The advantages and disadvantages of the novel fourth-generation cryoballoon as compared to the second-generation cryoballoon in the current short freeze strategy

Background The novel fourth-generation cryoballoon (4 th -CB) is characterized by a shorter-tip that potentially facilitates better time-to-isolation (TTI) monitoring. We sought to clarify the advantages and disadvantages of the 4 th -CB compared to the second-generation cryoballoon (2 nd -CB) in pulmonary vein isolation (PVI). Methods Forty-one and 49 consecutive atrial fibrillation patients underwent 2 nd -CB and 4th-CB PVIs using 28-mm balloons and short freeze strategies. When effective freezing was not obtained, the CB was switched to the other CB. Results The rate of successful PVIs was significantly higher for 2 nd -CBs than 4 th -CBs (162/162[100%] vs. 178/193[92.2%] PVs, p < 0.0001). The difference was significant for lower PVs, especially right inferior PVs (RIPVs)( p = 0.005). In a total of 15 PVs in 11 patients, 4 th -CBs were switched to 2 nd -CBs, and 14/15(93.3%) PVs were successfully isolated. The balloon temperature tended to reach -55℃ more frequently with 2 nd -CBs than 4 th -CBs during RIPV ablations (15/41[36.6%] vs. 12/49[24.5%], p = 0.21). The TTI monitoring capability was significantly higher with 4 th -CBs than 2 nd -CBs (131/188[69.7%] vs. 83/160[51.9%] PVs, p = 0.0007). The difference was significant for right superior and left inferior PVs, but not for left superior PVs. Even if PVs requiring crossover were excluded, the total freeze duration (715±152 vs. 755±215 seconds, p = 0.31) tended to be shorter for 2 nd -CBs than 4 th -CBs. The incidence of phrenic nerve injury was similar for 2 nd -CB and 4th-CB ablation (0/41 vs. 2/49, p = 0.12) Conclusions The 4 th -CB’s shorter balloon tip enabled a significantly higher capability of TTI monitoring; however, it resulted in significantly lower rates of successful PVIs than the 2 nd -CB, especially for the RIPVs.