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Background: Mechanisms of scar-related ventricular tachycardia (VT) are largely based on computational and animal models that portray a 2-dimensional view.Objectives: The authors sought to delineate the human VT circuit with a 3-dimensional perspective from recordings obtained by simultaneous endocardial and epicardial mapping.Methods: High-resolution mapping was performed during 97 procedures in 89 patients with structural heart disease. Circuits were characterized by systematic isochronal analysis to estimate the dimensions of the isthmus and extent of the exit region recorded on both myocardial surfaces.Results: A total of 151 VT morphologies were mapped, of which 83 underwent simultaneous endocardial and epicardial mapping; 17% of circuits activated in a 2-dimensional plane, restricted to 1 myocardial surface. Three-dimensional activation patterns with nonuniform transmural propagation were observed in 61% of circuits with only 4% showing transmurally uniform activation, and 18% exhibiting focal activation patterns consistent with mid-myocardial reentry. The dimensions of the central isthmus were 17 mm (12 to 28 mm) × 10 mm (9 to 19 mm) with 55% exhibiting a minimal dimension of <1.5 cm. QRS activation was transmural in 63% and located 43 mm (34 to 52 mm) from the central isthmus. On the basis of 6 proposed definitions for epicardial VT, the prevalence of an epicardial circuit ranged from 21% to 80% in ischemic cardiomyopathy and 28% to 77% in nonischemic cardiomyopathy.Conclusions: A 2D perspective oversimplifies the electrophysiological circuit responsible for reentrant human VT and simultaneous endocardial and epicardial mapping facilitates inferences about mid-myocardial activation. Intricate activation patterns are frequently observed on both myocardial surfaces, and the epicardium is functionally involved in the majority of circuits. Human reentry may exist within isthmus dimensions smaller than 1 cm, whereas QRS activation is often transmural and remote from the critical isthmus target. A 3-dimensional perspective of the VT circuit may enhance the precision of ablative therapy and may support a greater role for adjunctive strategies and technology to address arrhythmogenic tissue harbored in the mid-myocardium and subepicardium. [ABSTRACT FROM AUTHOR]

Introduction: Ventricular arrhythmias (VA) after left ventricular assist device (LVAD) placement are associated with increased morbidity and mortality. We sought to assess epicardial voltage characteristics at the time of LVAD implantation and investigate relationships between scar burden and postimplant VA. Methods and Results: Consecutive patients underwent open chest epicardial electroanatomic mapping immediately before LVAD implantation. Areas of low voltage and sites with local abnormal potentials were identified. Patients were followed prospectively for postimplant VA and clinical outcomes. Between 2015 and 2017, 36 patients underwent high‐density intraoperative epicardial voltage mapping; 15 had complete maps suitable for analysis. Mapping required a median of 11.8 (interquartile range [IQR], 8.5‐12.7) minutes, with a median of 2650 (IQR, 2139‐3191) points sampled per patient. Over a median follow‐up of 311 (IQR, 168‐469) postoperative days, four patients (27%) experienced sustained VA. Patients with postimplant VA were more likely to have had preimplant implantable cardioverter defibrillator shocks (100% vs 27%; P = 0.03), ventricular tachycardia storm (75% vs 9%; P = 0.03), and lower ejection fraction (13.5 vs 19.0%, P = 0.05). Patients with postimplant VA also had a significantly higher burden of epicardial low bipolar voltage points: 55.4% vs 24.9% of points were less than 0.5 mV (P = 0.01), and 88.9% vs 63.7% of points less than 1.5 mV (P = 0.004). Conclusions: Intraoperative high‐density epicardial mapping during LVAD implantation is safe and efficient, facilitating characterization of a potentially arrhythmogenic substrate. An increased burden of the epicardial scar may be associated with a higher incidence of postimplant VA. The role of empiric intraoperative epicardial ablation to mitigate risk of postimplant VA requires further study. [ABSTRACT FROM AUTHOR]

Background: In recent years, there has been a dedicated focus to improve the tools, techniques, and technology for radiofrequency ablation (RFA) of atrial fibrillation (AF). Multi-electrode catheters paired with software enhancements for visualization and electrogram analysis have paved the way for more efficient mapping and anatomically accurate renderings of cardiac chambers. Contact force sensing catheters have been shown to be safe and effective tools for RFA, and software features have allowed for more accurate predictability of durable lesions. These factors combined can dramatically improve procedural outcomes. Objective: The authors sought to demonstrate a safe and efficient workflow for AF RFA using the EnSite™ X EP System, TactiCath™ Ablation Catheter, Sensor Enabled™ and Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ high-density mapping catheter. Methods: Forty-nine patients undergoing paroxysmal AF RFA procedures were studied retrospectively to evaluate efficiency and safety of a workflow designed to optimize mapping and ablation conditions. Anesthesia considerations were made to ensure proper accuracy during mapping and catheter stability during ablation. All patients were paralyzed after the right phrenic nerve was tagged and ventilation was kept at 25 breaths/min and a tidal volume of 250cc throughout the procedure. After double transseptal access was obtained, the ablation catheter was used to build VoXels for the entire left atrium (LA), which ensured better mapping accuracy with the Advisor™ HD Grid Mapping Catheter, Sensor Enabled™. RFA was delivered using First Line Efficiency with EnSite™ X EP System (F.L.E.X.) protocol standards of power, time, impedance drop and AutoMark lesion tags. Results: This workflow has enabled our center to perform RFA AF procedures with procedural times of 74.20±17.84 minutes, radiofrequency ablation times of 10.35±3.47 minutes, zero-fluoroscopy in 97.9% of patients and same-day discharge for 76% of patients. There were no anesthesia or other procedural related complications. Conclusions: The recent enhancements of the EnSite™ X EP System with EnSite™ VoXel Mode magnetic navigation can be used with a detailed procedural workflow that optimizes mapping and ablation, yielding a safe and efficient RFA for AF. [ABSTRACT FROM AUTHOR]