Atypical Atrioventricular Nodal Reentrant Tachycardia Research Articles

Is the conventional deployment of electrode catheters appropriate to diagnose the circuit of atypical atrioventricular nodal reentrant tachycardia? -New insights into the retrograde slow pathways-

Abstract During atypical atrioventricular nodal reentrant tachycardia (AVNRT), the earliest atrial activation site following retrograde slow pathway conduction is either at the exit of the left inferior extension (LIE) in the coronary sinus (CS) or that of the right inferior extension (RIE) on the tricuspid annulus (TA). In an EP study, LIE can be detected by the CS catheter, but absence of catheters at the RIE can lead to it being missed. Aim To evaluate the electrophysiological characteristics of the retrograde slow pathway. Methods We assessed patients with atypical AVNRT using electro-anatomical 3D mapping. Results Among 14 patients (9 females, age 59±17), with a total of 18 atypical AVNRTs (15 fast/slow and 3 slow/slow), 4 patients had LIE, 6 had RIE, and 4 had both. The LIE exits were inside the CS, while those of RIE were on the posterior TA. During AVNRT or ventricular pacing, the local electrogram of RIE preceded that of the CS ostium and HBE by 24±12 and 34±12 ms respectively. Examination of activation times at the CS ostium and HBE showed that the nearer to the exit of RIE they were, the earlier they were excited. Conclusion The retrograde slow pathway of atypical AVNRT can have an exit site at the LIE or RIE, or both. Accurate identification of inferior extensions of the AV node is critical for diagnosis and treatment. We recommend placing a catheter on the posterior TA or 3D mapping the area for RIE exit detection in atypical AVNRT patients.

Cannon A wave validation as a diagnostic tool in paroxysmal supraventricular tachycardias.

The presence of cannon A waves, the so called "frog sign", has traditionally been considered diagnostic of atrioventricular nodal re-entrant tachycardia (AVNRT). Nevertheless, it has never been systematically evaluated. The aim of this study is to assess the independent diagnostic utility of cannon A waves in the differential diagnosis of supraventricular tachycardias (SVTs). We prospectively included 100 patients who underwent an electrophysiology (EP) study for SVT. The right jugular venous pulse was recorded during the study. In 61 patients, invasive central venous pressure (CVP) was registered as well. CVP increase is thought to be related with the timing between atria and ventricle depolarization; two groups were prespecified, the short VA interval tachycardias (including typical AVNRT and atrioventricular reciprocating tachycardia (AVRT) mediated by a septal accessory pathway) and the long VA interval tachycardias (including atypical AVNRT and AVRT mediated by a left free wall accessory pathway). The relationship between cannon A waves and AVNRT did not reach the statistical significance (OR: 3.01; p=.058); On the other hand, it was clearly associated with the final diagnosis of a short VA interval tachycardia (OR: 10.21; p<.001). CVP increase showed an inversely proportional relationship with the VA interval during tachycardia (b=-.020; p<.001). CVP increase was larger in cases of AVNRT (4.0mmHg vs. 1.2mmHg; p<.001) and short VA interval tachycardias (3.9mmHg vs. 1.2mmHg; p<.001). The presence of cannon A waves is associated with the final diagnosis of short VA interval tachycardias.

Local VA index for the differential diagnosis of supraventricular tachycardia

BackgroundDifferentiating between atypical atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia utilizing a septal accessory pathway is a complex challenge. ObjectiveThe purpose of this study was to describe the "local VA index," a straightforward method based on signals from the coronary sinus catheter, to distinguish between these arrhythmias during tachycardia and entrainment. The ventriculoatrial (VA) interval on the coronary sinus catheter is measured during tachycardia and entrainment, at the site of earliest atrial activity. The difference between these 2 situations defines the “local VA index.” We also propose a mechanism to clarify the limitations of historical pacing maneuvers, such as postpacing interval minus tachycardia cycle length (PPI-TCL) and stimulus–atrial interval minus ventriculoatrial interval (SA-VA), by examining nodal decrement and intraventricular conduction delay. MethodsIn a retrospective study of 75 patients referred for supraventricular tachycardia evaluation, 37 were diagnosed with atrioventricular reentrant tachycardia (AVRT) with orthodromic reciprocating tachycardia, and 38 with AVNRT (27 typical, 11 atypical). ResultsIn comparison to AVRT patients, AVNRT patients exhibited longer PPI-TCL (176 ± 47 ms vs 113 ± 42 ms; P <.01) and SA-VA (138 ± 47 ms vs 64 ± 28 ms; P <.01). The AVRT group had mean local VA index of –1 ± 13 ms, whereas the AVNRT group had a significantly longer index of 91 ± 46 ms (P <.01). An optimal threshold for differentiation was a local VA index of 40 ms. Importantly, there was no significant correlation between pacing cycle length and nodal decrement as well as intraventricular delay related to pathway location. This interindividual variability might explain misleading interpretations of PPI-TCL and SA-VA. ConclusionThis novel approach is advantageous because of its simplicity and effectiveness, requiring only 2 diagnostic catheters. A local VA interval difference <40 ms provides a clear distinction for AVRT.

Clinical profile and electrophysiological characteristics of atypical atrioventricular nodal reentrant tachycardia: A decade's experience

ObjectiveTo assess the clinical features and inducibility characteristics of atypical atrioventricular nodal reentrant tachycardia (AVNRT) and compare it with typical AVNRT. BackgroundAVNRT is the commonest form of paroxysmal supraventricular tachycardia. The mechanism of AVNRT is very varied. Several classification systems evolved with better understanding but a simplified approach of classification into typical and atypical AVNRT is justifiable and clinically more relevant. In our study, we have assessed the epidemiological profile of atypical AVNRT in a single institute over 10 years and analysed pertinent electrophysiological characteristics. MethodIn this retrospective observational single center study we analysed data of all AVNRT cases from January 2011 to June 2021. In our study we classified atypical AVNRT and typical AVNRT based on the HA interval; HA≤70 ms in the His bundle region during tachycardia was considered as typical AVNRT. Other parameters were also analysed during tachycardia, such as: induction by atrial or ventricular pacing, AH/HA ratio, tachycardia cycle length and site of the earliest atrial activation. The demographic profile of the patients were also compared between 2 groups. ResultsAtypical AVNRT was found in 75/1431 patients (5.2%) of all cases of AVNRT. The age of patients with atypical AVNRT was 52.4 ± 15.2 years (range 9–82 years) while that for typical AVNRT it was 48.2 ± 15.7 years (2–89 years), p = 0.023. There was no gender difference. Atypical AVNRT was induced by only ventricular extrastimuli (VES) in 17/75 (22.6%) while in typical AVNRT this was seen in only 12/1356 patients (0.9%, p < 0.001). Induction of atypical AVNRT was seen by both atrial extrastimuli (AES) and VES in 17/75 patients (22.6%) while in typical AVNRT this was seen in 64/1356 patients (4.8%, p < 0.001). Atypical AVNRT was induced by only AES in 40/75 patients (53.3%) while in typical AVNRT this was seen in 1280/1356 patients (94.3%, p < 0.001). An AH >200 ms during tachycardia was seen in all patients with typical AVNRT and in only 31/75 patients (41.3%) of atypical AVNRT (p < 0.00001). An interesting finding in atypical AVNRT was the earliest atrial activation at the His bundle region in 10/75 (13.3%) patients. ConclusionAtypical AVNRT prevalence depends on the way it is classified; this was 5.2% of all AVNRT cases in our study. Typical AVNRT was seen more frequently in comparatively younger age group and was more often induced by AES. Atypical AVNRT was much more commonly induced by only VES compared to typical AVNRT. It was not so unusual in atypical AVNRT to find the earliest atrial activation in the His bundle region.

Paradigm Shift for Catheter Ablation of Atypical Atrioventricular Nodal Re-Entrant Tachycardia: 3-Dimensional Mapping–Based Ablation

BackgroundIn current practice, the ablation target of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway region. ObjectivesThe purposes of this study were to map the site of earliest retrograde atrial activation using electroanatomic three-dimensional mapping during atypical AVNRT and to evaluate successful ablation sites. MethodsA total of 42 patients with a total of 49 AVNRTs (slow/fast: 30; fast/slow: 15; slow/slow: 4) underwent electrophysiological study and ablation. Among them there were 14 patients (10 women; 60 ± 19 years of age) in whom 19 atypical AVNRT (fast/slow: 15; slow/slow: 4) were induced. ResultsThe intracardiac electrocardiograms or three-dimensional mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension [LIE]), 3 solely in the right postero-septal tricuspid annulus (TA; right inferior extension [RIE]), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14 ± 6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o’clock in the left anterior oblique projection). Ablation targeting these exits or conventional slow pathway succeeded in long-term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications. ConclusionsCatheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.

Junctional rhythm during cryoablation for typical atrioventricular nodal reentrant tachycardia.

Cryoablation is being used as an alternative to radiofrequency (RF) ablation for atrioventricular nodal reentrant tachycardia (AVNRT) owing to the lower risk of atrioventricular block (AVB) compared to RF ablation. Junctional rhythm often occurs during successful application of RF ablation for AVNRT. In contrast, junctional rhythm has rarely been reported to occur during cryoablation. This retrospective study evaluated the characteristics of junctional rhythm during cryoablation for typical AVNRT. This retrospective study included 127 patients in whom successful cryoablation of typical AVNRT was performed. Patients diagnosed with atypical AVNRT were excluded. Junctional rhythm appeared during cryofreezing in 22 patients (17.3%). These junctional rhythms appeared due to cryofreezing at the successful site in the early phase within 15 s of commencement of cooling. Transient complete AVB was observed in 10 of 127 patients (7.9%), and it was noted that atrioventricular conduction improved immediately after cooling was stopped in these 10 patients. No junctional rhythm was observed before the appearance of AVB. No recurrence of tachycardia was confirmed in patients in whom junctional rhythm occurred by cryofreezing at the successful site. Occurrence of junctional rhythms during cryoablation is not so rare and can be considered a criterion for successful cryofreezing. Furthermore, junctional rhythm may be associated with low risk of recurrent tachycardia.

PO-05-146 AN UNUSUAL ATRIOVENTRICULAR REENTRY TACHYCARDIA: SUCCESSFUL ABLATION OF NOVEL SLOW PATHWAY AT SUPERIOR SEPTAL PERIMITRAL LEFT ATRIUM

Atrioventricular nodal reentrant tachycardia (AVNRT) is a common supraventricular tachycardia (SVT), treated with catheter ablation of slow pathway. The right and left inferior slow pathway (SP) extensions of the AV node are widely recognized, but other SPs are very rare. We present a case of atypical AVNRT that was successfully ablated at the superior septal perimitral left atrium. N/A A 75-year-old man with history of coronary artery disease status post coronary artery bypass grafting and recurrent episodes of symptomatic SVT despite diltiazem and metoprolol presented for catheter ablation. Mid RP SVT (cycle length, CL 350 ms) with concentric atrial activation was inducible with atrial and ventricular extrastimulation. Synchronized premature ventricular complexes and ventricular entrainment excluded AV reentry. Very late coupled premature atrial complex from coronary sinus (CS) delivered synchronous to septal A activation delayed next A and reset SVT indicating AVNRT and excluding ectopic junctional (JT) or atrial tachycardia (AT). Further, AH interval during SVT was much longer than AH with atrial pacing at same CL excluding AT. We concluded mechanism to be atypical AVNRT. On activation mapping of right atrium, earliest A was recorded in the fast pathway region, earlier than locations of right and left slow pathways in the triangle of Koch and CS respectively. Radiofrequency ablation lesions anatomically targeting both slow pathways were delivered at base of triangle of Koch and inside CS without affecting SVT. High density activation maps of both right and left atria were created during SVT using Orion basket catheter and Rhythmia (Boston Scientific) mapping system. Earliest A was recorded in the superior septal perimitral left atrium, superior to the location of His bundle electrogram, and anatomically adjacent to aortic sinuses of Valsalva (not mapped). We concluded this to be an unusual left superior extension of the AV node. Radiofrequency ablation lesion using IntellaNav MiFi catheter at this site promptly terminated SVT. Consolidation lesions were delivered and anchored to the mitral annulus. The tachycardia was no longer inducible on programmed electrical stimulation despite isoproterenol. The patient has remained symptom free for 6 months since ablation. With activation mapping we identified the retrograde slow pathway participating in an unusual atypical AVNRT at superior septal perimitral left atrium.

Atrioventricular Ring Tachycardias: Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia and Atrial Tachycardia Share a Common Arrhythmogenic Substrate—A Unifying Proposal

Our understanding of the variants of slow pathway (SP) and associated atypical atrioventricular (AV) nodal reentrant tachycardia (NRT) is still growing. We have identified variants extending outside Koch’s triangle along the tricuspid annulus, including superior, superoanterior and inferolateral right atrial SP and associated atypical, fast-slow AVNRT. We review the history of each variant, their electrophysiological characteristics and related atypical AVNRT, and their treatment by catheter ablation. We focused our efforts on organizing the published information, as well as some unpublished, reliable data, and show the pitfalls of electrophysiological observations, along with keys to the diagnosis of atypical AVNRT. The superior-type of fast-slow AVNRT mimics adenosine-sensitive atrial tachycardia originating near the AV node and can be successfully treated by ablation of a superior SP form the right side of the perihisian region or from the non-coronary sinus of Valsalva. Fast-slow AVNRT using a superoanterior or inferolateral right atrial SP also mimics atrial tachycardia originating from the tricuspid annulus. We summarize the similarities among these variants of SP, and the origin of the atrial tachycardias, including their anatomical distributions and electrophysiological and pharmacological characteristics. Moreover, based on recent basic research reporting the presence of node-like AV ring tissue encircling the annuli in adult hearts, we propose the term “AV ring tachycardia” to designate the tachycardias that share the AV ring tissue as a common arrhythmogenic substrate. This review should help the readers recognize rare types of SP variants and associated AVNRT, and diagnose and cure these complex tachycardias. We hope, with this proposal of a unified tachycardia designation, to open a new chapter in clinical electrophysiology.

Electrophysiological characteristics and catheter ablation of atypical fast-slow atrioventricular nodal reentrant tachycardia using an inferolateral left atrial slow pathway

Abstract Background Understandings of subtypes of atypical atrioventricular nodal reentrant tachycardia (AVNRT) using variants of slow pathway (SP) are still growing. Inferolateral (inf-lat-) left atrial (LA) SP is a rare variant extending into an inf-lat-LA along the mitral annulus (MA). Purpose To characterize an unknown subtype of atypical fast-slow (F/S-) AVNRT using an inf-lat-LA-SP as a retrograde limb (inf-lat-LA-F/S-AVNRT). Methods This Japanese multicenter retrospective study enrolled 4 patients of inf-lat-LA-F/S-AVNRT that was characterized by the earliest site of atrial activation during tachycardia (EAA) between 3 and 6 o'clock along the MA. The diagnosis was made by an exclusion of AV reentrant tachycardia (AVRT) and atrial tachycardia (AT) according to the standard criteria and was confirmed by successful elimination of tachycardia and the inf-lat-LA-SP. Results Surface ECG during tachycardia revealed long RP appearance except one who had short RP due to a short conduction time across the inf-lat-LA-SP. During tachycardia, far-field LA activation preceding near-field activation of coronary sinus (CS) musculature was visible in the CS recording in 2. Retrograde conduction via the inf-lat-LA-SP with a decremental delay was consistently reproducible with ventricular stimulation in 2, 1 of whom had double atrial response, while it was always masked by the presence of a retrograde conduction via the fast pathway in 1 and a retrograde block at the lower common pathway in 1. An injection of a small dose of ATP transiently interrupted a retrograde conduction over the inf-lat-LA-SP, suggesting its ATP-sensitivity. Exclusion of AVRT was made by no resetting of tachycardia with left ventricular extrastimulus in 2 and VA dissociation during overdrive pacing of tachycardia in remaining 2. Exclusion of AT was made by V-A-V response after ventricular entrainment in 1 and termination without atrial capture by ventricular pacing in 2. Ablation of the right-sided SP was unsuccessful to eliminate the tachycardia, but ablation at or near the EAA by transseptal approach was successful to cure the tachycardia, associated with an elimination of a retrograde conduction over the inf-lat-LA-SP following a development of an accelerated junction rhythm in all. Low-frequency potentials preceding local atrial activation, consistent with a retrograde activation via the inf-lat-LA-SP were detected along the MA medial to the EAA in 1. Conclusions Differential diagnosis of tachycardia with the EAA in the inf-lat-LA and especially long RP appearance should include inf-lat-LA-F/S-AVNRT. Presumed arrhythmogenic substrate of the inf-lat-LA-SP seemed to be consistent with the remnant of embryogenic AV ring tissue in the electropharmacological and locational characteristics. Successful elimination of this AVNRT can be obtained by ablation of the inf-lat-LA-SP, but not of the right-sided SP. Funding Acknowledgement Type of funding sources: None.

Variability of the VA interval at tachycardia induction: a simple method to differentiate orthodromic reciprocating tachycardia from atypical atrioventricular nodal reentrant tachycardia.

The differential diagnosis between orthodromic atrioventricular reentry tachycardia (AVRT) and atypical AV nodal reentrant tachycardia (aAVNRT) is sometimes challenging. We hypothesize that aAVNRTs have more variability in the retrograde conduction time at tachycardia onset than AVRTs. We aimed to assess the variability in retrograde conduction time at tachycardia onset in AVRT and aAVNRT and to propose a new diagnostic tool to differentiate these two arrhythmia mechanisms. We measured the VA interval of the first beats after tachycardia induction until it stabilized. The difference between the maximum and minimum VA intervals (∆VA) and the number of beats needed for the VA interval to stabilize was analyzed. Atrial tachycardias were excluded. A total of 107 patients with aAVNRT (n = 37) or AVRT (n = 64) were included. Six additional patients with decremental accessory pathway-mediated tachycardia (DAPT) were analyzed separately. All aAVNRTs had VA interval variability. The median ∆VA was 0 (0 - 5) ms in AVRTs vs 40 (21 - 55) ms in aAVNRTs (p < 0.001). The VA interval stabilized significantly earlier in AVRTs (median 1.5 [1 - 3] beats) than in aAVNRTs (5 [4 - 7] beats; p < 0.001). A ∆VA < 10ms accurately differentiated AVRT from aAVNRT with 100% of sensitivity, specificity, and positive and negative predictive values. The stabilization of the VA interval at < 3 beats of the tachycardia onset identified AVRT with sensitivity, specificity, and positive and negative predictive values of 64.1%, 94.6%, 95.3%, and 60.3%, respectively. A ∆VA < 20ms yielded good diagnostic accuracy for DAPT. A ∆VA < 10ms is a simple and useful criterion that accurately distinguished AVRT from atypical AVNRT. Central panel: Scatter plot showing individual values of ∆VA in atypical AVNRT and AVRT. Left panel: induction of atypical AVNRT. The VA interval stabilizes at the 5th beat and the ∆VA is 62ms (maximum VA interval: 172ms - minimum VA interval: 110ms). Right panel: induction of AVRT. The tachycardia has a fixed VA interval from the first beat. ∆VA is 0ms.

Radiofrequency Catheter Ablation for Pediatric Atrioventricular Nodal Reentrant Tachycardia: Impact of Age on Procedural Methods and Durable Success.

BackgroundCatheter‐based slow‐pathway modification (SPM) is the treatment of choice for symptomatic atrioventricular nodal reentrant tachycardia (AVNRT). We sought to investigate the interactions between patient age and procedural outcomes in pediatric patients undergoing catheter‐based SPM for AVNRT.Methods and ResultsA retrospective cohort study was performed, including consecutive patients undergoing acutely successful SPM for AVNRT from 2008 to 2017. Those with congenital heart disease, cardiomyopathy, and accessory pathways were excluded. Patients were stratified by age quartile at time of SPM. The primary outcome was AVNRT recurrence. A total of 512 patients underwent successful SPM for AVNRT. Age quartile 1 had 129 patients with a median age and weight of 8.9 years and 30.6 kg, respectively. Radiofrequency energy was used in 98% of cases. Follow‐up was available in 447 (87%) patients with a median duration of 0.8 years (interquartile range, 0.2–2.5 years). AVNRT recurred in 22 patients. Multivariable Cox proportional hazard modeling identified atypical AVNRT (hazard ratio [HR], 5.83; 95% CI, 2.01–16.96; P=0.001), dual atrioventricular nodal only (HR, 4.09; 95% CI, 1.39–12.02; P=0.011), total radiofrequency lesions (HR, 1.06 per lesion; 95% CI, 1.01–1.12; P=0.032), and the use of a long sheath (HR, 3.52; 95% CI, 1.23–10.03; P=0.010) as predictors of AVNRT recurrence; quartile 1 patients were not at higher risk of recurrence (HR, 0.45; 95% CI, 0.10–1.97; P=0.29). Complete heart block requiring permanent pacing occurred in one quartile 2 patient at 14.9 years of age.ConclusionsPediatric AVNRT can be treated with radiofrequency‐SPM with high procedural efficacy and minimal risk of complications, including heart block. Atypical AVNRT and dual atrioventricular nodal physiology without inducible tachycardia remain challenging substrates.

Discrimination of atypical atrioventricular nodal reentrant tachycardia from atrial tachycardia by the V-A-A-V response.

The electrophysiological discrimination between fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (NRT) and atrial tachycardia (AT) originating from the interatrial septum remains challenging. While a V-A-A-V response may occur immediately after ventricular induction or entrainment of either tachycardia, the electrophysiological dissimilarities in that response between the two tachycardias remain unclear. The purpose of this study was to identify a diagnostic indicator discriminating F/S-AVNRT from AT by examining the difference in the V-A-A-V response between the two tachycardias. This retrospective study included 17 patients with F/S-AVNRT [seven with common-form F/S-AVNRT using a typical slow pathway (SP) and 10 with superior type F/S-AVNRT using a superior SP] and 10 patients with reentrant AT. All 27 patients presented with long RP supraventricular tachycardia and an initial V-A-A-V response upon ventricular induction or entrainment. The V-A-A-V response in patients with F/S-AVNRT was due to dual atrial responses. We measured the interval between the first (A1) and second atrial electrogram (A2) of V-A-A-V and calculated ΔAA by subtracting A1-A2 from the tachycardia cycle length. V-A-A-V responses were observed most often upon ventricular induction of F/S-AVNRT (6 ± 5 times) as well as AT (6 ± 6 times; p=.87). The V-A-A-V response upon ventricular entrainment was observed in a single patient with F/S-AVNRT versus 10 all patients with AT (p<.001). ΔAA ranged between -80 and 228ms in F/S-AVNRT and between -184 and 26ms in AT. A ΔAA>26ms predicted a diagnosis of F/S-AVNRT with a 76% sensitivity and 100% specificity, while a ΔAA<-80ms predicted a diagnosis of AT with a 50% sensitivity and 100% specificity. ΔAA is a useful, confirmatory, diagnostic indicator of F/S-AVNRT versus AT associated with the V-A-A-V response.

Target of atypical atrioventricular nodal reentrant tachycardia in congenitally corrected transposition of great vessels.

Target of atypical atrioventricular nodal reentrant tachycardia in congenitally corrected transposition of great vessels.

Abstract 10194: Pacing Site- and Rate-Dependent Shortening of Retrograde Conduction Time Over the Slow Pathway After Atrial Entrainment of Fast-Slow Atrioventricular Nodal Reentrant Tachycardia

Introduction: The entrainment rule by which the site of entrainment has no effect on the orthodromic conduction time across the reentry circuit immediately after cessation of pacing has not been unequivocally verified in atypical atrioventricular nodal reentrant tachycardia (AVNRT). We have recently observed a unique electrophysiological response upon atrial induction of fast-slow (F/S-) AVNRT, characterized by a shortening of the retrograde conduction time across the slow pathway (SP) (retro-SP-time). Hypothesis: Atrial entrainment pacing (EP) of a) the common-type (com-) F/S-AVNRT using a typical SP, or b) the superior-type (sup-) F/S-AVNRT using a superior SP, both might modify the retro-SP-time immediately after termination of EP. Methods: In 16 patients of com-F/S-AVNRT and 11 patients of sup-F/S-AVNRT in whom successful EP from the high right atrium (EP-HRA) and the proximal coronary sinus (EP-CS) was obtained at 2±2 rates, we evaluated the difference in the His-atrial (HA) interval measured immediately after cessation of each EP attempt (HA difference) between EP-HRA and EP-CS (HA[1]-HRA and HA[1]-CS, respectively) and also measured atrial-His and HA intervals in the 1st and 2nd cycles immediately after the EP, and during tachycardia stabilized. Results: &gt;20 ms HA difference, defined as an atypical difference, at ≥1 rates of EP was observed in 16 patients (56%), including 7 with com- and 9 with sup-F/S-AVNRT. Irrespective of the EP rate, the atypical response of com-F/S-AVNRT was always due to a shorter HA[1]-CS than HA[1]-HRA, with a 39±22 ms HA difference, whereas the atypical response of sup-F/S-AVNRT was always due to a longer HA[1]-CS than HA[1]-HRA, with a 51±26 ms HA difference. Moreover, the atypical response disappeared within 2 cycles after the cessation of EP. The atypical difference, although its exact mechanism remains unclear, might attribute to a shortening of the retro-SP-time according to decremental properties of the SP with deeper antidromic penetration during EP provoked depending on the site and rate of pacing. Conclusions: We have identified a little-known pacing site- and pacing rate-dependent shortening of the retro-SP-time. This phenomenon may affect an interpretation of post-pacing interval after EP of F/S-AVNRT.

Change in VA interval by a single atrial premature depolarization - What is the mechanism?

A long VA tachycardia during a typical atrioventricular nodal reentrant tachycardia (AVNRT) can be a concomitant atypical AVNRT, atrial tachycardia or rarely atrio-ventricular reentrant tachycardia (AVRT). There are reported associations of AVNRT with other tachycardia substrates. Maneuvers are useful for differentiating the mechanism of the second tachycardia. Atrial tachycardia (AT) is one common association. When the AT originates from the lower triangle of Koch/near coronary sinus ostium, it can mimic slow-slow/fast-slow AVNRT. We encountered an interesting case where a longer VA tachycardia got reproducibly induced when a critically timed atrial premature depolarisation was delivered on typical AVNRT. It was proved to be an AT. A slow pathway modification in the lower TOK was successful to eliminate both the tachycardia substrate.

Fast-slow atrioventricular nodal reentrant tachycardia phenotype mimicking the slow-slow type

Abstract Background Fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is characterized by a short atrio-His (AH) interval and the earliest site of atrial activation (EAA) in the proximal coronary sinus (EAA-CS), while slow-slow (S/S-) AVNRT presents a long AH interval and EAA-CS. Those intracardiac appearances are initial indicators for making a diagnosis. Purpose To identify an unknown phenotype of F/S-AVNRT. Methods Among 46 consecutive patients with F/S-AVNRT, 6 patients (1 man, age 59±9) had an apparent but not typical (pseudo-) S/S-AVNRT during an electrophysiologic study. In 2 patients, pseudo-S/S-AVNRT was clinically documented. Results In all 6 patients, the diagnosis of F/S-AVNRT was made by an exclusion of atrial tachycardia with findings of 1) a V-A-V response following ventricular entrainment or 2) termination without atrial capture by ventricular pacing, and an exclusion of AV reentrant tachycardia with a ventriculoatrial dissociation during an initial (so-called QRS transition) zone of ventricular entrainment. An initial A-A-V activation sequence on atrial induction of F/S-AVNRT observed in 1 patient and Wenckebach-type AV block during ongoing F/S-AVNRT developing in 3 patients suggested the presence of the lower common pathway (LCP). Like the typical S/S-AVNRT, pseudo-S/S-AVNRT was induced with atrial stimulation after a jump in the AH interval or double ventricular response. However, in all patients, the pseudo-S/S-AVNRT transited to F/S-AVNRT following AV block in a single cycle and/or pseudo-S/S-AVNRT transited from spontaneously or triggered by atrial contractions. Importantly, on these transitions, the atrial cycle length (CL) and EAA-CS remained unchanged, that is, the atrial CL of S/S-AVNRT was almost identical to that of F/S-AVNRT, suggesting that the essential circuit of both tachycardias was identical. Actually, both tachycardias were cured by ablation at a single site in the traditional slow pathway (SP). Collectively, the pseudo-S/S-AVNRT was diagnosed as another phenotype of F/S-AVNRT accompanied by sustained antegrade conduction via another bystander (likely the left-sided or superior) SP breaking through the His bundle owing to the repetitive antegrade block at the LCP occurring by linking phenomenon, thus representing a long AH interval during the ongoing F/S-AVNRT. When the antegrade conduction is blocked at the bystander SP during the pseudo-S/S-AVNRT, releasing the linking phenomenon, the subsequent antegrade conduction reach the His-bundle via the fast pathway, thus returning to F/S-AVNRT. Conclusions An unknown, but not rare F/S-AVNRT phenotype exists that apparently mimics the typical S/S-AVNRT and is also an unknown subtype of apparent S/S-AVNRT. The presence of this pseudo-S/S-AVNRT suggests the limitation of classifying types of AVNRT based on AH and HA intervals during tachycardia. Understandings of this phenotype can advance a diagnosis of atypical AVNRT with multiple phenotypes. Funding Acknowledgement Type of funding sources: None.

Pacing site- and rate-dependent shortening of retrograde conduction time over the slow pathway after atrial entrainment of fast-slow atrioventricular nodal reentrant tachycardia.

IntroductionWe tested our hypothesis that atrial entrainment pacing (EP) of a) the common‐type (com‐) fast‐slow (F/S‐) atypical atrioventricular nodal reentrant tachycardia (AVNRT) using a typical slow pathway (SP), or b) the superior‐type (sup‐) F/S‐AVNRT using a superior SP, both modify the retrograde conduction time across the SP immediately after termination of EP (retro‐SP‐time).MethodsWe measured the difference in the His‐atrial interval (HA difference) immediately after cessation of EP, performed at 2 ± 2 rates from the high right atrium (HA[1]‐HRA) versus from the proximal coronary sinus (HA[1]‐CS) in 17 patients with com‐F/S‐AVNRT and 11 patients with sup‐F/S‐AVNRT. We also measured the atrial‐His and HA intervals of the first and second cycles immediately after cessation of EP and during stable tachycardia.ResultsUnequal responses, defined as a ≥ 20‐ms HA difference at ≥1 EP rates, were observed in 16 patients (57%), including 7 with com‐ and 9 with sup‐F/S‐AVNRT. Irrespective of the EP rate, all unequal responses of com‐F/S‐AVNRT were due to a shorter HA[1]‐CS than HA[1]‐HRA, with a mean 34 ± 11 ms HA difference, whereas all unequal responses of sup‐F/S‐AVNRT were due to a longer HA[1]‐CS than HA[1]‐HRA, with a mean 49 ± 25 ms HA difference. The unequal responses resolved within two cycles after the cessation of EP.ConclusionsWe have identified a little‐known pacing site‐ and pacing rate‐dependent shortening of the retro‐SP‐time.

B-PO05-133 ROLE OF ELECTROGRAMS RECORDED FROM THE MINI ELECTRODES IN CATHETER ABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA

Analysis of electrograms recorded from mini electrodes (MEs) (IntellaTip MiFi, Boston Scientific) has not been reported. We evaluated the additional value of MEs during ablation of atrioventricular nodal reentrant tachycardia (AVNRT). Consecutive patients with AVNRT who underwent slow pathway ablation using a MiFi catheter were included. A combined electroanatomic approach was used to identify the target site. During ablation, operators were blind to ME electrograms, and ME electrograms immediately before initiation of the first radiofrequency (RF) application were evaluated retrospectively. A total of 62 patients (47 ± 17 years, 46.8% male) with typical (n=58) and atypical (n=4) AVNRT were included. Slow pathway ablation or modification was achieved in all patients. Thirty-two patients (51.6%) showed accelerated junctional rhythm (JR) during the first RF application. Immediately before the first RF, atrial signals at the MEs were observed in 37 patients (59.7%). There was a significant association between presence of atrial signals in MEs and the occurrence of JR (OR 5.36, P=0.002). The positive and negative predictive values of the atrial signals in MEs for the JR induction during the first RF were 67.6% (25/37) and 72.0% (18/25), respectively. Amplitudes of atrial signals of the MEs were not different between patients with and without an inducible JR (0.20 ± 0.13 mV versus 0.14 ± 0.11 mV, P=0.18). Signals recorded from the MEs could be helpful in targeting the ablation point during slow pathway ablation. Ablation should be discouraged in regions with optimal bipolar electrograms not followed by adequate ME electrograms.

Spatial characterization of the tachycardia circuit of atrioventricular nodal re-entrant tachycardia.

The exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) remains elusive. To assess the location and dimensions of the AVNRT circuit. Both typical and atypical AVNRT were induced at electrophysiology study of 14 patients. We calculated the activation time of the fast and slow pathways, and consequently, the length of the slow pathway, by assuming an average conduction velocity of 0.04 mm/ms in the nodal area. The distance between the compact atrioventricular node and the slow pathway ablating electrode was measured on three-dimensionally reconstructed fluoroscopic images obtained in diastole and systole. We also measured the length of the histologically discrete right inferior nodal extension in 31 human hearts. The length of the slow pathway was calculated to be 10.8 ± 1.3 mm (range 8.2-12.8 mm). The distance from the node to the ablating electrode was measured in five patients 17.0 ± 1.6 mm (range 14.9-19.2 mm) and was consistently longer than the estimated length of the slow pathway (P < 0.001). The length of the right nodal inferior extension in histologic specimens was 8.1 ± 2.3 mm (range 5.3-13.7 mm). There were no statistically significant differences between these values and the calculated slow pathway lengths. Successful ablation affects the tachycardia circuit without necessarily abolishing slow conduction, probably by interrupting the circuit at the septal isthmus.

P1010Electrophysiological characteristics of paroxysmal tachycardia in children with short PQ interval

Abstract Introduction It is well known that children with short PQ interval can have different types paroxysmal tachycardia (PT). Combination of short PQ interval with PT is called Lown-Ganong-Levine (LGL) syndrome. We have hypothesized that in children with short PQ interval electrophysiological types of PT do not correlate with shortening of PQ interval. Purpose The aim of the study was to assess the PT types based on results of the electrophysiological studies and radiofrequencycatheter ablation (RFA), and to estimate the AV conduction parameters and their dynamic changes before and after the procedure. Materials and methods of research: 55 children with supraventricular tachycardia (SVT) and short PQ interval were examined. The examination included:ECG, 24-hour Holter monitor, transesophageal pacing study (TEPS), intracardiac electrophysiological study (EPS). 22 children underwent RFA procedure. During the period of the study 55 children had 111 TEPS and 28 EPS studies. Results 21 (38,2%) children had orthodromic AV reentrant tachycardia with accessory pathway (AVRT), 27 (49,1%) had typical (slow-fast) AV nodal reentrant tachycardia (AVNRT), 2 (3,6%) had atypical AVNRT, 1 (1,8%) had combination of typical and atypical AVNRT, 1 (1,8%) had atrial ectopic tachycardia combined with atypical AVNRT, 4 (7,3%) had spontaneous atrial fibrillation or atrial flutter, 3 (5,4%) had combination with typical AVNRT and 1 child (1,8%) had AVRT. PQ interval measured 107,2 ms (83–120ms). 22 (40%) children underwent RFA-13 children with typical AVNRT, 9 with AVRT. In children with AVNRT tachycardia cycle length was 229–425 ms (309,8±67,6ms). Primary RFA was effective in 10 (76,9%) children. The AVNRT recurrence was found in 3 (13,6%) cases after 7,2±4,3 month from the time of procedure. After slow pathway ablation PQ interval length didn't change (107,1±9,1ms compared to 108,2±7,1ms; p=0,2). No change occurred with the maximal rate of 1:1 conduction through AV node (187,8±14,8 imp/min compared to187±12,5 imp/min; p=0,2). Effective refractory period of AV node (AVNERP) increased by a small amount (288,9±14ms, compared to 266±42,7ms; p=0,06). 9 (40,9%) children underwent RFA of the accessory pathway (AP). In all of the cases there were concealed AP with the left-sided localization. AVRT cycle length was 259–382 ms (304,2±41,2ms). After RFA of concealed AP maximal rate of 1:1 conduction through AV node increased by a small amount (220±26,4 imp/min compared to 191,2±23,6 imp/min) and AVNERP decreased (256,7±25,2ms compared to 268,6±38,9ms; p=0,09).After RFA of AP PQ interval length didn't change (110±5,9ms compared to 110±5ms; p=0,1). Conclusion In children with short PQ interval PT was associated with dual physiology of AV connection or with concealed AP. After the successful RFA in children with AVNRT and AVRT there was no PQ interval normalization, which remained short in all examinations. Thus, short PQ- interval is a co-existing phenomenon in children with AVNRT and AVRT.