Janson CM, Shah MJ, Kennedy KF, Iyer VR, Behere S, Sweeten TL, O’Byrne ML.
JACC Clin Electrophysiol. 2023 Jan;9(1):73-84. doi: 10.1016/j.jacep.2022.08.023. Epub 2022 Nov 30.PMID: 36697203
- Overall ablation success for pediatric WPW remains very high with very low incidence of major adverse events based on contemporary national registry data
- Pediatric WPW patients <30kg appear to have higher ablation success rate than those >30kg, but incidence of adverse events is also higher
- Contemporary ablation outcomes for pediatric WPW < or >30kg appear to reflect ablation referral practices, even among high volume centers
Commentary by Dr. Philip Chang (Gainesville, FL, USA) Congenital and Pediatric Cardiac EP section editor:
Catheter ablation for WPW remains the best option for cure. Among pediatric patients, variability in the timing of performance of ablation exists, with a general consideration toward waiting to perform ablation procedures at an older age or bigger size to minimize the risk of procedural complications. Outcomes vs. complications from ablation procedures in smaller patients has been difficult to study given overall low numbers of procedures from individual centers.
Janson et al performed a retrospective multi-center analysis of pediatric WPW ablation using data collected from the IMPACT registry. Among all entries in the IMPACT registry, cases for patients 1-21yo in age undergoing first-time EPS between April 2016 and December 2019 were included. Inclusion was limited to structurally normal hearts and only 1 pathway ablation target. Available deidentified data collected from participating centers as part of the IMPACT registry data elements were used for descriptive and comparative analyses. Smaller patients were defined as those <30kg, as the 30kg value was 1 standard deviation below the mean weight among all included subjects in the IMPACT registry. The authors evaluated basic clinical variables, accessory pathway locations, findings from EP testing, mode of ablation delivery, acute outcomes, and reported complications/adverse events among patients > or <30kg that were available as part of the registry data elements.
Out of 18,043 cases in the registry, a total of 4,456 from 84 centers met inclusion criteria. Figure 2 from the publication shows the distribution of weights among included pediatric WPW cases, with only 14% comprising the <30kg cohort.
Center-to-center variability in weights varied widely regardless of procedural volume (high volume defined as >100 WPW cases during the inclusion period). Among the entire study cohort, a majority (57%) were male with mean age of 13.1 years and mean weight of 56kg. Patients <30kg were more likely to have pre-procedural documented SVT and to be on pharmacologic rhythm control. The <30kg group also exhibited higher incidence of SVT inducibility during EP testing and a different distribution of pathway locations with higher frequency of left sided non-septal locations and lower frequency of right septal pathways. Subjects >30kg had a higher incidence of AF induction during EP testing.
Procedural outcomes differed between weight groups, with significantly higher acute success in <30kg and a higher incidence of adverse events. Table 3 lists the types and incidence of specific adverse events between both weight groups. While the incidence of major adverse events differed significantly (0.3% vs. 0.05%, p 0.04), no cases of permanent AV block occurred and there were no deaths.
The incidence of deferring ablation (ie. EP testing only but no ablation attempt) was similar between both groups. Usage of cryo and RF+cryo were also similar between both groups, with cryo usage significantly higher only for CS pathway locations in the <30kg group. The use of irrigated RF ablation catheters was significantly lower in <30kg patients.
The overall distribution of acute success based on pathway location were higher for <30kg patients, with significantly higher success rates for CS pathways. The composite failed or deferred ablation rate was significantly higher in >30kg patients (19% vs. 14%, p 0.001, Table 4). Multivariable modeling showed that <30kg remained a predictor for acute success, while RF+cryo usage and non-left free wall pathway locations were predictors of failure.
The authors performed additional analyses of weight vs. ablation success and found that subjects <15kg still maintained very high success rates compared to the <30kg cohort, without any major or common adverse events. Interestingly, using cubic spline analysis, they found an inverse relationship between weight and ablation success and multivariable modeling with weight as a continuous variable still showed that increasing weight was a predictor of ablation failure.
This study provides interesting insights into the current state of pediatric WPW ablation. It is generally encouraging that overall ablation outcomes and overall incidence of adverse events including major complications remain very good. These same trends are reflected even in smaller sized patients. While the risk of serious complications is higher (though still quite low), acute success appeared better in patients <30kg compared to those >30kg. The authors provided insights into this finding, noting probable advantages with regards to catheter reach and tip stability together with proportionately larger ablation lesion relative to cardiac size and wall thickness as likely contributors. While ablative injury to coronary arterial branches and perforation risk during transseptal puncture are among the most feared complications with ablation in small patients, it was encouraging that neither were documented in the registry data for pediatric WPW. Interestingly, increasing weight was found to be a predictor of ablation failure in pediatric WPW. Larger chamber size and greater annular area to map, together with possible myocardial changes in older patients may contribute to lower acute success in heavier, and particularly obese, patients.
The general data set reflects the general trends in practice as far as the point at which patients are referred for ablation. Data was consistent with the general perspectives that those who are more symptomatic are more likely to undergo ablation earlier and asymptomatic WPW, frequently found in older patients, often presents to the lab for risk stratification purposes. The data also appears to reflect operator comfort levels and willingness to take patients to the lab, or possibly the confidence or reluctance of referring physicians to send patients for ablation. The overall low proportion of patients <30kg seems to reflect dominant practice patterns that seem to shy away from procedural intervention in smaller patients. The higher acute success rates, together with the finding of increasing weight being a contributor to lower ablation success across all pathway locations, may encourage some to consider earlier ablation referral.
The biggest limitation to this study relates to its design around the IMPACT registry data set. While the registry affords a large volume of case data to work with, finer details are lost, which typically can only be integrated in smaller scaled studies. This would include specific details regarding difference in vascular access number and sheath sizes, mode of mapping, integration of ICE, and other specific EP findings that may have influenced decisions to ablate and the degree of aggressiveness with ablation. Incomplete data entry could not be controlled for and data entry for patients who underwent EPS only vs. EPS + deferred ablation could not be clearly differentiated. Finally, while the study included data up through 2019, there has been a significant increase in newer technology with mapping systems and catheters, together with growing experience with irrigated RF catheters that likely impact ablation outcomes in the most current era.