Percutaneous pulmonary vein cryoablation to treat atrial fibrillation

Background: Cryothermic tissue injury, unlike hyperthermic tissue injury, preserves tissue architecture and causes less thrombus formation, and thus may prevent venous stenosis and stroke in ablating pulmonary veins (PVs) to treat patients with atrial fibrillation (AF). We investigate the feasibility, efficacy, safety and clinical outcome of using percutaneous cryoablation to treat such patients. Methods: Thirty-one patients who had drug refractory paroxysmal (20) or persistent (11) AF underwent 37 PV ablative procedures using a 4 mm- or 6 mm- tipped 7F cryoablation catheter (CryoCath Technologies Inc., Quebec, Canada). Segmental isolation at the veno- atrial junction was guided by a distal circumferential mapping catheter. Results: A total of 47 PV were ablated, of which 35/47 (74%) were electrically isolated and the remaining 12/47 had attenuation of PV electrograms, altered activation sequence, and marked slowing of left atrial-PV conduction. There was no change in PV diameter, either immediately following cryoablation (21+/-5 versus 22+/-6, p=0.69), or at 18+/-9 months follow-up (22+/-5 versus 22+/-5 mm, p=0.23). There was no clinical thromboembolic event. The duration of cryoablation for each treated PV and procedural duration was 65+/-39 and 290+/-101 min, respectively. Following cryoablation, 5/30 (6%) were free from AF and 12/30 (43%) showed improvement from previously ineffective antiarrhythmic drug therapy. 13/30 (43%) patients were unchanged by cryoablation. Conclusions: Cryothermic ablation shows great promise in reducing the risks of PV stenosis and thrombo-embolism associated with PV isolative procedures. However, cryoablation of these veins with linear catheters is time consuming, and the clinical outcomes are disappointing. Alternative catheter designs are required to overcome these difficulties.