The Macrophage Landscape Across the Lifespan of a Human Cardiac Allograft.

BACKGROUND: Much of our knowledge of organ rejection after transplantation is derived from rodent models. METHODS: We used single-nucleus RNA sequencing to investigate the inflammatory myocardial microenvironment in human pediatric cardiac allografts at different stages after transplantation. We distinguished donor- from recipient-derived cells using naturally occurring genetic variants embedded in single-nucleus RNA sequencing data. RESULTS: Donor-derived tissue resident macrophages, which accompany the allograft into the recipient, are lost over time after transplantation. In contrast, monocyte-derived macrophages from the recipient populate the heart within days after transplantation and form 2 macrophage populations: recipient MP1 and recipient MP2. Recipient MP2s have cell signatures similar to donor-derived resident macrophages; however, they lack signatures of pro-reparative phagocytic activity typical of donor-derived resident macrophages and instead express profibrotic genes. In contrast, recipient MP1s express genes consistent with hallmarks of cellular rejection. Our data suggest that recipient MP1s activate a subset of natural killer cells, turning them into a cytotoxic cell population through feed-forward signaling between recipient MP1s and natural killer cells. CONCLUSIONS: Our findings reveal an imbalance of donor-derived and recipient-derived macrophages in the pediatric cardiac allograft that contributes to allograft failure.

Labyrinthine cor triatriatum sinister in fetal hypoplastic left heart syndrome is associated with poor outcomes.

OBJECTIVES: A subset of hypoplastic-left-heart-syndrome (HLHS) fetuses have a complex cor-triatriatum sinister that we named "labyrinthine-cor (L-cor)". We sought to determine the prevalence of L-cor in HLHS fetuses and hypothesized that it is associated with increased mortality. METHODS: This single-center retrospective cohort study included all HLHS fetuses from January 2010-December 2020. Fetuses with other hypoplastic-left-heart variants, inadequate images, lack of follow-up and fetal atrial-septal interventions were excluded. RAS was defined as the ratio of pulmonary-vein forward-to-reverse velocity-time-integral (VTI) ≤ 5 and severe-RAS defined as VTI-ratio <3. Kaplan-Meier survival-analysis was performed for the primary outcome of transplant-free survival for 62 weeks after gestational-age of 30 weeks (∼1 year). RESULTS: Of the 156 consecutive fetuses with HLHS, 11 (7.7%) had L-cor and 8/11 (72.7%) of these had RAS. When compared to HLHS-RAS without L-cor, fetuses with HLHS-RAS and L-cor were less likely to survive to 28 days (87% vs. 62.5%, p = 0.017) and to 1 year (69.6% vs. 25%, p = 0.029). When comparing by survival analysis, fetuses with severe-RAS with L-cor had lower survival compared severe-RAS without L-cor (p = 0.020). CONCLUSION: L-cor in fetal HLHS is associated with increased mortality. Recognition of this finding is important for prognostication and atrial-septal-intervention planning.

Single nucleus transcriptome of a "Super RV" shows increased insulin and angiogenesis signaling.

The right ventricle (RV) is one of the four pumping chambers of the heart, pumping blood to the lungs. In severe forms of congenital heart disease and pulmonary hypertension, the RV is made to pump into the systemic circulation. Such systemic RVs typically display early failure due to pressure overload. In rare cases a systemic RV persists into later decades of life - colloquially called a 'Super RV'. Here we present the single-nucleus transcriptome of a systemic RV from a 60-year-old with congenitally corrected transposition of great arteries (ccTGA). Our data shows two specific signaling pathways enriched in the ccTGA RV myocardium. First, we show increased insulin like growth factor (IGF1) signaling within the systemic RV myocardium: there is increased expression of the main receptor IGFR1 within the cardiomyocytes, and IGF1 ligands within the cardiofibroblasts and macrophages. Second, we find increased VEGF and Wnt9 ligand expression in cardiomyocytes and increased VEGF1R and Wnt9 receptors in endothelial cells, which are implicated in angiogenesis. We show that increased insulin and angiogenesis signaling are potentially beneficial RV adaptations to increased pressure overload. This study of an adult systemic RV provides an important framework for understanding RV remodeling to systemic pressures in congenital heart disease and pulmonary hypertension.

Activated fibroblasts drive cellular interactions in end-stage pediatric hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a relatively rare but debilitating diagnosis in the pediatric population and patients with end-stage HCM require heart transplantation. In this study, we performed single-nucleus RNA sequencing on pediatric HCM and control myocardium. We identified distinct underling cellular processes in pediatric, end-stage HCM in cardiomyocytes, fibroblasts, endothelial cells, and myeloid cells, compared to controls. Pediatric HCM was enriched in cardiomyocytes exhibiting "stressed" myocardium gene signatures and underlying pathways associated with cardiac hypertrophy. Cardiac fibroblasts exhibited clear activation signatures and heightened downstream processes associated with fibrosis, more so than adult counterparts. There was notable depletion of tissue-resident macrophages, and increased vascular remodeling in endothelial cells. Our analysis provides the first single nuclei analysis focused on end-stage pediatric HCM.

Endothelial cells adopt a pro-reparative immune responsive signature during cardiac injury.

Modulation of the heart's immune microenvironment is crucial for recovery after ischemic events such as myocardial infarction (MI). Endothelial cells (ECs) can have immune regulatory functions; however, interactions between ECs and the immune environment in the heart after MI remain poorly understood. We identified an EC-specific IFN responsive and immune regulatory gene signature in adult and pediatric heart failure (HF) tissues. Single-cell transcriptomic analysis of murine hearts subjected to MI uncovered an EC population (IFN-ECs) with immunologic gene signatures similar to those in human HF. IFN-ECs were enriched in regenerative-stage mouse hearts and expressed genes encoding immune responsive transcription factors (Irf7, Batf2, and Stat1). Single-cell chromatin accessibility studies revealed an enrichment of these TF motifs at IFN-EC signature genes. Expression of immune regulatory ligand genes by IFN-ECs suggests bidirectional signaling between IFN-ECs and macrophages in regenerative-stage hearts. Our data suggest that ECs may adopt immune regulatory signatures after cardiac injury to accompany the reparative response. The presence of these signatures in human HF and murine MI models suggests a potential role for EC-mediated immune regulation in responding to stress induced by acute injury in MI and chronic adverse remodeling in HF.

Managing Bilateral Discontinuous Pulmonary Arteries of Ductal Origin in Single-Ventricle Anatomy.

BACKGROUND: We describe outcomes and management strategies for single-ventricle and bilaterally discontinuous pulmonary arteries (PAs) originating from bilateral ductus arteriosus. METHODS: We reviewed 22 patients with aforementioned anatomy and PA centralization from 1995 to 2023, excluding those with biventricular repair. RESULTS: Median age at centralization was 9 days (minimum-maximum, 0 days-2 years). Centralization was performed with systemic-to-pulmonary shunt (n =20 [91%]; 2 after bilateral ductal stents) or bidirectional cavopulmonary connection (n = 2 [9%]) using pericardial roll (n = 14 [64%]), patch-augmented direct anastomosis (n = 7 [32%]), and interposition graft (n = 1 [5%]) techniques. Concurrent total anomalous pulmonary venous connection (TAPVC, n = 11 [50%]) was associated with significantly inferior survival (P = .01). Five patients (23%) died at a median of 59 days (minimum-maximum, 6-257 days) after centralization, all with noncardiac TAPVC. At the latest follow-up for 17 survivors (median, 13.5 years; minimum-maximum, 0.5-25.1 years after centralization), 12 completed Fontan, 4 completed second-stage palliation, and 1 received a transplant before second-stage palliation. PA reintervention was required in 14 patients (64%), including 3 with reoperations independent of staged palliation. Echocardiography from baseline to before the second stage demonstrated branch PA growth with significantly increased diameters (left, P = .0006; right, P = .0002); z-scores significantly increased for right (P = .004) but not left (P = .11). CONCLUSIONS: Successful single-ventricle palliation is possible, although high risk, for patients with bilateral discontinuous ductal PAs. Early postcentralization mortality remains substantial, particularly with associated noncardiac TAPVC. Many require reintervention to maintain PA growth, typically concurrently with staged palliation.

Clinical Presentation, Classification, and Outcomes of Cardiogenic Shock in Children.

BACKGROUND: Despite growing cardiogenic shock (CS) research in adults, the epidemiology, clinical features, and outcomes of children with CS are lacking. OBJECTIVES: This study sought to describe the epidemiology, clinical presentation, hospital course, risk factors, and outcomes of CS among children hospitalized for acute decompensated heart failure (ADHF). METHODS: We examined consecutive ADHF hospitalizations (<21 years of age) from a large single-center retrospective cohort. Patients with CS at presentation were analyzed and risk factors for CS and for the primary outcome of in-hospital mortality were identified. A modified Society for Cardiovascular Angiography and Interventions shock classification was created and patients were staged accordingly. RESULTS: A total of 803 hospitalizations for ADHF were identified in 591 unique patients (median age 7.6 years). CS occurred in 207 (26%) hospitalizations. ADHF hospitalizations with CS were characterized by worse systolic function (P = 0.040), higher B-type natriuretic peptide concentration (P = 0.032), and more frequent early severe renal (P = 0.023) and liver (P < 0.001) injury than those without CS. Children presenting in CS received mechanical ventilation (87% vs 26%) and mechanical circulatory support (45% vs 16%) more frequently (both P < 0.001). Analyzing only the most recent ADHF hospitalization, children with CS were at increased risk of in-hospital mortality compared with children without CS (28% vs 11%; OR: 1.91; 95% CI: 1.05-3.45; P = 0.033). Each higher CS stage was associated with greater inpatient mortality (OR: 2.40-8.90; all P < 0.001). CONCLUSIONS: CS occurs in 26% of pediatric hospitalizations for ADHF and is independently associated with hospital mortality. A modified Society for Cardiovascular Angiography and Interventions classification for CS severity showed robust association with increasing mortality.

Predicting Stroke for Pediatric Patients Supported With Ventricular Assist Devices: A Pedimacs Report.

BACKGROUND: The Pediatric Interagency Registry for Mechanical Circulatory Support (Pedimacs) provides detailed understanding on pediatric patients supported with ventricular assist devices (VADs). We sought to identify important variables affecting the incidence of stroke in pediatric VADs. METHODS: Between 2012 and 2022, 1463 devices in 1219 patients were reported to Pedimacs from 40 centers in patients aged <19 years at their first VAD implantation. Multiphase parametric hazard modeling was used to identify risk factors for stroke among all device types. RESULTS: Of the 1219 patients, the most common devices were implantable continuous (472 [39%]), followed by paracorporeal pulsatile (342 [28%]), and paracorporeal continuous (327 [27%]). Overall freedom from stroke at 6 months was higher in the recent era (2012-2016; 80.2% [95% CI, 77.1%-82.9%] vs 2017-2023; 87.9% [95% CI, 86.2%-89.4%], P = .009). Implantable continuous VADs had the highest freedom from stroke at 3 months (92.7%; 95% CI, 91.1%-93.9%) and 6 months (91.1%; 95% CI, 89.3%-92.6%), followed by paracorporeal pulsatile (87.0% [95% CI, 84.8%-88.9%] and 82.8% [95% CI, 79.8%-85.5%], respectively), and paracorporeal continuous (76.0% [95% CI, 71.8%-79.5%] and 69.5% [95% CI, 63.4%-74.8%], respectively) VADs. Parametric modeling identified risk factors for stoke early after implant and later. Overall, and particularly for paracorporeal pulsatile devices, early stroke risk has decreased in the most recent era (hazard ratio, 5.01). Among implantable continuous devices, cardiogenic shock was the major risk factor. For patients <10 kg, early hazard was only seen in the previous era. For congenital patients, early hazard was seen in nonimplantable device use and use of extracorporeal membrane oxygenation. CONCLUSIONS: The overall stroke rate has decreased from 20% to 15% at 6 months, with particular improvement among paracorporeal pulsatile devices. Risk factor analyses offer insights for identification of higher stroke risk subsets and further management refinements.

Seventh Annual Society of Thoracic Surgeons Pedimacs Report.

BACKGROUND: The Pediatric Interagency Registry for Mechanical Circulatory Support (Pedimacs), supported by The Society of Thoracic Surgeons, provides detailed information on pediatric patients supported with ventricular assist devices (VADs). METHODS: From September 19, 2012, to December 31, 2022, 1463 devices in 1219 patients aged <19 years were reported to the registry from 40 North American hospitals. RESULTS: Cardiomyopathy remains the most common underlying etiology (59%), followed by congenital heart disease (26%) and myocarditis (8%). Implantable continuous devices were most common (39%) type, followed by paracorporeal pulsatile (28%) and paracorporeal continuous (27%) devices. At 6 months after VAD implantation, a favorable outcome (transplant, recovery, or alive on device) was achieved in 85% of patients, which was greatest among those on implantable continuous VADs (92%) and least for paracorporeal continuous VADs (68%), although the patient population supported on these devices is different. CONCLUSIONS: This Seventh Pedimacs Report demonstrates the continued importance of VADs in the treatment of children. With the complexity of cardiac physiologies and sizes of patients, multiple types of devices are used, including paracorporeal continuous, paracorporeal pulsatile, and implantable continuous devices. The preoperative risk factors and differences in patient populations may account for some of the differences in survival observed among these devices. This report, along with other collaborative work, continues to advance the care of this challenging and vulnerable population.

Outcomes in Children Who Undergo Post-cardiotomy ECMO: A Report from the STS-CHSD.

BACKGROUND: Children who undergo cardiac surgery may require post-cardiotomy extracorporeal membrane oxygenation (ECMO). Although morbidities are considerable, our understanding of outcome determinants is limited. We evaluated associations between patient and peri-operative factors with outcomes. METHODS: The STS Congenital Heart Surgery Database was queried for patients <18yo who underwent post-cardiotomy ECMO from 1/2016-6/2021. PRIMARY OUTCOME: survival to hospital discharge. SECONDARY OUTCOME: survival without neurologic injury. Logistic regression for binary outcomes and competing risk analysis for survival were used to identify the most important predictors. Variables were selected by stepwise procedure using entry level p=0.35. Those with p≤0.1 were kept in the final model. RESULTS: A total of 3,181 patients were supported with post-cardiotomy ECMO during the same hospitalization as cardiac surgery: (A) intra-operative initiation of ECMO, n=1206; (B) early post-operative (≤48 hours), n=936; (C) late post-operative (>48 hours), n=1039. Most common primary procedure of index operation was the Norwood procedure. 57% intra-op survived to discharge, versus 59% early post-op and 42% late post-op group (χ2 (2) = 64, p<0.0001, V = 0.14). In all groups, post-op septicemia, cardiac arrest, and new neurologic injury had the strongest association with mortality, while post-operative reintubation and unplanned non-cardiac reoperation were associated with higher survival. CONCLUSIONS: Multiple risk factors impact survival in children who undergo cardiac surgery and post-cardiotomy ECMO. ECMO initiated >48 hours after surgery is associated with the poorest outcomes. This is the first step in creating a predictive tool to educate clinicians and families regarding expectations in this high-risk population.

Deactivation of LVAD support for myocardial recovery-surgical perspectives.

Left ventricular assist devices (LVADs) are excellent therapies for advanced heart failure patients either bridged to transplant or for lifetime use. LVADs also allow for reverse remodeling of the failing heart that is often associated with functional improvement. Indeed, growing enthusiasm exists to better understand this population of patients, whereby the LVAD is used as an adjunct to mediate myocardial recovery. When patients achieve benchmarks suggesting that they no longer need LVAD support, questions related to the discontinuation of LVAD therapy become front and center. The purpose of this review is to provide a surgical perspective on the practical and technical issues surrounding LVAD deactivation.

A prospective multicenter feasibility study of a miniaturized implantable continuous flow ventricular assist device in smaller children with heart failure.

BACKGROUND: There is no FDA-approved left ventricular assist device (LVAD) for smaller children permitting routine hospital discharge. Smaller children supported with LVADs typically remain hospitalized for months awaiting heart transplant-a major burden for families and a challenge for hospitals. We describe the initial outcomes of the Jarvik 2015, a miniaturized implantable continuous flow LVAD, in the NHLBI-funded Pumps for Kids, Infants, and Neonates (PumpKIN) study, for bridge-to-heart transplant. METHODS: Children weighing 8 to 30 kg with severe systolic heart failure and failing optimal medical therapy were recruited at 7 centers in the United States. Patients with severe right heart failure and single-ventricle congenital heart disease were excluded. The primary feasibility endpoint was survival to 30 days without severe stroke or non-operational device failure. RESULTS: Of 7 children implanted, the median age was 2.2 (range 0.7, 7.1) years, median weight 10 (8.2 to 20.7) kilograms; 86% had dilated cardiomyopathy; 29% were INTERMACS profile 1. The median duration of Jarvik 2015 support was 149 (range 5 to 188) days where all 7 children survived including 5 to heart transplant, 1 to recovery, and 1 to conversion to a paracorporeal device. One patient experienced an ischemic stroke on day 53 of device support in the setting of myocardial recovery. One patient required ECMO support for intractable ventricular arrhythmias and was eventually transplanted from paracorporeal biventricular VAD support. The median pump speed was 1600 RPM with power ranging from 1-4 Watts. The median plasma free hemoglobin was 19, 30, 19 and 30 mg/dL at 7, 30, 90 and 180 days or time of explant, respectively. All patients reached the primary feasibility endpoint. Patient-reported outcomes with the device were favorable with respect to participation in a full range of activities. Due to financial issues with the manufacturer, the study was suspended after consent of the eighth patient. CONCLUSION: The Jarvik 2015 LVAD appears to hold important promise as an implantable continuous flow device for smaller children that may support hospital discharge. The FDA has approved the device to proceed to a 22-subject pivotal trial. Whether this device will survive to commercialization remains unclear because of the financial challenges faced by industry seeking to develop pediatric medical devices. (Supported by NIH/NHLBI HHS Contract N268201200001I, clinicaltrials.gov 02954497).