The rules by which neuronal activity causes long-term modification of synapses in the central nervous system are not fully understood. Whereas competitive or correlation-based rules result in local modification of synapses, homeostatic modifications allow neuron-wide changes in synaptic strength, promoting stability. Experimental investigations of these rules at central nervous system synapses have relied generally on manipulating activity in populations of neurons. Here, we investigated the effect of suppressing excitability in single neurons within a network of active hippocampal neurons by overexpressing an inward-rectifier potassium channel. Reducing activity in a neuron before synapse formation leads to a reduction in functional synaptic inputs to that neuron; no such reduction was observed when activity of all neurons was uniformly suppressed. In contrast, suppressing activity in a single neuron after synapses are established results in a homeostatic increase in synaptic input, which restores the activity of the neuron to control levels. Our results highlight the differences between global and selective suppression of activity, as well as those between early and late manipulation of activity.

BackgroundCongestive hepatopathy is a recognized complication of Fontan physiology. Data regarding the incidence of hepatopathy and risk factors are lacking.Methods and ResultsLiver biopsies and cardiac catherizations were performed as part of an evaluation offered to all patients ≥10 years after Fontan. Quantitative determination of hepatic fibrosis was performed using Sirius red staining with automated calculation of collagen deposition per slide (%CD). Biopsies from included subjects were compared to stained specimens from controls without known fibrotic liver disease. Patient characteristics, echocardiographic findings, and hemodynamic measures were evaluated as potential risk factors. The cohort consisted of 67 patients (31 female) at mean age of 17.3±4.5 years and mean time from Fontan of 14.9±4.5 years. Right ventricular morphology was present in 37 subjects. Median %CD by Sirius red staining was 21.6% (range 8.7% to 49.4%) compared to 2.6% (range 2.2% to 3.0%) in controls. There was a significant correlation between time from Fontan and degree of Sirius red staining (r=0.33, P<0.01). Serum liver enzymes and platelet count did not correlate with %CD. The median inferior vena cava pressure was 13 mm Hg (range 6‐24 mm Hg) and did not correlate with %CD. There was no difference in %CD based on ventricular morphology or severity of atrioventricular valve insufficiency.ConclusionsIn this cohort of predominantly asymptomatic children and adolescents electively evaluated after a Fontan operation, all exhibited evidence for hepatic fibrosis as measured by collagen deposition in the liver. Time from Fontan was the only factor significantly associated with collagen deposition. These findings demonstrate that liver fibrosis is an inherent feature of Fontan physiology and that the degree of fibrosis increases over time.

Background:The Fontan operation is performed for surgical palliation of single ventricle physiology. This operation is usually preceded by a superior cavopulmonary connection (SCPC); lymphatic abnormalities after SCPC may be demonstrated at MRI and prior to the Fontan operation.Purpose: To determine if the degree of neck and thoracic lymphatic abnormalities at T2-weighted MRI in patients after superior cavopulmonary connection (SCPC) correlated with surgical outcomes from the Fontan procedure. Materials and Methods:Patients for whom SCPC was performed for palliation of single ventricle disease who underwent chest MRI between July 2012 and May 2015 at a single institution were retrospectively reviewed. T2-weighted images were scored as lymphatic type 1 (little or no T2 mediastinal and supraclavicular signal) to type 4 (T2 signal into both the mediastinum and the lung parenchyma). Fontan takedown, duration of post-Fontan hospitalization and pleural effusion, postoperative plastic bronchitis, need for transplant, and mortality were tabulated. The relationship between lymphatic type and clinical outcomes was evaluated by using analysis of variance (ANOVA), the Kruskal-Wallis H test, and the Fisher exact test.Results: A total of 83 patients (mean age, 7.9 years 6 2.6) were evaluated. Among these 83 patients, 53 (64%) were classified with type 1 or 2 lymphatic abnormalities, 17 (20%) with type 3, and 12 (16%) with type 4. The rate of failure of Fontan completion was higher in patients with type 4 than in type 1 or 2 (54% vs 2%, respectively; P = .004). Need for cardiac transplant (one of 13 [8%]) and death (three of 13 [23%]) occurred only in type 4. Median postoperative length of stay was longer for patients with type 4 than for those with types 1 or 2 (29 days vs 9 days, respectively; P , .01). Conclusion:Greater MRI-based severity of lymphatic abnormalities in patients prior to planned Fontan procedure was associated with failure of Fontan completion and longer postoperative stay.

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Background Recent studies suggest that lymphatic congestion plays a role in development of late Fontan complications, such as protein‐losing enteropathy. However, the role of the lymphatic circulation in early post‐Fontan outcomes is not well defined. Methods and Results This was a retrospective, single‐center study of patients undergoing first‐time Fontan completion from 2012 to 2017. The primary outcome was early Fontan complication ≤6 months after surgery, a composite of death, Fontan takedown, extracorporeal membrane oxygenation, chest tube drainage >14 days, cardiac catheterization, readmission, or transplant. Complication causes were assigned to 1 of 4 groups: (1) Fontan circuit obstruction, (2) ventricular dysfunction or atrioventricular valve regurgitation, (3) persistent pleural effusions in the absence of Fontan obstruction or ventricular dysfunction, and (4) chylothorax or plastic bronchitis. T2‐weighted magnetic resonance imaging sequences were used to assess for lymphatic perfusion abnormality. The cohort consisted of 238 patients. Fifty‐eight (24%) developed early complications: 20 of 58 (34.5%) in group 1, 8 of 58 (14%) in group 2, 18 of 58 (31%) in group 3, and 12 of 58 (20%) in group 4. Preoperative T2 imaging was available for 126 (53%) patients. Patients with high‐grade lymphatic abnormalities had 6 times greater odds of developing early complications ( P =0.001). Conclusions There is substantial morbidity in the early post‐Fontan period. Half of those who developed early complications had lymphatic failure or persistent effusions unrelated to structural or functional abnormalities. Preoperative T2 imaging demonstrated that patients with higher‐grade lymphatic perfusion abnormalities were significantly more likely to develop early complications. This has implications for risk stratification and optimization of patients before Fontan palliation.

Objective The impact of genotype on outcomes of infant cardiac operations is not well established. The purpose of this study was to investigate the impact of 22q11.2 deletion (22q11del) on infants with truncus arteriosus communis (TA) and interrupted aortic arch (IAA) undergoing operative correction during infancy. Methods We conducted a retrospective cohort study of all infants who underwent operative correction of TA or IAA at The Children’s Hospital of Philadelphia from 1995 to 2007, comparing peri-operative outcomes (hospital length of stay, intensive care, and mechanical ventilation, risk of cardiac and non-cardiac events, number of consultations, and number of discharge medications) by 22q11del status. Results A total of 104 patients were studied (55 with TA and 49 with IAA), of which 40 (38%) were 22q11del positive. 22q11del status was unknown in 9 cases (7 with TA and 2 with IAA). In patients with known deletion status, those with 22q11del had a longer hospital length of stay and duration of intensive care. Subjects with 22q11del also underwent more frequent operative re-intervention, underwent more consultations, and were prescribed more medications at discharge. There was no significant difference in method of feeding between those with and without 22q11del at discharge. Conclusions 22q11del is associated with perioperative outcomes in infants undergoing operative correction of TA and IAA, with longer hospital stay and greater resource utilization in the perioperative period. These findings inform counseling and risk stratification and warrant further study to identify genotype specific management strategies to improve outcomes.

Pediatric patients requiring a pretransplantation ventricular assist device have long-term survival similar to that of patients not receiving mechanical circulatory support. Early survival among patients undergoing extracorporeal membrane oxygenation and infants is poor, reinforcing the need for improvements in device design and physiologic management of infants and neonates.

Background Cardiac catheterization is the standard of care procedure for diagnosis, choice of therapy, and longitudinal follow-up of children and adults with pulmonary hypertension (PH). However, the procedure is invasive and has risks associated with both the procedure and recovery period. Objectives Identify risk factors for catastrophic adverse outcome in children with PH undergoing cardiac catheterization. Methods We studied children and young adults 0-21 years of age with PH undergoing ≥1 cardiac catheterizations at centers participating in the Pediatric Health Information Systems (PHIS) database between 2007 and 2012. Using mixed effects multivariable regression, we assessed the association between pre-specified subject- and procedure-level covariates and the risk of the composite outcome of death and/or initiation of mechanical circulatory support within 1 day of cardiac catheterization after adjustment for patient- and procedure-level factors. Results 6,339 procedures performed on 4,401 patients with a diagnosis of PH from 38/43 centers contributing data to the PHIS database were included. The observed risk of composite outcome was 3.5%. In multivariate modeling, the adjusted risk of the composite outcome was 3.3%. Younger age at catheterization, cardiac operation in the same admission as the catheterization, pre-procedural systemic vasodilator infusion, and hemodialysis were independently associated with an increased risk of adverse outcomes. Pre-procedure use of pulmonary vasodilators was associated with reduced risk of composite outcome. Conclusions The risk of cardiac catheterization in children and young adults with PH is high relative to previously reported risk in other pediatric populations. The risk is influenced by patient-level factors. Further research is necessary to determine whether knowledge of these factors can be translated into practices that improve outcomes for children with PH.