Cryoablation Procedure
Anticoagulation was continued uninterrupted for all patients. Procedures were performed under conscious sedation or general anaesthesia. Single transeptal puncture was performed. Ablation was performed using 28mm Arctic Front Advance Cryoballoon System (Medtronic) via a 14F FlexCath Cryosheath (Medtronic, Ireland). Each PV was engaged with a multi-polar catheter (Achieve wire, Medtronic) and with demonstration of PV electrograms where possible. After inflation, pulmonary venous occlusion was confirmed with venography, and freezes between 180-240 seconds applied to each vein, aiming for abolition of PV signals and freeze temperatures between -40°C to -55°C. Freezes for the right PVs were performed with simultaneous phrenic nerve stimulation from high output pacing via a Quad catheter positioned in the right subclavian vein. A single good freeze was considered sufficient if it isolated a pulmonary vein, but further freezes were deployed if a vein failed to isolate, or at operator discretion if the freeze was deemed poor. Patients remaining in AF at procedure end were electrically cardioverted to sinus rhythm. In the case of documented CTI dependant atrial flutter, CTI ablation was also performed using an irrigated RF catheter (without a 3D mapping system or contact force sensing technology).