Brouwer C, Hebe J, Nürnberg JH, Cosedis Nielsen J, Lukac P, de Riva M, Blom N, Zeppenfeld K.JACC Clin Electrophysiol. 2024 Jun;10(6):1050-1060. doi: 10.1016/j.jacep.2024.02.020. Epub 2024 Apr 10.PMID: 38613544
Take Home Points
- Atrial arrhythmias remain an ongoing challenge among ACHD patients even following targeted arrhythmia and substrate ablation efforts
- Atrial fibrillation in ACHD patients has distinct differences from conventional atrial fibrillation in the general population, occurring in younger adults and in the background of different atrial substrate
- Catheter ablation for atrial arrhythmias may contribute to a reduced or slower progression to development of atrial fibrillation in ACHD patients

Commentary by Dr. Philip Chang (Gainesville, FL, USA) Congenital and Pediatric Cardiac EP chief section editor:
Atrial tachyarrhythmia management is a prominent and growing component of the care of the aging ACHD population. These types of arrhythmias are often viewed along a spectrum of severity of disease, complexities in management, and long-term prognosis. Oftentimes, along the spectrum of atrial tachyarrhythmias, atrial fibrillation is viewed as one of the more advanced and complex substrates with variable long-term outcomes with antiarrhythmic therapy, catheter ablation, and surgical substrate modification. The management of atrial fibrillation is becoming an increasingly frequent issue with the growing and aging ACHD population.
Brouwer et al looked at the incidence of new-onset atrial fibrillation in ACHD patients who underwent ablative therapy for organized atrial tachyarrhythmias. The study was a retrospective multi-center analysis of outcomes in ACHD patients undergoing first-time ablation procedures to treat organized atrial tachyarrhythmias and without any prior documentation of atrial fibrillation across 3 high-volume ACHD referral centers. Consecutive patients who underwent these procedures between 2006-2016 were included. Salient information regarding CHD type and repair, atrial arrhythmia documentation and diagnosis, antiarrhythmic drug utilization, and catheter ablation was gathered. Patients were followed 3 months after ablation and then every 6 months thereafter with arrhythmia recurrence or new development of atrial fibrillation tracked.
A total of 277 patients were included (median age 37 years, 58% men). The majority of patients had moderate or complex CHD (79%). Most patients (86%) had undergone prior corrective or palliative surgical intervention. An atrial tachyarrhythmia was documented in 96% of patients. At the time of index ablation procedure, only two thirds of patients had observed or inducible atrial arrhythmias and 10% of the primary cohort had more than 1 arrhythmia substrate ablated. Of those with observed or inducible arrhythmias, just over three quarters could be characterized to define arrhythmia mechanism. Among those with defined mechanisms, 54% were cavoannular isthmus dependent flutter, 30% non-cavoannular flutter, and 16% focal atrial tachycardia. Of the remaining 23% of the primary cohort where an arrhythmia was observed or induced but could not be adequately characterized mechanistically, empiric substrate modification was performed. Intra-procedural occurrence of atrial fibrillation was seen in 27 patients (10%) either from direct pacing induction, degeneration from organized arrhythmia, or secondary to catheter manipulation. Acute ablation success defined as post-ablation noninducibility of all arrhythmias was achieved in only 52% (presumed original cohort). Over a median follow-up duration of 38 months, 52% of the post-ablation cohort experienced atrial arrhythmia recurrence. New-onset atrial fibrillation occurred in 25 patients (9%) with 10 of these patients having had acute ablation success at their index procedure. Additionally, 7 of these 25 patients had new-onset atrial fibrillation together with recurrence of atrial tachycardia. New-onset atrial fibrillation occurred on average 8 months after the index ablation procedure.
Patients who experienced new-onset atrial fibrillation were older at the time of index ablation and had higher incidence of hypertension. Those with new-onset atrial fibrillation had a higher proportion of simple CHD (52% vs. 18%). The dominant form of CHD in the new-onset atrial fibrillation subgroup was ASD. Patients with new-onset atrial fibrillation were more likely to have had multiple inducible reentrant atrial arrhythmias and more likely to have experienced atrial fibrillation during the index ablation procedure. Univariate analysis noted simple CHD, intra-procedural occurrence of atrial fibrillation, age, and age at first CHD surgery to predict new-onset atrial fibrillation. Simple CHD remained the only predictor on multi-variate analysis.
This study had several limitations related to its retrospective design. There are obviously variables that the authors could not control for that prevent a clear and conclusive assessment of the prevalence of isolated atrial fibrillation after primary ablation of documented atrial tachyarrhythmias. There are also some numerical discrepancies that could not be reconciled (ie. % patients in the original cohort who had acute ablation success), though this likely does not significantly alter or contradict other outcomes. A 9% incidence of new-onset atrial fibrillation is within the published range of atrial fibrillation prevalence in CHD patients and the authors noted other published data indicating a co-existence of atrial fibrillation and organized atrial arrhythmias in 30% of CHD patients. A lack of continuous long-term arrhythmia monitoring in the primary patient cohort leaves the possibility that some patients who were not thought to have had atrial fibrillation before could have actually experienced it without clear documentation beforehand. Similarly, it is hard to know if atrial fibrillation incidence may have differed if continuous long-term rhythm surveillance was used. For example, insufficient information was provided to know if the documented “new-onset” atrial fibrillation resulted from degeneration from an organized arrhythmia or truly a standalone atrial fibrillation event. The authors also did not provide data on whether new-onset atrial fibrillation occurred in those who had characterized or uncharacterized arrhythmias or had no observed or inducible arrhythmias at the time of index ablation. Overall, the study did not clearly demonstrate any findings to suggest that atrial fibrillation isn’t significantly tied to other pre-existing or concomitant atrial arrhythmias (something that most would agree to be the case) or that primary ablative intervention on organized atrial arrhythmias significantly reduces the risk of atrial fibrillation after.
A couple of additional findings from this study are noteworthy. First, the high percentage (approximately one third) of patients without an observed or inducible arrhythmia at the time of index ablation is somewhat surprising. Furthermore, a 52% acute ablation success rate is also quite low and may in part be due to inadequate determination of arrhythmia mechanism and identification of critical substrate. It also stands to be determined as to whether the occurrence of new-onset atrial fibrillation post-ablation reflects atrial substrate changes directly from ablation that leads to atrial fibrillation that was otherwise not seen before ablation. Lastly, the significant contribution of late-repaired ASD among those with atrial fibrillation is sobering and is in line with the general understanding of progressive atrial remodeling that occurs even in the setting of an otherwise simple CHD lesion. Prior cardiac surgery in more complex forms of CHD may confer some benefit in terms of sequestering fibrillatory tissue and activity. Catheter ablative modification of tissue to treat organized atrial arrhythmias could potentially contribute to a predisposition of developing atrial fibrillation too. These further highlight the complex and evolving atrial substrate at play, the likely higher incidence of non-pulmonary vein triggers that differentiates CHD-associated atrial fibrillation from non-CHD atrial fibrillation, and the complex interplay between CHD-related and other acquired disease-associated risk factors that result in the incidence of atrial fibrillation at a young age and higher incidence overall of this arrhythmia in ACHD patients compared to the general population.