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. All symptomatic sinus or atrioventricular (AV) node disease requires pacemaker intervention with preemptive delineation of venous anatomy and intracardiac shunting being fundamental. (See 'Permanent pacemaker implantation' above.) Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Marelli AJ, Mackie AS, Ionescu-Ittu R, et al. Congenital heart disease in the general population: changing prevalence and age distribution. Circulation 2007; 115:163. 2. Brickner ME, Hillis LD, Lange RA. Congenital heart disease in adults. Second of two parts. N Engl J Med 2000; 342:334. 3. Brickner ME, Hillis LD, Lange RA. Congenital heart disease in adults. First of two parts. N Engl J Med 2000; 342:256. 4. Gilboa SM, Devine OJ, Kucik JE, et al. Congenital Heart Defects in the United States: Estimating the Magnitude of the Affected Population in 2010. Circulation 2016; 134:101. 5. Hoffman JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol 2002; 39:1890. 6. 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Topic 13599 Version 24.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 20/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate GRAPHICS Etiology of arrhythmias in congenital heart disease Bradycardia Examples Congenital Congenital sinus node Situs inversus dysfunction Congenital AV block AV canal defects; cc-TGA Acquired Acquired sinus node dysfunction s/p repair of Mustand/Senning, Fontan, Glenn or sinus venosus ASD Acquired AV node dysfunction s/p VSD/LVOT/aortic valve operation Tachycardia Examples Congenital Twin AV nodes Heterotaxy syndrome Acquired Atrial tachycardia/flutter Atrial baffles; post-MAZE Atrial fibrillation ASD's, mitral valve disease Ectopic atrial tachycardia Fontan AV: atrioventricular; cc-TGA: congenitally corrected transposition of the great arteries; ASD: atrial septal defect; VSD: ventricular septal defect; LVOT: left ventricular outflow tract. Graphic 64292 Version 3.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 21/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Common congenital anomalies per 10,000 live births Lesion Average Ventricular septal defect 36 Patent ductus arteriosus 8 Atrial septal defect 9 Atrioventricular septal defect 4 Pulmonary stenosis 7 Aortic stenosis 4 Coarctation of the aorta 4 Tetralogy of Fallot 4 d-Transposition of the great arteries 3 Bicuspid aortic valve 136 Data from: Ho man JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol 2002; 32:1890. Graphic 78627 Version 2.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 22/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Atriotomy scars The majority of atrial arrhythmias in congenital heart disease are driven by a scar-related reentrant mechanism. As evidenced in this diagram, the scars and postsurgical fibrotic tissue provide boundaries as well as a substrate for slow conduction, which allows for propagation of electrical reentry and intraatrial reentrant tachycardia (IART). The arrows delineate potential routes for electrical reentry during the propagation of IART. SVC: superior vena cava; CS: coronary sinus; IVC: inferior vena cava; TV: tricuspid valve. By permission of the Mayo Foundation for Medical Education and Research. All rights reserved. Graphic 75779 Version 10.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 23/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Atrial versus sinus rhythm on electocardiogram An ECG demonstrating an intraatrial reentrant tachycardia/atrial flutter in a patient with congenital heart dis Viewing lead V1, only a single p-wave is visible (arrows), and it is slightly positive with a negative terminal component, consistent with sinus rhythm/sinus tachycardia and potentially misleading. Lead II, however, rev notching of the T-wave (a second p-wave, dashed arrows), and the third p-wave is entirely hidden within the Q complex (not shown) in a 3:1 atrioventricular ratio. ECG: electrocardiogram. Graphic 114371 Version 2.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 24/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Intraatrial reentrant tachycardia An electrocardiogram from a patient with a Fontan repair, demonstrating an intra-atrial reentrant tachycardia. The periods of higher grade AV block allow for easy identification of the P waves. Without these pauses, the atrial rhythm can be difficult to identify, as the P waves are frequently buried within the preceding QRS complex. This is most evident on the paced beats. Graphic 52478 Version 3.0 https://www.uptodate.com/contents/atrial-arrhythmias-including-av-block-in-congenital-heart-disease/print 25/26 7/6/23, 1:47 PM Atrial arrhythmias (including AV block) in congenital heart disease - UpToDate Contributor Disclosures Samuel Asirvatham, MD Grant/Research/Clinical Trial Support: Medtronic [Defibrillators]; St Jude's [Sudden Cardiac Death]. Consultant/Advisory Boards: BioTronik [Defibrillators]; Boston Scientific [Sudden Cardiac Death]. All of the relevant financial relationships listed have been mitigated. Heidi M Connolly, MD, FACC, FASE No relevant financial relationship(s) with ineligible companies to disclose. Christopher J McLeod, MB, ChB, PhD Consultant/Advisory Boards: BioSig Technologies [Signal processing module for cardiac mapping]. All of the relevant financial relationships listed have been mitigated. Hugh Calkins, MD Grant/Research/Clinical Trial Support: Adagio Medical [Atrial fibrillation]; Boston Scientific [ARVC]; Farapulse [Atrial fibrillation]; Medtronic [Atrial fibrillation]. Consultant/Advisory Boards: Abbott [Atrial fibrillation]; Atricure [Atrial fibrillation]; Biosense Webster [Catheter ablation]; Boston Scientific [ARVC and atrial fibrillation]; Medtronic [Atrial fibrillation]; Sanofi [Atrial fibrillation]. Other Financial Interest: Atricure [Lecture honoraria]; Biosense Webster [Lecture honoraria]; Boston Scientific [Lecture honoraria]; Medtronic [Lecture honoraria]. All of the relevant financial relationships listed have been mitigated. Charles I Berul, MD Patent Holder: PeriCor LLC [Pacemakers/defibrillators]. Grant/Research/Clinical Trial Support: Medtronic Inc [Pacemakers/defibrillators]. All of the relevant financial relationships listed have been mitigated. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. 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