Current practices for refractory chylothorax following congenital heart surgery.

INTRODUCTION: Chylothorax following paediatric cardiac surgery is associated with significant morbidity, particularly those that are refractory to conservative therapy. It is our impression that there is important variability in the medical, surgical, and interventional therapies used to manage refractory chylothorax between congenital heart programmes. We therefore conducted a survey study of current practices for managing refractory chylothorax. METHODS: The Chylothorax Work Group, formed with the support of the Pediatric Cardiac Critical Care Consortium, designed this multi-centre survey study with a focus on the timing and indication for utilising known therapies for refractory chylothorax. The survey was sent to one chylothorax expert from each Work Group centre, and results were summarised and reported as the frequency of given responses. RESULTS: Of the 20 centres invited to participate, 17 (85%) submitted complete responses. Octreotide (13/17, 76%) and sildenafil (8/17, 47%) were the most utilised medications. Presently, 9 (53%) centres perform pleurodesis, 15 (88%) perform surgical thoracic duct ligation, 8 (47%) perform percutaneous lymphatic interventions, 6 (35%) utilise thoracic duct decompression procedures, and 3 (18%) perform pleuroperitoneal shunts. Diagnostic lymphatic imaging is performed prior to surgical thoracic duct ligation in only 7 of the 15 (47%) centres that perform the procedure. Respondents identified barriers to referring and transporting patients to centres with expertise in lymphatic interventions. CONCLUSIONS: There is variability in the treatment of refractory post-operative chylothorax across a large group of academic heart centres. Few surveyed heart centres have replaced surgical thoracic duct ligation or pleurodesis with image-guided selective lymphatic interventions.

Hereditary haemorrhagic telangiectasia and SMAD4 mutation in a patient with complex single ventricle heart disease.

We report a case of hypoplastic left heart syndrome and with subsequent aortopathy and then found to have hereditary haemorrhagic telangiectasia/juvenile polyposis syndrome due to a germline SMAD4 pathologic variant. The patient's staged palliation was complicated by the development of neoaortic aneurysms, arteriovenous malformations, and gastrointestinal bleeding thought to be secondary to Fontan circulation, but workup revealed a SMAD4 variant consistent with hereditary haemorrhagic telangiectasia/juvenile polyposis syndrome. This case underscores the importance of genetic modifiers in CHD, especially those with Fontan physiology.

Advances in Extracorporeal Support Technologies in Critically Ill Children.

The field of pediatric heart failure is evolving, and the patient population is growing as survival after complex congenital heart surgeries is improving. Mechanical circulatory support and extracorporeal respiratory support in critically ill children has progressed to a mainstay rescue modality in pediatric intensive care medicine. The need for mechanical circulatory support is growing, since the number of organ donors does not meet the necessity. This article aims to review the current state of available mechanical circulatory and respiratory support systems in acute care pediatrics, with an emphasis on the literature discussing the challenges associated with these complex support modalities.

Contemporary Use of Ultrasonography in Acute Care Pediatrics.

Use of ultrasonography by clinicians at the point of care has expanded widely and rapidly. Pediatric acute care providers now leverage this valuable tool to guide procedures, diagnose pathophysiologic processes, and inform time-sensitive decisions in sick and unstable children. However, the deployment of any new technology must be packaged with training, protocols, and safeguards to optimize safety for patients, providers, and institutions. As ultrasonography is increasingly incorporated into residency, fellowship, and even medical student curricula, it is important that educators and trainees are aware of the diversity of its clinical applications. This article aims to review the current state of point-of-care ultrasonography in acute care pediatrics, with an emphasis on the literature supporting the use of this important clinical tool.

Novel Utilization of Ultrasound Enhancing Agents in Complex Congenital Heart Disease Following Superior Cavopulmonary Connection.

BACKGROUND: Children with single-ventricle congenital heart disease typically undergo a superior cavopulmonary connection (SCPC) as the second stage in their surgical palliation. Postoperatively, stenoses of the SCPC and branch pulmonary arteries can occur. If there are clinical concerns and echocardiography is insufficient for diagnosis, patients undergo invasive evaluation with exposure to radiation and anesthesia. The use of ultrasound enhancing agents (UEAs) to improve echocardiographic diagnostic capabilities has not previously been described in this population. METHODS: A single-center, retrospective case review was conducted of children who underwent echocardiography with UEA, following SCPC, from March 1, 2020, to April 15, 2022, at the Children's Hospital of Philadelphia. Twenty-two patients with hypoxemia or concern for obstruction following SCPC underwent UEA echocardiography. Extracted clinical data included patient demographics, echocardiographic images, angiography, surgical and transcatheter interventions, as well as available follow-up data. RESULTS: Six of the 22 UEA echocardiograms demonstrated stenosis or occlusion of either the SCPC or a pulmonary artery. All six patients underwent cardiac catheterization and five required intervention. Angioplasty was performed in each case with one requiring subsequent surgical revision. Sixteen of 22 UEA echocardiograms demonstrated no evidence of stenosis. Ten of these 16 patients improved, while six experienced persistent hypoxemia prompting referral for cardiac catheterization. Angiography confirmed the UEA echocardiographic findings (absence of stenosis) in four of these six patients. There were no adverse reactions related to UEA administration. CONCLUSIONS: Echocardiography with UEAs is a valuable and safe adjunctive imaging modality following SCPC, particularly when two-dimensional and color imaging is limited. This novel application of UEAs in complex patients with congenital heart disease provides an "angiogram-like" image, better delineating vessel walls and improving assessment of postoperative obstruction. As experience with UEAs increases in the congenital heart disease population, there may be opportunities to decrease invasive and costly procedures, while expediting the care of patients in need of intervention.

Development of consensus recommendations for the management of post-operative chylothorax in paediatric CHD.

OBJECTIVE: A standardised multi-site approach to manage paediatric post-operative chylothorax does not exist and leads to unnecessary practice variation. The Chylothorax Work Group utilised the Pediatric Critical Care Consortium infrastructure to address this gap. METHODS: Over 60 multi-disciplinary providers representing 22 centres convened virtually as a quality initiative to develop an algorithm to manage paediatric post-operative chylothorax. Agreement was objectively quantified for each recommendation in the algorithm by utilising an anonymous survey. "Consensus" was defined as ≥ 80% of responses as "agree" or "strongly agree" to a recommendation. In order to determine if the algorithm recommendations would be correctly interpreted in the clinical environment, we developed ex vivo simulations and surveyed patients who developed the algorithm and patients who did not. RESULTS: The algorithm is intended for all children (<18 years of age) within 30 days of cardiac surgery. It contains rationale for 11 central chylothorax management recommendations; diagnostic criteria and evaluation, trial of fat-modified diet, stratification by volume of daily output, timing of first-line medical therapy for "low" and "high" volume patients, and timing and duration of fat-modified diet. All recommendations achieved "consensus" (agreement >80%) by the workgroup (range 81-100%). Ex vivo simulations demonstrated good understanding by developers (range 94-100%) and non-developers (73%-100%). CONCLUSIONS: The quality improvement effort represents the first multi-site algorithm for the management of paediatric post-operative chylothorax. The algorithm includes transparent and objective measures of agreement and understanding. Agreement to the algorithm recommendations was >80%, and overall understanding was 94%.

Real-Time Ultrasound Guidance for Umbilical Venous Cannulation in Neonates With Congenital Heart Disease.

OBJECTIVES: Umbilical venous cannulation is the favored approach to perinatal central access worldwide but has a failure rate of 25-50% and the insertion technique has not evolved in decades. Improving the success of this procedure would have broad implications, particularly where peripherally inserted central catheters are not easily obtained and in neonates with congenital heart disease, in whom umbilical access facilitates administration of inotropes and blood products while sparing vessels essential for later cardiac interventions. We sought to use real-time, point-of-care ultrasound to achieve central umbilical venous access in patients for whom conventional, blind placement techniques had failed. DESIGN: Multicenter case series, March 2019-May 2021. SETTING: Cardiac and neonatal ICUs at three tertiary care children's hospitals. PATIENTS: We identified 32 neonates with congenital heart disease, who had failed umbilical venous cannulation using traditional, blind techniques. INTERVENTIONS: Real-time ultrasound guidance and liver pressure were used to replace malpositioned catheters and achieve successful placement at the inferior cavoatrial junction. MEASUREMENTS AND MAIN RESULTS: In 32 patients with failed prior umbilical venous catheter placement, real-time ultrasound guidance was used to successfully "rescue" the line and achieve central position in 23 (72%). Twenty of 25 attempts (80%) performed in the first 48 hours of life were successful, and three of seven attempts (43%) performed later. Twenty-four patients (75%) were on prostaglandin infusion at the time of the procedure. We did not identify an association between patient weight or gestational age and successful placement. CONCLUSIONS: Ultrasound guidance has become standard of care for percutaneous central venous access but is a new and emerging technique for umbilical vessel catheterization. In this early experience, we report that point-of-care ultrasound, together with liver pressure, can be used to markedly improve success of placement. This represents a significant advance in this core neonatal procedure.

Acute neurological injury in pediatric patients with single-ventricle congenital heart disease.

OBJECTIVE: Single-ventricle congenital heart disease (CHD) in pediatric patients with Glenn and Fontan physiology represents a unique physiology requiring the surgical diversion of the systemic venous return from the superior vena cava (Glenn) and then the inferior vena cava (Fontan) directly to the pulmonary arteries. Because many of these patients are on chronic anticoagulation therapy and may have right-to-left shunts, arrhythmias, or lymphatic disorders that predispose them to bleeding and/or clotting, they are at risk of experiencing neurological injury requiring intubation and positive pressure ventilation, which can significantly hamper pulmonary blood flow and cardiac output. The aim of this study was to describe the complex neurological and cardiopulmonary interactions of these pediatric patients after acute central nervous system (CNS) injury. METHODS: The authors retrospectively analyzed the records of pediatric patients who had been admitted to a quaternary children's hospital with CHD palliated to bidirectional Glenn (BDG) or Fontan circulation and acute CNS injury and who had undergone intubation and mechanical ventilation. Patients who had been admitted from 2005 to 2019 were included in the study. Clinical characteristics, surgical outcomes, cardiovascular and pulmonary data, and intracranial pressure data were collected and analyzed. RESULTS: Nine pediatric single-ventricle patients met the study inclusion criteria. All had undergone the BDG procedure, and the majority (78%) were status post Fontan palliation. The mean age was 7.4 years (range 1.3-17.3 years). At the time of acute CNS injury, which included traumatic brain injury, intracranial hemorrhage, and cerebral infarct, the median time interval from the most recent cardiac surgical procedure was 3 years (range 2 weeks-11 years). Maintaining normocarbia to mild hypercarbia for most patients during intubation periods did not cause neurological deterioration, and hemodynamic profiles were more favorable as compared to periods of hypocarbia. Hypocarbia was associated with unfavorable hemodynamics but was necessary to decrease intracranial hypertension. Most patients were managed using low mean airway pressure (MAWP) in order to minimize the impact on preload and cardiac output. CONCLUSIONS: The authors highlight the complex neurological and cardiopulmonary interactions with respect to partial pressure of arterial CO2 (PaCO2) and MAWP when pediatric CHD patients with single-ventricle physiology require mechanical ventilation. The study data demonstrated that tight control of PaCO2 and minimizing MAWP with the goal of early extubation may be beneficial in this population. A multidisciplinary team of pediatric critical care intensivists, cardiac intensivists and anesthesiologists, and pediatric neurosurgeons and neurologists are recommended to ensure the best possible outcomes.

Non-immunogenic utrophin gene therapy for the treatment of muscular dystrophy animal models.

The essential product of the Duchenne muscular dystrophy (DMD) gene is dystrophin1, a rod-like protein2 that protects striated myocytes from contraction-induced injury3,4. Dystrophin-related protein (or utrophin) retains most of the structural and protein binding elements of dystrophin5. Importantly, normal thymic expression in DMD patients6 should protect utrophin by central immunologic tolerance. We designed a codon-optimized, synthetic transgene encoding a miniaturized utrophin (µUtro), deliverable by adeno-associated virus (AAV) vectors. Here, we show that µUtro is a highly functional, non-immunogenic substitute for dystrophin, preventing the most deleterious histological and physiological aspects of muscular dystrophy in small and large animal models. Following systemic administration of an AAV-µUtro to neonatal dystrophin-deficient mdx mice, histological and biochemical markers of myonecrosis and regeneration are completely suppressed throughout growth to adult weight. In the dystrophin-deficient golden retriever model, µUtro non-toxically prevented myonecrosis, even in the most powerful muscles. In a stringent test of immunogenicity, focal expression of µUtro in the deletional-null German shorthaired pointer model produced no evidence of cell-mediated immunity, in contrast to the robust T cell response against similarly constructed µDystrophin (µDystro). These findings support a model in which utrophin-derived therapies might be used to treat clinical dystrophin deficiency, with a favorable immunologic profile and preserved function in the face of extreme miniaturization.

Efficient myocyte gene delivery with complete cardiac surgical isolation in situ.

BACKGROUND: Previously, we used cardiopulmonary bypass with incomplete cardiac isolation and antegrade administration of vector for global cardiac gene delivery. Here we present a translatable cardiac surgical procedure that allows for complete surgical isolation of the heart in situ with retrograde (through the coronary venous circulation) administration of both vector and endothelial permeabilizing agents to increase myocyte transduction efficiency. METHODS: In 6 adult dogs the heart was completely isolated with tourniquets placed around both vena cavae and cannulas and all pulmonary veins. On cardiopulmonary bypass, the aorta and pulmonary artery were crossclamped, and the heart was isolated. Crystalloid cardioplegia at 4 degrees C containing 10(13) particles of adenovirus encoding LacZ and 15 microg of vascular endothelial growth factor was infused retrograde into the coronary sinus and recirculated for a total of 30 minutes. The dogs were then weaned from cardiopulmonary bypass and allowed to recover. With a catheter, 3 control dogs underwent retrograde infusion of the same cocktail without cardiac isolation or cardiopulmonary bypass. RESULTS: Beta-galactosidase activities in the cardiopulmonary bypass group were several orders of magnitude higher in both the right and left ventricles when compared with those in the control group (P < .05). X-gal staining from the cardiopulmonary bypass group showed unequivocal evidence of myocyte gene expression globally in a significant proportion of cardiac myocytes. No myocyte gene expression was observed in the control group. CONCLUSION: A novel cardiac surgical technique has been developed. This approach with cardiac isolation and retrograde delivery of vector through the coronary sinus results in efficient myocyte transduction in an adult large animal in vivo.

Uniform scale-independent gene transfer to striated muscle after transvenular extravasation of vector.

BACKGROUND: The muscular dystrophies exemplify a class of systemic disorders for which widespread protein replacement in situ is essential for treatment of the underlying genetic disorder. Somatic gene therapy will require efficient, scale-independent transport of DNA-containing macromolecular complexes too large to cross the continuous endothelia under physiological conditions. Previous studies in large-animal models have revealed a trade-off between the efficiency of gene transfer and the inherent safety of the required surgical and pharmacological interventions to achieve this. METHODS AND RESULTS: Rats and dogs underwent limb or hemibody isolation via atraumatic tourniquet placement or myocardial isolation via heterotopic transplantation. Recombinant adenovirus (10(13) particles per kilogram) or recombinant adeno-associated virus (10(14) genome copies/kg) encoding the lacZ transgene was delivered through pressurized venous infusion without pharmacological mediators. Muscle exhibited almost 100% myofiber transduction in rats and dogs by X-galactosidase staining and significantly higher beta-galactosidase levels compared with nonpressurized delivery. No significant difference was seen in beta-galactosidase levels between 100- or 400-mm Hg groups. The <50-mm Hg group yielded inhomogeneous and significantly lower transgene expression. CONCLUSIONS: Uniform scale- and vector-independent skeletal and cardiac myofiber transduction is facilitated by pressurized venous infusion in anatomic domains isolated from the central circulation without pharmacological interference with cardiovascular homeostasis. We provide the first demonstration of uniform gene transfer to muscle fibers of an entire extremity in the dog, providing a firm foundation for further translational studies of efficacy in canine models for human diseases.

Myosin gene mutation correlates with anatomical changes in the human lineage.

Powerful masticatory muscles are found in most primates, including chimpanzees and gorillas, and were part of a prominent adaptation of Australopithecus and Paranthropus, extinct genera of the family Hominidae. In contrast, masticatory muscles are considerably smaller in both modern and fossil members of Homo. The evolving hominid masticatory apparatus--traceable to a Late Miocene, chimpanzee-like morphology--shifted towards a pattern of gracilization nearly simultaneously with accelerated encephalization in early Homo. Here, we show that the gene encoding the predominant myosin heavy chain (MYH) expressed in these muscles was inactivated by a frameshifting mutation after the lineages leading to humans and chimpanzees diverged. Loss of this protein isoform is associated with marked size reductions in individual muscle fibres and entire masticatory muscles. Using the coding sequence for the myosin rod domains as a molecular clock, we estimate that this mutation appeared approximately 2.4 million years ago, predating the appearance of modern human body size and emigration of Homo from Africa. This represents the first proteomic distinction between humans and chimpanzees that can be correlated with a traceable anatomic imprint in the fossil record.

Myosin heavy chain and physiological adaptation of the rat diaphragm in elastase-induced emphysema.

BACKGROUND: Several physiological adaptations occur in the respiratory muscles in rodent models of elastase-induced emphysema. Although the contractile properties of the diaphragm are altered in a way that suggests expression of slower isoforms of myosin heavy chain (MHC), it has been difficult to demonstrate a shift in MHCs in an animal model that corresponds to the shift toward slower MHCs seen in human emphysema. METHODS: We sought to identify MHC and corresponding physiological changes in the diaphragms of rats with elastase-induced emphysema. Nine rats with emphysema and 11 control rats were studied 10 months after instillation with elastase. MHC isoform composition was determined by both reverse transcriptase polymerase chain reaction (RT-PCR) and immunocytochemistry by using specific probes able to identify all known adult isoforms. Physiological adaptation was studied on diaphragm strips stimulated in vitro. RESULTS: In addition to confirming that emphysematous diaphragm has a decreased fatigability, we identified a significantly longer time-to-peak-tension (63.9 +/- 2.7 ms versus 53.9 +/- 2.4 ms). At both the RNA (RT-PCR) and protein (immunocytochemistry) levels, we found a significant decrease in the fastest, MHC isoform (IIb) in emphysema. CONCLUSION: This is the first demonstration of MHC shifts and corresponding physiological changes in the diaphragm in an animal model of emphysema. It is established that rodent emphysema, like human emphysema, does result in a physiologically significant shift toward slower diaphragmatic MHC isoforms. In the rat, this occurs at the faster end of the MHC spectrum than in humans.