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In the field of congenital heart surgery, tissue-engineered vascular grafts (TEVGs) are a promising alternative to traditionally used synthetic grafts. Our group has pioneered the use of TEVGs as a conduit between the inferior vena cava and the pulmonary arteries in the Fontan operation. The natural history of graft remodeling and its effect on hemodynamic performance has not been well characterized. In this study, we provide a detailed analysis of the first U.S. clinical trial evaluating TEVGs in the treatment of congenital heart disease. We show two distinct phases of graft remodeling: an early phase distinguished by rapid changes in graft geometry and a second phase of sustained growth and decreased graft stiffness. Using clinically informed and patient-specific computational fluid dynamics (CFD) simulations, we demonstrate how changes to TEVG geometry, thickness, and stiffness affect patient hemodynamics. We show that metrics of patient hemodynamics remain within normal ranges despite clinically observed levels of graft narrowing. These insights strengthen the continued clinical evaluation of this technology while supporting recent indications that reversible graft narrowing can be well tolerated, thus suggesting caution before intervening clinically., (© 2021. The Author(s).)

Aortic root dilatation is a well-known complication in patients with congenital aortic valve malformation, tetralogy of Fallot, or a double outlet right ventricle. We report two rare patients who underwent composite graft replacement of the aortic root with a mechanical valve, the so-called Bentall-type operation, after Fontan completion. The pathological examination on the resected aortic wall revealed mucoid degeneration in tunica media and elastic fiber fragmentation. Our report emphasizes the need for close observation of these patients over a long-term period.

We previously developed and validated a murine model for investigating neotissue formation in tissue-engineered vascular grafts (TEVGs). Herein, we present the first longitudinal assessment of both the microstructural composition and the mechanical properties of a TEVG through the process of neovessel formation (total scaffold degradation). We show that when (poly)glycolic acid-based biodegradable scaffolds were used as inferior vena cava interposition grafts in mice, the evolving neovessel developed biaxial properties that approached those of the native vein within 24 weeks of implantation. Further, we found that these changes in biaxial properties related temporally to extracellular matrix production and remodeling, including deposition of collagen (types I and III), elastic fibers (elastin and fibrillin-1), and glycosaminoglycans in addition to changes in matrix metalloproteinase (MMP)-2 and -9 activity. Improving our understanding of the mechanobiological principles underlying vascular neotissue formation in TEVGs holds great promise for improving the design of TEVGs and enabling us to continue the translation of this technology from the bench to the clinic.

A major limitation of tissue engineering research is the lack of noninvasive monitoring techniques for observations of dynamic changes in single tissue-engineered constructs. We use cellular magnetic resonance imaging (MRI) to track the fate of cells seeded onto functional tissue-engineered vascular grafts (TEVGs) through serial imaging. After in vitro optimization, murine macrophages were labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles and seeded onto scaffolds that were surgically implanted as inferior vena cava interposition grafts in SCID/bg mice. Serial MRI showed the transverse relaxation times (T(2)) were significantly lower immediately following implantation of USPIO-labeled scaffolds (T(2) = 44 ± 6.8 vs. 71 ± 10.2 ms) but increased rapidly at 2 h to values identical to control implants seeded with unlabeled macrophages (T(2) = 63 ± 12 vs. 63 ± 14 ms). This strongly indicates the rapid loss of seeded cells from the scaffolds, a finding verified using Prussian blue staining for iron containing macrophages on explanted TEVGs. Our results support a novel paradigm where seeded cells are rapidly lost from implanted scaffolds instead of developing into cells of the neovessel, as traditionally thought. Our findings confirm and validate this paradigm shift while demonstrating the first successful application of noninvasive MRI for serial study of cellular-level processes in tissue engineering.

Introduction: We created the first tissue-engineered vascular graft (TEVG) to be successfully used in humans. The TEVG is made by seeding autologous bone marrow-derived mononuclear cells (BM-MNCs) onto a biodegradable tubular scaffold fabricated from polyglycolic-acid mesh coated with a 50:50 copolymer of poly-L-lactide and-ɛ-caprolactone. In the initial clinical study, the BM-MNCs were isolated using a Ficoll density centrifugation method. Use of this cell isolation technique is problematic in that it is performed using an open system and therefore is susceptible to contamination. As a first step toward creating a closed system for assembling a TEVG, we evaluated the use of a filter-based method for isolating BM-MNCs and compared it to density centrifugation in Ficoll., Methods: BM-MNCs were isolated from human BM using density centrifugation in Ficoll or a filter-based method. BM-MNCs were seeded onto biodegradable tubular scaffold and incubated for 24 h before implantation. The TEVG were implanted as inferior vena cava interposition grafts in SCID/bg mice (n=24) using microsurgical technique. Grafts were followed with ultrasonography and computed tomography-angiography. Ten weeks after implantation the TEVG were explanted and examined using histology and immunohistochemistry., Results: Both methods isolated similar number of cells (Ficoll: 8.5±6.6×10(6)/mL, Filter: 6.6±3.5×10(6)/mL; p=0.686) with similar viability as assayed using fluorescence-activated cell sorting (FACS) (Ficoll: 97.0%±1.5%, Filter: 95.9%±3.0%; p=0.339). FACS analysis demonstrated that the fraction of lymphocytes and monocytes to total cells was lower in the filter group (CD4 in Ficoll: 8.9%±1.1%, CD4 in Filter: 3.5%±0.8%; p=0.002, CD8 in Ficoll: 9.4%±2.1%, CD8 in Filter: 3.9%±1.4%; p=0.021, Monocyte in Ficoll: 6.9%±1.0%, Monocyte in Filter: 2.7%±1.0%; p=0.008), consistent with granulocyte contamination (Ficoll: 46.6±2.7×10(6)/mL, Filter: 58.1±5.2×10(6)/mL; p<0.001). The ratio of stem cells to BM-MNCs was comparable between groups. There were no statistically significant differences with regard to TEVG patency and morphology between groups. Both methods of cell isolation produced neovessels with similar histology., Conclusion: Filter-based BM-MNC isolation is comparable to BM-MNC isolation using density centrifugation in Ficoll for TEVG assembly. The filter-based cell isolation technique has the added advantage of the potential to create a closed disposable system., (© Mary Ann Liebert, Inc.)

We developed a tissue-engineered vascular graft composed of biodegradable scaffold seeded with autologous bone marrow-derived mononuclear cells (BMMCs) that is currently in clinical trial and developed analogous mouse models to study mechanisms of neovessel formation. We previously reported that seeded human BMMCs were rapidly lost after implantation into immunodeficient mice as host macrophages invaded the graft. As a consequence, the resulting neovessel was entirely of host cell origin. Here, we investigate the source of neotissue cells in syngeneic BMMC-seeded grafts, implanted into immunocompetent mouse recipients. We again find that seeded BMMCs are lost, declining to 0.02% at 14 d, concomitant with host macrophage invasion. In addition, we demonstrate using sex-mismatched chimeric hosts that bone marrow is not a significant source of endothelial or smooth muscle cells that comprise the neovessel. Furthermore, using composite grafts formed from seeded scaffold anastomosed to sex-mismatched natural vessel segments, we demonstrate that the adjacent vessel wall is the principal source of these endothelial and smooth muscle cells, forming 93% of proximal neotissue. These findings have important implications regarding fundamental mechanisms underlying neotissue formation; in this setting, the tissue-engineered construct functions by mobilizing the body's innate healing capabilities to "regenerate" neotissue from preexisting committed tissue cells.

Heparin is the routine anticoagulant for cardiopulmonary bypass, but complications due to heparin are often reported. This study assessed argatroban as an alternative to heparin. Normothermic cardiopulmonary bypass with hemodilution was performed for 2 h in 15 dogs (mean weight, 9.8 kg) randomly assigned to 3 groups of 5 each. The controls were given heparin 200 IU x kg(-1) before cardiopulmonary bypass; group A had argatroban infused continuously at a rate of 20 microg x kg(-1) x min(-1); group H/A had half doses of both heparin (100 IU x kg(-1)) and argatroban (10 microg x kg(-1) x min(-1)). Blood samples were collected at 5 time points during the experiment. Activated clotting time, hemoglobin level, platelet counts, and serum concentrations of fibrinogen, antithrombin III, and thrombin-antithrombin III complex were measured. The platelet count was reduced significantly, and the production of thrombin-antithrombin III complex was inhibited in group H/A. Activated clotting time remained <300 sec at all time points in group A, but it was maintained at approximately 400 sec in group H/A. Fibrinogen and antithrombin III levels were reduced to half in all groups after initiation of cardiopulmonary bypass. The simultaneous use of heparin and argatroban infusion might be useful for cardiopulmonary bypass with hemodilution.

Previous studies have revealed c-kit-positive (c-kit(+)) cardiac stem cells (CSCs) in the adult mammalian heart and these cells could be a suitable cell source for heart regeneration therapy. However, these cells have not been fully evaluated in terms of characterization and effect of long-term culture, which is necessary for their safe and optimal usage. Therefore, we isolated c-kit(+) CSCs from adult rat hearts to characterize these cells and investigate stability over long-term culture. We performed isolations of c-kit(+) CSCs 11 times and passaged them 40 times in a bulk culture system; we termed these cultures, bulk culture CSCs (CSC-BC). c-kit(+) CSCs expressed stemness genes and exhibited stem cell properties of single cell-derived clone formation, cardiosphere generation, and potential to differentiate into the three main cardiac lineages: cardiomyocyte, smooth muscle, and endothelial cells in vitro. Over long-term culture, some CSC-BC up-regulated GATA-4 expression, which resulted in enhanced cardiomyocyte differentiation, suggesting that the GATA-4 high c-kit(+) CSCs have potent cardiac regenerative potential. We also observed the spontaneous differentiation into cells other than cardiac lineages, such as adipocyte and skeletal myocyte. This effect of long-term culture on the c-kit(+) CSCs has not been previously reported. Interestingly, when c-kit(+) CSCs were co-cultured with adult rat cardiomyocytes, we found increased cardiomyocyte survival, and the growth factors, insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF), appeared to be responsible factors. The present study suggests that c-kit(+) CSCs have great therapeutic potential yet should be further investigated and optimized as a cell source for regenerative therapies prior to transplantation.

Left ventricular outflow tract obstruction in children is classified according to the site of the obstruction into a supra-aortic type, valvular type, and subaortic type (subaortic stenosis). Subaortic stenosis, in turn, is classified into two major subtypes, i.e., a discrete type, which accounts for most cases and a tunnel type, and one minor subtype, the accessory mitral tissue type, which is rare. Systolic anterior motion (SAM) is a phenomenon that is commonly observed in hypertrophic cardiomyopathy. We report a rare case of subaortic stenosis associated with SAM, which was caused by cleft anterior mitral leaflet and an accessory papillary muscle. Surgical treatment was successful, and there were no complications.

Dense adhesions in the retrosternal space make reoperations difficult in the field of cardiovascular surgery. Several substitutes for pericardium have been employed to prevent dense adhesions forming, but they have been unsatisfactory because of peel formation, calcification, and infection. To overcome these drawbacks, a novel biodegradable pericardial substitute was developed from gelatin obtained from specific-pathogen-free porcine skin and a bioabsorbable polyester mesh, which persists while the adhesion reaction occurs in the retrosternal space. A clinical pilot study of this gelatin sheet was carried out in patients scheduled to receive multistage cardiac surgery. From February 2003 to July 2004, the material was used in 5 patients aged 0.4 to 3.0 years. There were no complications related to the gelatin sheet. The effectiveness of the material was evaluated when the sternum was reopened 1.4 +/- 0.5 years later. It took 24.5 +/- 6.0 min for the resternotomy, and all surgeons who participated in the surgery rated the effectiveness of the gelatin sheet as "good". This anti-adhesive sheet prevented dense adhesions, suggesting that this material may be useful as a pericardial substitute for multistage pediatric cardiac surgery.

Objective: This study was to evaluate the efficacy of the hyaluronic acid (HA) bioabsorbable membrane combined use with both expanded-polytetrafluoroethylene (ePTFE) and autologous pericardium for preventing postoperative pericardial adhesions., Methods: The HA bioresorbable surgical membrane (Seprafilm, Genzyme, Cambridge, Mass) was used with either ePTFE or autologous pericardium in an experimental pericardial adhesion model. Twenty-four beagle dogs were classified as follows; Group A (n = 6): ePTFE only, Group B (n = 6): Seprafilm + ePTFE, Group C (n = 6): autologous pericardium only, Group D (n = 6): Seprafilm + autologous pericardium. Pericardial adhesions were evaluated at necropsy at 4, 8, and 12 weeks. The tenacity of adhesion was graded by macroscopic examination, and the adhesion tissue thickness was analyzed microscopically with an image processing program. The regeneration of mesothelial cells on neo-tissue fibrils were immunohistochemically studied., Results: In groups B and D, the adhesions were significant lower compared with those of control groups in the tenacity (Group A vs B: 2.5 +/- 0.55 vs 1.5 +/- 0.55, P < 0.05; Group C vs D: 3.2 +/- 0.75 vs 0.33 +/- 0.52, P < 0.01) and the tissue thickness (Group A vs B: 30.4 +/- 12.9 vs 10.3 +/- 4.42, P < 0.01; Group C vs D: 22.6 +/- 11.5 vs 4.96 +/- 4.87, P < 0.01). Immunohistochemically, a single layer of mesothelial cells were regenerated on the surface of neo-tissue fibrils in HA treated groups., Conclusion: The combined use of Seprafilm with either ePTFE or autologous pericardium effectively reduced the formation of pericardial adhesion.

Objective: Peripheral arterial disease (PAD) can have severe consequences on patient mortality and morbidity. In contrast to approaches using growth factor administration or isolated cell transplantation, we attempted to develop an alternative method for ischemic therapy using the transplantation of tissue engineered cell sheets with angiogenic potential., Methods and Results: Human smooth muscle cell (SMC) and fibroblast cell (FbC) sheets were harvested from temperature-responsive culture dishes and transplanted into ischemic hind limbs of athymic rats. ELISA showed significantly increased in vitro secretion of angiogenic factors by SMCs in comparison to FbCs. Twenty-one days after transplantation, laser doppler analysis demonstrated significantly increased blood perfusion in the SMC group. Perfusion with Indian ink and immunohistochemistry also revealed significantly greater numbers of functional capillaries in the SMC group. Finally, cell tracing experiments revealed that some SMCs from the transplanted cell sheets migrated into the ischemic tissues, contributing to newly formed vessels., Conclusions: SMC sheet transplantation allows for controlled and localized delivery of cells that possess angiogenic potential directly to ischemic tissues. Through the secretion of angiogenic factors, as well as cell migration and integration with newly formed vessels, SMC sheet transplantation provides an effective method for the revascularization of ischemic tissues.

Objective: Our treatment strategy for pulmonary atresia with ventricular septal defect (VSD) and major aortopulmonary collateral arteries is a staged repair that comprises the first complete unifocalization (UF) with 'unification' of intrapulmonary arteries and then the definitive repair. The purpose of this study is to evaluate the outcome of our staged repair strategy with complete UF and to determine the results of our current management strategy., Methods: From 1982 to 2004, 113 consecutive patients were treated with staged repair at our institute. We evaluated the risk of definitive repair failure or death in the 3 years after definitive repair using logistic regression. Furthermore, we compared the early group (patients who underwent UF before December 1995) and the late group (patients who underwent UF after January 1996)., Results: The mean follow-up interval was 8.8 years (0.8 months to 23.3 years), and Kaplan-Meier-estimated overall survival rates after first UF were 80.9, 73.8, and 69.9% at 5, 10, and 15 years, respectively. Survival in patients with an absent central pulmonary artery (PA) was significantly lower than in those with a central PA (p<0.05), and the factor that was significantly associated with definitive repair failure or death in the 3 years after definitive repair was central PA morphology (p<0.05). Higher mean PA pressure after UF was detected in patients with hypoplastic central PA, compared with those without hypoplastic PA (30.9 mmHg vs 23.3 mmHg, p<0.05). In the late group, age (in years) at first UF (3.9 vs 8.4, p<0.01), second UF (4.3 vs 9.2, p<0.01), and definitive repair (5.8 vs 9.1, p<0.01) was significantly younger than in early group, and the survival rate after first UF in the late group was 96.2 and 91.3% at 3 and 7 years, respectively. Systolic right ventricular pressure and the pressure ratio between the right and the left ventricles after definitive repair in the late group were significantly lower than in the early group (53.6 mmHg vs 75.0 mmHg, p<0.01; 61.7% vs 75.9%, p<0.05)., Conclusions: Hypoplastic central PA was a significant risk factor in this disease. The overall survival was improved by our current management strategy. Improved RV pressure after definitive repair appears to affect the long-term outcome.

Objective: This study was undertaken to compare long-term results of various types of surgical repairs for either congenitally corrected transposition of the great arteries or double outlet right ventricle with discordant atrioventricular connections, and to analyze the risk factors that affect early and late mortality and reintervention., Methods: Between January 1972 and September 2005, a total of 189 patients (median age 8.3 years, range 2 months to 47 years old) with congenitally corrected transposition of the great arteries or double outlet right ventricle with discordant atrioventricular connections underwent definitive repairs. The definitive repairs comprised a conventional repair (atrial septal defect, or ventricular septal defect closure with or without pulmonary stenosis release, or isolated tricuspid valve surgery) in 36 patients (group I), conventional Rastelli in 31 patients (group II), double-switch operation (atrial switch plus arterial switch) in 15 patients (group III), atrial switch plus intraventricular rerouting (with or without extracardiac conduits) in 69 patients (group IV), and a Fontan-type repair in 38 patients (group V). The mean follow-up period was 10.1 years. Hospitalization and late mortality and reoperation were indicated as events. Risk factors for these events were analyzed by logistic regression for hospital death and a Cox proportional hazards model for late events., Results: The Kaplan-Meier survival including hospital and late mortality was 62.4% at 32 years in group I, 78.5% at 27 years in group II, 74.5% at 15 years in group III, 80% at 16 years in group IV, and 79.3% at 22 years in group V. The reoperation-free ratio was 64.2% in group I, 76.6% in group II, 84.4% in group III, 89.6% in group IV, and 91.3% in group V. Risk analyses showed that the risk for hospital death was preoperative in patients with more than moderate tricuspid regurgitation and a cardiopulmonary bypass time of more than 240 minutes. A risk for late mortality was the presence of tricuspid regurgitation. Risks for reoperation were preoperative cardiomegaly, preoperative tricuspid regurgitation of more than grade II, ventricular septal defect enlargement, and body weight less than 10 kg. Risks for pacemaker implantation, as indicated by multivariate analysis, were ventricular septal defect enlargement during operation and age less than 3 years., Conclusions: There were no statistical differences between long-term survival rates of patients who underwent conventional surgical repair versus those of patients who underwent anatomic surgical repair. Results of conventional repair were satisfactory except in patients with significant tricuspid regurgitation. Results of anatomic repair were also satisfactory even for patients with significant tricuspid regurgitation, and therefore, anatomic repair should be the procedure of choice for those patients.

Objectives: The effect of hemodilution on neurologic outcome after cardiopulmonary bypass remains unclear. We studied the influences of hematocrit on cerebral oxygenation and neuropathologic outcome in a piglet model., Methods: Eleven piglets (9.3 +/- 1.1 kg) were randomized into 2 groups. Five piglets (group H) received a total blood prime resulting in a high hematocrit (33.0% +/- 2.3%), and 6 piglets (group L) received a crystalloid prime resulting in a low hematocrit (14.0% +/- 3.2%). Both groups underwent 90 minutes of moderate hypothermic cardiopulmonary bypass (28 degrees C) with alpha-stat strategy. Cerebral oxygenation was monitored by near-infrared spectroscopy. Group L received a blood transfusion immediately after cardiopulmonary bypass to reach the postoperative target hematocrit of 30%. The brain was fixed in situ 6 hours after weaning from cardiopulmonary bypass, and a histologic score for neurologic injury was assessed., Results: There were no significant differences in arterial blood gas analyses throughout the experiment between the groups. Mean arterial pressure, mixed venous oxygen saturation, and heart rate were significantly higher in group H compared with group L during hypothermia. Oxyhemoglobin and total hemoglobin signals detected by near-infrared spectroscopy were significantly lower in group L (analysis of variance, P < .0001), although the tissue oxygenation index was not different during cardiopulmonary bypass. Group L showed a poorer histologic score compared with group H (P = .0071)., Conclusions: Excessive hemodilution, such as a hematocrit of less than 15%, may be associated with a high incidence of neurologic injury. Further studies are required to determine the safety limits of hematocrit during pediatric cardiopulmonary bypass.

This study evaluated the endothelial function and mechanical properties of tissue-engineered vascular autografts (TEVAs) constructed with autologous mononuclear bone marrow cells (MN-BMCs) and a biodegradable scaffold using a canine inferior vena cava (IVC) model. MN-BMCs were obtained from a dog and seeded onto a biodegradable tubular scaffold consisting of polyglycolide fiber and poly(L-lactide-co-epsilon-caprolactone) sponge. This scaffold was implanted in the IVC of the same dog on the day of surgery. TEVAs were analyzed biochemically, biomechanically, and histologically after implantation. When TEVAs were explanted and stimulated with acetylcholine at 1 month, they produced nitrates and nitrites dose dependently. N(G)-nitro-L-arginine methylester significantly inhibited these reactions. With stimulation by acetylcholine, factor VIII-positive cells of TEVAs produced endothelial nitric oxide synthase proteins, and the ratio of endothelial nitric oxide synthase/s17 mRNA was similar among native IVC and TEVAs 1 and 3 months after implantation. TEVAs had biochemical properties and wall thickness similar to those of native IVC at 6 months after implantation, and tolerated venous pressure well without any problems such as calcification. The number of inflammatory cells in TEVAs and the ratio of CD4/s17 mRNA decreased significantly with time. These results indicate that TEVAs are a biocompatible material with functional endothelial cells and biomechanical properties and do not have unwanted side effects.

Objectives: A girl who was diagnosed with cyanotic congenital heart disease in a newborn, showed anoxic spell attacks which we thought were correlated with the congenital heart disease. Although she underwent the palliative operation at 8 months old and her SpO2 was increased, she experienced severe and life-threatening respiratory dysfunction many times after that. After careful examinations, the respiratory complaint was proved to be not only due to cyanotic congenital heart disease but also tracheobronchomalacia., Method: She had undergone the external stenting to the trachea and right bronchus at 1 year old. After that, she was examined by cardiac catheterization and the Fontan-type operation was successful using a tissue-engineered graft at 2 years old., Results: Her post-operative course was uneventful and she was discharged., Conclusion: It is very important to remember the possible existence of tracheobronchomalacia and prevent a life-threatening attack when congenital cardiac patients experience a prolonged respiratory failure or abnormal respiration.

Pulmonary artery is infrequently utilized as a material for coronary patch angioplasty in children. We applied a pulmonary arterial patch for coronary angioplasty on an 8-year-old boy with total occlusion of the left main coronary artery late after an arterial switch operation. The pulmonary arterial patch was easy to handle and the immediate result after the operation was satisfactory.

Objective: Prosthetic and bioprosthetic materials currently in use lack growth potential and therefore must be repeatedly replaced in pediatric patients as they grow. Tissue engineering is a new discipline that offers the potential for creating replacement structures from autologous cells and biodegradable polymer scaffolds. In May 2000, we initiated clinical application of tissue-engineered vascular grafts seeded with cultured cells. However, cell culturing is time-consuming, and xenoserum must be used. To overcome these disadvantages, we began to use bone marrow cells, readily available on the day of surgery, as a cell source. The aim of the study was to assess the safety and feasibility of this technique for creating vascular tissue under low-pressure systems such as pulmonary artery or venous pressure., Methods: Since September 2001, tissue-engineered grafts seeded with autologous bone marrow cells have been implanted in 42 patients. The patients or their parents were fully informed and had given consent to the procedure. A 5-mL/kg specimen of bone marrow was aspirated with the patient under general anesthesia before the skin incision. The polymer tube serving as a scaffold for the cells was composed of a copolymer of l -lactide and -caprolactone (50:50). This copolymer is degraded by hydrolysis. The matrix is more than 80% porous, and the diameter of each pore is 20 to 100 microm. Polyglycolic acid woven fabric with a thickness of 0.5 mm was used for reinforcement. Twenty-three tissue-engineered conduits (grafts for extracardiac total cavopulmonary connection) and 19 tissue-engineered patches were used for the repair of congenital heart defects. The patients' ages ranged from 1 to 24 years (median 5.5 years). All patients underwent a catheterization study, computed tomographic scan, or both, for evaluation after the operation. The patients received anticoagulation therapy for 3 to 6 months after surgery., Results: Mean follow-up after surgery was 490 +/- 276 days (1.3-31.6 months, median 16.7 months). There were no complications such as thrombosis, stenosis, or obstruction of the tissue-engineered autografts. One late death at 3 months after total cavopulmonary connection was noted in patient with hypoplastic left heart syndrome; this was unrelated to the tissue-engineered graft function. There was no evidence of aneurysm formation or calcification on cineangiography or computed tomography. All tube grafts were patent, and the diameter of the tube graft increased with time (110% +/- 7 % of the implanted size)., Conclusion: Biodegradable conduits or patches seeded with autologous bone marrow cells showed normal function (good patency to a maximum follow-up of 32 months). As living tissues, these vascular structures may have the potential for growth, repair, and remodeling. The tissue-engineering approach may provide an important alternative to the use of prosthetic materials in the field of pediatric cardiovascular surgery. Longer follow-up is necessary to confirm the durability of this approach.

Objective: To overcome the shortcomings of current vascular grafts, tissue-engineering methods have been applied to cardiovascular regions. We previously reported the creation of a tissue-engineered vascular graft by using vascular mixed cells. However, the cost and manpower for harvesting and culturing the cells was too burdensome. To overcome these drawbacks, we have developed a new method for creating a tissue-engineered vascular graft by using bone marrow cells, which can be obtained easily and used immediately, without cell culture., Methods: Biodegradable polymers seeded with different types of cells (group V, cultured venous cells; group B, bone marrow cells without culture; and group C, non-cell-seeded graft [as control]) were implanted into the inferior venae cavae of dogs. The grafts were explanted at 4 weeks and assessed histologically and biochemically., Results: In the histologic examination, a regular layer of Masson-staining collagen fiber and a layer of factor VII-stained endothelial and ant-alpha-smooth muscle cell antigen-immunoreactive cells stained in groups V and B like native vascular tissue, whereas no such stained regular lining was detected in group C. A 4-hydroxyproline assay in group C showed significantly lower levels than in groups V and B or native tissue ( P < .05). The DNA content of the tissue-engineered vascular graft tended to be higher in group C than in groups V and B or in native tissue., Conclusions: In the creation of tissue-engineered vascular grafts, the method of using bone marrow cells seems to be useful and superior to that of using vascular cells because bone marrow cells can be used directly, without culture.

Though congenital tracheal stenosis in infants with congenital heart disease is uncommon, congestive heart failure is often deteriorated by respiratory symptoms. We report an infant having a diagnosis of congenital tracheal stenosis complicated with congenital heart disease who underwent pericardial patch tracheoplasty after the arterial switch operation for the transposition of the great arteries. External appearance of the trachea showed no stenosis and tracheal rings were well formed. Intraoperative bronchofiberscopy transilluminated the upper border of stenosis. The trachea was opened longitudinally to the extent of 30 mm to the point from 10 mm point proximal to the bifurcation. The incision was enlarged with the autologous pericardial patch using running absorbable suture. Then pericardial patch was anchored at several points to the posterior surface of the ascending aorta, innominate artery, and to the strap muscles of the neck. He is doing well now without any respiratory symptom.

Unlabelled: In May 2000 we initiated clinical application of tissue-engineered (TE) vascular grafts seeded with cultured cells. However, cell culturing is time-consuming and xeno-serum must be used. To overcome these disadvantages, we started to use bone marrow cells (BMCs), readily available on the day of surgery, as a cell source. The aim of this study was to assess the safety and feasibility of this technique for creating pulmonary arteries., Methods: Since August 2000, TE grafts seeded with autologous BMCs have been implanted in 42 patients. Bone marrow (5 ml/kg) was aspirated under general anesthesia prior to the skin incision. The polymer tube serving as a scaffold for the cells was composed of a co-polymer of 1-lactide and epsilon-caprolactone (50:50). This co-polymer is degraded by hydrolysis. The matrix is >80% porous and the diameter of each pore is 100-200 microm. Polyglycolic acid woven fabric with a thickness of 0.5 mm was used for reinforcement. Twenty-three TE conduits (TCPC grafts) and 19 TE patches were used for the repair of congenital heart defects. The patients' ages ranged from 1 to 24 years (median, 5.5 years). All patients underwent a catheterization study and/or computed tomography (CT) scans for evaluation after surgery. The patients received anticoagulation therapy for 3 to 6 months after surgery., Results: Mean follow-up after surgery was 584 days (maximum 42 months). There were no lethal complications such as thrombosis or aneurysmal rupture. One late death at 3 months after TCPC was noted in a hypoplastic left heart syndrome patient, which was unrelated to the TE graft. There was no evidence of aneurysm formation on cineangiography or CT., Conclusions: Biodegradable conduits or pulmonary vessel patches seeded with autologous BMCs showed normal function (good patency up to maximum follow-up of 38 months). As living tissues, these vessels may have the potential for growth, repair, and remodeling. The TE approach may provide an important alternative to the use of prosthetic materials in the field of pediatric cardiovascular surgery. Longer follow-up is necessary to confirm the feasibility of this approach.

Background: In conventional conduit operations, longevity has been essentially limited by the inevitable need for conduit replacement. This study was undertaken to compare long-term results of the use of equine pericardial conduits, autologous pericardial conduits, and direct anastomosis repair., Methods: Between 1982 and 2001, 366 patients underwent primary establishment of right ventricle-pulmonary artery continuity at our institution. The mean age at the time of operation was 6.2 years (range, 4 days to 28 years) and mean weight was 17.2 kg (range, 1.6 to 61 kg). Three different repair techniques were used for connection: hand-made valved equine pericardial conduits (n = 179), autologous pericardial conduits (n = 71), and direct anastomosis without a conduit (n = 116). Mean follow-up period for early survivors was 8.6 years in the equine group, 6.1 years in the direct anastomosis group, and 5.1 years in the autologous pericardium group., Results: Direct anastomosis repair (p = 0.0002) was associated with significantly better freedom from late events (conduit replacement or late death) than equine pericardial conduits. The hazard ratio was less with the autologous pericardium conduit than with the equine pericardium, but the difference was not statistically significant (p = 0.2122). Younger age at operation, and postoperative pressure ratio from right to left ventricle were also predictors of conduit longevity., Conclusions: To decrease the probability of late events, direct anastomosis is an encouraging technique compared with traditional equine pericardium extracardiac conduit repair. An autologous pericardial conduit, because of its benefits, would be an alternative when direct anastomosis is not suitable.

We performed an extracardiac total cavopulmonary connection (TCPC) operation using tissue-engineered graft for a patient with elevated central venous pressure due to severe tricuspid valve insufficiency 9 years after closure of a large ventricular septal defect. Before the TCPC, this patient had a right atrial thrombus and pulmonary embolism for which thrombolytic therapy was ineffective. The patient has been receiving anticoagulation therapy with both warfarin sodium and aspirin for 10 months after TCPC operation to avoid thrombotic complications. TCPC may be an alternative in selected patients with failing biventricular repair.

Objective: The optimal pH strategy during hypothermic cardiopulmonary bypass remains controversial. Systemic pulmonary collateral circulation may develop in patients with cyanotic anomalies. The purpose of this study was to evaluate the effect of pH strategies on cerebral oxygenation and systemic pulmonary collateral circulation during hypothermic cardiopulmonary bypass in cyanotic patients with heart disease., Methods: Forty cyanotic patients (age > 1 year) with heart disease were prospectively randomized into 2 groups. Group 1 (n = 19, 14.3 +/- 1.5 kg) underwent hypothermic cardiopulmonary bypass with alpha-stat strategy and group 2 (n = 21, 12.5 +/- 0.9 kg) with pH-stat. Cardiopulmonary bypass was established with pump-assisted drainage. Cerebral oxygenation was assessed by near-infrared spectroscopy and the systemic pulmonary collateral circulation was calculated by pump flows [% systemic pulmonary collateral circulation = perfusion flow - drainage flow)/perfusion flow x 100]. Lactate was measured as an index of systemic anaerobic metabolism., Results: There were no significant differences in preoperative hematocrit, oxygen saturation, Qp/Qs, cardiopulmonary bypass duration, minimum temperatures, perfusion flow and pressure, urine output, and depth of anesthesia between the groups. Oxyhemoglobin signal and tissue oxygenation index of near-infrared spectroscopy monitoring were significantly lower in group 1 compared with group 2 (P =.008 and P <.0001, respectively), suggesting inadequate cerebral oxygenation with alpha-stat. Deoxygenated hemoglobin signal was significantly higher in group 1 relative to group 2 (P <.0001). The % systemic pulmonary collateral circulation was significantly lower in group 2 compared with group 1, suggesting a reduced pulmonary collateral circulation with pH-stat (P <.0001, average; group 1, 20.1% +/- 1.2%; group 2; 7.7% +/- 0.7%). Serum lactate was significantly lower in group 2 (P <.0001)., Conclusions: The pH-stat strategy results in an improved environment, including sufficient cerebral oxygenation, decreased systemic pulmonary collateral circulation, and lower lactate level during hypothermic cardiopulmonary bypass in cyanotic patients with heart disease. Future studies should investigate the long-term neurological outcome.

Objective: Extracardiac and lateral tunnel total cavopulmonary connection are currently 2 major options for patients with a single ventricle physiology. However, each procedure has some disadvantages over the other. We developed a new technique of extracardiac total cavopulmonary connection using a tissue-engineered graft to overcome some of the disadvantages previously associated with both the extracardiac and lateral tunnel procedures., Methods: Between February 2001 and October 2002, 8 patients underwent an extracardiac total cavopulmonary connection using a tissue-engineered graft in our institution. Collected bone marrow cells (1 x 10(8) mononucleocytes) from a patient (approximately 1-4 mL/kg body weight) were seeded onto a biodegradable scaffold composed of polycaprolactone-polylactic acid copolymer reinforced with woven polylactic acid. After a 2- to 4-hour cultivation, the seeded scaffold was implanted as an extracardiac conduit during the total cavopulmonary connection operation., Results: There were no hospital or late deaths. At a mean follow-up of 13.4 months (range 4-25 months), all patients are alive and asymptomatic with no need for repeat surgery. A postoperative catheter examination or computed tomography showed all tissue-engineered grafts to be patent and revealed no stenosis, obstruction, or aneurysmal change in the 8 patients., Conclusion: We believe that extracardiac total cavopulmonary connection using a tissue-engineered graft has the potential to overcome some of the disadvantages previously associated with extracardiac or lateral tunnel total cavopulmonary connection. However, an extended follow-up period is required to clarify the long-term clinical outcome for the tissue-engineered graft.

Background: Materials commonly used to repair complex cardiac defects lack growth potential and have other unwanted side effects. We designed and tested a bone marrow cell (BMC)-seeded biodegradable scaffold that avoids these problems., Methods and Results: To demonstrate the contribution of the BMCs to histogenesis, we labeled them with green fluorescence, seeded them onto scaffolds, and implanted them in the inferior vena cava of dogs. The implanted grafts were analyzed immunohistochemically at 3 hours and subsequently at 2, 4, and 8 weeks after implantation using antibodies against endothelial cell lineage markers, endothelium, and smooth muscle cells. There was no stenosis or obstruction caused by the tissue-engineered vascular autografts (TEVAs) implanted into the dogs. Immunohistochemically, the seeded BMCs expressing endothelial cell lineage markers, such as CD34, CD31, Flk-1, and Tie-2, adhered to the scaffold. This was followed by proliferation and differentiation, resulting in expression of endothelial cells markers, such as CD146, factor VIII, and CD31, and smooth muscle cell markers, such as alpha-smooth muscle cell actin, SMemb, SM1, and SM2. Vascular endothelial growth factor and angiopoietin-1 were also produced by cells in TEVAs., Conclusions: These results provide direct evidence that the use of BMCs enables the establishment of TEVAs. These TEVAs are useful for cardiovascular surgery in humans and especially in children, who require biocompatible materials with growth potential, which might reduce the instance of complications caused by incompatible materials and lead to a reduced likelihood of further surgery.

A 7-year-old girl with unilateral absence of the pulmonary artery underwent autologous tissue limited reconstructive surgery. The proximal portion of the artery was reconstructed by rotating a reverse U-shaped cut opposite the pulmonary arterial wall and covering the anterior surface with autologous pericardium. Follow-up catheterization at 5.8 years after surgery revealed no stenosis. This procedure could become one of the preferred methods for this unusual clinical condition.

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.