Transcatheter ablation is an effective method to eliminate the arrhythmogenic substrate in symptomatic children with various types of arrhythmias. A reduction in the procedure and fluoroscopy time would decrease the hazardous effects of the ablation procedures. The magnetic navigation system (MNS) uses atraumatic catheters and facilitates accurate catheter placement in all regions of the heart for mapping and therapy delivery. We compared the efficacy and safety between a manual and MNS-guided approach for mapping and ablation of arrhythmias in a general pediatric arrhythmia population and in a subgroup of young children aged <10 years old. A total of 58 pediatric patients (mean age 12.2 ± 3.2 years) were included in the present study. Of the 58 consecutive patients, 29 were treated with the MNS and 29 underwent conventional manual ablation. No demographic differences were present between the 2 groups. Acute success was achieved in 26 of 29 patients and 27 of 29 patients (p = NS). The mean procedure and fluoroscopy times were comparable in both study groups (168 ± 56 minutes vs 183 ± 52 minutes, p = NS; and 22 ± 59 minutes vs 30 ± 29 minutes, p = NS). In young children (aged <10 years), the success rate did not differ between the 2 groups (10 of 11 vs 6 of 8, p = NS). However, significant decreases in the procedure and fluoroscopy times were achieved (139 ± 57 minutes vs 204 ± 49 minutes and 13 ± 7 minutes vs 31 ± 28 minutes, respectively; p = 0.01 and p = 0.04). In conclusion, our data have strongly suggested that using the MNS for treating young children is advantageous, because it significantly reduced the procedure and fluoroscopy times without compromising efficacy.
Transcatheter ablation is an effective method for eliminating the arrhythmogenic substrate in symptomatic children with various types of tachyarrhythmias. Safety is without a doubt a crucial issue in these young and vulnerable patients. However, in small children, only a limited number of dedicated devices (i.e., significantly smaller and with specially designed curves) are available for ablation procedures. A reduction of procedure and fluoroscopy times would decrease the risks of ablation such as complications and the potential long-term effects of radiation exposure, such as leukemia and a whole spectrum of solid cancers. The magnetic navigation system (MNS, Niobe, Stereotaxis, St. Louis, Missouri) combines several possible advantages. It uses atraumatic catheters with superior navigation capabilities. The omnidirectional positioning of the catheter tip eliminates the specialized curves for this patient population and allows targeting of all regions for mapping and therapy delivery. In our study, we compared the efficacy and safety between the manual and MNS-guided approaches for mapping and ablation of tachyarrhythmias in a general pediatric population and in a subgroup of young children.
Methods
In our center, patients were recruited from an ongoing registry of all children with complex arrhythmias. Patients treated using the MNS were included consecutively into the present study from the point at which the MNS was introduced into our hospital for ablation of pediatric patients. All pediatric patients were treated with the MNS from that point onward. A control group of manually ablated patients was accumulated in the same consecutive fashion during the period directly before the introduction of the MNS. As a result, patients with different tachyarrhythmias were included in the study, and only those with a parahisian substrate were excluded. The parents of the patients <18 years old provided informed consent. Amiodarone was discontinued for ≥1 month, and all other antiarrhythmic agents were discontinued for ≥5 half lives before the procedure. The operators were the same for both groups. All procedures were performed with the patient under general anesthesia. Data were collected regarding procedural time, use of fluoroscopy, acute success, and procedure-related complications. The procedural time was measured from the time of puncturing the vein to the time of removal of the sheaths from the groin, including the 30-minute waiting period after successful ablation.
The diagnosis of dual atrioventricular nodal pathways, atrioventricular nodal re-entrant tachycardia, circle-mediated tachycardia, or atrial tachycardia was made using standard diagnostic criteria. In patients suspected of having atrial tachycardia, a 3-dimensional electroanatomic voltage and/or activation map (CARTO, Biosense-Webster, Diamond Bar, California) was constructed.
Manual RF catheter ablation was performed using a 4-mm, solid-tip, ablation catheter (Biosense-Webster) in a temperature-controlled mode (maximum temperature 55°C, maximum duration 60 seconds, maximum energy 40 W) using a Stockert RF generator (Biosense-Webster).
Catheter ablation using the MNS was performed using a 4-mm tip catheter (Celsius RMT or Navistar RMT, Biosense-Webster) using the same Stockert RF generator (Biosense-Webster). The principles and use of the MNS have been extensively described previously by our group.
In patients with atrioventricular nodal re-entrant tachycardia, our target was elimination of the slow pathway. The ablation was guided using a combination of fluoroscopic images and electrograms. The procedural end point was defined as noninducibility of the tachycardia. Inducibility was tested after each application. If the arrhythmia was noninducible, the test was repeated after a 30-minute waiting period. The procedure time was recorded from the moment of puncturing the femoral vein in the electrophysiology laboratory until removal of the sheath from the femoral vein, including the 30-minute waiting period.
In patients with atrial tachycardia, a 3-dimensional electroanatomic voltage and/or activation map (CARTO RMT, Biosense-Webster) was created. The procedural end point was again defined as noninducibility of the tachycardia. The procedural time was measured in the same fashion and also included the 30-minute waiting period.
In patients with circle-mediated tachycardia, the objective of the ablation was abolition of conduction over the accessory pathway. The procedural time was measured in the same fashion and also included the 30-minute waiting period.
At 24 hours after receiving treatment, the patients were re-evaluated clinically and an electrocardiogram and transthoracic echocardiographic examination were performed.
Continuous variables are expressed as the mean ± SD if normally distributed, or otherwise by the median. The Student t test or analysis of variance was used when appropriate for continuous variables, and the chi-square test was used to compare categorical data. The level of significance was set at p <0.05. All statistical analyses were performed using Statistical Package for Social Sciences, version 16.0 for Windows (Chicago, Illinois).
Results
A total of 58 pediatric patients (mean age 12.2 ± 3.2 years) were included in the present study. Of the 58 patients, 29 consecutive patients were treated with the MNS and 29 consecutive patients underwent conventional manual ablation. No demographic differences were present between the 2 groups ( Table 1 ).
| Variable | MNS (n = 29) | Manual (n = 29) |
|---|---|---|
| Age (years) | 12.1 ± 3.0 | 12.3 ± 3.4 |
| Weight (kg) | 28 ± 4.0 | 30 ± 4.5 |
| Males | 14 (48%) | 16 (55%) |
| Atrioventricular nodal re-entrant tachycardia | 4 (14%) | 7 (24%) |
| Atrial tachycardia | 3 (10%) | 1 (3%) |
| Right-side accessory pathway | 10 (34%) | 11 (39%) |
| Left-side accessory pathway | 12 (42%) | 10 (34%) |
| Procedural time (min) | 168 ± 56 | 183 ± 52 |
| Fluoroscopy time (min) | 22 ± 59 | 30 ± 29 |
| Acute success | 26 (90%) | 27 (93%) |
| Complications | 0 | 0 |
Acute success was achieved in 26 of 29 and 27 of 29 patients in the 2 groups (p = NS). The mean procedure and fluoroscopy times were not different between the 2 study groups ( Table 1 ). No complications occurred. A subgroup analysis was performed selecting only young children aged <10 years ( Table 2 ). The success rate did not differ between the 2 groups (10 of 11 vs 6 of 8, p = NS). However, a significant decrease in the procedure and fluoroscopy times was achieved (139 ± 57 vs 204 ± 49 minutes and 13 ± 7 vs 31 ± 28 minutes, p = 0.01 and p = 0.04, respectively).
| Variable | MNS | Manual |
|---|---|---|
| Patients (n) | 11 (58%) | 8 (42%) |
| Age (years) | 8.9 ± 1.0 | 7.8 ± 3.0 |
| Atrioventricular nodal re-entrant tachycardia | 1 (9%) | 0 |
| Atrial tachycardia | 3 (27%) | 0 |
| Right-sided accessory pathway | 5 (45%) | 3 (38%) |
| Left-sided accessory pathway | 2 (19%) | 5 (62%) |
| Procedural time (min) | 139 ± 57 ⁎ | 204 ± 49 ⁎ |
| Fluoroscopy time (min) | 13 ± 7 † | 31 ± 28 † |
| Acute success | 10 (91%) | 6 (75%) |
| Complications | 0 | 0 |
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