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Atrial tachycardia (AT) with alternating cycle lengths is sparsely reported, and, hence, the ideal mapping strategy has not been firmly established. Beyond the entrainment during tachycardia, some fragmentation characteristics might also give important clues for its possible participation in the macro-re-entrant circuit. We discuss a patient with prior atrial septal defect surgical closures who presented with dual macro-re-entrant ATs related to a fragmented area on the right atrial free wall (240 ms) and the cavotricuspid isthmus (260 ms), respectively. After ablation of the fastest AT on the lateral right atrial free wall, the cycle of the first AT changed to the second AT that was interrupted on cavotricuspid isthmus, proving the dual tachycardia mechanism. This case report addresses the utilization of electroanatomic mapping information as well as fractionated electrogram timing with respect to the surface P-wave as guides for ablation location., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided., (Copyright: © 2023 Innovations in Cardiac Rhythm Management.)

The cardiac Purkinje system is capable of very rapid burst activity suggestive of its potential role in being a driver of polymorphic ventricular tachycardia (VT) (PMVT) or ventricular fibrillation (VF). It plays a pivotal role, however, not only in the triggering of but also the perpetuation of ventricular arrhythmias. A varying degree of Purkinje-myocardial complicity has been blamed in determining not only the sustained or non-sustained nature of PMVT but also the pleomorphism of the non-sustained runs. The initial part of PMVT before cascading to the whole ventricle to establish disorganized VF can give important clues for ablation of PMVT and VF. We present a case of an electrical storm after acute myocardial infarction that was successfully ablated after identifying Purkinje potentials that triggered polymorphic, monomorphic, and pleiomorphic VTs and VF., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided. This case was presented December 10, 2022 at the EP Finishing School., (Copyright: © 2023 Innovations in Cardiac Rhythm Management.)

Para-Hisian pacing (PHP) is among the most useful maneuvers in cardiac electrophysiology during sinus rhythm and identifies whether retrograde conduction is dependent on the atrioventricular (AV) node. In this maneuver, the retrograde activation time and pattern are compared during capture and loss of capture of the His bundle while pacing from a para-Hisian position. A common misconception about PHP is that it is useful only for septal accessory pathways (APs). However, even with left or right lateral pathways, as long as pacing from the para-Hisian region conducts to the atrium with the activation sequence being analyzed, it can be used to determine whether that activation is AV node-dependent or AP-dependent., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided., (Copyright: © 2023 Innovations in Cardiac Rhythm Management.)

Tachycardia-induced tachycardia, or so-called double tachycardia, appears to be a relatively rare condition. The underlying mechanism for stable beat-to-beat cycle length variability (alternans) in atrial tachycardia has been sparsely reported., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided., (Copyright: © 2023 Innovations in Cardiac Rhythm Management.)

The analysis of the patterns and timing of coronary sinus activation provides a rapid stratification of the most likely macro-re-entrant atrial tachycardias and points toward the likely origin of centrifugal ones by comparing the left atrial and coronary sinus activation sequence and morphology during sinus rhythm and atrial tachycardia. The analysis of both the near- and far-field electrogram morphology of atrial signals also gives important clues in determining the mechanism of the arrhythmia., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided., (Copyright: © 2023 Innovations in Cardiac Rhythm Management.)

A change in the coronary sinus (CS) activation pattern from an eccentric to a concentric pattern during the ablation of an orthodromic reciprocating tachycardia might falsely suggest the presence of a second (septal) accessory pathway (AP) during tachycardia or the successful ablation of the left lateral AP under ventricular pacing despite persistent and unaffected AP conduction. Complete or partial intra-atrial block should be suspected when an abrupt change in the atrial activation sequence is noted during catheter ablation at the posterolateral and lateral aspects of the mitral annulus. The correct anatomical position of the CS catheter plays a vital role in the differential diagnosis of this situation., Competing Interests: The authors report no conflicts of interest for the published content. No funding information was provided., (Copyright: © 2022 Innovations in Cardiac Rhythm Management.)

The presence of 2 ventricular signals caused by structures near the His bundle region is rare. Some associative and dissociative maneuvers for dissociating a certain electrical signal from others of known origin are used to ascertain the source of an unknown potential., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2022 Innovations in Cardiac Rhythm Management.)

Electrocardiography has certainly great merit and is almost abnormal in most patients with Ebstein's anomaly. Incomplete or complete right bundle brunch block (RBBB) is seen in almost half of these patients. The absence of the expected RBBB during sinus rhythm in a patient with Ebstein's anomaly is a useful clue of pre-excitation in these patients., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2022 Innovations in Cardiac Rhythm Management.)

We present a patient with ischemic cardiomyopathy who had ventricular tachycardia (VT) with QRS morphology alternans. The electrophysiological findings, in this case, supported the occurrence of antegrade activation of the proximal His-Purkinje system during VT, with the ultimate electrocardiogram morphology dependent on fusion from intramyocardial and His-Purkinje activations., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2022 Innovations in Cardiac Rhythm Management.)

The differential diagnosis for a wide complex tachycardia includes all causes of supraventricular tachycardia (SVT) with bundle branch block or all causes of SVT with antegrade pre-excitation by bystander involvement of any accessory pathways, myocardial or bundle brunch ventricular tachycardia, and antidromic (atriofascicular or nodofascicular/nodoventricular) and other pre-excited reciprocating tachycardias. We present a case of wide complex QRS tachycardia with a left bundle branch block QRS morphology., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2021 Innovations in Cardiac Rhythm Management.)

In patients with mechanical aortic and mitral valves and left ventricular (LV) tachycardia (VT), catheter ablation is technically challenging due to the limited access to the LV. Promising new alternatives to radiofrequency ablation include pulsed-field electroporation, percutaneous or surgical sympathetic neuromodulation, and noninvasive stereotactic radioablation therapy (SBRT). We herein describe the effect of SBRT as a bailout therapy on the management of a challenging VT case in the presence of double left-sided mechanical valves., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2021 Innovations in Cardiac Rhythm Management.)

In equivocal or suspected cases of Brugada syndrome (BrS), ajmaline testing is frequently used in the diagnostic approach. However, the administration of sodium channel blockers can not only elicit the coved ST-segment elevation characteristic of type 1 Brugada pattern but also induce right bundle branch block (RBBB), which can preclude the electrocardiographic manifestations of BrS. We describe a case report wherein RBBB posed a diagnostic challenge during the ajmaline test for suspected BrS., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2021 Innovations in Cardiac Rhythm Management.)

The differential diagnosis of a regular, narrow QRS, long-R-P tachycardia includes atypical atrioventricular nodal reentry tachycardia, atrial tachycardia, and atrioventricular reentry tachycardia via a slowly conducting accessory pathway with decremental conduction properties. Almost all described diagnostic maneuvers in the electrophysiology laboratory have exceptions to their primary interpretation. The usual proviso is that the observation must be reproducible., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2021 Innovations in Cardiac Rhythm Management.)

Mechanical prosthetic aortic and mitral valves preclude either a retrograde aortic or transseptal approach to the left ventricular (LV) endocardium. Several operators have reported on the application of nonconventional techniques for ventricular tachycardia (VT) ablation including transventricular septal puncture, epicardial approach, transmechanical valve approach, transcoronary venous approach, and transapical approach. Incorporating transventricular access to the LV under intracardiac echocardiography (ICE) guidance has been previously attempted in VT ablation procedures in patients with both aortic and mitral mechanical valves. However, while ICE is readily used in the United States, its use is less common in Europe, since the health insurance agencies largely do not cover the costs of ICE catheters. We therefore herein present a case of VT ablation in the LV using a transventricular approach in a patient who underwent mechanical double valve replacement performed under subcostal echocardiographic and fluoroscopic guidance., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2019 Innovations in Cardiac Rhythm Management.)

Symptomatic obstruction of the superior vena cava can be caused by either intrathoracic malignancy or nonmalignant etiology, resulting in superior vena cava syndrome (SVCS). The widespread use of central venous catheters, ports, pacemakers, and defibrillators has increased the incidence of benign SVCS. We present a post-pacemaker-implantation case of SVCS manifesting as positional syncope. The percutaneous intervention of stent implantation after lead removal followed by reimplantation of the leadless pacemaker may be a potential alternative treatment for pacemaker-induced SVCS, since some cases eventually may require repeat intervention., Competing Interests: The authors report no conflicts of interest for the published content., (Copyright: © 2018 Innovations in Cardiac Rhythm Management.)