Activation recovery interval (ARI), extracted from unipolar electrograms, serves as a practical surrogate for repolarization during experimental studies in vivo. Far-field signal contamination and low spatial resolution obscure regional repolarization gradients and duration alernans detection using unipolar ARI. We hypothesized that the attenuation of far-field contamination with the principal component-referenced unipole will allow for a more accurate assessment of true local repolarization gradients and spatially assess action potential duration alternans.

In a previous study, on pulsed-field ablation (PFA) in the swine ventricle, we found that lesion depth was described (±1 mm accuracy) by a logarithmic function of contact force (CF) and the number of PFA pulses (PF-ablation index). This study was designed to validate prospectively whether the novel PF-ablation index would allow PFA lesions to be created at depths of 3.5, 4.5, 5.5, and 6.5 mm with high prediction accuracy in a swine-beating heart model.

Cavotricuspid isthmus (CTI) ablation is frequently performed either as a standalone procedure or in combination with pulmonary vein isolation. With the rapid adoption of pulsed field ablation for atrial fibrillation, it is essential to delineate the utility of this modality in treating CTI-dependent atrial flutter (AFL). This study aims to evaluate the procedural and clinical outcomes of CTI ablation using pulsed field energy.

Retrograde ethanolization of the vein of Marshall (VOM) has been identified as an adjunct technique in the treatment of persistent atrial fibrillation (AF) and left atrial tachycardia, as stated in the last consensus statement on ablation of AF. However, there is a lack of high-volume data on the technique.

Horses are one of the few animals that spontaneously develop atrial fibrillation (AF), making them a powerful model for studying AF mechanisms and treatment effects. Despite the initial effectiveness of treatment in horses and humans, AF-induced atrial remodeling compromises its long-term success. Observational studies have suggested that metformin may reduce the risk of AF, but its effects on progressive AF-induced atrial remodeling have yet to be evaluated in a high-fidelity large animal model.

Hemolysis is a recognized side effect of pulsed field ablation (PFA). Severe hemolysis can lead to acute kidney injury, affecting the morbidity of patients undergoing PFA for atrial fibrillation. Here, we aimed to characterize the degree of hemolysis across different PFA technologies.

Cardiac resynchronization therapy (CRT) is an important therapeutic option in selected pediatric patients and patients with congenital heart disease with reduced systemic ventricular ejection fraction (SVEF). However, the identification of optimal responders is challenging. This study aimed to identify predictors of response to CRT in children and patients with congenital heart disease at 5 large quaternary referral centers.

Long QT syndrome (LQTS) is primarily an inherited condition associated with the risk of sudden cardiac death. Due to variable phenotypic expression, a prolonged QT interval on a 12-lead ECG is not always present. LQTS may present in the fetus with persistent bradycardia, including sinus bradycardia or functional 2:1 atrioventricular block. We report our experience of persistent fetal bradycardia prompting parental assessment for congenital LQTS.

Although hyperthyroidism is known to increase the risk of atrial fibrillation (AF), subclinical hypothyroidism (SH) is an often-underreported condition characterized by elevated thyroid-stimulating hormone (TSH) levels and normal fT3/fT4 levels. This study aimed to clarify the association between SH and AF and to identify potential direct electrophysiological effects of TSH.

Multifocal ectopic Purkinje-related premature contractions syndrome presents as a rare cardiac disorder characterized by frequent multifocal ectopic ventricular beats with narrow QRS complexes, originating from various ectopic foci along the fascicular-Purkinje system. It is characterized by mutations in the gene, inducing a gain-of-function in the human cardiac voltage-gated Na channel (Na1.5), which causes an alteration in the action potentials of the cardiomyocytes. The syndrome was initially delineated in 2012 by Laurent et al in 3 Dutch families, subsequently garnering recognition through several reported cases worldwide. Clinically, it often manifests with a familial predisposition to other arrhythmogenic cardiac diseases, alongside symptoms such as palpitations and syncope. A key diagnostic hallmark is the high daily burden of multifocal premature ventricular contractions observed on 24-hour dynamic ECG, with evidence of repetitive ventricular arrhythmias. This can potentially induce a reversible form of left ventricular dilation with systolic dysfunction, known as premature ventricular contraction-induced cardiomyopathy. Diagnosis may be challenging, requiring exclusion of the most frequent causes of ventricular arrhythmias first. The disappearance of arrhythmias during a stress test and the inefficacy of catheter ablation procedures may serve as additional elements to bolster the suspicion of multifocal ectopic Purkinje-related premature contractions syndrome. Genetic testing and electrophysiological studies are pivotal in confirming the diagnosis. Therapeutic management of this syndrome primarily involves medical therapy with class I antiarrhythmic drugs, such as flecainide and quinidine, which may reduce ventricular arrhythmias and associated symptoms. In this systematic review, our aim was to provide an exhaustive insight into the genetic basis, diagnosis, and treatment strategies for this intriguing yet relatively underexplored syndrome.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, characterized by atrial fibrosis, a crucial substrate facilitating its initiation and persistence. CKAP4 (cytoskeleton-associated protein 4) has been associated with fibroblast activation; however, its involvement in atrial remodeling and AF susceptibility remains unclear.

The Lead EvaluAtion for Defibrillation and Reliability (LEADR) trial evaluated the small-diameter (4.7Fr), lumenless, integrated bipolar OmniaSecure defibrillation lead. The trial exceeded primary safety and efficacy objective thresholds, demonstrating favorable efficacy at implant and a low rate of complications. Three-year term outcomes of the LEADR trial assessing the OmniaSecure lead are reported here. The LEADR trial is a prospective, multicenter, single-arm clinical trial. Patients with an indication for de novo ICD/CRT-D were implanted with the OmniaSecure lead in standard right ventricle (RV) locations and followed at prespecified intervals. The lead was evaluated for safety, efficacy, and reliability through final follow-up. There were 643/657 patients (97.9%) successfully implanted with the OmniaSecure lead with a mean follow-up of 32.4 ± 9.1 months (26% female, 61.9 ± 12.9 years). Pacing capture threshold, pacing impedance, and R-wave amplitudes remained stable throughout. There was a 96.5% freedom from major study lead-related complications at 3 years. At 3 years, 22.3% of patients received appropriate therapies, i.e., shock and/or anti-tachycardia pacing (ATP), with a 75.4% ATP efficacy. Inappropriate shock rate was 2.7% and 5.9% at 1 and 3 years, respectively. The final results of the LEADR trial demonstrated 3-year term safety, efficacy, and reliability of the OmniaSecure lead, emphasizing the potential utility of this lead in a wide variety of patients.

MODULAR ATP (antitachycardia pacing), a multicenter, international trial, assesses a modular cardiac rhythm management system (mCRM): a subcutaneous implantable cardioverter-defibrillator (S-ICD) in wireless communication with a leadless pacemaker (LP) capable of pace-terminating ventricular tachycardia (VT). Enrolees had one or more clinical risk factors for VT and did not require chronic pacing. Complications included pre-specified major LP system- and procedure-related complications, and any complication related to the LP, S-ICD, implantation, or study protocol. Survival analysis was performed to identify complication-free rates, therapy delivery, and all-cause mortality. The 297 patients enrolled had an ejection fraction 35±13%, 43% secondary prevention indications, and 59% with prior ventricular arrhythmias (VA). Of 286 patients undergoing LP implantation (100% success), 251 patients completed 12-month follow-up. Mortality rate was 6%, with none related to the implant procedure. Median follow-up duration was 23.4 months (interquartile range: 17.9-28.1). The LP major complication-free rate was 97.2%, exceeding the performance goal. The overall LP+S-ICD system-related complication-free rate was 88.5%. Appropriate tachyarrhythmia-therapy (ATP+shock) rates were 14.4% and appropriate shock rates were 8.5%. Inappropriate total tachyarrhythmia therapy was 9.5% of which 8.5% were shocks. ATP was 67.3% successful in terminating VA episodes and accelerated VAs in 10.1% of episodes. Overall therapy burden (ATP+shock) was 96/100 patient-years of which 44/100 patient-years was for shock delivery. One-year outcomes of the first modular pacing-defibrillator system reveal low system and LP complication rates and good ATP efficacy rates suggesting that the mCRM is a viable alternative to single-chamber ICDs using low-energy pacing capability without the need for transvenous leads.