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Which parameters describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia?/Hangi parametreler ortak antriyoventrikuler nodal reenrant tasikardisi olan hastalarda basarili yavas yol RF ablasyon seyrinin elektrofizyolojik ozelliklerini tanimlar?

ABSTRACT

Which parameters describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia?

Objective: Atrioventricular nodal reentrant tachycardia (AVNRT) accounts for about 60% of the patients presenting with paroxysmal supraventricular tachycardia. The radiofrequency (RF) catheter ablation of the slow atrioventricular (AV) node pathway is the preferred therapeutic approach in patients with AV node reentrant tachycardia. The aim of our study was describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia.

Methods: The study design was a retrospective analysis involving fifty consecutive patients (18 males; mean age of 39+22 years) who underwent slow pathway ablation because of AVNRT.

Results: Slow junctional beats with a cycle length longer than 550 ms were observed in 39 patients (79%); the presence of rapid junctional beats with a cycle length less than 550 ms was showed in 5 patients (10%). Moreover, in 32 of 50 patients (65%) duration of atrial electrogram more than 40 ms was noticed. Analyzing data reported, we found the statistically significant presence of slow junctional beats (p<0.001) and atrial electrogram >40 ms (p<0.05) in successful RF ablation procedures.

Conclusion: In patients with AVNRT undergoing slow pathway ablation, the duration of atrial electrogram >40 ms and slow junctional beats with cycle length >550 ms during the application of RF energy describe the electrophysiological properties of successful slow pathway RF ablation.

Key words: Radiofrequency catheter ablation, atrioventricular nodal reentrant tachycardia, junctional ectopy, atrial electrogram, arrhythmia

OZET

Hangi parametreler ortak antriyoventrikuler nodal reenrant tasikardisi olan hastalarda basarili yavas yol RF ablasyon seyrinin elektrofizyolojik ozelliklerini tanimlar?

Amac: Antriyoventrikuler nodal reenrant tasikardi (AVNRT) paroksizmal supraventrikuler tasikardili hastalarin yaklasik %60'inda gorulur. Antriyoventrikuler (AV) reenrant tasikardili hastalarda AV dugumun yavas-yol radyofrekans (RF) kateter ablasyonu tercih edilen terapbtik bir yaklasimdir. Bu calismanin amaci, ortak AV nodal reenrant tasikardisi olan hastalarda basarili yavas-yol RF ablasyonun elektrofizyolojik ozelliklerini tanimlamakti.

Yontemler: Bu calismanin dizayni, AVNRT dolayisi ile yavaf-yol ablasyonu yapilan 50 ardisik hastayi iceren (18 erkek; ortalama 39 [+ or -] 22 yas) retrospektif bir analiz olarak tasarlanmistir.

Bulgular: Hastalarin 39'unda (%79) 550 ms'den daha fazla siklus uzunlugu olan yavas kavsak atimlari gozlendi; siklus uzunlugu 550 ms'den daha az olan hizli kavsak atimlarin varligi 5 hastada (%10) goruldu. Bulgularin analizinde, basarili RF ablasyon islemlerinde yavas kavsak atimlarinin varligi (p<0.001) ve atriyal elektrogramin >40 ms olmasi istatistik acidan onemli bulundu.

Sonuc: Yavas-yol ablasyonu yapilan AVRNT'li hastalarda RF enerji uygulama sirasinda atriyal elektrogram suresinin >40 ms ve siklus uzunlugu >50 ms olan yavas kavsak atimlari basarili yavas-yol RF ablasyonunun elektrofizyolojik ozellikleri olarak tanimlandi.

Anahtar kelimeler: Radyofrekans ablasyonu, antriyoventrikuler nodal reenrant tasikardi, kavsak atimi, atriyal elektrogram, aritmi

Introduction

Atrioventricular nodal reentrant tachycardia (AVNRT) accounts for about 60% of the patients presenting with paroxysmal supraventricular tachycardia (PSVT). It is the result of functional dissociation of atrioventricular (AV) nodal conduction into a so-called 'fast pathway' (FP) and 'slow pathway' (SP) (1). The fast pathway, connecting to the atrium in the anterior (superior) septum, forms the normal physiological conduction axis. Conduction over the slow pathway, connecting to the atrium in the posterior (inferior) septum, can be revealed when an atrial impulse is blocked in the fast pathway (which generally has a longer antegrade effective refractory period than the slow pathway) leading to a sudden prolongation of the AH interval. Therefore, the impulse reaches the ventricle through the slow way and runs through again, in retrograde direction, the rapid way, which in meanwhile, has recovered the excitability, creating the re-entry of the common junctional tachycardia (slow-fast).

The radiofrequency (RF) catheter ablation of the slow atrioventricular (AV) node pathway is the preferred therapeutic approach in patients with AV node reentrant tachycardia. The occurrence of junctional ectopy during perinodal RF energy delivery has been associated with the successful elimination of AVNRT (2). However, the electrophysiological features of different patterns of junctional rhythm (JR) and the importance of the multicomponent atrial electrogram are still unclear. The aim of our study is to describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia.

Methods

Study population

Fifty consecutive patients (18 males; mean age of 39 [+ or -] 22 years) who underwent successful slow pathway ablation for AVNRT were enrolled in the present retrospective study, after having given written informed consent. All patients enrolled had no structural heart disease. All antiarrhythmic drugs were discontinued at least five elimination half-lives before RF ablation procedure.

Electrophysiological study

All patients underwent electrophysiological study in non-sedated, fasting state. The atrial programmed stimulation was performed to define the nodal antegrade function, while the ventricular incremental stimulation was performed to value the nodal retrograde conduction. The programmed atrial stimulation was performed with a decrement of the coupling interval of atrial extrastimulus of 10 ms with sensed cycle or with stimulated cycles, the length of which were 600, 500, and 430 ms, until the achievement of the atrial refractoriness. An increment of the interval A1-H1 more than 50 ms, as a response to the decrement of 10 ms of the coupling interval A-A1, defined a discontinuation of nodal function curve and underlined a double way of anterograde atrioventricular conduction. This coupling interval, coinciding with the rapid way's refractory period, often coincided with the induction of the tachycardia. Analogous protocol was subsequently repeated after every ablative procedure.

Mapping and ablation

The method used for mapping and ablation has been described previously (3). Briefly, the triangle of Koch, extending from the coronary sinus ostium up to the His bundle region, is divided into three regions designated posterior, mid and anterior. The ablation catheter was placed along the tricuspid septal annulus down to the posterior aspect of the interatrial septum adjacent to the coronary sinus ostium (posterior zone), obtaining a recorded atrial/ventricular electrogram amplitude ratio of 0.1 to 0.5 with a multicomponent or a putative slow-pathway potential (4, 5). Radiofrequency energy was applied for 15 seconds after a target site was identified. If AV nodal reentrant tachycardia could not be eliminated after delivery of radiofrequency energy to the optimal sites, areas with different electrogram characteristics were chosen for ablation. The electrode catheter used for ablation had a thermistor embedded in the deflectable 4-mm-tip electrode. Radiofrequency energy was delivered from a generator (EPT-1000, EP Technologies, Inc. Sunnyvale, CA, USA), which supplied continuous, unmodulated sine-wave output at 500 kHz. Power, impedance, and temperature were measured, displayed and stored during each application of radiofrequency energy via an interface with a microcomputer. The maximum preset temperature was 55[degrees]C with a fixed power of 30 W, in every patient. Radiofrequency energy was terminated immediately in the event of impedance rise, displacement of the catheter, an increase in PR interval, occurrence of AV conduction block, accelerated JR with cycle length shorter than 450 ms or JR without ventriculoatrial conduction.

Electrophysiological parameters

During the delivery, we analyzed some important electrophysiological parameters:

1) Rapid junctional beats with a cycle length shorter than 550 ms;

2) Slow junctional beats with a cycle length longer than 550 ms;

3) Duration of atrial electrogram (ms).

Statistical analysis

Analyses were performed using the statistical package SPSS 11.0 software for Windows (Chicago, Illinois, USA). Statistical analysis was performed using unpaired Student's t-test for continuous variables. Data are presented as mean [+ or -] SD. Differences were considered to be significant at a p-value <0.05.

Results

Slow junctional beats with a cycle length longer than 550 ms (782 [+ or -] 127 ms) were observed in 39 patients (79%); the presence of rapid junctional beats with a cycle length less than 550 ms (340 [+ or -] 95 ms) was showed in 5 patients (10%). Six patients received successful ablation without having a JR. Moreover, in 32 of 50 patients (65%) a duration of atrial electrogram more than 40 ms (67 [+ or -] 5 ms) was noticed. This group also showed slow junctional beats with a cycle length longer than 550 ms. Analyzing data reported, we found the statistically significant presence of slow junctional beats (p<0.001) and the atrial electrogram >40 ms (p<0.05) in successful RF ablation procedures. There was no statistically significant presence of rapid junctional beats in successful RF ablation procedures. All results are shown in Table 1.

The population study was divided into two groups according to JR cycle length (Fig. 1) and atrial electrogram duration (Fig. 2). Junctional rhythm cycle length was significantly greater (p<0.005) in patients with rapid junctional beats as compared with patients with slow junctional beats. Atrial electrogram duration was significantly greater (p<0.01) in patients with atrial electrogram duration >40 ms as compared with patients with atrial electrogram duration <40 ms.

Discussion

Main findings

In this series of patients undergoing slow pathway ablation to eliminate AVNRT, a combined anatomic and electrogram mapping approach was used and a successful outcome was achieved in all patients. Slow junctional beats with a cycle length longer than 550 ms and atrial electrogram duration more than 40 ms were found to be parameters that describe the electrophysiological properties of successful slow pathway RF ablation.

Junctional beats

As reported in previous studies, junctional ectopy was found to be a sensitive, but non-specific marker of successful ablation (6). It appears in 75-92% of all AVNRT ablation attempts (5,7). McGavigan et al. (8). demonstrated that successful ablation of slow pathway seldom occurs in the absence of JR. Although JR almost invariably occurs with successful ablation, its lack of specificity and low positive predictive value questions the use of it as an endpoint in AVNRT ablation.

In the study of Lipscomb et al (9), fast junctional tachycardia with cycle lengths less than 350 ms seen during slow pathway modification was a predictor of conduction block, suggesting proximity to the compact node. Lee et al. (10) showed that there were different characteristics of the JR during slow pathway ablation of different types of AVNRT. Jentzer et al. (11) demonstrated that the quantification of junctional ectopy that occurs during delivery of RF energy is unlikely to be clinically useful in predicting whether a particular application was effective in eliminating the inducibility of AVNRT. Wagshal et al. (12) in their study compared different patterns of accelerated JR. Higher ablation temperature resulted in the most successful slow pathway ablation and was characterized by the least duration and few accelerated junctional rhythm beats. Higher temperature lesions simultaneously abolished all slow pathway activity as well as the focus of accelerated slow pathway potential. They concluded that this accelerated JR was specific for the slow pathway and was not a non-specific regional effect. According to lakobishvili et al. (13), the induction of a higher amount and longer duration of accelerated JR (with cycle length longer than 380 ms) results in more complete abolition of slow pathway conduction. In our study, the occurrence of slow junctional beats with a cycle length longer than 550 ms, during slow pathway RF ablation procedures was reported to be 79% and according to our experience, it could be considered a sensitive marker of successful slow pathway ablation in patients with common nodal reentrant tachycardia.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Local atrial electrogram

Although Jackman et al. (4) found a discrete slow-pathway potential at nearly all successful ablation sites, there have been several conflicting reports discussing the different prevalence's and definitions of these potentials (14-16). Haissaguerre et al (5) reported that during ablation of the slow pathway with discrete slow potentials used as a guide, 78% of 64 patients developed junctional rhythms. Kelly et al (17) demonstrated several independent predictors of successful ablation, including the occurrence of JR (93%) during ablation and the presence of a discrete slow-pathway potential (81%) in the successful ablation site. In our study, the occurrence of atrial electrogram duration more than 40 ms was reported to be 65%. Our data suggest that multicomponent atrial electrogram or slow-pathway potentials occur in the presence of slow JR.

Study limitations

This was a retrospective study and therefore we could not study several variables that would have further extended our understanding of the electrophysiological mechanisms in patients with or without JRs during slow-pathway ablation. The small number of patients could decrease the statistical power of our findings. No evaluation of the number of cumulative junctional beats was performed.

Conclusion

According to our findings, the duration of atrial electrogram more than 40 ms, recorded by the ablator catheter previously the ablation and the presence, during the delivery of slow junctional beats with a cycle length longer than 550 ms are parameters that describe the electrophysiological properties of successful slow pathway RF ablation. When a combined anatomic and electrogram approach to slow pathway ablation is used, an application of RF energy that is not accompanied by junctional ectopy is highly unlikely to have been successful in eliminating the inducibility of AVNRT. These data underline the necessity to dedicate more time for the "mapping" of the slow pathway, searching the multicomponent atrial electrogram or slow-pathway potentials. The efficiency of the procedure can be improved by performing short RF delivery-tests for the evaluation of the slow junctional beats presence, to confirm the right position of the ablation catheter on slow pathway. These delivery tests may render the slow pathway radiofrequency ablation more rapid, safe and with a smaller risk of relapse.

doi: 10.5152/akd.2010.036

Conflict of interest: None declared

Accepted/Kabul Tarihi: 25.01.2010

References

(1.) Heidbuchel H. How to ablate typical 'slow/fast' AV nodal reentry tachycardia. Europace 2000; 2:15-9.

(2.) Kalbfieisch SJ, Strickberger SA, Williamson B, Vorperian VR, Man C, Hummel JD, et al. Randomized comparison of anatomic and electrogram mapping approaches to ablation of the slow pathway of atrioventricular node reentrant tachycardia. J Am Coll Cardiol 1994; 23:716-23.

(3.) Tai CT, Chen SA, Chiang CE, Lee SH, Wen ZC, Chiou CW, et al. Complex electrophysiological characteristics in atrioventricular nodal reentrant tachycardia with continuous atrioventricular node function curves. Circulation 1997; 95: 2541-7.

(4.) Jackman WM, Beckman KJ, McClelland JH, Wang X, Friday KJ, Roman CA, et al. Treatment of supraventricular tachycardia due to atrioventricular nodal reentry by radiofrequency catheter ablation of slow-pathway conduction. N Engl J Med 1992; 327: 313-8.

(5.) Haissaguerre M, Gaita F, Fischer B, Commenges D, Montserrat P. d'Ivernois C, et al. Elimination of atrioventricular nodal reentrant tachycardia using discrete slow potentials to guide application of radiofrequency energy. Circulation 1992; 85: 2162-75.

(6.) Kay GN, Epstein AE, Dailey SM, Plumb VJ. Selective radiofrequency ablation of the slow pathway for the treatment of atrioventricular nodal reentrant tachycardia: evidence for involvement of perinodal myocardium within the reentrant circuit. Circulation 1992; 85:1675.

(7.) Kawaguchi N, Kobayashi Y, Miyauchi Y, Atarashi H, Takano T, Hayakawa H. Incidence and clinical significance of junctional rhythm remaining after termination of radiofrequency current delivery in patients with atrioventricular nodal reentrant tachycardia. Circ J 1999; 63: 865-72.

(8.) McGavigan AD, Rae AP Cobbe SM, Rankin AC. Junctional rhythm-a suitable surrogate endpoint in catheter ablation of atrioventricular nodal reentry tachycardia? Pacing Clin Electrophysiol 2005; 28:1052-4.

(9.) Lipscomb KJ, Zaidi AM, Fitzpatrick AR Slow pathway modification for atrioventricular node reentrant tachycardia: fast junctional tachycardia predicts adverse prognosis. Heart 2001; 85:44-7.

(10.) Lee SH, Tai CT, Lee PC, Chiang CE, Cheng JJ, Ueng KC, et al. Electrophysiological characteristics of junctional rhythm during ablation of slow pathway in different types of atrioventricular nodal reentrant tachycardia. Pacing Clin Electrophysiol 2005; 28:111-8.

(11.) Jentzer JH, Goyal R, Williamson BD, Man KC, Niebauer M, Daoud E, et al.Analysis of junctional ectopy during radiofrequency ablation of the slow pathway in patients with atrioventricular nodal tachycardia. Circulation 1994; 90: 2820-6.

(12.) Wagshal AB, Crystal E, Katz A. Patterns of accelerated junctional rhythm during slow pathway catheter ablation for atrioventricular nodal reentrant tachycardia: temperature dependence, prognostic value, and insights into the nature of the slow pathway. J Cardiovasc Electrophysiol 2000; 11: 244-54.

(13.) lakobishvili Z, Kusniec J, Shohat-Zabarsky R, Mazur A, Battler A, Strasberg B. Junctional rhythm quantity and duration during slow pathway radiofrequency ablation in patients with atrioventricular nodal re-entry supraventricular tachycardia. Europace 2006; 8:588-91.

(14.) McGuire MA, de Bakker JMT, Vermeulen JT, Opthof T, Becker AE, Janse MJ. Origin and significance of double potentials near the atrioventricular node: Correlation of extracellular potentials, intracellular potentials, and histology. Circulation 1994; 89: 2351-60.

(15.) Tebbenjohanns J, Pfeiffer D, Schumacher B, Manz M, Luderitz B. Impact of the local atrial electrogram in AV nodal reentrant tachycardia: ablation versus modification of the slow pathway. J Cardiovasc Electrophysiol 1995; 6: 245-51.

(16.) Kuo CT, Lauer MR, Young C, Hou CJ, Liem LB, Yu J, et al. Electrophysiologic significance of discrete slow potentials in dual atrioventricular node physiology: implications for selective radiofrequency ablation of slow pathway conduction. Am Heart J 1996; 131:490-8.

(17.) Kelly PA, Mann DE, Alder SW, Fuenzalida CE, Bailey WM, Ritter MJ. Predictors of successful radiofrequency ablation of extranodal slow pathways. Pacing Clin Electrophysiol 1994; 17:1143-8.

Address for Correspondence/Yazisma Adresi: Vincenzo Russo, Department of Cardiology, Monaldi Hospital, Via Leonardo Bianchi 80131 Naples, Italy Phone: +39 0817587482 E-mail: v.p.russo@libero.it

Gerardo Nigro, Vincenzo Russo, Anna Rago, Annabella de Chiara, Raffaele Chianese, Nadia Delia Cioppa * Raffaele Catabro

From Departments of Cardiology and * Anaesthesiology and Reanimation, Monaldi Hospital, Second University of Naples, Naples, Italy
Table 1. Electrophysiological parameters in the population study

Parameters                    Patients, n    Incidence, %

Slow junctional beats with        39             79
cycle length >550 ms
Rapid junctional beats with        5             10
cycle length <550 ms
Atrial electrogram                32             65
duration >40 ms
Atrial electrogram                18             35
duration <40 ms

Parameters                    Mean [+ or -] SD, ms   P *

Slow junctional beats with     782 [+ or -] 127      0.001
cycle length >550 ms
Rapid junctional beats with    340 [+ or -] 95
cycle length <550 ms
Atrial electrogram              67 [+ or -] 5        0.05
duration >40 ms
Atrial electrogram              31 [+ or -] 8
duration <40 ms

Data are presented as proportions/percentages and mean [+ or -] SD

* unpaired t test
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Title Annotation:Original Investigation/Ozgun Arastirma
Author:Nigro, Gerardo; Russo, Vincenzo; Rago, Anna; de Chiara, Annabella; Chianese, Raffaele; Cioppa, Nadia
Publication:The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi)
Date:Apr 1, 2010
Words:2973
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