journal, i975, bidirectional tachycardia in a child astudy...

British Heart Journal, I975, 37, 339-344.

Bidirectional tachycardia in a childA study using His bundle electrography

D. S. Reid, Michael Tynan, L. Braidwood, and G. R. FitzgeraldFrom the Department of Cardiology, Newcastle General Hospital,Westgate Road, Newcastle upon Tyne

This is a report of a case of bidirectional tachycardia in a 6-year-old girl with no evidence of any structuralabnormality of the heart. The patient had never received digitalis. The arrhythmia appeared to be precipitatedby effort and emotional stress, and could be induced by increasing the heart rate by atrial pacing or iso-prenaline administration. His bundle electrography showed that the arrhythmia was ventricular in origin.This emphasizes the importance of recording an effort electrocardiogram in all children with unexplainedsyncopal episodes, even when the resting electrocardiogram is normal.

Bidirectional tachycardia is an uncommon rhythmdisturbance, the origin and mechanism of which arestill disputed. In the majority of cases it occurs as amanifestation of digitalis toxicity or in the presenceof severe myocardial disease. This report describesthe electrophysiological and haemodynamic findingsin a 6-year-old girl with bidirectional tachycardianot caused by digitalis, but precipitated by effortand emotion.

Case reportA 6-year-old girl was initially seen at another hospital inJune I973 after sudden loss of consciousness which hadlasted for IO minutes. Examination at that time was

normal. A further episode occurred in August I973 whileshe was climbing in a children's playground, and shebecame pale, limp, and remained unconscious for IO to15 minutes. Examination after this episode was againnormal but an electrocardiogram recorded after effortshowed a rapid arrhythmia. She was admitted to thishospital in November 1973. Examination once more wasnormal apart from a short grade 2/6 ejection systolicmurmur localized to the base of the heart.An electrocardiogram (Fig. i) showed sinus rhythm, a

PR interval of o-ii sec, and a normal QRS complexsuggesting pre-excitation of the Lown-Ganong-Levinetype (Lown, Ganong, and Levine, I952). The QT0 was0-42 sec which is on the 75th percentile for a girl of thisage (McCammon, I96I), though the observed QT.

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340 Reid, Tynan, Braidwood, and Fitzgerald

FIG. 2 Electrocardiogram recorded during exercise: a) immediately before exercise sinusrhythm, b) during exercise frequent ventricular extrasystoles, c) onset of the tachycardia,d and e) during the tachycardia there is considerable variation in the QRS morphology frombeat to beat, but in e) there is an episode of bidirectional tachycardia, f) termination of thetachycardia, and g) ventricular extrasystoles persist after termination of the tachycardia, thensinus rhythm without extrasystoles.

exceeded the QT0 calculated from the formula ofFraser, Froggatt, and James (I964) by oo5 second.Chest x-ray showed a' normal cardiothoracic ratio of 52per cent with normal lung fields. Laboratory findings,including serum potassium, thyroid function tests, andurinary catecholamines, were normal. Echocardiographyshowed no structural abnormality of the heart and fromthe echocardiogram ofthe left ventricle, two indices of leftventricular performance - the ejection fraction (Feigen-baum et al., 1972) and the mean velocity of circumferen-tial fibre shortening (mean VCF) (Fortuin, Hood, andCraige, I972) - were calculated. These were normal,the ejection fraction being o076 and the mean VCFiIO circfsec.

Electrocardiographic monitoring over 5 days did notreveal any arrhythmias so an electrocardiogram wasperformed while she was exercising on a bicycle ergo-meter. During this exercise, when the heart rate was I07beats/min. ventricular extrasystoles occurred followed by

a tachycardia with considerable beat-to-beat variation inthe QRS morphology, including at times a clearly definedbidirectional tachycardia (Fig. 2). During this the patientdid not lose consciousness and the tachycardia termin-ated spontaneously. Carotid sinus pressure did notinfluence the tachycardia. On the following day a furtherbrief episode of tachycardia occurred when a doctorapproached to carry out a venepuncture. The heart ratepreceding this episode was not recorded.As the nature and aetiology of the tachycardia were

not clearly defined, and as the electrocardiogram at restsuggested pre-excitation, it was felt that further investiga-tion was indicated.

MethodsCardiac catheterization was carried out under basalanaesthesia using gamma-hydroxybutyric acid. After thehaemodynamic measurements were recorded, cine-



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Bidirectional tachycardia in a child - a study using His bundle electrography 341

angiography was performed in the right anterior obliqueprojection, with injection into the pulmonary artery.From the cineangiogram left ventricular volumes,ejection fraction, and mean velocity of circumferentialfibre shortening were calculated by the methods pre-viously described (Tynan et al., I974).A quadripolar catheter was positioned in the right

atrium, with the distal poles situated in the right atrial-superior vena caval junction. The two distal poles wereused for pacing and the proximal two poles for recordingthe atrial electrogram. A 5 F bipolar (io mm) pacingcatheter was then positioned across the tricuspid valve torecord the His bundle electrogram. The atrial and Hisbundle electrograms and leads I and II were recordedsimultaneously on an Elema Schonander ink jet recorderat various paper speeds.

After recording at the resting heart rate, recordingswere made during atrial pacing at twice diastolic thresh-old at gradually increasing rates from 100 to 200 beats/min. Sinus node recovery time was determined afterpacing at rates of 100 and I20 beats/min for 2 minutes.Isoprenaline was then given in single injections ofI ,ug, 2 jig, and 3 ,ug.

ResultsThe haemodynamic measurements, left ventricularmorphology, and left ventricular function werenormal (Table i). The components ofthe His bundleelectrogram during sinus rhythm and during atrialpacing are summarized in Table 2. The AH timewas shorter than the normal of 60 to I25 msec re-

ported by Roberts and Olley (I972) for childrenunder the age of 7 years, but was within the range of50 to 105 msec reported by Bekheit and her col-leagues (1973) for children of less than I2 years.

During atrial pacing the AH interval lengthened,which excludes atrioventricular nodal bypass, but

TABLE i Results of cardiac catheterization

Pressures Oxygensaturation

Dynamic Mean %

Superior vena cava 75Right atrium a=6

v=3 74X=I 72y=I 3 7I

Right ventricle 20/0-3 73Main pulmonary artery I4/7 II 74Pulmonary artery wedge 7Right femoral artery 104/50 70 95

LVEDV = 78 mi/M2LVESV =30 ml/m2Ejection fraction=o-62Mean VCF = I I7 circumferences/sec

TABLE 2 Measured electrogram intervalsduring atrial pacing and sinus node recoverytime

Heart rate PA AH HV(beats/min) (msec) (msec) (msec)

79 30 50 35I00 50 50 35I20 50 6o 35I30 50 60 35I40 50 70 35I50 50 75 35I60 50 85 35I70 50 85 35I80 50 90 35200 50 I00 35

and 2: i post H block

Sinus node recovery time i20/min= 860 msecioo/min=790 msec

not to the duration normally seen in adults. How-ever, as there are no figures available for childrenit is difficult to be certain whether this responseto pacing is normal or whether it suggests partialAV nodal bypass. The 2: i post-H block duringpacing at 200/min, a response that is not normallyseen during atrial pacing in adults, showed that therefractory period of the atrioventricular nodal path-way was shorter than the refractory period of thespecialized ventricular conduction system. Sinusnode recovery times were normal.The tachycardia could be initiated by atrial

pacing at rates of 130 to I50 beats/min and by iso-prenaline when the rate increased to I I7/min.Atrial pacing at rates below I30 beats/min and above15o beats/min did not initiate the tachycardia. Eachepisode of tachycardia was preceded by ventricularextrasystoles, and the initiating beat was either aventricular extrasystole or a fusion beat with acoupling interval of 330 to 370 msec (Fig. 3).The rate of the tachycardia varied from i62 to

207/min. A His potential was never seen precedingthe ventricular depolarization during the tachy-cardia, unless capture beats or fusion beats wereobserved, confirming the ventricular origin of thetachycardia (Fig. 3). The alternating morphology ofthe QRS in the two standard leads was characteristicof bidirectional tachycardia. However, during someof the paroxysms the morphology of the QRSchanged though the bidirectional nature of thetachycardia persisted.

Retrograde atrial activation was observed onoccasions during the tachycardia, sometimes withWenckebach periodicity, but complete AV dissocia-tion also occurred.



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FIG. 3 A brief episode of bidirectional tachycardia initiated by atrial pacing with recordings ofHis bundle electrograms (HBE), atrial electrogram (AEG), and simultaneously recorded leadsI and II at IOO mm/sec. The first beat is an atrially paced beat, the second beat is a ventricularextrasystole which initiates the tachycardia. The tachycardia terminates spontaneously and isfollowed by an atrially paced beat. The His potential is clearly seen in the two paced beats but notduring the tachycardia. The atrial electrogram shows that the first three beats are atrially pacedbeats, but the next three are caused by retrograde atrial activation (ST - stimulus, A - atrialdepolarization, V - ventricular depolarization, H - His depolarization).

Carotid sinus stimulation had no effect on thetachycardia. Termination occurred spontaneously,usually without alteration in the cycle length of thetachycardia, but on one occasion two spontaneousventricular extrasystoles terminated the tachycardia.

ProgressAfter catheterization practolol was given in adose of 50 mg twice daily, increasing to ioo mgtwice daily. Exercise was again carried out, asdescribed above. The heart rate increased to 120/min and apart from isolated extrasystoles sinusrhythm persisted. During the follow-up period of 3months, she has remained well without any furthersyncopal episodes.

DiscussionThe mechanism and origin of bidirectional tachy-cardia have been disputed since it was first describedby Schwensen in 1922. The main reason for the dis-pute is that, with the standard electrocardiogram,

the distinction of ventricular from supraventriculartachycardia can be difficult, even with the additionalinformation obtained using atrial and oesophagealleads.Rosenbaum, Elizari, and Lazzari (I969) have

recently reviewed the mechanism of bidirectionaltachycardia and have proposed that this arrhythmiais supraventricular in origin with permanent aberra-tion in the right bundle-branch and alternatingaberration in the two divisions of the left bundle-branch. Indirect support for its supraventricularorigin is the association of this arrhythmia withnodal and junctional tachycardia (Zimdahl andKramer, 1947; Zimdahl and Townsend, I954;Castellanos, Azan, and Calvino, I960; Sepaha, Jain,and Bhandari, I962). In this case the presence of ashort PR interval raised the possibility of pre-excitation and of a re-entry tachycardia involvingthe atrioventricular junction. However, His bundleelectrography failed to confirm this and demon-strated in this case, as in the three others studied



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Bidirectional tachycardia in a child - a study using His bundle electrography 343

using this technique (Morris and Zipes, I973;Kastor and Goldreyer, I973; Cohen, Deisseroth,and Hecht, 1973), that the tachycardia was ventricu-lar in origin.

In a recent review of the published cases of bi-directional tachycardia it was shown that themajority occurred in association with severe myo-cardial disease and in 82 per cent digitalis had beenadministered and was thought to be a contributoryfactor in the production of this arrhythmia (Cohenet al., I973). In this case neither digitalis nor myo-cardial disease played a part in the production of thearrhythmia, in fact increase in the heart rate oneffort or with emotional stress appeared to be theimportant precipitating factor. It is interesting thatthe arrhythmia could be reproduced in the catheterlaboratory by atrial pacing or isoprenaline.The appearance of bidirectional tachycardia in

this case is unusual for several reasons. The patientwas very young, had normal heart function demon-strated by angiography and echocardiography, andwas not receiving digitalis, and the arrhythmiaappeared to be precipitated by increasing the heartrate.Although ventricular arrhythmias have been

described during and immediately after effort inpeople with clinically normal hearts, these arrhyth-mias tend to be transient, lasting for 3 to 5 beats(Gooch and McConnel, I970). Emotion and effortare characteristic precipitating factors of theventricular arrhythmias associated with the syn-drome described by Jervell and Lange-Nielson(I957), and in the variant without deafness, theRomano-Ward syndrome (Romano, Gemme, andPongiglione, I963; Ward, I964). However, pro-longation of the QT interval which is an integralpart of these syndromes, was not present in this case.There are, however, isolated reports of childrenwithout organic heart disease and with normal QTintervals who have arrhythmias and syncope pro-duced by effort and emotion (Wennevold, Melchior,and Sand0e, I965; Horan and Venables, I962). Inthe case described by Wennevold and his colleagues(I965), the arrhythmia (their Fig. 3) showed con-siderable variation in the QRS morphology andclosely resembled that seen in this case. This wasalso seen in the case described by Horan andVenables (I962) in which there were runs resemblinga bidirectional tachycardia. In both these cases, as inthis case, the arrhythmia was only demonstrated byrecording an electrocardiogram during or aftereffort. It, therefore, seems advisable to carry outroutine exercise electrocardiograms in children whopresent with unexplained syncopal episodes, especi-ally if these are related to effort or emotion.

This case supports the recent evidence that bi-

directional tachycardia is ventricular in origin.However, the origin of bidirectional tachycardiamay vary from patient to patient and further studiesare required in more patients to define the mechan-ism of the tachycardia and to confirm that bi-directional tachycardia really is a 'ventricular'tachycardia.

ReferencesBekheit, S., Morton, P., Murtagh, J. G., and Fletcher, E.

(I973). Comparison of sinoventricular conduction inchildren and adults using bundle of His electrograms.British Heart3Journal, 35, 507.

Castellanos, A., Jr., Azan, L., and Calvino, J. M. (I960).Simultaneous tachycardia. American Heart Journal, 59,358.

Cohen, S. I., Deisseroth, A., and Hecht, H. S. (I973). Infra-His bundle origin of bidirectional tachycardia. Circulation,47, I260.

Feigenbaum, H., Popp, R. L., Wolfe, S. B., Troy, B. L.,Pombo, J. F., Haine, C. L., and Dodge, H. T. (I972).Ultrasound measurements of the left ventricle. A correla-tive study with angiocardiography. Archives of InternalMedicine, 129, 46I.

Fortuin, N. J., Hood, W. P., and Craige, E. (I972). Evaluationof left ventricular function by echocardiography. Circula-tion, 46, 26.

Fraser, G. R., Froggatt, P., and James, T. N. (I964). Con-genital deafness associated with electrocardiographicabnormalities, fainting attacks and sudden death. QuarterlyJournal of Medicine, 33, 36I.

Gooch, A. S., and McConnel, D. (1970). Analysis of transientarrhythmias and conduction disturbances occurring duringsubmaximal treadmill exercise testing. Progress in Cardio-vascular Diseases, 13, 293.

Horan, M., and Venables, A. W. (I962). Paroxysmal tachy-cardia with episodic unconsciousness. Archives of Diseasein Childhood, 37, 82.

Jervell, A., and Lange-Nielson, F. (1957). Congenital deaf-mutism, functional heart disease with prolongation of theQ-T interval, and sudden death. American Heart journal,54, 59.

Kastor, J. A., and Goldreyer, B. N. (I973). Ventricular originof bidirectional tachycardia. Case report of a patient nottoxic from digitalis. Circulation, 48, 897.

Lown, B., Ganong, W. F., and Levine, S. A. (1952). Thesyndrome of short P-R interval, normal QRS complex andparoxysmal rapid heart action. Circulation, 5, 693.

McCammon, R. W. (I96I). A longitudinal study of electro-cardiographic intervals in healthy children. Acta Paedia-trica (Uppsala), 50, Suppl. I26.

Morris, S. N., and Zipes, D. P. (I973). His bundle electro-cardiography during bidirectional tachycardia. Circulation,48, 32.

Roberts, N., and Olley, P. (I972). His bundle electrogram inchildren. Statistical correlation of the atrioventricularconduction times in children with their age and heart rate.British Heart Journal, 34, I099.

Romano, C., Gemme, G., and Pongiglione, R. (I963).Aritmie cardiache rare dell'eta pediatrica. Clinica Pediatrica,45, 656.

Rosenbaum, M. B., Elizari, M. V., and Lazzari, J. 0. (i969).The mechanism of bidirectional tachycardia. AmericanHeart Journal, 78, 4.

Schwensen, C. (I922). Ventricular tachycardia as the result ofadministration of digitalis. Heart, 9, I99.



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Sepaha, G. C., Jain, S. R., and Bhandari, C. R. (I962). Bi-directional tachycardia. British Heart Journal, 24, 6i.

Tynan, M., Kaye, H. H., Reid, D. S., Ozme, F., and HIunter,A. S. (I974). Assessment of left ventricular performance ininfants, children and adults using single plane cine angio-cardiography (abstract). British Heart Journal, 36, 399.

Ward, 0. C., Jr. (I964). A new familial cardiac syndrome inchildren. J'ournal of the Irish Medical Association, s4, 103.

Wennevold, A., Melchior, J. C., and Sand0e, E. (1965).Adams-Stokes syndrome in children without organicheart disease. Electrocardiogram after exercise as adiagnostic tool. Acta Medica Scandinavica, 177, 557.

Zimdahl, W. T., and Kramer, L. I. (I947). On the mechanismof paroxysmal tachycardia with rhythmic alternation in thedirection of the ventricular complexes. American HeartJournal, 33, 2I8.

Zimdahl, W. T., and Townsend, C. E. (I954). Bidirectionalventricular tachycardia due to digitalis poisoning. AmericanHeart Journal, 47, 304.

Requests for reprints to Dr. D. S. Reid, Department ofCardiology, Newcastle General Hospital, WestgateRoad, Newcastle upon Tyne NE4 6BE.



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