Cardiac regenerative therapies seek to replace damaged tissue following myocardial infarction to prevent heart failure. Human pluripotent stem-cell derived cardiomyocyte (hPSC-CM) injection can be used to remuscularize the heart and improve function but also cause ventricular tachycardia (VT). Electrical mapping studies suggest this VT is focal (i.e., driven by spontaneous excitations), but true mechanisms remain unknown. Computational approaches can provide new insights into these arrhythmias, but current simulation frameworks have not replicated focal VT. In this study, we conducted simulations with biophysically plausible representations of cell injection and the formation of gap junctions between hPSC-CM grafts and host tissue. We examined hPSC-CM ionic models with slow (1.1 Hz) and accelerated (2.5, 4 Hz) beating rates and assessed if these conditions could produce focal VT that is adequately rapid and robust to overpower sinus rhythm. For simulations conducted in human ventricular slice geometries with non-human primate graft patterns, we assessed susceptibility to focal VT. For the slow ionic model, focal VT was seen only at bradycardic heart rates (40 bpm); at faster heart rates (60 or 80 bpm), ectopic activity from the graft could not out-compete Purkinje-like endocardial excitations. In contrast, focal VT was seen for all tested heart rates when faster ionic models were used. Doubling graft size to cover larger infarct areas increased focal VT susceptibility in all cases. Thus, we conclude that post-injection increase in hPSC-CM spontaneous beating rate is a potential mechanism for focal VT, with applications in safer cell injection methods following experimental validation.

Introduction: Palpitations are one of the most common cardiovascular complaints, affecting approximately 6% to 11% of the general population. Since palpitations often occur sporadically and resolve before medical evaluation, diagnosing the underlying rhythm disturbance requires documentation via an electrocardiogram (ECG) recorded during the symptomatic episode. The standard tool for this purpose has long been the 24-h Holter monitor, which has significant limitations, with diagnostic yields as low as 10% to 15%. Objective: This study aims to evaluate the feasibility and diagnostic yield of single-lead ECG recordings from smartwatches in patients presenting with palpitations. Methods: From 1 May 2023 to 1 May 2025, we conducted a prospective, real-world cohort study among consecutive adults referred to the University Hospital of Ferrara-based arrhythmia outpatient clinics for evaluation of palpitations. Eligibility required patients to be ≥21 years of age, report palpitations for which ambulatory documentation was clinically indicated, and already own a compatible smartwatch capable of single-lead ECG. Participants were trained to record a 30-s single-lead ECG at the onset of symptoms. Tracings were transmitted securely and independently reviewed by two blinded electrophysiologists. Results: Fifty-nine patients were enrolled (mean age 52 years, 64% male). Thirty-one patients (52%) transmitted at least one smartwatch-derived electrocardiographic tracing. Seventy-seven smartwatch tracings were received. Of these, 73 (95%) were interpretable; 57 (78%) showed an arrhythmia, whereas 16 (22%) demonstrated normal sinus rhythm. Four recordings (5%) were non-interpretable. From the 57 arrhythmic tracings, 44 distinct arrhythmic diagnoses were identified. Paroxysmal atrial fibrillation (AF) accounted for 16 episodes. Other diagnosed arrhythmias included atrial flutter (n = 6), paroxysmal supraventricular tachycardia (PSVT) (n = 4), premature atrial complexes (PAC) (n = 6), premature ventricular complexes (PVC) (n = 9), inappropriate sinus tachycardia (n = 12), and second-degree atrioventricular (AV) block type I (n = 4). Conclusions: Smartwatch-based ECG monitoring in symptomatic patients is feasible and provides a high diagnostic yield for a broad spectrum of arrhythmias. Unlike large-scale population screening approaches, which generate vast datasets with limited clinical benefit, a symptom-driven strategy applied to carefully selected, educated, and motivated patients proves both clinically valuable and organizationally sustainable. Indeed, the mean number of tracings transmitted per patient was low (1.3), confirming the clinical and operational sustainability of this patient-triggered, real-world approach.

Background/Objectives: Transcatheter ablation assisted by three-dimensional (3D) electroanatomical mapping (EAM) is the elective treatment for atrioventricular nodal reentrant tachycardia (AVNRT) in children and adolescents. In this population of patients, the most frequently employed EAM strategies are the low-voltage bridge (LVB) strategy and sinus rhythm propagation mapping (SRPM). However, the exact pathophysiology and anatomy of the AVNRT reentrant circuits are still poorly understood. The aim of this study was to investigate the relationship between SRPM and LVB and to shed light on nodal physiology in children and adolescents affected by AVNRT. Methods: We retrospectively collected data on pediatric patients who underwent cryoablation for AVNRT assisted by high-density 3D EAM by using the LVB strategy; maps were reviewed by two independent electrophysiologists and the SRPM was described. SRPM was defined as typical when only one collision area was identified and atypical whenever either no or ≥ two collision areas were localized. Results: Twenty-eight consecutive patients (11.3 ± 3.3 years) were enrolled. All procedures were acutely successful. Overall, atypical SRPM was present in 10 patients (35.7%), and it did not correlate with the presence of multiple SPs or electrophysiological data. Moreover, we observed an imperfect concordance between SRPM and LVB (only in 10/18 patients). When SRPM and LVB were assessed in different locations, the LVB identified the effective cryoablation site in more cases than SRPM (4/8 vs. 1/8). Lastly, in cases of double collision, one collision area co-localized with the LVB and the effective cryoablation spot, whereas the other was located superiorly, closer to the His bundle. Conclusions: Atypical sinus rhythm propagation in the Koch's triangle is a frequent finding in pediatric AVNRT patients. In this series, LVB showed closer concordance with the successful cryolesion site than retrospectively reconstructed SRPM.

Etripamil (CARDAMYST[TM]) is an intranasal L-type calcium channel blocker (CCB) developed by Milestone Pharmaceuticals for the treatment of symptomatic paroxysmal supraventricular tachycardia (PSVT) and is under investigation for atrial fibrillation with rapid ventricular rate (AF-RVR). It received its first approval on the 12 December 2025 in the USA for the conversion of acute symptomatic PSVT episodes to sinus rhythm in adults. Additional global regulatory filings of etripamil for PSVT in adults, a phase II trial of etripamil in pediatrics, and a phase III trial for AF-RVR are in progress. This article summarizes the milestones in the development of etripamil leading to this first approval for PSVT.

Eosinophilic myocarditis can result from drug hypersensitivity or various systemic disorders. Although corticosteroids are effective, treatment strategies are not standardized.

Sustained ventricular arrhythmias (VAs) in horses can require medical intervention. Prompt pharmacological treatment is indicated when the arrhythmia leads to hemodynamic or electrical instability. Established antiarrhythmic treatment of VA in horses includes lidocaine and magnesium, administered parenterally. Other antiarrhythmic agents are used; however, concerns regarding adverse effects, financial restrictions, logistics of administration, and lack of access often limit their use. While anecdotal reports of oral administration of sotalol for treatment of VA in horses exist, sotalol has primarily been described for prevention of recurrent atrial fibrillation or suppression of supraventricular and ventricular ectopy. This case series describes 4 horses with sustained VA treated orally with sotalol. Successful conversion to a predominantly normal sinus rhythm or pre-existing atrial fibrillation was achieved without any adverse effects. Sotalol could be considered as a treatment option in selected, hemodynamically stable cases of VA, especially where other established treatment options are unavailable, ineffective, or unaffordable.