Heart failure (HF) is a prevalent cardiovascular disease with significant morbidity and mortality rates worldwide. Due to the intricate structure of the heart, diverse cell types, and the complex pathogenesis of HF, further in‐depth investigation into the underlying mechanisms is required. The elucidation of the heterogeneity of cardiomyocytes and the intercellular communication network is particularly important. Traditional high‐throughput sequencing methods provide an average measure of gene expression, failing to capture the “heterogeneity” between cells and impacting the accuracy of gene function knowledge. In contrast, single‐cell sequencing techniques allow for the amplification of the entire genome or transcriptome at the individual cell level, facilitating the examination of gene structure and expression with unparalleled precision. This approach offers valuable insights into disease mechanisms, enabling the identification of changes in cellular components and gene expressions during hypertrophy associated with HF. Moreover, it reveals distinct cell populations and their unique roles in the HF microenvironment, providing a comprehensive understanding of the cellular landscape that underpins HF pathogenesis. This review focuses on the insights provided by single‐cell sequencing techniques into the mechanisms underlying HF and discusses the challenges encountered in current cardiovascular research.

The heterogeneity of functional cardiomyocytes arises during heart development, which is essential to the complex and highly coordinated cardiac physiological function. Yet the biological and physiological identities and the origin of the specialized cardiomyocyte populations have not been fully comprehended. Here we report a previously unrecognised population of cardiomyocytes expressing Dbhgene encoding dopamine beta-hydroxylase in murine heart. We determined how these myocytes are distributed across the heart by utilising advanced single-cell and spatial transcriptomic analyses, genetic fate mapping and molecular imaging with computational reconstruction. We demonstrated that they form the key functional components of the cardiac conduction system by using optogenetic electrophysiology and conditional cardiomyocyte Dbh gene deletion models. We revealed their close relationship with sympathetic innervation during cardiac conduction system formation. Our study thus provides new insights into the development and heterogeneity of the mammalian cardiac conduction system by revealing a new cardiomyocyte population with potential catecholaminergic endocrine function.

The development of the cardiac conduction system (CCS) is essential for correct heart function. However, critical details on the cell types populating the CCS in the mammalian heart during the development remain to be resolved. Using single-cell RNA sequencing, we generated a large dataset of transcriptomes of ~0.5 million individual cells isolated from murine hearts at six successive developmental corresponding to the early, middle and late stages of heart development. The dataset provides a powerful library for studying the development of the heart’s CCS and other cardiac components. Our initial analysis identified distinct cell types between 20 to 26 cell types across different stages, of which ten are involved in forming the CCS. Our dataset allows researchers to reuse the datasets for data mining and a wide range of analyses. Collectively, our data add valuable transcriptomic resources for further study of cardiac development, such as gene expression, transcriptional regulation and functional gene activity in developing hearts, particularly the CCS.

Sodium-glucose co-transporter 2 (SGLT2) inhibitors have been shown to lower the risk of re-hospitalization and cardiovascular mortality among heart failure (HF) patients. Nevertheless, the impact of these agents on ventricular arrhythmias (VAs) has not been thoroughly investigated. To assess the beneficial impact of SGLT2 inhibitors on VAs in patients at various stages of HF, a systematic review and meta-analysis of randomized controlled trials involving SGLT2 inhibitors in this patient population was performed. A comprehensive search of the PubMed, Embase, Ovid, ProQuest, Scopus, and Cochrane databases was performed for clinical trials published up to November 21, 2024. The primary outcomes of interest were incidences of VAs and sudden cardiac death (SCD) between the groups receiving SGLT2 inhibitors and the control drugs. For the outcomes observed in the populations of the included trials and in specific subgroups, hazard ratios (HRs) and 95% confidence intervals (CIs) were pooled and meta-analysed across the analyses. A total of 23 randomized trials (22 placebo-controlled trials and 1 active-controlled trial) involving 74,380 patients (37,372 receiving SGLT2 inhibitors and 37,008 in the control group) were included. The analysed SGLT2 inhibitors included canagliflozin, dapagliflozin, empagliflozin, bexagliflozin, sotagliflozin, and ertugliflozin. The participants were non-advanced HF patients, including at-risk for HF, pre-HF, and symptomatic HF, with follow-up duration ranging from 12 to 296 weeks. Compared with the control, treatment with SGLT2 inhibitors was associated with significantly reduced risk of VAs (risk ratio (RR) 0.85, 95% confidence interval (CI) 0.74–0.98; P = 0.02) and SCD (RR 0.79, 95% CI 0.64–0.98; P = 0.03). Subgroup analyses indicated that longer follow-up (≥ 1 year) taking SGLT2 inhibitors can still reduce the risk of VAs (RR 0.79, 95% CI 0.65–0.96; P = 0.02) and SCD (RR 0.80, 95% CI 0.65–0.99; P = 0.04). SGLT2 inhibitors have beneficial effects on lowering risks of VAs and SCD in patients with type 2 diabetes, cardiovascular diseases, heart failure with reduced ejection fraction (HFrEF), heart failure with preserved ejection fraction (HFpEF), and heart failure with mildly reduced ejection fraction (HFmrEF), with longer follow-up duration reinforcing these findings. However, future prospective trials are needed to verify the effects of SGLT2 inhibitors on VAs and SCD. PROSPERO (CRD42024601914) 1. Redefine outcomes of ventricular arrhythmias (VAs) and sudden cardiac death (SCD) for SGLT2 inhibitor medication in heart failure patients. 2. SGLT2 inhibitors lower the risks of VAs and SCD in patients at various stages of HF, excluding advanced HF. 3. Longer therapeutic effects were associated with a significant reduction in the incidence of VAs and SCD.

Pathological hypertrophy underlies sudden cardiac death due to its high incidence of occurrence of ventricular arrhythmias. The alteration of transmural electrophysiological properties in hypertrophic cardiac murine tissue has never been explored previously. In this dataset, we have for the first time conducted high-throughput simultaneous optical imaging of transmembrane potential and calcium transients (CaT) throughout the entire hypertrophic murine hearts at high temporal and spatial resolution. Using ElectroMap, we have conducted multiple parameters analysis including action potential duration/calcium transient duration, conduction velocity, alternans and diastolic interval. Voltage-calcium latency was measured as time difference between action potential and CaT peak. The dataset therefore provides the first high spatial resolution transmural electrophysiological profiling of the murine heart, allowing interrogation of mechanisms driving ventricular arrhythmias associated with pathological hypertrophy. The dataset allows for further reuse and detailed analyses of geometrical, topological and functional analyses and reconstruction of 2-dimensional and 3-dimentional models.

We explored physiological effects of the sodium-glucose co-transporter-2 inhibitor empagliflozin on intact experimentally hypertrophic murine hearts following transverse aortic constriction (TAC). Postoperative drug (2–6 weeks) challenge resulted in reduced late Na⁺ currents, and increased phosphorylated (p-)CaMK-II and Nav1.5 but not total (t)-CaMK-II, and Na⁺/Ca²⁺ exchanger expression, confirming previous cardiomyocyte-level reports. It rescued TAC-induced reductions in echocardiographic ejection fraction and fractional shortening, and diastolic anterior and posterior wall thickening. Dual voltage- and Ca²⁺-optical mapping of Langendorff-perfused hearts demonstrated that empagliflozin rescued TAC-induced increases in action potential durations at 80% recovery (APD₈₀), Ca²⁺ transient peak signals and durations at 80% recovery (CaTD₈₀), times to peak Ca²⁺ (TTP₁₀₀) and Ca²⁺ decay constants (Decay_30–90) during regular 10-Hz stimulation, and Ca²⁺ transient alternans with shortening cycle length. Isoproterenol shortened APD₈₀ in sham-operated and TAC-only hearts, shortening CaTD₈₀ and Decay_30–90 but sparing TTP₁₀₀ and Ca²⁺ transient alternans in all groups. All groups showed similar APD₈₀, and TAC-only hearts showed greater CaTD₈₀, heterogeneities following isoproterenol challenge. Empagliflozin abolished or reduced ventricular tachycardia and premature ventricular contractions and associated re-entrant conduction patterns, in isoproterenol-challenged TAC-operated hearts following successive burst pacing episodes. Empagliflozin thus rescues TAC-induced ventricular hypertrophy and systolic functional, Ca²⁺ homeostatic, and pro-arrhythmogenic changes in intact hearts.