Discussion
This is a retrospective study of catheter ablation in children encompassing 68 procedures performed over 20 years. This study reviewed the indications and outcomes in pediatric population at a tertiary care center in underdeveloped country. Moreover, it provides information that will further enhance the limited body of knowledge on catheter ablation in our region.
Cardiac ablation, using different types of energy (radiofrequency and cryoablation), has been used for treatment of specific pediatric arrhythmias. Today, it is performed in tertiary centers in developed countries for specific types of arrhythmias with excellent results [11]. In our retrospective study, we looked over a span of 20 years, and described our experience in correlation with patient demographic, types of arrhythmias, presence of structural heart disease and complications associated with such procedure within this population.
According to a study involving 623 individuals who underwent invasive electrophysiologic testing for various tachycardias, it was found that AVNRT was twice as prevalent in women. In contrast, atrial tachycardia affected both genders equally. Conversely, AVRT, atrial fibrillation (AF), and ventricular fibrillation (VF) were more frequently observed in men [12]. The distribution patterns of supraventricular tachycardias (SVTs), AF, VF, and sudden death showed similar trends in the Framingham cohort [12]. Our findings reveal that most patients undergoing cardiac ablation were males (60%). In addition, it aligns with previous studies that have shown a higher prevalence of arrhythmias treated with cardiac ablation in males[6].
Moreover, the mechanisms of arrhythmia in adults and children with structurally normal heart are essentially the same [13]. Consequently, the major types of arrythmia seen in the pediatric population are generally seen in adults, which include accessory pathways, ectopic atrial foci, and dual AV nodal physiology. On the other hand, the arrhythmia in those with structurally heart disease is usually related to the underlying abnormality itself, the chronic hemodynamic stress or secondary to surgical intervention and/or scars [13].
In our study, the subtypes of SVTs were WPW, AVRT and AVNRT. Of the 19 patients with WPW who underwent ablation, 18 had acute success with no recurrence. This 95% success rate is positively comparable to that reported in big multicenter study with success rate of 91% [14]. Another type of reentrant tachycardia encountered in our series was AVNRT, the most common type of SVT, by which AV node would have both slow and fast fibers leading to reentrant tachycardia [15]. In our study, 12 patients with AVNRT had a 100% acute success rate of ablation which is close to the success rate of AVNRT ablation reported in children in other studies, which is around 99% [16]. Out of those 12 patients, one patient had recurrence of symptoms, and was successfully ablated the second time with no further recurrence, making the overall recurrence rate 1.5%. This is lower than that reported in other studies with a recurrence rate of 10.9% [26]. Atrial fibrillation is the most common type of cardiac arrythmia overall but has low prevalence in the pediatric population. Multiple mechanisms have been described to play a role in development of (AF), with the most common one being atrial remodeling. This results in electrical changes that cause deranged rhythm. It starts with a trigger exciting an ectopic focus usually around the pulmonary vein in the atria, this allows for an unsynchronized firing of electrical impulses causing fibrillation of the atria [17, 18]. AF was encountered only in two of our patients with CHD, one with TOF and other with VSD and PFO, and the ablation in both cases was successful.
Although some high-volume center-based studies showed that ablation success rate tends to be less successful in pediatrics with congenital heart disease [7, 8, 19, 20], it is still considered a safe and effective treatment option [10]. The incidence of structural heart disease was low accounting for only 6% of our studied population. Ventricular tachycardia remains one of the drastic events following TOF surgical repair as it can lead to sudden death [21]. In addition, VT resulting from TOF repair has the highest risk of recurrence and makes it challenging to prevent. Radiofrequency ablation for VT in those patients has been shown to decrease the risk of ICD shocks if done prior to device implantation [22]. In our study, patients with TOF had successful initial ablation. Nevertheless, they could not be maintained off medications, and they eventually needed an ICD insertion.
Ventricular tachycardia in the pediatric population could be related to underlying structural heart disease or idiopathic in structurally normal hearts. In one study, it was shown that VT mortality was more prevalent in patients with heart disease compared to those with a normal heart. In addition, VT in those with a normal heart had a better prognosis [23]. Another study showed that Antiarrhythmic therapy effectively abolished ventricular tachycardia in symptomatic children but was less effective in asymptomatic ones [24]. This raises a consideration regarding the usage of cardiac ablation not only in those with who are symptomatic or with underlying structural heart, but for asymptomatic patients with normal heart structure as well. VT had the highest ablation failure rate in our study (29%), this was reported in other studies reaching a success rate of 60% in pediatrics with or without CHD [25].
Abortion of ablation procedure occurred in 9 patients out of the 67 with rate of 13%, reasons were due to negative confirmatory EP studies (1), high risk arrythmia location (1), failure of SVT induction (6) or uncovering of new accessory pathways (1). Other causes of abortion reported include unstable VT. Morwood et al reported on anatomic obstacles as the reason behind VT ablation abortion to be as high as 34% [25]. In another study, the major factor unfavorably affecting the ablation outcome was the presence of congenital heart disease [26].
Medications were chronically administered to 59% of the population prior to the procedure. Medications at discharge were prescribed for (41%) and stopped after a period of two weeks to one month in 86%. This was to prevent any new arrhythmia or recurrence due to the temporary inflammation that results from the ablation [27].
Lastly, successful ablation was reached in 93% of our study population. This outcome is similar to success rates reported in several studies [8, 10].We had one recurrent case (1.5%), that was re-ablated successfully. A study by Kato et al10 showed that CHD patients had a significantly higher recurrence rate (24%) compared to patients without CHD. In addition, they showed that of the 877 patients studied, 94% were successfully treated after the first ablation, and recurrences occurred in 15% of patients. Furthermore, recurrence of arrhythmias after the first ablation was found to represent new electrophysiological focus in 26% of patients who underwent repeat electrophysiology studies [20].
Limitations
Our study is a retrospective study that looked at patients from one center. It was limited due to the small number of patients that underwent cardiac ablation and those that had structural heart disease.
We do recommend that more studies are needed for this specific population and the different treatment modalities in the Middle East.
Conclusion
The findings from this study, which encompassed a cohort of pediatric patients undergoing cardiac ablation, demonstrate a notable success rate of 93% in the treatment of arrhythmias. This observation underscores the effectiveness of cardiac ablation as a viable therapeutic option for managing childhood arrhythmias, in structurally normal and abnormal hearts in developing countries. Our study also highlights the complexity and potential complications associated with these procedures. Hence, it contributes to the existing body of knowledge on arrhythmia management, especially in a developing country where such evidence is scarce and where further research in this field is needed.
Ethical Considerations
This study was approved by the Institutional Review Board (IRB) at the American University of Beirut.
Acknowledgements:
We thank Dr. Dr. Hani Tamim and Ms Walaa El Sheikh for their contribution in the statistical analysis of the Data.
Conflict of interest statement: None declared.
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