Abstract:
Introduction : Radiofrequency ablation (RFA) slow pathway modification for catheter ablation of AV nodal reentrant tachycardia (AVNRT) is traditionally performed using a 4mm, non-irrigated (NI) RF ablation catheter. Slow pathway modification using irrigated, contact-force sensing (ICFS) RFA catheters has been described in case reports, but outcomes have not been systematically evaluated.
Methods : Acute procedural outcomes of 200 consecutive patients undergoing slow pathway modification for AVNRT were analyzed. An ICFS 3.5mm RFA catheter (ThermoCool SmartTouch STSF, Biosense Webster, Inc.) was utilized in 134 patients, and a 4mm NI RFA catheter (EZ Steer, Biosense Webster, Inc.) was utilized in 66 patients. Electroanatomic maps were retrospectively analyzed in a blinded fashion to determine proximity of ablation lesions to the His region.
Results : Baseline characteristics of patients in both groups were similar. Total RF time was significantly lower in the ICFS group compared to the NI group (5.53±4.6 vs. 6.24±4.9 min, p=0.03). Median procedure time was similar in both groups, ICFS 108.0 (87.5-131.5) vs. NI 100.0 (85.0-125.0) min, p=0.2). Ablation was required in closer proximity to the His region in the NI group compared to the ICFS group (14.4 ± 5.9 mm vs, 16.7 ± 6.4 mm, respectively, p=0.01). AVNRT was rendered non-inducible in all patients, and there was no arrhythmia recurrence during follow-up in both groups. Catheter ablation was complicated by AV block in one patient in the NI group.
Conclusion : Slow pathway modification for catheter ablation of AVNRT using an irrigated, contact-force sensing RFA catheter is feasible, safe, and may facilitate shorter duration ablation while avoiding ablation in close proximity to the His region.
Keywords: radiofrequency ablation, atrioventricular nodal reentrant tachycardia, irrigated catheter, slow pathway modification
Introduction :
Radiofrequency ablation (RFA) is a safe and effective treatment option for AV nodal reentrant tachycardia (AVNRT), and is most frequently performed using a 4mm, non-irrigated (NI) RF ablation catheter in a temperature-controlled mode, although use of irrigated RF ablation catheters is increasingly common. The location of RF application for slow pathway modification is selected to optimize efficacy while maintaining a safe distance to the presumed location of the compact AV node to minimize risk of creating AV block.1 Optimal energy delivery during RFA requires stable contact at the catheter-tissue interface. Utilization of irrigated, contact-force sensing (ICFS) catheters has increased over time for a range of indications.2-4 Availability of contact-force data during ablation may facilitate effective ablation, while ablation electrode irrigation may improve efficiency lesion creation, particularly when power during NI RF ablation is limited by temperature at the ablation electrode.
Although slow pathway modification using ICFS RFA catheters has been described in case reports, outcomes have not been systematically evaluated. The aim of this study is to compare acute outcomes of RF ablation for slow pathway modification using a 3.5mm ICFS RFA catheter to those using a NI 4mm RF ablation catheter.
Methods :
Retrospective chart review identified 200 consecutive patients who underwent slow pathway modification for AVNRT between March 2019 and June 2021. Patients were excluded from the study if they had prior ablation, were undergoing an additional ablation at time of AVNRT ablation or had unavailable mapping data. All available medical records, including baseline characteristics, ECG, and electrophysiology study were reviewed and analyzed by investigators. Data collection and analysis was performed according to protocols approved by the NYU Langone Health Institutional Review Board. Surface and intracardiac electrograms (EGMs) were digitally recorded and stored (EP Workmate, Abbott Medical, Inc.). All procedures were performed under conscious sedation and AVNRT diagnosis was confirmed using established criteria.5, 6 An ICFS 3.5mm RFA catheter (ThermoCool SmartTouch STSF, Biosense Webster, Inc.) was utilized in 134 patients, and a 4mm NI RFA catheter (EZ Steer, Biosense Webster, Inc.) was utilized in 66 patients. NI RFA was performed with an initial power setting of 50W in a temperature control mode and temperature limit 55°C and RF generator in “fast mode.” ICFS RFA was performed in a power control mode with an initial power setting of 35W and standard irrigation settings and RF generator in “STSF mode.” Power settings were not altered intraoperatively. Non-fluoroscopic 3-dimensional mapping was performed using the Carto 3 (Biosense-Webster, Inc.,) mapping system in all patients. Catheter ablation was considered acutely successful if AVNRT was rendered noninducible, and there was ≤ 1 inducible AV nodal reentrant echo beat with isoproterenol infusion up to 20mcg/min. Electroanatomic maps (EAM) were analyzed in a retrospective fashion by blinded investigators to determine the shortest distance between an EAM point with a His electrogram and the nearest ablation lesion (His distance) as a surrogate marker of ablation-related AV conduction injury risk (Figure 1). Intraprocedural data including radiofrequency (RF) time, case length, fluoroscopy time and details of electrophysiology study were collected and analyzed.
Patients were followed at least three months after the date of their procedure. Patients received routine outpatient follow-up at 1-month post-ablation and subsequently at the discretion of their referring cardiologist. The primary outcomes were survival free of recurrent AVNRT after slow pathway modification, and occurrence of major complications including ablation related AV block. Secondary outcomes were procedure duration, RF time, and shortest distance between the electroanatomic mapping point with a His electrogram and the nearest ablation lesion.
Categorical data were analyzed across the 2 groups with the chi squared test and were reported as frequencies and percentages. Continuous data were analyzed using the Mann-Whitney U test and were reported as mean+ standard deviation. SPSS Statistics software 25.0 (IBM, Armonk, NY) was used for data analysis.
Results :
The baseline clinical characteristics of the 134 patients who underwent NI RFA and 66 patients who underwent ICFS RFA were similar (Table 1). Baseline electrophysiologic features of patients in both groups were similar apart from obstructive sleep apnea (OSA) (Table 2). A steerable sheath was used more frequently in patients who underwent ICFS catheter ablation compared to patients who underwent ablation with a NI catheter (88% vs. 51%, respectively, P<0.001). Six patients underwent transseptal puncture in the ICFS group, as compared to two in the NI groups. Total RF time was significantly lower in the ICFS group compared to the NI group (5.5±4.6 vs. 6.2±4.9 min, p=0.03). Median procedure time was similar in both groups, ICFS 108 (88-132) min vs. NI 100 (85 -125) min, p=0.2). Ablation was required in closer proximity to the His region in the NI group compared to the ICFS group (14 ± 6 mm vs, 17 ± 6 mm, respectively, p=0.01). The proportion of cases in which ablation was required within 1 cm of a location with a His electrogram was significantly greater in the NI catheter group as compared to the ICFS group (20% vs. 9%, respectively, p=0.04, Figure 2). AVNRT was successfully rendered uninducible in all patients.
After ablation, patients had at-least one post-procedure outpatient evaluation. There were no recurrent arrhythmias noted during the follow-up period (Table 3). One patient in the NI ablation group developed persistent AV block with a His distance of 17 mm, while there were no cases of persistent AV block in the ICFS ablation group. There were no vascular access complications, including AV fistula or hematoma, in either cohort.