Slow Atrioventricular Nodal Pathway Research Articles

Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Patients With Congenital Heart Disease.

Atrioventricular (AV) nodal reentrant tachycardia represents the most common regular supraventricular arrhythmia in humans, and catheter ablation of the so called slow AV nodal pathway has been effectively performed for decades. In patients with congenital heart disease, a combination of different factors makes catheter ablation of AV nodal reentrant tachycardia substrate particularly challenging, including abnormal venous access to intracardiac structures, abnormal intracardiac anatomy, potentially deviant and often unpredictable sites of the specific conduction system, loss of traditional anatomic landmarks, and congenital cardiac surgery that may complicate the access to the AV nodal area. Published experiences have confirmed the efficacy and the relative safety of such procedures when performed by experts, but the risk of complications, in particular AV block, remains non-negligible. A thorough knowledge and understanding of anatomic and electrical specificities according to underlying phenotype are essential in addressing these complex cases. Considering the major consequences associated with AV block in patients with complex congenital heart disease, particularly those without low risk access for transvenous ventricular pacing (eg, single ventricle physiology or Eisenmenger syndrome), the individual risk-benefit ratio should be carefully evaluated. The decision to defer ablation may be the wisest approach in selected patients with either infrequent or hemodynamically tolerated arrhythmias, or when the location of the AV conduction pathways remains uncertain. This narrative review aims to synthetize existing literature on catheter ablation of AV nodal reentrant tachycardia in congenital heart disease, to present main features of common associated pathologies, and to discuss approaches to mapping and safely ablating the slow AV nodal pathway in challenging cases.

Miniseries 2-Septal and paraseptal accessory pathways-Part III: Mid-paraseptal accessory pathways-revisiting bypass tracts crossing the pyramidal space.

The mid-paraseptal region corresponds to the portion of the pyramidal space whose right atrial aspect is known as the triangle of Koch. The superior area of this mid-paraseptal region is also para-Hisian, and is close to the compact atrioventricular node and the His bundle. The inferior sector of the mid-paraseptal area is unrelated to the normal atrioventricular conduction pathways. It is, therefore, a safe zone in which, if necessary, to perform catheter ablation. The middle part of the mid-paraseptal zone may, however, in some patients, house components of the compact atrioventricular node. This suggests the need for adopting a prudent attitude when considering catheter ablation in this area. The inferior extensions of the atrioventricular node, which may represent the substrate for the slow atrioventricular nodal pathway, take their course through the middle, and even the inferior, sectors of the mid-paraseptal region. In this review, we contend that the middle and inferior areas of the mid-paraseptal region correspond to what, in the past, was labelled by most groups as the 'midseptal' zone. We describe the electrocardiographic patterns observed during pre-excitation and orthodromic reciprocating tachycardia in patients with pathways ablated in the middle or inferior sectors of the region. We discuss the modification of the ventriculo-atrial conduction times during tachycardia after the development of bundle branch block aberrancy. We conclude that the so-called 'intermediate septal' pathways, as described in the era of surgical ablation, were insufficiently characterized. They should not be considered the surrogate of the 'midseptal' pathways defined using endocardial catheter electrode mapping.

Automated rhythm-based control of radiofrequency ablation close to the atrioventricular node: Preclinical, animal, and first-in-human testing

The risk of heart block during radiofrequency ablation of atrioventricular (AV) nodal reentrant tachycardia and septal accessory pathways is minimized by rapidly ceasing ablation in response to markers of risk, such as atrioventricular dissociation, fast junctional rhythm, PR interval prolongation, or 2 consecutive atrial or ventricular depolarizations. Currently this is done manually. The objectives of this study were to build and test a control system able to monitor cardiac rhythm and automatically terminate ablation energy when required. The device was built from off-shelf componentry. Preclinical testing involved real-time input of electrogram/electrocardiogram data from 209 ablation procedures (20 patients) over slow (n = 19) and fast (n = 1) AV nodal pathways. The device response speed was compared with the human response speed. The device's ability to prevent heart block was tested in 5 sheep. First-in-human testing was then performed in 12 patients undergoing AV nodal reentrant tachycardia ablation. Risk conditions necessitating shutoff of ablation (200 total; 111 preclinical and 89 first-in-human) were detected by the device with 100% sensitivity and 94% specificity, automatically terminating ablation while still allowing successful ablation in all patients. Device shutoff of ablation was always faster than human response (median difference 1.24 seconds). In each of 5 sheep, 40 consecutive attempts to cause heart block by ablating over the His bundle were unsuccessful because of automatic shutoff in response to rhythm change. Automated shutoff of ablation close to the AV node in response to markers of the risk of heart block is feasible with high accuracy as well as faster response than human response. The system may improve the safety of ablation near the AV node by preventing heart block.

Medical and Interventional Outcomes in Pediatric Lone Atrial Fibrillation.

The goal of this study was to describe the clinical characteristics of pediatric patients with lone atrial fibrillation (LAF) and their treatment outcomes. The authors focused on patients who underwent ablation and compared the recurrence after ablation of supraventricular tachycardia substrates as presumed triggers versus pulmonary vein isolation (PVI). LAF in pediatrics is rare, and outcomes remain poorly defined. Current guidelines on ablation are based on a few small studies, and we present outcomes from the largest cohort of patients after ablation. This retrospective review included patients≤21 years of age diagnosed with LAF from 2004 to 2015. Relevant clinical data, including recurrence rates after treatment, were tracked and analyzed with a focus on patients who underwent ablation procedures. Sixty-two patients were identified with LAF; 88% were male, and 63% were athletes. Of the 33 patients taking antiarrhythmic medication, 20 (61%) experienced recurrence. Overall, 16 patients (26%) underwent ablation: PVIin 10 (62.5%), ablation of an accessory pathway in 3 (19%), and modification of the slow atrioventricular nodalpathway in 3 (19%). One-half of patients who underwent PVI experienced documented recurrence. Of those who solely underwent supraventricular tachycardia substrate ablation, one-half also had symptomatic or documented recurrence. Ablation recurrence within this pediatric cohort was higher than expected. These recurrence ratesmaybe demonstrative of the technical challenge of pediatric ablation compared with adult counterparts, characteristics of these patients such as athletic conditioning, or inherent differences in their atrial tissue, renderingitmore refractorytosubstrate modification.

Dual atrioventricular nodal pathways: physiology, arrhythmic findings, and electrocardiographic manifestations

The atrioventricular (AV) node is an anatomically well-defined structure, conveniently housed in the triangle of Koch. There are two distinct atrial impulse approaches to the AV node, one of which (in the anterior portion of triangle of Koch) has a faster conduction, while the other one (in the posterior portion) has a slower conduction. However, it is not said that such a conductive duality translates into any arrhythmic phenomena. Actually, these arrhythmias are due to an imbalance of the two pathways electrophysiological properties, which does not always exist. In the presence of such an imbalance, the dual AV nodal physiology is, however, the substrate for various arrhythmias and curious electrocardiographic behaviors. Often the fast pathway is characterized by a relatively long refractory period. In contrast, the slow approach is often characterized by shorter refractoriness.The unbalanced refractoriness of the two nodal pathways constitutes the prerequisite for the most common form of paroxysmal supraventricular tachycardia: the AV nodal reentrant tachycardia (AVNRT). In subjects prone to this type of arrhythmia, during sinus rhythm, nodal conduction usually occurs from the anterior approach (fast pathway). However, a premature atrial beat may find this pathway refractory and cross the AV node through the posterior approach (slow pathway), resulting in a sudden prolongation of the AV conduction time ("jump"). This allows the impulse, once it reaches the common end, to excitate the fast pathway in a retrograde direction and to return backwards to the atrium, thus triggering a circus movement that can result in a "slow-fast" AVNRT. More rarely, an AVNRT can take place in an opposite direction of the reentrant impulse ("fast-slow" variety of AVNRT). A paroxysmal supraventricular tachycardia may seldom occur with a regularly alternating RR cycle, if the reentrant mechanism involves retrogradely an accessory AV pathway and, in anterograde direction, a fast and a slow AV nodal pathway, alternately. Among the mechanisms underlying the total RR irregularity during atrial fibrillation, there is probably also the possibility that the AV node may offer to the atrial impulses two distinct pathways to reach the His bundle. Not too rarely, a dual AV nodal physiology can occur during sinus rhythm, through unexpected and sudden changes in the AV conduction time, so that two distinct PR families can be observed. It is likely that the presence of dual AV nodal pathways can facilitate or promote a Wenckebach conduction mechanism at nodal site.

Sex Differences in Cardiac Arrhythmias: Clinical and Research Implications.

Sex differences have the potential to impact diagnostic and therapeutic interventions in a wide variety of medical conditions, and cardiac arrhythmias are no exception.1 Studies evaluating pathophysiology, disease course, and therapeutic options for cardiac arrhythmias have been performed predominantly in male patients. However, catheter and device-based therapies coupled with landmark clinical trials have contributed to an improved understanding of this important aspect. The objective of this review is to present the current state of knowledge on sex differences in cardiac arrhythmias with a focus on clinical management, while highlighting gaps in knowledge that would benefit from future investigation. ### Atrial Fibrillation and Atrial Flutter #### Disease Burden Atrial fibrillation (AF) and atrial flutter (AFL) are the most commonly encountered tachyarrhythmias in clinical practice, with significant implications for public health and healthcare costs. Stroke, hospitalization, and loss of productivity are the major consequences of AF.2 The incidence of AF (per 1000 person-years) is reported to be between 1.6 and 2.7 in women and between 3.8 and 4.7 in men.2 The age-adjusted incidence and prevalence of AF is lower in women compared with that in men, and accordingly, the lifetime risk of AF from the Framingham Heart Study at 40 years of age was higher in men (26.0% for men versus 23.0% for women).3 Another analysis from the Framingham Heart Study demonstrated no significant sex differences in the risk of developing AFL.4 The prevalence of AF continues to rise among both men and women. In a study investigating the global burden of disease from 1980 to 2010, there was not only an increase in overall burden, incidence, and prevalence of AF, but most importantly an increase in AF-associated mortality in both men and women (Figure 1).5 The age-adjusted mortality for women was consistently higher compared with that for men from 1990 to 2010 (Figure …

073_16823-L2 Compared the Efficacy of Cryoablation and Rradiofrequency Ablation for Treatment of Atrioventricular Nodal Reentrant Tachycardia

Radiofrequency (RF) ablation of the atrioventricular nodal slow pathway is the accepted treatment for atrioventricular nodal reentrant tachycardia (AVNRT), with success rates greater than 90%. The major risk is atrioventricular nodal block requiring permanent pacemaker implantation. Cryoablation is

Zablokowane ExSV czy pojedyncze pobudzenia nawrotne? Jeden zapis, dwie interpretacje

W artykule przedstawiono opis przypadku mlodej pacjentki z wywiadem napadowych czestoskurczow nadkomorowych poddanej inwazyjnemu badaniu elektrofizjologicznemu i jednoczasowo ablacji drogi wolnej wezla przedsionkowo-komorowego. W 24-godzinnym monitorowaniu elektrokardiograficznym metodą Holtera, wykonanym dobe po zabiegu, okresowo obserwowano zapis, ktory, zdaniem autorow, mozna rownoprawnie interpretowac na dwa sposoby — jako przedwczesne pobudzenia przedsionkowe zablokowane lub wsteczną aktywacje przedsionkow.

Analysis of atrioventricular function and its efficacy in patients with AVNRT undergoing atrioventricular junction ablation of slow conduction pathway

Objective The electrophysiological parameters of atrioventricular conduction function in patients with atrioventricular nodal reentry tachycardia (AVNRT) were analyzed, and to explore the effect of different ablation endpoints on atrioventricular conduction function in patients with AVNRT. Methods 96 cases with AVNRT underwent radiofrequency catheter ablation (RFCA) of slow conduction pathway.According to whether the slow pathway eliminated, the patients were divided into the slow pathway disappeared group and slow tracks remaining group.Preoperative and postoperative intracavitary electrophysiological examination and atrioventricular function data were recorded, including before and after radiofrequency ablation of bundle of HIS, PA, AH, HV interval, atrioventricular prequel venturi point(AVN-WKB), ventriculoatrial retrograde venturi point(VAN-WKB), atrioventricular node prequel effective refractory period(AVB-WKB). Patients were followed up by telephone for a year.Then, a comparative analysis of preoperative and postoperative was done. Results RFCA of AVNRT patients with atrioventricular node prequel time effect: RFCA and preoperative ratio, after his bundle electrogram PA, ah, HV interval had no significant changes(P>0.05). Effect of RFCA surgery on patients with AVNRT refractory atrioventricular node prequel: compared with RFCA before surgery, postoperative slow pathway disappear fast pathway shortening of effective refractory period[preoperative(287.5±46.2)ms, postoperative(260.2±55.6)ms, t=2.901, P=0.005], slow pathway effective refractory period[disappear preoperative(243.3±43.2), postoperative(0.0±0.0)ms, t=43.290, P=0.000], AV node Wenckebach point in advance before operation[(261.3±44.3)ms, postoperative(293.2±46.2)ms, t=3.828, P=0.000]; group after slow pathway to improve fast pathway effective refractory period without obvious change(P>0.05), the slow pathway effective refractory period in high concentration[preoperative(242.2±42.8)ms, postoperative(281.2±41.3)ms, t=3.879, P=0.000], atrioventricular node Wenckebach point in advance before operation[(261.5±43.5)ms, postoperative(291.3±46.5)ms, t=2.769, P=0.007]. Comparison between groups, after slow pathway disappeared group fast pathway effective refractory period was significantly shorter in the slow diameter improvement group, but between the two groups in the atrioventricular node Wenckebach point differences was not statistically significant(P>0.05). There was no recurrence in the follow-up after a year of slow path loss and slow pathway. Conclusion RFCA caused by slow pathway to disappear or modified two slow pathway ablation right AVNRT patients atrioventricular time had no effect, but all the atrioventricular junction the prequel's point advance.The atrioventricular node slow pathway disappear fast and effective pathway refractory period shortened, slow pathway improved the slow pathway effective refractory period.RFCA surgery done by the slow pathway disappeared or slow pathway ablation is effective in patients with AVNRT, and there was no significant recurrence rate in both groups within 1 year. Key words: Ablation; Tachycardia; Atrioventricular conduction function

Dual atrioventricular nodal non-re-entrant tachycardia.

Dual atrioventricular nodal non-re-entrant tachycardia (DAVNNT), also known as 'double fire', has recently received more attention since it was demonstrated to mimic more common arrhythmias such as atrial premature beats, atrial fibrillation, and ventricular tachycardia. This is important, since mistaken differential diagnoses and the resulting therapeutic decisions have severe consequences for affected patients. DAVNNT is characterized by conduction characteristics of the atrioventricular (AV) node that leads to a double antegrade conduction of one sinoatrial nodal activity via the slow and fast AV nodal pathways. As a result, the most significant hint from an electrocardiogram (ECG) is a P wave followed by two narrow QRS complexes. Although DAVNNT is rather a rare arrhythmia, it now appears to be more common than previously thought. To date, 68 cases including 3 small single-centre observational studies accumulated over the last 5 years have demonstrated the feasibility and safety of radiofrequency catheter ablation for DAVNNT. Catheter ablation treats this arrhythmia effectively by modifying or eliminating slow pathway function. Here, we review the current state of DAVNNT knowledge systematically and address current challenges presented by this 'ECG chameleon from the AV node'.

Visualization of Atrioventricular Nodal Reentry Tachycardia Slow Pathways Using Voltage Mapping for Pediatric Catheter Ablation.

Catheter ablation of the slow atrioventricular (AV) pathway has been shown to be safe and effective in pediatric patients with atrioventricular nodal reentrant tachycardia (AVNRT). Despite that, acute success is not guaranteed, and safety of ablating near the AV node remains a concern. A retrospective analysis was performed of all AVNRT ablations using the Ensite NavX voltage mapping technique at our institution. Each map was reviewed with patient and NavX computer data recorded. To account for a learning curve, each map was idealized and compared with the original map. Procedure and fluoroscopy time were compared with a control group. Twenty-eight patients underwent catheter ablation for AVNRT from September 2011 until December 2012 using the voltage mapping technique. The historical control group comprised 24 patients who underwent catheter ablation using the electroanatomic approach. There was 96% acute success with one recurrence in the voltage mapping group, at a mean follow-up of 24 months. The slow pathway was visualized in 86% of patients at the time of ablation, while three of four without could be found on idealization of the voltage map. Mean high- and low-voltage parameters increased with idealization, but showed no correlation with age, gender, or weight. Estimated pathway size had significant inter-patient variability. Procedure and fluoroscopy times did not vary significantly compared with controls. Visualization of the AV nodal slow pathway in a pediatric population is possible using voltage mapping technique with the potential to increase safety and efficacy. Variability exists in the voltage parameters needed to visualize individual slow pathways, which leads to a distinct learning curve.

Two difficult cases of radiofrequency catheter ablation for atrioventricular nodal slow pathway

Two difficult cases of radiofrequency catheter ablation for atrioventricular nodal slow pathway

Supraventricular tachycardia with broad QRS complexes and atrioventricular dissociation — is that possible?

We present a case of broad QRS complex tachycardia and atrioventricular (AV) dissociation that was documented during electrophysiological study to be a supraventricular rather than a ventricular tachycardia. Ablation of AV nodal slow pathway eliminated the arrhythmia confirming the diagnosis of atypical AV nodal reentrant tachycardia.

Catheter Ablation of an Unusual Decremental Accessory Pathway in the Left Coronary Cusp of the Aortic Valve Mimicking Outflow Tract Ventricular Tachycardia

The anatomic location of atrioventricular (AV) bypass tracts (or accessory pathways) is variable, but these generally traverse the tricuspid or mitral annulus and insert into the atrium and ventricle near the AV ring. There is only 1 case report of an accessory pathway ablated in the left coronary cusp (LCC),1 and this pathway had bidirectional conduction, was not decremental, and was associated with an orthodromic tachycardia. We report here the first case of an antegrade slowly conducting, decremental, accessory pathway that was also successfully ablated in the aortic LCC. This pathway generated antidromic tachycardia having a QRS morphology mimicking those seen in outflow tract ventricular tachycardia. A 42-year-old woman was evaluated for palpitations and presyncope for 2 years. These were commonly associated with shortness of breath and chest heaviness that would resolve spontaneously. Her baseline ECG was normal without ventricular preexcitation. Echocardiogram, coronary angiogram, and thyroid function were also unremarkable. On her third presentation to a hospital, a broad complex tachycardia was captured (representative 12-lead ECG shown in Figure 1). The cycle length was 480 ms, the QRS duration was 150 ms, and a left bundle branch morphology with a right inferior axis was noted. She was referred for ablation of suspected ventricular outflow tract tachycardia. Consent was obtained for mapping and ablation of this tachycardia. During placement of catheters, a spontaneous initiation of tachycardia occurred, which was noted to have 1:1 AV association. A quadripolar catheter was placed at the right ventricular apex and His bundle, with a decapolar catheter in the coronary sinus. During ventricular pacing, retrograde conduction occurred with a long ventriculoatrial interval. Tachycardia was readily initiated with ventricular premature beats showing retrograde decremental conduction (Figure 2). An antegradely conducting accessory pathway was noted during atrial pacing maneuvers. During delivery of premature atrial stimulations, shortening of …

Ivabradine in the Treatment of Inappropriate Sinus Tachycardia in Patients after Successful Radiofrequency Catheter Ablation of Atrioventricular Node Slow Pathway

Inappropriate sinus tachycardia (IST) occurs relatively common after catheter ablation of slow pathway in patients with atrioventricular nodal reentrant tachycardia. The treatment of IST symptoms using β-blockers or calcium channel-blockers are often noneffective or not well tolerated. Ivabradine is a new heart rate (HR)-decreasing agent inhibiting sinus node If current. The purpose of the study was to evaluate the efficacy and safety of ivabradine in patients with persistent and β-blocker-resistant IST after successful radiofrequency (RF) ablation of atrioventricular node slow pathway. We enrolled 14 patients (42 ± 11 years; 10 women) affected by IST after RF ablation. Holter monitoring, treadmill stress test, and IST symptoms assessment were performed at baseline and after first, and second month of the study. We observed significant reduction of mean resting HR after 30 and 60 days of ivabradine treatment compared to baseline (P < 0.001). 24-hour Holter monitoring showed a significant reduction of mean HR and mean HR during daily activity (P < 0.001). The study revealed significant improvement in exercise capacity during treadmill exercise test on ivabradine therapy (P < 0.001). Significantly lower incidence of IST-related symptoms were registered after administration of If current inhibitor. After 2 months of treatment no patients reported severe complaints assessed by means of European Heart Rhythm Association score. We did not observe severe side effects during therapy. Ivabradine is an effective treatment option to reduce HR and symptoms in patients with IST after RF ablation of atrioventricular node slow pathway. The therapy with ivabradine is well tolerated even with maximum daily dose.

Asystole induced by radiofrequency catheter ablation of slow pathway

Radiofrequency (RF) catheter ablation is a treatment of choice widely used for a variety of supraventricular tachycardia. Transient sinus and atrioventricular (AV) node dysfunctions may occur during RF application to sites remote from the sinus and AV nodes, but they generally resolve quickly after cessation of RF current. We present a case of two episodes of asystole in a 43-year-old man induced by RF catheter ablation of an AV nodal slow pathway. A Bezold–Jarisch-like reflex, direct stimulation of parasympathetic fibers traveling to the sinus and AV nodes, RF-induced myocardial injury or pain could be responsible for this situation.

Newly created animal model of human postoperative junctional ectopic tachycardia

Junctional ectopic tachycardia complicates the postoperative recovery from open heart surgery in children. The reported risk factors include younger age, prolonged cardiopulmonary bypass times, and administration of inotropic agents. Junctional ectopic tachycardia occurs early after open heart surgery, in the setting of relative postoperative sinus node dysfunction, and exhibits QRS morphology consistent with an origin from the atrioventricular node or proximal conduction system. Our goal was to develop a reproducible animal model for postoperative junctional ectopic tachycardia. Eleven pigs, aged 2 to 4 months, underwent open heart surgery after induction of general anesthesia. Electrodes were sewn to the left atrium and right ventricle. Sinus node dysfunction was created using clamp crushing without or with radiofrequency ablation (successful in 1 of 5 pigs) or sinus node removal (successful in 4 of 4). After prolonged cardiopulmonary bypass (>120 minutes) alone and with isoproterenol infusion, no spontaneous junctional ectopic tachycardia developed. Junctional ectopic tachycardia or fascicular tachycardia could be initiated after either slow atrioventricular nodal pathway ablation and/or digoxin administration. Junctional ectopic tachycardia occurred in 8 of 9 pigs (mean ventricular rate, 171 ± 32 bpm), and fascicular tachycardia occurred in 9 of 9 pigs (mean ventricular rate, 187 ± 39 bpm). His and right bundle recordings confirmed the conduction system origin. Experimental junctional ectopic tachycardia or fascicular tachycardia can occur in the intraoperative setting of sinus node dysfunction, prolonged cardiopulmonary bypass, and enhanced conduction system automaticity. Conduction system automaticity occurred after either physical injury (ablation or tricuspid valve stretch) or measures to augment the transient inward current of the conduction system (isoproterenol and digoxin). This animal model can serve as the basis to assess new treatments of postoperative junctional ectopic tachycardia.

Dual Atrioventricular Nodal Nonreentrant Tachycardia with Alternating 1:1 and 1:2 AV Conduction: Mechanistic Hypotheses and Total Suppression Using Right Atrial Pacing

Dual atrioventricular (AV) nodal nonreentrant tachycardia is an uncommon arrhythmia with several pattern types. The primary therapy is ablation of the slow AV nodal pathway. A rare pattern type demonstrates alternating 1:2 and 1:1 AV ratios with longer PR intervals during 1:1 conduction. We report the second intracardiac study of this variant and the first case of using right atrial pacing as the ultimate therapy for any pattern type.

Familial Occurrence of Atrioventricular Nodal Reentrant Tachycardia in a Mother and Her Son

Atrioventricular nodal reentrant tachycardia (AVNRT), caused by a reentry circuit involving fast and slow atrioventricular nodal pathways, is one of the most common types of paroxysmal supraventricular tachycardias. While familial Wolff-Parkinson-White syndrome has been well recognized, familial AVNRT has been rarely reported. We report a familial occurrence of AVNRT in a mother and her son, who were symptomatic and successfully treated with radiofrequency catheter ablation of slow pathway.

The study of the relation between different end points of slow atrioventricular nodal pathway ablation and clinical efficiency in patients with atrioventricular nodal reentrant tachycardia (slow-fast kind)

ObjectiveThe study of the Relation between different end points of slow atrioventricular nodal pathway ablation and clinical efficiency in patients with atrioventricular nodal reentrant tachycardia.Methods350 patients with atrioventricular nodal re-entrant...