7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Official reprint from UpToDate www.uptodate.com 2023 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Atrial arrhythmias (including AV block) in congenital heart disease : Samuel Asirvatham, MD, Heidi M Connolly, MD, FACC, FASE, Christopher J McLeod, MB, ChB, PhD : Hugh Calkins, MD, Charles I Berul, MD : Susan B Yeon, MD, JD, FACC All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Jun 2023. This topic last updated: Dec 08, 2022. INTRODUCTION One of the striking successes in caring for patients with congenital heart disease (CHD) over the last few decades is the improved longevity. Over one million adults with CHD are now living in the United States [1-4]; up to half having undergone at least one open heart surgical procedure resulting in one or more residual atrial scars [5,6]. For the purposes of this topic, CHD does not include bicuspid valves. As a consequence of both the added longevity and the atrial scarring from surgical procedures, atrial arrhythmias are increasingly recognized in this group. They are a major cause of hospital admission and morbidity in patients with CHD [7-9]. These rhythm abnormalities may be poorly tolerated and are associated with an almost 50 percent increase in mortality compared with those patients without atrial arrhythmias [9]. Although all forms of atrial bradycardia and tachycardia can adversely affect patients with CHD, there are particular considerations in this group because of the anatomy and prior surgical repairs. Although some arrhythmias are intrinsic to the cardiac maldevelopment itself, most are secondary to surgical scars and chronic hemodynamic burden. This review will focus on the management of these arrhythmias ( table 1), which should involve a comprehensive multidisciplinary approach. https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 1/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate PREVALENCE AND INCIDENCE Excluding bicuspid aortic valve, around 1 percent of infants are born with congenital heart disease (CHD) ( table 2), with minor reported racial differences in the United States [10]. Many of the congenital cardiac lesions (45 percent) are classified as simple forms, such as atrial septal defects (ASD) and ventricular septal defects (VSD); moderate forms of CHD such as tetralogy of Fallot occur less commonly, and complex CHD occurs infrequently [11]. The epidemiology of CHD is discussed in detail elsewhere. (See "Identifying newborns with critical congenital heart disease", section on 'Epidemiology'.) The abnormal hemodynamics associated with CHD (through atrial stretch and concomitant fibrosis) exaggerates an arrhythmogenic milieu and increases the likelihood of atrial arrhythmias over time. (See "Isolated atrial septal defects (ASDs) in children: Classification, clinical features, and diagnosis" and "Isolated atrial septal defects (ASDs) in children: Management and outcome" and "Management and outcome of tetralogy of Fallot" and "Tetralogy of Fallot (TOF): Pathophysiology, clinical features, and diagnosis".) Longitudinal studies suggest that atrial tachyarrhythmias afflict between 20 and 50 percent of individuals with CHD over their lifetime [9]. Approximately half of patients who have ASD repair over age 25 years [12] and nearly one-third of patients with tetralogy of Fallot develop atrial tachyarrhythmias [13]. (See "Clinical manifestations and diagnosis of atrial septal defects in adults" and "Atrial septal abnormalities (PFO, ASD, and ASA) and risk of cerebral emboli in adults" and "Stroke associated with patent foramen ovale (PFO): Evaluation".) The development of atrial tachyarrhythmias is associated with higher morbidity, mortality, and hospitalization rates in patients with CHD and a worse functional class. Atrial tachyarrhythmias are independently associated with a higher risk of death in patients with single-ventricle anatomy, pulmonary hypertension, and valvular heart disease [14]. Atrial arrhythmias are seen in more than half of patients with the more complex repairs such as the classical atriopulmonary Fontan operation [15,16], and in response to this, alternate surgical approaches such as the extracardiac Fontan, which excludes the right atrium and the nidus for atrial arrhythmias, have evolved [17,18]. The frequency of congenital heart disease as a cause of atrial arrhythmias in the fetal heart is discussed separately. (See "Fetal arrhythmias".) PATHOPHYSIOLOGY https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 2/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Tachycardias in this group of patients most commonly have a reentrant mechanism and are facilitated by abnormal atrial substrate adjacent to valves, patches, or suture lines. In addition, cellular injury from longstanding hypoxia and atrial stretch conceivably also engenders inhomogeneity in myocardial conduction and refractoriness and hence adds to the arrhythmogenic milieu ( table 1) [19]. (See "Approach to the child with tachycardia".) Bradycardia can be inherent to the congenital anomaly, such as abnormalities of the sinus node or atrioventricular (AV) node in the heterotaxy (isomerism) syndromes, L-transposition of great arteries, or AV septal defects [20,21]. However, bradycardia is most commonly seen secondary to iatrogenic disruption of these structures and can occur in both the early postoperative period and/or many years after the operation, presumably driven by fibrosis [15,22-25] ( table 1). (See "Bradycardia in children".) Bradycardias Symptomatic bradycardia can cause considerable morbidity in patients with congenital heart disease (CHD). Pacemaker implantation is required for bradyarrhythmias in up to 3 to 4 percent of patients after surgical repair of Ebstein anomaly [26]; in approximately 7 percent of Fontan patients [15,27]; in over 80 percent of patients who have undergone atrial switch procedures for d-transposition of the great arteries; and around half of those patients with congenitally corrected transposition [28] of the great arteries (ccTGA) [22]. (See "Clinical manifestations and diagnosis of Ebstein anomaly".) Congenital sinus node dysfunction Superior sinus venosus ASDs (occurring in the septum between the superior vena cava and right-sided pulmonary veins) account for around 5 to 10 percent of all ASDs [29,30]. Due to the location of this defect, congenital sinus node dysfunction is commonly found [31]. This is also the case in the other rare CHD lesions that involve the heterotaxy syndromes or juxtaposed atrial appendages [32]. (See "Clinical manifestations and diagnosis of atrial septal defects in adults", section on 'Sinus venosus defect' and "Fetal arrhythmias".) Acquired sinus node dysfunction Any procedure involving an atriotomy such as cannulation for cardiopulmonary bypass potentially risks injury to the sinus node by virtue of its location. More extensive congenital operations involving atrial repair pose substantial risk to the sinus node. These include the atrial switch (Mustard/Senning), Glenn, Fontan, and Ebstein repairs [15,22,23,33]. Patients may present with an overt loss of sinus rhythm or a poor chronotropic response to exercise [22,23]. (See "Management of complications in patients with Fontan circulation", section on 'Arrhythmias'.) Congenital AV block While familial congenital AV block is reported, the majority of congenital AV block is secondary to maternal auto-antibodies in the settings of diseases like https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 3/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate systemic lupus erythematosus and Sj gren's disease [34,35]. The AV node is a right atrial structure, whereas the His bundle, the electrical continuation of the AV node, is a ventricular structure. Therefore, anatomical defects, which include misalignment of these two contiguous chambers, frequently result in interruption of AV conduction. These anomalies include ccTGA, large primum ASDs, and large AV septal defects (AV canal defects) [21,36]. These malformations can result in either complete heart block or progressive AV conduction disease [37]. (See "Pregnancy in women with congenital heart disease: Specific lesions", section on 'Congenitally corrected transposition of the great arteries' and "Management and outcome of atrioventricular (AV) canal defects", section on 'Arrhythmias'.) Acquired AV node dysfunction Surgical trauma in the region of the AV conduction axis occurs most commonly with operations that involve this region, such as aortic valve, left ventricular outflow tract, or AV valve repair/replacement [24]. Tachycardias Intraatrial reentrant tachycardia Atrial scars in repaired CHD patients provide a fundamental element for the development of intraatrial reentrant tachycardia (IART), which is the most common atrial tachyarrhythmia [33] in this population (see "Intraatrial reentrant tachycardia"). Mechanistically, IART is similar to atrial flutter, with a macro-reentrant circuit requiring a zone of slow conduction that develops in diseased tissue and is bordered by scars/valve or vena cava. Found primarily in patients where the atrial tissue is damaged through chronic stretch or operative scars, these circuits usually develop many years after the original intervention [38,39]. Classical intracardiac Fontan repairs, which utilize atrial tissue and the Mustard/Senning procedures, are most commonly associated with this arrhythmia. They can occur also with simple atriotomy scars ( figure 1). Concomitant sinus node dysfunction and older age at first surgical repair appear to increase the incidence [15]. The atrial rate may vary between 150 and 250 beats per minute, and in the presence of preserved AV nodal function, the ensuing ventricular response may be 1:1, with rapid clinical deterioration. Atrial fibrillation The pulmonary venous origins of paroxysmal atrial fibrillation in CHD do not appear to differ markedly from acquired heart disease [40]. Left heart lesions with subsequent left atrial stretch and fibrosis are most commonly associated with this rhythm abnormality. Associated coronary disease or lesions involving the left ventricular outflow tract and/or mitral valve are the more commonly related lesions [41]. The presence of CHD does not preclude other conditions contributing to atrial arrhythmias such as obstructive sleep apnea and thyroid disease, and these should be sought. https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 4/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Ectopic/focal atrial tachycardia The precise etiology and prevalence of this arrhythmia in CHD is less clear (see "Focal atrial tachycardia"). It is far less common than IART and appears to be more prevalent in children than in adults with CHD [42]. It may originate from atrial tissue within the Fontan circuit, from the atrial appendages, or adjacent to the pulmonary veins. On the surface electrocardiogram, this arrhythmia can be identified by the unusual p-wave axis and often a progressive increase in the rate. Catheter ablation of the focus, however, is associated with much higher rates of success than IART and provides an excellent chance of cure [43]. EVALUATION Cardiac referral and further evaluation The management and treatment of patients with congenital heart disease (CHD) and atrial arrhythmias are often more complex than more typical arrhythmia patients. These patients should be referred to centers that routinely follow this population [44-46]. Importantly, atrial arrhythmias can be a harbinger of underlying hemodynamic deterioration, and a comprehensive congenital clinical and hemodynamic assessment is vital for all congenital cardiac patients. History A thorough surgical history, including operative reports, is necessary. This information is critical not only in the diagnostic work-up of the patient and atrial arrhythmia, but also in identifying whether venous access for catheters or permanent pacing is feasible. Similarly, during pacing or ablation procedures, inadvertent injury to the AV conduction system may occur. In these instances, it is critical to know whether a transvenous route to rapidly pace the ventricle is available. Physical examination The physical examination is important in order to identify evidence for concomitant cardiovascular lesions, which may be integral to the arrhythmia development. For example, the presence of peripheral edema, ascites, and an enlarged liver might identify Fontan obstruction or failure, and revision of this conduit may prove to be the most appropriate ultimate intervention for worsening atrial arrhythmias. Electrocardiogram The 12-lead electrocardiogram (ECG) is instrumental in clarifying the underlying rhythm disturbance in CHD patients [47]. However, the ECG can be misleading in this patient population, reemphasizing the importance of specialty care ( waveform 1). Patients with intraatrial reentrant tachycardia (IART) often have atrial rates that are slower than typical cavotricuspid isthmus dependent flutter, with discrete p-waves and an isoelectric interval. This rhythm is often mistaken for sinus tachycardia, as the p-wave can be buried in the preceding QRS complex or in the setting of 1:1 conduction through a healthy AV node ( waveform 2). Patients who have undergone modified Maze surgeries often have very little evidence of atrial https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 5/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate activity on the ECG, making electrocardiographic diagnosis challenging [48]. (See "Atrial fibrillation: Surgical ablation" and "Atrial fibrillation: Surgical ablation", section on 'Maze procedure'.) An underlying IART may be missed in this instance and running a longer rhythm strip can be helpful to identify grouped beating occurring in the context of variable AV block. The T wave should also be scrutinized for any sharp deflections not usually associated with repolarization, and hence indicative of atrial depolarization. Echocardiogram The transthoracic echocardiogram is invaluable in identifying structural and hemodynamic cardiac lesions that may have precipitated the rhythm disturbance. Conduit or valvular dysfunction may lead to secondary effects on the atrial muscle and thus a CHD specialist should interpret the echocardiograms in these patients. The echo examination may also provide the first clue to an atrial rhythm disturbance or demonstrate reduction in ventricular function from tachycardia. Fetal echocardiography has allowed identification of congenital cardiac anomalies, and this should be considered in fetuses at increased risk. (See "Congenital heart disease: Prenatal screening, diagnosis, and management".) Ambulatory ECG/Holter monitoring/prolonged cardiac monitoring device Twenty-four- hour Holter recordings or prolonged device monitoring (such as wireless patch cardiac monitors) are important tools to identify the underlying rhythm abnormality when the patient's ECG is unrevealing and there is a history of presyncope, syncope, or palpitations [49]. In addition, this can be a useful adjunctive investigation when chronotropic incompetence is suspected, due to underlying sinus, AV node, or medication-related bradycardia. (See "Ambulatory ECG monitoring".) Event monitor The event monitor is used to identify the etiology of short-lived symptoms that cannot be characterized by the ECG, Holter recordings, or prolonged device monitoring. One- to three-month periods of transient cardiac event monitors or looping recorders are frequently employed diagnostically, and insertable cardiac monitors (ICM; also sometimes referred to as implantable cardiac monitor or implantable loop recorder) can be considered for patients with infrequent symptoms. (See "Ambulatory ECG monitoring".) Exercise testing Exercise testing is vital in demonstrating chronotropic incompetence in the setting of symptomatic sinus node dysfunction and also for exposing infranodal AV conduction block in those patients with 2:1 AV block or exertional dyspnea. Catecholaminergic surges that develop during maximal effort can also precipitate tachyarrhythmias by influencing conduction velocity and refractoriness. In addition, faster AV node function during exercise may allow 1:1 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 6/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate conduction in the context of a previously undiagnosed atrial tachycardia with 2:1 AV block. (See "Exercise ECG testing: Performing the test and interpreting the ECG results".) Electrophysiology study It is recommended to proceed with an electrophysiology study in the evaluation of the patient with CHD following an unexplained cardiac arrest or syncopal event, and for those who present with sustained ventricular tachycardia. This is aimed at identifying potential lethal sinus or AV nodal disease and can identify whether a ventricular arrhythmia was likely causative. Electrophysiology study is also recommended in select CHD patients prior to cardiac surgical intervention such as those with Ebstein anomaly with a history of arrhythmias [50]. It should also be considered for this group of patients with palpitations where a standard workup has been unrevealing [50]. (See "Invasive diagnostic cardiac electrophysiology studies".) MANAGEMENT It is important to recognize that in the management of atrial tachyarrhythmias in patients with congenital heart disease (CHD), rhythm versus rate control has not been studied. (See "Management of atrial fibrillation: Rhythm control versus rate control".) The AFFIRM and HOT- CAF studies [51,52] did not include patients with CHD with or without prior repair, and as such we do not have any long-term data comparing the outcomes with these strategies. In addition, the most common atrial arrhythmia encountered in clinical practice is that of intraatrial reentrant tachycardia [41], an arrhythmia that is unlikely to respond to rate-control because of the fixed circuit and slower atrial cycle length. For this reason, antiarrhythmic medications and ablation provide the cornerstone of therapy [50]. Acute termination For any atrial tachyarrhythmia that is associated with hemodynamic instability, synchronized direct current (DC) cardioversion should be utilized without delay. (See "Basic principles and technique of external electrical cardioversion and defibrillation".) DC cardioversion can also be reserved for the initial management of hemodynamically stable yet symptomatic arrhythmias if a more definitive strategy has not yet been chosen, and the patient has fairly infrequent episodes. In this context, transesophageal echocardiography (TEE) to identify intracardiac clot is strongly recommended, especially in Fontan circulations, irrespective of the anticoagulation status [53,54]. The classical Fontan often entails sluggish blood flow, and atrial thrombus formation is common. Embolism of the thrombus into the pulmonary bed through DC cardioversion can be fatal in these patients. Cardioversion in the patient with CHD with appropriate precautions including anticoagulation and pre- or periprocedure TEE is proven to be safe and effective and should not be withheld [54,55]. TEE-guided cardioversions for https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 7/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Fontan and other high-risk congenital patients are commonly done in conjunction with anesthesia staff due to tenuous hemodynamics and the risk of complications related to sedation. Symptomatic bradyarrhythmias may require acute temporary pacing, and preprocedure knowledge of intracardiac and vena caval anatomy is critical. Anticoagulation is recommended for any CHD patient with an intracardiac shunt receiving a temporary pacemaker to avoid systemic thromboembolism from the pacing lead, until a permanent epicardial or alternate percutaneous system can be placed. (See "Temporary cardiac pacing".) Permanent pacemaker implantation In general, the indications for permanent pacing in CHD are similar to those in acquired heart disease. All symptomatic sinus or AV node disease requires pacemaker intervention [56]. (See "Permanent cardiac pacing: Overview of devices and indications" and "Congenital third-degree (complete) atrioventricular block".) Several special considerations apply to patients with CHD who require pacemaker implantation: Planning of lead access Lead access frequently poses difficulties in this group, and a detailed surgical history is necessary, often with adjunctive review of cross-sectional imaging (eg, computerized tomography, magnetic resonance imaging) or venography. In complex CHD patients with prior operative intervention in whom surgical reports are not available and urgent pacemaker placement is needed, imaging of venous anatomy with cross-sectional imaging or venography is crucial. Avoid thromboembolic stroke To avoid paradoxical thromboembolic stroke from transvenous lead thrombus, the clinician should image the heart and vessels (TEE with bubble study or venography) to exclude intracardiac shunting/baffle-leaks. If these are present and not amenable to closure, epicardial pacemaker lead placement may be indicated, depending on the patient-specific comorbid conditions [57-59]. No lead across mechanical tricuspid valve In patients with a mechanical tricuspid (non- systemic AV) valve, a pacemaker lead should not be positioned crossing the valve. Options in this setting include a coronary sinus lead [60] or an epicardial lead. Antiarrhythmic drug therapy Antiarrhythmic drugs remain a cornerstone in the management of atrial arrhythmias in CHD patients. Class I agents (such as propafenone or flecainide) should be avoided in any patient with ventricular scar given the potential for life- threatening ventricular arrhythmias [61-63]. (See "Arrhythmia management for the primary care clinician".) These medications slow cardiac electrical conduction, can also result in slower, more sustained atrial flutters, and hence are not the medications of choice in this group. Dofetilide https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 8/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate [64] and sotalol [65] delay repolarization and therefore are the most suitable for reentrant atrial arrhythmias (such as intraatrial reentrant tachycardia), with dofetilide having the added benefit of avoiding any impact on the sinus or AV nodes in the bradycardic patient [66]. (See "Clinical uses of sotalol" and "Clinical use of dofetilide".) The most effective drug is amiodarone [67], although significant side effects may be problematic leading to noncompliance or discontinuation [68]. (See "Amiodarone: Adverse effects, potential toxicities, and approach to monitoring" and "Amiodarone: Clinical uses".) Long-term use of amiodarone requires close monitoring of eye, thyroid, pulmonary, and hepatic function [64], and this should rarely be considered as lifelong suppressive therapy in the younger adult CHD patient with atrial arrhythmias [50]. Ablation Radiofrequency catheter ablation (RFA) is now utilized early in the course of many adult congenital patients with atrial tachyarrhythmias. Atrial arrhythmia ablation should be considered in symptomatic patients refractory to or unsuitable for long-term antiarrhythmic therapy. Minimally symptomatic atrial tachyarrhythmias can also be targeted with this approach to avoid a tachycardia-mediated decline in ventricular function. RFA can be complex in patients with CHD, and it is recommended these procedures be performed at centers experienced with RFA in this patient population [50]. Although early success rates are excellent even in the most complex defects [69,70], long-term recurrence rates remain suboptimal, especially when multiple circuits coexist and atrial scars are abundant [71]. The clinical tachycardia can most often be eradicated to reduce symptomatic recurrence and improve antiarrhythmic drug therapy or pacing efficacy [72-74], yet other arrhythmias can subsequently develop. Older age at time of ablation and complexity of the atrial repair (Fontan or atrial-switch) both predict worse procedural success [75]. It is also important to recognize that the electrophysiological study often unmasks underlying sinus node dysfunction, and a role for permanent pacing may be identified [75]. For this reason, we recommend discussing this antecedently with patients. Atrial antitachycardia devices Pacemakers with atrial antitachycardia pacing capability have been used to treat reentrant atrial tachycardias in patients with CHD. As a sole therapy, long- term efficacy for this approach is poor, but can be considered in patients with symptomatic bradycardia and/or other clear indications for pacing. In this setting, and often in conjunction with ablation, Maze, or anti-arrhythmic drug therapy, this pacing strategy can be effective in limiting symptomatic exacerbations [76,77]. Maze surgery CHD patients undergoing operative repair of a cardiac defect should be considered for Maze surgery if there is a background of atrial arrhythmias [78]. Cut-and-sew https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 9/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate techniques have higher rates of freedom from atrial arrhythmia when compared with alternative energy sources such as radio-frequency ablation or cryoablation [79,80]. No data currently exist on preemptive Maze surgery in CHD patients at high risk for, but without, prior documented arrhythmias. (See "Atrial fibrillation: Surgical ablation" and "Atrial fibrillation: Surgical ablation", section on 'Maze procedure'.) Anticoagulation therapy Anticoagulation therapy should be considered in CHD patients as soon as an atrial rhythm disturbance is identified. Patients with Fontan circulations have low flow states [81] and are at high risk of thrombus formation within the atria or Fontan circuit. Patients with repaired atrial septal defects also appear to be at high risk for thromboembolic complications in the setting of atrial arrhythmias, accounting for around one-fifth of late deaths in one series [12]. The use of conventional thromboembolic and hemorrhagic risk-assessment scores, such as CHA DS -VASc and CHADS2, 2 2 has not been rigorously evaluated in these patient groups. National and international societal recommendations [50] do, however, recommend using the CHA DS -VASc risk schema for simple 2 2 CHD syndromes (such as repaired atrial septal defect or ventricular septal defect) and then prescription of either warfarin or a direct oral anticoagulant is permissible. (See "Atrial fibrillation in adults: Use of oral anticoagulants" and "Atrial fibrillation in adults: Selection of candidates for anticoagulation".) For all other patients with atrial arrhythmias (those with CHD of moderate or severe complexity), warfarin is generally recommended without the need for thromboembolic risk stratification [50]. Limited data regarding the non-vitamin K oral anticoagulant agents suggest efficacy in CHD patients [82-84]. SPECIFIC CONSIDERATIONS ASD Atrial septal defect (ASD) is one of the most common congenital cardiac anomalies and is associated with a high incidence of atrial arrhythmias, which increase in frequency as affected patients age [9,12]. (See "Management of atrial septal defects in adults".) The later in life the ASD is repaired, the more likely atrial arrhythmias are to develop. Surgical and device closure do not appear to mitigate the development of this problem [12]. In addition, significant thromboembolic complications have been observed in patients who had surgical ASD closure performed at 24 years of age or older, affecting around 22 percent of these patients [12]. For this reason, anticoagulation is recommended for all patients with atrial arrhythmias following surgical ASD closure with a CHA DS -VASc 2 [50]. Atrial arrhythmias should be actively 2 2 identified using routine ambulatory ECG monitoring. Intraatrial reentrant tachycardia circuits https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 10/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate around a patch or suture lines also occur frequently, and ablative therapy should be considered early in their management [85]. Prior Maze Modified Maze operations are a common, safe, and highly effective surgical method of restoring sinus rhythm in patients with CHD and atrial fibrillation/flutter. (See "Atrial fibrillation: Surgical ablation".) These interventions, which are often performed at the time of CHD operations, can be effective in preventing atrial arrhythmia recurrence approximately 70 to 80 percent at 10 years [86]. Maze procedures present potential electrical and mechanical complications subsequent to the extensive transmural lesions that not only potentially interfere with sinus and intraatrial conduction but which can also disrupt atrial mechanical compliance and transport. Sinus node dysfunction, atrial bradyarrhythmias and tachyarrhythmias, and development of an indication for permanent pacemaker implantation are among the sequelae of the Maze procedure. New atrial tachyarrhythmias can develop around Maze lesions, and ablation of these is commonly subsequently necessary. Antiarrhythmic drug therapy is frequently used in this setting, and atrial antitachycardia pacemakers can be of added utility [87]. (See "Atrial fibrillation: Surgical ablation", section on 'Limitations and complications'.) Tetralogy of Fallot Bradyarrhythmias requiring permanent pacing in patients with tetralogy of Fallot are uncommon. However, atrial tachyarrhythmias are a frequent cause of morbidity and may be seen in up to 25 percent of patients with tetralogy of Fallot [13] (see "Management and outcome of tetralogy of Fallot"). The prevalence of atrial arrhythmias markedly increases after 45 years of age in this group and in those with reduced left ventricular function [88]. Fontan procedure The "classic" Fontan procedure that fashions an atriopulmonary conduit from right atrial tissue is more frequently associated with the development of atrial arrhythmias [89] compared with contemporary "extracardiac" Fontan procedures [90]. In a retrospective analysis of adult patients with prior Fontan procedure (mean follow-up of 18.6 years), 42 percent sustained at least one tachyarrhythmia [74,91]. The most common arrhythmia was intraatrial reentrant tachycardia. These are commonly recurrent issues and are associated with important morbidity [70]. Anticoagulation is recommended in all Fontan patients with atrial arrhythmias [81], and empiric anticoagulation is often recommended for all patients with the classical atriopulmonary connection, since these patients are at the highest risk of thromboembolic events and atrial arrhythmias [90]. Conversion to an extracardiac conduit or total cavopulmonary connection may provide hemodynamic relief and reduce the arrhythmia burden, but it comes with substantial inherent operative risk, and candidates for this procedure should be carefully selected [92]. https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 11/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Injury to the sinus node is also common following the Fontan procedure [93], and permanent pacing may be necessary. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Arrhythmias in adults".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, The Basics and Beyond the Basics. th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on patient info and the keyword(s) of interest.) Basics topics (see "Patient education: Heart block in adults (The Basics)" and "Patient education: Heart block in children (The Basics)") SUMMARY AND RECOMMENDATIONS Atrial arrhythmias are common in congenital heart disease (CHD), affecting at least 20 percent of CHD patients over their lifetime. (See 'Prevalence and incidence' above.) Atrial arrhythmias are a major cause of morbidity in patients with CHD and can be precipitated by cardiac residua. They can also cause hemodynamic deterioration. For this reason, it is imperative that a comprehensive clinical and hemodynamic assessment be undertaken as part of the initial arrhythmia work-up. (See 'Prevalence and incidence' above and 'Evaluation' above.) https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 12/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate CHD patients with atrial arrhythmias should be referred to centers that routinely care for CHD patients. Bradycardia can be inherent to the CHD anomaly; however, it is more commonly seen secondary to operative disruption of the conduction system. This can occur in both the early postoperative period or later due to fibrosis. (See 'Bradycardias' above.) Stroke is common in adult CHD patients, and atrial arrhythmias such as atrial fibrillation and intraatrial reentrant tachycardia (IART) should prompt the clinician to consider long- term oral anticoagulation. (See 'Anticoagulation therapy' above.) Indications for permanent pacing in CHD are similar to those in acquired heart disease. 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