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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