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.......................................... arrhythmias related to structural remodelling, which may occur at a younger age than in the general population, e.g. AF.

Other arrhythmias are related to the type and timing of the ACHD repair. Right atrial (RA) incisions, together with cardiac remodelling secondary to haemodynamic overload, contribute to the high prevalence of atrial tachycardias (AT) in various CHDs. Most frequently encountered is late intraatrial reentrant tachycardia (IART), in particular cavotricuspid isthmus-dependent atrial flutter. Atrial rates between 150 and 250 beats per minute may lead to rapid AV conduction, haemodynamic compromise, and sudden cardiac death (SCD). Monomorphic ventricular tachycardia (VT) also depends on the malformation (Table 7) and type of repair,34,35 with the critical part of the macro-reentry circuit typically located within anatomically well-defined isthmuses bordered by surgical scars and patch material. In contrast, in patients with progressive failure of the systemic or subpulmonary ventricle, more complex EP changes may occur. These changes involve ion channel remodelling, alterations in calcium handling, and remodelling of the extracellular matrix leading to different arrythmias including less well-organized fast polymorphic VT and ventricular fibrillation (VF).36

3.4.2.2 Assessment in patients with suspected/documented arrhythmias and arrhythmia management In symptomatic patients without arrhythmia documentation at presentation, evaluation depends on the frequency [Holter registration, device interrogation (if present), event recorder] and circumstances (exercise testing) of symptoms. The usefulness of periodic evaluation beyond 12-lead ECGs (e.g. periodic Holter) in asymptomatic patients is less clear. A high

Table 7 Risk estimates for arrhythmic events and bradycardias in ACHD

AF = atrial fibrillation; ASD = atrial septal defect; AV = atrioventricular; AVRT = atrioventricular reentrant tachycardia; AVSD = atrioventricular septal defect; ccTGA = congenitally corrected transposition of the great arteries; CHD = congenital heart disease; EAT = ectopic atrial tachycardia; IART = intraatrial reentrant tachycardia; SCD = sudden cardiac death; SND = sinus node dysfunction; TGA = transposition of the great arteries; TOF = tetralogy of Fallot; VSD = ventricular septal defect; VT = ventricular tachycardia. aConsidering the high prevalence of VSD, the overall risk in unselected patients with VSD is considered to be minimal. bSCD may be due to supraventricular arrhythmias with rapid AV conduction. cVT higher estimated risk in complex dextro-TGA. dNon-arrhythmic. Downloaded from academic.oup.com/eurheartj/article/42/6/563/5898606 by guest on 07 October 2026