Refinement of surgical techniques for the treatment of congenital heart disease (CHD) has created

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1 Eletrophysiology ARRHYTHMIAS IN ADULTS WITH CONGENITAL HEART DISEASE John K Triedman *383 Correspondene to: John Triedman MD, Department of Cardiology, Children s Hospital, 300 Longwood Avenue, Boston, MA 02155, USA; triedman@ ardio1.th.harvard.edu CLINICAL Heart 2002;87: Refinement of surgial tehniques for the treatment of ongenital heart disease (CHD) has reated a new population of young adults with heart disease. In the USA, it is estimated that there are nearly one million CHD patients, 15 20% with disease of severity to warrant surgial intervention. As surgial mortality has fallen, the number of adults living with major ongenital heart defets has inreased. 1 Arrhythmias ompliate the are of many adults with CHD. Their prevalene and the diffiulty of treatment have made arrhythmia a major fous of interest for physiians working in this area. The presene of longstanding CHD in an arrhythmia patient signifiantly alters the nature and potential severity of the arrhythmia omplaint and the safety and feasibility of various treatments. In addition to analysis of the targeted arrhythmia omplaint, the physiian must have omplete and speifi knowledge of the patient s ardiovasular anatomy and the onsequenes of that anatomy and subsequent surgial modifiations on ardiovasular funtion. The arrhythmogeni substrate in adults with CHD is omplex. All arrhythmias prevalent in the normal population may also our in CHD, and some speifi assoiations are observed for example, Wolff-Parkinson-White syndrome and Ebstein s anomaly. However, more ommon are aquired arrhythmias that are rarely seen in normal young adult hearts, and that are assoiated with longstanding hypertrophy and fibrosis aused by yanosis, hroni haemodynami overload, and superimposed surgial sarring. These arrhythmias inlude re-entrant atrial and ventriular tahyardias, heart blok, and sinus node dysfuntion. This artile will review the evaluation and management of these more ommon arrhythmia problems in adults with CHD. BACKGROUND Although the anatomial lassifiation of ongenital heart defets is omplex, three major ategories onstitute a large perentage of adult CHD patients with arrhythmia, beause of their frequeny and high inidene of arrhythmia (fig 1). The spetrum of linial onsequenes of arrhythmia in adults with CHD ranges from linially oult arrhythmia to sudden death. Inessant or reurrent arrhythmia may ause gradual haemodynami deterioration, and vie versa, often resulting in a viious yle of linial deompensation. Thrombosis 2 and thromboemboli events are also assoiated with tahyardia. Symptoms, frequent need for hospitalisation, and the management of ardia devies and antiarrhythmi drugs onstitute a signifiant burden on quality of life. In the era of effetive automati implantable ardioverter-defibrillator (AICD) therapy, assessment of risk of ardia sudden death is an important omponent of linial arrhythmia management. Patients with aquired heart disease an now be segregated into large, relatively homogeneous groups of similarly elevated risk (for example, patients in the first year after myoardial infartion, or with depressed ejetion fration). In ontrast, CHD populations are small, anatomially diverse, and have relatively low rates of sudden death, with annual mortality in even high risk groups in the range of < 2%. 34 Thus, it is diffiult to identify speifi risk fators in CHD and to measure the effet of interventions on survival. Nonetheless, some linial markers appear to affet outomes adversely over a wide range of anatomial defets, inluding the presene of residual haemodynami defets, performane of surgial repair later in life, and longer duration of follow up. At the other extreme of linial presentation, not all adults with CHD and arrhythmia are symptomati, and some experiene symptoms so subtle that the amount of the day spent in tahyardia is not easily quantified. A major area for future researh will be a larifiation of the natural history of arrhythmia in these patients, with attention paid to their role in the gradual deterioration of older patients with CHD. ATRIAL TACHYCARDIAS Intra-atrial re-entrant tahyardia Intra-atrial re-entrant tahyardia (IART) denotes maroreentrant atrial tahyardias other than ommon atrial flutter ourring in the normal heart. Rare in normal hearts, IART is a ommon late

2 384 * Mustard and Senning proedures Patients born with transposition of the great vessels in the 1970s through the early 1990s were palliated by the onstrution of intra-atrial baffles using either syntheti material (the Mustard proedure) or by folding and augmentation of the atrial wall (the Senning proedure). Both rediret aval and pulmonary venous blood to orret yanosis, utilising the right ventrile as the systemi ventrile. These operations have largely been abandoned in favour of the arterial swith proedure. Fontan proedures Many ongenital heart defets have in ommon anatomial features that prelude surgial septation of the ventriles resulting in univentriular physiology. The ommon end point of staged surgial palliation is the Fontan proedure, whih utilises the single ventrile as the systemi ventrile and sends blood diretly from the systemi veins to the pulmonary arteries. Several approahes to this have been used; urrently, an anastomosis between the superior vena ava and pulmonary artery is reated, with an interaval onnetion effeted by tube graft or intra-atrial baffle. Repaired Tetralogy of Fallot (TOF) The prevalene of TOF, its potential for survival through hildhood without operation, and the early date at whih reparative surgery beame available have resulted in large group of patients with relatively homogenous linial experiene. Repair involves losure of the ventriular septal defet (VSD) and relief of right ventriular obstrution, often requiring both ventriulotomy and atriotomy. Figure 1 Congenital heart malformations ommonly assoiated with arrhythmia. ompliation in many varieties of CHD. Like atrial flutter, it tends to have a stable yle length and P wave morphology, suggesting that it is organised by a fixed substrate. Its prevalene among patients who have undergone surgial proedures involving extensive atrial dissetion and repair indiates a partiular dependene on surgial injury, 5 and animal models expliitly patterned after surgeries assoiated with IART (for example, the Mustard and Fontan proedures) result in tahyardias similar to those observed linially. Frequently identified risk fators for IART inlude older age at operation and longer follow up. About half of those patients with old-style Fontans onnetion of the entire right atrium to the pulmonary artery by anastomosis or onduit will develop IART within 10 years of surgery, 6 while onstrution of a lateral right atrial tunnel and avopulmonary onnetion are at lower risk. 7 It is antiipated that the extraardia Fontan, performed using an interaval tube graft, may also be low risk, but arrhythmia has been reported in early follow up of those patients. 8 Survivors of the Mustard and Senning proedures are at risk for the development of sinus node dysfuntion and IART, often onurrently. IART is more prevalent in patients with repaired tetralogy of Fallot (TOF) than ventriular tahyardia, and more likely to be assoiated with symptoms. 9 The first large follow up study of IART after CHD surgery revealed a mortality rate over 6.5 years of 17%, with 10% experiening sudden death. More reently, a group of patients with atrial tahyardias and a prior surgial history of Fontan, Mustard or Senning proedures reported sudden ardia death in 6% over an average follow up of three years. The linial fators assoiated with sudden death were ongoing Figure 2 Ehoardiographi image of a large thrombus identified in the giant right atrium of a patient with an old-style Fontan proedure using an atriopulmonary anastomosis. and/or poorly ontrolled tahyardia episodes and overall poor linial status. 5 Reports of stroke after ardioversion of IART in CHD patients are rare. However, intravasular and intraardia thromboses are assoiated with IART, and a prevalene of intraardia thrombi in 42% of patients undergoing ehoardiography before ardioversion has been reported (fig 2). 2 It is not lear whether atrial tahyardias atually promote suh events, or are merely a onomitant problem ourring in patients with sik, prematurely aging hearts. Drug treatment Although some small studies have suggested otherwise, linial experiene generally has shown that antiarrhythmi drug

3 Abbreviations AICD: automati implantable ardioverter-defibrillator AV: atrioventriular IART: intra-atrial re-entrant tahyardia CHD: ongenital heart disease TOF: tetralogy of Fallot VT: ventriular tahyardia *385 treatment is unlikely to suppress reurrenes of IART. Experimental models of atrial re-entry have given us a good understanding of the potential salutary effets of lass 1C and lass 3 drugs, and symptomati arrhythmias an sometimes be suppressed in individual patients using these agents. However, proarrhythmia and adverse effets on ventriular and nodal funtion may limit their value. Novel antiarrhythmi drugs with pure lass 3 ativity have not been widely used in IART, and may prove useful. The frequent ourrene of thrombosis in adult patients with CHD and atrial tahyardia suggests that warfarin or other potent antioagulant treatment is indiated in most of these patients. Atrioventriular (AV) nodal bloking drugs may also be used, but are often diffiult to titrate beause of the relatively slow yle length and fixed ondution ratios often seen in IART. Paemaker therapy Atrial antibradyardia paing alone sometimes results in symptomati improvement and dereased tahyardia frequeny. 10 In patients with sinus node dysfuntion, this may be the result of improved haemodynamis with appropriately timed atrial ativation. Automati antitahyardia paing has also been of value for some patients. The overall effiay of atrial paing is variable, and there are signifiant tehnial diffiulties assoiated with lead plaement in these patients. Few endoardial or epiardial sites are generally available and able to generate sensed eletrograms of suffiient quality to ensure reliable atrial sensing. Endovasular plaement of atrial leads may also inrease risk of thrombosis. The potential of other innovative devie therapies urrently being developed for treatment of atrial fibrillation, suh as dual site paing and the atrial defibrillator, has not been explored in CHD. Catheter ablation A proposed urative approah to IART has been to extend or reate lines of ondution blok, using atheter based and/or surgial tehniques. This anatomial approah to treatment involves the design of a lesion or lesions based on an understanding of the relation of maroreentrant iruits to the underlying ardia anatomy. It has preedents in the atheter and surgial ablation proedures for ventriular tahyardia (VT) and the maze proedure for atrial fibrillation. Aute suess rates reported for radiofrequeny atheter ablation for IART range from 55 90%. 11 Catheter ablation proedures usually target individual maroreentrant iruits, seeking a vulnerable site for appliation of a radiofrequeny lesion. Review of IART ablation experiene has shown that, in patients with a right AV valve, the isthmus between that valve and the inferior vena ava ommonly supports IART, similar to ommon atrial flutter. 12 When this isthmus is present, as is the ase in patients with Mustard and Senning proedures, TOF, and other biventriular repairs, tehniques developed for atrial flutter may be used to perform and assess the effetiveness of the ablation. Even in these familiar anatomies, however, the Figure 3 Eletroanatomial map in right anterior oblique view of an intra-atrial re-entrant tahyardia iruit onstruted in a patient with an older variant of the Fontan proedure. Ativation times are olour oded to indiate the movement of the wavefront in this tahyardia, indiated by the white arrow. The white shaded area indiates an area of sarring and ondution blok, inferred from harateristis of eletrograms reorded from that region. observation of multiple IART iruits is ommon, and other anatomial or surgial features relevant to ablation may be diffiult to loate fluorosopially. It may also be diffiult to generate the large and onfluent lesions sometimes needed to interrupt these iruits. Appliation of reently introdued mapping and ablation tehniques, suh as advaned ativation mapping tehnologies, and appliation of irrigated radiofrequeny lesions, is assoiated with improved aute suess rates. Longer term follow up after ablation has revealed that arrhythmia symptoms and quality of life are improved in most patients after IART ablation, but reurrenes are doumented in almost half of these patients. 13 Further advanes in our understanding of the arrhythmia substrate and the tehnology available to visualise and modify it will be neessary to improve this important linial outome (fig 3). Surgial treatment Attempts to revise old style Fontan patients to avopulmonary type onnetions for haemodynami reasons are assoiated with perioperative mortality in the region of 10%, 14 and in the absene of speifi intervention for arrhythmia do not reliably prevent arrhythmia reurrene. More reent reports of right atrial maze proedures performed with surgial and/or ryoablative tehniques and employing an empiri set of lesions have shown promising results, with no linially signifiant arrhythmia reurrene in the majority of patients. 15 This suggests that maze revision of Fontan proedures an be performed at a reasonable surgial risk and may greatly redue reurrene of postoperative IART. Additional follow up studies are needed to asertain long term haemodynami and arrhythmia benefit.

4 386 * Long term survival r = 0.27 %/year until 25 years po 0.75 n = 490 p = Time after proedure (years) r = 0.94 %/year after 25 years po Figure 4 Survival urve in late follow up of adult patients with tetralogy of Fallot. Most deaths were sudden; inreased mortality in late deades of follow up has also been observed in other series. Reprodued from Nollert et al 4 with permission of the publisher. Atrial fibrillation Atrial fibrillation ours in as many as 25 30% of patients with CHD and atrial tahyardia. The limited information available on these patients suggests that those with residual left sided obstrutive lesions or unrepaired heart disease are more prone to atrial fibrillation. Priniples of management are drawn from the general adult population, inluding antioagulation and rate ontrol. Risk of thromboembolism is presumably elevated. Sinus rhythm is haemodynamially preferred in CHD, and ardioversion, prophylati antiarrhythmi drugs, and atrial paing are used to prevent the establishment of permanent atrial fibrillation if possible. The ourrene of atrial fibrillation in patients who also have IART redues the likelihood that ablation will be benefiial, and may prompt onsideration of a surgial maze proedure, though the effiay of this approah to atrial fibrillation in CHD has not yet been reported. Use of internal atrial defibrillators and ablation of foal atrial fibrillation in the pulmonary veins have not been explored in CHD. VENTRICULAR ARRHYTHMIAS Considerable data are available on the natural history data of ventriular arrhythmias and linial outomes among patients with TOF, beause of its prevalene in the adult CHD population and elevated inidene of ventriular arrhythmia. Mapping studies have shown that, similar to IART, VT in TOF involves a maroreentrant iruit dependant on an anatomial obstale, in this ase the right ventriular outflow trat path and/or the onal septum. 16 The long term prognosis for patients with repaired TOF is exellent, with nearly 90% survival at 30 years. 4 Sudden death and VT our with a reported inidene of 1 2% over five years for young adults and an overall prevalene of sudden ardia death of 3 6% (fig 4). 417 Although linial presentation of adult TOF patients with sustained monomorphi VT is unommon, suh VT is induible by programmed stimulation in 15 30% of patients, and half have frequent and omplex ventriular etopy on ambulatory ECG. 20 Sinus node dysfuntion and IART our in 20 30% of patients with repaired TOF, and in up to 50% of symptomati patients, 9 often mimiking VT symptoms and/or ausing wide omplex tahyardias. These issues make it diffiult to apply standard diagnosti tools to sreen individuals with linial arrhythmia symptoms for inreased risk of sudden death. Although patients with Mustard, Senning, and Fontan proedures experiene atrial tahyardias and premature mortality, they do not appear to be partiularly prone to VT. Data on VT prevalene in other defets are limited. Patients with valvar aorti stenosis, pulmonary stenosis, and ventriular septal defet have been noted to have frequent ventriular etopy. Aorti stenosis has the highest risk of sudden death among these lesions, but mortality in this defet is haraterised by severity of outflow trat obstrution, rather than arrhythmia. Risk stratifiation Simple models of risk stratifiation for sudden death (for example, ejetion fration) do not exist for adult CHD patients. Assessment of the risk of sudden death aused by ventriular arrhythmia requires an understanding of the limited preditive values of ommonly used diagnosti tests in this population. Although Holter, exerise testing, and programmed ventriular stimulation are useful for provoking and/or reording linially doumented arrhythmias, their value as sreening tests is unlear. Risk assessment is further ompliated by the ourrene of atrial tahyardias, whih may also ause symptoms and sudden death. Several linial features are assoiated with VT and sudden death in adult CHD patients, inluding older age, older age at repair, and poorer haemodynami status. Eletroardiographially, pronouned prolongation of QRS duration and prolongation dispersions of the QT and JT intervals poorly understood indies of ventriular repolarisation are assoiated with ardiomegaly, mortality, and induible sustained VT in TOF patients. 21 These findings identify a more arrhythmogeni myoardium and suggest that both depolarisation and repolarisation are abnormal in high risk TOF patients. Beause of the ubiquity of lower grades of ventriular etopy in this population, ambulatory ECG is often abnormal, and in the absene of signifiant runs of VT it may be of limited value in disriminating patients at elevated risk. The value of programmed ventriular stimulation in patients with CHD is unlear. In one large series evaluating programmed stimulation in patients with a variety of defets, induibility of VT predited subsequent ardia arrest and mortality after adjustment for ovariate linial fators, but also emphasised the importane of areful seletion of patients for study on the basis of those linial features. 22 In another study of adults with TOF, no patients who subsequently died suddenly had induible VT. 18 Both false positive studies 19 (induible VT in patients without VT or mortality on follow up) and false negative studies (non-induibility of patients with doumented sustained VT) our with appreiable frequeny. Management Minimally symptomati patients with non-sustained ventriular etopy must be evaluated to determine whether an assoiated evolution of underlying abnormal haemodynamis or metabolism has ourred. If not, periodi linial monitoring and non-invasive assessment (ECG, eho, and Holter monitoring) are probably suffiient. Event monitoring may be useful for investigation of arrhythmia symptoms. More ominous arrhythmia presentations suh as synope, near synope with palpitation or non-sustained VT should trigger more omprehensive inquiry, inluding atheterisation with haemodynami assessment and programmed atrial and ventriular stimulation. Patients with negative studies, minimal symptoms, and good haemodynamis are managed without treatment, or by using drugs with a favourable side effet

5 profile (suh as β blokers) to suppress symptomati etopy. Supraventriular tahyardia is treated with ablation when possible, and severe bradyardia managed with paing. Patients with severe symptoms or induible VT are onsidered for more aggressive antiarrhythmi drug treatment and AICD plaement (fig 5). Antiarrhythmi drugs may be useful for suppression of symptomati ventriular arrhythmias, but have not been shown to prolong survival in CHD. AICD therapy is feasible in many patients with CHD, and its use is inreasing. Catheter ablation of VT has been suessful in small series of patients with CHD, and may be appropriate for patients with sustained, monomorphi VT that is haemodynamially tolerated. 23 When patients warrant surgery for haemodynami reasons, attempts to reset potential ritial zones for VT may be onsidered. Reently, indiations have broadened for pulmonary valve replaement in patients with symptoms and/or signs of right heart failure and pulmonary regurgitation many of whom also have prolonged QRS duration on ECG. The effet suh surgial intervention may have on ventriular arrhythmia is unknown. *387 BRADYCARDIA Sinus node dysfuntion Gradual loss of sinus rhythm ours after the Mustard and Senning and all varieties of Fontan proedures. 24 Patients with heterotaxy syndromes, partiularly left atrial isomerism, may also have ongenital abnormalities of the sinus node independent of the effets of their surgial proedures. Paroxysmal atrial tahyardias are frequently assoiated with sinus node dysfuntion, and loss of sinus rhythm appears to inrease risk of sudden death. Eletrophysiologial study of patients with the Mustard proedure have identified a variety of abnormalities of atrial eletrophysiology, inluding prolonged sinus node reovery times, intra-atrial ondution times, and atrial refratoriness. 25 Diret surgial injury to the sinus node has been proposed as a ause of observed abnormalities of sinus node funtion. However, the progressive loss of sinus rhythm observed over extended follow up implies additional ongoing pathophysiologial proesses related to hroni haemodynami abnormality. AV blok Interventriular ondution abnormalities, partiularly right bundle branh blok, are very ommon after surgery for CHD. Complete postoperative heart blok is aused either by diret surgial injury to the speialised ondution system or by indiret damage due to inflammatory response. It is typially assoiated with surgial manipulation of the ventriular septum. Patients at highest risk are those undergoing surgery for left ventriular outflow trat obstrutions and patients with ventriular inversion (L-transposition of the great arteries), but it is also ommon after ventriular septal defet and TOF repairs. Review of linial outomes before ardia paing systems appropriate for CHD patients were available showed that postoperative heart blok had a high mortality rate, even in the presene of an esape rhythm. Complete heart blok also ours spontaneously in patients with ertain strutural heart defets, espeially endoardial ushion defets and ventriular inversion. This may be aused by aberrant anatomy of the AV node and His bundle in these patients, rendering them vulnerable to injury. Although some of these patients present with heart blok at birth, it may progress at any stage of life. Figure 5 Radiograph illustrating a variety of tehnial issues with paemaker plaement in a patient who has undergone the Mustard proedure. The ventriular paing lead is loated in the apex of the left ventrile (LV apex), and the atrial lead in the mouth of the left atrial appendage (LA app). Both traverse the superior limb of the Mustard baffle between the superior vena ava and the left atrium, whih was stenoti and required stenting (blak arrows) to relieve obstrution before lead plaement. The presumed loations of the lateral margin of the intra-atrial baffle, defining the pulmonary venous atrial hannel (neo-la) and the ommuniation between left and right atria, are highlighted in white. Paemaker issues While heart blok is a lear indiation for permanent ardia paing in CHD, others are less well substantiated. Many patients with CHD tolerate hroni bradyardia well, but paing may alleviate symptoms suh as fatigue, dizziness, or synope in some patients with juntional esape rhythms, severe resting bradyardia, hronotropi inompetene, and/or prolonged pauses. Paing may also be neessary to permit treatment with antiarrhythmi drugs. Cardia paing in adults with CHD presents a variety of speial hallenges (fig 5). Congenital and aquired ardiovasular abnormalities and shunting may limit opportunities for endoardial lead plaement and neessitate an epiardial or even a hybrid approah. Examples inlude patients with old transvenous lead systems who may have assoiated aquired vasular abnormalities, and Fontan patients, in whom the ventriular avities and muh or all of the atrial myoardium are surgially exluded from systemi venous pathways. Patients with the Mustard and Senning proedures may reeive transvenous dual hamber paing systems, and even AICDs, but the leads must navigate the superior limb of the intra-atrial baffle, whih is prone to obstrution. Atrial lead plaement in unusual sites may be diffiult and must avoid inadvertent stimulation of the phreni nerve. Beause asynhronous atrial paing may provoke IART, areful lead site seletion resulting in exellent sensing of atrial eletrial ativity is important. Clinial experiene shows the value of AV synhrony and favours implantation of a system apable of providing a physiologial heart rate response. However, the speifi value of rate responsive and dual hambered paing as ompared to

6 388 * Arrhythmias in adults with CHD: key points Although long term survival and linial outomes for adults with ongenital heart disease (CHD) are generally good, arrhythmias are a signifiant ause of morbidity and mortality in this group of patients, espeially in later deades of follow up Strategies for individual risk assessment are limited, but groups at partiular risk for arrhythmia inlude patients with the Mustard and Senning proedure for transposition of the great vessels, patients with the Fontan proedure, and patients with repaired tetralogy of Fallot In most forms of CHD, atrial tahyardias appear to be more prevalent than ventriular tahyardias, frequently symptomati, and assoiated with an inreased risk of thrombosis and death Interventional strategies are urrently in development for treatment of atrial and ventriular tahyardia in patients with CHD, and inlude innovative appliations of atheter based and surgial ablative proedures, and antitahyardia and defibrillator devie therapies simpler paing modalities is not well established in CHD. Pratial limitations often require that the hoie of system be adapted to patient speifi problems faed with lead plaement and maintenane. Exploration of the potential utility of new devie tehnologies in CHD, suh as dual site paing for ventriular resynhronisation and atrial defibrillators, will further hallenge the inventiveness of physiians aring for these patients. CONCLUSION Our understanding of arrhythmia in adults with CHD has progressed rapidly, through inreased appreiation of the extended natural history of these patients and innovative appliation of treatments designed for and tested in patients without CHD. Patients with these tahyardias have poor outomes, but the small size and anatomial diversity of this group make it diffiult to determine whih patients are most at risk and whether arrhythmia ontrol will lead to measurable gains in longevity and health. Animal models and the appliation of evolving therapeuti tehnologies have provided us with valuable insights into the anatomial substrates of arrhythmia in this group, and helped to understand some of the problems with preventing their reurrene. Development of a more omplete piture of the underlying pathophysiologial hanges in the myoardium that lead to these arrhythmias will help to fous further efforts to improve our urrent therapeuti outomes. Dislosure of potential onflit of interest: Dr Triedman is a onsultant for Biosense-Webster, In. REFERENCES 1 Boneva RS, Botto LD, Moore CA, et al. Mortality assoiated with ongenital heart defets in the United States: trends and raial disparities, Cirulation 2001;103: Feltes TF, Friedman RA. Transesophageal ehoardiographi detetion of atrial thrombi in patients with nonfibrillation atrial tahyarrhythmias and ongenital heart disease. J Am Coll Cardiol 1994;24: Gelatt M, Hamilton RM, MCrindle BW, et al. Arrhythmia and mortality after the Mustard proedure: a 30-year single-enter experiene. J Am Coll Cardiol 1997;29: A large single entre study of long term outomes revealed ongoing loss of sinus rhythm and late peaks in the risk of atrial flutter and death in patients with the Mustard proedure. 4 Nollert G, Fishlein T, Bouterwek S, et al. Long-term survival in patients with repair of tetralogy of Fallot: 36-year follow-up of 490 survivors of the first year after surgial repair. J Am Coll Cardiol 1997;30: Long term follow up of patients who have survived repair of TOF reveal risk fators for early demise, and inreased mortality in later deades of follow up. 5 Garson A Jr, Bink-Boelkens MTE, Hesslein PS, et al. Atrial flutter in the young: a ollaborative study in 380 ases. J Am Coll Cardiol 1985;6: This report was the result of a joint effort by the Pediatri Eletrophysiology Soiety and represents the first large sale effort to haraterise the natural history of atrial tahyardia in survivors of CHD. 6 Fishberger SB, Wernovsky G, Gentles TL, et al. Fators that influene the development of atrial flutter after the Fontan operation. J Thora Cardiovas Surg 1997;113:80 6. One of three large, single entre follow up studies of Fontan arrhythmia outomes whih doumented the progressively inreasing risk of IART after Fontans and identified linial risk fators for its ourrene. 7 Stamm C, Triedman JK, Mayer JE, et al. Long-term results of the lateral tunnel Fontan operation. J Thora Cardiovas Surg 2001;121: Ten year follow up was obtained in patients who had undergone lateral tunnel reation and total avopulmonary onnetion, onfirming the impression that Fontans reated in this way were less prone to early development of IART. 8 Shirai LK, Rosenthal DN, Reitz BA, et al. Arrhythmias and thromboemboli ompliations after the extraardia Fontan operation. J Thora Cardiovas Surg 1998;115: Roos-Hesselink J, Perlroth MG, MGhie J, et al. Atrial arrhythmias in adults after repair of tetralogy of Fallot. Correlations with linial, exerise, and ehoardiographi findings. Cirulation 1995;91: Although prior studies emphasised the importane of ventriular arrhythmias in TOF patients, this group identified atrial arrhythmias as the main soure of morbidity, ourring in one third of adult postoperative patients. 10 Rhodes LA, Walsh EP, Gamble WJ, et al. Benefits and potential risks of atrial antitahyardia paing after repair of ongenital heart disease. PACE 1995;18: Collins KK, Love BA, Walsh EP, et al. Loation of autely suessful radiofrequeny atheter ablation of intra-atrial reentrant tahyardia in patients with ongenital heart disease. Am J Cardiol 2000;86: Effetive atheter ablation sites in patients with biventriular repairs of CHD were most ommonly loated in the avotriuspid isthmus, while Fontan patients were more likely to be suessfully ablated on the atrial free wall. 12 Chan DP, Van Hare GF, Makall JA, et al. Importane of atrial flutter isthmus in postoperative intra-atrial reentrant tahyardia. Cirulation 2000;102: Triedman JK, Bergau DM, Saul JP, et al. Effiay of radiofrequeny ablation for ontrol of intra-atrial reentrant tahyardia in patients with ongenital heart disease. J Am Coll Cardiol 1997;30: Follow up of patients treated for IART with atheter ablation showed that suessful ablation redued the frequeny of IART symptoms and need for treatment, but half had at least one IART reurrene within six months. 14 Marelletti CF, Hanley FL, Mavroudis C, et al. Revision of previous Fontan onnetions to total extraardia avopulmonary anastomosis: a multienter experiene. J Thora Cardiovas Surg 2000;119: Deal BJ, Mavroudis C, Baker CL, et al. Impat of arrhythmia iruit ryoablation during Fontan onversion for refratory atrial tahyardia. Am J Cardiol 1999;83: This is the first ase series of signifiant size that demonstrates that surgial maze lesions delivered to the right atrium during Fontan revision proedures an prevent the subsequent reurrene of IART in many patients. 16 Horton RP, Canby RC, Kessler DJ, et al. Ablation of ventriular tahyardia assoiated with tetralogy of Fallot: demonstration of bidiretional blok. J Cardiovas Eletrophysiol 1997;8: Murphy JG, Gersh BJ, Mair DD, et al. Long-term outome in patients undergoing surgial repair of tetralogy of Fallot. N Engl J Med 1993;329: Chandar JS, Wolff GS, Garson AJ, et al. Ventriular arrhythmias in postoperative tetralogy of Fallot. Am J Cardiol 1990;65: This large, multientre retrospetive study of patients with postoperative TOF investigated the relations between ventriular etopy disovered by ambulatory monitoring, induibility of VT at atheterisation, and ardia outomes. 19 Luron H, Maron F, Bosser G, et al. Indution of sustained ventriular tahyardia after surgial repair of tetralogy of Fallot. Am J Cardiol 1999; 83: Cullen S, Celermajer DS, Franklin RC, et al. Prognosti signifiane of ventriular arrhythmia after repair of tetralogy of Fallot: a 12-year prospetive study. J Am Coll Cardiol 1994;23: Gatzoulis MA, Till JA, Redington AN. Depolarization-repolarization inhomogeneity after repair of tetralogy of Fallot: the substrate for malignant ventriular tahyardia? Cirulation 1997;95: This and earlier reports from the same group assoiate prolongation and variability in resting ECG intervals with inreased risk of ventriular arrhythmia and death, and propose possible pathogeneti mehanisms to link the two.

7 22 Alexander ME, Walsh EP, Saul JP, et al. Value of programmed ventriular stimulation in patients with ongenital heart disease. J Cardiovas Eletrophysiol 1999;10: A single entre retrospetive analysis of the utility of programmed stimulation alone and in ombination with other linial fators for risk stratifiation of ardia arrest in patients with CHD. 23 Gonska BD, Cao K, Raab J, et al. Radiofrequeny atheter ablation of right ventriular tahyardia late after repair of ongenital heart defets. Cirulation 1996;94: While other ase reports had doumented the feasibility of VT ablation in patients with CHD, this artile reports the first patient series of substantial size and establishes that aute outomes similar to IART ablation may be expeted. 24 Duster MC, Bink-Boelkens MT, Wampler D, et al. Long-term follow-up of dysrhythmias following the Mustard proedure. Am Heart J 1985;109: In long term follow up of patients with the Mustard proedure, sinus node dysfuntion is a frequent and progressive problem. 25 Vetter VL, Tanner CS, Horowitz LN. Eletrophysiologi onsequenes of the Mustard repair of d-transposition of the great arteries. J Am Coll Cardiol 1987;10: *389