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The article presents a case study of a 21-year-old woman undergoing electrophysiological study for long RP (Refractory Period) tachycardia. It initially suspected atrial tachycardia or atypical atrioventricular nodal reentrant tachycardia (aAVNRT), later confirming slow-slow AVNRT. It is reported that Radiofrequency ablation targeted the AV (atrioventricular) node's right inferior extension, successfully resolving the tachycardia.

The article presents a case study of a 62-year-old female patient with irregular tachycardia. Topics discussed include the differential diagnoses of narrow QRS tachycardias such as atrial flutter and orthodromic reciprocating tachycardia, the results of the 12-lead electrocardiogram administered to the patient, and the clinical implications of regularly irregular tachycardia.

A 71-year-old male with persistent atrial fibrillation and a dual chamber permanent pacemaker presented complaining of dyspnea on exertion, easy fatiguability, and intermittent cough. A 12-lead electrocardiogram revealed ventricular paced complexes, native QRS complexes, and irregular atrial activity. Herein we present an unusual mechanism of atrioventricular dyssynchrony. (Level of Difficulty: Intermediate.)

Introduction: Persistent left superior vena cava (PLSVC) is accompanied by enlarged coronary sinus (CS) and deformation of the triangle of Koch. This makes anatomical evaluation of the atrioventricular (AV) nodal pathways difficult. Methods: We attempted cryoablation of retrograde fast pathway located in the enlarged CS roof of PLSVC for slow‐fast AV nodal reentrant tachycardia (AVNRT) induced by inadvertent antegrade fast pathway elimination during ablation of left atrial tachycardia. Results: Slow‐fast AVNRT was successfully eliminated without AV block progression. Conclusions: This is the first case of successful retrograde fast pathway ablation of the CS ostial roof for slow‐fast AVNRT with PLSVC. [ABSTRACT FROM AUTHOR]

Background: The management of patients with atrial fibrillation and an abnormally fast ventricular response has been through the use of pharmacologic agents. In those cases where rate control cannot be achieved pharmacologically, a standard approach has been atrioventricular (AV) junctional ablation and ventricular pacemaker implantation to achieve a stable ventricular rate. Long-term ventricular pacing has been shown to result in diminished ventricular function that can lead to heart failure. Objective: To describe an experimental and clinical study demonstrating a modified form of AV junction ablation. Methods: Ablation of the slow and fast AV nodal input does not produce AV block. Ablation of the connection between the two induces AV block, leaving the AV node and His bundle intact. Results: Subsequently the escape heart rate is close to normal and responds well to exercise. Conclusion: In a clinical study with a 42 month follow-up, the modified procedure resulted in significantly reduced pacemaker dependence and mortality compared to the standard AV ablation procedure.

The Atrio Ventricular Junction (AVJ) is a well-defined anatomical region of the heart the physiology of which, despite extensive and numerous observations, it is not fully understood. The aim of this review is to present an up to date summary of old and more recent findings on histology, cellular electrophysiology and intracellular connectivity of this region. We have also attempted to relate our increasing understanding of nodal pathophysiology to the interpretation of the electrocardiographic (ECG) manifestations of AVN behavior. Bridging cellular observations with ECG analysis in a process we call "Precision Electrocardiology" renders this tool far more sensitive and clinically useful than the pattern analysis too often employed in the ECG interpretation. [ABSTRACT FROM AUTHOR]

Aims: The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the atrioventricular node. This knowledge is crucial to understand the phenomenon of atrioventricular nodal re-entry.Methods and Results: We studied 20 human hearts with serial sections covering the entirety of the triangle of Koch and the cavotricuspid isthmus. We determined the location of the atrioventricular conduction axis and the connections between the specialized cardiomyocytes of the conduction axis and the adjacent working atrial myocardium. The atrioventricular node was found at the apex of the triangle of Koch, with entry of the conduction axis to the central fibrous body providing the criterion for distinction of the bundle of His. We found marked variation in the inferior extensions of the node, the shape of the node, the presence or absence of a connecting bridge within the myocardium of the cavotricuspid isthmus, the connections between the compact node and the myocardium of the atrial septum, the presence of transitional cardiomyocytes, and the 'last' connection between the working atrial myocardium and the conduction axis before it became the bundle of His.Conclusion: The observed variations of the inferior extensions, combined with the arrangement of the 'last' connections between the atrial myocardium and the conduction axis prior to its insulation as the bundle of His, provide compelling evidence to support the concept for atrioventricular nodal re-entry as advanced by Katritsis and Becker. [ABSTRACT FROM AUTHOR]

Introduction: Atrioventricular nodal re‐entry tachycardia (AVNRT) is the most common, regular narrow‐complex tachycardia. The established treatment is catheter ablation of the AV nodal slow pathway (SP). However, in a select group of patients with long PR intervals in sinus rhythm, SP ablation can lead to AV block due to the absence of robust anterograde conduction through the fast pathway (FP). This report aims to demonstrate that AV nodal FP ablation is a reasonable approach in patients with AVNRT and poor or absent anterograde FP conduction. Methods and Results: Standard electrophysiology study techniques were used in the electrophysiology laboratory. Catheter ablations were performed using radiofrequency energy. Mapping of intracardiac activation was performed with electroanatomical mapping systems. Outcomes were assessed acutely during the procedure and during routine clinical follow‐up. Six patients with first‐degree AV block and recurrent AVNRT who underwent ablation of their tachycardia at our institution are presented. One patient underwent ablation of AV nodal SP resulting in high‐degree AV block necessitating pacemaker implantation. The remaining five patients underwent ablation of the AV nodal FP guided by electroanatomical mapping of the earliest atrial activation in tachycardia. These five had successful treatment of the tachycardia with preservation of anterograde AV nodal conduction. Mapping and ablation approach to eliminate retrograde FP conduction are described. Conclusion: In select patients with AVNRT and poor anterograde FP conduction, retrograde FP ablation is reasonable and is less likely to result in AV block and pacemaker dependency. [ABSTRACT FROM AUTHOR]

A 66-year-old woman with palpitations was referred to our center for catheter ablation due to drug-refractory, common type atrioventricular nodal tachycardia (AVNRT). A selective slow pathway ablation was attempted. A fast junctional rhythm with transient ventriculoatrial block followed by transient prolongation of the A–H interval occurred immediately after the radiofrequency (RF) application at the coronary sinus ostium (CSOS) level. To assess the location of the fast pathway and His bundle, we sought to visualize the anatomy of the triangle of Koch (TOK) by three-dimensional computed tomography (CT).

The intracardiac electrograms are shown during scanned single premature ventricular extrastimuli with a decreasing coupling interval in a very short RP tachycardia. What is the diagnosis and is the fast pathway essential for sustaining the tachycardia?, Competing Interests: Authors declare no conflict of interests for this article., (© 2023 The Authors. Journal of Arrhythmia published by John Wiley & Sons Australia, Ltd on behalf of Japanese Heart Rhythm Society.)

Background: Dedicated mapping studies of the triangle of Koch to characterize retrograde fast pathway activation have not been previously performed using high-resolution, 3-dimensional, multielectrode mapping technology.Objective: To delineate the activation pattern and spatial distribution of the retrograde fast pathway within the triangle of Koch during typical atrioventricular nodal reentrant tachycardia (AVNRT) and right ventricular pacing in a consecutive series of patients using the Rhythmia mapping system (Boston Scientific, Natick, MA).Methods: A total of 18 patients with symptomatic typical AVNRT referred for ablation underwent ultra high-density mapping of atrial activation with minielectrode basket configuration during tachycardia. The earliest atrial activation was mapped using automated annotation, with manual overreading by 2 independent observers. The triangle of Koch was classified into 3 anatomic regions: anteroseptal (His), midseptal, and posteroseptal (coronary sinus roof). Thirteen patients underwent mapping of atrial activation during ventricular pacing.Results: A median of 422 mapping points (interquartile range 258-896 points) was acquired within the triangle of Koch during tachycardia. The most common site of earliest atrial activation within the triangle of Koch was anterior in 67% of patients (n = 12). Midseptal early atrial activation was seen in 17% (n = 3), and posteroseptal activation was observed in 11% (n = 2). One patient exhibited broad simultaneous activation of the entire triangle of Koch. Slow pathway potentials were not identified.Conclusions: With high-resolution multielectrode mapping, atrial activation during typical AVNRT exhibited anatomic variability and spatially heterogeneous activation within the triangle of Koch. These findings highlight the limitations of an anatomically based classification of atrioventricular nodal retrograde pathways. [ABSTRACT FROM AUTHOR]

The reported electrocardiogram shows several atrial extrasystoles (AEs) sometimes occurring in couplets. The former beat of each couplet is nonconducted, whereas the latter triggers a supraventricular tachycardia with negative P waves in inferior leads and RP > PR. This suggests an atypical atrioventricular nodal reentrant tachycardia involving the fast pathway anterogradely and the slow pathway retrogradely. The tachycardia is never precipitated by single AEs. The blocked AE of each pair is pivotal in tachycardia initiation, allowing the subsequent impulse to conduct down the fast pathway. A concealed slow pathway penetration during the blocked AE is invoked as the key mechanism. [ABSTRACT FROM AUTHOR]

Background: In contrast to the current textbook model and the current clinical index of dual pathway atrioventricular (AV) nodal conduction, here we summarize the discovery and validation of Zhang's phenomenon (originally His electrogram alternans) as a new index of dual pathway conduction. We also describe the new findings of transverse-versus-longitudinal electrical propagation within the AV node as the electrophysiological basis underlining this new index. Thus, a new index and a new model of dual pathway AV conduction are being developed.Methods: We have reviewed current literature and provided evidence supporting a new index and a new model of dual pathway AV conduction.Results: Recent data revealed that during fast pathway conduction, electrical excitation in the AV node propagates in a superior to inferior direction across AV conduction axis and fiber orientation to reach first the superior His bundle fibers. However, this transverse conduction can fail easily within the superior nodal domain at fast rates. The failing of transverse propagation permits electrical excitation formed at the posterior/inferior nodal region to propagate longitudinally along fiber orientation in a posterior to anterior direction through the inferior nodal domain to reach the inferior His bundle (slow pathway conduction). This transverse-versus-longitudinal electrical propagation within the AV node results in a functional dissociation in the distal node and formation of dual inputs into the His bundle, providing the electrophysiological basis for the formation of Zhang's phenomenon (His electrogram alternans).Conclusions: Based on strong experimental data, a new index and a new model of dual pathway AV nodal conduction are emerging, although they are still awaiting clinical validation. [ABSTRACT FROM AUTHOR]

A 71-year-old male with persistent atrial fibrillation and a dual chamber permanent pacemaker presented complaining of dyspnea on exertion, easy fatiguability, and intermittent cough. A 12-lead electrocardiogram revealed ventricular paced complexes, native QRS complexes, and irregular atrial activity. Herein we present an unusual mechanism of atrioventricular dyssynchrony. ( Level of Difficulty: Intermediate. )., Competing Interests: The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (© 2023 The Authors.)

A 66-year-old woman with palpitations was referred to our center for catheter ablation due to drug-refractory, common type atrioventricular nodal tachycardia (AVNRT). A selective slow pathway ablation was attempted. A fast junctional rhythm with transient ventriculoatrial block followed by transient prolongation of the A–H interval occurred immediately after the radiofrequency (RF) application at the coronary sinus ostium (CSOS) level. To assess the location of the fast pathway and His bundle, we sought to visualize the anatomy of the triangle of Koch (TOK) by three-dimensional computed tomography (CT). [ABSTRACT FROM AUTHOR]

Background: It is suggested that the adenosine resistance of retrograde fast pathway in slow-fast atrioventricular nodal reentrant tachycardia (AVNRT) confirms the participation of a concealed retrograde atrio-Hisian pathway rather than the conventional fast pathway in the arrhythmia circuit of slow-fast AVNRT. Objective: To prospectively assess the retrograde fast pathway response to the intravenous administration of adenosine in patients with typical AVNRT and the control group. Methods: Electrophysiological parameters and adenosine sensitivity of retrograde fast pathway were studied in 21 consecutive patients (18 women; mean age 57 ± 10 years) with slow-fast AVNRT and 24 patients (11 women; mean age 46 ± 16 years) as the control group. Results: Fifteen (71%) patients with AVNRT and 18 (75%) patients in the control group developed transient ventriculoatrial (VA) block after the intravenous administration of adenosine (P = .79). In patients with slow-fast AVNRT, female sex (P = .003), longer VA interval during right ventricular pacing (P < .001), and longer tachycardia cycle length (P < .001) predicted transient VA block after the intravenous administration of adenosine. In patients in the control group, a shorter VA interval during fixed rate right ventricular apical pacing (P = .009) and the presence of dual atrioventricular nodal physiology (P = .002) were associated with the adenosine resistance of the retrograde fast pathway. Conclusions: The prevalence of the adenosine resistance of retrograde fast pathway’s conduction is comparable between patients with and those without slow-fast AVNRT. This finding can be explained better by the existence of an insulated intranodal tract with Purkinje-like properties or a superior atrionodal connection to the nodo-Hisian region of the atrioventricular node rather than the presence of an atrio-Hisian pathway. [Copyright &y& Elsevier]

Abstract: Pulse gymnotids extract information about the environment using the pulsed discharge of an electric organ. Cutaneous electroreceptor organs transduce and encode the changes that objects imprint on the self-generated transcutaneous electric field. This review deals with the role of a neural circuit, the fast electrosensory path of pulse gymnotids, in the streaming of self generated electrosensory signals. The activation of this path triggers a low-responsiveness window slightly shorter than the interval between electric organ discharges. This phenomenon occurs at the electrosensory lateral line lobe where primary afferent terminals project on the somata of spherical neurons. The main subservient mechanism of the low-responsiveness window rely on the intrinsic properties of spherical neurons (dominated by a voltage dependent, low-threshold, non-inactivating and slowly-deactivating K+ conductance) determining the cell to respond with a single spike followed by a long refractory period. Externally generated signals that randomly occur within the interval between self-generated discharges are likely blocked by the low responsiveness window. Repetitive signals, as those emitted by conspecifics with a slightly lower rate, occur progressively at longer delays beyond the duration of the low responsiveness window. Transient increases of the discharge rate relocate the interference within the low-responsiveness window. We propose that this combination of sensory filtering and electromotor control favors the self-generated signals in detriment of other, securing the continuity of the electrolocation stream. [Copyright &y& Elsevier]

The article presents an anatomic model of the atrioventricular node (AVN) and relate it to AVN function. The anatomic model demonstrates the importance of the inferior nodal extension (INE) pacemaking and atrioventricular nodal reentry. The model can also be used to simulate the activation sequence of the AVN during normal anterograde conduction through the AVN, atrioventricular junctional pacemaking, and slow-fast and fast-slow atrioventricular nodal reentry.

Background: Concealed conduction is recognized as a major determinant of atrioventricular (AV) nodal filtering properties, but little is known about the underlying mechanisms.Objectives: The purpose of this study was to consistently elicit concealed conduction through the AV node and to determine the involvement of slow and fast pathways in resultant changes in nodal function.Methods: The concealment zone (nodal effective refractory period minus nodal functional refractory period of atrium) was determined in six rabbit heart preparations with and without a conditioning cycle (10 ms longer than nodal effective refractory period). Nodal function curves were constructed for concealed cycle lengths selected within the concealment zone. Experiments were repeated after slow pathway ablation.Results: When assessed with a blocked beat alone, a narrow concealment zone (22 +/- 12 ms, n = 3) was observed in 50% of the preparations. In contrast, when assessed with a blocked beat preceded by a conducted conditioning beat, a wider concealment zone (77 +/- 47 ms, n = 6, P <.03) was observed in all preparations. Increases in the concealed cycle length resulted in graded increases in the nodal effective refractory period and nodal functional refractory period and graded rightward shifts of the recovery curve as a whole, consistent with resetting of the excitability cycle in the slow and fast pathways. These effects were analogous to those expected from a conducted beat. Slow pathway ablation widened the concealment zone but failed to alter fast pathway resetting.Conclusion: Our approach reveals a wide concealment zone consistently displayed in all preparations. Concealed conduction acts as a resetting mechanism of the excitability cycle in the slow and fast pathways similar to that expected from a conducted beat. [ABSTRACT FROM AUTHOR]

In more than 95% of patients with atrioventricular nodal reentrant tachycardia (AVNRT), curative treatment can be achieved with selective ablation of the slow pathway in the right-sided septum. We report a patient with typical AVNRT who had failed attempts to perform conventional right septal ablation of the slow as well as of the fast pathway and finally underwent successful ablation of the fast pathway on the left side of the interatrial septum using a transseptal approach. [ABSTRACT FROM PUBLISHER]