Br Heart J: first published as 10.1136/hrt.36.5.516 on 1 May 1974. Downloaded from Atrioventricular dissociation with prolonged QT interval and syncopal attacks in a io-year-old boy R. J. Kernohan and P. Froggatt From the Waveney Hospital, Ballymena, and The Department of Social and Preventive Medicine, The Queen's University, Belfast A case is reported of a io-year-old boy with prolonged QT interval, syncopal attacks, and A V dissociation: a combination not previously described. Diagnosis and therapy are discussed. Two heritable syndromes possibly genotypically On admission the patient appeared healthy, intelli- related and manifesting prolonged QT (or QU) gent, and of normal physique. Birthweight was 2-8 kg interval and TU wave changes, sinus bradycardia, after an uneventful pregnancy and confinement. Pre- syncopal attacks, ventricular arrhythmias, and fre- vious history and findings on systemic examination were sudden are respectively unremarkable. Pulse rate was 5S a minute; blood quently death, recognized pressure go/60 mmHg; and there was a minimal early with (Jervell and Lange-Nielsen, 1957) and with- apical systolic murmur. On x-ray the cardiac silhouette out (Romano, Gemme, and Pongiglione, I963; was normal and cardiothoracic index 0o45. Laboratory Ward, I964) profound childhood perceptive deaf- investigations including full blood examinations, ESR, ness. We report here a case seemingly of the latter serum electrolytes, serum magnesium, calcium and syndrome but with atrioventricular dissociation as phosphorus, and blood glucose, were all normal as was the dominant rhythm. Persistent supraventricular an electroencephalogram and audiogram. arrhythmias are only rarely documented in these The electrocardiogram was abnormal showing atrio- syndromes (James, I967), and moreover the present ventricular dissociation with intermittent ventricular http://heart.bmj.com/ case has other features that further warrant its capture and a characteristically variable prolongation of report. the QT interval (Fig. iA and B). Long runs showed ventricular and atrial rates as, respectively, 52 and 5i a minute. P waves were generally upright in all limb leads but were occasionally inverted in lead III following a Case report QRS complex, possibly indicating intermittent AV nodal dominance with retrograde atrial activation. The QT A 9-year-old boy was admitted to the Waveney Hospital, interval was in the range 048 to 0-54 sec (RR on 26 October a (QT.) Ballymena, 197I, after spell of uncon- interval = i-i5 sec); the 'normal' QT interval (QTc) for on September 26, 2021 by guest. Protected copyright. sciousness while playing in his garden the previous this ventricular rate is o038 sec, as calculated from re- afternoon. His mother (a nurse) found him pale, per- gression equation based on data from a random sample of spiring, and unconscious but with neither convulsive hearing schoolboys in Belfast (Fraser, Froggatt, and movements nor incontinence. His pulse was not pal- Murphy, i964b).' Subtraction gives (QTO- QTC)=o-Io pated. Recovery within 5 minutes was accompanied by to o i6 which is to 8 times the standard facial flushing but without pronounced residual symp- sec, 5 error of toms. There had been brief premonitory dizziness but QTC (=0-02 sec), a highly significant QT prolongation neither pain nor palpitations. Three months previously (P <oooi). while bathing in an unheated swimming pool he had his On the basis of the electrocardiographic findings the first known episode of unconsciousness and was rescued spells of unconsciousness were diagnosed as syncope due by a life-guard. He was unconscious for about 5 min- to ventricular tachyarrhythmia or asystole which have utes and subsequently disorientated for an equal period. been increasingly documented in these syndromes He also had, since December I970, minor episodes with (Jervell, 197I) even when the rate-related QT prolonga- pallor, epigastric discomfort, nausea, headache but no tion is less pronounced than here (Froggatt and James, loss of consciousness, pronounced face flushing during I973). recovery, and residual listlessness. The aetiology was unclear, but these episodes resembled in some ways the 1 QT0 =0.099+0.486 (RR) -0.231 (RR)' +0.0023 (age in ' minor' attacks previously described in these syndromes years). When RR > i.o sec, QT0 may be underestimated but (e.g. Fraser, Froggatt, and James, I964a; Jervell, 1971). to an unimportant extent. Br Heart J: first published as 10.1136/hrt.36.5.516 on 1 May 1974. Downloaded from A V dissociation and prolonged QT interval 517 A AHII L A ^~~A ;;olo B -- - C __ _-__ -r I;-_ 11 11 H III I'l III 11 I . I L II I I -I D e .--Mnm LI- 14 -Al- A I1,--I Ii .- FIG. I (Paper speed is I sec=25 mm). A) Patient. Characteristic tracing (lead III) shows dominant A V dissociation. Long strip averaging gives: ventricular rate 52 a minute, atrial rate 5I a minute, QTo = o-48 sec, QT, = o038 sec, QTo- QTc = o-io sec (P < o-ooi - see text). P waves are upright in all limb leads (except aVR). B) Patient. Further strip (lead II) shows: QTo=0=54 sec; QTc=o038 sec; QTo- QT0=o-i6 sec (P<o-ooi). C) Mother (aged 34). Sinus rhythm at 5i beats a minute (lead II). QTo = 0-47 sec; QT0 (Ljung's (z949) formula) = http://heart.bmj.com/ 0-41 sec; QTo- QT0 = oo6 sec (P < o-oI). D) Sister (aged i3). Sinus rhythm at 74 beats a minute andpronounced sinus arrhythmia (lead Vi). QTo = o045 sec; QT" = 0-36 sec; QTo- QT, = 0o09 sec (P < Ooo0I). Family history a minute, with permanent capture of sinus rhythm on The patient is the third of 4 children (3F; iM) born to one record at a rate of I20 beats a minute (Fig. 2A). The healthy unrelated parents. Information covering kin- QT prolongation, however, increased (Fig. 2B), repli- on September 26, 2021 by guest. Protected copyright. ships up to the third degree gave no history of syncope, cating the (atypical) experience of, for example, Jervell fits, unexplained or untimely sudden death, or deafness. and Lange-Nielsen (1957) with adrenaline. Electrocardiograms of the first-degree relatives were No further syncopal attacks occurred and the patient normal for the father and one sister, but QT prolonga- was readmitted on 5 February I973 for reassessment. Saventrine was discontinued. After days' monitoring tion was pronounced in the mother (Fig. iC) and the 5 eldest sister (Fig. ID) and moderate in the youngest to establish basic patterns and exclude significant arrhythmias, a single bolus of o-6 mg atropine was given sister (QTO - QT =o0o5 sec: P = o-oi), the mother also having sinus bradycardia. intravenously. After 7 minutes, sinus rhythm was re- captured at 80 to go beats a minute and retained for go minutes before runs of AV dissociation recurred as the Therapy sinus rate slowed. QT prolongation also seemingly de- Long-acting oral isoprenaline hydrochloride (Saven- creased: pre-atropine control tracing gave QTo- QTC = trine) was started the day after admission since it in- 0- I2 sec (P < o-ooi) while the average for 7 to 30 minutes creases automaticity of the sinoatrial node, can raise the post-atropine tracings was o-o6 sec (P <o-oi). After ventricular fibrillation threshold in complete AV block further drug-free monitoring Ioo mg (3 mg/kg) of (Linenthal and Zoll, i963), and can shorten the rate- diphenylhydantoin was given intravenously over 5 related QT interval in the QT prolongation syndromes minutes and its effect observed for 3 hours. At 20 min- (e.g. Garza et al., I970) and in the experimental situa- utes, when drug effect should be maximal (Ratshin et al., tion. Electrocardiograms before and after discharge on I971), sinus rate (52 per minute) and sinus arrhythmia 45 mg 'saventrine' 6-hourly, showed persistence of were unaffected, sinus rhythm was only intermittently dominant AV dissociation at sinus rates up to about 70 recaptured, and QT prolongation was only equivocally Br Heart J: first published as 10.1136/hrt.36.5.516 on 1 May 1974. Downloaded from 5I8 Kernohan and Froggatt - viewed in Froggatt and James, I973). Moreover, I 11 I 11 II one parent and two (of three) sibs show QT length- . A . I ening (though without syncope) consistent with A F I "111'r w I Mendelian 'dominant' inheritance as now clearly demonstrated for the Romano-Ward variant (Gale et al., 1970; van der Straaten and Bruins, I973). The AV dissociation is unlikely to be a chance concomitant. Sinus bradycardia (and sinus arrhyth- B mia) are common findings in the QT prolonga- F-T tion syndromes and the results here indicate that the AV dissociation, of the 'interference' or 're- fractory' type, is their electrophysiological sequel. On this hypothesis occasional supraventricular ectopic pacemaking would occur in these syndromes C ol and this has been documented as transient (James, Owllkkmm..4.,-o I967; Froggatt and Adgey, 1974) or, rarely, domi- nant patterns (James, I967) but with persistent FIG. 2 (Paper speed is I sec= 25 mm). A) Patient. retrograde atrial activation, as in the 'diving reflex' Sinus rhythm at 120 beats a minute 4 weeks after in normal subjects (Whayne and Killip, I967). The rhythm here described may be a rarer variant start of 'saventrine' (lead II). QTo = 0-38 sec; QTc= simply 0o30 sec, QTo-QTc=o-o8 sec (P<o ooI). B) response determined by a critical relation between Patient. AV dissociation 4 days after start of 'saven- the absolute and relative rates in the two automatic trine' (lead II). Ventricular rate 6o beats a minute; centres. QTo=0o57 sec; QTc=0o37 sec; QTo-QTc=0-20 The aim of therapy was to prevent further syn- sec (P<o-ooi). This was the longest QT interval cope by increasing and stabilizing sinus node auto- recorded but on 'saventrine' all tracings showed maticity and/or reducing the QT prolongation, the dissociation QTo - QT, in excess of Fig.