Catheter-induced atrioventricular nodal block during radiofrequency ablation

Anthony King, MD, Ming-Shien Wen, MD, San-Jou Yeh, MD, Chung-Chieh Wang, MD,

Fun-Chung Lin, MD, and Delon Wu, MD Tao-Yuan, Taiwan, Republic of China

This study examined the incidence and significance of catheter-induced atrioventricular nodal block (AVNB) during a radiofrequency ablation procedure that uses stiff large-tip steerable ablation catheters. AVNB was noted in 10 (1.6%) of 613 consecutive patients undergoing radiofrequency abla- tion therapy for atrioventricular nodal (AVN) reentrant ta- chycardia (592 patients) or atrioventricular reentry tachy- cardia incorporating a midseptal accessory pathway (21 patients). Of these 10 patients, 9 underwent AVN modifica- tion for AVN reentrant tachycardia and 1 for ablation of a midseptal accessory pathway. One patient had two epi- sodes of AVNB during two sessions undertaken because of recurrence of tachycardia. No patient had a preexisting con- duction defect before the study. In all 10 patients, AVNB was transient, and it lasted for a mean of 9.1 ± 19 minutes. It oc- curred during positioning of the ablation catheter in the junctional area before (8 patients) or after (2 patients) the start of radiofrequency current applications. Complete AVNB was noted on six occasions, second-degree AVNB on four occasions, and first-degree AVNB on one occasion. All blocks were associated with narrow QRS ventricular beats and with a site of block proximal to the His bundle. The mean ventricular heart rate during AVNB was 60 ± 23 beats/min. Two patients had transient asystole, with one having loss of consciousness. No patient required special treatment for heart block. One-to-one conduction resumed after reposi- tioning of the catheters, and the subsequent ablation proce- dure was successfully completed in 8 of the 10 patients. During a follow-up of 20 ± 12 months, none of the patients had severe dizziness or syncope, and none required im- plantation of a permanent pacemaker. In conclusion, tran- sient AVNB due to mechanical injury occurs during posi- tioning of a stiff large-tip steerable ablation catheter in the junctional area. Delivery of radiofrequency current to the site that provokes catheter-induced AVNB should be avoided. (Am Heart J 1996;132:979-85.)

From the Second Section of Cardiology, Department of Medicine, Chang Gung Memorial Hospital, Chang Gung Medical College.

Dr. King is an international fellow from Makati Medical Center, Manila, The Philippines.

Supported in part by grants from the National Science Council (NSC 85-2331-B182-068 and NSC 85-2331-B182-067) of the Republic of China, Taipei, Taiwan.

Received for publication Feb. 8, 1996; accepted March 18, 1996.

Reprint requests: Delon Wu, MD, Chang Gung Memorial Hospital, 199 Tung Hwa North Rd., Taipei, Taiwan.

Copyright © 1996 by Mosby-Year Book, Inc. 0002-8703/96/$5.00 + 0 4/1/75323

The risk of creating chronic heart block is a well- known complication of radiofrequency modification for atrioventricular nodal reentrant tachycardia. However, the occurrence of transient atrioventricu- lar block during radiofrequency ablation has rarely received comment. In a recent study Fenelon et al. 1 reported an incidence of transient complete heart block of 10% (19 of 186 patients) in patients with atrioventricular nodal reentrant tachycardia under- going fast- or slow-pathway ablation. Another study, by Hintringer et al.,2 noted that transient heart block occurred immediately after current application in 10 (17%) of 58 consecutive patients undergoing radio- frequency ablation of the slow atrioventricular nodal pathway. These complications were related to the delivery of radiofrequency currents.

A transient conduction defect due to positioning of the catheter is a well-recognized complication of car- diac catheterization and has been reported to occur in the right bundle branch, 3 in the fascicle, 4 in the His bundle, 4, 5 in the atrioventricular node proximal to the His bundle recording site, 6, 7 and in the acces- sory pathways, s, 9 Almost all previously reported cases have been observed during right-side hear t catheterization, including His bundle recording and implantation of a temporary pacemaker. However, catheter-induced atrioventricular blocks in patients with or without preexistent bundle branch block during left-side heart catheterization have been oc- casionally reported. 1°

The purpose of this study was to investigate the incidence and significance of mechanically induced atrioventricular nodal block during radiofrequency ablation procedures.

METHODS Study population. From June 1991 to May 1995, 613

consecutive patients with atrioventricular nodal reentrant tachycardia (592 patients) or atrioventricular reentrant tachycardia incorporating a midseptal accessory pathway (21 patients) were referred to Chang Gung Memorial Hos- pital for electrophysiologic study and radiofrequency abla- tion. The electrophysiologic procedure and transcatheter

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980 King et al. American Heart Journal

ablation technique were approved by the Institutional Re- view Board and were in accordance with the local ethical standards.

Of these 613 patients, 10 (1.6%) patients had 11 cathe- ter-induced atrioventricular blocks. These 10 patients constituted the study population. There were 9 females and ~1 male ranging in age from 16 to 54 years (mean 29 +- 14 years). All 10 patients had a normal resting elec- trocardiogram without any known or documented conduc- tion disturbance before the study, and none had structural heart disease, although i patient (case 2) had systemic ar- terial hypertension. Nine patients underwent atrioven- tricular nodal modification for atrioventricular nodal re- entrant tachycardia, and 1 underwent an ablation for a midseptal accessory pathway.

Electrophysiologic study. The electrophysiologic study was performed as previously described. 11 First, all cardio- tonic drugs were discontinued for at least 3 half-lives, and informed written consent was obtained. Three 6F quadri- polar electrode catheters (USCI 002943) were introduced percutaneously into the femoral vein; advanced into the right atrium; and then positioned in the right ventricular apex, across the tricuspid valve, and in the high right atrium, respectively. A fourth 6F quadripolar catheter was introduced percutaneously via the right internal jugular vein and advanced into the coronary sinus. All catheters were positioned for recording local electrograms and pac- ing.

Electrocardiographic leads I, aVF, and V1 and intracar- diac electrograms from multiple sites were simultaneously displayed and recorded on a multichannel oscilloscope re- corder (Midas System, PPG Industries, Lenexa, Kan.; Electronics for Medicine, VR-16, White Plains, N.Y.) at a paper speed of 100 to 150 mm/sec. Complete anterograde and retrograde studies using incremental pacing and extrastimuli were performed in each patient. Conduction intervals, refractory periods of anterograde or retrograde dual atrioventricular node pathways, and accessory path- ways were measured and defined as previously de- scribed. 11-14

Radiofrequency catheter ablation. Selective slow-path- way ablations using the inferior approach 12, 13 were done in all patients with atrioventricular nodal reentrant ta- chycardia. With this approach, a 7F quadripolar steerable electrode catheter with a 4 mm distal electrode and 2 mm interelectrode spacing between the two distal electrodes (Mansfield EP, Watertown, Mass.) was initially manipu- lated to record the maximum proximal His deflection at the apex of Koch's triangle. The catheter tip was then slowly curved downward in a clockwise fashion until the His bundle deflection was no longer appreciated and the ratio of atrial to ventricular deflection was <1. The radiofre- quency currents then were delivered at this site.

Catheter ablation of the midseptal accessory pathway in patients with atrioventricular reentrant tachycardia was done as described previously. 14 The ablation catheter was advanced to the right atrium, and using the His bundle and coronary sinus catheters as references, the tip of the cath- eter was positioned at various sites in the atrioventricular

junctional area to map a para-Hisian or paranodal acces- sory pathway to identify the target site for delivery of ra- diofrequency currents.

Catheter-induced atrioventricular block. Catheter-in- duced atrioventricular block was defined as the appear- ance of block due to mechanical t rauma during manipula- tion of the electrode catheter within Koch's triangle and not related to the application of radiofrequency currents. The block could occur before or after the commencement of radiofrequency ablation therapy. Blocks that developed during application of radiofrequency currents, whether they were transient or persistent, were excluded and were considered a complication of radiofrequency ablation.

On development of atrioventricular block, the type, du- ration, and site of involvement were determined. The pa- tient's vital signs, including heart rate or rate of the escape rhythm, were constantly monitored. The offending cathe- ter was withdrawn from the junctional area immediately. Patients were continuously observed and temporary pac- ing was done as required by the situation. On resolution of the block, the electrophysiologic study was repeated, and radiofrequency ablation was done as described in the pre- vious section. After the procedure, all patients underwent serial daily 12-lead electrocardiography for 3 days and 24- hour Holter monitoring before discharge.

Follow-up. Patients were discharged and followed up closely in the clinic. Additional 12-lead electrocardiograms were recorded at each clinic visit. Any symptoms that might be attributable to atrioventricular block were re- corded; functional classifications were based on daily activities; and abnormal physical examination findings, if any, were evaluated; and a follow-up electrophysiologic study was advised for each patient 2 to 3 months after the initial study.

Statistics, Data are expressed as means +_ SD and were analyzed by Student's t test. Differences were considered statistically signfficant at a p value of <0.05.

RESULTS Catheter-induced atrioventricular block (Table I).

Cathe te r - induced a t r ioven t r i cu la r block was ob- served i n 1 0 pa t i en t s dur ing m a n i p u l a t i o n of the large- t ip abla t ion ca the te r in the midsep ta l area. Of these 10 pa t ien ts , t he re were 9 (1.5%) f rom a m o n g the 592 pa t i en t s wi th a t r ioven t r i cu la r nodal reen- t r a n t t achycard ia , and 1 (4.8%) (case 2) f rom a m o n g the 21 pa t i en t s wi th a midsep ta l accessory pa thway . One pa t i en t (case 8) wi th a t r ioven t r i cu la r nodal re- e n t r a n t t achyca rd ia h a d two episodes of ca theter- in- duced a t r ioven t r i cu la r block dur ing two abla t ion sessions. Thus a to ta l of 11 ca the te r - induced blocks were noted.

In n ine episodes (eight pat ients ; cases 1 t h rough 8), ca the te r - induced a t r ioven t r i cu la r block occurred before the s t a r t of rad iof requency cu r ren t applica- tion, and in two episodes (cases 9 and 10) i t occurred af ter c o m m e n c e m e n t of rad iof requency ablat ion. In

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American Heart Journal King et al. 981

Table I. Clinical and electrophysiologic findings

AVB

Structural Ventricular Follow-up Follow-up Age heart Supraventricular Duration heart rate duration E P S

Patient (yr) Sex disease tachycardia Type (sec) Site (beats ~rain) (too) (days)

1 18 M No AVNR T CAVB 50 Prox imal to H or 54 9 270 nodea l -His ian

2 54 F H y p e r t e n s i o n AVRT CAVB >10 Prox ima l to H 0* 34 - - 3 47 F No AVNRT 2 ° AVB 60 Prox ima l to H 58 15 - - 4 44 F No AVNRT 2 ° AVB 10 Prox imal to H 92 17 62 5 33 F No AVNR T 2 ° AVB 8 Prox ima l to H 60 12 - - 6 32 F No AVNR T CAVB 63 Prox imal to H 60 14 75 7 18 F No AVNRT 1 ° AVB 1800 Prox ima l to H 70 37 70 8 17 F No AVNRT CAVB 3600 Prox ima l to H 78 28 665

CAVB 40 Prox ima l to H 50 8 - - 9 26 F No AVNR T CAVB 300 Prox imal to H 60 39 71

10 16 F No AVNR T 2 ° AVB 90 Prox imal to H 77 11 69

AVB, Atrioventricular block; AVNRT, atrioventricular nodal reentrant tachycardia; AVRT, atrioventricular reentrant tachycardia; CAVB, complete AVB; EPS, electrophysiologic study; H, His bundle; 1 ° AVB, first-degree AVB; 2 ° AVB, second-degree AVB. *Asystole with loss of consciousness.

the latter two cases, there was no atrioventricu]ar block during delivery of radiofrequency current. First-degree atrioventricular block was noted on one occasion (case 7), second-degree atrioventricular block on four occasions (cases 3 through 5 and case 10), and third-degree atrioventricular block on 6 oc- casions (5 patients; cases 1, 2, 6, 8, and 9) (Figs. I and 2). The ventricular rate during the block episode was 60 _+ 23 beats/min and was 50 _+ 27 beats/min in pa- tients with complete heart block.

Two patients (cases 1 and 2) had an asystole last- ing longer than 3 seconds (4 and >10 seconds, respectively). The escape rhythm was of narrow QRS rhythm during heart block that was preceded by a His bundle potential, except in the patient who had an asystole lasting >10 seconds. The latter patient lost consciousness, whereas the others were asymp- tomatic during the block episode. His bundle elec- trograms recorded during heart block revealed that the site of conduction delay or block was located proximal to the His bundle recording site in all of the patients. However, one patient with prolonged asys- tole (case 1), in whom low-frequency nodal potentials were observed on the electrogram recorded by the ablation catheter positioned near the compact node, had progressive fragmentation and diminution of the nodal potentials during the episode of block (Fig. 1).

All blocks were transient and lasted 8 seconds to 1 hour (mean _ SD = 9.1 _ 19 minutes). The sinus cycle lengths during control, 10 minutes before block, 1 minute before block, and during block were 650 _ 63 msec, 625 _+ 33 msec, 640 - 41 msec, and 542 _-+ 57 msec, respectively. The sinus cycle length

during block was significantly shorter than that be- fore block (p < 0.001). The longest atrial paced cycle length that produced second-degree atrioventricular nodal block was 380 _+ 100 msec after recovery of one-to-one atrioventricular conduction, as compared with 326 _+ 58 msec before the occurrence of cathe- ter-induced block (difference not significant). In one patient (case 7), the predischarge 24-hour Holter re- cordings showed two episodes of type 1 block.

In eight patients, the radiofrequency ablation pro- ceeded successfully without further complication af- ter recovery of normal atrioventricular conduction, whereas in two patients the radiofrequency ablation was deferred. In the former eight patients, the deliv- ery of the radiofrequency current was avoided at the site that provoked catheter-induced atrioventricular nodal block. In one (case 8), it was deferred because of a prolonged heart block of 1 hour. This patient un- derwent a second ablation session 22 months later because of recurrence of atrioventricular nodal reen- trant tachycardia, and again he had an episode of catheter-induced heart block. This time the antero- grade conduction recovered within 40 seconds, and the patient underwent a successful ablation of atri- oventricular nodal reentrant tachycardia. In the other patient (case 2), who had a concealed midsep- tal accessory pathway, the radiofrequency ablation was deferred because there was no ventricular-atri- al conduction after resumption of normal atrioven- tricular conduction. This patient had no recurrence of tachycardia during follow-up, but she refused a repeated electrophysiologic study.

Follow-up (Table I). All 10 patients were followed

N o v e m b e r 1996 982 King et al. A m e r i c a n H e a r t J o u r n a l

I

AVF

HPO~

DCS I -

PCS

RF

HBE

I I

r

~ , _ J~ .r r r-

I

AVF

V1

HRA

DCS

PCS

HBE

I I I I I I I I I '

L L L L L r r r r r r [ r r r [ r r ' r r [ I" "[" ~'" T T- " 'r" r" I-- [" I-

Fig. 1. Recordings from case 1 showing catheter-induced atrioventricular nodal block with asystole. Top, Sudden onset of complete atrioventricular block with prolonged ventricular asystole, which occurred when tip of ablation catheter was mapping near compact node at apex of Koch's triangle. His bundle catheter recorded sharp His bundle potentials, whereas ablation catheter recorded low-frequency nodal potentials (arrows). During episode of atrioventricular block, each atrial potential was not followed by His bundle po- tential on His bundle electrogram, but nodal potentials that displayed progressive fragmentation and diminution of low-frequency waves (arrowheads) were noted on first two blocked P waves. Bottom, One- to-one atrioventricu]ar conduction resumed after ablation catheter was withdrawn from junctional area. I, AVF, and V1, Electrocardiographic leads I, aVF, and V1; HRA, DCS, and PCS, bipolar electrograms re- corded from high right atrium, distal coronary sinus, and proximal coronary sinus, respectively; RF and HBE, bipolar electrograms recorded from distal two electrodes of ablation catheter and His bundle cath- eter; H, His bundle potential. *P waves during complete block.

closely af ter radiofrequency ablation. None of these 10 pa t ien ts had severe dizziness or syncope over a follow-up period of 20 _+ 12 months (range 8 to 39 months) . Seven pat ients , including the one in whom the initial radiofrequency ablat ion was deferred and there was a recur rence of tachycardia , unde rw en t a follow-up electrophysiologic s tudy 183 +_ 225 days

af ter radiofrequency ablation. The longest atr ial paced cycle length t h a t caused second-degree atrio- ven t r icu la r block among these 7 pa t ien ts was 421 +_ 153 msec (range 250 to 650 msec). In none was there induct ion of tachycard ia wi th the exception of the one pa t i en t in whom the initial ablat ion was de- ferred.

V o l u m e 1 3 2 , N u m b e r 5 A m e r i c a n H e a r t J o u r n a l King et al. 983

I I [ l l l l l l l l l l l l [ l l l ( l [ l l l l ( l l l l ! q l ( ! l l i ( ! ! ! ! ! ! !

AVF ~ ~ - - ~ - ~

. ~ , ~ ¢~ ~ ~ .._ i

! i t I I [ I I 1 I I I I I I I I I I I f I I I I I I I I / , " ~

) i i ~ , , 1 ~ l i l l l l l t I I I l l l l l l l l l I I

AvF ~ ~ - - - J A r ^ . . . . . . .

HRA J~, ~. . . . . . _~,

o s .... ¢~ . ,~ - . , , . -

_ _ -

Fi 9. 2. C•ntinu•usre••rdingsfr•m•ase5sh•wingca•heter-indu•edse••nd-degreeatri•ventricu•arb•••k. First two sinus P waves were conducted to ventricles with prolongation of AH interval (145 msec); third p wave was blocked proximal to His bundle recording site. Third to sixth ventricular beats were junctional escape beats that were preceded by H spike. Ninth and tenth P waves were conducted with prolongation of AH interval (150 to 155 msee). Atrioventricular conduction recovered after withdrawal of ablation cath- eter from junctional area. OS, Bipolar eleetrogram recorded from the ostium of the coronary sinus;A, atrial; V, ventrieular. Other abbreviations as in Fig. 1.

DISCUSSION Catheter-induced conduction block. Conduction dis-

turbance resulting from catheter manipulation in- side the heart is a well-known phenomenon. Soon after the introduction of cardiac catheterization, the complication of right bundle branch block was recog- nized. ~ It can occur during standard right-side heart catheterization with fluid-filled lumen catheters; during electrophysiologic studies or implantation of a temporary pacemaker with stiffer electrode cathe- ters; or during the insertion of a soft balloon-tip pul- monary artery catheter. Mechanical t rauma result- ing from direct contact of the catheter tip with the proximal right bundle is the main cause of the block; however, irritation of the right bundle by the stiff shaft of the catheter may also contribute to the occurrence of conduction disturbance.

Catheter-induced right bundle branch block is usually transient, has no sequelae, and requires no special management. However, in patients with pr e - existing left bundle branch block, catheter-induced

right bundle branch block may result in complete heart block with subsequent ventricular asysto- le.10, 15-17 Most of these blocks resolve within a few seconds when the offending catheter is carefully withdrawn, and implantation of a temporary pace- maker usually is unnecessary in most patients. However, permanent heart block requiring implan- tation of a permanent pacemaker has been noted on rare occasions. 15

Catheter-induced conduction disturbance to tis- sues other than the right bundle has also been observed. Stein et al. 1° described a patient with pre- existing right bundle branch block in whom tran- sient complete heart block occurred during left-side heart catheterization, presumably because of injury to the proximal lefL bundle by the catheter. Jacobson and Scheinman 5 described a patient with preexisting left bundle branch block in whom transient high- grade atrioventricular block and "split His" poten- tials were observed. In this patient, in addition to the injury to the proximal right bundle, the His bundle

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984 King et al. American Heart Journal

probably also sustained injury. Castellanos et al. 4 described four patients with mechanically induced right bundle branch block associated with left poste- rior or left anterior hemiblock. His bundle recording in one of their four patients revealed a two-to-one in- tra-Hisian block. They implied that mechanical t rauma to the His bundle was responsible for both intra-Hisian block and the fascicular block.

Mechanical injury to the atrioventricular node is very uncommon during regular right-side heart catheterization or electrophysi01ogic study. Gault et al. Is described a 9-year-old girl with tetralogy offa l - lot, dextroposition of the heart, and agenesis of the right pulmonary artery and right lung, in whom persistent complete atrioventricular block with junc- tional escape rhythm occurred as the catheter was withdrawn from the aorta to the right ventricle. In this patient, the site of block was not verified by a His bundle recording. Freed and Rosenthal ~ and Peters et al. 7 each reported one case of catheter-induced atrioventricular nodal block during cardiac cathe- terization or electrophysiologic study.

Accessory pathway conduction also may be dam- aged during manipulation of the electrode catheter. Novick et al. s described four patients with catheter- induced conduction delay or block in the accessory pathway that recovered in 14 hours. Robinson et al. 9 reported a case of permanent loss of accessory path- way conduction during placement of a coronary sinus catheter. The advent ofradiofrequency ablation with the use of stifflarge-tip steerable electrode catheters has made catheter-induced mechanical t r auma to the conduction pathways more common.

In a prospective study conducted by Chiang et al.19 in 666 patients receiving radiofrequency ablation for supraventricular tachycardia, catheter-induced me- chanical t rauma was observed in 17 (2.6%) patients, 4 by the small-tip diagnostic electrode catheter and 12 by the large-tip mapping or ablation catheter. More than half of their patients had long-term res- olution of the tachycardia as a result of mechanical trauma. However, the subsequent rate of recurrence oftachycardia was significantly greater in those with mechanical t rauma than in those without mechani- cal t rauma during ablation.

Catheter-induced atrioventricular nodal block during radiofrequency ablation. The anatomic location of the atrioventricular node and His bundle may protect them from mechanical t rauma by the regular diag- nostic fluid-filled catheter or electrode catheter. However, the deflectable large-tip stiff ablation elec- trode catheter designed to achieve firm tissue contact may result in a higher incidence of mechanical t rauma to the atrioventricular node or His bundle,

especially when this catheter is being manipulated in the junctional area for ablation of atrioventricular nodal reentrant tachycardia or a midseptal accessory pathway: In the series of Chiang et al., 19 4 of the 254 patients undergoing radiofrequency modification of atrioventricular nodal reentrant tachycardia sus- tained mechanical injury, including 3 with injury on the retrograde fast pathway and i with injury on the anterograde slow pathway. The tachycardia was rendered noninducible; however, in none of their pa- tients did high-grade atrioventricular block develop. In a preliminary study, Cossfi et al.20 reported that 5 (8%) of 63 patients undergoing radiofrequency modification of atrioventricular nodal reentrant ta- chycardia had transient catheter-induced second- or third-degree atrioventricular block. In addition, 2 of these 5 patients had atrioventricular block in subse- quent standard radiofrequency ablations. The au- thors suggested that patients with catheter-induced atrioventricular nodal block are more likely to have complications of hear t block in the subsequent ra- diofrequency ablation. Neither Chiang et al.19 nor Cossfi et al. 2° specified whether the mechanical t rauma in their patients was induced before or after commencement of the radiofrequency ablation ther- apy.

In the current study, nine episodes of catheter-in- duced atrioventricular nodal block occurred before the start of radiofrequency ablation procedure, and two episodes occurred after the ablation procedure. The block was transient in all patients. It deferred the subsequent radiofrequency ablation therapy in two patients, although it did not increase the inci- dence of complication of hear t block in the subse- quent radiofrequency ablation. The observations in this study concur with the observation that most pa- tients with transient atrioventricular nodal block during delivery of the radiofrequency current for modification of atrioventricular nodal reentrant ta- chycardia have a benign outcomefl 2 In these pa- tients, the pressure rather than the thermal t rauma may be responsible for the transient hear t block. Be- cause delivery of radiofrequency current to the atri- oventricular nodal area requires maintenance of a constant clockwise torque with application of pres- sure to the tip of the catheter, transient atrioven- tricular block that occurs during delivery of the ra- diofrequency current may in part be related to pres- sure injury. However, in our opinion, the site that provokes mechanical atrioventricular block should be avoided as the site for delivery of radiofrequency current.

The single case of a recording of nodal potentials that displayed fragmentation and diminution of

Volume 132, Number 5 #t aZ. 985 American Heart Journal /~/~g

waves during the episode of repetitive atrioventric- ular block deserves further comment. Damato et al. 21 first reported the recording of nodal potentials, and Haissaguerre et al. 22 first noted fragmentation and diminution of these low-frequency potentials during gradually diminished conduction. The manifesta- tions observed in our patient are consistent with a site of block in the atrioventricular node, but it also may have occurred in the nodal-Hisian area or even the proximal His bundle.

Conclusion. Transient atrioventricular nodal block due to mechanical injury occurs not infrequently dur- ing positioning of a large-tip stiff steerable ablation catheter in the junctional area. These catheters should be manipulated gently in this area to avoid this complication. Although this complication is benign in most patients, the site that provokes catheter-induced atrioventricular nodal block should be avoided as the site for subsequent delivery of radiofrequency current or delivery of current in a subsequent ablation session.

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