Prolonged Inotrope Use After Surgery for Congenital Heart Disease: A Common Occurrence with a High Burden of Mortality.

Outcomes in patients requiring prolonged inotropes (PI) following surgery for congenital heart disease (CHD) have not been well studied. We aimed to describe the burden of PI use in the immediate postoperative period after CHD surgery and identify risk factors for in-hospital mortality. We conducted a retrospective cohort study using the Pediatric Health Information System® (PHIS) database. Patients 0-18 years with CHD who underwent cardiovascular surgery from 2010 to 2020 were included. Patients who received inotropic medications for > 7 consecutive days after surgery were in the PI group and all others in the control group. Patients who died before 7 days were excluded. Multivariable mixed-effect logistic regression was used to examine risk factors for in-hospital mortality. There were 110,271 patients from 48 centers included, 10,292 in the PI group and 99,979 in the control group. In-hospital mortality was significantly higher in the PI group (24.9% vs. 4.6%, p < 0.001). Ventricular assist device use was rare (1.6%). After adjustment, odds of in-hospital mortality in the PI group was 3.5 (95% CI 3.3-3.8) times higher than in controls. Independent risk factors for in-hospital mortality were age, non-White race, class of CHD, number of complex chronic conditions, preoperative inotrope, preoperative extracorporeal membrane oxygenation, sepsis, stroke, renal failure, number of inotropes at 7 days, and discharge year (p < 0.01 for all). Postoperative PI use in CHD is common and carries a considerable burden of mortality. Additional work is needed to understand which risk factors are modifiable and which patients may benefit from reintervention or advanced heart failure therapies.

Perioperative management and outcomes for posterior spinal fusion in patients with Friedreich ataxia: A single-center, retrospective study.

BACKGROUND: Friedreich ataxia is a rare genetic disorder associated with progressive mitochondrial dysfunction leading to widespread sequelae including ataxia, muscle weakness, hypertrophic cardiomyopathy, diabetes mellitus, and neuromuscular scoliosis. Children with Friedreich ataxia are at high risk for periprocedural complications during posterior spinal fusion due to their comorbidities. AIM: To describe our single-center perioperative management of patients with Friedreich ataxia undergoing posterior spinal fusion. METHODS: Adolescent patients with Friedreich ataxia presenting for spinal deformity surgery between 2007 and 2023 were included in this retrospective case series performed at the Children's Hospital of Philadelphia. Perioperative outcomes were reviewed along with preoperative characteristics, intraoperative anesthetic management, and postoperative medical management. RESULTS: Seventeen patients were included in the final analysis. The mean age was 15 ± 2 years old and 47% were female. Preoperatively, 35% were wheelchair dependent, 100% had mild-to-moderate hypertrophic cardiomyopathy with preserved systolic function and no left ventricular outflow tract obstruction, 29% were on cardiac medications, and 29% were on pain medications. Intraoperatively, 53% had transesophageal echocardiography monitoring; 12% had changes in volume status on echo but no changes in function. Numerous combinations of total intravenous anesthetic agents were used, most commonly propofol, remifentanil, and ketamine. Baseline neuromonitoring signals were poor in four patients and one patient lost signals, resulting in 4 (24%) wake-up tests. The majority (75%) were extubated in the operating room. Postoperative complications were high (88%) and ranged from minor complications like nausea/vomiting (18%) to major complications like hypotension/tachycardia (29%) and need for extracorporeal membrane oxygenation support in one patient (6%). CONCLUSIONS: Patients with Friedreich ataxia are at high risk for perioperative complications when undergoing posterior spinal fusion and coordinated multidisciplinary care is required at each stage. Future research should focus on the utility of intraoperative echocardiography, optimal anesthetic agent selection, and targeted fluid management to reduce postoperative cardiac complications.

Programmatic Palliative Care Consultations in Pediatric Heart Transplant Evaluations.

Guidelines advocate for integrating palliative care into the management of heart failure (HF) and of children with life-limiting disease. The potential impact of palliative care integration into pediatric HF on patient-centered outcomes is poorly understood. The present study sought to assess the association of programmatic implementation of palliative care into the heart transplant evaluation process with hospital-free days (HFD) and end of life (EOL) treatment choices. The study included patients less than 19 years of age who underwent a heart transplant evaluation between February 2012 and April 2020 at a single center. Patients evaluated in the programmatic palliative care (PPC) era (January 2016-April 2020) were compared to patients evaluated in the pre-PPC era (February 2012-December 2015). The study included 188 patients, with 91 (48%) in the PPC era and 97 (52%) in the pre-PCC era. Children < 1 year of age at the time of the evaluation represented 32% of the cohort. 52% of patients had single ventricle physiology. PPC was not significantly associated with increased HFD (IRR 0.94 [95% CI 0.79-1.2]). PPC was however associated with intensity of EOL care with decreased mechanical ventilation (OR 0.12 [95% CI 0.02-0.789], p = 0.03) and decreased use of ionotropic support (OR 0.13 [95% CI 0.02-0.85], p =0.03). PPC in pediatric heart transplant evaluations may be associated with less invasive interventions at EOL.

Exercise training and NR supplementation to improve muscle mass and fitness in adolescent and young adult hematopoietic cell transplant survivors: a randomized controlled trial {1}.

BACKGROUND: Advances in hematopoietic cell transplantation (HCT) have led to marked improvements in survival. However, adolescents and young adults (AYAs) who undergo HCT are at high risk of developing sarcopenia (loss of skeletal muscle mass) due to the impact of HCT-related exposures on the developing musculoskeletal system. HCT survivors who have sarcopenia also have excess lifetime risk of non-relapse mortality. Therefore, interventions that increase skeletal muscle mass, metabolism, strength, and function are needed to improve health in AYA HCT survivors. Skeletal muscle is highly reliant on mitochondrial energy production, as reflected by oxidative phosphorylation (OXPHOS) capacity. Exercise is one approach to target skeletal muscle mitochondrial OXPHOS, and in turn improve muscle function and strength. Another approach is to use "exercise enhancers", such as nicotinamide riboside (NR), a safe and well-tolerated precursor of nicotinamide adenine dinucleotide (NAD+), a cofactor that in turn impacts muscle energy production. Interventions combining exercise with exercise enhancers like NR hold promise, but have not yet been rigorously tested in AYA HCT survivors. METHODS/DESIGN: We will perform a randomized controlled trial testing 16 weeks of in-home aerobic and resistance exercise and NR in AYA HCT survivors, with a primary outcome of muscle strength via dynamometry and a key secondary outcome of cardiovascular fitness via cardiopulmonary exercise testing. We will also test the effects of these interventions on i) muscle mass via dual energy x-ray absorptiometry; ii) muscle mitochondrial OXPHOS via an innovative non-invasive MRI-based technique, and iii) circulating correlates of NAD+ metabolism via metabolomics. Eighty AYAs (ages 15-30y) will be recruited 6-24 months post-HCT and randomized to 1 of 4 arms: exercise + NR, exercise alone, NR alone, or control. Outcomes will be collected at baseline and after the 16-week intervention. DISCUSSION: We expect that exercise with NR will produce larger changes than exercise alone in key outcomes, and that changes will be mediated by increases in muscle OXPHOS. We will apply the insights gained from this trial to develop individualized, evidence-supported precision initiatives that will reduce chronic disease burden in high-risk cancer survivors. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05194397. Registered January 18, 2022, https://clinicaltrials.gov/ct2/show/NCT05194397 {2a}.

The Hippo pathway mediates Semaphorin signaling.

Semaphorins were originally identified as axonal guidance molecules, but they also control processes such as vascular development and tumorigenesis. The downstream signaling cascades of Semaphorins in these biological processes remain unclear. Here, we show that the class 3 Semaphorins (SEMA3s) activate the Hippo pathway to attenuate tissue growth, angiogenesis, and tumorigenesis. SEMA3B restoration in lung cancer cells with SEMA3B loss of heterozygosity suppresses cancer cell growth via activating the core Hippo kinases LATS1/2 (large tumor suppressor kinase 1/2). Furthermore, SEMA3 also acts through LATS1/2 to inhibit angiogenesis. We identified p190RhoGAPs as essential partners of the SEMA3A receptor PlexinA in Hippo regulation. Upon SEMA3 treatment, PlexinA interacts with the pseudo-guanosine triphosphatase (GTPase) domain of p190RhoGAP and simultaneously recruits RND GTPases to activate p190RhoGAP, which then stimulates LATS1/2. Disease-associated etiological factors, such as genetic lesions and oscillatory shear, diminish Hippo pathway regulation by SEMA3. Our study thus discovers a critical role of Hippo signaling in mediating SEMA3 physiological function.

The evolution of pediatric heart retransplantation over three decades: An analysis from the PHTS.

BACKGROUND: Retransplantation is rare and associated with worse survival and more morbidity. The study aim is to describe an updated cohort of pediatric retransplants, determine if there has been an era effect on outcomes, and understand if identified trends are explained by changes in patient selection. METHODS: Pediatric Heart Transplant Society database analysis of retransplantation patients <18 years of age (Era 1: 1993-2001, Era 2: 2002-2010, Era 3: 2011-2018). Multivariate analysis identified risk factors for graft loss. Multiphase parametric hazard modeling was used to depict era and risk factor effect. RESULTS: Survival was lower (p < .0001) for retransplant (n = 222) compared to primary transplant (n = 6548) (median 9.3 vs 20.2 years). Median survival increased from Era 1 to 2 (4.8 vs 9.3 years; p < .0001) with no incremental change in Era 3. Era 2 and 3 retransplants had a longer inter-transplant interval (p < .0001), were less frequently for early graft failure (p = .0004) or acute rejection (p = .007), more frequently from a ventricular assist device (p = .0014), and less frequently from extracorporeal membrane oxygenation (p = .0024). Predictors of graft loss included Era 1 (HR 10.55, p = .001), congenital heart disease (HR 4.42, p = .01), inter-transplant interval <1 year (HR 5.34, p = .002), and mechanical support (ventricular assist device HR 7.47, p = .0042; extracorporeal membrane oxygenation HR 10.09, p < .0001). For each 1-year increase in inter-transplant interval, graft loss risk decreased by 1.15 (p = .0002). Retransplantation was associated with more rejection, infection, and allograft vasculopathy. CONCLUSIONS: Graft survival has improved in pediatric retransplants making it a viable option in select patients. Retransplantation should be avoided in the setting of early graft failure especially requiring mechanical support.

The Irreversible FLT3 Inhibitor FF-10101 Is Active Against a Diversity of FLT3 Inhibitor Resistance Mechanisms.

Small-molecule FLT3 inhibitors have recently improved clinical outcomes for patients with FLT3-mutant acute myeloid leukemia (AML) after many years of development, but resistance remains an important clinical problem. FF-10101 is the first irreversible, covalent inhibitor of FLT3 which has previously shown activity against FLT3 tyrosine kinase inhibitor resistance-causing FLT3 F691L and D835 mutations. We report that FF-10101 is also active against an expanded panel of clinically identified FLT3 mutations associated with resistance to other FLT3 inhibitors. We also demonstrate that FF-10101 can potentially address resistance mechanisms associated with growth factors present in the bone marrow microenvironment but is vulnerable to mutation at C695, the amino acid required for covalent FLT3 binding. These data suggest that FF-10101 possesses a favorable resistance profile that may contribute to improved single-agent efficacy when used in patients with FLT3-mutant AML.

Adherence With Lipid Screening Guidelines in Children With Acquired and Congenital Heart Disease: An Observational Study Using Data From The MarketScan Commercial and Medicaid Databases.

Background Universal lipid screening in children provides an opportunity to mitigate the lifetime risk of atherosclerosis, particularly in children with chronic conditions that are predisposed to early atherosclerosis. In response, national guidelines recommend additional early screening in a subset of cardiac conditions. The penetration of such guidelines has not been evaluated. Methods and Results We performed a retrospective study of a geographically representative sample of US children using the MarketScan Commercial and Medicaid claims databases. The study population was children with cardiac disease between ages 2 and 18 years and ≥3 years of continuous coverage from January 1, 2013, to June 30, 2018, divided into 4 major strata of heart disease. We assessed the likelihood of screening between these classifications and compared with healthy children and calculated multivariate models to identify patient factors associated with screening likelihood. Of the eligible 8.4 million children, 155 000 children had heart disease, of which 1.8% (31 216) had high-risk conditions. Only 17.5% of healthy children underwent lipid screening. High-risk children were more likely to be screened (odds ratio [OR], 2.1; 95% CI, 2.09-2.19; P<0.001) than standard-risk children, but that likelihood varied depending on strata of cardiac disease (22%-77%). Timing of screening also varied, with most occurring between ages 9 and 11 years. Among cardiac conditions, heart transplantation (OR, 16.8; 95% CI, 14.4-19.7) and cardiomyopathy (OR, 2.9; 95% CI, 2.8-3.1) were associated with the highest likelihood of screening. Conclusions Children with cardiac disease are more likely to undergo recommended lipid screening than healthy children, but at lower rates and later ages than recommended, highlighting the importance of quality improvement and advocacy for this vulnerable population.

Acute Left Ventricular Dysfunction Following Gemtuzumab Ozogamicin in Two Pediatric AML Patients.

Gemtuzumab ozogamicin (GO) is an anti-CD33 antibody-tumor antibiotic conjugate with proven efficacy in pediatric and adult patients with CD33+ acute myeloid leukemia. Adverse effects commonly associated with GO include hyperbilirubinemia, elevated transaminases, and sinusoidal obstruction syndrome. Cardiotoxicity has not been a commonly described adverse event. We describe 2 pediatric patients with relapsed/refractory acute myeloid leukemia who received fractionated GO monotherapy and subsequently developed severe acute left ventricular dysfunction. Both patients achieved remission, recovered cardiac function with medical therapy, and tolerated subsequent stem cell transplantation.

Safety and Feasibility of Exercise Rehabilitation in Children with Ventricular Assist Devices.

Children with advanced heart failure may require ventricular assist devices (VAD) while awaiting heart transplantation. Currently, no data exist regarding the safety of exercise rehabilitation (ER) in children on VAD support. The purpose of this study was to determine the safety and feasibility of ER in children on VAD support awaiting heart transplantation. Eligible patients underwent VAD placement between 1998 and 2019; both inpatient and outpatient participants were included. After VAD implantation and when ambulatory, patients were enrolled in ER. Exercise sessions were scheduled three times a week and consisted of aerobic and musculoskeletal conditioning. A total of 29 patients (59% male, mean age 14 ± 3.2 years) were included with a median VAD duration of 120 ± 109 days. Cardiac diagnoses included cardiomyopathy (81%) and congenital heart disease (19%). VAD type included pulsatile (59%) and continuous-flow devices (41%). Eight hundred and sixty-four (85%) ER sessions were successfully completed and began at a mean of 49 days (range 19-108) after VAD implant. No adverse events, including episodes of hypotension, significant complex arrhythmia, or VAD malfunction occurred during exercise testing or ER, and no sessions were discontinued prematurely. Pediatric patients on VAD support can safely participate in ER with relatively high compliance, and sessions can be implemented early after VAD implantation. Given the safety profile, ER in pediatric VAD recipients, which is a modifiable pre-transplant risk factor that may improve functional capacity, warrants further study as a potential modality to improve post-transplant outcomes.

Cardiopulmonary Exercise Testing in Pediatric Patients With Hypertrophic Cardiomyopathy.

Background: Exercise stress testing (EST) in pediatric hypertrophic cardiomyopathy (HCM) patients has not well described in a large heterogenous cohort. Objectives: The objective of the study was to determine the clinical utility of EST in pediatric HCM. Methods: This was a retrospective single-center analysis of HCM patients younger than 21 years who had EST between January 1, 2000, and January 1, 2019. Clinical, demographic characteristics, and EST data were analyzed, using the last EST during the study or prior to the event in subjects with a primary outcome. The primary composite endpoint included cardiac death, transplant, or arrhythmia requiring implantable cardioverter-defibrillator placement. Outcome analysis was performed using Cox proportional hazard modeling. Results: The study cohort included 140 patients, 52% with a recognized genetic variant. There were 2 tests aborted due to safety concerns (ST-segment changes, ventricular ectopy). The median age at first EST was 13.6 years. Ninety percent of patients were tested using cycle ergometry, and 44% were on a beta-blocker. The median peak oxygen consumption was 37.1 mL/kg/min (IQR: 12.5 mL/kg/min) or 81.2% predicted, the mean anaerobic threshold was 21.8 Ml (IQR: 8.3 mL), and the median peak power was 2.6 ± 1.1 W/kg or 73.7% predicted. Ectopy during EST was seen in 44% of patients, and 8% had an abnormal blood pressure response to exercise. The endpoint was reached in 12 patients. The presence of any degree of ectopy was a predictor of the composite endpoint (hazard ratio: 5.8; 95% CI: 1.3-26.7). Conclusions: EST is clinically useful in select pediatric patients with HCM. Ectopy on EST is a risk factor for cardiac death, cardiac transplant, and arrhythmias requiring implantable cardioverter-defibrillator.

Heat stress activates YAP/TAZ to induce the heat shock transcriptome.

The Hippo pathway plays critical roles in cell growth, differentiation, organ development and tissue homeostasis, whereas its dysregulation can lead to tumorigenesis. YAP and TAZ are transcription co-activators and represent the main downstream effectors of the Hippo pathway. Here, we show that heat stress induces a strong and rapid YAP dephosphorylation and activation. The effect of heat shock on YAP is dominant to other signals known to modulate the Hippo pathway. Heat shock inhibits LATS kinase by promoting HSP90-dependent LATS interaction with and inactivation by protein phosphatase 5. Heat shock also induces LATS ubiquitination and degradation. YAP and TAZ are crucial for cellular heat shock responses, including the heat shock transcriptome and cell viability. This study uncovers previously unknown mechanisms of Hippo regulation by heat shock, as well as physiological functions of YAP, in the heat stress response. Our observations also reveal a potential combinational therapy involving hyperthermia and targeting of the Hippo pathway.

Cardiomyopathy in Children: Classification and Diagnosis: A Scientific Statement From the American Heart Association.

In this scientific statement from the American Heart Association, experts in the field of cardiomyopathy (heart muscle disease) in children address 2 issues: the most current understanding of the causes of cardiomyopathy in children and the optimal approaches to diagnosis cardiomyopathy in children. Cardiomyopathies result in some of the worst pediatric cardiology outcomes; nearly 40% of children who present with symptomatic cardiomyopathy undergo a heart transplantation or die within the first 2 years after diagnosis. The percentage of children with cardiomyopathy who underwent a heart transplantation has not declined over the past 10 years, and cardiomyopathy remains the leading cause of transplantation for children >1 year of age. Studies from the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry have shown that causes are established in very few children with cardiomyopathy, yet genetic causes are likely to be present in most. The incidence of pediatric cardiomyopathy is ≈1 per 100 000 children. This is comparable to the incidence of such childhood cancers as lymphoma, Wilms tumor, and neuroblastoma. However, the published research and scientific conferences focused on pediatric cardiomyopathy are sparcer than for those cancers. The aim of the statement is to focus on the diagnosis and classification of cardiomyopathy. We anticipate that this report will help shape the future research priorities in this set of diseases to achieve earlier diagnosis, improved clinical outcomes, and better quality of life for these children and their families.

Significant mortality, morbidity and resource utilization associated with advanced heart failure in congenital heart disease in children and young adults.

BACKGROUND: Children with congenital heart disease (CHD) are at risk for advanced heart failure (AHF). We sought to define the mortality and resource utilization in CHD-related AHF in children and young adults. METHODS: All hospitalizations in the Pediatric Health Information System database involving patients ≤21 years old with a CHD diagnosis and heart failure requiring at least 7 days of continuous inotropic support between 2004 and 2015 were included. Hospitalizations including CHD surgery were excluded. RESULTS: Of 465,482 CHD hospitalizations, AHF was present in 2,712 (0.6%) [58% infant, 55% male, 30% single ventricle]. AHF therapies frequently used included extracorporeal membrane oxygenation (ECMO) (15%) and cardiac transplant (16%). Ventricular assist device (VAD) support was rare (3%), although VAD use significantly increased from 2004 to 2015 (P < .0010). Hospital mortality in CHD with AHF was 26%, with higher mortality associated with single ventricle heart disease (OR 1.64, 95% CI 1.23-2.19; P = .0009), infancy (OR 1.71, 95% CI 1.17-2.5; P = .0057), non-white race (OR 1.28, 95% CI 1.04-1.59; p=0.0234), and chronic complex comorbidities (OR 1.76, 95% CI 1.34-2.30; P < .0001). Over the 11-year study period, despite the significant increase in CHD-related AHF hospitalizations (P < .0001), hospital mortality improved (P = .0011). Median hospital costs were $252,000, a 6-fold increase above those without AHF, and was primarily driven by hospital length of stay (P < .0001). CONCLUSION: AHF in children with CHD in uncommon but increasing and is associated with significant morbidity, mortality and resource utilization. Approximately 1 in 5 children do not survive to hospital discharge. Many risk factors for mortality may not be modifiable, and further study is needed to identify modifiable risk factors and improve care for this complex population.

Mortality, Resource Utilization, and Inpatient Costs Vary Among Pediatric Heart Transplant Indications: A Merged Data Set Analysis From the United Network for Organ Sharing and Pediatric Health Information Systems Databases.

BACKGROUND: Merging United Network for Organ Sharing (UNOS) and Pediatric Health Information Systems databases has enabled a more granular analysis of pediatric heart transplant outcomes and resource utilization. We evaluated whether transplant indication at time of transplantation was associated with mortality, resource utilization, and inpatient costs during the first year after transplantation. METHODS AND RESULTS: We analyzed transplant outcomes and resource utilization from 2004 to 2015. Patients were categorized as congenital (CHD), myocarditis, or cardiomyopathy based on UNOS-defined primary indication. CHD complexity subgroup analyses (single-ventricle, complex, and simple biventricular CHD) were also performed. Of 2251 transplants (49% CHD, 5% myocarditis, 46% cardiomyopathy), CHD recipients were younger (2 [IQR 0-10], 6 [IQR 0-12], and 7 [IQR 1-14] years, respectively; P < .001) and less likely to have a ventricular assist device (VAD) at transplantation (3%, 27%, and 13%, respectively; P < .001). Patients with single-ventricle CHD had the longest time on the waitlist and were least likely to receive a VAD before transplantation. After adjusting for patient-level factors, transplant recipients with single-ventricle CHD had the greatest mortality during transplantation admission and within 1 year (odds ratio [OR] 11.8 [95% confidence interval (CI) 5.9-23.6] and OR 6.0 [95% CI 3.6-10.2], respectively, vs cardiomyopathy). Mortality was similar between patients with myocarditis and cardiomyopathy. Post-transplantation length of stay (LOS) was longer in transplant recipients with CHD than myocarditis or cardiomyopathy (25 [interquartile range [IQR] 15-45] vs 21 [IQR 12-35] vs 16 [IQR 12-25] days; P < .001), related in part to longer duration of intensive care unit-level care (ICU LOS 8 [IQR 4-20] vs 6 [IQR 4-13] vs 5 [IQR 3-8] days; P < .001). Similarly, patients with CHD had higher median post-transplantation costs than myocarditis or cardiomyopathy ($415K [IQR $201K-503K] vs $354K [IQR $179K-390K] vs $284K [IQR $145K-319K]; P < .001) that persisted after adjusting for patient-level factors (adjusted cost ratio 1.4 [95% CI 1.4-1.5], CHD vs cardiomyopathy) and was primarily driven by longer LOS. More than 50% were readmitted during the first year after transplantation, although readmission rates were similar across transplant indications (P = .42). CONCLUSIONS: Children with CHD, particularly single-ventricle patients, require substantially greater hospital resource utilization and have significantly worse outcomes during the first year after heart transplantation compared with other indications. Further work is aimed at identifying modifiable pre-transplantation risk factors, such as pre-transplantation conditioning with VAD support and cardiac rehabilitation, to improve post-transplantation outcomes and reduce resource utilization in this complex population.

RAP2 mediates mechanoresponses of the Hippo pathway.

Mammalian cells are surrounded by neighbouring cells and extracellular matrix (ECM), which provide cells with structural support and mechanical cues that influence diverse biological processes1. The Hippo pathway effectors YAP (also known as YAP1) and TAZ (also known as WWTR1) are regulated by mechanical cues and mediate cellular responses to ECM stiffness2,3. Here we identified the Ras-related GTPase RAP2 as a key intracellular signal transducer that relays ECM rigidity signals to control mechanosensitive cellular activities through YAP and TAZ. RAP2 is activated by low ECM stiffness, and deletion of RAP2 blocks the regulation of YAP and TAZ by stiffness signals and promotes aberrant cell growth. Mechanistically, matrix stiffness acts through phospholipase Cγ1 (PLCγ1) to influence levels of phosphatidylinositol 4,5-bisphosphate and phosphatidic acid, which activates RAP2 through PDZGEF1 and PDZGEF2 (also known as RAPGEF2 and RAPGEF6). At low stiffness, active RAP2 binds to and stimulates MAP4K4, MAP4K6, MAP4K7 and ARHGAP29, resulting in activation of LATS1 and LATS2 and inhibition of YAP and TAZ. RAP2, YAP and TAZ have pivotal roles in mechanoregulated transcription, as deletion of YAP and TAZ abolishes the ECM stiffness-responsive transcriptome. Our findings show that RAP2 is a molecular switch in mechanotransduction, thereby defining a mechanosignalling pathway from ECM stiffness to the nucleus.

The Hippo pathway effector proteins YAP and TAZ have both distinct and overlapping functions in the cell.

The Hippo pathway plays an important role in regulating tissue homeostasis, and its effectors, the transcriptional co-activators Yes-associated protein (YAP) and WW domain-containing transcription regulator 1 (WWTR1 or TAZ), are responsible for mediating the vast majority of its physiological functions. Although YAP and TAZ are thought to be largely redundant and similarly regulated by Hippo signaling, they have developmental, structural, and physiological differences that suggest they may differ in their regulation and downstream functions. To better understand the functions of YAP and TAZ in the Hippo pathway, using CRISPR/Cas9, we generated YAP KO, TAZ KO, and YAP/TAZ KO cell lines in HEK293A cells. We evaluated them in response to many environmental conditions and stimuli and used RNA-Seq to compare their transcriptional profiles. We found that YAP inactivation has a greater effect on cellular physiology (namely, cell spreading, volume, granularity, glucose uptake, proliferation, and migration) than TAZ inactivation. However, functional redundancy between YAP and TAZ was also observed. In summary, our findings confirm that the Hippo pathway effectors YAP and TAZ are master regulators for multiple cellular processes but also reveal that YAP has a stronger influence than TAZ.

Cardiac Profile of Chimeric Antigen Receptor T Cell Therapy in Children: A Single-Institution Experience.

Immunotherapy with chimeric antigen receptor (CAR)-modified T cells targeting CD19 for pediatric acute lymphoblastic leukemia (ALL) has demonstrated significant efficacy. The principle toxicity is cytokine release syndrome with resultant hypotension. However, the spectrum of cardiovascular effects associated with CAR T cell therapy has not been systematically evaluated. We reviewed all patients who received CD19-directed CAR T cells at the Children's Hospital of Philadelphia between April 2012 and September 2016. The primary endpoint was hypotension-requiring inotropic support. Secondary endpoints included echocardiographic dysfunction at discharge and 6-month follow-up. Descriptive and univariate analyses were performed, and 98 encounters were included (55% male patients; mean age, 11.8 years [range, 1.7 to 27.1]); 98% had B-ALL. Before infusion 10 had cardiomyopathy and 1 had single-ventricle physiology. Primary endpoint occurred in 24 patients with mean onset 4.6 days (range, 1 to 9) after CAR T cell infusion, including 6 patients receiving milrinone. Worsened systolic function occurred in 10 patients; there were no cardiac-related deaths. Pretreatment factors associated with primary endpoint included higher pretreatment blast percentage on bone marrow biopsy (blast > 25%: odds ratio, 15.5; 95% confidence interval, 5.1 to 47.1; P < .001) and baseline lower ejection fraction (P = .019) or diastolic dysfunction (P = .021); neither pre-existing cardiomyopathy (P = .062), total body irradiation (P = .629), nor anthracycline dose (P = .444) were associated. At discharge, 7 patients had worsened echocardiographic function, but persistent dysfunction by the 6-month follow-up was rare. Pretreatment factors were not associated with persistent dysfunction at discharge. This is the first study to describe the cardiovascular effects of pediatric CAR T cell therapy. Although 10% had new systolic dysfunction after treatment, persistence was rare. Pretreatment blast count > 25% or pre-existing cardiac dysfunction increased the risk for hypotension-requiring inotropic support; these patients may warrant close observation.

Cumulative Effect of Preoperative Risk Factors on Mortality After Pediatric Heart Transplantation.

BACKGROUND: Risk assessment in heart transplantation is critical for candidate selection, but current models inadequately assess individual risk of postoperative mortality. We sought to identify risk factors and develop a scoring system to predict mortality after heart transplantation in children. METHODS: The records of patients undergoing heart transplantation at our institution from 2010 through 2016 were reviewed. Clinical characteristics were recorded and compared between survivors and nonsurvivors. We used Cox proportional hazard modeling of factors associated with postoperative mortality to develop a risk factor score. RESULTS: There were 74 patients who underwent heart transplantation at a mean age of 8.8 ± 6.6 years. Congenital heart disease was the most common indication, comprising 48.6% of the cohort. Overall mortality was 18.9%, with 10 of 14 dying within 30 days of the operation or during the initial postoperative admission (early mortality). Preoperative factors associated with overall mortality were single-ventricle congenital heart disease (hazard ratio [HR], 3.2; p = 0.042), biventricular assist device (HR, 4.8; p = 0.043), history of four or more sternotomies (HR, 3.9; p = 0.023), panel reactive antibody exceeding 10% (HR, 4.4; p = 0.013), any previous operation at another institution (HR, 3.2; p = 0.038), and pulmonary vein disease (HR, 4.7; p = 0.045). Each risk factor was assigned a point value, based on similar magnitude of the HRs. A score of 4 or higher predicted mortality with 57% sensitivity and 90% specificity. CONCLUSIONS: In this single-center pediatric cohort, postheart transplantation mortality could be predicted using patient-specific risk factors. The cumulative effect of these risk factors predicted mortality with high specificity.

Heart failure after the Norwood procedure: An analysis of the Single Ventricle Reconstruction Trial.

BACKGROUND: Heart failure results in significant morbidity and mortality in young children with hypoplastic left heart syndrome (HLHS) after the Norwood procedure. METHODS: We studied subjects enrolled in the prospective Single Ventricle Reconstruction (SVR) Trial who survived to hospital discharge after a Norwood operation and were followed up to age 6 years. The primary outcome was heart failure, defined as heart transplant listing after Norwood hospitalization, death attributable to heart failure, or symptomatic heart failure (New York Heart Association [NYHA] Class IV). Multivariate modeling was undertaken using Cox regression methodology to determine variables associated with heart failure. RESULTS: Of the 461 subjects discharged home following a Norwood procedure, 66 (14.3%) met the criteria for heart failure. Among these, 15 died from heart failure, 39 were listed for transplant (22 had a transplant, 12 died after listing, and 5 were alive and not yet transplanted), and 12 had NYHA Class IV heart failure but were never listed. The median age at heart failure identification was 1.28 (interquartile range 0.30 to 4.69) years. Factors associated with early heart failure included post-Norwood lower fractional area change, need for extracorporeal membrane oxygenation, non-Hispanic ethnicity, Norwood perfusion type, and total support time (p < 0.05). CONCLUSIONS: By 6 years of age, heart failure developed in nearly 15% of children after the Norwood procedure. Although transplant listing was common, many patients died from heart failure before receiving a transplant or without being listed. Shunt type did not impact the risk of developing heart failure.