Optimized isochronal late activation methods in the visualization and isthmus identification of ventricular tachycardia.

BACKGROUND: Catheter ablation of ventricular tachycardia (VT) during sinus rhythm often relies on isochronal late activation mapping (ILAM), a validated means of isthmus identification, whereby points are binned by local activation time (LAT) into 8 isochrones, and isthmus regions are identified as regions with isochronal crowding. The resulting output, however, is inherently discretized, and loss of LAT data occurs. To improve the precision of isthmus identification, we quantify isochronal density and assess the effect of increasing the number of isochrones used and the effectiveness of continuous metrics analogous to ILAM. OBJECTIVE: The objective of this study was to determine whether current practices in ILAM calculation are optimized for isthmus detection. METHODS: Patients undergoing VT ablation were included if high-density maps in both VT and sinus or paced rhythms were available. Isochronal density was assessed at differing numbers of isochrones, and isthmus discrimination was assessed. Continuous metrics that mimicked ILAM by assessing the local distribution of LAT values-using interquartile range or the median absolute deviation-were also defined and assessed. RESULTS: Eight electroanatomic maps (EAMs) were included. Isthmus discrimination improved progressively from a minimum area under the curve (AUC) of 0.600 when assessing the isochronal density of 8-isochrone EAMs to a maximum of 0.776 when assessing the density of 1000-isochrone EAMs (DeLong test, P < .0001). On logistic regression, the continuous metrics using interquartile range (AUC = 0.714) and median absolute deviation (AUC = 0.721) better discriminated isthmus identity than ILAM. CONCLUSION: Using more isochrones or using continuous ILAM analogues improves isthmus identification. By retaining more data, these metrics could increase the precision of VT ablation.

Periprocedural Management and Multidisciplinary Care Pathways for Patients With Cardiac Implantable Electronic Devices: A Scientific Statement From the American Heart Association.

The rapid technological advancements in cardiac implantable electronic devices such as pacemakers, implantable cardioverter defibrillators, and loop recorders, coupled with a rise in the number of patients with these devices, necessitate an updated clinical framework for periprocedural management. The introduction of leadless pacemakers, subcutaneous and extravascular defibrillators, and novel device communication protocols underscores the imperative for clinical updates. This scientific statement provides an inclusive framework for the periprocedural management of patients with these devices, encompassing the planning phase, procedure, and subsequent care coordinated with the primary device managing clinic. Expert contributions from anesthesiologists, cardiac electrophysiologists, and cardiac nurses are consolidated to appraise current evidence, offer patient and health system management strategies, and highlight key areas for future research. The statement, pertinent to a wide range of health care professionals, underscores the importance of quality care pathways for patient safety, optimal device function, and minimization of hemodynamic disturbances or arrhythmias during procedures. Our primary objective is to deliver quality care to the expanding patient cohort with cardiac implanted electronic devices, offering direction in the era of evolving technologies and laying a foundation for sustained education and practice enhancement.

Determinants of global cardiac implantable electrical device remote monitoring utilization - Results from an international survey.

Background: Despite near-global availability of remote monitoring (RM) in patients with cardiac implantable electronic devices (CIED), there is a high geographical variability in the uptake and use of RM. The underlying reasons for this geographic disparity remain largely unknown. Objectives: To study the determinants of worldwide RM utilization and identify locoregional barriers of RM uptake. Methods: An international survey was administered to all CIED clinic personnel using the Heart Rhythm Society global network collecting demographic information, as well as information on the use of RM, the organization of the CIED clinic, and details on local reimbursement and clinic funding. The most complete response from each center was included in the current analysis. Stepwise forward multivariate linear regression was performed to identify determinants of the percentage of patients with a CIED on RM. Results: A total of 302 responses from 47 different countries were included, 61.3% by physicians and 62.3% from hospital-based CIED clinics. The median percentage of CIED patients on RM was 80% (interquartile range, 40-90). Predictors of RM use were gross national income per capita (0.76% per US$1000, 95% CI 0.72-1.00, P < .001), office-based clinics (7.48%, 95% CI 1.53-13.44, P = .014), and presence of clinic funding (per-patient payment model 7.90% [95% CI 0.63-15.17, P = .033); global budget 3.56% (95% CI -6.14 to 13.25, P = .471]). Conclusion: The high variability in RM utilization can partly be explained by economic and structural barriers that may warrant specific efforts by all stakeholders to increase RM utilization.

Quantitative 3D electron microscopy characterization of mitochondrial structure, mitophagy, and organelle interactions in murine atrial fibrillation.

Atrial fibrillation (AF) is the most common clinical arrhythmia, however there is limited understanding of its pathophysiology including the cellular and ultrastructural changes rendered by the irregular rhythm, which limits pharmacological therapy development. Prior work has demonstrated the importance of reactive oxygen species (ROS) and mitochondrial dysfunction in the development of AF. Mitochondrial structure, interactions with other organelles such as sarcoplasmic reticulum (SR) and T-tubules (TT), and degradation of dysfunctional mitochondria via mitophagy are important processes to understand ultrastructural changes due to AF. However, most analysis of mitochondrial structure and interactome in AF has been limited to two-dimensional (2D) modalities such as transmission electron microscopy (EM), which does not fully visualize the morphological evolution of the mitochondria during mitophagy. Herein, we utilize focused ion beam-scanning electron microscopy (FIB-SEM) and perform reconstruction of three-dimensional (3D) EM from murine left atrial samples and measure the interactions of mitochondria with SR and TT. We developed a novel 3D quantitative analysis of FIB-SEM in a murine model of AF to quantify mitophagy stage, mitophagosome size in cardiomyocytes, and mitochondrial structural remodeling when compared with control mice. We show that in our murine model of spontaneous and continuous AF due to persistent late sodium current, left atrial cardiomyocytes have heterogenous mitochondria, with a significant number which are enlarged with increased elongation and structural complexity. Mitophagosomes in AF cardiomyocytes are located at Z-lines where they neighbor large, elongated mitochondria. Mitochondria in AF cardiomyocytes show increased organelle interaction, with 5X greater contact area with SR and are 4X as likely to interact with TT when compared to control. We show that mitophagy in AF cardiomyocytes involves 2.5X larger mitophagosomes that carry increased organelle contents. In conclusion, when oxidative stress overcomes compensatory mechanisms, mitophagy in AF faces a challenge of degrading bulky complex mitochondria, which may result in increased SR and TT contacts, perhaps allowing for mitochondrial Ca2+ maintenance and antioxidant production.

Automated prediction of isthmus areas in scar-related atrial tachycardias using artificial intelligence.

INTRODUCTION: Ablation of scar-related reentrant atrial tachycardia (SRRAT) involves identification and ablation of a critical isthmus. A graph convolutional network (GCN) is a machine learning structure that is well-suited to analyze the irregularly-structured data obtained in mapping procedures and may be used to identify potential isthmuses. METHODS: Electroanatomic maps from 29 SRRATs were collected, and custom electrogram features assessing key tissue and wavefront properties were calculated for each point. Isthmuses were labeled off-line. Training data was used to determine the optimal GCN parameters and train the final model. Putative isthmus points were predicted in the training and test populations and grouped into proposed isthmus areas based on density and distance thresholds. The primary outcome was the distance between the centroids of the true and closest proposed isthmus areas. RESULTS: A total of 193 821 points were collected. Thirty isthmuses were detected in 29 tachycardias among 25 patients (median age 65.0, 5 women). The median (IQR) distance between true and the closest proposed isthmus area centroids was 8.2 (3.5, 14.4) mm in the training and 7.3 (2.8, 16.1) mm in the test group. The mean overlap in areas, measured by the Dice coefficient, was 11.5 ± 3.2% in the training group and 13.9 ± 4.6% in the test group. CONCLUSION: A GCN can be trained to identify isthmus areas in SRRATs and may help identify critical ablation targets.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation.

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society (HRS), the Asia Pacific HRS, and the Latin American HRS.