Arrhythmias in Congenital Heart Disease: A Mini Review

Congenital heart disease (CHD) represents the most common congenital malformation in live-born infants, with an estimated global birth prevalence of approximately 9 per 1,000 live births [1]. Advances in surgical and medical management have significantly improved the survival of children with CHD, resulting in a growing population of adolescents and adults living with repaired or palliated cardiac defects [2]. This demographic shift has given rise to a new spectrum of long-term complications, among which cardiac arrhythmias represent a leading cause of morbidity and mortality. Arrhythmias in CHD patients may arise from a complex interplay of structural, hemodynamic, surgical, and electrophysiological factors. The mechanisms are often multifactorial, including scarring from prior surgeries, chamber enlargement, myocardial fibrosis, and inherent conduction system abnormalities [3,4]. Furthermore, the type and timing of surgical repair, particularly procedures involving atriotomy or ventriculotomy, contribute substantially to arrhythmogenic risk [5]. The spectrum of arrhythmias varies depending on the underlying congenital lesion. Supraventricular arrhythmias, particularly intra-atrial reentrant tachycardia (IART) and atrial fibrillation, are frequently encountered in patients with atrial septal defects (ASD), atrioventricular septal defects (AVSD), and after Fontan palliation [6-8]. Ventricular arrhythmias, including monomorphic ventricular tachycardia (VT), are more prevalent in conditions such as tetralogy of Fallot (TOF) and complex cyanotic CHD with prior ventriculotomy or patch repair [9].

Importantly, arrhythmias in this population are not merely symptomatic disturbances but carry significant prognostic implications. They are associated with increased risk of heart failure, thromboembolic events, and sudden cardiac death, especially in adults with repaired CHD [10-12]. As such, timely identification, risk stratification, and targeted management of arrhythmias are vital components of long-term care in this population. Despite the growing burden of arrhythmias in CHD, challenges persist in diagnosis and management due to the heterogeneity of cardiac anatomy, variable surgical histories, and limitations in applying standard electrophysiological approaches [13]. Tailored strategies, often requiring multidisciplinary input and specialized expertise in adult congenital heart disease (ACHD), are essential for optimal outcomes.

The prevalence and types of arrhythmias in CHD vary according to the underlying defect, type of surgical repair, and patient age. In general, the incidence of arrhythmias increases with time following surgical correction [5]. Atrial arrhythmias, such as intra-atrial reentrant tachycardia (IART) and atrial flutter, are more prevalent in patients with atrial septal defects (ASD), Fontan circulation, and atrioventricular septal defects [6]. Ventricular arrhythmias are more commonly seen in patients with tetralogy of Fallot (TOF), transposition of the great arteries (TGA), and systemic right ventricles [7]. The risk of sudden cardiac death (SCD) is increased in these populations, especially when residual lesions or myocardial scarring is present [8].

Arrhythmogenesis in CHD is multifactorial. One key mechanism is surgical scarring, which can create reentrant circuits, particularly in patients who have undergone atriotomy or ventriculotomy incisions [9]. Chamber dilatation from residual shunts or valvular dysfunction can lead to structural remodeling and fibrosis, further predisposing to arrhythmias [10]. Chronic hypoxia and pressure overload, common in cyanotic lesions or single-ventricle physiology, contribute to myocardial fibrosis and electrical heterogeneity [11]. Additionally, patients with Fontan circulation may experience autonomic dysfunction, which can facilitate both bradyarrhythmias and tachyarrhythmias [12].

The types of arrhythmias observed in CHD are diverse and often lesion-specific. Atrial arrhythmias such as atrial flutter, atrial fibrillation (AF), and IART are the most common and often occur decades after surgical repair [13]. IART is especially prevalent in patients with Fontan physiology or those who have undergone the Mustard or Senning procedures [14]. Sinus node dysfunction is frequently observed following atrial surgeries, particularly in patients with ASDs and Fontan palliation [15]. High-grade atrioventricular (AV) block may occur in patients who have undergone surgical repair involving the septal area [16]. Ventricular tachycardia (VT) and ventricular fibrillation (VF), although less frequent, are associated with significant mortality and are typically seen in TOF, TGA, and systemic right ventricles [17] (Table 1).

Table 1: Common Arrhythmias by Congenital Heart Defect

Arrhythmia diagnosis in CHD requires a multimodal approach. Standard 12-lead ECG and ambulatory Holter monitoring are essential first-line tools for detecting both symptomatic and asymptomatic episodes [18]. For patients with infrequent symptoms, extended monitoring using event recorders or implantable loop recorders improves diagnostic yield [19]. Invasive electrophysiology studies (EPS) are useful for mapping complex arrhythmias and determining ablation strategy [20]. Cardiac imaging, particularly MRI, plays a vital role in assessing ventricular function, chamber sizes, surgical scarring, and myocardial fibrosis [21].

Medical Therapy

Pharmacologic therapy remains an important component of arrhythmia management. Beta-blockers are frequently used for both rate and rhythm control. Class III antiarrhythmics, such as amiodarone and sotalol, are often effective but require careful monitoring due to potential side effects and proarrhythmic risk [22] (Table 2).

Table 2: Risk Factors for Arrhythmias in CHD

Catheter Ablation

Catheter ablation has become a mainstay for treating IART and other reentrant arrhythmias. While success rates are high in some lesions, anatomical complexity and prior surgeries may lower efficacy, particularly in Fontan patients or those with systemic venous baffles [23]. Advances in three-dimensional electroanatomical mapping have improved procedural outcomes.

Pacemaker and ICD Therapy

Sinus node dysfunction and AV block may necessitate permanent pacemaker implantation [24]. Patients with CHD and a history of sustained VT or aborted SCD are candidates for implantable cardioverter-defibrillators (ICDs) [25]. Guidelines also recommend ICDs for primary prevention in selected high-risk groups, such as TOF with significant right ventricular enlargement or dysfunction [26] (Table 3).

Table 3: Diagnostic Tools for Arrhythmia Evaluation in CHD

Surgical and Hybrid Approaches

In patients undergoing reoperation for other indications, surgical ablation (e.g., maze procedure) may be added to reduce atrial arrhythmia burden [27]. Hybrid strategies combining surgical access with catheter mapping are increasingly used for complex arrhythmias that are inaccessible via standard endovascular routes [28].

Long-Term Considerations

Lifelong surveillance is essential for early detection and treatment of arrhythmias in CHD patients. Routine follow-up with ECG and ambulatory monitoring should be part of standard care, particularly in those with repaired complex lesions or previous arrhythmias [29]. Transition from pediatric to adult care must include arrhythmia education, screening, and integration into multidisciplinary ACHD programs [30]. The presence of arrhythmias is a major determinant of quality of life and can increase the risk of heart failure and thromboembolism, especially if unrecognized or undertreated [31] (Table 4).

Table 4: Summary of Management Strategies

Arrhythmias in congenital heart disease are a significant source of morbidity and mortality. Their management requires a deep understanding of congenital anatomy, prior surgical interventions, and arrhythmic mechanisms. Advances in diagnostics, ablation techniques, and device therapy have improved care, but individualized, lifelong management remains essential. Collaborative, multidisciplinary care and early intervention are key to optimizing long-term outcomes.