deep hypothermic circulatory arrest in a piglet model.

METHODS

Twelve Yorkshire piglets were subjected to cardiopulmonary bypass, 30 minutes of cooling, 100 minutes of circulatory arrest at 15 degrees C, and 40 minutes of rewarming. Five animals received a bolus of 60 mg/kg of CY-1503 and an infusion (3 mg/kg per hour) for 24 hours from reperfusion (group O), and 7 randomly selected control piglets received saline solution (group C). Body weight and total body water content were evaluated 3 hours and 24 hours after reperfusion by a bio-impedance technique. Neurologic recovery of animals was evaluated daily by neurologic deficit score (0 = normal, 500 = brain death) and overall performance categories (1 = normal, 5 = brain death). The brain was fixed in situ on the fourth postoperative day and examined by histologic score (0 = normal, 5+ = necrosis) in a blinded fashion.

RESULTS

Two of 7 animals in group C died. The neurologic deficit score was significantly lower in group O than in group C (postoperative day 1, P <.001; postoperative day 2, P =.02). The overall performance category was significantly lower in group O than in group C on postoperative day 2 (P =.01). Percentage total body water after cardiopulmonary bypass was significantly higher in group C than in group O (P =.03). Histologic score tended to be higher in group C than in group O, but this difference did not reach statistical significance (group O = 0.5 +/- 0.7; group C = 1.3 +/- 1.off

CONCLUSION

Blockade of selectin adhesion molecules by saturation with a Sialyl Lewisx analog accelerates recovery after 100 minutes of deep hypothermic circulatory arrest in a piglet survival model.

Effects of a monoclonal antibody to P-selectin on recovery of neonatal lamb hearts after cold cardioplegic ischemia

BACKGROUND

The interaction between endothelium and leukocytes plays a crucial role in ischemia-reperfusion injury. P-selectin, which is expressed on activated endothelium, mediates the first step in leukocyte adherence to the endothelium. This study examined the effects of a monoclonal antibody (mAb) against P-selectin on the recovery of cardiac function and myocardial neutrophil infiltration after ischemia.

METHODS AND RESULTS

Thirteen blood-perfused, isolated neonatal lamb hearts underwent 2 hours of hypothermic cardioplegic arrest and 2 hours of reperfusion. Immediately before reperfusion, mAb to P-selectin was administered to the perfusate (15 micrograms/mL) in 6 hearts (group P-sel). In control (n = 7), the same volume of saline was added. Isovolumic left ventricular function and coronary blood flow were measured. At 2 hours after reperfusion, myocardial myeloperoxidase activity, an index of neutrophil accumulation, was assayed. At 30 minutes of reperfusion, hearts treated with mAb to P-selectin achieved significantly greater recovery of maximum developed pressure (70 +/- 4% in control versus 77 +/- 2% in group P-sel, P < 0.01), maximum positive first derivative of pressure (dP/dt) (64 +/- 7% in control versus 73 +/- 5% in group P-sel, P < 0.05), and maximum negative dP/dt (61 +/- 6% in control versus 70 +/- 6% in group P-sel, P < 0.05) compared with control. Percent baseline of coronary blood flow was also significantly increased in group P-sel (135 +/- 40% in control versus 205 +/- 43% in group P-sel, P < 0.05). Myocardial myeloperoxidase activity was significantly lower (P < 0.05) in group P-sel (4.7 +/- 3.2) versus control (16.0 +/- 10.1). (Units are change in absorbance/min/g tissue.)

CONCLUSIONS

The functional blockade of P-selectin resulted in better recovery of cardiac function and attenuated neutrophil accumulation during early reperfusion. Strategies to block P-selectin mediated neutrophil adherence may have clinical application in improving myocardial function at early reperfusion.

High-volume continuous hemofiltration during cardiopulmonary bypass attenuates pulmonary dysfunction in neonatal lambs after deep hypothermic circulatory arrest

BACKGROUND

Cardiopulmonary bypass (CPB) induces an inflammatory reaction that activates neutrophils and releases free radicals in tissue. Ischemia-reperfusion further aggravates inflammation. Hemofiltration (HF) could potentially remove inflammatory mediators and reduce injury. This study assessed the effect of continuous high-volume HF during CPB on systemic edema formation and pulmonary function after deep hypothermic circulatory arrest (DHCA).

METHODS AND RESULTS

Anesthetized lambs (n = 16) underwent CPB with systemic cooling (40 minutes), DHCA (120 minutes at 18 degrees C), and rewarming (40 minutes). All animals were weaned from CPB and observed for 3 hours after reperfusion. Continuous HF was used in 8 lambs at a flow rate of 300 mL/kg per hour throughout CPB, simultaneously replacing hemofiltration volume with a balanced salt solution (HF group). In 8 control animals, no hemofiltration was performed. Hematocrit remained at 23% to 25% during the experiment in both groups. Pulmonary vascular resistance (PVR), lung dynamic compliance (Cdyn), alveolar-arterial oxygen difference (AaDO2), and total body water content (bioimpedance) were measured. Malondialdehyde (MDA), a product of lipid peroxidation, was assayed in lung tissue. Percent increase of body water content at 180 minutes of reperfusion was significantly lower in the HF group than in control (132 +/- 2% vs 152 +/- 5%, P < 0.005). There was less of a rise in PVR compared with baseline at 180 minutes of reperfusion in the HF group than in control (131 +/- 8% vs 238 +/- 26%, P < 0.005). In addition, percent recovery of Cdyn and AaDO2 in the HF group was preserved significantly (respectively, P < 0.05) 2 hours after reperfusion than in the control group. Lung tissue MDA in the HF group (46.2 +/- 12.6 vs 65.3 +/- 17.1 nmol/L per gram of tissue, P < 0.05) was significantly lower than in the control group.

CONCLUSIONS

High-volume, continuous hemofiltration during CPB attenuates systemic edema formation, pulmonary hypertension, the extent of lung dysfunction, and depression of cardiac output and reduces free radical-mediated tissue injury after CPB with DHCA. This technique may have a clinical application to reduce the morbidity rate of CPB.

Near-infrared spectrophotometry of the brain in cardiovascular surgery

Neuropsychological and neurological deficits are still major causes of mortality and morbidity after cardiac operations and are thought to be caused by embolism and cerebral hypoxia. Near-infrared spectrophotometry (NIRS) is a promising method for non-invasive monitoring of cerebral oxygenation and hemodynamics. Different devices provide information on changes of oxygenated (HbO2) and deoxygenated hemoglobin (Hb), oxidized cytochrome aa3 (CytOx) or regional oxygen saturation (rSO2). NIRS has been applied to patients during adult and pediatric cardiovascular surgery with and without deep hypothermic circulatory arrest (DHCA). In most of the studies, significant changes in cerebral oxygenation were detected by NIRS. NIRS measurements were influenced by the cerebral oxygen metabolism and the operative management. However, clinical, experimental, and theoretical issues raise doubts as to the clinical relevance of the hemoglobin saturation (HbO2, Hb, rSO2 signals) during hypothermia and alkalosis, because the oxygen affinity of hemoglobin increases and a high saturation might simply reflect the inadequate oxygen transport into cells. In contrast, recent experiments have proved a high correlation between the CytOx signal and the MRS parameters nucleoside triphosphate and phosphocreatine. Histological damage was significantly related to the lowest CytOx value; in a clinical study it predicted impaired neuropsychological outcome. Therefore, the CytOx signal is of great interest for future studies. NIRS must prove its ability to diagnose cerebral hypoxia consistently during cardiac surgery in a large patient study before this method is brought into routine clinical practice. Absolute quantification and definitions of critical oxygenation margins will be helpful for this goal.

Effects of oncotic pressure and hematocrit on outcome after hypothermic circulatory arrest

BACKGROUND

A recent study found that a higher-perfusate hematocrit was associated with improved neurologic recovery after deep hypothermic circulatory arrest. The current study examined the relative contributions of oxygen delivery and colloid oncotic pressure to this result, as well as the efficacy of different colloidal agents and modified ultrafiltration.

METHODS

Twenty-six piglets were randomized into five groups (n = 5 or 6 animals per group): control group 1--blood and crystalloid prime, hematocrit of 20%; group 2--blood and hetastarch prime, hematocrit of 20%; group 3--blood and pentafraction prime, hematocrit of 20%; group 4--blood and crystalloid prime with 10 minutes of modified ultrafiltration; group 5--whole blood prime, hematocrit of 30%. All groups underwent 60 minutes of deep hypothermic circulatory arrest at 15 degrees C.

RESULTS

Groups 2 and 3 showed less body weight gain (analysis of variance, p = 0.001; group 2 versus group 1, p = 0.0009; group 3 versus group 1, p = 0.0009) and body water content after cardiopulmonary bypass (analysis of variance, p = 0.001; group 2 versus group 1, p = 0.003; group 3 versus group 1, p = 0.013). Group 5 showed more rapid recovery of phosphocreatine and intracellular acidosis, as measured by magnetic resonance spectroscopy, during rewarming than group 1 did (phosphocreatine, p = 0.0329; intracellular acidosis, p = 0.0462). Group 3 also showed accelerated recovery of intracellular acidosis (p = 0.0411). Cytochrome a,a3 recovery, determined by near-infrared spectroscopy, was significantly better in group 5 than in group 1 and worse in group 2 than in group 1 after rewarming. The neurologic deficit score and overall performance category score were best in group 5 (neurologic deficit score, p = 0.012; overall performance category score, p = 0.046) on the first postoperative day. Group 3 also had a better overall performance category score than group 1 did (p = 0.0068). Only group 1 and 2 animals showed histologic damage.

CONCLUSIONS

Both higher hematocrit and higher colloid oncotic pressure with pentafraction improve cerebral recovery after deep hypothermic circulatory arrest. The higher hematocrit improves cerebral oxygen delivery but does not reduce total body edema. Modified ultrafiltration after cardiopulmonary bypass is less effective than having a higher initial prime hematocrit or colloid oncotic pressure.

Tissue engineering of cardiovascular structures

Congenital and acquired diseases of the heart valves and great arteries are leading causes of morbidity and mortality. Current prosthetic or bioprosthetic replacement devices are imperfect and subject patients to one or more ongoing risks including thrombosis, limited durability, increased susceptibility to infection, and need for reoperations due to lack of growth. Tissue engineering (TE) is a new discipline that offers the potential to create replacement structures from autologous cells and biodegradable polymers. Because TE constructs contain living cells, they may have the potential for growth and self-repair and remodeling. Cardiac valve leaflets and large conduit arteries have been made with the TE approach. These TE structures have functioned in the pulmonary circulation of growing lambs for up to 4 months and have demonstrated 1) structural organization to resemble normal valve and artery, 2) satisfactory physiologic function, 3) lack of thrombus formation, and 4) growth.

Evaluation of a pulsatile pediatric ventricular assist device in an acute right heart failure model

BACKGROUND

The development of pulsatile ventricular assist devices for children has been limited mainly by size constraints. The purpose of this study was to evaluate the MEDOS trileaflet-valved, pulsatile, pediatric right ventricular assist device (stroke volume = 9 mL) in a neonatal lamb model of acute right ventricular failure.

METHODS

Right ventricular failure was induced in ten 3-week-old lambs (8.6 kg) by right ventriculotomy and disruption of the tricuspid valve. Control group 1 (n = 5) had no mechanical support whereas experimental group 2 (n = 5) had right ventricular assist device support for 6 hours. The following hemodynamic parameters were measured in all animals: heart rate and right atrial, pulmonary arterial, left atrial, and systemic arterial pressures. Cardiac output was measured by an electromagnetic flow probe placed on the pulmonary artery.

RESULTS

All results are expressed as mean +/- standard deviation and analyzed by Student's t test. A p value less than 0.05 was considered statistically significant. Base-line measurements were not significantly different between groups and included systemic arterial pressure, 80.6 +/- 12.7 mm Hg; right atrial pressure, 4.6 +/- 1.6 mm Hg; mean pulmonary arterial pressure, 15.6 +/- 4.2 mm Hg; left atrial pressure, 4.8 +/- 0.8 mm Hg; and cardiac output, 1.4 +/- 0.2 L/min. Right ventricular injury produced hemodynamics compatible with right ventricular failure in both groups: mean systemic arterial pressure, 38.8 +/- 10.4 mm Hg; right atrial pressure, 16.8 +/- 2.3 mm Hg; left atrial pressure, 1.4 +/- 0.5 mm Hg; and cardiac output, 0.6 +/- 0.1 L/min. All group 1 animals died at a mean of 71.4 +/- 9.4 minutes after the operation. All group 2 animals survived the duration of study. Hemodynamic parameters were recorded at 2, 4, and 6 hours on and off pump, and were significantly improved at all time points: mean systemic arterial pressure, 68.0 +/- 13.0 mm Hg; right atrial pressure, 8.2 +/- 2.3 mm Hg; left atrial pressure, 6.4 +/- 2.1 mm Hg; and cardiac output, 1.0 +/- 0.2 L/min.

CONCLUSIONS

The results demonstrate the successful creation of a right ventricular failure model and its salvage by a miniaturized, pulsatile right ventricular assist device. The small size of this device makes its use possible even in small neonates.

Higher hematocrit improves cerebral outcome after deep hypothermic circulatory arrest

BACKGROUND

Various degrees of hemodilution are currently in clinical use during deep hypothermic circulatory arrest to counteract deleterious rheologic effects linked with brain injury by previous reports.

MATERIAL AND METHODS

Seventeen piglets were randomly assigned to three groups. Group I piglets (n = 7) received colloid and crystalloid prime (hematocrit < 10%), group II piglets (n = 5) received blood and crystalloid prime (hematocrit 20%), group III piglets (n = 5) received blood prime (hematocrit 30%). All groups underwent 60 minutes of deep hypothermic circulatory arrest at 15 degrees C with continuous magnetic resonance spectroscopy and near-infrared spectroscopy Neurologic recovery was evaluated for 4 days (neurologic deficit score 0, normal, to 500, brain death; overall performance category 1, normal, to 5, brain death). Neurohistologic score (0, normal, to 5+, necrosis) was assessed after the animals were euthanized on day 4.

RESULTS

Group I had significant loss of phosphocreatine and intracellular acidosis during early cooling (phosphocreatine in group I, 86.3% +/- 26.8%; group II, 117.3% +/- 8.6%; group III, 110.9% +/- 2.68%; p = 0.0008; intracellular pH in group I, 6.95 +/- 0.18; group II, 7.28 +/- 0.04; group III, 7.49 +/- 0.04; p = 0.0048). Final recovery was the same for all groups. Cytochrome aa3 was more reduced in group I during deep hypothermic circulatory arrest than in either of the other groups (group I, -43.6 +/- 2.6; group II, -16.0 +/- 5.2; group III, 1.3 +/= 3.1; p < 0.0001). Neurologic deficit score was best preserved in group III (p < 0.05 group II vs group III) on the first postoperative day, although this difference diminished with time and all animals were neurologically normal after 4 days. Histologic assessment was worst among group I in neocortex area (group I, 1.33 +/- 0.3; group II, 0.22 +/- 0.1; group III, 0.40 +/- 0.2, p < 0.05, group I vs group II; p = 0.0287, group I vs group III).

CONCLUSION

Extreme hemodilution during cardiopulmonary bypass may cause inadequate oxygen delivery during early cooling. The higher hematocrit with a blood prime is associated with improved cerebral recovery after deep hypothermic circulatory arrest.

Intermittent whole-body perfusion with "somatoplegia' versus blood perfusate to extend duration of circulatory arrest

BACKGROUND

Continuous whole-body perfusion for > 3 hours with a cold asanguineous blood substitute, hypothermosol (HTS) solution, has been reported to preserve organ function. We used this solution in a survival animal model to evaluate its possible application in extending the safe duration of deep hypothermic circulatory arrest (DHCA).

METHODS AND RESULTS

Fifteen piglets were placed on cardiopulmonary bypass (CPB), were cooled to a nasopharyngeal temperature of 15 degrees C, and underwent 100 minutes of DHCA. Control animals (group C, n = 5) had uninterrupted DHCA, group HTS animals were perfused with maintenance HTS for 5 minutes every 25 minutes during DHCA (n = 5), and group B animals were intermittently perfused as for group HTS with the blood in the bypass circuit (n = 5). Cerebral oxygenation was assessed with near-infrared spectroscopy throughout CPB and DHCA. Animals were allowed to recover after CPB and underwent daily neurobehavioral evaluation by the neurological deficit score (NDS: 0, normal; 500, brain death) and overall performance categories (OPC: 1, normal; 5, brain death). Blood samples were drawn on postoperative day (POD) 1 for selected biochemistry analysis. On POD 4, the brain of each animal was perfusion-fixed for histological evaluation, and a neurohistological score (NHS: 0, normal; 5+, necrosis) was assigned for the degree of neuronal injury. All animals except one from group HTS survived surgery. Mean perfusion pressures were significantly elevated in group B compared with group C and group HTS during the rewarming phase (P < .05). The HbO2 signal increased in all groups during the cooling phase of CPB and remained significantly above baseline only in group B during DHCA (P < .05). SGOT, LDH, ALP, and CPK levels on POD 1 were elevated above baseline in all groups. The increase in SGOT and ALP was significantly greater in group HTS than in the other groups (P < .02). The NDS was lower in group B on each postoperative evaluation, being significant relative to group C and group HTS on POD 1 (P < .05) and significantly lower than group C on POD 2 (P < .05). The OPC score was significantly lower in group B than in group C and group HTS on POD 2 (P < .05) and significantly lower than in group C on PODs 3 and 4 (P < .05). The NHS was lower in group B than in the other 2 groups, being significant relative to group C in the neocortex (P < .007).

CONCLUSIONS

Intermittent whole-body asanguineous perfusion with hypothermosol solution does not extend cerebral protection in a porcine survivor model of DHCA. Neurobehavioral and histological outcomes are improved in animals receiving intermittent blood perfusion during prolonged DHCA.

Blockade of selectin-mediated leukocyte adhesion improves postischemic function in lamb hearts

BACKGROUND

Leukocyte-endothelial interactions appear to have a important role in ischemia/reperfusion injury and are mediated by specific leukocyte and endothelial adhesion molecules. The selectins are adhesion molecules found on leukocytes (L-selectin) and endothelium (P and E selectin) that bind to oligosaccharide ligands containing fucose and sialic acid to mediate leukocyte rolling on the endothelium. Fucoidin is a nontoxic sulfated fucose oligosaccharide derived from seaweed that blocks the selectins.

METHODS

We tested the effects of fucoidin in an isolated blood-perfused neonatal (age range, 3 to 7 days; mean age, 4.3 days) lamb heart model undergoing 2 hours of cold cardioplegic ischemia. In group F (n = 8) fucoidin (30 mg/L) was added at initial reperfusion. Group C (n = 9) received only cardioplegia with no reperfusion intervention. Isovolumic maximum developed pressure and the maximum positive and negative first derivatives of pressure were measured using a catheter-tip transducer in an intraventricular balloon before ischemia and at 30 minutes of reperfusion. Coronary blood flow, myocardial oxygen consumption, and white blood cell counts in the circulating blood were also measured.

RESULTS

Percent recoveries of baseline maximum developed pressure and maximum positive and negative first derivatives of pressure in group F (86% +/- 5%, 81% +/- 10%, and 74% +/- 8%, respectively; mean +/- standard deviation) were higher than in group C (77% +/- 5%, 70% +/- 9%, and 65% +/- 6%; p < 0.05). Group F postischemic coronary blood flow was greater (190% +/- 35%) than in group C (102% +/- 10%; p < 0.05). Recovery of myocardial oxygen consumption in group F (86% +/- 14%) was greater than group C (72% +/- 11%; p < 0.05). Postischemic white blood cell count in group F (88% +/- 4%) was greater than in group C (81% +/- 5%; p < 0.05).

CONCLUSIONS

Selectin blockade with fucoidin resulted in better recovery of left ventricular function, coronary blood flow, and myocardial oxygen consumption after cold ischemia, despite a higher circulating white blood cell count. These data support the hypothesis that endothelial-leukocyte interactions play an important role in ischemia/reperfusion and suggest that selectin blockade may be a useful therapeutic strategy.

[Surgical treatment of transposition of the great arteries with intact ventricular septum associated with left ventricular outflow obstruction]

Thirteen patients have undergone surgical treatment for transposition of the great arteries (TGA) with intact ventricular septum (IVS) associated with left ventricular outflow obstruction (LVOTO) in our institute. Ages at operation ranged from three months to six years (mean 9.2 +/- 4.7 months). Of these patients, seven had dynamic type LVOTO (group I), and six had organic LVOTO (group II). Preoperative left ventricular end-diastolic volume was significantly smaller in group II (78 +/- 13% of normal) than control group (135 +/- 53% of normal). Preoperative pressure gradient between the pulmonary artery and left ventricle was significantly greater in group II (55.8 +/- 3.2 mmHg) than group I (35.2 +/- 3.9 mmHg). In group I, II patients underwent two-stage ASO, the other 5 patients underwent Senning operation. The reason for the Senning operation were era before introduction of ASO in our institute (1983) or unsuccessful training of the left ventricle. In group II, all but one patient underwent Senning operation, the other underwent a successful Fontan operation with Damus anastomosis because of too small left ventricle (LVEDV: 49% of normal). Techniques to correct LVOTO at the definitive operation included ventriculotomy (n = 4) and pulmonary valvotomy (n = 2). One patients in group II underwent a Fontan operation with Damus anastomosis due to an underdeveloped left ventricle (LVEDV: 49% of normal). There was no early or late death. The postoperative pressure gradients disappeared or reduced to trivial levels in all patients. At present no LVOTO has developed in any of the patients.

[Reoperations of extracardiac valved conduit for congenital cardiac defects]

Fifteen of 223 patients who have had extracardiac conduit repair at the Heart Institute of Japan from January, 1970, to April, 1991, have required conduits replacement because of conduit obstruction or infection. The main causes of obstruction were degeneration of the prosthetic valve and proliferative pseudo-intima in the conduit. The interval between initial conduit repair and conduit replacement was 2.2 to 18.3 years (mean 10.5 +/- 4.4). The average pressure gradient through the conduit decreased from 74.7 +/- 42.0 mmHg preoperatively to 12.3 +/- 7.1 mmHg postoperatively (p < 0.05). There was no early and late death. We concluded that xeno-pericardial roll conduits were superior to others and that conduit replacement procedure following the extracardiac conduit repair was safe and effective.

[Successful two-staged Jatene operation for severe right ventricular dysfunction and tricuspid regurgitation after Senning operation--a case report]

We report a seven-year-old boy who underwent a successful Jatene procedure seven years after Senning procedure. The modified Senning operation was performed for the treatment of transposition of the great arteries with intact ventricular septum at three years of age. However, he gradually showed the progressive right ventricular failure with tricuspid regurgitation after operation. When he was referred to our hospital, he was in severe right ventricular failure and showed massive tricuspid regurgitation simultaneously with the moderate degree of left ventricular failure. Staged pulmonary artery banding was applied to prepare the left ventricle for Jatene procedure in spite of the presence of left ventricular failure. The systolic pressure ratio of left ventricle to right ventricle was elevated to 0.91 by this banding although the left ventricular ejection fraction decreased from 43% to 30%. And Jatene procedure was successfully performed after three months of preparation period. Catheterization study after Jatene procedure revealed improved right and left ventricular functions with decrease of tricuspid regurgitation. We conclude that the Jatene procedure should be an ideal alternative in patient with right ventricular failure and/or tricuspid regurgitation after an atrial switch operation; the left ventricle could be prepared by an effective pulmonary banding in most instances.

[Valvuloplasty for mitral regurgitation associated with acromegaly: report of a case]

A 67-year-old female with mitral regurgitation associated with acromegaly was admitted to our hospital. The cause of MR was torn chordae of posterior leaflet of the mitral valve. A prolapse part of the posterior leaflet was resected and sutured by McGoon's method. Annuloplasty was performed by Kay's method. Postoperative course was uneventful. She recovered well after the operation.

[Successful correction of incomplete endocardial cushion defects in an elderly patient]

We have experienced surgical correction of incomplete ECD in a 66-year-old female patient. This is the oldest case in Japanese literatures. Preoperative examination showed mild mitral regurgitation, interatrial shunt (L-R 52%) and moderate pulmonary hypertension (Pp/Ps 0.48). The correction consisted of valvuloplasty of mitral valve and patch closure of ostium primum. The postoperative course was uneventful. The postoperative catheterization showed improved cardiac function.