EP Rounds

An 80-year-old man underwent catheter ablation for atrial tachycardia (AT), which developed after catheter ablation for atrial fibrillation. The AT was diagnosed as dual-loop tachycardia, which included peri-mitral and roof-dependent ATs. An ethanol infusion into the vein of Marshall resulted in left phrenic nerve paralysis. During the procedure, the phrenic nerve paralysis was completely relieved.

Introduction: Human atria comprise distinct epicardial layers, which can bypass endocardial layers and lead to downstream centrifugal propagation at the “epi-endo” connection. We sought to characterize anatomical substrates, electrophysiological properties, and ablation outcomes of “pseudo-focal” atrial tachycardias (ATs), defined as macroreentrant ATs mimicking focal ATs. Methods and Results: We retrospectively analyzed ATs showing centrifugal propagation with post-pacing intervals (PPIs) after entrainment pacing suggestive of a macroreentry. A total of 26 patients had pseudo-focal ATs consisting of 15 perimitral, 7 roof-dependent, and 5 cavotricuspid isthmus (CTI)-dependent flutters. A low-voltage area was consistently found at the collision site and co-localized with epicardial layers like the: (1) coronary sinus-great cardiac vein bundle (22%); (2) vein of Marshall bundle (15%); (3) Bachmann bundle (22%); (4) septopulmonary bundle (15%); (5) fossa ovalis (7%); and (6) low right atrium (19%). The mean missing tachycardia cycle length (TCL) was 67 ± 29 ms (22%) on the endocardial activation map. PPI was 9 [0-15] ms and 10 [0-20] ms longer than TCL at the breakthrough site and the opposite site, respectively. While feasible in 25 pseudo-focal ATs (93%), termination was better achieved by blocking the anatomical isthmus than ablating the breakthrough site [24/26 (92%) vs. 1/6 (17%); p < 0.001]. Conclusion: Perimitral, roof-dependent, and CTI-dependent flutters with centrifugal propagation are favored by a low-voltage area located at well-identified epicardial bundles. Comprehensive entrainment pacing maneuvers are crucial to distinguish pseudo-focal ATs from true focal ATs. Blocking the anatomical isthmus is a better therapeutic option than ablating the breakthrough site.

EP Rounds

Introduction: Ultra-high-density mapping for ventricular tachycardia (VT) is increasingly used. However, manual annotation of local abnormal ventricular activities (LAVAs) is challenging in this setting. Therefore, we assessed the accuracy of the automatic annotation of LAVAs with the Lumipoint algorithm of the Rhythmia system (Boston Scientific). Methods and Results: One hundred consecutive patients undergoing catheter ablation of scar-related VT were studied. Areas with LAVAs and ablation sites were manually annotated during the procedure and compared with automatically annotated areas using the Lumipoint features for detecting late potentials (LP), fragmented potentials (FP), and double potentials (DP). The accuracy of each automatic annotation feature was assessed by re-evaluating local potentials within automatically annotated areas. Automatically annotated areas matched with manually annotated areas in 64 cases (64%), identified an area with LAVAs missed during manual annotation in 15 cases (15%), and did not highlight areas identified with manual annotation in 18 cases (18%). Automatic FP annotation accurately detected LAVAs regardless of the cardiac rhythm or scar location; automatic LP annotation accurately detected LAVAs in sinus rhythm, but was affected by the scar location during ventricular pacing; automatic DP annotation was not affected by the mapping rhythm, but its accuracy was suboptimal when the scar was located on the right ventricle or epicardium. Conclusion: The Lumipoint algorithm was as/more accurate than manual annotation in 79% of patients. FP annotation detected LAVAs most accurately regardless of mapping rhythm and scar location. The accuracy of LP and DP annotations varied depending on mapping rhythm or scar location.

EP Rounds

Coronary artery injury is a rare complication of catheter ablation in the right ventricular outflow tract (RVOT). Furthermore, acute myocardial ischemia usually causes polymorphic ventricular tachycardia (VT) or ventricular fibrillation. We herein describe a case in which catheter ablation for VT originating from the RVOT provoked ischemia-related VTs due to acute occlusion of the left anterior descending artery.

Background Data on the optimal location of the ECG leads for the diagnosis of drug-induced long QT syndrome (diLQTS) with Torsades de Pointes (TdP) are lacking. Methods We systematically reviewed the literature for ECGs of patients with diLQTS and subsequent TdP. We assessed T-wave morphology in each lead and measured the longest QT interval in the limb and chest leads in a standardized fashion. Results Of 84 patients, 61.9% were female and mean age was 58.8 years. QTc was significantly longer in chest versus limb leads (mean (standard deviation) 671 (102) vs 655 (97) ms, p=0.02). Using only limb leads for QT interpretation, 18 (21.4%) ECGs were non-interpretable: 10 (11.9%) due to too flat T-waves, 7 (8.3%) due to frequent, early PVCs and 1 (1.2%) due to too low ECG recording quality. In the chest leads, ECGs were non-interpretable in 9 (10.7%) patients: 6 (7.1%) due to frequent, early PVCs, 1 (1.2%) due to insufficient ECG quality, 2 (2.4%) due to missing chest leads but none due to too flat T-waves. The most common T-wave morphologies in the limb leads were flat (51.0%), broad (14.3%) and late peaking (12.6%) T-waves. Corresponding chest lead morphologies were inverted (35.5%), flat (19.6%) and biphasic (15.2%) T-waves. Conclusions Our results indicate that QT evaluation by limb leads only underestimates the incidence of diLQTS experiencing TdP and favors the screening using both limb and chest lead ECG.

Near-field Signals Detected by a Standard Bipolar Electrode without Detection of Corresponding Signals by Microelectrode: What is the Mechanism?Short title ; Near-filed Microelectrode signalTakashi Nakashima, MD*, Cyril Goujeau, MD, Yosuke Nakatani, MD,Ghassen Cheniti, MD, Pierre Jaïs, MD, Frédéric Sacher, MDAll authors have no conflicts of interest to disclose.Department of Cardiac Electrophysiology, Service de Rhythmologie, Hôpital Cardiologique du Haut-Lévêque (Centre Hospitalier Universtaire de Bordeaux)Avenue de Magellan, 33604, Bordeaux-Pessac, FranceCorrespondence to Takashi Nakashima, MDDepartment of Cardiac Electrophysiology, Service de Rhythmologie, Hôpital Cardiologique du Haut-Lévêque (Centre Hospitalier Universtaire de Bordeaux)Avenue de Magellan, 33604, Bordeaux-Pessac, FranceTel: +33 5 57 65 68 63 19, Fax: +33 5 57 65 68 96 20, Email; [email protected], ORCID: 0000-0002-8538-9259Key words: Ablation; Electrogram analysis; Microelectrode; Ventricular tachycardia