Safety and efficacy of superior vena cava isolation using the second-generation cryoballoon ablation in a canine...

The safety and efficacy of superior vena cava (SVC) isolation (SVCI) using second-generation cryoballoon (CB) ablation remains unknown.

Electrical isolation of SVC was attempted using the second-generation CB ablation catheter in 14 canines. Ablation duration was randomized to either 90 s (7 canines) or 120 s (7 canines). SVC venography was performed to identify the SVC-right atrium (RA) junction. The 28-mm CB was positioned above SVC-RA junction. Repeat electrophysiological assessment in the live animals was conducted 40-60 days post-ablation, after which animals were euthanized for histological examination.

Acute SVCI was successfully performed in all canines. No significant differences in numbers of freezes (1.7 ± 0.8 vs. 1.5 ± 0.5, p = 0.658), time to isolation (TTI) (24.3 ± 8.1s vs. 22.7 ± 9.0s, p = 0.297), temperature at isolation (-23.4 ± 12.5 °C vs. -21.5 ± 11.1 °C, p = 0.370), and nadir temperature (-51.2 ± 6.2 °C vs. -53.3 ± 7.0 °C, p = 0.195) were observed between the 90-s and 120-s groups. There were no procedural complications except one transient sinus bradycardia in the 120-s group. After ablation, animals survived for 51 ± 5 days. Chronic SVCI was achieved in 6 of 7 (85.7%) SVCs in the 90-s group and 7 of 7 SVCs (100%) in the 120-s group (p = 0.299). Histological analysis revealed that a circumferential transmural lesion was achieved in all isolated SVCs. No sinus node (SN) and phrenic nerve injuries were observed. The minimum distance between ablation lesion and SN was 5.1 ± 3.0 mm.

The second-generation CB ablation catheter is both safe and effective in achieving SVC isolation in a canine model. Effective SVCI was found in the 90-s dosing strategy.