Iatrogenic Ventricular Tachycardia fromEndocardial Pacemaker Late After Repair ofTetralogy of FallotWEI LI, BERARDO SARUBBI, and JANE SOMERVILLE*From the fane Somerville GUCH Unit, Royal Brompton & Harefiold NHS Trust, and tbe*Imperial College School of Medicine, London University, the United Kingdom

LI, W., FT AL.: Iatrogenic Ventricular Tachycardia from Endocardial Pacemaker Late After Repair ofTetralogy of Fallot. A 34-year-old woman, who had undergone radical repair for tetralogy of Fallot at theagt ofSyears, was left with moderate-to-severe pulmonary regurgitation. VT developed after endocardialpacing for symptomatic pauses and at rial flutter. The possibility that the new VT originated from the api-cal endocardial lead was suggested by the unusual morphology of the VT, which was similar to paced.Surgical removal of the lead, which was deeply embedded at the same time as a pulmonary valve was re-placed, cured the arrhythmia. This unusual cause of VT highlights possible risks associated with settingup a dangerous reentry circuit by inserting a right ventricular endocardial pacemaker lead. (PACE 2000;23:2131-2134)

ventricular tachycardia, tetralogy of Fallot, pacemaker

IntroductionVentricular tacbycardia (VT) is a known late

complication following surgical repair for tetral-ogy of Fallot. Tbe site of ventriculotomy and in-fundibular resection may provide an anatomicsubstrate for reentrant circuits. ̂ ^ We report a pa-tient with repaired tetralogy of Fallot in wbom anendocardial lead caused serious symptomaticventricular tachycardia that disappeared after sur-gical lead removal.

Case ReportA 34-year-old woman (JG) was diagnosed

with tetralogy of Fallot soon after birtb, bad a leftmodified Blalock-Taussig sbunt at age 2 years forincreasing cyanosis, and a subsequent radical re-pair witb a tran.sannular pericardial patcb at age 8years. At operation, a large coronary artery wasfound to cross tbe right ventricular outflow tractso the pericardial patch was placed beneath tbecoronary artery.

She bad important pulmonary regurgitationwitb a dilated rigbt ventricle (cardiotboracic ratio[CTR] = 60%) but was asymptomatic until age 31.Sbe then presented with rapid palpitation, cbestpain, and dyspnea. Holter monitoring confirmedparoxysmal atrial flutter witb periods of bradycar-

Wei Li is supported by the Fielding Medical Trust.

Address for roprint.s: Wei Li. M.D.. Jane Snmerville GUCHUnit, Royal Brompton & Harefield NHS Trust. Sydney St..London. SW:i 6NP. England. Fax: 0171-351-8604.

Re[:eived October 22, 1999; November 22, 1999; acceptedJanuary 18, 2000.

dia and pauses of up to 2.6 seconds witbout anyventricular arrbythmias. Cardiac catheterizationshowed normal rigbt ventricular pressures [35/0mmHg), no residual ventricular septal defect, nogradient across the rigbt ventricular outflow tract,but gross pulmonary valve regurgitation witb a di-lated and normally functioning rigbt ventricle. Thepauses, although asymptomatic, suggested sick si-nus syndrome. A DDDR pacemaker was insertedplacing a screw-in lead in tbe rigbt atrial ap-pendage and a ventricular lead in the rigbt ventric-ular apex. Five weeks later sbe complained ofsymptomatically more severe palpitations thatwere accompanied by dizziness and cbest pain. Anelectrocardiogram (ECG) event recorder, activatedby the patient, showed broad complex tachycardiawitb a beart rate of 200 beats/min and signs of atri-oventricular dissociation (Fig. 1). Sotalol was inef-fective (up to 240 mg daily) as tbe frequency of at-tacks increased. An episode lasted 5 bours and ledto syncope and emergency electrical cardiover-sion. Tbe 12-lead ECG recorded before conversionsbowed a broad complex tachycardia witb a beartrate of 180 beats/min and a left bundle brancbblock pattern witb a superior axis (Fig. 2). Tbis wasconsidered to arise near tbe rigbt ventricular apex,whicb is not usual in repaired Fallot. Its ouset sosoon after pacemaker insertion implicated thepacemaker itself as the cause. Echocardiogram per-formed after the cardioversion showed a dilatedrigbt ventricle with a ventricular pacing lead lo-cated at tbe apex, no excessive tissue around tbetip of pacing lead, a normal size left ventricle, andgood left and rigbt ventricular function. At an elec-tropbysiological study performed on the following

PACE, Vol. 23 Decemher 2000 2131

LI, ET AL.

00:2310

Figure 1. Broad complex tacbycardia recorded from an eiectrocardiographic (ECG) eventrecorder.

day, it was impossible to induce sustained VT de-spite the use of three ventricular extrastimuli (withcycle length of 600, 400. and 350 ms) at the rightventricular apex adjacent to the pacemaker leadand outflow tract, also using an isoproterenol infu-sion. Finally, with the pacemaker programmed inVVI mode and a pacing rate of 150 beats/min, abroad complex tachycardia with similar morphol-ogy to the clinical arrhythmia was recorded (Fig.3). Therefore, it was decided to remove the ven-tricular load and program the pacemaker to AAIR.This was performed concomitant with pulmonaryvalve replacement. The patient was referred forsurgery for both procedures and no anatomic ab-

normality in the right ventricular apex was foundexcept with a deeply embedded lead. At 3-year fol-low-up she remained asymptomatic and withoutany recorded episode of tachycardia on serial 24-hour Holter studies.

DiscussionVT in adults following repair of tetralogy of

Fallot has been shown to originate from the site ofsurgical resection and ventriculotomy scars,which can provide a potential anatomic substratefor a reentrant ventricular circuit.^"^

In this case there were unusual features sug-gesting that a scar related VT was unlikely. The

2132 December 2000 PACE, Vol. 23

IATROGENIC VT AFTER REPARATIVE SURGERY FOR TETRALOGY OF FALLOT

Figure 2. Broad complex tachycardia recorded on 12-Iead electrocardiogram (ECG) on admissionbefore cardioversion.

morphology of the clinical arrhythmia, althoughnot identical, was similar to that of the pacedventricular beats. VT began only after the pace-maker was implanted and appeared to originatein the vicinity of endocardial lead tip. The ven-tricular scar localized in the right ventricularwall could possibly provide the barrier aroundwhich the tachycardia could circulate.^"'* Pre-sumably, the endocardial pacing lead was in-volved in the occurrence of sustained VT, actingas a trigger factor in a favorahle substrate. Pace-maker-mediated VT is rare in patients withchronically implanted and correctly functioning

pacing systems, in the absence of acute ischemia,hypoxia, or electrolyte imbalance, as the appro-priate sensing functions usually prevent the de-livery of a pacemaker impulse during the vulner-ahle part of the cardiac cycle (T wave).'' VTinitiated by a runaway pacemaker, with the pac-ing rate inappropriately high due to battery fail-ure or malfunction, has been described.'^' Morerare are descriptions of cases in which tachycar-dia was initiated hy correctly timed impulsesfrom normally functioning VVI pacemakers/ orwas induced by the fusion of a pacemaker im-pulse and a ventricular extrasystole.^

Figure 3. Broad complex tachycardia recorded while the pacemaker was programmed in the VVImode and a pacing rate of 150 beats/min.

PACE, Vol. 23 December 2000 2133

LI, ET AL.

We are unaware of any previous case report-ing pacemaker induced VT in patients with con-genital heart disease. The close temporal associa-tion with pacemaker insertion and the absence ofrecurrence of VT after lead removal suggests thatthis explanation is correct. However, the patientalso had pulmonary valve replacement, which re-sulted in improvement of symptoms but unlikelyto have an effect on the arrhythmia. The proar-rhythmic effect of the pacemaker appears to haveheen related to the mechanical effect of the pacingelectrode tip in an already created arrhythmic cir-cuit. It suggests the need for caution and a well-de-fined indication for an endocardial pacemaker insuch patients. Finally, the therapeutic options

used to prevent the occurrence of the lifo-threat-ening arrhythmias in the present case were lim-ited by the requirement for a pacemaker. However,endocardial pacing could be safely limited toatriai pacing so the ventricular endocardial leadwas removed and with elimination of the "poten-tial trigger" the problem ceased.

We conclude that VT late after reparativesurgery for congenital heart disease can occur. It isimportant to consider the possibility that a nor-mally placed endocardial pacing lead may triggerventricular arrhythmia. Caution must be usedwhen implanting a pacemaker in patients with aprevious myocardiai scar and a potential reentrantcircuit.

References1. VViiniKs CA, Sonuirvillt! |. Tricus|)i(l atresia i

and adulls: Current stale and lalu cuinpliciitions. Br Heart | lHtifi;56:535.

2. Dowiiar E. Harris L, Kiniber S. et al. Ventricular tachycarriia aftersnrgit:al repair of tittraiogy of Failot: Results of intraoperative map-ping studies, I Am Coll Cardiol 1992: 20:640.

3. Chinushi M, Aizawa Y. kitazawa H, et al. Clockwise aiid counter-clockwisfi circulation of wavefroiits around an anatomical obstacleas one mechanism of two morphoiogifis nf sustained veiifriculartachycardia in patienls after a correctivi! operation of tetralogy ofFaJlot, PACE 1997: 20:2279.

4. Gillette PC. Yeomen MA, Muliins CE, e( al. Sudden death after re-

pair of tetralogy of Fallot: Electrocardiographir and electrrjphysio-Iogical abnormalities. Circulation 1977; 56:556.

5, Lau CP. Sensors and pacemaker mediated lachycardias. PACE 1991;

Mickley H, Andersen C. Htidmann Nielsen L, Runaway pacemaker;A still existing complication and therapeutic guidolines. Clin Car-diol 19»9; 12:412,Kerbomi U. Borggrefe M, Breithardt G, Pacemaker-induced ventric-ular tachycardia in normally functioning ventricular demand pace-makers. Am I Cardiol 198fl; 63:120,Lefroy DC, Crake T, Davies DW. Ventricular tachycardia: An usualpacemaker-mediated tachycardia. Br Heart J 1994: 71:481.

2134 December 2000 PACE, Vol. 23