intermittent bundle branch blocks in a patient with uncommon-type atrioventricular nodal reentrant...

Journal of Electrocardiology Vol. 32 No. 1 1999

I n t e r m i t t e n t B u n d l e Branch Blocks in a Pa t i en t With U n c o m m o n - T y p e Atr ioventr i cu lar N o d a l R e e n t r a n t

Tachycardia and E n h a n c e d Atr ioventr i cu lar N o d a l C o n d u c t i o n

K e n z o Hi rao , M D,* Ke i Yano , MD,* T o m o e H o r i k a w a , MD,*

K o u S u z u k i , MD,* M i h o k o K a w a b a t a , MD,*

K a t s u h i k o M o t o k a w a , MD,* F u m i o S u z u k i , MD,*

T o k u h i r o K a w a r a , MD,]- a n d K a z u m a s a H i e j i m a , MDJ-

Abstract: We report on a patient with uncommon-type atrioventricular (AV) nodal reentrant tachycardia with a short tachycardia cycle length (235-270 ms), in whom transient wide QRS tachycardia with both left bundle branch block and right bundle branch block aberrancy were followed by narrow QRS complexes. In addition, His-ventricular (H-V) block and a sudden prolongation of the H-V interval occurred during the tachycardia. As the determinant of these unusual findings, the possibility that the anterograde limb of the reentry circuit has an enhanced AV nodal conduction property is discussed, as is the clinical significance of this type of tachycardia. Key words: uncommon-type AV nodal reentrant tachycardia, enhanced AV nodal conduction, bundle branch block, His-ventricular block, radiofrequency catheter ablation.

The development of bundle branch block, espe- cially left bundle branch block (LBBB), during atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is unusual (1). In this paper, we describe an uncommon-type AVNRT patient who had both LBBB and right bundle branch block (RBBB) QRS

morphology during sustained tachycardia. The possibility of the involvement of enhanced AV nodal conduction as an anterograde limb in the reentrant circuit is discussed in regard to the mechanism of this rare electrophysiological phenomenon and the clinical significance of this type of tachycardia.

From the *First Department of Internal Medicine and ~-Department of Allied Health Sciences, School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan.

Reprint requests: Kenzo Fiirao, MD, First Department of Internal Medicine, School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan.

Copyright © 1999 by Churchill Livingstone ® 0022-0736/99/3201-0009510.00/0

Case Report

A 26-year-old man with paroxysmal palpitations was referred for electrophysiological study and catheter ablation. He had experienced frequent

65

66 Journal of Electrocardiology Vol. 32 No. 1 January 1999

episodes of palpitations for the past 3 years. One of these episodes resulted in syncope. There was no evidence of organic hear t disease on an echocardio- gram. The electrocardiogram (ECG) at admission showed a relatively short PR interval (120 ms) but no ventricular preexcitat ion during sinus rhythm.

An electrophysiological study was performed in the postabsorptive state while the patient was se- dated with fentanyl and midazolam. Four quadri- polar electrode catheters (7-French, Cordis-Web- ster, Baldwin Park, California), each separated by 2 m m or 5 mm, were inserted percutaneously into the right and left femoral veins and posit ioned in the right atrial appendage, right ventricular apex, region of the His bundle, and the posteroseptal right a t r ium be tween the coronary sinus ostinm and tricuspid annulus. A 5-French octapolar deflectable electrode catheter (Cordis-Webster, Baldwin Park, California) was inserted into the right internal

jugular vein and posit ioned in the coronary sinus. The five multipolar electrode catheters were used for the p rogrammed stimulation and recordings of intracardiac electrograms. The electrograms includ- ing surface ECG were recorded using an EP Lab computer system (Quinton Electrophysiology Co., Toronto, Canada) with digital amplifiers. The heart was stimulated at twice the diastolic threshold current level with a pulse durat ion of 2 ms. During para-Hisian pacing, the catheter was moved to the right ventricular septum, close to and distal to the His bundle, which was stimulated with up to 10 mA of h igh-output current (2,3).

During sinus rhythm, the atrial-His (A-H) and His-ventricular (H-V) intervals were 50 and 50 ms, respectively. As shown in Figure 1, three types of QRS morphology were observed during the electrophysiological study. The AV conduct ion curve was cont inuous and the tachycardia with QRS morphol-

II

Ill

aVa

aVk

aVF

V1

V2

V 3

V4

V5

V6

Narrow QRS tachycardia

i i ! i

i2,1.

i;ii - • . , • •

• : . : : : : - , . . . . . . : = :

• " : - : . : : : i ; : - ..... i..! ~ i.;!-'.!~ ......... i~ :.~.i.i~ .......... ; i2i

.i.i.i.~.! :.~,~.:.:..i.!.i.i ~.!.i..... :.::~.:.:.i i.i.i..

- + . . q p. . . . .

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i:~.: ~ E . i . ! . i . i . i

Wide QRS tachycardia (LBBB)

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II ~ II

III Ill

aVR aVR

aVL aVL

aVE aVE

V1 V1

V2 V2

V3 V3

V4 V4

V5 V5

V6 V6

Wide QRS tachycardia (RBBB)

. . . . J!iSij!ii! !iJi i!ill i Hi I!HI i!i

2201min 255/min 240Imin

Fig. 1. Three types of tachycardia. Leftpanel: The ECG shows narrow QRS morphology tachycardia. The negative P wave was recognizable in leads II, III, and aVF just before the QRS complex, suggesting that this is long RP tachycardia. Middle panel: Complete left bundle branch block (LBBB) aberrancy QRS morphology was seen during the tachycardia, and the P wave was not identifiable. Right panel: The ECG shows a complete right bundle branch block (RBBB) QRS morphology. The negative P wave was present at a time point a slightly later than the midpoint between QRS complexes.

A

V1

RAA

HBE

PS

CSp

CSm

CSd

Uncommon AVNRT With Enhanced AV Nodal Conduction

Wide QRS tachycardia (LBBB)

I I I 200ms

• Hirao et al. 67

B I

II

V1

S Wide QRS tachycardia (LBBB) | Narrow QRS tachycardia

RAA

HBE

PS

CSp

CSm

CSd ' - A

I I I 200ms

Fig. 2. Induction and transformation of the tachycardia. (A) Induction of tachycardia: An atrial extrastimulus at an A1A2 interval of 220 ms, which produced an AV nodal conduction to the ventricle with a relatively short A-H interval, which produced an AV nodal echo resulting in sustained wide QRS tachycardia with LBBB. (B) Transformation from LBBB complex tachycardia to narrow QRS tachycardia: A single ventricular extrastimulus delivered during tachycardia with LBBB induced a normalizat ion of QRS morphology. Note that the tachycardia cycle length measured from the interatrial potentials stayed the same both during wide QRS tachycardia with LBBB and narrow QRS tachycardia. During the narrow QRS tachycardia, the atrial potential at the posterior septum, indicated by asterisks, preceded the other atrial potentials. Abbreviations: I, II, V1, surface electrocardiographic leads; RAA, HBE, PS, CSp, CSm, CSd, the intracardiac electrogram recorded from the right atrial appendage, His bundle, posterior septum, the proximal, middle, and distal coronary sinus; S 1 $2; basic and extrastimulus pacing artifacts; A1, A2, atrial responses to S 1 and $2; HI, H2, His bundle responses to S1 and $2; V1, V2, ventricular responses to S1 and $2.


Wide QRS tachycardia (RBBB) Wide QRS tachycardia (LBBB)

I

V1

RAA

HBE

,A 240 t 240 I 240 I 240 l 240 I 240 I 240 t 240 [ 240 A 240

A 100 ~.A 90 tl I A 90 Ip ~A 90 ll LA

1 A

CSp

Fig. 3. Spontaneous conversion of QRS morphology from RBBB to LBBB during wide QRS tachycardia. During tachycardia with RBBB, the H-V intervals prolonged gradually, resulting in H-V block as shown in the figure, but the tachycardia did not terminate and the different QRS morphology (LBBB) began without a change in the cycle length of the tachycardia. These findings indicate that these two patterns of tachycardia (RBBB and LBBB) are the same and are not AV reentrant tachycardia because of tachycardia sustainability despite the H-V block occurrence. Abbreviations are the same as those in Figure 2.

ogy of LBBB was induced with a mild prolongat ion of the A-H interval during atrial extrast imuli (Fig. 2A). The anterograde Wenckebach cycle length was 210 ms, and there was no evidence of anterograde conduct ion over an accessory pa thway at any pacing cycle length. The high Wenckebach rate as well as the short PR interval suggested the presence of enhanced AV nodal conduction. The ventriculoatrial conduction curve was continuous and the earliest site of atrial activation during ventricular extrastimuli was located at the His bundle region (anterior septum) with all of the ventricular coupling intervals. No AV nodal echo was induced during ventricular extrastimuli. A sep- tally located accessory pa thway was ruled out by the para-Hisian pacing method (2,3).

The wide QRS tachycard ia w i th LBBB was t r a n s f o r m e d to n a r r o w QRS tachycard ia by the in t roduc t ion of a single p r e m a t u r e ven t r i cu la r s t imulus w i t h o u t changing the t achycard ia cycle length, AH and HA intervals or the atr ial act iva-

t ion sequences as s h o w n in Figure 2B. Therefore , this t achycard ia was a sup raven t r i cu l a r t achycar - dia (SVT) and the wide QRS tachycard ia wi th LBBB was i n t e rp re t ed as SVT wi th abe r r an t conduct ion. The wide QRS tachycard ia wi th RBBB aber rancy , wh ich was also induced, t r a n s f o r m e d to t achycard ia wi th LBBB w i t h o u t a change in the t achycard ia cycle l eng th or the atrial ac t iva t ion sequences (Fig. 3), indicat ing tha t b o t h pa t t e rns of wide QRS tachycard ia we re SVT wi th different ly abe r r an t conduc t ion . As s h o w n in Figure 3, the t achycard ia was sus ta ined despi te the spon- t aneous occur rence of H-V block, and the tachycardia cycle length was no t affected by the changes of H-V intervals . This indica ted tha t o r t h o d r o m i c AV r e e n t r a n t t achycard ia could be comple t e ly ru led out. Dur ing the SVT, ven t r i cu la r pac ing cap tu red the atr ia r e t rograde ly wi th the same atrial ac t iva t ion sequences , and the first r e t u rn cycle of the SVT was similar to the pac ing

II

V1

RAA

HBE

PS

CSp

CSm

CSd

Uncommon AVNRT With Enhanced AV Nodal Conduction • Hirao et al. 69

Narrow QRS tachycardia RV burst pacing:pcl=230 ms Narrow QRS tachycardia

S S S S S S S S S S S S S S

I l l 200 ms

Fig. 4. Entrainment of the tachycardia. The narrow QRS tachycardia was present in the first three complexes at a cycle length of 260 ms. Subsequently, ventricular pacing began at 230 ms with retrograde capture of the atrium from the fifth ventricular extrastimulus. Since the first return cycle of the tachycardia was 260 ms when the pacing was discontinued, entrainment of the tachycardia was demonstrated.

cycle length, as s h o w n in Figure 4. We thus cons idered tha t the SVT was en t ra ined by ventr icular pacing, and that atrial tachycardia could be ru led out as its m e c h a n i s m (4). The cycle length of SVT was 235 to 270 ms, wi th a con- s tant ly short A-H in terval (70 ms) and long H-A intervals (165-200 ms) and the earliest atrial act ivat ion site dur ing the SVT was the posteroseptal r ight a t r ium. Based on these findings during tachycardia , the tachycardia was diagnosed as u n c o m m o n - t y p e (fast/slow form) AVNRT.

Burst pacing from the right a t r ium at the cycle length up to 230 ms entrained the tachycardia and the QRS morphology was conver ted from nar row QRS to wide QRS with LBBB, accompanied by the H-V prolongation. This was also seen during the atrial p remature stimuli in t roduced f rom the coronary sinus, as shown in Figure 5. The atrial prema- ture stimulus, fol lowed by the next His bundle potential with the same A-H interval.

Radiofrequency catheter ablation was then performed to cure this tachycardia by targeting the slow pathway. The pair of distal electrodes of the ablation 7-French catheter (Osypka "Cerablate," Dr.

P. Osypka, Grenzach-Whylen, Germany) was placed be tween the coronary sinus and the tricuspid annulus to record a large ventricular potential and a small atrial potential containing high-fre- quency components during sinus rhy thm. Using the radiofrequency generator (HAT 300, Dr. Osypka), energy (500 kHz, unmodula ted current) was delivered be tween the tip electrode of the catheter and an adhesive electrosurgical dispersive pad during sinus rhythm. Six applications of radio- f requency current with the preselected tempera ture (55°C) achieved the goal of noninducibil i ty of tachycardia. Following this ablation, not even a single AV nodal echo was induced at any A1A2 interval and A1A2A3 interval during single or double atrial extrastimulus tests before and after an isoproterenol infusion. Al though ventricular pacing was not per formed after the ablation, the presence of retrograde slow pa thway conduct ion was not demonst ra ted during the atrial single and double extrastimulus tests. The PR, A-H, and H-V intervals after ablation were the same values as those just before ablation. The patient has been free f rom


Narrow QRS tachycardia

II 250 250 250 280 260 250 255 250

V1 A A A A

RAA A A A , As f . ~

HBE

PS

CSp

csrn

L C S d / ~ - - - ~ - t

As

A ~p~s A

r ~ r T "I-

I I I 200 m s

Fig. 5. Sudden prolongation of the H-V interval by the introduction of an atrial extrastilnulus. Following a single atrial extrastimulus introduced form the coronary sinus ostium, the H-V interval was abruptly prolonged from 90 ms to 135-140 ms, but the length and QRS morphlogy of the tachycardia did not change. Since the H-A and A-H intervals did not change at all, the H-V prolongation resulted in a shortening of the V-A interval on HBE, and the RP interval changed from long to short on the surface ECG. Abbreviations: As, Hs, Vs, the responses of the atria, His bundle, and ventricle, respectively, to a single atrial extrastimulus.

tachycardia attacks for a fol low-up period of 9 months .

Discussion

We have described a pat ient wi th fas t / s low-form AVNRT, in w h o m wide QRS tachycardias wi th both LBBB and RBBB aberrant in t raventr icular conduc- t ion were observed to t ransform to a n a r row QRS tachycardia. The possibility that the anterograde limb of the reent ry circuit has an enhanced AV nodal conduct ion p roper ty was speculated as the de te rminan t of these unusua l p h e n o m e n a . Because u n c o m m o n - t y p e AVNRT with enhanced AV nodal conduct ion has not been previously repor ted to our knowledge, we discuss its electrophysiological characteristics as well as clinical significance.

The short PR interval and the high Wenckebach rate during atrial pacing suggest the presence ot enhanced AV nodal conduct ion (5,6). Since the A-H interval increased gradually during the atrial extrast imulus test, such an accessory p a t h w a y by- passing the AV node complete ly as an atrio-Hisian bypass tract was excluded as a cause of the enhanced AV nodal conduct ion in this patient. C o m -

m o n - t y p e AVNRT, utilizing a fast p a t h w a y with enhanced AV nodal conduct ion as a retrograde limb, has been repor ted by several investigators (6 -8 ) . Benditt et al. repor ted that the cycle length of AVNRT in patients wi th L o w n - G a n o n g - L e v i n e syndrome was 294 _+ 60.4 ms, 60 ms shorter than that in the control group (6), probably because not only retrograde conduct ion over the fast p a t h w a y but also anterograde conduct ion over the slow p a t h w a y have been described to be enhanced (7).

Bundle branch block and prolongat ion of the H-V interval at short intervals of atrial activity are re- garded as associated features of enhanced AV nodal conduct ion (10). Patients wi th AVNRT appear to have a lower incidence of bundle b ranch block at the onset of the tachycardia than do pat ients wi th AV reen t ran t tachycardia ma in ly because of the difference of tachycardia cycle length (1,10,11). It was repor ted that only 2 of 141 AVNRT patients studied developed LBBB aber rancy following induction by extrast imuli (1). Befeler et al. described a L o w n - G a n o n g - L e v i n e syndrome case showing bundle b ranch block during atrial fibrillation with rapid ventr icular response (200 -250 /min ) ( 12 ), We therefore speculated that enhanced AV nodal conduction could be closely related wi th the bundle

Uncommon AVNRT With Enhanced AV Nodal Conduction • Hirao et al. 71

branch block or H-V block observed during AVNRT in this pa t ient and that the m e c h a n i s m of these p h e n o m e n a could be expla ined by the far bet ter conduct ion p roper ty of the AV nodal conduct ion system compared to that of the infranodal conduc- t ion system, as described below. The QRS morpho l - ogy t rans format ion f rom wide QRS tachycardia wi th LBBB to n a r r o w QRS tachycardia by a single ventr icular extrast imulus m a y have been caused by a peeling back of the refractory period of the left bundle b ranch (13,14). Changes in the refractory periods in the I:Iis-Purkinje sys tem during tachycardia made the tachycardia wi th RBBB t rans form to that wi th LBBB via a H-V block. More interestingly, following induct ion by an atrial extrast imulus during the na r row QRS tachycardia, the H-V interval was marked ly pro longed by an impulse enter ing into the His-Purkinje sys tem that exceeded its refractory period, which did not change tachycardia cycle length but induced a shor tening of the RP interval and a lengthening of the PR interval wi th an HA/AH interval similar to that recorded before the atrial extrast imulus.

Clinically, a tachycardia wi th short cycle lengths and t endency of wide QRS complex tachycardia as observed in this case should be t aken into account for t r ea tmen t or diagnosis, because syncope or hypo tens ion could occur during an AVNRT attack; an electrophysiological test would be necessary to proper ly identify the tachycardia m e c h a n i s m for catheter ablat ion or an t ia r rhy thmic drug therapy.

In conclusion, unusua l p h e n o m e n a were observed at the His-Purkinje system level (ie, bundle b ranch block and H-V prolongat ion) resulting f rom the short refractory per iod of the AV node and shorter cycle length during the tachycardia of this patient. This type of tachycardia requires more careful diagnosis and t r ea tmen t than AVNRT with no rma l AV nodal conduct ion properties.

References

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2. Jackman WM, Beckman ICJ, McClelland JH et ah

Para-Hisian RV pacing for differentiating retrograde conduction over septal accessory pathway and AV node. Padng Clin Electrophysiol 14:670 (abstr), 1991

3. Hirao K, Otomo K, Wang X et ah Para-Hisian pacing: a new method for differentiating retrograde conduction over an accessory AV pathway from conduction over the AV node. Circulation 94:1027, 1996

4. Vassallo JA, Cassidy DM, Josephson ME: Atrioven- tricular nodal supraventricular tachycardia. Am J Cardiol 56:193, 1985

5. Gallagher J J, Scaly WC, Kasell J, Wallace AG: Mul- tiple accessory pathways the infranodal conduction system, as described below. The QRS morphology in patients with the pre-excitation syndrome. Circula- tion 54:571, 1976

6. Benditt DG: Characteristics of atrioventricular conduction and the spectrum of arrhythmias in the Lown-Ganong-Levine syndrome. Circulation 57:454, 1978

7. Ward DE, Bexton RS, Carom A: Characteristics of atrio-His conduction in the short PR interval, normal QRS complex syndrome. Evidence for enhanced slow pathway conduction. Eur Heart J 4:882, 1983

8. Bauernfeind RA, Ayers BF, Wyndham RC et ah Cycle length in atrioventricular nodal reentrant paroxysmal tachycardia with observations on Lown- Ganong-Levine syndrome. Am J Cardiol 45:1148, 1980

9. Ward DE, Camm AJ: Pre-excitation. p. 97. In Ward DE, Camm AJ (eds): Clinical Electrophysiology of the Heart. Edward Arnold, London, 1987

10. Wellens H J J, Duffer D: Supraventricular tachycardia with left aberrant during supraventricular tachycardia in man. p. 453. In Zipes DP, Jalife J {eds): Cardiac Electrophysiology and Arrhythmias. Grune & Strat- ton, Orlando, I968

11. Zipes DP, De Joseph RE, Rothbaum DA: Unusual properties of accessory pathways. Circulation 49: 1200, 1974

12. Befeler B, Castellanos A, Aranda J et al: Intermittent bundle-branch block in patients with accessory atrio- His or atrio-AV nodal pathways: variants of the Lown-Ganong-Levine syndrome. Br Heart J 38:173, 1976

13. Langendorf R: Newer aspects of concealed conduction of the cardiac impulse, p. 410. In Wellens HJJ, Lie RI, Janse MJ (eds): Conduction System of the Heart. Stenfert Kroese B.V., Leiden, 1976

14. Wellens HJJ, Durrer D: The role of an accessory atrioventricular pathway in reciprocating tachycardia. Circulation 52:58, I975

intermittent bundle branch blocks in a patient with uncommon-type atrioventricular nodal reentrant...

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