Journal of Pediatric Cardiology and Cardiac Surgery

Atrioventricular nodal reentrant tachycardia (AVNRT) is the second most common form of supraventricular tachycardia in children after atrioventricular reentrant tachycardia.¹⁾ The mechanisms underlying AVNRT episodes are classified into the common and uncommon types. Radiofrequency catheter ablation has been recommended for treatment of AVNRT. Both the common and uncommon types of AVNRT are treated by the ablation of the slow pathway. The success rate has been reported to be ≧95%.^2, 3) However, it has been reported that the uncommon type includes numerous refractory cases and that it is associated with a high rate of relapse in comparison to the common type.⁴⁾ Furthermore, few reports have so far examined the long-term outcomes after ablation treatment. In follow-up studies of adults after ablation for AVNRT, the reported rate of relapse at 5 years ranged from 0% to 7%.^5–7) There are fewer reports on pediatric cases; such studies have reported rates of 4% to 9% at 1 year and 11% at 8 years.^8, 9) We do not know of any pediatric reports describing a longer follow-up period.

In this study we aimed to elucidate the clinical features in pediatric patients with AVNRT who underwent ablation in our institute more than 15 years prior to the present study by asking them to respond to a questionnaire.

Study population

We aimed to survey 71 patients with AVNRT who underwent radiofrequency catheter ablation (RFCA) in our institute between May 1993 and September 2001 (total number of treatments, 90). The median age of the patients at the time of treatment was 14 years (range 1–39 years); 33 patients were male, and 38 were female. When the patients were treated before 20 years of age and had current contact information, questionnaire forms were mailed to either the patients or their family members for completion; they were returned by either a self-addressed envelope or facsimile transmission. We explained the precautions taken to protect personal information, the possible risks to the respondents, and the importance of the research in an information section of the questionnaire form. In addition to direct responses from the patient, we accepted questionnaires that were filled out by relatives or guardians. This research was conducted with approval from our hospital’s ethics committee (Ethics Committee Approval No. 27-205). The questionnaire focused on the patients’ perception of palpitations despite treatment by RFCA, whether or not medical evaluations were sought because of such symptoms, and the overall satisfaction with treatment (Table 1). In addition, the questionnaire survey revealed that many patients were aware of palpitations at the time of the survey. Thus, the subjects were divided into groups according to whether or not they recognized palpitations after RFCA (Group A, palpitations present; Group B, palpitations absent) in order to clarify the clinical features associated with palpitations from their medical records. We examined and compared following characteristics: the age when RFCA was performed, gender, body mass index (BMI), history of medication prior to the procedure (e.g., digoxin, verapamil, disopyramide, and cibenzoline), presence or absence of congenital heart disease, endpoint of RFCA, type of AVNRT, and repeat ablation.

The Mailing and Return of the Questionnaires

Seventy-one patients with AVNRT underwent ablation (90 sessions) in our department (Fig. 1). We excluded 9 patients whose addresses were unknown and 11 who were ≧20 years of age at the time of ablation. The questionnaires failed to reach 17 of the remaining 51 patients because of a change of address. Eleven other potential subjects did not reply. Ultimately, 23 responses were received from the 51 patients (45%). The median time from the date of ablation to the date on which the questionnaire was 223 months (range 175–275 months).

Fig. 1 The mailing and the return of the questionnaires

The return rate was 45%, with 23 subjects providing informative responses.

Replies to the Questionnaire

All respondents had sensations of palpitation prior to ablation. The results pertaining to palpitation after ablation are shown in Fig. 2. Twelve of the 23 respondents still sensed some palpitations after ablation (52%). Five of these twelve did not seek medical attention, while seven went to a hospital for evaluation. In 4, no arrhythmia was detected, and no diagnosis was made. Two of the 3 remaining subjects who sought evaluation were diagnosed with relapse; the other patient was diagnosed with a different arrhythmia. Due to the presence of these respondents, the long-term relapse rate of AVNRT after RFCA at our hospital was 9%. Fig. 3 shows the satisfaction with treatment. Twenty-two of the 23 respondents (96%) said that they were satisfied. With regard to the reasons for satisfaction, 13 respondents mentioned that they were satisfied because they did not need to regularly visit a hospital; 11 said that they no longer felt anxious—these responses were given by approximately half of the respondents. The next most popular responses were “no restriction of exercise” (n=6) and “no longer require medicine” (n=4)—these responses were given by approximately one-fourth of respondents. Only 1 subjects listed “decrease in tachycardia” under the other reasons.

Fig. 2 Palpitations after ablation

Twelve subjects experienced palpitations despite treatment. Seven of them visited a hospital for evaluation. Two of these subjects were diagnosed with relapse, while four received no diagnosis because no arrhythmia was detected at the time.

Fig. 3 Satisfaction with treatment

Ninety-six percent of the subjects were satisfied with the ablation treatment. Nearly half of the subjects stated that they were satisfied because they no longer needed to regularly visit the hospital, or because their disease-related anxiety was decreased.

Findings Associated with the Persistence or Absence of Palpitations (Table 2)

We did not identify any significant differences between the two groups in terms of age, gender, or BMI. The same was true for the satisfaction with treatment, which was reported by 11 respondents (92%) in Group A and 11 respondents (100%) in Group B. Hospital evaluation was sought by 7 respondents in Group A (58%) but none in Group B. Group A included 7 patients who were treated with medication prior to ablation (58%), while Group B included 1 such patient (9%). There was a significant difference (p<0.05). On the other hand, in regard to the presence or absence of congenital heart defects, the endpoint of RFCA, the type of AVNRT and repeat ablation, there were no significant differences between two groups. Two patients in Group A were diagnosed with relapse upon assessment at a hospital after the ablation.

In the present survey, 96% of the respondents reported that they were satisfied with their treatment. We previously found that 98% of the respondents were satisfied after ablation treatment for Wolff-Parkinson-White (WPW) syndrome.¹¹⁾ Many AVNRT patients mentioned that they were satisfied with their treatment because they no longer needed to regularly visit a hospital; this was followed by reduced anxiety about attacks. The latter reason was also mentioned by our WPW syndrome patients. Prior to treatment, patients with WPW syndrome are typically warned about possible sudden death from untreated WPW syndrome. While anxiety has been reported to increase after the treatment of various reentrant tachycardias,¹²⁾ our present respondents who were treated for AVNRT often cited their reduced anxiety about attacks as a reason for their satisfaction.

Even though 96% of our subjects were satisfied with their treatment, over half of our AVNRT patients still experienced some palpitations. This was higher than the proportion of patients who reported palpitations after ablation for WPW syndrome (28%).¹¹⁾ We were able to contact 5 of the 12 respondents who still had palpitations after RFCA by telephone. Among these subjects, 3 considered the palpitations to be the same sort that they had experienced before ablation, while the remaining 2 reported that the continuing palpitations were considered to be premature beats. Overall, we considered the persistence of palpitations to be a useful indication for an electrophysiological study to investigate the possible relapse of AVNRT, and—if indicated—to perform retreated.

In our survey, the long-term relapse rate in patients with AVNRT was higher than that of WPW syndrome we reported before (9% vs 0.5%).¹¹⁾ While the relapse of WPW syndrome can be diagnosed by identifying a delta wave on an electrocardiogram (ECG), patients with AVNRT show normal ECG findings, except when they experience a clinical attack. All the more reason, it is important to pay attention to a clinical symptom even after a successful RFCA.

We divided subjects into two groups according to whether or not they recognized palpitations after RFCA and compared their clinical features. A significant difference was found between two groups in the medications taken prior to the ablation. Seven of the patients in Group A took some medicines. In three of them, the reason why they take medication was anxiety which may have a tachycardia attack again. Among them, two took verapamil only when they have a tachycardia attack. One patient who had a premature ventricular contraction (PVC) as a comorbidity required medication for PVC. One patient took digoxin although we do not know the reason. The remaining three patients were complicated cases. One patient was diagnosed to have ventricular septal defect (VSD) and underwent tricuspid valve replacement after VSD closure. The remaining two patients were uncommon AVNRT. In other words, the patients who complain of palpitations after RFCA were more likely to have anxiety before RFCA and complicated case. In this study, many patients have reported their palpitations after long passage as 15 years. Although our hospital has finished regular follow-up in 5 years after RFCA, we have to create a system such as the patients can be re-examined long after the RFCA.

Limitations

In this study, we demonstrated the long-term clinical features of AVNRT after RFCA. However, there were some limitations. First, this study is based on a questionnaire survey and investigates the clinical features of the remote period. Therefore, long-term results after RFCA cannot be mentioned. Second, since less than half of the subjects responded to the questionnaires, the answers might not have been representative of the larger group. Third, many patients who reported palpitations did not undergo ECG assessments, which leaves open the possibility that our analysis might have missed some subjects with relapse. When possible, we sought to increase our accuracy with respect to this issue by conducting telephone interviews with the subjects who experienced palpitations.

Although more than half of the AVNRT patients in the present study still were aware of palpitations after ablation, many patients were satisfied with the treatment. Even though the causes of continued palpitations were often not elucidated, some relationship existed between persistent palpitations and a history of anti-arrhythmic medication prior to ablation. In patients with AVNRT, relapse should be suspected when palpitations recur or persist, and electrophysiological studies should be performed when necessary.