Catheter ablation of atrial fibrillation: the need for studies to assess the efficacy and safety of novel anticoagulants

For selected patients with atrial fibrillation (AF), catheter ablation is an important treatment alternative and has about a 70 % success rate in carefully selected patients. Patients undergoing this procedure are at an increased risk of thromboembolic events during and following the ablation procedure. Bridging of anticoagulation, insertion of sheaths and catheters, left atrial endothelial damage, and atrial stunning may all lead to this increased thromboembolic risk. In order to minimize these thromboembolic events, anticoagulation, initiated as part of the procedure, increases bleeding complications including pericardial tamponade and vascular complications. Controlled data are not available to guide anticoagulation management of such patients during the peri-ablation period. Several years ago, we used to discontinue warfarin for several days before the procedure and the anticoagulation bridged with subcutaneous low molecular weight heparin (LMWH). The main limitation of this approach is that patients require LMWH after the procedure until the international normalized ratio (INR) becomes therapeutic. Excessive anticoagulation with LMWH and periods of subtherapeutic INR on warfarin post-procedure, have resulted in bleeding and thrombo-embolic complications [1]. More recently, in order to reduce these limitations, it has become more common to perform the ablation procedure without discontinuation of warfarin [2–4]. Several studies have demonstrated that uninterrupted warfarin is associated with fewer bleeding complications compared to LMWH bridging. With both approaches, unfractionated heparin is administered during the procedure and the dosing regimen is guided by a target activated clotting time (ACT) ranging from 225 to 450. Heparin infusion is discontinued once all catheters have been removed and the sheaths are removed once the ACT is less than 200 s. Post-procedure LMWH is usually not required since the patient is on a therapeutic level of anticoagulation with warfarin. Anticoagulation is then continued for 3–6 months or indefinitely depending on the patient’s risk factors. The problem with the above protocols is that there is no gold standard based on carefully collected prospective controlled data and the FDA has never approved LMWH bridging as an indication for this type of perioperative use. The commercial approval of dabigatran and rivaroxaban (and soon apixaban and edoxaban) has created a new anticoagulation challenge for AF patients undergoing catheter ablation procedures. Dabigatran has been commercially available for about 2 years and several reports have been published related to the safety and efficacy of using this drug during AF ablation procedures. Winkle et al. [5] demonstrated dabigatran to be safe and well tolerated when used after AF ablation (interrupted use prior to the ablation procedure) in a single-center study. The study included patients previously treated with warfarin, dabigatran, or aspirin. The post-procedure use of dabigatran was not associated with any major bleeding or thromboembolic events. However, three patients had to stop dabigatran due to dyspepsia, rash, and diarrhea. In this study, dabigatran was discontinued 36– 60 h prior to the procedure based on renal function and restarted 22 h after the procedure (post-procedure LMW heparin was given). The target ACT during the procedure was 225 s. A larger multicenter study by Lakkireddy et al. [6] reported that periprocedural dabigatran use significantly G. V. Naccarelli (*) :M. D. Gonzalez Electrophysiology Program, Heart and Vascular Institute, Penn State University College of Medicine, 500 University Drive, Room H1511, P. O. Box 850, MC H047, Hershey, PA 17033, USA e-mail: gnaccarelli@hmc.psu.edu