Single-Nucleus RNA Sequencing Reveals Cardiac Macrophage Landscape in Hypoplastic Left Heart Syndrome

Background:Hypoplastic left heart syndrome(HLHS)is one of the most challenging congenital heart diseases in clinical treatment.In cardiac tissues,resident macrophages fulfill critical functions in maintaining a stable cardiac state and have strong regenerative capacity and organ specificity.However,the molecular mechanisms of macro-phages in HLHS remained unclear.Methods:Single-nucleus RNA sequencing(snRNA-seq)data of HLHS and healthy control(donors)samples obtained from the Gene Expression Omnibus(GEO)database were normalized and clustered using the Seurat package.The“FindMarkers”function was used to screen differentially expressed genes(DEGs)between the HLHS and donor groups and to analyze the functional enrichment of the set of genes of interest.Finally,cell-cell communication,pseudotime,and single-cell regulatory network inference and cluster-ing(SCENIC)analyses were used to study the mechanisms of macrophages in HLHS.Results:Based on the snRNA-seq data of HLHS and donors,we identified a total of 9 cell clusters,among which the proportion of macrophages was significantly less in the HLHS group than in the control group.Subdivision of macrophage subpopulations(Macrophages 1,2,and 3)showed that Macrophages 1 was mainly involved in nervous system development,angiogenesis,and apoptotic processes.In addition,analysis of communication between Macro-phages 1 and cardiomyocytes revealed that ligand-acceptor pairs such as GAS6/AXL,IL6,IGF1,THY1,and L1CAM were present only in the donor group.Finally,pesudotime and SCENIC analyses demonstrated that FOXO3 and ELF2 played a critical role for Macrophages 1 to maintain cardiac function in patients with HLHS.Conclusion:Our study improved the current understanding of the molecular mechanisms of macrophage devel-opment in HLHS,showing that manipulating the regulatory role of macrophages in the heart can be a novel treat-ment for HLHS.

A 20-Year Follow-up after the Fontan Operation in a Population with Hypoplastic Left Heart Syndrome

Background:Thromboembolic events are a cause of significant morbidity and mortality in the Fontan population.We previously reported on coagulation profile changes in a cohort of patients with hypoplastic left heart syndrome(HLHS)from Stage I through Fontan completion.In this report,we examine their clinical status,anticoagulation and incidence of thromboembolic events up to 20 years post Fontan.Methods:A retrospective chart review was conducted for twenty(20)surviving patients,from 1998 through December 2020.Patients who underwent orthotopic heart transplantation(OTx)were followed until their transplant.Patients who were found in the original study to have a factor VIII activity level>160%,were examined separately.Results:Most patients had follow-up within the last two years(2018–2020).Two patients underwent OTx and two patients died.Anticoagulation strategy was variable.Most patients were on aspirin monotherapy.There was a total of twelve thrombotic events(63.2%).These included six cerebrovascular accidents(two of which were fatal).Three out of the seven patients with elevated factor VIII activity from the original study had thromboembolic events(42.9%).Fontan complications were variable.Some degree of Fontan Associated Liver Disease was universal.Conclusions:This retrospective review of a group of single-ventricle patients post Fontan,illustrates the variability in anticoagulation therapy that exists in this population.A large proportion of patients suffered a significant thromboembolic event,including the patients with elevated factor VIII.Further investigation into the patients with elevated factor VIII may help determine whether a different antithrombotic strategy post Fontan would be beneficial.

Creation of high position fetal balloon atrial septoplasty for hypoplastic left heart syndrome and highly restrictive atrial septum: A case report and literature review

Background:Fetal balloon atrial septoplasty(BAS)is performed through the restrictive foramen ovale in fetal cases with established hypoplastic left heart syndrome(HLHS)and an intact or highly restrictive atrial septum(RAS).Methods:In the current report,we present a case of high position BAS in a fetus with HLHS/RAS.Results:Echocardiography confirmed an adequate atrial opening above the foramen ovale and fetal pleural effusion resolved spontaneously 1 day after the procedure.Conclusion:To the best of our knowledge,the creation of a high position hole in the thinner part of the atrial septum,instead of the restrictive tiny hole,has not been reported in fetal cases with HLHS/RAS.

Preoperative Feeding in Single Ventricle Neonates is Predictive of Shorter Time to Goal Feed

Background:Patients with single ventricle anatomy are at increased risk of growth failure and malnutrition.Amongst cardiac centers,there is little standardization of feeding practices in this complex population.We hypothesized that initiation of our center’s preoperative feeding protocol would result in decreased gastrostomy tube(G-tube)use,decreased length of stay and would not result in increased Necrotizing Enterocolitis(NEC)rates.Methods:A single institution review of 52 patients who had undergone stage I single ventricle palliative repair was performed.Patient diagnoses were hypoplastic left heart syndrome(39%),atrioventricular canal(15%),and other(46%).Postoperative parameters such as time to goal feed and need for gastrostomy tube(G-tube)were compared among preoperatively fed and non-preoperatively fed groups.Time to goal feed was calculated as time from first postoperative enteral feed to goal volume of 100 mL/kg.Results:Of the 26 patients who met inclusion criteria for preoperative feeding,22 patients(85%)were fed prior to surgery.Cox proportional hazard ratio revealed that age at surgery(p=0.047)and being preoperatively fed(p=0.001)were associated with reaching goal feed sooner.Multivariable analysis revealed that being preoperatively fed made a patient twice as likely to reach goal feed sooner(p=0.047).Univariable logistic regression revealed that days on total parenteral nutrition(p=0.018),length of hospitalization(p=0.008),and time to 1st postoperative feed(p=0.020)were significantly associated with higher odds of needing a G-tube postoperatively.Multivariable logistic regression did not show any predictors of postoperative G-tube usage.However,there was a trend towards lower G-tube usage in the preoperatively fed group.Conclusions:Implementing a standardized preoperative feeding protocol in single ventricle neonates can result in significantly shorter time to goal feed in preoperatively fed patients.It is beneficial for institutions to begin implementing standard feeding protocols to improve nutrition and growth outcomes.

A Ring-Reinforced Right Ventricle to Pulmonary Artery Conduit Is Associated with Better Regional Mechanics after Stage I Norwood Operation

Background:The right ventricle to pulmonary artery conduit(RVPAC)may impair right ventricular(RV)function in patients with functional single right ventricles.Modification of the RVPAC using a ring-reinforced end with dunked insertion into the RV through a limited ventriculotomy may reduce the impact on RV function.We compared RV segmental strain between patients with a traditional RVPAC and ring-reinforced RVPAC using feature tracking cardiovascular magnetic resonance(CMR)imaging.Methods:Patients with CMR examinations after Stage I operation with RVPAC between 2000 and 2018 were reviewed.Ventricular mass,volumes,late gadolinium enhancement(LGE),and peak radial and circumferential strain of the 4 segments near the RVPAC insertion site were analyzed.Results:The study included 71 CMR examinations in 61 patients(30 traditional RVPAC,31 ring-reinforced RVPAC).Prior to Stage II,the ring-reinforced RVPAC group had better peak radial strain and circumferential strain in 1 of 4 segments proximal to the RVPAC insertion site compared to the traditional RVPAC group.Prior to Stage III operation,the ring-reinforced group had better peak radial and circumferential strain in 2 of 4 segments.LGE at the RVPAC insertion site was observed in 97%of patients before Stage II and 95%of patients before Stage III.RVPAC type and regional strain were not associated with transplant-free survival during a median follow-up of 6.3 years.Conclusions:Compared to a traditional RVPAC,the ring-reinforced RVPAC is associated with improved regional mechanics at the conduit insertion site.Further investigation of long-term outcomes after ring-reinforced RVPAC is warranted.

Longitudinal Evaluation of Right Ventricle Function after Right Ventricle-Pulmonary Artery Shunt vs.Blalock-Taussig Shunt

Background:Still little is known about the impact on right ventricle function of the 2 main approaches to Norwood palliation in Hypoplastic left heart syndrome,the right ventricle-pulmonary artery shunt(RVPAS)and the modified Blalock-Taussig shunt(mBTS).Methods:The cohort included 27 patients with Hypoplastic left heart syndrome(10 in the mBTS group,17 in the RVPAS group).Longitudinal strain,tricuspid annulus peak systolic excursion and fractional area change were evaluated before Norwood and in four different breakpoints in the steady-state after Norwood procedure(30-days,90-days,140-days and 200-days after Norwood).Results:No significant differences were found in all standard echocardiographic functional parameters between the two groups at any times.However,when we compared right ventricle function before and after Norwood procedure,longitudinal strain significantly improved in mBTS group compared to pre-surgical assessment(after 90-days:mBTS+27,35%±43,47 vs.RVPAS-8,20%±25,25,p=0,03;after 200-days:mBTS+10.19%±36.58 vs.RVPAS-21.64%±30.43,p=0.04).Conclusion:The mBTS group,which did not receive any ventriculotomy,showed a significant increase in right ventricle longitudinal strain during convalescence.These data support the use of longitudinal strain in Hypoplastic left heart syndrome evaluation and may suggest potential value in terms of cardiac mechanics in using mBTS,preserving the right ventricle integrity.