BACKGROUND: The mechanisms behind endocardial entanglement and resultant delamination during left bundle branch area pacing, as well as potential solutions, have not been fully demonstrated in the human heart. METHODS: Active fixation of a lumenless screw-in lead into the right ventricular septum was attempted with or without delivery system support using donor human hearts rejected for transplant. Delivery sheath support was ensured through firm catheter support maintained by a fixed clip. Endocardial entanglement, endocardial delamination after unscrewing, and lead penetration were evaluated using both macroscopic and microscopic analyses. RESULTS : Each of 10 lead deployments with or without support was attempted using 4 donor human hearts. There was a higher incidence of endocardial entanglement and resultant helix-only penetration in the nonsupport group than the support group (70% versus 0%). Unscrewing after the endocardial entanglement consistently revealed extensively delaminated endocardium entwined around the helix. The median endocardial delamination area was larger in the entanglement group than in the nonentanglement group (25.0 mm(2 )versus 0.9 mm(2), P<0.001). In the regions with endocardial entanglement, histological analysis confirmed extensive endocardial delamination with minimal myocardial injury. On the other hand, localized endocardial delamination and deep intramural penetration were observed in the regions without entanglement. Screw-in procedures reattempted into the regions with extensive endocardial delamination following entanglement achieved deep penetration even without delivery system support. CONCLUSIONS: Endocardial entanglement and delamination were confirmed in donor human hearts. Adequate delivery system support, particularly its coaxiality and counterforce effect, is likely to prevent endocardial entanglement and facilitate effective penetration of a lumenless screw-in lead into the human ventricular septum.

To evaluate whether “idiopathic ventricular tachycardia” remains an appropriate label in the modern era. We synthesize current literature and review sites of origin, mechanisms, and characteristic ECG signatures, and appraise contemporary diagnostic approaches capable of revealing occult substrate. Tools such as cardiac MRI with late gadolinium enhancement and electroanatomic mapping frequently reveals substrate in patients once considered “idiopathic.” 18F-FDG PET-CT can also detect active myocardial inflammation when CMR is nondiagnostic, and high-density voltage mapping may expose low-voltage scar below imaging resolution. Early genetic signals (e.g., CCR7, PKN2) suggest heritable underpinnings for some “idiopathic” presentations. A substantial fraction of “idiopathic” VT appears to reflect limitations in detection rather than true absence of disease. A pragmatic workup includes history/ECG, ischemia evaluation, CMR (LGE ± T1/T2 mapping), targeted inflammatory imaging when suspicion is high, and consideration of high-density voltage mapping in select cases. Standardized definitions incorporating modern diagnostics and long-term follow-up are needed.

Cardiac telemetry has evolved into a vital tool for continuous cardiac monitoring and early detection of cardiac abnormalities. In recent years, artificial intelligence (AI) has become increasingly integrated into cardiac telemetry, making a shift from traditional statistical machine learning models to more advanced deep neural networks. These modern AI models have demonstrated superior accuracy and the ability to detect complex patterns in telemetry data, enhancing real-time monitoring, predictive analytics and personalised cardiac care. In our review, we examine the current state of AI in cardiac telemetry, focusing on deep learning techniques, their clinical applications, the challenges and limitations faced by these models, and potential future directions in this promising field.

Atrial fibrillation (AF) is a common cardiac arrhythmia with serious health consequences if not detected and treated early. Detecting AF using wearable devices with photoplethysmography (PPG) sensors and deep neural networks has demonstrated some success using proprietary algorithms in commercial solutions. However, to improve continuous AF detection in ambulatory settings towards a population-wide screening use case, we face several challenges, one of which is the lack of large-scale labeled training data. To address this challenge, we propose to leverage AF alarms from bedside patient monitors to label concurrent PPG signals, resulting in the largest PPG-AF dataset so far (8.5 M 30-second records from 24,100 patients) and demonstrating a practical approach to build large labeled PPG datasets. Furthermore, we recognize that the AF labels thus obtained contain errors because of false AF alarms generated from imperfect built-in algorithms from bedside monitors. Dealing with label noise with unknown distribution characteristics in this case requires advanced algorithms. We, therefore, introduce and open-source a novel loss design, the cluster membership consistency (CMC) loss, to mitigate label errors. By comparing CMC with state-of-the-art methods selected from a noisy label competition, we demonstrate its superiority in handling label noise in PPG data, resilience to poor-quality signals, and computational efficiency.

AIMS:Prior case series showed promising results for cardioneuroablation in patients with vagally induced atrioventricular blocks (VAVBs). We aimed to examine the acute procedural characteristics and intermediate-term outcomes of electroanatomical-guided cardioneuroablation (EACNA) in patients with VAVB. METHODS AND RESULTS:This international multicentre retrospective registry included data collected from 20 centres. Patients presenting with symptomatic paroxysmal or persistent VAVB were included in the study. All patients underwent EACNA. Procedural success was defined by the acute reversal of atrioventricular blocks (AVBs) and complete abolition of atropine response. The primary outcome was occurrence of syncope and daytime second- or advanced-degree AVB on serial prolonged electrocardiogram monitoring during follow-up. A total of 130 patients underwent EACNA. Acute procedural success was achieved in 96.2% of the cases. During a median follow-up of 300 days (150, 496), the primary outcome occurred in 17/125 (14%) cases with acute procedural success (recurrence of AVB in 9 and new syncope in 8 cases). Operator experience and use of extracardiac vagal stimulation were similar for patients with and without primary outcomes. A history of atrial fibrillation, hypertension, and coronary artery disease was associated with a higher primary outcome occurrence. Only four patients with primary outcome required pacemaker placement during follow-up. CONCLUSION:This is the largest multicentre study demonstrating the feasibility of EACNA with encouraging intermediate-term outcomes in selected patients with VAVB. Studies investigating the effect on burden of daytime symptoms caused by the AVB are required to confirm these findings.

Introduction: Vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor (TKI) therapy has been associated with cardiotoxicity, particularly hypertension. Cardiomyopathy and ventricular arrhythmias (VA) have rarely been reported. Case Report: A 51-year-old male with metastatic sarcoma on pazopanib, a VEGFR-TKI, for the past 4 years presented with 1 month of increasing palpitations and lightheadedness leading to a fall. On arrival, telemetry showed paroxysmal AF with RVR rates to 120 bpm followed by incessant runs of NSVT with rates 200-240 bpm. Initial labs included BNP 191 pg/mL and HS troponin-I 6 ng/L (<5 ng/L). Lidocaine infusion, amiodarone infusion, and metoprolol were required to reduce NSVT burden. Initial TTE revealed LVEF of 30-35% from baseline 55-60%. Coronary angiography showed no significant CAD. Cardiac MRI was negative for LGE or metastatic involvement. Cardiac PET-CT revealed moderate diffuse FDG uptake with focal enhancement suggestive of an inflammatory process. Pazopanib was stopped and the patient started on GDMT and prednisone taper for treatment of myocarditis. At 2 months follow up, TTE revealed LVEF improved to 45-50% and ambulatory rhythm monitoring showed rare PVCs and few NSVT episodes. Repeat cardiac PET-CT revealed resolution of myocardial inflammation. Due to sarcoma progression, the patient started on regorafenib, another VEGFR-TKI, 3 months after initial hospitalization. About 3 weeks later, he presented with frequent NSVT which required lidocaine and amiodarone infusions for arrhythmia control. Repeat cardiac PET demonstrated myocarditis recurrence. He received intravenous pulse dose steroids followed by prednisone taper and was transitioned to oral mexiletine and amiodarone with resolution of VA. Review of ambulatory rhythm monitoring 1 week following regorafenib initiation already showed 20.6% burden of ventricular ectopy and >8000 NSVT episodes. Discussion: This patient had an unusual, delayed presentation of VEGFR-TKI induced myocarditis presenting with significant VA. Although TKI induced myocarditis is rare and the mechanism is not well understood, recurrence of myocarditis in this case with an alternative agent indicates a possible medication-class effect.

Anomalous left coronary artery to pulmonary artery (ALCAPA) is a leading cause of pediatric myocardial ischemia. This paper presents a case of a young man presenting with ventricular tachycardia storm 18 years after ALCAPA repair. Clinicians should recognize the risk of ventricular tachycardia in this patient population.

Background: Cervical vagus nerve activation has been shown to have significant cardiac hemodynamic and electrophysiological effects. Transcutaneous vagal nerve stimulation (tVNS) has been reported to benefit patients with atrial fibrillation, though the potential electrophysiological effects of tVNS beyond the atrium remain unclear. Aims: The purpose of this study was to evaluate the electrophysiological effects of tVNS in patients with structurally normal hearts. Methods: Patients with structurally normal hearts undergoing electrophysiology study for supraventricular tachycardia were recruited and randomized to low-level stimulation of the right or left tragus (1 mA below discomfort threshold personalized for each patient pre-procedure, 20 Hz, 250 µs). After completion of ablation, hemodynamic and electrophysiologic parameters were measured before, during 30 min of tVNS, and at approximately 15 min after tVNS had ended. Variables were compared using one-way ANOVA, and if significant, paired comparisons were performed using the paired Student’s t-test. Results: Eighteen patients were randomized and 16 (mean age 47.0±16.1 years; 50% female) underwent the full protocol (9 right and 7 left). TVNS reduced systolic blood pressure (SBP) and was associated with significant increases in RR interval, atrial and atrioventricular nodal refractory periods (AVNERP), atrio-His (AH) interval, atrioventricular nodal Wenckebach cycle length (AVWBCL), and ventriculoatrial block cycle (VABCL) length (figure). There were no significant differences in sinus node recovery time (SNRT), His-ventricular (HV) interval, and ventricular refractory periods (VERP); 15 min post-tVNS, significant differences were still observed in SBP, RR interval, AERP, and AVWBCL, suggesting neural memory, though the effects on AVNERP and VABCL had diminished. Conclusions: TVNS is associated with measurable increases in the conduction time of the AV node and AV nodal and atrial, but not ventricular, refractory periods. Increases in AERP and AV nodal effects may explain the benefit of tVNS observed in atrial fibrillation and may potentially be leveraged to slow or terminate AV nodal dependent supraventricular tachycardias.

Catheter-based neuromodulation of intrinsic cardiac autonomic nervous system is increasingly being used to improve outcomes in patients with vasovagal syncope and bradyarrhythmias caused by vagal overactivity. However, there is still no consensus for patient selection, technical steps, and procedural end points. This review takes the reader on a practical exploration of neuromodulation for bradyarrhythmias, concentrating on the critical aspects of proper patient selection, evidence-based insights, and anatomic intricacies within the intrinsic cardiac autonomic nervous system. Also discussed are different mapping techniques and outcome measures. Future directions to optimize the utilization of this technique in clinical practice are highlighted.