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Long time‐to‐isolation during fourth‐generation cryoballoon ablation of the right superior pulmonary vein. What should we do next?

A 65-year-old man without any structural heart disease was admitted to our hospital for catheter ablation of symptomatic paroxysmal atrial fibrillation (AF). The starting rhythm was AF, and he underwent pulmonary vein (PV) isolation with a 28-mm fourth-generation cryoballoon (Artic Front Advance PRO, Medtronic, Inc., Minneapolis, MN, USA). In order to avoid right phrenic nerve injury, diaphragmatic electromyography was monitored during the cryoballoon (CB) applications. Following the confirmation of complete sealing of the PV with a 28-mm CB using a contrast medium injection, a single freeze was applied for the right superior PV (RSPV) as the first target vein. The Achieve mapping catheter (Achieve, Medtronic) was pulled back just behind the cryoballoon to monitor the real-time PV potentials. The cycle length of the recorded potentials on the Achieve mapping catheter gradually prolonged during the freezing and disappeared 130 s after the start of the application (Figure1A,B). Thenadir balloon temperature of the application was −53◦C (−32◦C at 30 s and −44◦C at 60 s from the start of the application), and a single 180s freeze was applied. The time-to-isolation (TTI) was long and what should we do next?