Catheter ablation of left atrial arrhythmias on uninterrupted oral anticoagulation with vitamin K antagonists: What is the relationship between international normalized ratio, activated clotting time, and procedure‐related complications?

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Radiofrequency catheter ablation (RFA) is considered an effective treatment of drug‐refractory atrial fibrillation (AF). The risk of periprocedural thromboembolic events remains a concern, and anticoagulation during the procedure with a targeted activated clotting time (ACT) of >300 seconds is recommended.1
Anticoagulation protocols for vitamin K antagonists (VKA) differ. Some centers still discontinue VKA and use subcutaneous or intravenous heparin to bridge anticoagulation before and after the procedure.3 However, studies have shown that heparin or enoxaparin administration after VKA discontinuance increases the risk of bleeding and thromboembolic events.3 Uninterrupted oral anticoagulation during RFA is associated with a lower risk of bleeding and thromboembolic complications compared with a “bridging” strategy.6 Additionally, this approach decreases the amount of heparin required to achieve an ACT >300 seconds.9 Although guidelines recommend a target ACT of >300 seconds, different studies aim for ACT levels between 250–400 seconds and even below that. It should be noted that referenced studies aiming for an ACT >300 seconds are based on investigations mostly performed with closed tip catheters, with a significantly greater chance for “charring” and potential thrombus formation.10 A target ACT >300 seconds has been attributed to the decrease in the risk for thromboembolic complications, but studies have also showed that RFA can be performed safely with a target ACT of <300 seconds, especially in a setting where open irrigated tip catheters that require lower ACTs are used.6 Existing data show that ACTs lower than 250–300 seconds are not associated with a higher periprocedural rate on thromboembolic complications, but these studies compared patients on interrupted VKA.13 It is not known whether target ACT levels of 250–300 seconds with uninterrupted VKA are safe regarding thromboembolic and bleeding complications.
The purpose of this study was to assess the relationship among international normalized ratio (INR) level, baseline‐ACT, mean ACT, minimum ACT, maximum ACT, and heparin requirements. This study also aimed to evaluate the safety and efficacy of a target ACT of 250–300 seconds in regard to periprocedural complications in patients on uninterrupted VKA undergoing RFA procedures for AF and left atrial tachycardias.

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