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(Circulation. 1995;91:2614-2618.)
© 1995 American Heart Association, Inc.

Articles

Effect of Dual Atrioventricular Node Pathways on Atrioventricular Reentrant Tachycardia

Zoltan Csanadi, MD; George J. Klein, MD; Raymond Yee, MD; Ranjan K. Thakur, MD; Huagui Li, MD

From the Department of Medicine, The University of Western Ontario, London, Ontario, Canada.

Correspondence to Dr George J. Klein, University Hospital, 339 Windermere Rd, London, Ontario, Canada.

	Abstract

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Background Dual atrioventricular (AV) node pathway physiology is frequently observed in patients with AV accessory pathways.

Methods and Results To examine the implications of this, we identified 36 patients (19 men and 17 women; mean±SD age, 30±13 years) with both phenomena. The 36 patients had 48 accessory pathways. Twenty-seven patients had bidirectional and 9 had unidirectional accessory pathways. Of the 34 patients with inducible atrioventricular reentry, 17 used the slow and 11 used the fast anterograde AV node pathway exclusively during AV reentrant tachycardia, whereas 6 patients used both the fast and the slow AV node pathways. AV node reentrant tachycardia was inducible in addition to AV reentry in 7 patients. Both the cycle length and AH intervals were significantly longer during slow pathway–dependent (cycle length, 411±58 milliseconds [ms]; AH, 229±42 ms) than during fast pathway–dependent (cycle length, 322±40 ms; AH, 121±25 ms; P<.05) reentrant tachycardias. Two patients had only AV node reentrant tachycardia inducible despite the presence of the accessory pathway. Four patients with technically difficult accessory pathways were managed by AV node modification with slow pathway (3) or fast pathway (1) ablation. Three of them remained free of symptoms 7, 14, and 25 months after the procedure whereas 1 patient had recurrence of arrhythmia.

Conclusions AV reentrance with dual AV node pathways frequently depends exclusively on either the slow or the fast AV node pathway for clinical tachycardia. This may provide additional options for ablation in technically difficult cases when the accessory pathway is not otherwise problematic.

Key Words: atrioventricular node • physiology • tachycardia

	Introduction

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Dual atrioventricular (AV) node pathway physiology is known to occur in 8% to 40%^{1 2 3 4} of patients with accessory AV pathways, leading to a variety of possible reentrant circuits.^{5 6 7 8 9 10 11} To examine the implications for radiofrequency ablation, we evaluated the contribution of the fast and slow AV node pathways and accessory pathways in a consecutive series of patients assessed for arrhythmia associated with the Wolff-Parkinson-White syndrome.

	Methods

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Study Patients
We reviewed the records of 382 consecutive patients with accessory AV pathways who were referred for electrophysiological testing between January 1, 1990, and August 31, 1993, because of documented paroxysmal supraventricular tachycardia or palpitations. We identified 43 patients (12%) who also had dual antegrade AV node pathway physiology or AV node reentrance. In 7 patients, no tachycardia was inducible during electrophysiological testing; these patients were excluded from further study. The remaining 36 patients (19 men and 17 women; mean±SD age, 30±13 years) were the subjects of the present study.

Electrophysiological Study
The study protocol has been described.^{12 13} Briefly, standard electrode catheters were positioned in the coronary sinus, the right ventricular apex, the high right atrium, and at the His bundle region. Programmed stimulation was performed at twice diastolic threshold with 2-millisecond (ms) square-wave pulses. Atrial and ventricular extrastimulus testing at two cycle lengths (600 and 400 ms) was performed until atrial and ventricular refractoriness was reached. Atrial and ventricular incremental pacing was performed until AV and ventriculoatrial block occurred, respectively. If reentrant tachycardia was not inducible with these techniques, burst pacing and double atrial or ventricular extrastimuli were tried as well as isoproterenol and atropine administration. After radiofrequency ablation, the above protocol was repeated 30 minutes after the last energy application, with extrastimulus testing usually performed at at least one cycle length (600 ms).

Diagnostic Criteria
The criteria used for the diagnosis of AV reentry and AV node reentry have been described.¹³ Dual AV node pathways required at least a 50-ms increment in the AH interval for a 10-ms decrement in coupling interval during atrial extrastimulus testing. AV node reentrance manifested as either AV node echo cycles or AV node reentrant tachycardia. When antegrade conduction over the accessory pathway masked antegrade conduction over the fast AV node pathway, the diagnosis of dual AV node pathways was based on the test performed after successful accessory pathway ablation.

Participation of the slow or fast AV node pathway as the antegrade limb of AV reentrant tachycardia was determined by comparison of the AH interval during tachycardia with that observed during slow AV node pathway conduction with atrial extrastimuli, incremental pacing, or AV node reentry. Tachycardia induced by atrial extrastimuli after the discontinuity ("jump") in the AH interval was considered to use the slow AV node pathway for antegrade conduction.

Therapeutic Interventions
Radiofrequency ablation immediately followed the diagnostic study. For accessory pathway ablation,¹⁴ radiofrequency current was applied between the 4-mm tip electrode of the ablation catheter and a backplate. Ablation was not temperature controlled. The duration of ablation attempts ranged between 10 and 45 seconds. If loss of preexcitation was not observed during the first 10 seconds of energy delivery, current was discontinued. AV node modification was performed using an anatomic approach.¹⁵ The operative ablation of accessory pathways¹⁶ and operative AV node modification¹⁷ have been described.

Statistical Analysis
Mean AH intervals and tachycardia cycle lengths were compared using Student's t test. Two distinct AH intervals and tachycardia cycle lengths due to a switch between fast and slow AV node pathways within an episode of tachycardia were considered as two distinct tachycardias for statistical purposes.

	Results

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The 36 patients had a total of 48 accessory pathways. There was a preponderance of left lateral and posteroseptal¹⁴ pathways as is usually found in patients with Wolff-Parkinson-White syndrome. The accessory pathway was unidirectional in 9, conducting retrogradely only in 8, and conducting anterogradely only in 1. Typical discontinuous curves relating AH interval to prematurity of an atrial extrastimulus (dual pathways) were observed in 26 of 36 patients (72%). AV node reentry was observed in 26 patients with single echo cycles observed in 17 and sustained AV node reentrant tachycardia in 9 patients. Ten patients had dual AV node pathways without AV node reentrance.

Dual pathway physiology or AV node reentrance was observed before ablation in 24 patients. This diagnosis was made by presence of dual AV node pathways (n=8), alternation of AH intervals during AV reentry (n=6), induction of sustained AV node reentrant tachycardia (n=7), or observation of single AV node reentrant cycles (n=3). The diagnosis was made only after ablation of the accessory pathway in 12 patients. This was manifest as single AV node echo cycles (n=8), dual pathways (n=2), or sustained AV node reentrant tachycardia (n=2).

The most common arrhythmia was AV reentry without coexistent AV node reentry (27 patients [75%]; Table). Two (6%) patients had only AV node reentry, whereas 7 (19%) had both AV reentry and AV node reentry. Of the 34 patients with AV reentry, 17 used the slow and 11 used the fast anterograde AV node pathway exclusively, whereas 6 used both the slow and the fast AV node pathways alternately (Figs 1 and 2).

View this table: [in this window] [in a new window]   Table 1. Fast and Slow Pathways in Tachycardia

View larger version (20K): [in this window] [in a new window]   Figure 1. Variation of atrioventricular reentrant tachycardia cycle length related to variability in the AH interval. The retrograde limb of this circuit is a left lateral accessory pathway as shown by the earliest retrograde atrial activation in distal coronary sinus (arrow). Anterograde conduction is alternating between a fast and a slow atrioventricular node pathway. A indicates atrial electrogram; CS4 to CS1, coronary sinus from proximal to distal, respectively; H, His bundle potential; HB, His bundle electrograms; RA, right atrium electrogram; RV, right atrium electrogram; RV, right ventricle electrogram; and 2 and V6, surface ECG leads.

View larger version (24K): [in this window] [in a new window]   Figure 2. Top, Two distinct tachycardia rates in atrioventricular reentrant tachycardia. Before the ventricular extrastimulus, retrograde conduction is proceeding over a left lateral accessory pathway. The AH interval is 150 milliseconds. After the ventricular extrastimulus, retrograde conduction remains unchanged, but the AH interval is now 270 milliseconds. This may be related to slight preexcitation of the atrial activation by the premature ventricular extrastimulus, causing block in the anterograde fast atrioventricular node pathway. Alternatively, it is possible that concealed retrograde conduction into the fast pathway by the ventricular extrastimulus resulted in fast pathway block after the subsequent atrial activation. Bottom, Atrioventricular node reentry in the same patient after ablation of two accessory pathways. The AH interval is 280 milliseconds, similar to that observed during atrioventricular reentry (top) using the slow pathway for anterograde conduction. See Fig 1 for abbreviations.

Use of the fast or slow anterograde AV node pathway influenced the cycle length of AV reentrant tachycardia, and, as expected, this was related to the AH interval (Figs 3 and 4). The cycle length of tachycardia in patients using the fast AV node pathway anterogradely was shorter than that in patients using the slow pathway (mean±SD, 322±40 versus 411±58 ms, respectively; P<.001). The AH interval was shorter in AV reentry using the fast pathway than that using the slow pathway (121±25 versus 229±42, P<.001).

View larger version (13K): [in this window] [in a new window]   Figure 3. Bar graph showing comparison of atrioventricular reentrant tachycardia (AVRT) cycle length (CL) between patients using a fast anterograde atrioventricular node pathway and those using a slow pathway.

View larger version (12K): [in this window] [in a new window]   Figure 4. Comparison of AH interval in tachycardia using a fast versus a slow atrioventricular node pathway as the anterograde limb. The difference in cycle length observed in Fig 3 is related to change in the AH. See Fig 3 for abbreviations.

Miscellaneous Observations
The coexistence of dual AV node pathways and AV node reentrance with AV tachycardia resulted in spontaneous termination of tachycardia in some patients. This occurred as a result of the occurrence of a long–short cycle with block in the AV node or accessory pathway of the subsequent cycle. Alternatively, the occurrence of AV node reentrant atrial echo cycles sometimes terminated AV reentry (Fig 5).

View larger version (18K): [in this window] [in a new window]   Figure 5. Termination of atrioventricular reentrant tachycardia with an atrioventricular node echo cycle. Atrioventricular tachycardia at cycle length 380 milliseconds in the first four cycles uses the slow atrioventricular node pathway anterogradely and a left lateral accessory pathway retrogradely. Retrograde conduction over the fast atrioventricular node pathway (fifth cycle) results in premature atrial activation of the slow anterograde pathway with block and termination of tachycardia. See Fig 1 for abbreviations.

Accessory pathway bystander participation in AV node reentrant tachycardia was potentially possible in 6 patients where the anterograde refractory period of the accessory pathway permitted accessory pathway conduction at the cycle length of tachycardia. However, this was not observed in any of the study patients, suggesting that this phenomenon is usually limited by concealed retrograde conduction into the accessory pathway.

Therapy
Most patients underwent accessory pathway ablation by either catheter¹⁴ or surgery.¹⁶ One patient had a failed accessory pathway ablation. Three patients had both radiofrequency accessory pathway ablation and slow AV node pathway ablation. Three patients had only slow AV node pathway radiofrequency ablation. The latter patients had AV reentry dependent on slow AV node pathway conduction and the accessory pathway was not considered to be otherwise problematic. None of these patients had inducible arrhythmia at conclusion of the procedure despite intact accessory pathway conduction. One patient had multiple tachycardias including AV node reentry and both antidromic and orthodromic reentry related to two accessory pathways. Fast AV node pathway ablation done inadvertently during an attempt at slow pathway ablation was performed and resulted in noninducibility of tachycardia despite intact accessory pathway conduction in both directions.

Follow-up
All patients with initially successful accessory pathway ablation remain free of tachycardia during a mean follow-up of 21.3 months (range, 7 to 49 months). Of the 3 patients undergoing slow AV node pathway ablation, 2 are free of tachycardia after 25 and 7 months, and 1 had recurrence after 14 months. The latter patient was found to have persistent dual AV node pathways and inducible AV reentrant tachycardia and subsequently underwent both slow AV node pathway ablation and accessory pathway ablation. The patient undergoing fast AV node pathway ablation has not had recurrence of tachycardia and persists with anterograde preexcitation and anterograde slow AV node pathway conduction (14 months).

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
Results of the present study confirm the relatively frequent (12%) coexistence of dual AV node pathways in patients with manifest or concealed Wolff-Parkinson-White syndrome previously reported to be between 8% and 40%.^{1 2 3 4} The coexistence of dual AV node pathways in this context had significant effects on the manifestations of tachycardia with some practical therapeutic implications pertaining to radiofrequency ablation. Some patients with the Wolff-Parkinson-White pattern electrocardiographically only had inducible AV node reentrant tachycardia with no relation of clinical tachycardia to the manifest preexcitation. Others had both inducible AV reentry and AV node reentry. Most patients had AV reentry as the only tachycardia mechanism, with the majority requiring either the slow anterograde AV node pathway (56%) or the fast anterograde AV node pathway (30%) exclusively as the anterograde limb of the reentrant circuit. These observations highlight the importance of a detailed diagnostic study before therapeutic radiofrequency ablation¹⁸ to ensure that ablation is not directed against a clinically insignificant accessory pathway. The observations also permit alternate therapeutic options in patients with AV reentry, ie, slow or fast AV node pathway ablation in selected patients in whom accessory pathway ablation is technically difficult and anterograde accessory pathway conduction is not problematic. It may be argued that slow AV node pathway ablation is preferred in some of these individuals as a technically simpler and more expedient procedure than accessory pathway ablation. The ideal candidate for this preferred approach would have clinical AV reentry dependent on the slow AV node pathway and an accessory pathway with a long anterograde refractory period.

The observation of two populations of AH intervals during AV reentrant tachycardia in this study was related to dual AV node pathway physiology (Figs 1 and 2). However, alternating AH intervals may be observed in the absence of dual pathways,^{19 20} and this may be related to functional oscillation of the AH interval between two points on the curve relating AH interval to prematurity of atrial extrastimuli. In the present study, the presence of variable AH intervals within a given episode of tachycardia contributed to spontaneous termination of tachycardia in some patients.

The AH interval during AV reentrant tachycardia was found to be a reliable indicator for the presence of anterograde slow or fast AV node pathway conduction. The longest AH interval during tachycardia using the fast AV node pathway was 160 ms, whereas the AH interval was never less than 180 ms in patients using the slow anterograde AV node pathway. These data suggest that an AH interval during AV reentrant tachycardia of longer than 180 ms may raise the suspicion of anterograde slow pathway conduction. The observation also underscores the difficulty of attempting to distinguish AV node reentrant tachycardia from AV reentrant tachycardia by cycle length alone since patients using slow pathway conduction anterogradely may well have cycle lengths similar to patients with typical AV node reentry.

In conclusion, the frequent occurrence of dual AV node pathway conduction underscores the importance of detailed electrophysiological assessment before and after ablation of an accessory pathway. Although there is therapeutic relevance for only a small segment of the total population with the Wolff-Parkinson-White syndrome, alternative ablation strategies directed at the AV node may be considered in individuals when clinical tachycardia depends on either the slow or the fast AV node pathway and the accessory pathway is not otherwise problematic. Appropriate therapy will also be carried out in those presenting with sustained AV node reentry as the exclusive or concomitant clinical arrhythmia. The absence of clinical tachycardia during follow-up in those with only dual pathway physiology with or without single echo cycles would argue against the routine ablation of the slow pathway in these patients.

Received September 29, 1994; revision received December 1, 1994; accepted December 3, 1994.

	References

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1. Zardini M, Leitch JW, Guiraudon GM, Klein GJ, Yee R. Atrioventricular nodal reentry and dual atrioventricular node physiology in patients undergoing accessory pathway ablation. Am J Cardiol. 1990;66:1388-1389. [Medline] [Order article via Infotrieve]
   
2. Reyes W, Milstein S, Dunnigan A, Benditt DG, Kriett J, Pineda E. Indications for modification of coexisting dual atrioventricular node pathways in patients undergoing surgical ablation of accessory atrioventricular connections. J Am Coll Cardiol. 1991;17:1561-1567. [Abstract]
   
3. Pritchett ELC, Prystowsky EN, Benditt DG, Gallagher JJ. Dual atrioventricular nodal pathways in patients with Wolff-Parkinson-White syndrome. Br Heart J. 1980;43:7-13. [Abstract/Free Full Text]
   
4. Farshidi A, Josephson ME, Horowitz L. Electrophysiologic characteristics of concealed bypass tracts: clinical and electrocardiographic correlates. Am J Cardiol. 1978;41:1052-1060. [Medline] [Order article via Infotrieve]
   
5. Rosen KM. Atrioventricular nodal reentrance: an unexpected mechanism of paroxysmal tachycardia in a patient with preexcitation. Circulation. 1973;47:1267-1273. [Abstract/Free Full Text]
   
6. Spurell RAJ, Krikler D, Sowton E. Two or more intra-atrioventricular nodal pathways in association with either a James or Kent extranodal bypass in three patients with paroxysmal supraventricular tachycardia. Br Heart J. 1973;35:113-122. [Free Full Text]
   
7. Friedberg HD, Schamroth L. Three atrioventricular pathways: reciprocating tachycardia with alternation of conduction times. J Electrocardiol. 1973;6:159-163. [Medline] [Order article via Infotrieve]
   
8. Neuss H, Schlepper M. Unusual reentry mechanisms in patients with Wolff-Parkinson-White. Br Heart J. 1974;36:880-887.[Free Full Text]
   
9. Mandel WJ, Laks MM, Obayashi K. Atrioventricular nodal reentry in the Wolff-Parkinson-White syndrome. Chest. 1975;68:321-325. [Abstract/Free Full Text]
   
10. Amat-y-Leon F, Wyndham C, Wu D, Denes P, Dhingra R, Rosen K. Participation of fast and slow A-V nodal pathways in tachycardias complicating the Wolff-Parkinson-White syndrome. Circulation. 1977;55:663-668. [Abstract/Free Full Text]
    
11. Sung RJ, Styperek JL. Electrophysiologic identification of dual atrioventricular nodal pathway conduction in patients with reciprocating tachycardia using anomalous bypass tracts. Circulation. 1979;60:1464-1476. [Free Full Text]
    
12. Klein GJ, Prystowsky EN, Pritchett ELC, Davis D, Gallagher JJ. Atypical patterns of retrograde conduction over accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome. Circulation. 1979;60:1477-1486. [Abstract/Free Full Text]
    
13. Leitch J, Klein GJ, Yee R, Murdock C. Invasive electrophysiologic evaluation of patients with supraventricular tachycardia. Cardiol Clin. 1990;8:465-477. [Medline] [Order article via Infotrieve]
    
14. Leather RA, Leitch JW, Klein GJ, Guiraudon GM, Yee R, Kim YH. Radiofrequency catheter ablation of accessory pathways: a learning experience. Am J Cardiol. 1991;68:1651-1655. [Medline] [Order article via Infotrieve]
    
15. Wathen M, Natale A, Wolfe K, Yee R, Newman D, Klein GJ. An anatomically guided approach to atrioventricular node slow pathway ablation. Am J Cardiol. 1992;70:886-889. [Medline] [Order article via Infotrieve]
    
16. Guiraudon GM, Klein GJ, Gulamhusein S, Jones DL, Yee R, Perkins DG, Jarvis E. Surgical repair of Wolff-Parkinson-White syndrome: a new closed-heart technique. Ann Thorac Surg. 1984;37:67-71. [Abstract]
    
17. Fujimura O, Guiraudon GM, Yee R, Sharma AD, Klein GJ. Operative therapy of atrioventricular node reentry and results of an anatomically guided procedure. Am J Cardiol. 1989;64:1327-1332. [Medline] [Order article via Infotrieve]
    
18. Stites WH, Thakur RK, Yee R, Klein GJ. Evaluation of an abbreviated protocol for catheter ablation of left free wall accessory pathways. Am J Cardiol. 1993;72:836-838. [Medline] [Order article via Infotrieve]
    
19. Ross DL, Dassen WRM, Vanagt EJ, Brugada P, Barr FWHM, Wellens HJJ. Cycle length alternation in circus movement tachycardia using an atrioventricular accessory pathway. Circulation. 1981;65:862-868. [Abstract/Free Full Text]
    
20. Talajic M, Villemaire C, Papadatos D, Lemery R, Roy D, Nattel S. Cycle length alternation during supraventricular tachycardia: occurrence and mechanism in a canine model of atrioventricular reentrant tachycardia. PACE Pacing Clin Electrophysiol. 1990;13:314-325.[Medline] [Order article via Infotrieve]
    

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Csanadi, Z. Articles by Li, H. Search for Related Content PubMed PubMed Citation Articles by Csanadi, Z. Articles by Li, H.