Results
Baseline characteristics
A total of 136 patients were included in the study and 68 patients were each allocated in the ME group and the control group. According to SVT diagnosis, there were 76 patients with AVNRT (38 in the ME group and 38 in the control group) and 60 patients with AVRT/WPW syndrome (30 in the ME group and 30 in the control group). The mean age was 51.2 (±16.7) years and 76 (55.9%) patients were male (Table 1). There was no significant difference in demographic characteristics or underlying comorbidities between the ME group and the control group.
Procedure outcomes in the entire population
Ablation procedures were successfully conducted in all patients with no intraprocedural complication. There was no crossover in ablation catheters during the procedures. RF attempt number to achieve the prespecified ablation endpoints was significantly lower in the ME group compared to the control group (2 [1–4] vs. 3 [2–7] in the ME group and the control group, respectively, p=0.032). RFA time to the ablation endpoints was also significantly shorter in the ME group (23.5 [5.0–111.5] vs. 64.5 [16.0–185.0] seconds in the ME group and the control group, respectively, p=0.013) (Table 2). During the entire procedure, total ablation time and procedure time were similar between the two groups. Average RF power was higher in the ME group (34.0 [31.0–38.0]W vs. 32.0 [28.0–33.5]W, p<0.001) and average temperature was lower in the ME group (41.0 [34.0–42.0]°C vs. 49.0 (46.0–51.5)°C, p<0.001). There was no significant difference in the acute SVT reinduction rate between the two groups (5.9% vs. 5.9%). The procedure endpoint (≤1 echo beat or an absence of AP conduction) was achieved by repeated ablation in all patients with SVT reinduction.
Outcomes in AVNRT
SP ablation was performed in 76 patients with AVNRT. Eight patients had atypical AVNRT without significant difference between the two groups (Table 3). Median RF attempt number to the emergence of junctional rhythm was 2 (1–4) in the ME group and 2 (2–4) in the control group (p=0.113) (Table 3). Median ablation time to the emergence of junctional rhythm was 16 (5–80) seconds in the ME group and 48 (16–144) seconds in the control group (p=0.043). There was no significant difference in total ablation time, procedure time, or acute AVNRT reinduction rates between the two groups. Discrete SP electrograms were observed via ablation catheter in 14/38 (36.8%) patients in the ME group and 6/38 (15.7%) patients in the control group (Figure 2A). There was no transient or persistent atrioventricular block after ablation in all subjects.
Outcomes in AVRT/WPW syndrome
AP ablation was performed in 60 patients with AVRT/WPW syndrome. Manifest AP was shown in 18 patients without significant difference between the two groups (Table 4). Median RF attempt number to AP block was 2.5 (1–5) in the ME group and 4 (2–9) in the control group (p=0.128). Median ablation time to AP block was 29 (3–123) seconds in the ME group and 82.5 (16–214) seconds in the control group (p=0.110) (Table 4). There was no significant difference in total ablation time or procedure time. SVT reinduction was not observed in all patients, and acute AP reconnection rate (23.3% vs. 20.0% in the ME group and the control group, respectively, p=1.000) and dormant AP conduction rate (10.0% vs. 6.7%, p=1.000) were not significantly different between the two groups. Discrete AP electrograms were observed via ablation catheter in 13/30 (43.3%) patients in the ME group and 7/30 (23.3%) patients in the control group (Figure 2B, 2C, 2D).