Spatially resolved multiomics of human cardiac niches.

The function of a cell is defined by its intrinsic characteristics and its niche: the tissue microenvironment in which it dwells. Here we combine single-cell and spatial transcriptomics data to discover cellular niches within eight regions of the human heart. We map cells to microanatomical locations and integrate knowledge-based and unsupervised structural annotations. We also profile the cells of the human cardiac conduction system1. The results revealed their distinctive repertoire of ion channels, G-protein-coupled receptors (GPCRs) and regulatory networks, and implicated FOXP2 in the pacemaker phenotype. We show that the sinoatrial node is compartmentalized, with a core of pacemaker cells, fibroblasts and glial cells supporting glutamatergic signalling. Using a custom CellPhoneDB.org module, we identify trans-synaptic pacemaker cell interactions with glia. We introduce a druggable target prediction tool, drug2cell, which leverages single-cell profiles and drug-target interactions to provide mechanistic insights into the chronotropic effects of drugs, including GLP-1 analogues. In the epicardium, we show enrichment of both IgG+ and IgA+ plasma cells forming immune niches that may contribute to infection defence. Overall, we provide new clarity to cardiac electro-anatomy and immunology, and our suite of computational approaches can be applied to other tissues and organs.

Single-cell transcriptomics for the assessment of cardiac disease.

Cardiovascular disease is the leading cause of death globally. An advanced understanding of cardiovascular disease mechanisms is required to improve therapeutic strategies and patient risk stratification. State-of-the-art, large-scale, single-cell and single-nucleus transcriptomics facilitate the exploration of the cardiac cellular landscape at an unprecedented level, beyond its descriptive features, and can further our understanding of the mechanisms of disease and guide functional studies. In this Review, we provide an overview of the technical challenges in the experimental design of single-cell and single-nucleus transcriptomics studies, as well as a discussion of the type of inferences that can be made from the data derived from these studies. Furthermore, we describe novel findings derived from transcriptomics studies for each major cardiac cell type in both health and disease, and from development to adulthood. This Review also provides a guide to interpreting the exhaustive list of newly identified cardiac cell types and states, and highlights the consensus and discordances in annotation, indicating an urgent need for standardization. We describe advanced applications such as integration of single-cell data with spatial transcriptomics to map genes and cells on tissue and define cellular microenvironments that regulate homeostasis and disease progression. Finally, we discuss current and future translational and clinical implications of novel transcriptomics approaches, and provide an outlook of how these technologies will change the way we diagnose and treat heart disease.

Erratum: Author Correction: A single-cell comparison of adult and fetal human epicardium defines the age-associated changes in epicardial activity.

[This corrects the article DOI: 10.1038/s44161-022-00183-w.].

Pathogenic variants damage cell composition and single cell transcription in cardiomyopathies.

Pathogenic variants in genes that cause dilated cardiomyopathy (DCM) and arrhythmogenic cardiomyopathy (ACM) convey high risks for the development of heart failure through unknown mechanisms. Using single-nucleus RNA sequencing, we characterized the transcriptome of 880,000 nuclei from 18 control and 61 failing, nonischemic human hearts with pathogenic variants in DCM and ACM genes or idiopathic disease. We performed genotype-stratified analyses of the ventricular cell lineages and transcriptional states. The resultant DCM and ACM ventricular cell atlas demonstrated distinct right and left ventricular responses, highlighting genotype-associated pathways, intercellular interactions, and differential gene expression at single-cell resolution. Together, these data illuminate both shared and distinct cellular and molecular architectures of human heart failure and suggest candidate therapeutic targets.

Impact of COVID-19 pandemic on cardiac rhythm management services: Views from the United Kingdom.

Background: Effects of the COVID-19 pandemic on cardiac rhythm management (CRM) services remain poorly quantified. Objective: To describe the impact of COVID-19 on specialist CRM centers in the United Kingdom (UK). Methods: Two-center study involving the Liverpool Heart and Chest Hospital NHS Foundation Trust and Royal Papworth Hospital NHS Foundation Trust. The first nationwide lockdown lasted from April to July 2020 and the second from December 2020 to March 2021. Results: Compared to the pre-pandemic period, pandemic 1 (April-July 2020) was associated with a 52.2% reduction in electrophysiology (EP) procedures (P = .083), 32.7% reduction in device procedures (P = .003), and 36.8% decrease in CRM referrals (P < .001). There was also a 13.4% increase in the use of conscious sedation (CS) (P < .001) and day-case procedures for EP (P = .003), with no change in day-case device procedures (P = .555). Corresponding numbers for pandemic 2 (August-November 2020) were a 0.7% increase in EP procedures (P = .925), 7.9% reduction in device procedures (P = .232), 13.9% decrease in referrals (P = .014), 5.5% increase in CS for EP (P = .009), 7.1% increase in day-case EP procedures (P < .001), and no change in day-case device procedures (P = .537). Corresponding numbers for pandemic 3 (December 2020-March 2021) were a 31.6% reduction in EP procedures (P = .001), 22.3% reduction in device procedures (P = .006), 8.4% decrease in referrals (P = .094), 11.0% increase in CS for EP (P < .001), 7.6% increase in day-case EP procedures (P = .003), and no change in day-case device procedures (P = .146). By the end of March 2021, the CRM waiting list was 167.8% pre-pandemic levels. Conclusion: During the COVID-19 pandemic, specialist centers in the UK were affected such that the number of procedures performed was greatly reduced in the initial period with latter improvements as better coping strategies were developed.

A single-cell comparison of adult and fetal human epicardium defines the age-associated changes in epicardial activity.

Re-activating quiescent adult epicardium represents a potential therapeutic approach for human cardiac regeneration. However, the exact molecular differences between inactive adult and active fetal epicardium are not known. In this study, we combined fetal and adult human hearts using single-cell and single-nuclei RNA sequencing and compared epicardial cells from both stages. We found that a migratory fibroblast-like epicardial population only in the fetal heart and fetal epicardium expressed angiogenic gene programs, whereas the adult epicardium was solely mesothelial and immune responsive. Furthermore, we predicted that adult hearts may still receive fetal epicardial paracrine communication, including WNT signaling with endocardium, reinforcing the validity of regenerative strategies that administer or reactivate epicardial cells in situ. Finally, we explained graft efficacy of our human embryonic stem-cell-derived epicardium model by noting its similarity to human fetal epicardium. Overall, our study defines epicardial programs of regenerative angiogenesis absent in adult hearts, contextualizes animal studies and defines epicardial states required for effective human heart regeneration.

Pulsed Levosimendan in advanced heart failure due to congenital heart disease: a case series.

BACKGROUND: Levosimendan is a non-adrenergic calcium-sensitizing agent with positive inotropic and vasodilatory effects. Its use in acute decompensation of heart failure is established. Good evidence now exists for repetitive infusions of Levosimendan to improve symptoms and reduce hospitalization in advanced heart failure (AdHF) populations. Its use in heart failure resulting from congenital heart disease is not yet commonplace. CASE SUMMARY: We present three cases in which pulsed Levosimendan was used in the management of AdHF secondary to underlying congenital heart disease. There was symptomatic and biomarker evidence of improvement. DISCUSSION: Intermittent Levosimendan may represent a valuable therapy to reduce hospitalization and improve quality of life in adults with congenital heart conditions.

Multi-ancestry GWAS of the electrocardiographic PR interval identifies 202 loci underlying cardiac conduction.

The electrocardiographic PR interval reflects atrioventricular conduction, and is associated with conduction abnormalities, pacemaker implantation, atrial fibrillation (AF), and cardiovascular mortality. Here we report a multi-ancestry (N = 293,051) genome-wide association meta-analysis for the PR interval, discovering 202 loci of which 141 have not previously been reported. Variants at identified loci increase the percentage of heritability explained, from 33.5% to 62.6%. We observe enrichment for cardiac muscle developmental/contractile and cytoskeletal genes, highlighting key regulation processes for atrioventricular conduction. Additionally, 8 loci not previously reported harbor genes underlying inherited arrhythmic syndromes and/or cardiomyopathies suggesting a role for these genes in cardiovascular pathology in the general population. We show that polygenic predisposition to PR interval duration is an endophenotype for cardiovascular disease, including distal conduction disease, AF, and atrioventricular pre-excitation. These findings advance our understanding of the polygenic basis of cardiac conduction, and the genetic relationship between PR interval duration and cardiovascular disease.

Catastrophic antiphospholipid syndrome causing ST-segment elevation myocardial infarction with non-obstructive coronary arteries.

A 51-year-old woman with known primary antiphospholipid syndrome presented with a 4-day history of chest and abdominal pain, inferior ST-segment elevation on a 12-lead ECG and a subtherapeutic international normalised ratio. In view of a significantly raised high-sensitivity troponin I assay, inferior wall hypokinesis on transthoracic echocardiography and despite unobstructed epicardial vessels on emergency coronary angiography, a diagnosis of myocardial infarction was made. Furthermore, the patient also developed both bilateral adrenal haemorrhages leading to acute adrenal insufficiency and microvascular thrombotic renal disease concurrently. The patient therefore fulfilled the diagnostic criteria for catastrophic antiphospholipid syndrome presenting with cardiac, endocrine and renal involvement. Early diagnosis permitted appropriate treatment with anticoagulation, dual antiplatelet therapy, secondary prevention and corticosteroid replacement therapy and led to a full recovery. This case highlights first the importance of adequate anticoagulation in antiphospholipid syndrome and, second, the potentially fatal, multiorgan complication of failure to do so.

Clinical outcomes of bioresorbable vascular scaffolds implanted with routine versus selective optical coherence tomography guidance: results from a single-centre experience.

AIMS: We aimed to investigate the effects of an initial learning period with mandatory optical coherence tomography (OCT) guidance for the implantation of everolimus-eluting bioresorbable vascular scaffolds (BVS). METHODS AND RESULTS: We analysed procedural and clinical outcomes of all BVS implantations at a single centre where OCT guidance was mandatory in the initial rollout (OCT-mandatory) phase. We compared these data with the later phase where use of OCT was at operator discretion (OCT-selective or angiography). We implanted 406 BVS in 306 vessels (201 OCT, 105 angiography) in 272 patients. Follow-up duration was 38±10 months. Annualised rates of device-oriented cardiac events (DOCE) and scaffold thrombosis (ScT) were 1.4% and 0.4%, respectively. The risks of DOCE (HR 1.06, 95% CI: 0.33-3.34; p=0.71) and ScT (HR 0.48, 95% CI: 0.07-3.85; p=0.49) were not significantly different when comparing the OCT and angiography groups. CONCLUSIONS: Routine use of OCT to guide and optimise BVS implants results in very acceptable outcomes. Further, the benefits of such an early OCT-mandatory "learning" period persist after cessation of routine OCT usage when imaging is not routinely used. A period of mandatory OCT usage for BVS implants may therefore be beneficial in improving patient outcomes with these devices.

Ventricular pro-arrhythmic phenotype, arrhythmic substrate, ageing and mitochondrial dysfunction in peroxisome proliferator activated receptor-γ coactivator-1ß deficient (Pgc-1ß-/-) murine hearts.

INTRODUCTION: Ageing and age-related bioenergetic conditions including obesity, diabetes mellitus and heart failure constitute clinical ventricular arrhythmic risk factors. MATERIALS AND METHODS: Pro-arrhythmic properties in electrocardiographic and intracellular recordings were compared in young and aged, peroxisome proliferator-activated receptor-γ coactivator-1ß knockout (Pgc-1ß-/-) and wild type (WT), Langendorff-perfused murine hearts, during regular and programmed stimulation (PES), comparing results by two-way ANOVA. RESULTS AND DISCUSSION: Young and aged Pgc-1ß-/- showed higher frequencies and durations of arrhythmic episodes through wider PES coupling-interval ranges than WT. Both young and old, regularly-paced, Pgc-1ß-/- hearts showed slowed maximum action potential (AP) upstrokes, (dV/dt)max (∼157 vs. 120-130 V s-1), prolonged AP latencies (by ∼20%) and shortened refractory periods (∼58 vs. 51 ms) but similar AP durations (∼50 ms at 90% recovery) compared to WT. However, Pgc-1ß-/- genotype and age each influenced extrasystolic AP latencies during PES. Young and aged WT ventricles displayed distinct, but Pgc-1ß-/- ventricles displayed similar dependences of AP latency upon (dV/dt)max resembling aged WT. They also independently increased myocardial fibrosis. AP wavelengths combining activation and recovery terms paralleled contrasting arrhythmic incidences in Pgc-1ß-/- and WT hearts. Mitochondrial dysfunction thus causes pro-arrhythmic Pgc-1ß-/- phenotypes by altering AP conduction through reducing (dV/dt)max and causing age-dependent fibrotic change.

The cardiac sympathetic co-transmitter galanin reduces acetylcholine release and vagal bradycardia: implications for neural control of cardiac excitability.

The autonomic phenotype of congestive cardiac failure is characterised by high sympathetic drive and impaired vagal tone, which are independent predictors of mortality. We hypothesize that impaired bradycardia to peripheral vagal stimulation following high-level sympathetic drive is due to sympatho-vagal crosstalk by the adrenergic co-transmitters galanin and neuropeptide-Y (NPY). Moreover we hypothesize that galanin acts similarly to NPY by reducing vagal acetylcholine release via a receptor mediated, protein kinase-dependent pathway. Prolonged right stellate ganglion stimulation (10 Hz, 2 min, in the presence of 10 µM metoprolol) in an isolated guinea pig atrial preparation with dual autonomic innervation leads to a significant (p<0.05) reduction in the magnitude of vagal bradycardia (5 Hz) maintained over the subsequent 20 min (n=6). Immunohistochemistry demonstrated the presence of galanin in a small number of tyrosine hydroxylase positive neurons from freshly dissected stellate ganglion tissue sections. Following 3 days of tissue culture however, most stellate neurons expressed galanin. Stellate stimulation caused the release of low levels of galanin and significantly higher levels of NPY into the surrounding perfusate (n=6, using ELISA). The reduction in vagal bradycardia post sympathetic stimulation was partially reversed by the galanin receptor antagonist M40 after 10 min (1 µM, n=5), and completely reversed with the NPY Y(2) receptor antagonist BIIE 0246 at all time points (1 µM, n=6). Exogenous galanin (n=6, 50-500 nM) also reduced the heart rate response to vagal stimulation but had no effect on the response to carbamylcholine that produced similar degrees of bradycardia (n=6). Galanin (500 nM) also significantly attenuated the release of (3)H-acetylcholine from isolated atria during field stimulation (5 Hz, n=5). The effect of galanin on vagal bradycardia could be abolished by the galanin receptor antagonist M40 (n=5). Importantly the GalR(1) receptor was immunofluorescently co-localised with choline acetyl-transferase containing neurons at the sinoatrial node. The protein kinase C inhibitor calphostin (100 nM, n=6) abolished the effect of galanin on vagal bradycardia whilst the protein kinase A inhibitor H89 (500 nM, n=6) had no effect. These results demonstrate that prolonged sympathetic activation releases the slowly diffusing adrenergic co-transmitter galanin in addition to NPY, and that this contributes to the attenuation in vagal bradycardia via a reduction in acetylcholine release. This effect is mediated by GalR(1) receptors on vagal neurons coupled to protein kinase C dependent signalling pathways. The role of galanin may become more important following an acute injury response where galanin expression is increased.