AUSTIN, TEXAS. Catheter ablation for atrial fibrillation (AF) is associated with an approximately 1% risk of procedure-related ischemic stroke. The risk arises from the formation of blood clots (thrombi) on catheters and sheaths as well as from the stagnation of blood in the left atrial appendage. It is also possible that char formed on catheters due to overheating may be dislodged and carried to the small arteries in the brain where they, like the above-mentioned thrombi, may cause a stroke.

In order to prevent a procedure-related stroke, prospective ablation patients are placed on warfarin (INR 2.0-3.0) for two months prior to the procedure. Warfarin is usually discontinued a day or two before the ablation and replaced with heparin, which is also infused during the procedure. After a couple of days "bridging" with heparin, warfarin therapy is reintroduced and the patients are maintained on this for 3 to 6 months post-procedure.

A group of electrophysiologists headed by Dr. Andrea Natale now report that discontinuing warfarin immediately before and during the ablation procedure may be a bad idea. Their meta-analysis included 9 studies which compared the standard anticoagulation protocol (DW) in which warfarin is discontinued a day or two prior to the ablation and replaced by heparin which is also infused during the procedure and for a couple of days following with a new protocol (CW) where warfarin therapy (INR between 2.0 and 3.5) is maintained without interruption from 2 months before the procedure to 2 or 3 months after. The patients in both the DW group (21,002 patients) and the CW group (6400 patients) underwent pulmonary vein isolation with additional lesions as required. Intravenous unfractionated heparin was administered to all patients, although with different doses and at different stage of the procedure. Irrigated ablation catheters were used in all but two of the studies, and navigation guidance with an ICE (intracardiac echocardiography) catheter was used in 5 studies.

Overall, procedure-related death was 0.09%. The incidence of procedure-related thromboembolic events (ischemic stroke and TIA) was 16 times higher in the DW group (0.94%) than in the CW group (0.06%). A total of 4 strokes occurred in the CW group. One of these occurred in a patient who had only been on warfarin for 3 days prior to the procedure, while another occurred in a patient whose INR was below 1.8.

Major bleeding requiring medical intervention or blood transfusion occurred among 1.25% of patients in the DW group vs. 0.55% in the CW group. The majority of major bleeding complications was due to cardiac tamponade (fluid build-up in the sac enclosing the heart caused by puncture of the heart wall) which occurred in 0.29% of patients in the CW group and in 1.10% in the DW group. Minor bleeding complications occurred in 4.5% of patients in the CW group and in 18.6% of those in the DW group. This increase in minor bleeding was strongly associated with the use of low-molecular-weight heparin in pre-procedural bridging. A combination of CW and the use of ICE guidance was highly successful in reducing major bleeding complications.

The researchers conclude that continuous warfarin treatment (CW protocol), especially if used in conjunction with ICE imaging, materially reduces stroke/TIA risk and risk of bleeding when compared to the current standard DW protocol, which discontinues warfarin immediately before, during, and immediately following the ablation procedure. They do point out though that the studies involved procedures carried out in highly experienced AF ablation centers. They finish off with the following comment – whether the benefit and safety of CW also extend to low-volume centers merits further investigation.
Santangeli, P, Natale, A, et al. Ablation of atrial fibrillation under therapeutic warfarin reduces periprocedural complications. Circulation: Arrhythmia and Electrophysiology, Vol. 5, 2012, pp. 302-11

Editor's comment: This highly encouraging study provides convincing evidence that the risk of bleeding complications and stroke/TIA can be very significantly reduced by replacing the current DW protocol involving discontinuation of warfarin with the new CW protocol based on continuous warfarin therapy. However, whether the success of the CW protocol can be reproduced by less experienced EPs remains, at least in my mind, a question. Dr. Natale and colleagues not only have an outstanding success rate, but also an equally remarkable safety record. I would think this plays a large part in the success of the CW approach, which was primarily used by Dr. Natale and colleagues.