A Modified EXIT-to-ECMO with Optional Reservoir Circuit for Use during an EXIT Procedure Requiring Thoracic Surgery.

A 34 year old mother with a history of polyhydraminos and premature rupture of membranes presented for an ex utero intrapartum treatment (EXIT) procedure to deliver her 34 week gestation fetus. The fetus had been diagnosed with a large cervical mass which significantly extended into the right chest. The mass compressed and deviated the airway and major neck vessels posteriorly. Imaging also revealed possible tumor involvement with the superior vena cava and right atrium. The plan was for potential extracorporeal membrane oxygenation (ECMO) during the EXIT procedure (EXIT-to-ECMO) and the potential for traditional cardiopulmonary bypass (CPB) for mediastinal tumor resection. A Modified EXIT-To-ECMO with Optional Reservoir (METEOR) circuit was devised to satisfy both therapies. A fetal airway could not be established during the EXIT procedure and so the EXIT-to-ECMO strategy was utilized. The fetus was then delivered and transferred to an adjoining operating room (OR). Traditional cardiopulmonary bypass with a cardiotomy venous reservoir (CVR) was utilized during the establishment of an airway, tumor biopsy and partial resection. The patient was eventually transitioned to our institution's standard ECMO circuit and then transferred to the intensive care unit. The patient was weaned from ECMO on day of life (DOL) eight and had a successful tumor resection on DOL 11. The patient required hospitalization for numerous interventions including cardiac surgery at 4 months of age. She was discharged to home at 5 months of age.

Repair of Tetralogy of Fallot in Children Less Than 4 kg Body Weight.

We reviewed our experience of surgical repair of Tetralogy of Fallot (TOF) in children weighing less than or equal to 4 kg to compare outcome of early palliation versus complete repair as the initial surgical approach. Seventy-six patients, weighing ≤ 4 kg, with TOF surgery between January 2005 and September 2013 were included in this single-center retrospective study. Twenty-five patients who underwent initial shunt procedure followed by later full repair were compared to 51 patients who had primary full repair for differences in baseline characteristics and outcomes. Shunt group patients had lower body weight, 2.76 ± 0.69 versus 3.11 ± 0.65 (kg), p = 0.03, and lower preoperative oxygen saturations, 82 ± 7 versus 90 ± 6 (%), p = 0.0001, than full repair group. A higher number of surgical procedures per patient was recorded in shunt patients, 2.29 ± 0.59 versus 1.27 ± 0.49, p = 0.00002. Thirteen of 51 patients in the full repair group required a repeat surgery. Catheterization procedures were performed in 12 patients in shunt and in 15 patients in full repair group, with interventional angioplasty in three and 11, respectively, p ≥ 0.05. Two patients, both in the shunt group, died after the surgery. Early full repair had longer hospital stay but significantly less hospitalizations 1.95 ± 1.3 versus 2.5 ± 1.4, p = 0.03. Initial complete repair of TOF in small children yielded favorable outcome with significantly less surgical procedures and subsequent hospitalizations. Cath laboratory re-interventions for residual defects were similar after both surgical approaches, and type of initial surgery does not predict freedom from re-intervention.

Successful treatment of mediastinitis in a young child by omental translocation following extracardiac Fontan graft placement.

Mediastinitis after a midline sternotomy can become a serious complication, especially after implantation of prosthetic vascular grafts. We present a case of a three-year-old boy with hypoplastic left heart syndrome who developed mediastinitis following his third-stage palliation (Fontan operation). Rather than following the "traditional" surgical therapy of graft explantation, debridement, and replacement, we chose to preserve the graft and protect it by omental translocation. The relative merits of this therapeutic approach, which is rarely utilized and underappreciated in children, are outlined and discussed.

Estimated in vivo postnatal surface growth patterns of the ovine main pulmonary artery and ascending aorta.

Delineating the normal postnatal development of the pulmonary artery (PA) and ascending aorta (AA) can inform our understanding of congenital abnormalities, as well as pulmonary and systolic hypertension. We thus conducted the following study to delineate the PA and AA postnatal growth deformation characteristics in an ovine model. MR images were obtained from endoluminal surfaces of 11 animals whose ages ranged from 1.5 months/15.3 kg mass (very young) to 12 months/56.6 kg mass (adult). A bicubic Hermite finite element surface representation was developed for the each artery from each animal. Under the assumption that the relative locations of surface points were retained during growth, the individual animal surface fits were subsequently used to develop a method to estimate the time-evolving local effective surface growth (relative to the youngest measured animal) in the end-diastolic state. Results indicated that the spatial and temporal surface growth deformation patterns of both arteries, especially in the circumferential direction, were heterogeneous, leading to an increase in taper and increase in cross-sectional ellipticity of the PA. The longitudinal PA growth stretch of a large segment on the posterior wall reached 2.57 ± 0.078 (mean ± SD) at the adult stage. In contrast, the longitudinal growth of the AA was smaller and more uniform (1.80 ± 0.047). Interestingly, a region of the medial wall of both arteries where both arteries are in contact showed smaller circumferential growth stretches-specifically 1.12 ± 0.012 in the PA and 1.43 ± 0.071 in the AA at the adult stage. Overall, our results indicated that contact between the PA and AA resulted in increasing spatial heterogeneity in postnatal growth, with the PA demonstrating the greatest changes. Parametric studies using simplified geometric models of curved arteries during growth suggest that heterogeneous effective surface growth deformations must occur to account for the changes in measured arterial shapes during the postnatal growth period. This result suggests that these first results are a reasonable first-approximation to the actual effective growth patterns. Moreover, this study clearly underscores how functional growth of the PA and AA during postnatal maturation involves complex, local adaptations in tissue formation. Moreover, the present results will help to lay the basis for functional replacement by defining critical geometric metrics.

Pulmonary artery conduit in vivo dimensional requirements in a growing ovine model: comparisons with the ascending aorta.

BACKGROUND AND AIM OF THE STUDY: The pulmonary trunk (PT) structure and function are abnormal in multiple congenital cardiovascular diseases. Existing surgical treatments of congenital malformations of the right ventricular outflow tract and PT do not provide a long-term replacement that can adapt to normal growth. Although there is strong interest in developing tissue-engineered approaches for PT conduit replacement, there remains an absence of any complete investigation of the native geometric growth patterns of the PT to serve as a necessary benchmark. METHODS: Eleven Dorset sheep (aged 4-12 months) underwent a single cardiac magnetic resonance imaging study, from which luminal arterial surface points were obtained using a novel semi-automated segmentation technique. The three-dimensional shapes of the PT and ascending aorta (AA) were measured over the same time period to gain insight into differences in the geometric changes between these two great vessels. RESULTS: The volumetric growth of the PT appeared to be a linear function of age, whereas its surface geometry demonstrated non-uniform growth patterns. While tortuosity was maintained with age, the cross-sectional shape of the main pulmonary artery (MPA) evolved from circular in young animals to elliptical at 12 months. In addition, the distal MPA near the pulmonary artery bifurcation tapered with age. CONCLUSION: It can be concluded that postnatal growth of the PT is not a simple proportionate (i.e. isotropic) size increase, but rather exhibits complex three-dimensional geometric features during somatic growth.

Regional structural and biomechanical alterations of the ovine main pulmonary artery during postnatal growth.

The engineering foundation for novel approaches for the repair of congenital defects that involve the main pulmonary artery (PA) must rest on an understanding of changes in the structure-function relationship that occur during postnatal maturation. In the present study, we quantified the postnatal growth patterns in structural and biomechanical behavior in the ovine PA in the juvenile and adult stages. The biaxial mechanical properties and collagen and elastin fiber architecture were studied in four regions of the PA wall, with the collagen recruitment of the medial region analyzed using a custom biaxial mechanical-multiphoton microscopy system. Circumferential residual strain was also quantified at the sinotubular junction and bifurcation locations, which delimit the PA. The PA wall demonstrated significant mechanical anisotropy, except in the posterior region where it was nearly isotropic. Overall, we observed only moderate changes in regional mechanical properties with growth. We did observe that the medial and lateral locations experience a moderate increase in anisotropy. There was an average of about 24% circumferential residual stain present at the luminal surface in the juvenile stage that decreased to 16% in the adult stage with a significant decrease at the bifurcation, implying that the PA wall remodels toward the bifurcation with growth. There were no measurable changes in collagen and elastin content of the tunica media with growth. On average, the collagen fiber recruited more rapidly with strain in the adult compared to the juvenile. Interestingly, the PA thickness remained constant with growth. When this fact is combined with the observed stable overall mechanical behavior and increase in vessel diameter with growth, a simple Laplace Law wall stress estimate suggests an increase in effective PA wall stress with postnatal maturation. This observation is contrary to the accepted theory of maintenance of homeostatic stress levels in the regulation of vascular function and suggests alternative mechanisms regulate postnatal somatic growth. Understanding the underlying mechanisms, incorporating important structural features during growth, will help to improve our understanding of congenital defects of the PA and lay the basis for functional duplication in their repair and replacement.

Three-dimensional quantitative micromorphology of pre- and post-implanted engineered heart valve tissues.

There is a significant gap in our knowledge of engineered heart valve tissue (EHVT) development regarding detailed three-dimensional (3D) tissue formation and remodeling from the point of in vitro culturing to full in vivo function. As a step toward understanding the complexities of EHVT formation and remodeling, a novel serial confocal microscopy technique was employed to obtain 3D microstructural information of pre-implant (PRI) and post-implant for 12 weeks (POI) EHVT fabricated from PGA:PLLA scaffolds and seeded with ovine bone-marrow-derived mesenchymal stem cells. Custom scaffold fiber tracking software was developed to quantify scaffold fiber architectural features such as length, tortuosity, and minimum scaffold fiber-fiber separation distance and scaffold fiber orientation was quantified utilizing a 3D fabric tensor. In addition, collagen and cellular density of ovine pulmonary valve leaflet tissue were also analyzed for baseline comparisons. Results indicated that in the unseeded state, scaffold fibers formed a continuous, oriented network. In the PRI state, the scaffold showed some fragmentation with a scaffold volume fraction of 7.79%. In the POI specimen, the scaffold became highly fragmented, forming a randomly distributed short fibrous network (volume fraction of 2.03%) within a contiguous, dense collagenous matrix. Both PGA and PLLA scaffold fibers were observed in the PRI and POI specimens. Collagen density remained similar in both PRI and POI specimens (74.2 and 71.5%, respectively), though the distributions in the transmural direction appeared slightly more homogenous in the POI specimen. Finally, to guide future 2D histological studies for large-scale studies (since acquisition of high-resolution volumetric data is not practical for all specimens), we investigated changes in relevant collagen and scaffold metrics (collagen density and scaffold fiber orientation) with varying section spacing. It was found that a sectioning spacing up to 25 µm (for scaffold morphology) and 50 µm (for collagen density) in both PRI and POI tissues did not result in loss of information fidelity, and that sectioning in the circumferential or radial direction provides the greatest preservation of information. This is the first known work to investigate EHVT microstructure over a large volume with high resolution and to investigate time evolving in vivo EHVT morphology. The important scaffold fiber structural changes observed provide morphological information crucial for guiding future structurally based constitutive modeling efforts focused on better understanding EHVT tissue formation and remodeling.

In vivo monitoring of function of autologous engineered pulmonary valve.

OBJECTIVES: Clinical translation of tissue-engineered heart valves requires valve competency and lack of stenosis in the short and long term. Early studies of engineered valves showed promise, although lacked complete definition of valve function. Building on prior experiments, we sought to define the in vivo changes in structure and function of autologous engineered pulmonary valved conduits. METHODS: Mesenchymal stem cells were isolated from neonatal sheep bone marrow and seeded onto a bioresorbable scaffold. After 4 weeks of culture, valved conduits were implanted. Valve function, cusp, and conduit dimensions were evaluated at implantation (echocardiography), at the experimental midpoint (magnetic resonance imaging), and at explant, at 1 day, and 1, 6, 12, or 20 weeks postoperatively (direct measurement, echocardiography). Histologic evaluation was performed. RESULTS: Nineteen animals underwent autologous tissue-engineered valved conduit replacement. At implantation, valved conduit function was excellent; maximum transvalvular pressure gradient by Doppler echocardiography was 17 mm Hg; most valved conduits showed trivial pulmonary regurgitation. At 6 postoperative weeks, valve cusps appeared less mobile; pulmonary regurgitation was mild to moderate. At 12 weeks or more, valved conduit cusps were increasingly attenuated and regurgitant. Valved conduit diameter remained unchanged over 20 weeks. Dimensional measurements by magnetic resonance imaging correlated with direct measurement at explant. CONCLUSIONS: We demonstrate autologous engineered tissue valved conduits that function well at implantation, with subsequent monitoring of dimensions and function in real time by magnetic resonance imaging. In vivo valves undergo structural and functional remodeling without stenosis, but with worsening pulmonary regurgitation after 6 weeks. Insights into mechanisms of in vivo remodeling are valuable for future iterations of engineered heart valves.

Intravital molecular imaging of small-diameter tissue-engineered vascular grafts in mice: a feasibility study.

OBJECTIVES: Creating functional small-diameter tissue-engineered blood vessels has not been successful to date. Moreover, the processes underlying the in vivo remodeling of these grafts and the fate of cells seeded onto scaffolds remain unclear. Here we addressed these unmet scientific needs by using intravital molecular imaging to monitor the development of tissue-engineered vascular grafts (TEVG) implanted in mouse carotid artery. METHODS AND RESULTS: Green fluorescent protein-labeled human bone marrow-derived mesenchymal stem cells and cord blood-derived endothelial progenitor cells were seeded on polyglycolic acid-poly-L-lactic acid scaffolds to construct small-caliber TEVG that were subsequently implanted in the carotid artery position of nude mice (n = 9). Mice were injected with near-infrared agents and imaged using intravital fluorescence microscope at 0, 7, and 35 days to validate in vivo the TEVG remodeling capability (Prosense680; VisEn, Woburn, MA) and patency (Angiosense750; VisEn). Imaging coregistered strong proteolytic activity and blood flow through anastomoses at both 7 and 35 days postimplantation. In addition, image analyses showed green fluorescent protein signal produced from mesenchymal stem cell up to 35 days postimplantation. Comprehensive correlative histopathological analyses corroborated intravital imaging findings. CONCLUSIONS: Multispectral imaging offers simultaneous characterization of in vivo remodeling enzyme activity, functionality, and cell fate of viable small-caliber TEVG.

The role of organ level conditioning on the promotion of engineered heart valve tissue development in-vitro using mesenchymal stem cells.

We have previously shown that combined flexure and flow (CFF) augment engineered heart valve tissue formation using bone marrow-derived mesenchymal stem cells (MSC) seeded on polyglycolic acid (PGA)/poly-L-lactic acid (PLLA) blend nonwoven fibrous scaffolds (Engelmayr, et al., Biomaterials 2006; vol. 27 pp. 6083-95). In the present study, we sought to determine if these phenomena were reproducible at the organ level in a functional tri-leaflet valve. Tissue engineered valve constructs (TEVC) were fabricated using PGA/PLLA nonwoven fibrous scaffolds then seeded with MSCs. Tissue formation rates using both standard and augmented (using basic fibroblast growth factor [bFGF] and ascorbic acid-2-phosphate [AA2P]) media to enhance the overall production of collagen were evaluated, along with their relation to the local fluid flow fields. The resulting TEVCs were statically cultured for 3 weeks, followed by a 3 week dynamic culture period using our organ level bioreactor (Hildebrand et al., ABME, Vol. 32, pp. 1039-49, 2004) under approximated pulmonary artery conditions. Results indicated that supplemented media accelerated collagen formation (approximately 185% increase in collagen mass/MSC compared to standard media), as well as increasing collagen mass production from 3.90 to 4.43 pg/cell/week from 3 to 6 weeks. Using augmented media, dynamic conditioning increased collagen mass production rate from 7.23 to 13.65 pg/cell/week (88.8%) during the dynamic culture period, along with greater preservation of net DNA. Moreover, when compared to our previous CFF study, organ level conditioning increased the collagen production rate from 4.76 to 6.42 pg/cell/week (35%). Newly conducted CFD studies of the CFF specimen flow patterns suggested that oscillatory surface shear stresses were surprisingly similar to a tri-leaflet valve. Overall, we found that the use of simulated pulmonary artery conditions resulted in substantially larger collagen mass production levels and rates found in our earlier CFF study. Moreover, given the fact that the scaffolds underwent modest strains (approximately 7% max) during either CFF or physiological conditioning, the oscillatory surface shear stresses estimated in both studies may play a substantial role in eliciting MSC collagen production in the highly dynamic engineered heart valve fluid mechanical environment.

Predictors of outcome of arterial switch operation for complex D-transposition.

BACKGROUND: Overall mortality and reoperation risk for the arterial switch operation (ASO) for D-transposition of the great arteries (D-TGA) is low. D-TGA with ventricular septal defect (VSD) and aortic arch obstruction (AAO) is a higher risk subgroup in which we sought risk factors for mortality and reoperation after ASO. METHODS: Echocardiograms of 74 patients who underwent ASO, VSD, and arch repair for D-TGA, VSD and AAO were reviewed; the reoperation analysis considered the 65 survivors. Pre-ASO clinical and anatomic characteristics were compared between survivors and nonsurvivors; patients who required (R) and did not require (NR) reoperation. RESULTS: Distal transverse aortic arch (TrAo) z score equal to -2.5 or less, triscuspid valve z score less than 0, repaired muscular VSD, and circulatory arrest time were significant predictors of mortality. When stratified for circulatory arrest time below 60 minutes, small distal transverse aortic arch and tricuspid valve remained significant predictors of mortality. Mean aortic annulus size was smaller in R than NR (p = 0.048). Left coronary artery arising posteriorly was associated with a reoperation hazard ratio of 5.2 (p = 0.022). CONCLUSIONS: Preoperative anatomy was associated with death and reoperation post-ASO. Small TrAo and TV were risk factors for mortality in univariate analysis, and remained significant in the subset of patients with short circulatory arrest times, suggesting that even when controlling for technical factors, anatomic risk factors predict mortality. Small aortic annulus and posterior left circumflex artery origin were associated with reoperation. Patients with D-TGA, VSD, and AAO constitute a higher risk group, which includes patients who may be marginal candidates for two-ventricle repair.

Infant feeding practices of HIV-infected and uninfected women in Zimbabwe.

We surveyed infant feeding knowledge, attitudes, and practices in Zimbabwe to determine whether knowledge of HIV seropositivity influences infant feeding behavior. Questionnaires were administered to 97 women 1 and 4 weeks postpartum and prospective data on infant feeding practices were collected. Participants were pregnant women who consented to a HIV test. A total of 116 women participated of whom 99 women underwent voluntary HIV counseling and testing (VCT); 17 women agreed to blinded HIV testing but did not opt for VCT. The responses to questionnaires on infant feeding practices of HIV-positive and HIV-negative women who knew and did not know their HIV status at day 1 and week 4 postpartum were compared. We found that HIV-positive women who did not learn their status breastfed their infants less, introduced supplementary foods sooner, and planned to wean their babies earlier compared to other women (p = 0.005, p = NS, p= 0.02). HIV-positive women (30/97) more frequently reported a prior history of infant death and AIDS-related symptoms compared to HIV-negative women. We conclude that HIV-positive women who did not know their status made incorrect decisions with respect to infant feeding. These women may have suspected themselves to be HIV-positive and consequently underfed their infants or because these women were more symptomatic may have been less likely to breastfeed; decreased intake may increase the risk for malnutrition. Knowledge of HIV status may influence infant feeding decisions and reveal an urgent need to address infant feeding practices of pregnant women in Zimbabwe.

Sirolimus prolongs recovery from delayed graft function after cadaveric renal transplantation.

Sirolimus, lacking known nephrotoxicity, appeared to be an ideal immunosuppressive agent in the setting of delayed graft function (DGF) after renal transplantation. Coincident with our use of sirolimus however, we noticed prolongation of DGF. To investigate possible causes of prolonged DGF, extensive donor, recipient, transplant, and post-transplant data were collected on 132 consecutive cases of DGF at the University of California, San Francisco between 1/1/97 and 6/30/01. Cox proportional hazards analysis of time to graft function was used in univariate and multivariate models to identify factors that prolong DGF. Sirolimus had a large and highly significant effect on time to graft function (hazard ratio 0.48, p = 0.0007). The hazard ratio indicates that a recipient on sirolimus is half as likely to resolve DGF or twice as likely to remain on dialysis as a recipient without sirolimus. Two other factors had less potent but still significant association with DGF duration: recipient sensitization (hazard ratio 0.66, p = 0.037), and Novartis score (hazard ratio 0.93 per 1.0 increase; p = 0.034). Sirolimus retained its profound negative association with time to graft function in all multivariate models. Because sirolimus appears to prolong DGF, it may not be the optimal immunosuppressive choice in the DGF setting.