Long Term Outcomes of Pediatric Patients After Catheter Ablation for Possible Arrhythmia Induced Cardiomyopathy

Technical Summary: Long Term Outcomes of Pediatric Patients After Catheter Ablation for Possible Arrhythmia Induced Cardiomyopathy

Problem Statement
Arrhythmia-induced cardiomyopathy (AiCM), also known as tachycardia-induced cardiomyopathy (T-CM), is a reversible condition where sustained arrhythmias lead to left ventricular (LV) dysfunction and heart failure in pediatric patients. A significant clinical challenge exists because the diagnosis of AiCM is often retrospective; it can only be confirmed once LV function recovers following the control of the underlying arrhythmia. This creates difficulty in distinguishing AiCM from genetic cardiomyopathies that present with secondary arrhythmias, particularly when slow tachycardias are undocumented prior to presentation. Consequently, many pediatric patients with severe LV dysfunction are initially misdiagnosed with idiopathic dilated cardiomyopathy (DCM) and may be considered for heart transplantation before the reversible nature of their condition is recognized.

Methodology
This study is a single-center, retrospective analysis conducted at the Royal Children's Hospital in Melbourne, covering patients who underwent catheter ablation for presumed AiCM after January 2011.

• Cohort: 20 patients (10 female) were included. The median age at presentation was 6.1 years (range 0–15.2), with two neonates.
• Inclusion Criteria: Patients presented with decreased LV function (LVEF < 50%), dilated LV (LVEDD Z-score ≥ 2 SD, with one exception included due to clinical picture), and a confirmed arrhythmia.
• Arrhythmia Types: The cohort included Atrial Ectopic Tachycardia (AET, n=8), Permanent Junctional Reciprocating Tachycardia (PJRT, n=6), Ventricular Tachycardia (VT, n=3), Premature Ventricular Contractions (PVC, n=1), Atrial Flutter (n=1), and Atrioventricular Reciprocating Tachycardia (n=1).
• Procedural Context: Eight patients (40%) presented with mechanical circulatory support (MCS), including 5 on Extracorporeal Membrane Oxygenation (ECMO) and 3 on Left Ventricular Assist Devices (LVAD). Four patients (20% of the total cohort) underwent the ablation procedure while on MCS.
• Definitions: Successful ablation was defined as the elimination of the documented arrhythmia resulting in LV functional recovery (LVEF ≥ 50%) and/or the discontinuation of antiarrhythmic medication.
• Follow-up: The median follow-up duration was 5.2 years.

Key Results

• Ablation Success: Overall long-term control of arrhythmia was achieved in 17/20 patients (85%). Primary ablation success (first session without recurrence) was achieved in 13/20 patients (65%).
• Functional Recovery: Overall, 19/20 patients (95%) demonstrated normal cardiac function by the end of the study period.
  • One patient (6.6-year-old male with AET) had successful ablation but failed to recover LV function. Genetic testing later revealed a pathogenic TNNT2 variant, confirming a genetic cardiomyopathy, and the patient subsequently required a heart transplant.
  • One neonate with PJRT underwent ablation under ECMO support which resulted in complete AV block requiring a pacemaker; however, this patient achieved successful functional recovery.
• Recurrence: Three patients (15%) experienced arrhythmia recurrence within six months. All three were successfully managed with a second ablation session or continued medical therapy, eventually achieving arrhythmia control.
• Mechanical Support Outcomes: Among the 8 patients who presented with MCS, 5/8 (63%) achieved successful ablation outcomes overall. Specifically, 4/8 patients achieved success in the first session (4/8, 50%), while others required a second session (one under LVAD, one after coming off ECMO).
• Complications: There was one significant complication (AV block in a neonate on ECMO), representing a 13% severe complication rate in the MCS subgroup, which the authors note is comparable to previous studies.
• Long-term Prognosis: No patients were readmitted for heart failure symptoms after the initial presentation. While six patients were initially referred for heart transplantation, five recovered function following ablation.

Significance and Claims
The authors conclude that catheter ablation is a highly effective treatment for pediatric patients with suspected AiCM, even in high-risk scenarios involving small body weight and severe ventricular dysfunction requiring mechanical circulatory support.

• Reversibility: The study reinforces that AiCM has a favorable prognosis with 95% of patients maintaining normal LVEF and LVEDD once the causative arrhythmia is controlled.
• Diagnostic Caution: The paper highlights the critical importance of suspecting AiCM to avoid unnecessary heart transplant listings. However, it also notes that patients who fail to recover function despite successful arrhythmia control should be evaluated for underlying genetic cardiomyopathies, as secondary arrhythmias can mimic AiCM.
• Pediatric vs. Adult Differences: Unlike adult populations with atrial fibrillation-induced cardiomyopathy, where arrhythmia recurrence frequently leads to heart failure relapse, the pediatric cohort in this study showed no recurrence of heart failure despite arrhythmia recurrences, which were manageable with repeat ablation or medication.

The study suggests that while the diagnosis of AiCM remains retrospective, early intervention with catheter ablation offers a high success rate for functional recovery in children, provided that genetic causes are ruled out in non-responders.