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Background: Pacemaker-dependent patients with device infection require temporary pacing while the infection is treated. External transthoracic pacing is painful and variably effective, while temporary pacing leads are susceptible to superinfection.Objective: To create a biological pacemaker delivered via venous catheters in a porcine model of complete heart block, providing a temporary alternative/adjunct to external pacing devices without additional indwelling hardware.Methods: Complete atrioventricular (AV) nodal block was induced in pigs by radiofrequency ablation after the implantation of a single-chamber electronic pacemaker to maintain a ventricular backup rate of 50 beats/min. An adenoviral vector cocktail (K(AAA) + H2), expressing dominant-negative inward rectifier potassium channel (Kir2.1AAA) and hyperpolarization-activated cation channel (HCN2) genes, was injected into the AV junctional region via a NOGA Myostar catheter advanced through the femoral vein.Results: Animals injected with K(AAA) + H2 maintained a physiologically relevant ventricular rate of 93.5 ± 7 beats/min (n = 4) compared with control animals (average rate, 59.4 ± 4 beats/min; n = 6 at day 7 postinjection; P <.05). Backup electronic pacemaker utilization decreased by almost 4-fold in the K(AAA) + H2 group compared with the control (P <.05), an effect maintained for the entire 14-day window. In contrast to the efficacy of gene delivery into the AV junctional region, open-chest, direct injection of K(AAA) + H2 (or its individual vectors) into the ventricular myocardium failed to elicit significant pacemaker activity.Conclusions: The right-sided delivery of K(AAA) + H2 to the AV junctional region provided physiologically relevant biological pacing over a 14-day period. Our approach may provide temporary, bridge-to-device pacing for the effective clearance of infection prior to the reimplantation of a definitive electronic pacemaker. [ABSTRACT FROM AUTHOR]

Background: Late potential (LP) elimination has been proposed as a surrogate endpoint for scar-related ventricular tachycardia (VT) ablation procedures. The characteristics, distribution, and predictors of persistent late potentials (pLPs) after ablation have not been studied., Objective: The purpose of this study was to characterize the spatial distribution and features of pLP after catheter ablation of VT substrate with high-resolution mapping., Methods: Cases of scar-related VT ablation with adequate pre- and postablation electroanatomic maps (EAMs) acquired exclusively using a high-density grid catheter were reviewed from 2021 to 2023., Results: A total of 62 EAMs (pre- and postablation) from 31 cases using a high-density grid catheter were reviewed. pLPs were observed in 19 cases (61%) after ablation. New LP, spatially distinct from preablation LP, at the periphery of the ablation area comprised the majority of pLPs (16/19 [84%]). Isolated pLPs were more prevalent than fractionated pLPs, with a median amplitude of 0.26 mV (0.09-0.59 mV). The presence of pLP was associated with a significantly lower left ventricular ejection fraction (LVEF) and septal ablation but not low voltage, LP, or ablation area compared to absence of pLP (22.8% ± 7.8% vs 31.5% ± 8.0%, P = .008 for LVEF; 83% vs 44%, P = .033 for septal ablation)., Conclusion: Formation of spatially distinct new LP after targeted VT ablation is common, especially in patients with lower LVEF and septal substrate independent of ablation burden. This finding highlights the limitations of complete LP elimination as an endpoint to VT ablation procedures., Competing Interests: Disclosures Shreel Joshi is an employee of Abbott Laboratories, manufacturer of the mapping system and catheters used in this study. All other authors have no conflicts to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The interaction of the pulmonary vein (PV) and putative nonpulmonary triggers of atrial fibrillation (AF) remains unclear and has yet to translate into patient-tailored ablation strategies., Objective: The purpose of this study was to use noncontact mapping to detail the global conduction patterns in paroxysmal and persistent AF and how they are modified during PV ablation., Methods: Forty patients during AF ablation underwent mapping using a noncontact catheter (AcQMap, Acutus Medical, Inc., Carlsbad, CA) before and after PV isolation (PVI). Propagation history maps were analyzed postprocedure for each patient to categorize conduction patterns into focal, organized reentrant, and disorganized patterns (F-Patterns, O-Patterns, and D-Patterns, respectively)., Results: Activation patterns identified by using a noncontact mapping system can be subclassified from 3 main patterns into subtypes (macroreentrant and localized reentrant [MR and LR] subtypes and disorganized 1 and disorganized 2 [D1 and D2] subtypes). Persistent AF demonstrated more D-Patterns and less O-Patterns and F-Patterns than did paroxysmal AF. In addition, patients with PAF inducible after PVI demonstrated a higher region number and higher prevalence of MR subtypes than did those noninducible. PVs remained the critical region and included almost one-third of all patterns across any AF types. PVI was effective to eliminate PV-related functional phenotypes and affected recurrence with other patterns., Conclusion: Activation patterns identified using AcQMap can be classified into 3 main patterns (F-Patterns, O-Patterns, and D-Patterns) as well as subtypes (MR and LR subtypes and D1 and D2 subtypes). PerAF was different from PAF in demonstrating a higher region number and higher prevalence of D-Patterns but a lower region number and lower prevalence of O-Patterns and F-Patterns., (Copyright © 2022 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: There remains some confusion delineating the accurate location and the detailed anatomical relationship between atrioventricular accessory pathways (APs) located in the superoparaseptal region., Objective: The purpose of this article was to detail the anatomical relationship and accurate location of APs located in the superoparaseptal region., Methods: Between May 1, 2009 and November 30, 2016, 11 patients with superoparaseptal APs (SPS-APs) were identified in 129 consecutive patients who underwent catheter ablation for APs in our center., Results: A single SPS-AP was detected in all patients (manifest, n = 5; concealed, n = 6). The location of all 11 APs were precisely identified at the region millimeters superior to the His bundle recording site at the tricuspid annulus (S-HB, n = 6; manifest, n = 4); the area millimeters behind the His bundle recording site, adjacent to the right atrial aspect of the noncoronary aortic cusp (B-HB, n = 2; manifest, n = 1); and the true para-His bundle region (P-HB, n = 3). The electrocardiogram of all 5 manifest APs conformed to the typical "anteroseptal AP" pattern: a positive delta wave in leads I, II, avF, and avL; a narrow positive delta wave in lead V 1 ; and a precordial QRS transition at lead V 3 . All APs were successfully eliminated by catheter ablation. After 54 ± 26 months of follow-up, all patients were free of arrhythmia., Conclusion: Three distinct regions are identified for localization of SPS-APs. Careful mapping and a detailed understanding of the anatomy of this region as well as distinct electrocardiographic characteristics are essential to eliminate such APs safely and effectively., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: In patients with idiopathic left ventricular tachycardia (ILVT), the arrhythmogenic substrate is poorly understood., Objective: The purpose of this study was to elucidate the ILVT characteristics and outcome of radiofrequency catheter ablation in patients with ILVT., Methods: Twenty-four patients with ILVT and 15 patients with left accessory pathways (control) underwent high-density mapping of the left His-Purkinje system during sinus rhythm (SR) using 3-dimensional electroanatomic mapping., Results: Fragmented antegrade Purkinje potential (FAP) was represented at the left ventricular septum slightly inferoposterior to the left posterior fascicle (LPF) in 23 patients with ILVT. In control subjects, no FAPs could be recorded at the same region, FAPs were identified at the proximal portion of the LPF (4 patients) and at the distal LPF (1 patient). The finding of any FAPs in ILVT patients was significantly higher than that in control patients (23/24 vs 5/15, P < .01). Radiofrequency ablation at the area of FAP resulted in successful ablation in 23 patients with ILVT. No ILVT recurred during follow-up of 16.3 ± 7.2 months., Conclusion: In patients with ILVT, FAP located at the left ventricular septum slightly inferoposterior to the LPF is a novel finding using 3-dimensional electroanatomic mapping. The FAP may represent an arrhythmogenic substrate in ILVT and may be used for guiding successful ablation., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: There are well-described ablation strategies to treat left fascicular tachyarrhythmia (LFTA); however, a method to predict the origin is less well characterized., Objective: The purpose of this study was to predict the origin of LFTAs by measuring the HV interval during normal sinus rhythm (NSR) and LFTAs., Methods: A predicted value of the earliest presystolic potential (PP) time was calculated using the HV interval during NSR and LFTAs [(HVNSR+HVLFTA)/2]. The earliest retrograde PP was mapped during LFTAs, and the relationship between the predicted and the mapped value was correlated., Results: Twenty-one consecutive patients with LFTAs were included in this study. Four patients (19%) had tachycardia originating from the left anterior fascicle; the mean HV interval was 50.3 ± 8.3 and 30.3 ± 11.6 ms during NSR and tachycardia, respectively. The mapped retrograde PP during LFTAs preceded the onset of the surface electrocardiogram by 34 ± 9.4 ms. Seventeen patients (81%) had tachycardia originating from the left posterior fascicle; the mean HV interval was 49.2 ± 4.6 and -4.5 ± 13.6 ms during NSR and LFTAs, respectively. Nineteen patients with successful ablation were analyzed; the mean HV interval was -0.9 ± 16.8 and 49.5 ± 4.6 ms during LFTAs and NSR, respectively. The predicted value was similar to the mapped value (24.4 ± 9.1 ms vs 25.2 ± 8.1 ms; P = .76). The predicted value was well correlated with that from the target site (r = 0.97; P < .001)., Conclusion: The earliest retrograde PP site for the ablation of LFTAs can be predicted measuring the HV interval during NSR and LFTAs. Successful ablation can be performed during NSR for patients with LFTAs inducible at baseline but noninducible during mapping., (Copyright © 2016. Published by Elsevier Inc.)

Background: Implantable cardioverter-defibrillator (ICD) lead failure is one of the major causes of inappropriate shocks. Algorithms have been developed by manufacturers to identify ICD lead failure and avoid inappropriate shocks. The SecureSense RV Lead Noise Discrimination (St Jude Medical, St Paul, MN) algorithm is designed to differentiate oversensing due to lead failure from ventricular arrhythmias and withhold inappropriate therapies. Several non-lead failure-related issues can trigger the SecureSense automated algorithm., Objective: Our objective was to explain the SecureSense algorithm in a detailed fashion, highlighting examples of SecureSense alerts triggered by non-lead failure-related issues., Methods: This is a nonrandomized observational case series. SecureSense-triggered alerts from 3 ICD device clinics were analyzed, and representative examples of SecureSense triggers due to non-lead failure-related issues were chosen to explain the function and malfunction of this algorithm., Results: The series includes 8 cases of SecureSense alerts triggered by non-lead failure-related issues---myopotential oversensing (1), P-wave oversensing (1), T-wave oversensing (1), loss of capture (1), R-wave undersensing (1), timing cycle issues (2), and cross talk (1)---and 1 case of failure of the algorithm to appropriately identify lead failure and prevent ICD shocks., Conclusion: Lead failure detection algorithms such as the one assessed in this study have an inherent risk of false-positive and false-negative detections. The latter might have fatal consequences. The true accuracy of these algorithms needs to be evaluated in large-scale real-life prospective clinical studies., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: While inducibility of atrial fibrillation (AF) is often used as an endpoint for radiofrequency ablation of AF, little is known regarding inducibility among normals. We therefore evaluated the inducibility of AF with rapid atrial pacing in patients without a clinical history of AF after catheter ablation of supraventricular tachycardia (SVT)., Methods: We prospectively evaluated 86 patients with no history of AF who were referred for catheter ablation of SVT. After successful ablation, two different rapid atrial pacing protocols for induction of AF were tested. First, AF induction was attempted by 5-second bursts of atrial pacing from the coronary sinus ostium (CSO) at three different cycle lengths (CLs). Next, decremental pacing was performed from the CSO starting at a CL of 250 ms to the loss of 1:1 atrial capture. This protocol was repeated 3 times for each subject., Results: Three of the subjects (3.5%) enrolled had inducible AF with the first pacing protocol. However, with the second protocol, AF was inducible in 22 patients (25.6%), including sustained AF in 16 patients (18.6%). There were significant differences in the inducibility of AF between the two atrial pacing protocols. Additionally, with the second pacing protocol, patients with a loss of 1:1 atrial capture at CL <180 ms were more easily inducible for AF (21/63 vs. 1/23; P = .006)., Conclusion: Using a specific, decremental pacing protocol, 26% of patients without a history of AF had inducible AF. These findings suggest that significant further investigation is needed to optimize the specificity of using AF induction as an endpoint for AF ablation., (Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)