Radiofrequency Catheter Ablation for Arrhythmia-induced Cardiomyopathy in Infants: A Case Series and Literature Review

Arrhythmia-induced cardiomyopathy (AiCM) is a subtype of acute heart failure, characterised by left ventricular (LV) systolic dysfunction (LVSD) secondary to rapid and/or irregular ventricular rates caused by sustained supraventricular or ventricular arrhythmias.^1,2 This condition is characterised by a significant improvement in systolic function following the elimination or effective management of the causative arrhythmia.³ In its typical form, AiCM presents with arrhythmia as the sole underlying pathology, and LVSD is fully reversible. However, in the presence of pre-existing structural heart disease, AiCM may exacerbate LVSD, rendering it only partially reversible.⁴ Accessory atrioventricular pathway-mediated supraventricular tachycardia (SVT) is the most common symptomatic tachycardia in young patients with structurally normal hearts.

In symptomatic children weighing >15 kg, radiofrequency catheter ablation (RFCA) of accessory pathways is a well-established intervention.⁵ However, its application in infants aged ≤1 year (typically weighing <10 kg) remains limited due to safety concerns, including risks of vascular injury, atrioventricular block and other complications. Here, we report four cases of infantile AiCM secondary to manifest right-sided free wall accessory pathways, successfully treated with RFCA before the age of 1 year, addressing critical gaps in the risk–benefit assessment for this vulnerable population.

Case Presentation

Case 1

A 12-month-old girl (weight 7.5 kg) was admitted with a 5-day history of cough and 2 days of groaning with respiratory distress. On admission, she presented with pallor, laboured breathing, inspiratory three-concave sign, scattered dry rales in both lungs, regular heart rhythm with muffled heart sounds, no significant murmur and hepatomegaly (liver palpable 3 cm below costal margin). She also showed poor feeding and failure to thrive. Echocardiography revealed left ventricular enlargement, severely reduced LV systolic function (LV ejection fraction; LVEF 14%, LV internal diameter at end-diastole 49.4 mm), mild-to-moderate mitral regurgitation, mild tricuspid and aortic regurgitation, and minimal pericardial effusion. Brain natriuretic peptide (BNP) was 318 pg/ml.

The initial ECG showed pre-excitation syndrome (type B) with a QRS duration of 128 ms. Moreover, continuous ECG monitoring during hospitalisation documented paroxysmal SVT (PSVT) episodes, with heart rates reaching 268 BPM. Based on the coexistence of newly diagnosed severe cardiomyopathy and documented incessant tachycardia, the patient was diagnosed with AiCM secondary to accessory pathway-mediated tachycardia. Treatment with milrinone, captopril, spironolactone and furosemide was initiated for inotropic support, diuresis and vasodilation. Amiodarone was introduced later, which ultimately failed to control the arrhythmia, leading to the decision for ablation.

The ablation procedures were performed under general anaesthesia. Via femoral venous access, a 6 Fr sheath was placed for a diagnostic electrode, and an 8 Fr sheath for a 4 mm tip ThermoCool ablation catheter (Biosense Webster). Given the limited vascular capacity in infants, only these two catheters were used. The ablation catheter was sequentially repositioned to record atrial and His bundle electrograms as needed. Strategies to avoid complications included: meticulous mapping to maintain a safe distance from the accessory atrioventricular node; stable catheter positioning facilitated by the small cardiac chambers to prevent slippage and collateral damage; use of electroanatomical mapping to visualise catheter-tissue contact; and postprocedural echocardiography to rule out valve injury or pericardial effusion. All ablations were guided by the CARTO system (Biosense Webster) and delivered in temperature-controlled mode (target 40°C, power limit 30 W). RFCA was performed, targeting the tricuspid annulus at the 7–8 o’clock position, with successful ablation. Three ablation lesions were delivered, with each lesion lasting 120 seconds. The total procedure time lasted 110 minutes.

One week after RFCA, echocardiography showed persistent LV enlargement, reduced systolic function (LV internal diameter at end-diastole 43.4 mm, ejection fraction; EF 36%, fractional shortening 17%) and mild mitral regurgitation; BNP decreased to 79 pg/ml. Six months post-RFCA, EF normalised (LV internal diameter at end-diastole 27.9 mm, EF 64%), and 1-year follow-up echocardiography confirmed normal heart size (Figure 1 ).

Case 2

A 4-month-old boy (weight 8 kg) was admitted with a 1-week history of vomiting and a 12-hour history of tachycardia. The infant was admitted following a 12-hour documented episode of sustained SVT, which led to the diagnosis of acute heart failure. However, the history revealed preceding non-specific symptoms, including vomiting and lethargy, for 1 week, suggesting that the total arrhythmic burden likely extended over this longer period.

Physical examination revealed a grade II systolic blowing murmur at the second left intercostal space. ECG showed intermittent type B pre-excitation (QRS duration was 120 ms) with narrow and wide QRS tachycardia, suggestive of orthodromic and antidromic atrioventricular re-entrant tachycardia. The recorded SVT had a rate of 190–240 BPM with a narrow QRS complex. Echocardiography indicated irregular heart rhythm, reduced LV systolic function (EF 40%), right atrial and ventricular enlargement, an atrial septal defect, and moderate tricuspid regurgitation. BNP was 7,041 pg/ml. Despite treatment with adenosine triphosphate, propafenone and amiodarone, recurrent arrhythmias persisted with unstable blood pressure, necessitating emergency extracorporeal membrane oxygenation (ECMO).

After 4 days of ECMO and ventilatory support with epinephrine, the infant was weaned off ECMO. RFCA was performed, targeting the tricuspid annulus at the 10 o’clock position, with successful ablation and resolution of pre-excitation (Figure 2). Three ablation lesions were delivered, with each lesion lasting 120 seconds. The total procedure time lasted 75 minutes. One week post-RFCA, echocardiography showed normalised heart size and EF; BNP decreased to 888.2 pg/ml within 5 days postprocedure.

Case 3

An 11-month-old boy (weight 10 kg) was admitted with a 2-week history of poor feeding, worsening over 3 days with vomiting. He had recurrent PSVT to cardioversion. The recorded PSVT had a rate of 289 BPM with a narrow QRS complex. ECG showed sinus tachycardia, left axis deviation and ventricular pre-excitation (QRS duration was 107 ms). Echocardiography revealed significant LV enlargement (Z-score 3.0) and evidence of systolic dysfunction (EF 58%), accompanied by uncoordinated septal motion, mild mitral and tricuspid regurgitation, and a small coronary artery-to-pulmonary artery fistula. The finding of an EF at the lower normative limit, in the context of significant ventricular dilatation, was consistent with arrhythmia-induced cardiomyopathy. The clinical severity was underscored by a markedly elevated BNP level of 13,787 pg/ml. Treatment with adenosine triphosphate, propafenone, and metoprolol failed to achieve cardioversion.

The patient was transferred to the paediatric intensive care unit in a critical condition. Synchronised cardioversion (5 J) restored sinus rhythm, but PSVT recurred. Under general anaesthesia, RFCA with an electrophysiological study was performed, targeting the tricuspid annulus at the 11 o’clock position. Postablation, the body surface pre-excitation wave changed (AVF lead shifted from positive to negative), indicating a second accessory pathway. A second ablation at the 9 o’clock position eliminated pre-excitation (Figure 3). Three ablation lesions were for one target, with each lesion lasting 120 seconds. The total procedure time lasted 55 minutes. Four days post-RFCA, BNP decreased to 20.8 pg/ml, and follow-up echocardiography confirmed normal EF and left ventricular size.

Case 4

A 6-month-old boy (weight 8 kg) presented with frequent PSVT episodes (>10 recurrences), poorly controlled with oral medications. Despite treatment with propafenone and metoprolol, PSVT persisted. The PSVT rate was 245 BPM. ECG showed sinus rhythm with ventricular preexcitation (QRS duration was 107 ms). Echocardiography revealed uncoordinated mid-to-lower septal motion and mildly reduced LV systolic function (EF 50%). After detailed discussion of the risks and benefits, RFCA was performed, targeting the tricuspid annulus at the 12 o’clock position, with successful ablation (Figure 4). Prior to ablation, the His bundle potential was mapped and annotated on the electroanatomic map (Figure 4) to delineate a safety zone. Three ablation lesions were delivered, with each lesion lasting 120 seconds. The total procedure time lasted 69 minutes. Three days post-RFCA, echocardiography confirmed normalised EF.

No procedural complications occurred. Specifically, no significant haematomas were observed, and clinical vascular examination revealed no evidence of limb ischaemia. Postprocedural transthoracic echocardiography confirmed the absence of new tricuspid regurgitation in all patients.

Discussion

AiCM is a reversible form of heart failure caused by sustained tachyarrhythmias, leading to LVSD. AiCM can occur at any age, including in foetuses, infants, children and adults.⁶ Preclinical studies have elucidated its pathophysiology, demonstrating that persistent tachycardia induces heart failure symptoms, LV dilatation, increased wall stress, and elevated end-diastolic pressure and volume.⁴ Elevated plasma levels of atrial natriuretic peptide and BNP accompany early LV dilatation, progressing from a compensatory phase (>7 days) to LV dysfunction (1–3 weeks) and eventual heart failure (>3 weeks), characterised by progressive LV dilatation, increased neurohormonal activation and systemic haemodynamic changes, including reduced systemic blood pressure, and elevated central venous and pulmonary pressures.^7,8 At the cellular level, AiCM involves myofibrillar disarray, cell elongation, sarcomere loss and impaired excitation-contraction coupling due to subclinical ischaemia, oxidative stress, calcium handling abnormalities and adenosine triphosphate depletion. These changes result in LV dilatation and severe systolic dysfunction, with impaired calcium transients and reduced L-type calcium currents correlating with decreased LVEF.

Following cessation of tachycardia, right atrial and arterial pressures normalise, with significant improvements in LVEF and cardiac output within 48 hours, and complete recovery within 1–2 weeks. However, residual myocardial fibrosis and increased LV mass may persist, indicating incomplete ultrastructural recovery.⁹ Critically, such histological changes are potentially irreversible, and have been associated with an increased risk of mortality and recurrent heart failure, even after the normalisation of LVEF.^10,11 This underscores the paramount importance of early suspicion and intervention to prevent the progression to this irreversible myocardial damage.

In paediatric AiCM, the predominant arrhythmias differ from adults, where AF (72.9%), atrial flutter (17.6%) and premature ventricular contractions (2.1%) are most common.¹² In children, atrial tachycardia (59%), incessant junctional re-entrant tachycardia (23%) and ventricular tachycardia (7%) are the primary causes.¹³ It is noteworthy that patients with right-sided accessory pathways represent a distinct subgroup within this population, as the associated ventricular pre-excitation can induce mechanical dyssynchrony, which independently contributes to the development of cardiomyopathy.¹⁴ Paediatric patients, particularly younger paediatric patients, show a higher likelihood of functional recovery, with a median time to LVEF normalisation of approximately 1.5–2 months, and LV end-diastolic dimension recovery within 2–3 months.^15–17

While studies report normalisation of cardiac function and dimensions in paediatric AiCM patients after arrhythmia control, the potential for incomplete myocardial remodelling should inform clinical decisions, favouring early and definitive therapy to mitigate long-term risks.¹⁸ Various factors, such as age, tachycardia rate, baseline LVEF and LV end-diastolic dimension, are predictive of recovery.¹³

Our cases, involving infants aged 4–12 months with right-sided accessory pathway-mediated AiCM, demonstrated complete LVEF and LV end-diastolic dimension normalisation within 3 days to 6 months post-RFCA. This rapid recovery is consistent with the reversal of the dual pathogenic insults: the elimination of the tachyarrhythmia and the restoration of synchronous ventricular contraction following successful ablation.¹⁹ Notably, case 1 showed severe LVSD (LVEF 14%) with gradual recovery over 6 months, underscoring the potential for prolonged recovery in severe cases.

Establishing a causal relationship between arrhythmia and LVSD can be challenging, as LVSD may itself precipitate arrhythmias. Comprehensive diagnostic evaluation is essential to rule out underlying causes of LVSD. The reversibility of LVSD within weeks to months following arrhythmia control confirms the diagnosis of AiCM. Studies have also shown that the initial degree of LV dilatation in patients with arrhythmia-induced cardiomyopathy is less pronounced compared with those with dilated cardiomyopathy or secondary tachycardia.²⁰

In infants, delayed recognition of symptoms often leads to heart failure at presentation. Therefore, when infants present with persistent tachycardia, AiCM should be considered as a potential new diagnosis for LV dysfunction or heart failure.¹⁷ AiCM in infants often presents with non-specific symptoms, such as respiratory distress, vomiting and poor feeding, in our cases. This lack of specificity underscores the critical importance of early recognition and intervention, as the duration of tachycardia determines the degree of recovery. Our cases highlight the efficacy of RFCA in infants with AiCM, with no complications, such as atrioventricular block or vascular injury. This outcome aligns with the high long-term success rate of 93.3% reported by Svintsova et al. for infant ablation, and is further supported by Ozaki et al., who demonstrated its safety and efficacy in low-weight infants.^21,22

Furthermore, available long-term follow-up data in children are reassuring. A study monitoring patients for up to 15 years after ablation in early childhood found no evidence of ablation-induced LV dysfunction, suggesting that the procedure itself does not appear to be a common cause of late-onset cardiomyopathy.²³

All four cases in this series involved right-sided accessory pathways, which is relevant to the selection of RFCA as a treatment modality. While right-sided accessory pathways can be approached via venous access, associated with a lower risk of vascular injury, making RFCA a viable option when pharmacological therapy fails, the management of left-sided or concealed pathways in infants remains more complex with the risks of any left-sided procedure (e.g. thromboembolism, cardiac perforation). Although a transseptal approach or traversal of a patent foramen ovale can circumvent the need for arterial access, our institutional strategy during this period prioritised risk mitigation in infants with pre-existing ventricular dysfunction. Thus, for those with recurrent arrhythmias related to left-sided or concealed pathways, we generally opted for intensified multi-drug therapy and deliberately deferred catheter ablation until after infancy to optimise procedural safety.

Our experience highlights several technical considerations for successful RFCA in infants with AiCM. The strategy of using a minimal number of catheters reduces vascular burden and the risk of complications. Furthermore, the small cardiac chambers in this age group, while challenging, can be leveraged to the operator’s advantage by providing inherent catheter stability.

AiCM encompasses ventricular dysfunction caused by various arrhythmias, such as AF, frequent premature ventricular complexes and sustained tachycardias.⁴ Tachycardia-induced cardiomyopathy is a prominent subtype within this spectrum.⁹ Tachycardia-induced cardiomyopathy can be classified into two distinct types: tachycardia-induced cardiomyopathy, in which the arrhythmia is the sole cause of ventricular dysfunction in an otherwise normal heart, and arrhythmia-superimposed cardiomyopathy, in which the arrhythmia exacerbates ventricular dysfunction and/or worsens heart failure in patients with known or underlying structural heart disease.²⁴ In AiCM without concurrent underlying heart disease, cardiac function can normalise following arrhythmia control. If recovery does not occur, potential factors, such as subclinical arrhythmia recurrence or underlying cardiomyopathy, should be investigated.¹³

Despite successful arrhythmia control and LVEF normalisation, residual myocardial damage may persist. Studies have reported persistent diffuse fibrosis and elevated LV end-diastolic volumes in AiCM patients years after successful ablation, suggesting incomplete ultrastructural recovery.⁴ In patients with focal atrial tachycardia-induced cardiomyopathy who achieved successful ablation and normalised LVEF, MRI scans conducted 5 years postablation revealed higher LV end-diastolic volume and evidence of diffuse fibrosis compared with focal atrial tachycardia patients without AiCM and healthy controls.²⁵ This underscores the importance of long-term follow-up in paediatric AiCM patients.

The rapid normalisation of BNP levels post-RFCA in our cases (e.g. from 13,787 to 20.8 pg/ml in case 3 within 4 days) reflects the acute haemodynamic benefits of arrhythmia control, while the variable time to echocardiographic recovery (3 days to 6 months) highlights the individualised nature of reverse remodelling. While short-term functional recovery is excellent, the potential for subtle, long-term sequelae (e.g. from radiofrequency lesions on the immature myocardium) is not fully known and warrants ongoing follow-up and study.

A critical consideration in our series, where all infants presented with right-sided accessory pathways, is the contribution of chronic mechanical dyssynchrony to the development of cardiomyopathy. This concept is well-established in other clinical contexts, such as the cardiomyopathy induced by frequent premature ventricular contractions or left bundle branch block, where abnormal ventricular activation leads to incoordinate contraction and systolic dysfunction.^26,27 Similarly, right ventricular pre-excitation disrupts the normal, coordinated sequence of ventricular contraction. In our cohort, the pre-excited QRS duration ranged from 107 to 120 ms, which is moderately prolonged for children and likely contributed to some degree of mechanical dyssynchrony. However, given that the QRS complex was not excessively widened, it is improbable that dyssynchrony alone was the sole driver of the severe dysfunction observed. This dyssynchrony, independent of tachycardia, leads to inefficient ventricular pumping and increased myocardial energy expenditure, thereby inducing a form of ‘dyssynchrony-induced’ or ‘pre-excitation-induced’ cardiomyopathy.²⁸

Consequently, we postulate that the myocardial dysfunction observed in our cohort likely resulted from a ‘dual-hit’ pathophysiology: the combined detrimental effects of chronic tachyarrhythmia and chronic ventricular dyssynchrony in cases 1 and 3, with the burden of persistent tachycardia likely being the predominant factor. Therefore, the dramatic recovery following successful RFCA can be attributed to the simultaneous abolition of both pathological insults – the elimination of the arrhythmic trigger and the restoration of physiological, synchronous ventricular activation.

Guo et al. specifically analysed 25 children with right-sided accessory pathways and LV dysfunction, reporting a high prevalence of ventricular wall motion abnormalities (particularly basal septal bulge).²⁹ Their work, along with that of Ko, confirms that this entity can occur even in the absence of sustained tachyarrhythmias, implicating mechanical dyssynchrony from right ventricular pre-excitation as the primary pathogenic mechanism.³⁰ The prognostic implications and time course of recovery are further elucidated by Zhang et al., who demonstrated in a cohort of 49 children that the severity of baseline cardiac dysfunction (lower LVEF, larger LV dimensions) is a key determinant of the time required for functional normalisation after successful ablation.³¹

Collectively, these studies substantiate the pathophysiological model of a dyssynchrony-induced cardiomyopathy, provide a clinical framework for its diagnosis and underscore the critical importance of early catheter ablation to reverse the deleterious remodelling process, especially in younger children who demonstrate a remarkable capacity for complete recovery. Therefore, the cardiomyopathy observed in our four infantile cases is best understood as stemming from the synergistic detriment of both persistent tachyarrhythmia and chronic mechanical dyssynchrony, with catheter ablation serving as a definitive therapy by simultaneously addressing both components of this ‘dual-hit’ pathophysiology.

It is important to note that this series exclusively involved infants with manifest right-sided free wall accessory pathways. This anatomical specificity likely contributed to the high procedural success and low complication rate observed. However, the management strategy differs substantially for infants with higher-risk substrates. For those with suspected septal pathways or concealed pathways, the risk of atrioventricular block elevates the procedural risk.³² In such cases, our institutional protocol prioritises an initial trial of intensified medical therapy.

Catheter ablation is reserved for cases of drug-refractory heart failure or life-threatening arrhythmias, where the procedural risk is justified by the disease severity. When ablation is deemed necessary in these high-risk locations, we employ enhanced safety measures, including meticulous mapping of the conduction system, low-power temperature-controlled radiofrequency applications and a strong preference for cryoablation when available, given its favourable safety profile regarding permanent conduction injury.³³

Conclusion

For infants with right-sided accessory pathway-mediated AiCM for whom arrhythmia recurs and cardiomyopathy persists despite optimised medical therapy, RFCA represents a safe and effective therapeutic option. The high success rate and absence of complications in our cases support its use in this population, despite historical safety concerns. Early intervention is crucial to maximise recovery potential, and long-term follow-up is warranted to monitor for residual myocardial changes.