Long‐term follow‐up in preschool children after radiofrequency catheter ablation of arrhythmias

Abstract Background Radiofrequency ablation (RFA) is the standard method of treatment for tachyarrhythmias in school children, and it leads to complete recovery in children without structural heart disease. However, RFA in young children is limited by the risk of complications and unstudied remote effects of radiofrequency lesions. Objective To present the experience of RFA of arrhythmias and the results of follow‐up of younger children. Materials and Methods RFA procedures (n = 255) were performed in 209 children with arrhythmias from 0 to 7 years old. The arrhythmias were presented with atrioventricular reentry tachycardia with Wolff‐Parkinson‐White (WPW) syndrome (56%), atrial ectopic tachycardia (21.5%), atrioventricular nodal reentry tachycardia (4.8%), and ventricular arrhythmia (17.2%). Results The overall effectiveness of RFA, considering the repeated procedures performed due to the primary ineffectiveness and recurrencies, was 94.7%. There was no mortality associated with RFA in patients, including young patients. All cases of “major” complications are associated with RFA of the left‐sided accessory pathway and tachycardia foci and are represented by the mitral valve damage in three patients (1.4%). Tachycardia and preexcitation recurred in 44 (21%) patients. There was a correlation between recurrences and parameters of RFA (odds ratio 0.894; 95% confidence interval: 0.804–0.994; p = .039). Reducing the maximum power of effective applications in our study increased the risk of recurrence. Conclusion The use of the minimum effective parameters of RFA in children reduces the risk of complications, but increases arrhythmia recurrence rate.

extrasystole with high daily burden 25% with episodes of unstable ventricular tachycardia.
Paroxysmal course of tachycardia was observed in 118 patients (68% of all SVT). Most of such tachycardias were presented by AVRT with WPW syndrome and AVNRT. Sustained tachycardia occurred in patients with atrial ectopic tachycardia (n = 47.3%). Incessant atrial ectopic tachycardia was observed in eight patients (5%) at the age of 1 year old. 4 Heart failure signs were observed in 43 patients (20.6%), of which functional class (FK) IV-in 2 patients, III FK-in 13 patients, and II FK-in 28 patients (Table 1) There were 108 (51.7%) cases of cardiac dysfunction. In 48 (23%) patients, there was reduced EF. Decreased LV EF considered as <55%, EF was assessed by Simpson. Twenty percent of patients had increased LV EDV > 120% of normal, 38% had increased LA volume >130% of normal, and 35% had increased RA volume >130% of normal.

| Technology of intracardiac EPS and RFA
Intracardiac EPS and RFA were performed with well-balanced total intravenous anesthesia that provided by continuous infusion of F I G U R E 1 Age distribution. Heparin 50 units/kg therapy with further intake of low-dose aspirin during 3 weeks for thromboembolic complications prophylaxis was used at RFA of left-sided arrhythmia substrates.

| Postoperative observation and follow-up
All patients after RFA were observed in an intensive care unit with continuous electrocardiographic monitoring during 24 h. The first control examination including electrocardiogram (ECG), Holter monitoring, and Echo was performed in 5-7 days after RFA and then in 1, 3, 6, and 12 months. The follow-up was 5.7 ± 2.9 years (from 1.5 to 10 years).

| Statistical analysis
Statistical analysis of the given data was carried out using STATISTICA 6.0 for Windows. The description of quantitative characteristics, the distribution of which did not correspond to the normal law, is presented in the form of a median (Me) and IQR. If the quantitative characteristics had normal distribution, their description is presented in the form of (M ± σ). The rating description was performed by the contingency table with absolute and relative frequency (%) of characteristics. To determine statistically significant differences in nominal characteristics, the analysis of contingency table was used (Pearson χ 2 criteria, two-sided Fisher exact test). The comparison of two independent samples was performed by Mann-Whitney test.
p < .05 was considered as statistically significant difference. The calculation of the probability of realization of an unfavorable prognosis and identification of significant predictors of an unfavorable outcome were carried out by the multivariate logistic regression analysis with direct stepwise inclusion of variables into the model.

| Indications for RFA
Symptomatic arrhythmia, reduced cardiac function, heart failure signs, and refractoriness to antiarrhythmic therapy (AAT) are the indications for RFA. 5 The choice of ablation method of arrhythmia treatment by the parents in case of their refusal to get preventive AAT and limit children in sports was the indication for RFA in six children aged 5-7 years. WPW syndrome occurred in all these patients.

| Previous AAT
AAT as the first stage of the treatment was used in all patients.
Antiarrhythmic drugs were prescribed by a selective method: If one drug was ineffective, another was prescribed. 6 In average, each patient got three drugs consecutively (from 1 to 5). The duration of therapy with each drug ranged from 2 weeks to 3 months.
With ineffective monotherapy, the combined therapy was prescribed: amiodarone + propranolol, amiodarone + digoxin, and propafenone + propranolol. AAT in the given patient group was ineffective or had only a temporary effect consisting in decrease of heart rate (HR) during first days of tachycardia treatment. Later, HR reached the initial tachycardia level, and cardiac dysfunction continued to progress that was the indication for RFA.

| Efficacy and complications of RFA
The overall efficacy of RFA in all patients including repeated procedures performed due to ineffective primary RFA and recurrences was 94.7%. RFA efficacy in children under 1 year of age was 96%.
There was no mortality associated with RFA.
During RFA, injury of the mitral valve (MV), considered as a "major" complication, occurred in three patients with left-sided accessory pathway (1.4%; 3/209), among which the age of one patient was 6 months and two-7 years. At the age of 4, the first patient required MV repair in 3.5 years after RFA due to III grade mitral regurgitation and heart failure. MV revision discovered two clefts-of anterior leaflet in A1 segment and of posterior leaflet in P1 segment.

| Arrhythmia recurrences
Tachycardia and preexcitation recurred in 44 (21%) patients. In 20 children, the recurrences occurred in the first 5 days after RFA, in 24-from 5 days to 6 months. Clinical characteristics of patients with recurrences are presented in Table 2  The time of recurrence after primary RFA, months (Ме(IQR)) 0.5 (0.1-2.0) The interval between primary and repeated RFA, months (Me (IQR)) 6.0 (3.0-17.0) Recurrences in children with WPW syndrome (n; % in the given arrhythmia group)

21; 18%
Recurrences in children with atrial tachycardia (n; % in the given arrhythmia group)
"major" complications were avoided in our study. They also were not observed in patients with transient intraoperative AV conduction disorders during follow-up.
In our study, "major" complications were associated with leftsided localization of arrhythmias and catheter manipulations in the MV. The technology and equipment require improvement considering the need to accompany the RFA procedure with imaging methods, since such complications are usually disclosed after RFA.
Intracardiac echocardiography is used during RFA in adult invasive arrhythmology. However, in pediatric population with weight less than 30 kg, the use of the technique is limited by the necessity of additional venous access and catheter size 9Fr. 18  The comparison of our results with previous studies with RFA outcomes in younger children allows us to conclude that along with the minimum number of "major" complications, we got a sufficiently high recurrence rate that required repeated procedures and ensured a high overall RFA efficacy in our patients. It is well known that the risk of injury and perforation of myocardium is inversely related to the age and weight of the patient. The factors reducing the risk of catheter treatment of arrhythmias in children are the experience of the electrophysiologist associated with delicate catheter manipulation in small children due to thin walls and small chambers of the heart and minimally effective parameters of radiofrequency exposure.

| CON CLUS ION
The most serious "major" complications are associated with the left-sided localization of the focus of arrhythmia or accessory pathway. Therefore, the choice of management of such patients should be carried out considering the "risk" and "benefit" factors of RFA in each particular case, even if the clinic has considerable experience. The use of echocardiography during RFA of left-sided