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.................................................................................... prevalence of asymptomatic findings has been reported that rarely change management.37

In all patients, evaluation for a reversible cause of the arrhythmia (e.g. hyperthyroidism, inflammatory process) and new or residual haemodynamic abnormalities is important. Arrhythmias causing haemodynamic instability require immediate termination irrespective of duration/anticoagulation following current recommendations.32 Post-conversion, sinus arrest/bradycardia may occur and availability of back-up pacing needs to be considered in patients at risk for sinus node dysfunction (SND) (Table 7). If IART/AF is tolerated and lasting >_48 h, cardiac thrombus needs to be ruled out (TOE) and/or appropriate anticoagulation (>3 weeks) and pharmacological rate control needs to be initiated before cardioversion using a beta blocker or calcium channel blocker (in patients with normal systemic ventricular function and absent preexcitation).32,37,38 Maintenance of sinus rhythm is the aim in all CHD patients.32,37 Catheter ablation is recommended as first-line therapy and preferred over long-term pharmacological treatment, in case of amenable, circumscribed substrates, as antiarrhythmic drugs are often associated with negative inotropic and/or dromotropic effects.32 Antiarrhythmic drugs such as class IC drugs may slow the rate of IART without blocking AV conduction allowing 1:1 conduction with worsening haemodynamics.32 Amiodarone may be considered for AT/AF recurrence prevention in patients with CHD and systemic ventricular dysfunction, hypertrophy of systemic ventricle, or CAD, in whom catheter ablation fails or is otherwise no option. Side effects of amiodarone are frequent and it should be used with caution in cyanotic CHD, low body weight, hepatic, thyroid, or pulmonary disease, or prolonged QT interval. Longterm amiodarone therapy is not advised in young CHD patients.32 For optimal chronic arrhythmia management, referral to a centre with a multidisciplinary team and expertise in CHD-related arrhythmias is mandatory.32,37 For more specifications on anticoagulation see section 3.4.7.

3.4.2.3 Sinus node dysfunction, atrioventricular block, and infra-hisian conduction delay Periodic Holter for patients at risk for SND and AV block should be considered in asymptomatic patients. Chronic SND/bradycardia with ineffective atrial haemodynamics may affect atrial remodelling and facilitate IART. Patients with post-operative AV block are considered at increased risk for SCD. Accordingly, broader indications for pacemaker implantation compared with patients with structurally normal hearts have been suggested.20,32 In ACHD patients with a biventricular circulation and a systemic LV, indications for CRT follow standard criteria. Of note, conventional ventricular pacing rather than bundle branch block is the major cause of systemic ventricular dysfunction. Accordingly, CRT is recommended in ACHD with a systemic EF <_35% and intrinsic narrow QRS, and an anticipated requirement for significant pacing and new device placement. Alternatively, his bundle pacing could be considered. Efficacy of CRT in ACHD may vary across defects and may depend on the individual anatomy and causes of dyssynchrony (e.g. systemic RV/single ventricle, AV valve regurgitation, scarring). In general, QRS duration alone may not be a sufficient predictor and follow-up data are limited. In addition, thoracotomy or hybrid lead implantation is often required and data on longevity of CRT are lacking.32 3.4.2.4 Sudden cardiac death and risk stratification SCD related to ventricular arrhythmia is of concern (726% of all deaths in adults).29,39,40 Although the incidence in the CHD population at large is relatively low (<0.1% per year), some defects place patients at higher risk, with occasional disease-specific substrates and risk factors (Table 7). Identifying patients at risk for SCD remains a challenge.

ICD implantation for secondary prevention of SCD and for primary prevention in patients with biventricular physiology and a systemic LV follows standard criteria.37,41 Antiarrhythmic drugs may be used as an adjunct to an ICD in order to reduce the ventricular arrhythmia burden.32 The benefit of ICD therapy in primary prevention for single or systemic RVs is less well established. Accordingly, with the exception of tetralogy of Fallot (TOF), specific guidelines regarding ICD implantation for primary prevention in CHD remain elusive.32,37 Transvenous ICD systems have been used, but in patients with limited venous access to the ventricle or intracardiac shunt, the subcutaneous ICD may be an alternative. However, not all patients are eligible due to the risk of inappropriate sensing and lack of antitachycardia and antibradycardia pacing. The usefulness of programmed electrical stimulation (PES) in asymptomatic patients with CHD is unclear. It seems reasonable in patients with ventricular incisions and/or a substrate for ventricular reentry typically, but not exclusively, encountered in repaired TOF (rTOF). It is important to recognize other causes of SCD due to bradycardia/total AV block and bradycardia-induced ventricular arrhythmia with or without long QT, and IART/AF with rapid conduction.

Recommendations for treatment of arrhythmias in adult congenital heart disease

Recommendations Classa Levelb

In patients with moderate and severe CHD complexity (Table 4) and documented arrhythmias, referral to a centre with a multidisciplinary team and expertise in ACHD patients and ACHDrelated arrhythmia is indicated. I C In CHD patients with documented arrhythmias or at high risk for post-procedural arrhythmias (e.g. ASD closure at older age) considered for percutaneous or surgical (re)interventions, referral to a centre with a multidisciplinary team with expertise in these interventions and in invasive treatment of arrhythmias is indicated. I C In mild CHD, catheter ablation is recommended over long-term medical therapy for symptomatic, sustained recurrent SVT (AVNRT, AVRT, AT, and IART), or if SVT is potentially related to SCD (Table 7). I C In moderate and severe CHD, catheter ablation should be considered for symptomatic, sustained recurrent SVT (AVNRT, AVRT, AT, and IART), or if SVT is potentially related to SCD (Table 7), provided that the procedure is performed in experienced centres. IIa C

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