Bundle Brunch Reentrant Ventricular Tachycardia withTwo Distinct Conduction Patterns in a Patient withComplete Right Bundle Branch BlockYOSHIHISA ENJOJI, M.D., MASAHIRO MIZOBUCHI, M.D., KENSAKU SHIBATA, M.D.,TSUYOSHI ONO, M.D., ATSUSHI FUNATSU, M.D., DAISUKE KANBAYASHI, M.D.,TOMOKO KOBAYASHI, M.D., and SHIGERU NAKAMURA, M.D.From the Cardiovascular Center, Kyoto Katsura Hospital, Kyoto, Japan; 17 Yamada Hirao-Cho, Nishikyo-ku,615-8256, Kyoto, Japan

We report a rare case of bundle branch reentrant ventricular tachycardia [BBRVT]. A 67-year-old femalewas admitted for management of wide QRS tachycardia (right bundle branch block [RBBB] and a southwestaxis). The mapping procedure revealed the tachycardia circuit consisted of the left anterior fascicle (LAF)as an antegrade, and the right bundle as a retrograde pathway. She presented RBBB during sinus rhythm.LAF ablation changed the tachycardia configuration to a northwest axis and prolonged the cycle length.Left posterior fascicle ablation terminated the tachycardia, and complete atrioventricular block occurred,which showed the unidirectional conduction over the right bundle. (PACE 2006; 29:1438–1441)

bundle branch reentry, bundle branch block, catheter ablation, pacemaker

IntroductionBundle branch reentrant ventricular tachycar-

dia (BBRVT) usually occurs in patients with struc-tural heart disease.1,2 It may also occur in patientswith conduction disturbances with a structurallynormal heart.3–6 The circuit of BBRVT involvestwo branches: the left bundle branch as an ante-grade pathway and the right bundle as a retrogradepathway or vice versa. Radiofrequency catheter ab-lation is an effective treatment option for BBRVTtargeting either branch.7 We experienced a rarecase of BBRVT, which presented with two distinctconfigurations and cycle lengths during radiofre-quency catheter ablation.

Case PresentationA 67-year-old female was admitted for the

evaluation and treatment of sudden onset wideQRS tachycardia. A 12-lead electrocardiogramshowed right bundle branch block (RBBB) witha normal axis during sinus rhythm and RBBBwith a southwest axis during tachycardia (Fig.1). Ultrasound echocardiography showed a de-creased left ventricular ejection fraction of ap-proximately 40%. An electrophysiological studyand catheter ablation were performed after ob-taining written informed consent. The tachycardiawas reproducibly induced by programmed elec-trical stimuli. Reentrant ventricular tachycardia

Address for reprints: Yoshihisa Enjoji, M.D., Division ofElectrophysiological Lab., Cardiovascular Center, Kyoto Kat-sura Hospital, 17 Yamada Hirao-Cho, Nishikyo-Ku, 619-8256,Kyoto, Japan. Fax: 81-75-382-3199; e-mail: enmomo@nifty.com

Received February 13, 2006; revised April 6, 2006; acceptedMay 8, 2006.

was confirmed by the presence of atrioventricu-lar dissociation (Fig. 2). Catheter ablation was per-formed using a 7 F quadripolar deflectable 4-mmtip electrode catheter (Cardiac Pathway Inc. Sun-nyvale, CA, USA) and a 500 kHz current genera-tor (Central Industry, Chiba, Japan). We mappedthe right ventricle, but the right bundle electro-gram was difficult to record during sinus rhythmdue to the RBBB. We then mapped the left ventri-cle via the femoral artery. The left anterior fascicle(LAF) was activated from proximal to distal. TheHis-ventricular (HV) interval during tachycardiawas 70 ms during tachycardia and 55 ms duringsinus rhythm. Spontaneous changes in LAF po-tential cycle length preceded changes in the ven-tricular cycle length (Fig. 2). Continuous pacing atthe LAF region resulted in concealed entrainment,and a stimulus to the ventricular electrogram in-terval at the pacing site was equal to that of theLAF potential to the local ventricular electrogram(Fig. 2). LAF ablation during tachycardia resultedin a sudden change from RBBB with a southwestaxis to RBBB with a northwest axis. The cyclelength during tachycardia increased from 310 to340 ms (Fig. 3). Following LAF ablation, a 12-leadelectrocardiogram showed RBBB with a northwestaxis during sinus rhythm or tachycardia. The map-ping catheter was then moved to the left posteriorfascicle (LPF) region, and the LPF potential wasactivated from proximal to distal end (Fig. 2). Af-ter obtaining informed consent for implantation ofa permanent pacemaker, we performed LPF abla-tion. LPF ablation terminated the tachycardia, anda complete atrio-ventricular block occurred, whichshowed a complete absence of antegrade conduc-tion over the right bundle (Fig. 3). After LAF andLPF ablation, ventricular tachycardia could not be

C©2006, The Authors. Journal compilation C©2006, Blackwell Publishing, Inc.

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Figure 1. Comparison of each electrocardiogram. Left upper panel: During sinus rhythm beforeLAF ablation. Right upper panel: During VT before LAF ablation. Left lower panel: During sinusrhythm after LAF ablation. Right lower panel: During VT after LAF ablation.

induced by up to three extra stimuli and burst pac-ing to 250 ppm during isoproterenol infusion.

Discussion

Diagnosis of Wide QRS Tachycardia

There are several potential mechanismswhich present with wide QRS tachycardia. Al-though supra-ventricular tachycardia with a ven-tricular conduction disturbance could be ruledout in this case, there was ventriculo-atrial dis-sociation during tachycardia, which excluded thediagnosis of atrioventricular reentrant tachycar-dia with a concealed accessory pathway. Atri-oventricular dissociation during tachycardia inatrioventricular nodal reentrant tachycardia hasbeen reported,8 but is uncommon: in these cases,the QRS configuration during sinus rhythm andtachycardia should be identical. In our patient,the QRS configuration was different during si-nus rhythm and tachycardia, ruling out the di-agnosis of atrioventricular nodal reentrant tachy-cardia with ventricular conduction disturbance.Supraventricular tachycardia with aberrant con-duction should also be considered. In this case,Wenckebach conduction of the atrioventricularnode was 130 beats per minute (bpm) during sinus

rhythm, and the rate of tachycardia was 180–190 bpm. Therefore atrioventricular nodal reen-trant tachycardia with aberrant conduction wasthought to be unlikely. Our patient’s tachycardiahad the following characteristics: (1) The QRScomplex morphology with bundle branch blockpattern was consistent with ventricular depolar-ization through the appropriate bundle branch; (2)Ventriculo-atrial dissociation was present duringtachycardia; (3) A change in bundle branch po-tential cycle length preceded similar changes inthe ventricular cycle length; (4) Complete elim-ination of tachycardia was achieved by bundlebranch ablation. According to these findings, inter-fascicular reentrant ventricular tachycardia (IFVT)and the BBRVT should be distinguished. We firstablated the LAF during tachycardia, which re-sulted in the prolongation of tachycardia cyclelength and changed the QRS axis. If the mecha-nism of firstly induced tachycardia was IFVT, LPFshould be activated from distal to proximal. Themapping catheter was soon moved from LAF re-gion to LPF region, which revealed that LPF alsoactivated from proximal to distal. These findingsare consistent with BBRVT.9 Therefore the mecha-nism of this wide QRS tachycardia was thought tobe BBRVT.

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Figure 2. Intracardiac electrogram during tachycardia. Left upper Panel: Ventriculo-atrial dissociation was observed,which showed the tachycardia mechanism as the ventricular tachycardia. The activation sequence of LAF is fromproximal to distal. Spontaneous changes in the His bundle potential and the LAF potential cycle length preceded thechanges in the ventricular cycle length. Right upper panel: The mapping catheter located at the LPF region after theLAF ablation. The activation sequence of LPF is from proximal to distal. Left lower panel: Concealed entrainmentphenomenon is observed during pacing from LAF region. Ventricular wave at the LAF region is entrained orthodromi-cally, and the stimulus-ventricular wave interval at the pacing site is equal to that of LAF–Ventricular wave. Arrowindicates the LAF or LPF potential. HRA = high right atrium; CS = coronary sinus; HBE = His bundle electrogram;RV = right ventricle.

The Tachycardia CircuitThe circuit of BBRVT involves two branches.

When the left bundle branch is the antegrade path-way, the LAF or the LPF is activated from proximalto distal, and the right bundle from distal to proxi-mal. The LAF or LPF was activated from proximalto distal, showing the left bundle to be the ante-grade limb of this tachycardia circuit. Althoughwe tried to map the right bundle region, it was dif-ficult to record clearly. Therefore it was hard tojudge how the right ventricle was activated. How-ever, the His bundle electrogram recorded at theright ventricular septum was activated from distalto proximal, and entrained after a left ventricularelectrogram. Therefore the right bundle was the

retrograde limb of this tachycardia circuit. Thistachycardia was unique in two ways: First, theconfiguration and cycle length of the tachycardiachanged during LAF ablation. Although the ante-grade limb of the tachycardia circuit switched fromthe LAF to the LPF, tachycardia persisted with thesame mechanism. Second, the right bundle wasutilized as the retrograde limb of this tachycardiacircuit, despite the absence of antegrade conduc-tion over the right bundle.

Limitations of This Study

The strategy of ablation in BBRVT shouldbe targeted at the retrograde pathway. Because it

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Figure 3. Intracardiac electrogram during radiofrequency energy application. Left panel: Radiofrequency energy de-livery to the LAF. Although the QRS configuration changed, and the cycle length prolonged from 310 to 340 ms,tachycardia sustained. Arrow: Change of QRS configuration and the tachycardia cycle length. Right panel: Radiofre-quency energy delivery to the LPF. Tachycardia terminated and the complete atrio-ventricular block occurred.

proved difficult to record the right bundle poten-tial, we first approached the right ventricle andmapped the right bundle anatomically. In this case,antegrade right bundle conduction was absentduring sinus rhythm, which may explain why itwas so difficult to map.

ConclusionWe report a rare case of bundle branch reen-

trant tachycardia with two distinct configurations.The antegrade pathway switched from the LAF tothe LPF, and the tachycardia cycle length changedduring catheter ablation.

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