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Assessing Arrhythmia Burden After Catheter Ablation of Atrial Fibrillation Using an Implantable Loop Recorder: The ABACUS Study


  • [Correction added after online publication 2-May-2013: Author name has been corrected. Dr. Frankel should be identified as David S. Frankel, M.D.]

  • The study was supported by an unrestricted grant from Medtronic, Inc., who had no role in the administration of the study, in the interpretation of data and writing of the manuscript.

  • A.E.E., D.J.C., R.B., M.D.H., E.P.G., F.E.M., D.F., J.M.C., R.J.C., and S.D. received honoraria from Medtronic. A.E.E., E.P.G., F.E.M., and S.D. received research support from Medtronic. M.D.H. and F.E.M. served on advisory boards for Medtronic and D.J.C. received consulting fees. Other authors: No disclosures.

Address for correspondence: Sanjay Dixit, M.D., Hospital of the University of Pennsylvania, 9 Founders Pavilion, 3400 Spruce St., Philadelphia, PA 19104, USA. Fax: 215-615-4350; E-mail:

Assessing Arrhythmia Burden After Ablation


Arrhythmia monitoring in patients undergoing atrial fibrillation (AF) ablation is challenging. Transtelephonic monitors (TTMs) are cumbersome to use and provide limited temporal assessment. Implantable loop recorders (ILRs) may overcome these limitations. We sought to evaluate the utility of ILRs versus conventional monitoring (CM) in patients undergoing AF ablation.

Methods and Results

Forty-four patients undergoing AF ablation received ILRs and CM (30-day TTM at discharge and months 5 and 11 postablation). Over the initial 6 months, clinical decisions were made based on CM. Subjects were then randomized for the remaining 6 months to arrhythmia assessment and management by ILR versus CM. The primary endpoint was arrhythmia recurrence. The secondary endpoint was actionable clinical events (change of antiarrhythmic drugs [AADs], anticoagulation, non-AF arrhythmia events, etc.) due to either monitoring strategy.

Over the study period, 6 patients withdrew. In the first 6 months, AF recurred in 18 patients (7 noted by CM, 18 by ILR; P = 0.002). Five patients in the CM (28%) and 5 in the ILR arm (25%; P = NS) had AF recurrence during the latter 6 months. AF was falsely diagnosed frequently by ILR (730 of 1,421 episodes; 51%). In more patients in the ILR compared with the CM arm, rate control agents (60% vs 39%, P = 0.02) and AADs (71% vs 44%, P = 0.04) were discontinued.


In AF ablation patients, ILR can detect more arrhythmias than CM. However, false detection remains a challenge. With adequate oversight, ILRs may be useful in monitoring these patients after ablation.