Discussion
The present study revealed no statistical difference between CF ablation technology and traditional RF methods. There was wide variability in the total procedure time, successful lesion time, time spent mapping and ablating the pathway, and number of lesions delivered, resulting in similar averages in both cohorts. Although a trend toward higher acute success was observed in the CF group, we also saw more long-term recurrence compared to control, though neither outcome achieved statistical significance. To our knowledge, this is the first pediatric study directly comparing ablation outcomes for CF and standard RF catheters for AVRT.
There has been significant research on use of CF in the adult population, however there have been fewer pediatric studies, and even less standard of practice recommendations for use of CF. Extensive research of CF in adult atrial fibrillation shows several benefits, however through our study we saw the outcomes do not differ from using traditional RF ablation. It is difficult to tell whether these results are due to the unique pediatric population with APs, or if it reflects our early experience with this new technology and further research could elucidate statistically significant benefits from CF in pediatrics.
Contact force technology has largely been studied in adult patients with atrial arrhythmias and is overall shown to decrease procedure times and improve outcomes.2 However, even within the adult population, variation exists depending on specific study parameters and arrhythmia characteristics, as seen by Jarman et al with improved outcomes in ablation of paroxysmal atrial fibrillation, but not in non-paroxysmal atrial fibrillation.4 While some groups found that CF did not change total procedure length, fluoroscopy exposure, or one-year follow-up outcomes5,6, other studies dispute this showing CF reduced procedure times and number of touch-up ablation lesions.7 Some variation in the adult literature can be attributed to the lack of unified protocol amongst the studies. Although studies such as the TOCCATA and EFFICAS I trials attempted to consolidate and hone recommendations, different facilities are still free to use their own criteria for adequate contact force.8,9 Similarly, to date there are no pediatric specific recommendations for CF and force-time measurements for successful ablation.
Radiofrequency ablation has been used for decades in the pediatric population and newer CF technology is successfully being implemented as well, but more research on the amount of force and outcomes is required to better define the role of this technology in pediatric patients. The early research on CF in pediatrics has been mainly on safety and force recommendations. The FEDERATION study looked at the original adult protocol formed in the TOCCATA trial of 2012, and investigated the recommendations specifically in a pediatric population, concluding CF can safely be used in a pediatric population and significantly less force is needed for successful ablation.3 Although the study indicated patients with AVNRT and AVRT may not require transmural lesions, a concrete protocol for use of CF in pediatrics still does not exist and there remains minimal evidence on the benefit of CF in ablation of pediatric APs.
Currently, recommendations for transmural lesions in adult atrial fibrillation ablation include a CF of 20 g and force-time integral (FTI) > 400 gs.8 Pediatric studies have shown that less force may be necessary in ablation of APs in children, suggesting CF of 6 g and FTI of 153 gs may be sufficient.3 Children’s Wisconsin used these recommendations and operator experience to identify a protocol suggesting ideal ablations with > 3 g of force for 60 seconds or a maximum of 400 gs, but further research is needed in order to create solid CF criteria for ideal ablation outcomes. Though not statistically significant, we observed a trend towards more long-term recurrence in the CF cohort than in the control. This recurrence rate could be attributed to the Children’s Wisconsin protocol, and different criteria may improve outcomes in the future.
Only four patients (2.0% of CF and 3.9% of control patients) in our study experienced complications including mild aortic insufficiency on follow up echocardiogram, ischemia and VF secondary to ventricular pacing, cardiac perforation during transseptal puncture, and a groin hematoma. The aortic insufficiency was observed while using the Tacticath CF catheter for ablation of a left-sided pathway using a retrograde approach. Aortic insufficiency is a known complication of this approach,10 and it is unclear whether the stiffer nature of the Tacticath catheter would increase this risk. However, the remainder of the complications observed are related to the procedure itself, unrelated to the ablation catheter used, and all patients made a full recovery. Mansaur et al and several other studies have shown low complication rates using CF ablation, and the technology has been proven effective and safe both in adult and pediatric populations.2,11
The CF catheters used in our study cost approximately $1900 more than our typical non-irrigated, non-CF catheters, reflecting an almost three-fold cost difference per catheter. Given the comparable outcomes presented in our study, it is challenging to justify this additional cost in the absence of any identifiable benefit. However, should further experience and refinement of protocols using this catheter ultimately result in improved procedural outcomes and lower recurrence rates, then the overall cost-effectiveness of the catheter may improve when compared to the cost of repeat ablation procedures. Alternatively, further studies may identify particular pathway locations where catheter contact may be associated with higher recurrence rates, such as right free wall pathways, where outcomes are improved with using CF technology.12