Partial heart xenotransplantation: A research protocol in non-human primates

Partial heart transplantation is a new type of transplant that delivers growing heart valve replacements for babies. Partial heart transplantation differs from orthotopic heart transplantation because only the part of the heart containing the heart valve is transplanted. It also differs from homograft valve replacement because viability of the graft is preserved by tissue matching, minimizing donor ischemia times, and recipient immunosuppression. This preserves partial heart transplant viability and allows the grafts to fulfill biological functions such as growth and self-repair. These advantages over conventional heart valve prostheses are balanced by similar disadvantages as other organ transplants, most importantly limitations in donor graft availability. Prodigious progress in xenotransplantation promises to solve this problem by providing an unlimited source of donor grafts. In order to study partial heart xenotransplantation, a suitable large animal model is important. Here we describe our research protocol for partial heart xenotransplantation in nonhuman primates.

Palliation of a Heterotaxy Single Ventricle Neonate with Pulmonary Atresia and Obstructed TAPVR

Patients born with obstructed total anomalous pulmonary venous return have a high risk of morbidity and mortality in the neonatal period, which only increases when combined with single ventricle physiology and non-cardiac congenital anomalies such as heterotaxy syndrome. Despite advances in management of congenital heart disease, surgery within the first weeks of life to repair the pulmonary venous connection and establish pulmonary blood flow with a systemic-to-pulmonary shunt has historically led to disappointing outcomes. A multidisciplinary approach with pediatric interventional cardiology and cardiac surgery is required to reduce morbidity and mortality in this extremely high-risk patient population. Extending the time between birth and cardiac surgery can lessen postoperative complications and mortality risk, especially in patients with abnormal thoracoabdominal relationships. Our team was able to successfully utilize transcatheter stent placement in a vertical vein and patent ductus arteriosus to delay and stage cardiac surgeries in an infant born with obstructed total anomalous pulmonary venous return, unbalanced atrioventricular septal defect with pulmonary atresia and heterotaxy, thus reducing the morbidity and mortality associated with this diagnosis.

Demographics of Current and Aspiring Integrated Six-year Cardiothoracic Surgery Trainees

BACKGROUND

The integrated 6-year thoracic surgery (I-6) residency model was developed in part to promote early interest in cardiothoracic surgery in diverse trainees. To determine gaps in and opportunities for recruitment of women and minority groups in the pipeline for I-6 residency, we quantified rates of progression at each training level and trends over time.

METHODS

We obtained 2015 to 2019 medical student, I-6 applicant, and I-6 resident gender and race/ethnicity demographic data from the American Association of Medical Colleges and Electronic Residency Application Service public databases and Accreditation Council for Graduate Medical Education Data Resource Books. We performed χ², Fisher exact, and Cochran-Armitage tests for trend to compare 2015 and 2019.

RESULTS

Our cross-sectional analysis found increased representation of women and all non-White races/ethnicities, except Native American, at each training level from 2015 to 2019 (P < .001 for all). The greatest trends in increases were seen in the proportions of women (28% vs 22%, P = .46) and Asian/Pacific Islander (25% vs 15%, P = .08) applicants. There was also an increase in the proportions of women (28% vs 24%, P = .024) and White (61% vs 58%, P = .007) I-6 residents, with a trend for Asian/Pacific Islanders (20% vs 17%, P = .08). The proportions of Hispanic (5%) and Black/African American (2%) I-6 residents in 2019 remained low.

CONCLUSIONS

I-6 residency matriculation is not representative of medical student demographics and spotlights a need to foster early interest in cardiothoracic surgery among all groups underrepresented in medicine while ensuring that we mitigate bias in residency recruitment.

Augmentation of Histone Deacetylase 6 Activity Impairs Mitochondrial Respiratory Complex I in Ischemic/Reperfused Diabetic Hearts

BACKGROUND

Diabetes augments activity of histone deacetylase 6 (HDAC6) and generation of tumor necrosis factor α (TNFα) and impairs the physiological function of mitochondrial complex I (mCI) which oxidizes reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide to sustain the tricarboxylic acid cycle and β-oxidation. Here we examined how HDAC6 regulates TNFα production, mCI activity, mitochondrial morphology and NADH levels, and cardiac function in ischemic/reperfused diabetic hearts.

METHODS

HDAC6 knockout, streptozotocin-induced type 1 diabetic, and obese type 2 diabetic db/db mice underwent myocardial ischemia/reperfusion injury in vivo or ex vivo in a Langendorff-perfused system. H9c2 cardiomyocytes with and without HDAC6 knockdown were subjected to hypoxia/reoxygenation injury in the presence of high glucose. We compared the activities of HDAC6 and mCI, TNFα and mitochondrial NADH levels, mitochondrial morphology, myocardial infarct size, and cardiac function between groups.

RESULTS

Myocardial ischemia/reperfusion injury and diabetes synergistically augmented myocardial HDCA6 activity, myocardial TNFα levels, and mitochondrial fission and inhibited mCI activity. Interestingly, neutralization of TNFα with an anti-TNFα monoclonal antibody augmented myocardial mCI activity. Importantly, genetic disruption or inhibition of HDAC6 with tubastatin A decreased TNFα levels, mitochondrial fission, and myocardial mitochondrial NADH levels in ischemic/reperfused diabetic mice, concomitant with augmented mCI activity, decreased infarct size, and ameliorated cardiac dysfunction. In H9c2 cardiomyocytes cultured in high glucose, hypoxia/reoxygenation augmented HDAC6 activity and TNFα levels and decreased mCI activity. These negative effects were blocked by HDAC6 knockdown.

CONCLUSIONS

Augmenting HDAC6 activity inhibits mCI activity by increasing TNFα levels in ischemic/reperfused diabetic hearts. The HDAC6 inhibitor, tubastatin A, has high therapeutic potential for acute myocardial infarction in diabetes.

Cardio-omentopexy requires a cardioprotective innate immune response to promote myocardial angiogenesis in mice

Objective

The pedicled greater omentum, when applied onto stressed hearts using omentopexy, has been shown to be protective in humans and animals. The mechanisms underlying cardioprotection using omentopexy remain elusive. This study examined whether macrophage-mediated angiogenesis accounts for the cardioprotective effect of omentopexy in mice.

Methods

C57BL/6 mice were subjected to minimally invasive transverse aortic constriction for 6 weeks and subsequent cardio-omentopexy for 8 weeks. Control mice underwent the same surgical procedures without aortic constriction or cardio-omentopexy.

Results

Transverse aortic constriction led to left ventricular concentric hypertrophy, reduced mitral E/A ratio, increased cardiomyocyte size, and myocardial fibrosis in the mice that underwent sham cardio-omentopexy surgery. The negative effects of transverse aortic constriction were prevented by cardio-omentopexy. Myocardial microvessel density was elevated in the mice that underwent aortic constriction and sham cardio-omentopexy surgery, and cardio-omentopexy further enhanced angiogenesis. Nanostring gene array analysis uncovered the activation of angiogenesis gene networks by cardio-omentopexy. Flow cytometric analysis revealed that cardio-omentopexy triggered the accumulation of cardiac MHCIIloLyve1+TimD4+ (Major histocompatibility complex class IIlow lymphatic vessel endothelial hyaluronan receptor 1+ T cell immunoglobulin and mucin domain conataining 4+) resident macrophages at the omental-cardiac interface. Intriguingly, the depletion of macrophages with clodronate-liposome resulted in the failure of cardio-omentopexy to protect the heart and promote angiogenesis.

Conclusions

Cardio-omentopexy protects the heart from pressure overload-elicited left ventricular hypertrophy and dysfunction by promoting myocardial angiogenesis. Cardiac MHCIIloLyve1+TimD4+ resident macrophages play a critical role in the cardioprotective effect and angiogenesis of cardio-omentopexy.

Video Abstract

Single-Stage Surgical Management of Atrioventricular Septal Defects with Coarctation of the Aorta

Surgical options for coarctation of aorta (CoA) with atrioventricular septal defect (AVSD) include single-stage repair vs. staged approach with neonatal CoA repair and delayed AVSD repair. The durability of left atrioventricular valve (LAVV) function after neonatal repair is questioned, and the optimal approach remains controversial. Eighteen CoA-AVSD patients who underwent single-stage repair 2005-2015 by a single surgeon were retrospectively analyzed. Fifteen patients had complete and three had partial AVSD. Birth weight was 3.19 kg (2.17-4.08). Age at surgery was 16 days (6-127). One- and ten-year survival were 80% and 69%. Freedom from reintervention was 60% and 40% at one and ten-year respectively. Reinterventions included relief of left ventricular outflow tract obstruction (LVOTO) (n = 4), repair of cleft LAVV (n = 3), and LAVV and aortic valve replacement (n = 1). Freedom from LAVV reintervention was 85.6% and 66% at 1 and 10 years respectively. There were four deaths: two post-operative and two following hospital discharge. Mortality was due to sepsis in three patients, and heart failure related to LVOTO and LAVV insufficiency in one. At 68-month (0.6-144) follow-up the majority had mild or less LAVV regurgitation, and all had normal LV dimension and systolic function. There was no recurrent arch obstruction. Single-stage surgical repair of CoA-AVSD is feasible and reasonable. Survival and freedom from reintervention in our cohort approximate those outcomes of two-stage repair with durable left AV valve function and no recurrent arch obstruction. These patients are frequently syndromic and demonstrate mortality risk from non-cardiac causes. Consideration of a single-staged approach is warranted for appropriate patients with CoA-AVSD.

Applicability and Durability of Valve-Sparing Tetralogy of Fallot Repair

BACKGROUND

Although valve-sparing repair remains ideal for patients with tetralogy of Fallot, the durability of valve-sparing repair and which patients may have been better served with a transannular patch remain unclear.

METHODS

Retrospective review was performed of tetralogy of Fallot operations at our institution from January 2008 to December 2018. Standard demographic data were collected, including echocardiographic parameters, operative details, and clinical outcomes. Statistical analysis was performed comparing the transannular patch and valve-sparing repair groups.

RESULTS

Sixty-seven patients underwent tetralogy of Fallot repair with a median age of 4.5 (3.2-6.0) months and weight of 5.8 (5.2, 6.7) kg. Seventeen (25%) patients underwent transannular patch repair and 50 (75%) patients underwent valve-sparing repair. There was no difference in age or weight between patients who underwent a transannular patch repair and those who underwent a valve-sparing repair. At last follow-up (median 42 months), there was a trend of a higher peak pulmonary valve/right ventricular outflow tract gradient (P = .06) in the valve-sparing group, but no difference in the pulmonary valve annulus z-scores. Additionally, the pulmonary valve z-scores in the valve-sparing group decreased from -2.3 ± 1.0 on predischarge echocardiogram of to -1.2 ± 1.6 on last follow-up, with the peak gradient on predischarge 23 (0-37) mm Hg remaining stable on last follow-up at 18 (0-29) mm Hg. There was one reoperation: pulmonary valve replacement six years after a transannular patch.

CONCLUSIONS

Obtaining a postrepair pulmonary valve z-score of -2 yields satisfactory, stable valve-sparing repair with pulmonary valve growth, acceptable gradients, minimal regurgitation, and high freedom from reintervention during follow-up.

Cardiopulmonary Bypass-Induced Inflammation and Myocardial Ischemia and Reperfusion Injury Stimulates Accumulation of Soluble MER

OBJECTIVES

Soluble MER has emerged as a potential biomarker for delayed resolution of inflammation after myocardial injury and a therapeutic target to reduce cardiac-related morbidity and mortality in adults. The significance of soluble MER in pediatric populations, however, is unclear. We sought to investigate if soluble MER concentrations change in response to myocardial ischemia and reperfusion injury in pediatric patients. In parallel, we also sought to investigate for correlations between the change in soluble MER concentration and specific patient, bypass, and postoperative data.

DESIGN

We quantified the change in plasma soluble MER concentration post- compared with precardiopulmonary bypass for each patient in a cohort of pediatric patients. Linear regression, correlation coefficients, and t tests were used to compare innate patient characteristics (i.e., sex, age, cyanotic vs acyanotic cardiac lesion), cardiac bypass data (i.e., total cardiac bypass time, total aortic cross-clamp time, perioperative steroid administration), and postcardiac bypass data (total postoperative ventilator days, total postoperative vasoactive medication days, and total postoperative ICU days) with change in soluble MER concentrations.

SETTING

Whole blood samples were obtained intraoperatively at a single tertiary care children's hospital from April to October 2019.

SUBJECTS

Our patient cohort included 24 pediatric patients ages ranging from birth to 19 years old with both cyanotic and acyanotic cardiac lesions.

INTERVENTIONS

Retrospective analyses of pediatric blood specimens, as well as patient, bypass, and postoperative data, were performed.

MEASUREMENTS AND MAIN RESULTS

We observed a statistically significant increase in soluble MER concentration post cardiac bypass in 17 of 24 patients (71%).

CONCLUSIONS

Soluble MER concentrations increase with cardiopulmonary bypass-induced inflammation and myocardial ischemia and reperfusion injury in pediatric patients. The utility of soluble MER as a clinical biomarker to identify pediatric patients at risk for exacerbated postoperative outcomes after bypass-induced myocardial ischemia and reperfusion injury requires further investigation.

Bone marrow-derived AXL tyrosine kinase promotes mitogenic crosstalk and cardiac allograft vasculopathy

Cardiac Allograft Vasculopathy (CAV) is a leading contributor to late transplant rejection. Although implicated, the mechanisms by which bone marrow-derived cells promote CAV remain unclear. Emerging evidence implicates the cell surface receptor tyrosine kinase AXL to be elevated in rejecting human allografts. AXL protein is found on multiple cell types, including bone marrow-derived myeloid cells. The causal role of AXL from this compartment and during transplant is largely unknown. This is important because AXL is a key regulator of myeloid inflammation. Utilizing experimental chimeras deficient in the bone marrow-derived Axl gene, we report that Axl antagonizes cardiac allograft survival and promotes CAV. Flow cytometric and histologic analyses of Axl-deficient transplant recipients revealed reductions in both allograft immune cell accumulation and vascular intimal thickness. Co-culture experiments designed to identify cell-intrinsic functions of Axl uncovered complementary cell-proliferative pathways by which Axl promotes CAV-associated inflammation. Specifically, Axl-deficient myeloid cells were less efficient at increasing the replication of both antigen-specific T cells and vascular smooth muscle cells (VSMCs), the latter a key hallmark of CAV. For the latter, we discovered that Axl-was required to amass the VSMC mitogen Platelet-Derived Growth Factor. Taken together, our studies reveal a new role for myeloid Axl in the progression of CAV and mitogenic crosstalk. Inhibition of AXL-protein, in combination with current standards of care, is a candidate strategy to prolong cardiac allograft survival.

Bioresorbable Stent to Manage Congenital Heart Defects in Children

Intravascular stents for pediatric patients that degrade without inhibiting vessel growth remain a clinical challenge. Here, poly(L-lactide) fibers (DH-BDS) at two thicknesses, 250 μm and 300 μm, were assembled into large, pediatric-sized stents (Ø10 - Ø20 mm). Fibers were characterized mechanically and thermally, then stent mechanical properties were compared to metal controls, while mass loss and degradation kinetics modeling estimated total stent degradation time. Thicker fibers displayed lower stiffness (1969 ± 44 vs 2126 ± 37 MPa) and yield stress (117 ± 12 vs 137 ± 5 MPa) than thinner counterparts, but exhibited similar fail strength (478 ± 28 vs 476 ± 16 MPa) at higher strains (47 ± 2 vs 44 ± 2%). Stents all exhibited crystallinity between 51.3 - 54.4% and fiber glass transition temperatures of 88.6 ± 0.5 °C and 84.6 ± 0.5 °C were well above physiological ranges. Radial strength (0.31 ± 0.01 - 0.34 ± 0.02 N/mm) in thinner stents was similar to metal stents (0.24 - 0.41 N/mm) up to Ø14 mm with no foreshortening and thicker coils granted comparable radial strength (0.32 ± 0.02 - 0.34 ± 0.02 N/mm) in stents larger than Ø14 mm. Both 10 mm (1.17 ± 0.02 % and 0.86 ± 0.1 %) and 12 mm (1.1 ± 0.03% and 0.89 ± 0.1%) stents exhibited minimal weight loss over one year. Degradation kinetics models predicted full stent degradation within 2.8 - 4.5 years depending on thickness. DH-BDS exhibiting hoop strength similar to metal stents and demonstrating minimal degradation and strength loss over the first year before completely disappearing within 3 to 4.5 years show promise as a pediatric interventional alternative to current strategies.

Mitral Valve Surgery in the First Year of Life

Data are limited on outcomes associated with mitral valve surgery in infants. Prior studies report high mortality and increased risk for late cardiac failure particularly for those with mitral stenosis. We sought to evaluate outcomes in patients with mitral stenosis (MS) or regurgitation (MR) who had mitral valvuloplasty or replacement in the first year of life. A retrospective analysis of all patients in a single institution who underwent mitral valvuloplasty or replacement in their first year of life from 2004 to 2016 (n = 25), excluding patients with single ventricle pathology or those undergoing surgery for atrioventricular canal defect, was carried out. Median age and weight at surgery were 76.5 days (range 2-329) and 4.5 kg (range 3.0-10.1), respectively. The primary mitral pathology was MR in 16 and MS in 9 patients. Median follow-up among living patients was 4 years (range 106 days-12.3 years). Overall survival was 96% at 30 days and 87.8% at 1, 5, and 10 years. There were three early deaths (12%), all within 6 weeks of surgery. There were no late deaths. Three patients required valve replacement, 1 of which had a primary mitral valve replacement and died within 30 days of surgery. Re-intervention-free survival (surgical and catheter based) was 83.8%, 73.3%, and 48.9% at 1, 5, and 10 years per Kaplan-Meier estimates. There was no difference in re-intervention-free survival between patients with MR versus MS. No risk factors for death or re-intervention were identified. Mitral valvuloplasty and replacement can be performed in infants under 1 year of age with acceptable survival and need for re-intervention.

Cardio-omentopexy Reduces Cardiac Fibrosis and Heart Failure After Experimental Pressure Overload

BACKGROUND

The pedicled greater omentum has been shown to offer benefit in ischemic heart disease for both animal models and human patients. The impact of cardio-omentopexy in a pressure overload model of left ventricular hypertrophy (LVH) is unknown.

METHODS

LVH was created in rats by banding the ascending aorta after right thoracotomy (n = 23). Sham surgery was performed in 12 additional rats. Six weeks after banding, surviving LVH rats were assigned to cardio-omentopexy by left thoracotomy (LVH+Om, n = 8) or sham left thoracotomy (LVH, n = 8). Sham rats also underwent left thoracotomy for cardio-omentopexy (Sham+Om, n = 6); the remaining rats underwent sham left thoracotomy (Sham, n = 6).

RESULTS

Echocardiography 10 weeks after cardio-omentopexy revealed LV end-systolic diameter, cardiomyocyte diamter, and myocardial fibrosis in the LVH group were significantly increased compared with the LVH+Om, Sham+Om, and Sham groups (p < 0.01). LV ejection fraction of the LVH group was lower than the LVH+Om group (p < 0.01). Gene expression analysis revealed significantly lower levels of sarcoendoplasmic reticulum calcium adenosine triphosphatase 2b in LVH rats than in the LVH+Om, Sham+Om, and Sham groups (p < 0.01). In contrast, collagen type 1 α 1 chain, lysyl oxidase-like protein 1, nuclear protein-1, and transforming growth factor- β1 in the LVH group were significantly higher than in the LVH+Om cohort (p < 0.01), consistent with a reduced fibrotic phenotype after omentopexy. Lectin staining showed myocardial capillary density of the LVH group was significantly lower than all other groups (p < 0.01).

CONCLUSIONS

Cardio-omentopexy reduced cardiac dilation, contractile dysfunction, cardiomyocyte hypertrophy, and myocardial fibrosis, while maintaining other molecular indicators of contractile function in this LVH model.

Supra-Annular Mitral Implantation of Melody Valve: Minimizing Left Ventricular Outflow Tract Obstruction

Utilization of the Melody valve for mitral valve replacement has been previously reported; however, left ventricular outflow tract obstruction is a frequent concern. In this report, a technique for supra-annular placement of the Melody valve in the mitral position is described which will minimize the risk of left ventricular outflow tract obstruction.

Descending Aortic Translocation and Right Pulmonary Artery Reimplantation for Midline Descending Aorta and Crossed Pulmonary Arteries in an Infant

Left mainstem bronchial compression by a midline descending thoracic aorta is a rare anatomic variant. Translocation of the descending thoracic aorta to the ascending aorta has recently been described to treat this condition. We performed an aortic translocation and right pulmonary artery reimplantation in a 4-month-old infant with severe pulmonary hypertension secondary to right pulmonary artery stenosis and left bronchial compression by a midline descending thoracic aorta. The procedure was successful in ameliorating the patient's left mainstem bronchial compression and pulmonary hypertension. Descending aortic translocation should be considered when the left bronchus is compressed causing respiratory symptoms.

Elevated cranial ultrasound resistive indices are associated with improved neurodevelopmental outcomes one year after pediatric cardiac surgery: A single center pilot study

OBJECTIVE

To determine if a non-invasive, repeatable test can be used to predict neurodevelopmental outcomes in patients with congenital heart disease.

METHODS

This was a prospective study of pediatric patients less than two months of age undergoing congenital heart surgery at the Children's Health Children's Medical Center at Dallas. Multichannel near-infrared spectroscopy (NIRS) was utilized during the surgery, and ultrasound (US) resistive indices (RI) of the major cranial vessels were obtained prior to surgery, immediately post-operatively, and prior to discharge. Pearson's correlation, Fischer exact t test, and Fischer r to z transformation were used where appropriate.

RESULTS

A total of 16 patients were enrolled. All had US data. Of the sixteen patients, two died prior to the neurodevelopmental testing, six did not return for the neurodevelopmental testing, and eight patients completed the neurodevelopmental testing. There were no significant correlations between the prior to surgery and prior to discharge US RI and neurodevelopmental outcomes. The immediate post-operative US RI demonstrated a strong positive correlation with standardized neurodevelopmental outcome measures. We were able to demonstrate qualitative differences using multichannel NIRS during surgery, but experienced significant technical difficulties implementing consistent monitoring.

CONCLUSIONS

A higher resistive index in the major cerebral blood vessels following cardiac surgery in the neonatal period is associated with improved neurological outcomes one year after surgery. Obtaining an ultrasound with resistive indices of the major cerebral vessels prior to and after surgery may yield information that is predictive of neurodevelopmental outcomes.

Use of a Modified Classic BT Shunt in a Patient With Multiple Conduit Obstructions With Positive Lupus Anticoagulant

The use of a right ventricle-to-pulmonary artery conduit has re-emerged as a popular alternative to a systemic artery-to-pulmonary artery shunt in the Norwood procedure. Both proximal obstruction secondary to dynamic compression and distal obstruction at the anastomosis site with the pulmonary arteries are well described. In an effort to prevent complications, a technique where in the conduit is placed through the entire full thickness, or dunked, through the RV free wall has been described. We report a case of a patient with HLHS and positive lupus anticoagulant who developed recurrent conduit obstructions. The "Sano" was abandoned in favor of an autologous source of pulmonary blood flow-the modified Blalock-Taussig shunt using the "turn down" of the carotid artery.

Initial Experience With the Pediatric Impella Device: A Feasibility Study in a Porcine Model

OBJECTIVE

This study's objective was to evaluate insertion techniques and device fit of the pediatric version of the Impella ventricular assist device in swine which had similar sized carotids and left ventricles (LVs) as children weighing 10-20 kg.

BACKGROUND

Options for minimally invasive circulatory support in children are limited. A modified device based on the current Impella 2.5 platform was created in an effort to provide minimally invasive circulatory support for children.

METHODS

Animal studies (n = 10) were performed to determine technical feasibility of device implant via the right common carotid artery (RCCA) in swine with a carotid and LV size similar to children with a BSA < 1 m² and weight 10-20 kg. The RCCA diameter was measured on pre-implant ultrasound and the LV length was measured at necropsy. The animals were supported for 4 hr and the device explanted. Blood samples and post-explant necropsy was performed to evaluate for device related complications.

RESULTS

All animals underwent successful device insertion. Mean carotid artery diameter by ultrasound was 3.5 ± 0.3 mm. There was no LV or aortic/mitral valve damage with a minimum LV length of 5.4 cm.

CONCLUSIONS

Minimally invasive circulatory support is needed in small children. Limitations are primarily related to vessel and chamber size. The Impella Pediatric catheter was safely and successfully implanted in carotid arteries similar in size to children weighing 10-20 kg with minimal complications. © 2016 Wiley Periodicals, Inc.

Bench and initial preclinical results of a novel 8 mm diameter double opposed helical biodegradable stent

BACKGROUND

Metallic endovascular stents are utilized off-label in congenital heart disease. Biodegradable stents (BDS) offer potential advantages in a growing child. We have previously reported double opposed helical (DH) BDS up to 6 mm diameter (DH-6). The objectives are to investigate the bench characteristics of larger 8 mm diameter BDS (DH-8) manufactured with increasing strut thicknesses and the inflammatory profile in a porcine model.

METHODS

DH-8 were manufactured with strut thicknesses 0.10, 0.12, and 0.18 mm and mechanical testing performed. Stents were deployed into the infrarenal descending aorta (DAO) of nine minipigs. At insertion (nonsurvival = 2), 1 week (n = 2), 1 month (n = 2), and 9 months (n = 3) follow-up angiography, intravascular ultrasound and histopathology were performed.

RESULTS

There was superior recoil and collapse pressure with increasing strut thickness, with 0.18 mm having 1.0% elastic recoil and collapse pressure 0.75 Atmospheres. There was good wall apposition at insertion with 5 BDS (4 DH-8 and 1 DH-6) but suboptimal in 4 as the minipigs infrarenal DAO were >8 mm (deployed at iliac bifurcation). Structural integrity was maintained in 8 BDS with 1 DH-8 collapsed at 9 months, secondary to strut damage at insertion. No thrombosis was seen. There was mild inflammation and neointimal proliferation at 1 week and 1 month, but a moderate inflammatory response at 9 months.

CONCLUSIONS

DH-8 with increased strut thickness had acceptable mechanical properties at the cost of an increased inflammatory response. Miniaturization to improve delivery and further investigation on the long-term inflammatory profile of thicker struts, including through degradation, is needed. © 2016 Wiley Periodicals, Inc.

Bacterial sensitivity assessment of multifunctional polymeric coatings for airway stents

Current interventional technology for pediatric airway obstruction consists of cardiovascular stents and silicon tubes. These devices are composed of permanent materials that have limitations in biocompatibility and mechanical properties that make them controversial for used in pediatrics. Bioresorbable stents offer a temporary intervention that dissolves in the body over time and can serve as a platform for local drug delivery. Here we investigate a novel approach to use an antibiotic, ciprofloxacin, as a polymerization initiator to synthesize poly(ciprofloxacin fumaric acid) (PCFA) and then a second polymer using gadodiamide as an initiator to synthesize poly(gadodiamide ciprofloxacin fumaric acid) (PGCFA). Polymer structure, degradation, thermal properties, and rheological behavior were analyzed. Ciprofloxacin released was determined and polymer degradation extracts were used in bacterial sensitivity assessments with four common airway pathogens. PCFA and PGCFA polymers and drug release properties were compared to our previously published polymer poly(fumaric acid) (PFA). These novel polymers enable new possibilities as coatings for bioresorbable biomedical applications that require antibiotic resistance and imaging capabilities. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2153-2161, 2017.

Selective Use of the Blalock-Taussig Shunt and Right Ventricle-to-Pulmonary Artery Conduit During the Norwood Procedure

Background:

The single ventricle reconstruction trial showed better one-year transplant-free survival for the right ventricle-to-pulmonary artery (RV-to-PA) conduit over the modified Blalock-Taussig shunt (mBTS) at Norwood operation. However, concerns remain about the long-term effects of a neonatal ventriculotomy. In our institution, we have used specific selection criteria for the use of mBTS in the Norwood operation.

Methods:

We reviewed 122 consecutive neonates undergoing the Norwood procedure from December 2006 to December 2013. We used the following criteria to select our source of pulmonary blood flow: (1) presence of a dominant morphologic left ventricle; (2) presence of antegrade blood in an ascending aorta that is greater than 3 mm; and (3) presence of significant large “crossing coronaries” on ventricle. All patients who met any of the above 3 criteria underwent an mBTS while the remaining patients underwent an RV-to-PA conduit.

Results:

Seventy-five (61.5%) patients had the RV-to-PA conduit and 47 (38.5%) patients had an mBTS. The overall surgical mortality was 9%. Mean follow-up interval was 23.5 months. Actuarial transplant-free survival was similar at 12, 24, 36, and 48 months in both the mBTS group and the RV-to-PA conduit group. In the RV-to-PA conduit group, actuarial transplant-free survival was 73% at 12 months, 71% at 24 months, 71% at 36 months, and 67% at 48 months, while in the mBTS group, actuarial transplant-free survival was 82% at 12 months, 75% at 24 months, 75% at 36 months, and 75% at 48 months.

Conclusion:

Our selection criteria for mBTS have allowed us to obtain equivalent transplant-free survival at 12, 24, 36, and 48 months when compared to the RV-to-PA conduit group.

Modified Senning Procedure for Correction of Atrioventricular Discordance With Total Anomalous Pulmonary Venous Return, Atrial Situs Inversus, Dextrocardia, and Bilateral Superior Venae Cavae

The Senning and Mustard baffles remain important techniques for the treatment of congenitally corrected transposition (cc-TGA), isolated ventricular inversion, and D-transposition of the great arteries with delayed presentation. We describe the treatment of an 8-month old infant with atrioventricular discordance, ventriculoarterial concordance, and dextrocardia with atrial situs inversus. A modified Senning procedure was performed through the "left-sided" atrium. Modifications of the Senning and Mustard baffles remain important tools in the treatment of rare conditions like isolated ventricular inversion.

A novel design biodegradable stent for use in congenital heart disease: mid-term results in rabbit descending aorta

OBJECTIVES

This study evaluates the feasibility of delivery and deployment of low and medium molecular weight (LMW and MMW, respectively) double-opposing helical (DH) poly-l-lactic acid biodegradable stent (BDS) in rabbit descending aorta (DAO). Secondary objectives were to assess patency and inflammation of stented vessels at 9 months and to investigate safety following intentional embolization of stent fragments in DAO.

BACKGROUND

A BDS that will relieve aortic obstruction and disappears as the child grows older allowing for preservation of aortic wall elasticity and natural growth of aorta will be ideal to treat Coarctation (CoA). BDS have never been evaluated in the DAO.

METHODS

Seven New Zealand white rabbits underwent implantation of DH-LMW (n = 7), DH-MMW (n = 3), and metal stents (n = 7) in DAO. BDS fragments were intentionally embolized into DAO in two rabbits.

RESULTS

All stents were deployed via a 6-French sheath. Five BDS covered the origin of major DAO side branches. Angiography and intravascular ultrasound showed good stent apposition to the wall of DAO with minimal luminal loss at 9 months follow-up. All stents had minimal neointimal hyperplasia on histopathology. Adverse events included 1 death, 1 aortic aneurysm, and lower extremity ulceration due to self-mutilation in an embolization rabbit.

CONCLUSIONS

Pilot study confirms the feasibility of delivery and deployment of up to 6-millimeter diameter DH BDS in rabbit DAO. Stent integrity with DH design was maintained at 9 months with minimal vessel inflammation. Potential morbidity due to embolized BD fragments cannot be ruled out and needs further evaluation.

Management and outcomes of heterotaxy syndrome associated with pulmonary atresia or pulmonary stenosis

BACKGROUND

Historic outcomes of patients with heterotaxy and pulmonary atresia or pulmonary stenosis (PA/PS) have been poor and in the current era are incompletely described. We reviewed our management of these patients and associated risk factors for death.

METHODS

We retrospectively reviewed the records of all patients with heterotaxy and PA/PS treated in our institution from January 1, 2002, to August 31, 2012. Death data were also confirmed with the Social Security Death Index. The log-rank test was done to assess six risk factors for death.

RESULTS

We identified 42 patients with heterotaxy and PA/PS. Median age at the first operation was 6.5 days, and median follow-up was 3.5 years. Death data were complete for all patients. Overall mortality was 19% (8 of 42). The 30-day, 1-year, and 5-year mortality estimation was 4.76%, 12.3%, and 19.1% respectively, as determined by the Kaplan-Meier method. The log-rank test showed total anomalous pulmonary venous return (TAPVR) (p<0.05) and obstructed TAPVR requiring an operation at less than 30 days (p=0.001) were significant risk factors for death.

CONCLUSIONS

In the current era, surgical treatment of heterotaxy and PA/PS can result in good outcomes. Associated TAPVR and obstructed TAPVR requiring neonatal correction were noted to be risk factors for death.

Optimization of preoperative status in hypoplastic left heart syndrome with intact atrial septum by left atrial decompression and bilateral pulmonary artery bands

Hypoplastic left heart syndrome (HLHS) with intact (IAS) or highly restrictive atrial septum (RAS) has extremely poor outcomes largely related to pulmonary pathology. At birth, immediate left atrial (LA) decompression is required to remain viable, but there is a tradeoff between residual increase in LA pressure and pulmonary overcirculation, either of which exacerbates the pulmonary status. From August 2010 to April 2013, a retrospective chart review was performed on consecutive patients with a prenatal diagnosis of HLHS with IAS/RAS presenting to a single center. The management strategy was immediate LA decompression followed by placement of bilateral pulmonary artery bands (bPAB) and subsequent conventional Norwood procedure. Six patients were born with HLHS with IAS/RAS during this time period with this planned management strategy. Four patients underwent LA decompression and subsequently developed low cardiac output with pulmonary overcirculation. bPAB were used with improvement in cardiac output and pronounced diuresis. These patients all survived the Norwood and subsequent Glenn procedures and remain alive [median follow-up 2.2 years (range 11 months-2.7 years)]. Two patients did not survive with therapy being withdrawn before the Norwood procedure. It is hypothesized that a strategy of total LA decompression followed by bPAB maximizes preoperative systemic perfusion and minimizes ongoing injury to the pulmonary system. This may enhance patient candidacy for the Norwood procedure and long-term survival.

Bilateral pulmonary artery banding for resuscitation in high-risk, single-ventricle neonates and infants: a single-center experience

OBJECTIVES

Bilateral pulmonary artery banding with or without ductal stenting has been performed as a resuscitative intervention for patients considered at too high risk for conventional single ventricle palliation. The purpose of the present study was to determine the outcomes using this strategy.

METHODS

We performed a retrospective review of 24 patients with single ventricle anatomy who were younger than 3 months who had undergone bilateral pulmonary artery banding and ductal stenting or maintenance of prostaglandin E(1) from January 2007 to October 2011 at our institution. The echocardiographic, angiographic, operative, and clinical data were reviewed. Follow-up data were available for 100% of the patients.

RESULTS

All 24 patients (13 male patients) underwent bilateral pulmonary artery banding at a median age of 8 days (range, 2-44 days). Their gestational age was 38 weeks (range, 27-41 weeks), and their weight was 3.01 kg (range, 1.5-4.4 kg). The cardiac diagnoses included hypoplastic left heart syndrome/variant hypoplastic left heart syndrome in 18, unbalanced atrioventricular canal in 4, and tricuspid atresia in 2. In the hypoplastic left heart syndrome group, 9 (50%) had an intact or a highly restrictive atrial septum requiring open (n = 1) or transcatheter (n = 8) atrial septostomy with or without atrial stent placement (n = 4). Ductal stenting was performed in 14 patients, and 10 patients were continued with prostaglandin E(1). Fifteen patients (62.5%) survived to undergo a Norwood procedure (n = 7), comprehensive stage 2 (n = 1), or primary cardiac transplantation (n = 7). Of the 9 who died, support was withdrawn in 5 because of a contraindication to transplantation, 1 because of sepsis and/or multiorgan system failure, and 1 for whom palliative care was desired. Two died awaiting transplantation. All 7 patients who underwent a conventional Norwood operation survived to discharge, and 6 of the 7 (85.7%) underwent bidirectional Glenn shunt placement. Of the 7 patients who underwent transplantation, 6 (85.7%) were alive at a median follow-up of 33.6 months.

CONCLUSIONS

Bilateral pulmonary artery banding with or without ductal stenting is an effective method of resuscitation for high-risk neonates and infants with a single ventricle, allowing for reasonable survival to conventional first-stage palliation or primary transplantation.

Use of del Nido cardioplegia solution and a low-prime recirculating cardioplegia circuit in pediatrics

The evolution of myocardial protection techniques has been both the source of milestone advancements and controversial debate in cardiac surgery. Our institution has modified a low-prime cardioplegia system (CPS) and adopted a single-dose cardioplegia solution (del Nido cardioplegia) for our congenital heart disease population. The goal of this article is to describe our CPS and outline our myocardial protection protocol. These techniques have allowed us to minimize circuit surface area, operate uninterrupted, and safely protect the myocardium during extended ischemic periods.

Ladd's procedure in functional single ventricle and heterotaxy syndrome: does timing affect outcome?

BACKGROUND

Infants with univentricular hearts often require intervention, such as a systemic to pulmonary shunt, as part of a staged surgical palliation. This physiology is inherently unstable, and interim mortality ranges from 4% to 15%. Heterotaxy syndrome confers a high incidence of intestinal rotation and fixation abnormalities. Controversy persists as to the need for elective Ladd's procedure. The purpose of this study is to review our experience in children with heterotaxy syndrome and functionally univentricular hearts who underwent Ladd's procedure.

METHODS

A retrospective chart review (2005 to 2010) from our institutional database identified patients with heterotaxy syndrome who underwent a Ladd's procedure.

RESULTS

Nine patients (3 boys and 6 girls) underwent Ladd's procedure. Patient demographics were as follows: median gestational age, 38 weeks (range, 37 to 39); median birth weight, 2.7 kg (range, 2 to 3.4 kg); and median age at Ladd's procedure, 180 days (range, 7 to 1,080). Four patients (44%) exhibited feeding intolerance with documented intestinal rotation and fixation abnormalities. Two of these patients underwent Ladd's procedure before cardiac surgery, 1 of whom had subsequent pulmonary artery banding, had recurrent necrotizing enterocolitis, and died. Two children had Ladd's procedure after initial cardiac palliation; both had shunt thrombosis during abdominal surgery, with a mortality of 50%. Five patients who were asymptomatic underwent Ladd's procedure after second-stage palliation. Mortality in this group was 0%.

CONCLUSIONS

Ladd's procedure in single ventricle heterotaxy patients who are tolerating enteral feeding should be performed after physiologic palliation to a more balanced circulation, ideally after cavopulmonary connection. Symptomatic neonates pose management challenges. Timing of abdominal surgery should be carefully considered, given the significant risk of mortality in these patients.

The impact of temperature and pump flow rate during selective cerebral perfusion on regional blood flow in piglets

OBJECTIVE

Ideal temperature and flow rate for selective cerebral perfusion (SCP) are not known. We examined regional organ perfusion in a piglet SCP model.

METHODS

Three groups underwent SCP at 30 mL/kg/min at different temperatures (15°C, 25°C, and 32°C) and 4 groups remained at 25°C for SCP at different flow rates (10, 30, 50 and 75 mL/kg/min). Fluorescent microspheres were injected at 5 minutes of normothermic cardiopulmonary bypass (CPB), immediately before SCP, SCP 45 minutes, SCP 90 minutes, and 2 hours after CPB. Brain and lower body organs were collected to examine regional blood flow (RBF, mL/min/g).

RESULTS

At 2 hours after CPB, RBF of the 32°C group was higher than that of the 15°C group (P < .05) at the caudate nucleus and hippocampus; RBF of the 32°C group was higher than that of the 25°C and 15°C groups (P < .05) at the neocortex. No significant difference in RBF was observed among any of the 25°C groups at different flow rates. Also, there was no significant difference between the RBF to the left and right sides of brain in either the temperature or flow rate groups. RBF did significantly increase with temperature in the liver and quadriceps during SCP (P < .05). At the kidney, RBF at SCP 90 minutes was significantly higher than that at SCP 45 minutes when all temperature groups were combined (P < .05).

CONCLUSIONS

SCP at 32°C provides higher brain RBF 2 hours after CPB. Increasing SCP flow rate does not increase RBF significantly at 25°C. Higher temperature during SCP results in improved RBF to the liver and quadriceps.

Ventricular assist device support in children and adolescents with heart failure: the Children's Medical Center of Dallas experience

Children with heart failure unresponsive to medical therapy are left with few options for survival. Ventricular assist devices (VADs) are life-saving options for such patients, allowing for bridge to transplantation or cardiac recovery. Retrospective review of cases from May 2006 to October 2010 was undertaken. Fourteen patients underwent implantation of VADs for refractory heart failure. Mean age was 9 years (range 1-17 years), and weight was 41 kg (range 9.7-71 kg). Indications for support: end-stage cardiomyopathy (n = 8), myocarditis (n = 3), univentricular failure (n = 2), and congenital heart disease/postcardiotomy (n = 1). Level of limitation at time of implant included critical cardiogenic shock in six (43%) and progressive decline in eight (57%). Extracorporeal membrane oxygenation was used as a bridge to VAD in five (36%) patients. Preimplant variables: 86% of patients requiring mechanical ventilation (mean 10.3 days), hyperbilirubinemia in 75%, and acute renal insufficiency in 79%. Device selection was systemic VAD in 11 (79%) and biventricular assist device in three (21%). Berlin Heart EXCOR was used in eight patients, while six patients received a Thoratec implantable VAD or paracorporeal VAD. Mean duration of support was 68 days (range 8-363 days). Overall survival was 79%. Ten patients (71%) were successfully bridged to transplantation, three (21%) died while on a device, one remains on support, and no patients were weaned from VAD. Children supported for single ventricle heart failure had a 50% survival with none currently bridged to transplantation. Complications included bleeding requiring reoperation in 21% (n = 3), stroke in 29% (n = 4), and driveline infections in 7% (n = 1). In two patients, a total of six pump exchanges were performed for thrombus formation. Survival for pediatric patients of all ages is excellent using current device technology with a majority of patients being successfully bridged to transplantation. Morbidity is acceptably low considering the severity of illness. Significant challenges exist with long-term extracorporeal support due to lack of donor availability and the high incidence of preformed alloantibodies especially in the failing single ventricle.

Randomized trial of hematocrit 25% versus 35% during hypothermic cardiopulmonary bypass in infant heart surgery

OBJECTIVES

We previously reported that postoperative hemodynamics and developmental outcomes were better among infants randomized to a higher hematocrit value during hypothermic cardiopulmonary bypass. However, worse outcomes were concentrated in patients with hematocrit values of 20% or below, and the benefits of hematocrit values higher than 25% were uncertain.

METHODS

We compared perioperative hemodynamics and, at 1 year, developmental outcome and brain magnetic resonance imaging in a single-center, randomized trial of hemodilution to a hematocrit value of 25% versus 35% during hypothermic radiopulmonary bypass for reparative heart surgery in infants undergoing 2-ventricle repairs without aortic arch obstruction.

RESULTS

Among 124 subjects, 56 were assigned to the lower-hematocrit strategy (24.8% +/- 3.1%, mean +/- SD) and 68 to the higher-hematocrit strategy (32.6% +/- 3.5%). Infants randomized to the 25% strategy, compared with the 35% strategy, had a more positive intraoperative fluid balance (P = .007) and lower regional cerebral oxygen saturation at 10 minutes after cooling (P = .04) and onset of low flow (P = .03). Infants with dextro-transposition of the great arteries in the 25% group had significantly longer hospital stay. Other postoperative outcomes, blood product usage, and adverse events were similar in the treatment groups. At age 1 year (n = 106), the treatment groups had similar scores on the Psychomotor and Mental Development Indexes of the Bayley Scales; both groups scored significantly worse than population norms.

CONCLUSIONS

Hemodilution to hematocrit levels of 35% compared with those of 25% had no major benefits or risks overall among infants undergoing 2-ventricle repair. Developmental outcomes at age 1 year in both randomized groups were below those in the normative population.

Cerebral near infrared spectroscopy is a reliable marker of systemic perfusion in awake single ventricle children

Clinical assessment of systemic perfusion in single ventricle patients with parallel circulation can be difficult in the outpatient setting. Near infrared spectroscopy (NIRS) is a noninvasive measure of cerebral oximetry. We measured vital signs, pulse oximetry, and NIRS in 20 single ventricle patients with parallel circulation prior to routine cardiac catheterization. These variables were evaluated to determine the best noninvasive predictor of the superior vena cava saturation (SVC(sat)) as a marker for the adequacy of systemic oxygen delivery. The mean age was 6.7 months [standard deviation (SD), 8.6] and mean weight was 6.5 kg (SD, 2.2). Diagnoses were hypoplastic left heart syndrome (8), tricuspid or pulmonary atresia (10), and double-outlet right ventricle variants (2), all prior to cavo pulmonary anastomoses or complete repairs. Stepwise multiple regression analysis generated a model in which only NIRS was a significant independent predictor of SVC(sat) (p = 0.009). These results support the conclusion that NIRS can be a useful tool to evaluate awake single ventricle patients in the outpatient setting.

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) in pediatric cardiac support

BACKGROUND

Resuscitation extracorporeal membrane oxygenation (R-ECMO) was introduced at our institution in July 2002. We reviewed the use of venoarterial (VA)-ECMO for cardiac diagnoses at our institution.

METHODS

Retrospective analysis of patients on VA-ECMO for cardiac failure was performed. Survival was defined as discharge from hospital.

RESULTS

Twenty-seven patients were supported with VA-ECMO (median age, 27 days; range, 1 to 640 days; median weight, 3.8 kg; range, 1.8 to 11.3 kg). Diagnoses were cardiomyopathy-myocarditis (CMM) in 8 (30%), systemic-to-pulmonary artery shunt-dependent single ventricle (SV) in 12 (44%), postcardiotomy for biventricular repair (BiV) in 6 (22%), and arrhythmia in 1 (4%). Sixteen of 27 patients survived (59%). Seven of 8 CMM patients survived (88%); 6 (75%) bridged to cardiac recovery, 1 to transplant (13%), and 1 death (13%). Seven of 12 SV patients survived (58%). The SV ECMO indications: post-Norwood ventricular dysfunction (n = 3, 2 deaths), postoperative cardiac failure (n = 6, 2 deaths), respiratory failure (n = 1, 1 death), and acute shunt occlusion (n = 2, 0 deaths). One of 6 BiV patients survived (17%). The BiV ECMO indications: failure to wean from CPB (n = 3, 3 deaths), postoperative cardiac failure (n = 2, 2 deaths), and pulmonary hypertension (n = 1, 0 deaths). Fifteen patients (56%) underwent cardiopulmonary resuscitation during ECMO cannulation. Eleven of 15 R-ECMO patients (73%) survived versus 5 of 12 non-R-ECMO patients (42%, p = 0.13). Median duration of R-ECMO: 66 hours (range, 18 to 179) versus 145 hours (range, 43 to 986, p = 0.01) for non-R-ECMO.

CONCLUSIONS

Resuscitation extracorporeal membrane oxygenation is an appropriate application in pediatric patients with cardiac disease. Single ventricle patients experiencing cardiopulmonary collapse and CMM patients have favorable outcomes. Failure to wean from CPB and postoperative ventricular failure are higher risk indications.

Total Cavopulmonary Connection Flow With Functional Left Pulmonary Artery Stenosis

BACKGROUND

In our multicenter study of the total cavopulmonary connection (TCPC), a cohort of patients with long-segment left pulmonary artery (LPA) stenosis was observed (35%). The clinically recognized detrimental effects of LPA stenosis motivated a computational fluid dynamic simulation study within 3-dimensional patient-specific and idealized TCPC pathways. The goal of this study was to quantify and evaluate the hemodynamic impact of LPA stenosis and to judge interventional strategies aimed at treating it.

METHODS AND RESULTS

Simulations were conducted at equal vascular lung resistance, modeling both discrete stenosis (DS) and diffuse long-segment hypoplasia with varying degrees of obstruction (0% to 80%). Models having fenestrations of 2 to 6 mm and atrium pressures of 4 to 14 mm Hg were explored. A patient-specific, extracardiac TCPC with 85% DS was studied in its original configuration and after virtual surgery that dilated the LPA to 0% stenosis in the computer medium. Performance indices improved exponentially (R2>0.99) with decreasing obstruction. Diffuse long-segment hypoplasia was approximately 50% more severe with regard to lung perfusion and cardiac energy loss than DS. Virtual angioplasty performed on the 3-dimensional Fontan anatomy exhibiting an 85% DS stenosis produced a 61% increase in left lung perfusion and a 50% decrease in cardiac energy dissipation. After 4-mm fenestration, TCPC baffle pressure dropped by approximately 10% and left lung perfusion decreased by approximately 8% compared with the 80% DS case.

CONCLUSIONS

DS <60% and diffuse long-segment hypoplasia <40% could be considered tolerable because both resulted in only a 12% decrease in left lung perfusion. In contrast to angioplasty, a fenestration (right-to-left shunt) reduced TCPC pressure at the cost of decreased left and right lung perfusion. These results suggest that pre-Fontan computational fluid dynamic simulation may be valuable for determining both the hemodynamic significance of LPA stenosis and the potential benefits of intervention.

Upregulation of hypoxia inducible factor is associated with attenuation of neuronal injury in neonatal piglets undergoing deep hypothermic circulatory arrest

BACKGROUND

Prolonged deep hypothermic circulatory arrest is known to cause neurological injury. Hypoxia inducible factor, a transcription factor that mediates adaptive changes during hypoxia, is neuroprotective in models of ischemic brain injury, in part by upregulating erythropoietin. This study tested the hypothesis that upregulation of hypoxia inducible factor and erythropoietin by preconditioning with hypoxia or the hypoxia-mimetic agents deferoxamine and cobalt chloride would be neuroprotective in a piglet model of deep hypothermic circulatory arrest.

METHODS

Anesthetized neonatal piglets were randomized to 4 preconditioning groups (15 per group): hypoxia, deferoxamine, cobalt chloride, or control (NaCl vehicle). Brain hypoxia inducible factor and erythropoietin contents were assessed by means of Western blotting at 3, 8, and 24 hours after treatment (n = 3 per time point). Twenty-four hours after treatment, 6 to 7 animals per group underwent cardiopulmonary bypass and 110 minutes of deep hypothermic circulatory arrest. After recovery, serial neurobehavioral examinations were conducted for 6 days, after which histopathologic brain injury and neuronal apoptosis (cleaved caspase 3) were assessed.

RESULTS

Erythropoietin expression was not significantly increased by any of the pretreatment strategies. In contrast, there was a significant upregulation of hypoxia inducible factor by pretreatment with deferoxamine and cobalt chloride (P = .002). Neurobehavioral measures revealed no significant differences in time to recovery or extent of injury. Examination of histopathologic brain injury in the hippocampus revealed that pretreatment with deferoxamine (0.4 +/- 0.3) and cobalt chloride (0.5 +/- 0.3) were associated with significantly less neuronal loss than pretreatment with hypoxia or control (2.8 +/- 0.5, P = .004). Finally, cleaved caspase 3 (a marker of apoptotic cell death) was also shown to be diminished in the cobalt and deferoxamine groups, but the difference was not significantly different from the value in the control group.

CONCLUSIONS

In contrast to hypoxia, deferoxamine and cobalt chloride preconditioning upregulated hypoxia inducible factor and were associated with histopathologic neuroprotection after exposure to cardiopulmonary bypass and prolonged deep hypothermic circulatory arrest.