Complete atrioventricular block, second-degree Mobitz type II and first-degree atrioventricular
block with right bundle branch block were observed consecutively following successful
radiofrequency ablation in close proximity to the sinus node. This resulted in the modification
and disappearance of the inappropriate sinus tachycardia that had previously been present.
Neither tachycardia nor conduction disturbances have been recorded in the 9-year follow-up,
implying that ventricular pacing standby should also be considered in high atrial ablation
cases. (Cardiol J 2007; 14: 504-507

Bednarek, Jacek

Lelakowski, Jacek

Majewski, Jacek

Małecka, Barbara

Tomala, Igor

English

Via Medica Journals

CASE REPORTCardiology Journal2007, Vol. 14, No. 5, pp. 504–507Copyright © 2007 Via MedicaISSN 1897–5593504 www.cardiologyjournal.orgAddress for correspondence: Jacek Bednarek, MDDepartment of Electrocardiology, Cardiology InstituteFaculty of Medicine, Jagiellonian UniversityPrądnicka 80, 31–202 Kraków, PolandTel./fax: +48 12 614 23 81e-mail: mcbednar@cyf-kr.edu.plReceived: 20.12.2006 Accepted: 24.04.2007Transient atrioventricular block following catheterradiofrequency sinus node modificationJacek Bednarek, Igor Tomala, Jacek Lelakowski, Jacek Majewski and Barbara MałeckaDepartment of Electrocardiology, Cardiology Institute, Faculty of Medicine,Jagiellonian University, Cracow, PolandAbstractComplete atrioventricular block, second-degree Mobitz type II and first-degree atrioventricularblock with right bundle branch block were observed consecutively following successfulradiofrequency ablation in close proximity to the sinus node. This resulted in the modificationand disappearance of the inappropriate sinus tachycardia that had previously been present.Neither tachycardia nor conduction disturbances have been recorded in the 9-year follow-up,implying that ventricular pacing standby should also be considered in high atrial ablationcases. (Cardiol J 2007; 14: 504–507)Key words: catheter ablation, radiofrequency, inappropriate sinus tachycardia,atrioventricular blockIntroductionTwelve years have passed since Waspe et al. [1]and Lee et al. [2] published the first works on sinusnode modification in inappropriate sinus tachycar-dia (IST), but no data have been reported concern-ing subsequent atrioventricular (AV) conductiondisturbances. We report on transient complicationsunique to IST ablation. In the case of the success-ful modification here presented, complete heartblock, followed by Mobitz type II second-degree AVblock and right bundle branch block (RBBB) withfirst-degree AV block occurred unexpectedly. Itsmechanism cannot be clearly explained. Althoughit later reverted spontaneously to normal conduc-tion, a less favorable clinical outcome is also likely.This makes ventricular lead introduction reasonablenot only in ablation proximal to the AV node [3, 4],but also in cases of sinus node modification.Case descriptionA 47-year-old female office clerk, the motherof three healthy children, had presented with fullysymptomatic IST and remained in ambulatory fol-low-up for eight years. She had experienced long-lasting palpitations, dizzy spells, spots before theeyes and multiple presyncopal and syncopal states.Her resting heart rate had rarely dropped below100/min except at night, showing markedly exces-sive acceleration during even moderate physicaleffort, and was concomitant with decreased exer-cise tolerance. Ambulatory, as well as detailed in-hospital diagnosis had been carried out in order toestablish the etiopathological background. All po-tential extra-cardiac disorders were excluded asproven causative factors. Invasive and non-invasivecardiac examination, including ECHO, coronarog-raphy, ventriculography and myocardial biopsyfailed to reveal any significant heart disease exceptfor sinus arrhythmia. Treadmill tests were per-formed twice but discontinued  at an early stageowing to presyncope after a heart rate of 164/min505Jacek Bednarek et al., Transient AV block following catheter RF sinus node modificationwww.cardiologyjournal.orghad been reached. Ambulatory ECG monitoringshowed long-lasting sinus tachycardia of up to 220/min.In addition, antiarrhythmic pharmacotherapy, usingall available drugs, appeared to be ineffective andresulted in the development of transient first-de-gree AV block. An ischemic or inflammatory etiol-ogy and AV node pathology were excluded, as, witha high degree of probability, was an ectopic origin.The electrophysiology (EP) studies performedtwice revealed neither signs of sinus automaticitynor conductive insufficiency. Retrograde ventricu-loatrial conduction was absent and the Wenckebachpoint appeared to be very high at over 220/min. Wefound no sign of dual node physiology or pre-exci-tation. Sinus node re-entry was excluded as, witha high degree of probability, was right atrial focaltachycardia. We performed sinoatrial node cathe-ter radiofrequency (RF) modification on 6 January1998. Following a detailed EP study, sinus tachy-cardia at a rate of 176/min, lasting over 20 min waseasily initiated during slow intravenous administra-tion of orciprenaline at a dose of 0.5 mg. Pro-grammed atrial and ventricular pacing neither ini-tiated nor terminated sinus tachycardia. All basicmeasurements, including AH, HV and QRS, re-mained within normal limits before and after theonset of arrhythmia. Endocardial mapping was per-formed using four electrodes placed at the follow-ing sites: the coronary sinus (Csp, Csd), the Hisbundle region (HBE), the high right atrium (HRA1,HRA2, HRA3, HRA4) and the ablative 7 F electrode(ABL) in the high right atrium. The first was intro-duced via the left subclavian vein and the othersusing the right femoral vein approach. Analysis ofatrial impulse propagation before and during tachy-cardia revealed a physiological sequence. We ob-served the earliest atrial activation potential record-ed from the HRA1 and HRA2 electrodes. At the lastone we found the atrial potential to be prolongedand fractionated with a multicomponent appearanceduring tachycardia. The ablative electrode wasplaced in this vicinity, close to the sinus node re-gion, at the junction of the superior vena cava withthe posterolateral right atrium wall. We targeted RFenergy at the site of earliest activation with frac-tionation of atrial potential during tachycardia. Thesecond RF delivery of 25 W × 60 s resulted in abrupttermination of the sinus tachycardia of 170/min withrestoration of a sinus rhythm of 75/min and normal-ization of the atrial potential morphology (Fig. 1).Two consecutive “consolidation” RF pulses weredelivered, each of 60 s × 25 W. Shortly afterwardsan unexpected 10-second episode of transient com-plete AV block was noticed with a junctional rhythmof 40/min (not recorded on paper for technical rea-sons) and later second-degree block of the MobitzII type (Fig. 2) and afterwards one-degree AV blockwith RBBB, which spontaneously disappeared af-ter two days.Owing to the nature of IST, there are no stand-ard methods of assessment of the efficacy of abla-tion, although several findings have been noted af-ter the procedure. In contrast to the initial state,slow sinus rhythm acceleration up to 135/min, anda gradual moderate slowing down was brought aboutby intravenous orciprenaline administration ata dose 1.0 mg. The atrial potential recorded fromFigure 2. Surface and intracardiac electrogram recor-ded soon after radiofrequency sinus node modification.Second-degree Mobitz type II atrioventricular block.Figure 1. Surface and intracardiac electrogram recor-ded during radiofrequency energy delivery shows ter-mination of sinus tachycardia of 170/min with restora-tion of sinus rhythm of 75/min.506Cardiology Journal 2007, Vol. 14, No. 5www.cardiologyjournal.orgthe high right atrium electrodes, initially prolongedand fractionated during tachycardia, did not dem-onstrate such characteristics afterwards. The EPstudies performed shortly afterwards and on thefollowing day revealed that the basic parameterswere unchanged. Hemodynamically essential sinustachycardia remained non-inducible, either withpacing or with a beta-sympathomimetic agent. Hol-ter monitoring showed none of the arrhythmia thathad hitherto prevailed and a significant decrease inheart rate.All antiarrhythmics, except for small doses ofbeta blocker, were withdrawn. During the nine-yearfollow-up we have found the patient to be in a goodclinical state with a physical condition, presentingneither severe tachycardia nor the AV conductiondisturbances she had experienced formerly.DiscussionInappropriate sinus tachycardia is an uncommonand still poorly defined chronic arrhythmia, whichoccurs in otherwise healthy people with no underly-ing structural heart disease. It is characterized bya positive P wave in II, III and aVF in ECG, typicalimpulse propagation and a high resting heart rate (usu-ally over 100/min), with exaggerated acceleration oneven moderate exertion. This rare disorder occursmainly in young females and may lead to recurrentsyncopal states [5–7]. Its mechanism and anatomicsubstrate are unknown.There are some probable etiologic factors in-cluding the following: enhanced sinus node automa-ticity, automatic right atrial tachycardia in the closedvicinity of the sinus node, a depressed efferent car-diovagal reflex, beta-adrenergic hypersensitivityand excess sympathetic tone as well as a diminishedparasympathetic tone regarding sinoatrial node in-nervation [5, 7]. Although IST is usually consideredan idiopathic disorder, it must be pointed out thatit is frequently observed as a result of atrioventricu-lar nodal re-entry tachycardia and RF ablation of thepara-Hisian accessory pathways [8–10]. This mech-anism probably involves transient parasympatheticdenervation [11]. EP studies carried out in IST cas-es have revealed a physiologic sequence of impulsepropagation, with its earliest activation in the re-gion of the sinus node. Although it is possible todifferentiate between IST and sinus node re-entry,the exclusion of ectopic atrial tachycardia might betroublesome, since the response of both arrhyth-mias to programmed pacing is similar. The manage-ment of IST is still the clinical problem to be solved.Pharmacologic therapy with beta-blockers, calciumchannel blockers, amiodarone and propafenone isempiric and usually not fully efficient [3]. For theremaining group of patients who have failed phar-macotherapy ablation should be considered. Thereis no precise method of verifying ablation efficacy,which is why the effects of both treatment meth-ods, pharmacological as well as non-pharmacologi-cal, remain unsatisfactory.Apart from the more aggressive RF destruc-tion of sinus node function or the AV node withsubsequent pacemaker implantation [12], the publi-cations draw attention to sinus node RF modification[13, 14] with its sophisticated innovations [15, 16] asthe potential therapy of choice in IST. The first de-scriptions of RF sinus node ablation in IST were pub-lished by Waspe et al. [1] and Lee et al. [2] in 1994,and since that time numerous cases have been pub-lished worldwide. To our knowledge, AV conductivedisturbances following sinus node modification havenot previously been reported, although they weredescribed in cases of AV nodal re-entry and bypass-tracts [3, 4]. This and the long distance between theablative electrode and the AV junction make this phe-nomenon difficult to explain. From the theoreticalbackground the conclusion may be derived that thecausative factors for these disturbances can be me-chanical compression of the electrode over the AVjunction and right bundle or transient excess parasym-pathetic or reduced sympathetic tone. The Bezold--Jarish reflex should not be excluded either.Regardless of the exact localization of the ar-rhythmia substrate and its relationship to the sinusnode central zone, the observation of AV block fol-lowing RF application in the high right region isunexpected and difficult to explain.ConclusionIntroduction of a back-up temporary pacing leadprior to supraventricular tachycardia ablation pro-cedures should be considered even in a high atrialRF application.References1. Waspe LE, Chien WW, Merillat JC et al. Sinus nodemodification using radiofrequency current in a pa-tient with persistent inappropriate sinus tachycardia.PACE 1994; 17: 1569–1576.2. Lee RJ, Grogin HR, Fitzpatrick AP et al. Sinus nodemodification for inappropriate sinus tachycardia. J AmColl Cardiol (special issue), 1994: 155A.3. Singh B, Sudan D, Kaul U. Transient complete atrio-ventricular block following radiofrequency ablation507Jacek Bednarek et al., Transient AV block following catheter RF sinus node modificationwww.cardiologyjournal.orgof left free wall accessory pathway. J Interv CardiacElectrophysiol, 1998; 2: 305–307.4. Stamato NJ, Eddy SL, Whiting DJ. Transient com-plete heart block during radiofrequency ablation ofleft lateral bypass tract with right bundle branchblock. PACE 1996; 19: 1351–1354.5. Krahn AD, Yee R, Klein GJ, Morillo C. Inappropriatesinus tachycardia: evaluation and therapy. J Cardio-vasc Electrophysiol, 1995; 6: 1124–1128.6. Lee RJ, Shinbane JS. Inappropriate sinus tachycar-dia: diagnosis and treatment. Cardiol Clin, 1997; 15:599–605.7. Morillo CA, Klein GI, Thakur RK et al. Mechanismof “inappropriate” sinus tachycardia. Role of sym-pathovagal balance. Circulation, 1994; 90: 873–877.8. Brugada P, Simonis F, Tsakonas K et al. Inappropri-ate sinus tachycardia following radiofrequency abla-tion of AV nodal tachycardia: incidence and clinicalsignificance. PACE, 1994; 17: 924–927.9. Ehlert FA, Goldberger JJ, Brooks R, Miller S, Kadish AHPersistent inappropriate sinus tachycardia after radio-frequency current catheter modification of the atrio-ventricular node. Am J Cardiol, 1992; 69: 1092–1095.10. Skeberis V, Simonis F, Tsakonas K, Celiker A,Andries E, Brugada P. Inappropriate sinus tachycardiafollowing radiofrequency ablation of AV nodal tachy-cardia: incidence and clinical significance. PACE,1994; 17 (Part I): 924–927.11. Kocovic DZ, Harada T, Shea JB et al. Alterations ofheart rate and of heart rate variability after radiofre-quency catheter ablation of supraventricular tachy-cardia. Delineation of parasympathetic pathways inthe human heart. Circulation, 1993; 88: 1671–1681.12. Esmailzadeh B, Bernat R, Winkler K et al. Surgicalexcision of the sinus node in a patient with inappro-priate sinus tachycardia. J Thorac Cardiovasc Surg,1997; 114: 861–864.13. Lee RJ, Kalman JM, Fitzpatrick AP et al. Radiofre-quency catheter modification of the sinus node for“inappropriate” sinus tachycardia. Circulation, 1995;92: 2919–2928.14. Jamie B, Conti MD, Kelly J et al. Radiofrequencyablation for inappropriate sinus tachycardia followingsuccessful ablation of atrioventricular nodal reentranttachycardia. Heart Web, 1997; 2: 970– 1003.15. Kalman JM, Lee RJ, Fisher WG et al. Radiofrequen-cy catheter modification of sinus pacemaker functionguided by intracardiac echocardiography. Circulation,1995; 92: 3070–3081.16. Kalman JM, Olgin JE, Karch MR, Lesh MD. Use ofintracardiac echocardiography in interventional elec-trophysiology. PACE, 1997; 20 (Part I): 2248–2262.

Transient atrioventricular block following catheter radiofrequency sinus node modification

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Transient atrioventricular block following catheter radiofrequency sinus node modification

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