3.1 Patients
A total of 280 patients were categorised into the CF group, and 294 into the ZF group. Of these, 170 were in the ZF adult subgroup and 124 in the ZF paediatric subgroup. The baseline characteristics are shown in Table 1. The CF and ZF groups differed in mean age (52.7 ± 16.5 years vs 30.9 ± 20.3 years, p < 0.001) and BMI (27.0 ± 5.4 kg/m2 vs 22.8 ± 5.7 kg/m2, p< 0.001). In the subgroup analysis, the differences of mean age and BMI were present only between the CF group and the ZF paediatric subgroup. There was only one patient younger than 5 years, aged 4 years at the time of the procedure. There were no patients with a body weight below 15 kg; the lightest patient weighed 18 kg. The CF and ZF groups differed in the type of tachycardia: the ZF group had a lower proportion of patients with AVNRT (53.1% vs 63.0%, p < 0.016) and a higher proportion of patients with AVRT (34.4% vs 23.8%, p = 0.006); these differences were present in the ZF paediatric subgroup but not in the ZF adult subgroup.
There were also fewer patients on AAD therapy in the ZF group at the time of the index procedure (20.7% vs 56.1%, p < 0.001). There were no crossovers in either of the groups.
3.2 Procedural data
There were significantly more cryoablation and significantly fewer RF ablation procedures in the ZF group (cryoablation: 44 vs 0; RF ablation: 250 vs 280, p < 0.001). When looking at RF ablation procedures, the median number of lesions (8 (4-17) vs 7 (4-13), p= 0.015) and ablation time were significantly higher in the ZF group (382 ± 379 s vs 233 ± 242 s, p < 0.001). These differences were present in the ZF adult subgroup and not in the ZF paediatric subgroup. Procedure time was shorter in the ZF group (94.2 ± 50.4 min vs 104.0 ± 54.0 min; p = 0.002). Differences of procedure time for different arrhythmias can be seen in Figure 1. This difference was present in both of the ZF subgroups. In the CF group, the average fluoroscopy time was 13.9 ± 11.0 minutes and the average dose area product (DAP) was 606 ± 1003 mGym2. There were no major complications in either group. One patient in the CF group who was treated for left atrial AT and had transseptal puncture developed pericardial effusion that resolved without an additional intervention. The two groups did not differ in overall procedural success rate (ZF vs CF; 92.5% vs 95.4%, p = 0.155). In Figure 2, the procedural success for each arrhythmia can be found. In the subgroup analysis, patients in the ZF adult subgroup who underwent RF ablation for AVNRT had a statistically lower success rate compared to the CF group (95.8% vs 99.4 %, p = 0.040). Detailed procedural information is available in the supplemental data in Table S1.