Does the type of oral anticoagulant affect heparin dosing during catheter ablation?

Introduction

Catheter ablation is an effective and commonly used method for treating AF. To minimize the risk of thromboembolic complications, it is recommended that patients continue their established oral anticoagulant therapy with either a vitamin K antagonist (warfarin) or novel oral anticoagulants (NOACs). During the ablation, systemic anticoagulation with heparin is indicated to maintain activated clotting time (ACT) at values > 300 s, according to guidelines.

Earlier analyses suggested that the heparin dose required to achieve the desired ACT might differ depending on whether patients are on NOACs or warfarin. The RE-CIRCUIT study demonstrated that patients treated with the NOAC dabigatran had a lower risk of bleeding complications associated with catheter ablation compared to those on warfarin. A post hoc analysis of this study, summarized below, assessed whether the total dose of heparin administered during ablation differed between these two groups.

The RE-CIRCUIT Study

Methodology and Course

RE-CIRCUIT was a multicenter, prospective, randomized open study with blinded independent observers. It involved 635 patients indicated for catheter ablation for paroxysmal or persistent AF. Patients were randomized to treatment with dabigatran (DBG) at a dose of 150 mg twice daily or warfarin (W) dosed based on individual INR values. The ablation was performed without interrupting oral anticoagulant therapy, which continued for at least 2 months post-procedure. The first bolus of unfractionated heparin, calculated based on patient weight, was administered after the femoral sheath insertion before or immediately after transseptal puncture. Throughout the catheter's placement in the left atrium, heparin was dosed to maintain ACT above 300 s. ACT was measured 15 minutes after the first bolus dose and subsequently every 20 minutes.

Results

Researchers obtained data from 396 participants, with 191 on DBG and 205 on W. The average heparin dose administered during ablation did not significantly differ between the DBG and W groups: 12,402 IU (standard deviation [SD] 10,721) versus 11,910 IU (SD 8359). The average ACT was also comparable (330 s [DBG] vs. 342 s [W]), as was the proportion of patients maintaining an ACT over 300 s during ablation (31.9% [DBG] vs. 30.2% [W]).

The time interval between the last oral anticoagulant dose and transseptal puncture was most commonly 0 to < 4 hours for patients on DBG and 16 to < 24 hours for those on W. A lower heparin dose was needed to reach ACT > 300 s if the last DBG dose was given 0 to < 4 hours before transseptal puncture.

Conclusion and Discussion

The analysis results indicate that patients treated with dabigatran required a comparable amount of heparin to achieve ACT > 300 s as those on warfarin. These findings contrast with the earlier VENTURE-AF study, which showed a higher heparin consumption in patients on NOACs. The difference may be due to the distinct mechanisms of action of the tested medications. Dabigatran, as a direct thrombin inhibitor, modifies both ACT and activated partial thromboplastin time (aPTT), while the factor Xa inhibitor rivaroxaban, tested in VENTURE-AF, does not influence ACT or aPTT. This could explain the higher heparin requirement to achieve the desired ACT when using rivaroxaban compared to dabigatran.

The analysis further showed that the longer the time elapsed since the last dabigatran dose before transseptal puncture, the higher the heparin dose required to achieve ACT > 300 s. The small proportion of patients maintaining ACT above 300 s might indicate a conservative approach by physicians in administering heparin without interrupting oral anticoagulant therapy.

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Source: Calkins H., Willems C., Verma A. et al. Heparin dosing in uninterrupted anticoagulation with dabigatran vs. warfarin in atrial fibrillation ablation: RE-CIRCUIT study. Europace 2019; 21 (6): 879–885, doi: 10.1093/europace/euz057.