J. ELECTROCARDIOLOGY 12 (2), 1979, 227-233

Ebstein's Anomaly in Association with Anomalous Nodoventricular Conduction. Pre-Operative and Intra-Operative Electrophysiological Studies BY DAVIDE. WARD,M.B., M.R.C.P., JOHN CAMM, M.B., M.R.C.P., RICHARDCORY-PEARCE, F.R.C.S., IVAN FUENMAYOR, M.D.*, GARETH M. REES, F.R.C.S. AND ROWORTHA.J. SPURRELL, M.D.,F.A.C.C.

SUMMARY A 13 year old girl with Ebstein's anomaly was investigated for refractory paroxysmal tachycardias and ventricular pre-excitation. Intracardiac electrophysiological studies demonstrated that ventricular pre-excitation was due to conduction in an anomalous nodo-ventricular pathway. Tachycardia occurred as a result of re-entry within the A-V node with pre-excitation during tachycardia due to conduction in the nodo-ventricular pathway. These tachycardias were controlled initially by medical therapy but because of increasing frequency of attacks, occasionally requiring D.C. conversion, further electrophysiological studies and epicardial mapping were undertaken. The epicardial surface of the right ventricle and right atrium were mapped during tachycardia. The results of the studies confirmed that a direct anomalous atrio-ventricular pathway was not present and that re-entrant tachycardia did not involve an accessory pathway of this type. A rapid atrial pacing system was implanted and paroxysmal tachycardias have been successfully controlled.

CASE REPORT

The association between Ebstein's anomaly and ventricular pre-excitation is relatively common, in some series reported as high as 25% 1 of patients. This figure m a y be an underestimate because the presence of underlying right bundle branch block m a y mask right ventricular pre-excitation. 2,3 In most cases of Ebstein's anomaly and in all the reports of p a t i e n t s with the a n o m a l y who have had epicardial mapping studies 4,5,6,7,s ventricular pre-excitation has been due to the presence of a right-sided direct atrioventricular connection. M a n y of t h e s e p a t i e n t s suffer from paroxysmal palpitations which m a y be caused by re-entrant tachycardia involving the accessory pathway, or, rarely, by atrial fibrillation with a rapid ventricular response. Where it has been shown that the accessory pathway is involved in a re-entrant circuit or is responsible for a rapid ventricular rate during atrial fibrillation, surgical division of the anomalous p a t h w a y is a curative procedure. H o w e v e r , o t h e r r e - e n t r a n t circuits m a y exist in patients with the Wolff-ParkinsonW h i t e 9,1o,11,12 s y n d r o m e and careful electrophysiological studies are required to distinguish these different mechanisms.

The patient, a 13 year old girl, first presented to hospital in May 1973 with a sudden onset of central chest pain and malaise. The e l e c t r o c a r d i o g r a m (ECG) showed a rapid tachycardia of 180 bpm with broad QRS complexes. Intravenous practolol (3 mg.) had no effect on the tachycardia and she was started on digoxin 0.125 mg. eight hourly, with a gradual reduction in heart rate and eventual termination of the tachycardia. She remained well on prophylactic digoxin until October 1974 when she presented with another attack which required D.C. shock. At that time a tricuspid diastolic m u r m u r was heard and a diagnosis of Ebstein's anomaly was made. In the following year she had several more attacks despite treatment with digoxin 0.125 mg. daily and verapamil 20 mg. t.d.s. Several other anti-arrhythmic agents including disopyramide and amiodarone did not result in control of the attacks. In February 1976 she was admitted for electrophysiological studies and cardiac catheterisation. These studies suggested the presence of a right sided Kent pathway. Atrial pressure recorded simultaneously w i t h v e n t r i c u l a r e l e c t r o g r a m s confirmed the presence of "atrialised" ventricle typical of Ebstein's anomaly. In April 1977, the patient was referred to this hospital for consideration of surgical division of an accessory atrio-ventricular pathway. Electrophysiological studies were repeated and suggested that nodo-ventricular rather than atrio-ventricular anomalous conduction was present. During 1977, a c o m -

From the Cardiology and Cardiothoracic Surgery Departments, St. Bartholomew's Hospital, London, E.C. 1. *Visiting Fellow The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. w 1734 solely to indicate this fact. Reprint requests to: D.E. Ward, Cardiology Department, St. Bartholomew's Hospital, London, E.C. 1.

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Fig. 1. During atrial pacing (SIS0 at a basic cycle length of 500 msec, atrial premature stimuli ($2) are delivered at 440 msec (top left), 380 msec (top right), 290 msec (bottom left), 270 msec (bottom right). HRAE = high right atrial electrogram LAE = left atrial electrogram (recorded via a patent foramen ovale) HBE = His Bundle electrogram AE = atrial echo VE = ventricular echo I, AVF, Vz, V~ = surface electrocardiographic leads Paper speed 100 mm/sec. bination of disopyramide 100 mg. t.d.s, and verapamil 80 mg. t.d.s, resulted in a n imp r o v e m e n t in the p a t i e n t ' s s y m p t o m s but later in the year she suffered further attacks requiring D.C. conversion. In view of persistent tachycardias she was readmitted in April 1978 for further electrophysiological studies. Following these studies it was electively decided to i m p l a n t a p a t i e n t - a c t i v a t e d rapid atrial pacing system to control the tachycardias. During the operation, epicardial mapping was u n d e r t a k e n to confirm the absence of an anomalous atrioventricular pathway. Routine haematological investigations were normal. The chest radiograph showed slight enlargement of the right atrium. The ECGs during sinus r h y t h m revealed normal conduction or i n t e r m i t t e n t incomplete right bundle branch block.

Pre-operative electrophysiological studies were performed as described elsewhere. 1~ At operation, the heart was exposed via a m i d - s t e r n a l incision. The r i g h t a t r i a l and right ventricular myocardium were impaled with a small bipolar hook electrode to act as reference sensing electrodes or pacing electrodes. A hand-held tripolar electrode, with 1.5 m m inter-electrode distances and 1 m m electrode diameter, was used to sample signals from 40 points on the right atrial epicardium and 39 points on the right ventricular epicardium during tachycardia. Normal sinus r h y t h m could not be adequately studied because of frequent interruptions by tachycardia. Epicardial signals were filtered between 50-700 Hz and recorded at 100 mm/sec, together with surface electrocardiographic leads I, III, AVR, and AVL using ah Elema J. E L E C T R O C A R D I O L O G Y ,

VOL. 12, NO. 2, 1979

EBSTEIN'S ANOMALY WITH NODOVENTRICULAR CONDUCTION

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Fig. 2. Anterograde conduction curve. A1-A2 = atrial extrastimulus coupling interval PCL = paced cycle length AE = atrial echo M i n g o g r a f recorder. Rapid atrial stimulation and ventricular stimulation were performed using a Devices 4570 isolated stimulator. Bypass facilities were on standby so that in the event of finding a direct A-V connection, this could be properly treated. I. Pre-operative studies. At the time of study the PR interval was normal during sinus r h y t h m with QRS complexes that were normal or showed a small S wave in lead I. Right or left atrial pacing at increasing rates resulted in prolongation of the A-H interval and A-V interval, associated with increasing preexcitation manifested by a positive delta wave in leads V6 and I, with a small positive initial v e c t o r in V1. The H i s p o t e n t i a l b e c a m e obscured by ventricular electrograms at a pacing cycle length of 375 msec. At a cycle length of 315 msec, A-V Wenckebach conduction was precipitated with gradually increasing A-V i n t e r v a l s . These s e q u e n c e s were consistently terminated by total loss of conJ. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979

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duction to the ventricles. Programmed atrial pacing at a basic cycle length of 500 msec and atrial e x t r a s t i m u l i introduced at progressively shorter coupling intervals resulted in A-H prolongation and A-V prolongation associated with increasing pre-excitation (Fig. 1). At a coupling interval of 360 msec, the His potential became obscured by the ventricular electrogram. At an A1-A2 interval of 270 msec there was sudden prolongation of the A-V interval (Fig. 2), without change in the pre-excited QRS complex morphology and an atrial echo beat occurred with low to high right atrial activation sequence. A ventricular echo followed the atrial echo. A similar sequence of events was observed at shorter coupling intervals of the atrial extrastimulus, b u t no s u s t a i n e d t a c h y c a r d i a s c o u l d be initiated. Programmed ventricular pacing and ventricular extrastimuli resulted in progressive and identical V-A delay of all atrial electrograms b u t again no sustained re-entry was initiated.

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Fig. 3. a. Sustained tachycardia demonstrating a negative H-V interval and right atrial activation preceding left atrial activation. DCSE = distal coronary sinus electrogram PCSE = proximal coronary sinus electrogram b. Atrial extrastimulus at 290 msec. resulting in prolongation of the A-H and A-V intervals. The QRS complex is pre-excited and has the same morphology to that seen during tachycardia. Similar findings were observed at the second electrophysiological study performed at this hospital. However, at this study, sustained re-entrant tachycardias could be initiated by a single ventricular extrastimulus. This t a c h y c a r d i a showed pre-excited QRS complexes identical to those observed during atrial extrastimulation (Fig. 3). Atrial activation during tachycardia was from low to high right atrium. A His potential was clearly visible 20 msec after the onset of the QRS complex. Endocardial atrial mapping d u r i n g t a c h y c a r d i a showed e a r l i e s t right atrial activation in the area of the posteriorsuperior tricuspid annulus. Tachycardia was r e l i a b l y t e r m i n a t e d by r a p i d r i g h t atrial s t i m u l a t i o n at 250-300 bpm. H i s b u n d l e stimulation could not be achieved at either study. II. Intra-operative study. At surgery, right atrial and right ventricular epicardial activation sequences were studied during stable tachycardia. Earliest atrial activation was seen in high and low anterior sites. There was no evidence of eccentric a t r i a l activation spread from the A-V groove. Earliest ventricular activation during pre-excited tachycardia was observed on the anterior surface of the right ventricle near the apex (Figs. 4

and 5). No early activation adjacent to the A-V groove was evident. DISCUSSION I. Pre-operative studies. Paroxysmal tachycardias and ventricular pre-excitation in Ebstein's anomaly is usually due to the presence of right sided direct atrio-ventricular anomalo u s p a t h w a y s . T h e p r e - o p e r a t i v e electrophysiological studies did not suggest that this was the case in this patient. In the presence of this type of accessory pathway, the typical response to incremental atrial pacing or atrial premature stimuli is increasing preexcitation with prolongation of the A-H interval, but constancy of the A-V interval. 14,15 On the contrary, there was significant prolongation of the A-V interval associated with increasing pre-excitation and H-V shortening in response to incremental atrial pacing or atrial extrastimuli. Although delay in a direct A-V accessory p a t h w a y may account for this finding it is extremely unlikely. Furthermore, it is improbable that A-V Wenckebach periods in two anatomically separate pathways would always be terminated by total A-V block in both pathways. 16 Delay within the A-V node proximal to a nodo-ventricular pathway explains the gradual increase in the A-V interval J. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979

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Fig. 4. Sample of recordings from the earliest point of right ventricular epicardial activation. The probe electrogram is registered synchronously with the onset of QRS activity. and further delay distal to the origin of such a p a t h w a y would result in increasing preexcitation. 16 The gradual appearance of broad QRS complexes with progressive shortening of the A1-A2 interval, associated with shortening of the H-V interval makes prematurity related left bundle branch block unlikely. Also, the QRS morphology remained unchanged when the A~-V2 interval suddenly increased from 220 msec to 340 msec (Fig. 1). Although we cannot see the His potential of this complex, it is reasonable to assume that the H~-H2 interval must also be prolonged. This would tend to diminish or abolish prematurity related bundle branch block. Finally, the negative H-V i n t e r v a l d u r i n g t a c h y c a r d i a , c a n n o t be explained by functional left bundle branch block alone. The sudden increase in the A-V interval and the appearance of an atrial echo beat w i t h o u t change in the QRS morphology suggests the presence of dual A-V nodal pathways ~7 proximal to the origin of the acJ. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979

cessory pathway. The presence of a concealed accessory pathway was excluded preoperatively by the response to programmed vent r i c u l a r s t i m u l a t i o n which resulted in a gradual identical increase in the V-A interval of all atrial electrograms, is Eccentric atrial activation during tachycardia19 was not present. The n e g a t i v e H-V i n t e r v a l d u r i n g tachycardia is not consistent with ventricular activation over a direct A-V connection and retrograde conduction to the atria via the His bundle. Although anterograde conduction in a nodo-ventricular pathway and retrograde conduction in the right bundle branch could conceivably account for this short V-H interval, it is most unlikely that this circuit is responsible for the tachycardia since the QRS morphology during tachycardia is identical to t h a t produced by an atrial p r e m a t u r e stimulus resulting in pre-excitation (Fig. 3). A similar argument makes it improbable that the tachycardia emanates from the right bundle branch system with retrograde activation of the His bundle. These observations, taken

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t o g e t h e r with the a n t e r o g r a d e conduction characteristics, suggest t h a t re-entry is located within the A-V node, with pre-excitation of the ventricles occurring as a result of conduction in a nodo-ventricular p a t h w a y which bypasses the distal A-V node - - His bundle region. This mechanism adequately explains the negative H-V interval during tachycardia with broad QRS complexes. II. Intra-operative studies. During stable preexcited tachycardia the earliest epicardial activation of the right ventricle on its anterior surface r e m o t e from the A-V groove w a s simultaneous with the onset of the QRS complex (Fig. 4). From this point, epicardial activation spread towards the A-V groove, apex and posterior interventricular groove. These findings are not typical of ventricular preexcitation by a direct atrioventricular pathway, which, in all published examples studied by epicardial mapping, has resulted in early a c t i v a t i o n of t h e v e n t r i c u l a r m y o c a r d i u m adjacent to the A-V groove. 4'2~ However, our observations are consistent with a nodo-ventricular anomalous p a t h w a y inserting into the right ventricular myocardium near to, or, less likely, directly into the right bundle branch.

Fig. 5. Diagrammatic representation of the unfolded right ventricular epicardial surface. The activation time of each of the 39 points is indicated at the location of the point. The point of earliest activation is arrowed. LAD = left anterior descending artery PDA = posterior descending artery PA = pulmonary artery

Atrial epicardial a c t i v a t i o n during sustained tachycardia revealed a normal retrograde activation sequence with spread towards the postero-lateral right atrium. This is additional evidence that a right-sided concealed accessory pathway is not involved in the retrograde limb of the tachycardia circuit because, unless such a p a t h w a y were situated close to the A-V node, eccentric atrial activation would be evident. The evidence therefore suggests that reentry did not involve any direct atrio-ventricular connection and that pre-excitation was due to a n o m a l o u s c o n d u c t i o n in a nodoventricular pathway. Therefore, surgical intervention in respect of a classical "Kent" pathway was not possible. Rapid atrial s t i m u l a t i o n is an effective m e a n s of t e r m i n a t i n g s u p r a v e n t r i c u l a r re-entrant tachycardias of almost any variety. 21,22,23 In our patient, pre-operative stimulation studies had consistently demonstrated the effectiveness of this technique without inducing atrial fibrillation. A patient-activated radiofrequency controlled rapid atrial pacing s y s t e m ( M e d t r o n i c 5998) w a s t h e r e f o r e implanted. In the published cases of Ebstein% anomaly J. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979

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with Wolff-Parkinson-White syndrome who h a v e u n d e r g o n e e p i c a r d i a l m a p p i n g studies, all h a v e h a d r i g h t - s i d e d direct A - V p a t h w a y s p r o d u c i n g t y p e B p r e - e x c i t a t i o n . I n one of t h e s e r e p o r t s , 24 t h e r e w a s l i m i t e d e v i d e n c e for t h e co-existence of a " M a h a i m " p a t h w a y w h i c h w a s d i s c o v e r e d b y chance i n t r a - o p e r a t i v e l y . E p i c a r d i a l m a p p i n g studies w e r e p e r f o r m e d d u r i n g a t a c h y c a r d i a w i t h left b u n d l e b r a n c h b l o c k p a t t e r n . T h e s e s t u d i e s r e v e a l e d a simil a r a c t i v a t i o n s e q u e n c e to t h a t in t h e p a t i e n t d e s c r i b e d here. L i m i t e d p o s t - o p e r a t i v e studies d e m o n s t r a t e d p h e n o m e n a w h i c h c o u l d be explained by nodo-ventricular conduction but no c o m m e n t s w e r e m a d e a b o u t t h e m e a n i n g of specific findings. This report illustrates another mechanism of p r e - e x c i t a t i o n t h a t m a y occur in E b s t e i n ' s a n o m a l y a n d w h i c h m u s t be d i s t i n g u i s h e d from the classical mechanism of pree x c i t a t i o n . T h i s h a s obvious t h e r a p e u t i c imp l i c a t i o n s if s u r g e r y is to be considered. REFERENCES 1. BIALOSTOZKY, D, HOROWITZ, S AND ESPINOVERA, J: Ebstein's malformation of the tricuspid valve, a review of 65 cases. Am J Cardiol 28:84, 1971 2. ROBERTSON, P G C, EMSLIE-SM1TH, D, LOWE, K G AND WATSON, H: Association of type B ventricular pre-excitation and right bundle branch block. Br Heart J 25:755, 1963 3. FERNANDEZ,F, HELLER,J AND LENEGRE, J: Association de WPW type B avec block de branch droite. Etude electrovectorcardiographique d'un cas. Arch Mal Coeur 60:571, 1967 4. GALLAGHER,J J, GILBERT, M, SVENSON, R H, SEALY, W C, KASSELL, J AND WALLACE, A G: Wolff-Parkinson-White syndrome. The problem, evaluation and surgical correction. Circulation 51:767, 1975 5. KASTOR, J A, GOLDREYER, B N, JOSEPHSON, M E, PERLOFF, J K, SCHARF, D L, MANCHESTER, J H, SELBURN, J C AND HIRSCHFELD, J W: Electrophysiologic characteristics of Ebstein's anomaly of the tricuspid valve. Circulation 52:987, 1975 6. CAMM, A J AND SPURRELL, R A J: Epicardial isochrone mapping in Ebstein's anomaly of the tricuspid valve. (abstract) 3rd International Congress of Electrocardiology, Brussels, 1976 7. KUGLER, J D, GILLETTE, P C, DUFF, D E, COOLEY, D A AND MCNAMARA, D G: Elective mapping and surgical division of the Bundle of Kent in a patient with Ebstein's anomaly who required tricuspid valve replacement. Am J Cardiol 41:602, 1978 8. MCFAUL, R C, DAVIS, Z, GIVLIANI, E R, RITTLER, D G AND DANIELSON,G K: Ebstein's malformation. Surgical experience at the Mayo Clinic. J Thoracic and Cardiovascular Surgery 72:910, 1976 9. MANDEL, W, LAKS, M AND OBAYASHI, K: Atrio-ventricular nodal re-entry in the WolffParkinson-White syndrome. Chest 68:321, 1975

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10. DENES, P AND ROSEN, K M: Dual A-V pathways and pre-excitation. Circulation 50:861, 1974 11. WELLENS,H J J AND DURRER, D: The role of an accessory atrioventricular pathway in reciprocal tachycardia. Circulation 52:58, 1975 12. WARD, D E, CAMM, A J AND SPURRELL, R A J: Re-entrant tachycardia utilizing two bypass tracts and excluding the A-V node in patients with the short PR interval normal QRS complex syndrome. Br Heart J 40:1127, 1978 13. S~URRELL, R A J, THORBURN, C W, CAMM, J, SOWTON, E AND DEUCHAR, D C: Effects of disopyramide on electrophysiological properties of specialised conduction system in man and on accessory atrioventricular pathway in WolffParkinson-White syndrome. Br Heart J 37:861, 1975 14. WELLENS, H J J: Contribution of cardiac pacing to our u n d e r s t a n d i n g of t h e WolffParkinson-White syndrome. Br Heart J 37:231, 1975 15. CASTELLANOS,A, CHAPUNOFF, E, CASTILLO,C, MAYTIN, O AND LEMBERG, L: His Bundle elect r o g r a m s in two cases of Wolff-ParkinsonWhite (pre-excitation) syndrome. Circulation 41:399, 1970 16. WARD, D E, CAMM, A J AND SPURRELL, R A J: Ventricular pre-excitation due to nodo-ventricular pathways - - report of 3 cases. European J Cardiol 9:111, 1979 17. DENES, P, Wu, D, DHINGRA, R, CHUQUIMIA,R AND ROSEN K M: Demonstration of dual A-V node pathways in patients with paroxysmal s u p r a v e n t r i c u l a r tachycardia. Circulation 48:549, 1973 18. WELLENS, H J J AND DURRER, D: Patterns of v e n t r i c u l o - a t r i a l conduction in the WolffParkinson-White syndrome. Circulation 49: 22, 1974 19. PRrrCHETT, E L, GALLAGHER, J J AND WALLACE, A G: Re-entry within the atrioventricular node in man - - a reassessment. European J Cardiol 6:437, 1977 20. CAMM, A J, REES, G M, WARD, D E AND SPURRELL, R A J: Operative treatment of WolffP a r k i n s o n - W h i t e s y n d r o m e (abstract). Br Heart J 40:459, 1978 21. VERGARA, G S, HILDNER, F J, SCHOENFELD, C B, JAVIER, R P, COHEN, L S AND SAMET, P: Conversion of supraventricular tachycardias with rapid atrial stimulation. Circulation 46:788, 1972 22. KAHN, A, MORRIS, J J AND CITRON, P: Patientinitiated rapid atrial pacing to manage supraventricular tachycardia. Am J of Cardiol 38:200, 1976 23. CAMM, J, WARD, D AND SPURRELL, R: The response of regular re-entrant supraventricular tachycardias to right heart stimulation. Presentations of 1st European Symposium on Cardiac Pacing, London, May 1978 24. TONKIN, A M, FORTUNE, D A, SVENSON, R H, SEALY, W C, WALLACE, A G AND GALLAGHER,J J: C o e x i s t e n c e of f u n c t i o n a l K e n t a n d Mahaim-type tracts in the pre-excitation syndrome. Demonstration by catheter techniques and epicardial mapping. Circulation 52:193, 1975

Ebstein's anomaly in association with anomalous nodoventricular conduction. Pre-operative and intra-operative electrophysiological studies.

J. ELECTROCARDIOLOGY 12 (2), 1979, 227-233 Ebstein's Anomaly in Association with Anomalous Nodoventricular Conduction. Pre-Operative and Intra-Operat...
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