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).