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Background: The role of catheter tip shape on the safety and efficacy of radiofrequency (RF) ablation has been overlooked, although differences have been observed in clinical and research fields., Objective: The purpose of this study was to analyze the role of electrode tip shape in RF ablation using a computational model., Methods: We simulated 108 RF ablations through a realistic 3-dimensional computational model considering 2 clinically used, open-irrigated catheters (spherical and cylindrical tip), varying contact force (CF), blood flow, and irrigation. Lesions are defined by the 50°C isotherm contour and evaluated by means of width, depth, depth at maximum width, and volume. Ablations are deemed as safe, critical (tissue temperature >90°C), and pop (tissue temperature >100°C)., Results: Tissue-electrode contact is less for the spherical tip at low CF but the relationship is inverted at high CF. At low CF, the cylindrical tip generates deeper and wider lesions and a 4-fold larger volume. With increasing CF, the lesions generated by the spherical tip become comparable to those generated by the cylindrical tip. The 2 tips feature different safety profiles: CF and power are the main determinants of pops for the spherical tip; power is the main factor for the cylindrical tip; and CF has a marginal effect. The cylindrical tip is more prone to pop generation at higher powers. Saline irrigation and blood flow effect do not depend on tip shape., Conclusion: Tip shape determines the performance of ablation catheters and has a major impact on their safety profile. The cylindrical tip shows more predictable behavior in a wide range of CF values., (© 2022 Heart Rhythm Society. Published by Elsevier Inc.)

Objectives: The aim of this study was to describe a mapping approach for ablation of complex atrial re-entrant tachycardias (ARTs) in which high-density activation maps are transformed into low-density activation maps displaying only the active part of the tachycardia circuit., Background: High-density activation maps during complex ARTs are challenging to interpret because they include the activation patterns of active and passive circuits. Entrainment mapping provides the identification of the active tachycardia circuit. However, current electroanatomic mapping systems are not capable of color-coding the information obtained from entrainment maneuvers., Methods: Seventeen consecutive patients with atypical atrial flutter were included. A high-density activation map was acquired during index tachycardia. Subsequently, entrainment maneuvers were performed to generate a low-density activation map in which only the activation of the atria directly involved in the flutter circuit was displayed., Results: Of all patients included, 82% were men, and their mean age was 62 ± 7 years. Structural heart disease was present in 59%, and 53% had undergone prior left atrial ablation procedures. Low-density activation maps were successfully generated from an average of 14 ± 3 entrainment points. Twenty circuits (95%) were identified in the left atrium and 1 (5%) in the right atrium. Ablation guided by low-density mapping successfully terminated all ARTs in 267 ± 353 s of radiofrequency application., Conclusions: Low-density mapping based on entrainment maneuvers provides a precise delineation of the active circuit during complex ARTs and resulted in successful arrhythmia termination. This approach can be easily incorporated into clinical practice., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: Left atrial (LA) low-voltage substrate (LVS) potentially slows intra-atrial conduction, which might identify patients at risk for arrhythmia recurrence following pulmonary vein isolation (PVI)., Background: Up to 50% of patients with persistent atrial fibrillation (AF) have arrhythmia recurrence following PVI, mostly due to arrhythmogenic LA LVS., Methods: Seventy-two patients with persistent AF underwent electrocardioversion to sinus rhythm and high-density voltage mapping of the left atrium. Invasively measured LA activation time and P-wave duration (PWD; total PWD and LA PWD [measured from -dV/dt in leads V 1 and V 2 until the end of the P-wave]) on amplified (40 to 50 mm/mV, 100 to 200 mm/s) digitized 12-lead electrocardiography (ECG) were compared with the extent of LA LVS (<0.5 and <1. 0mV). Freedom from arrhythmia following PVI was evaluated in 143 patients with persistent AF stratified according to amplified PWD before ablation., Results: LA LVS resulted in regional conduction delay, which increased LA activation time (r = 0.79). LA PWD strongly correlated with LA activation time (r = 0.96) and LA LVS (r = 0.80). As the first (right atrial) portion of the P-wave (from P-wave beginning until -dV/dt in leads V 1 and V 2 ) was not affected by LA LVS, total PWD correlated with LA LVS (r = 0.84). PWD ≥150 ms identified advanced LA LVS with 94.3% sensitivity and 91.7% specificity. One-year arrhythmia freedom following PVI-only was significantly higher in patients with PWD <150 ms (n = 73) compared with those with prolonged PWD ≥150 ms (n = 70) (72.0% vs. 40.8%; p = 0.003)., Conclusions: Advanced arrhythmogenic LVS is associated with significant intra-atrial conduction delay, which is accurately measurable by prolongation of PWD on amplified 12-lead ECG. PWD ≥150 ms during sinus rhythm measured prior to ablation identifies patients with persistent AF who are at increased risk for arrhythmia recurrence following PVI., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)