More prolonged ACT with dabigatran
In the present study, we demonstrated that dabigatran prolonged the ACT more than the other DOACs in a setting of a single skip. The possible mechanisms may include (1) dabigatran’s more pronounced ability to prolong the ACT, (2) it’s greater residual anticoagulant activity, or (3) its tighter positive interaction on the ACT with heparin. Let us discuss each possibility. First, all 4 currently available DOACs have been reported to prolong the ACT [10]. The extent to which a DOAC prolongs the ACT at a certain blood level varies depending on the DOAC. A study [19] reported that dabigatran and rivaroxaban prolonged the ACT in a concentration dependent manner while apixaban necessarily did not. Another extensive study [20] demonstrated that the ACT was longer in the uninterrupted dabigatran arm than in the uninterrupted apixaban and rivaroxaban arms, and a significant positive correlation between the ACT and drug concentration was noted only in the dabigatran arm. These findings may support the first possible mechanism. Second, all 4 DOACs have comparable half-lives [10]. Nevertheless, there are 2 different dosing regimens; edoxaban and rivaroxaban are supposed to be taken once daily while apixaban and dabigatran are given twice a day. In our series, patients with edoxaban and rivaroxaban had regularly taken them in the morning rather than evening according to the Japanese custom. Because of the single skip approach in our series, therefore, their last dose was about 24 hours before the ablation. On the contrary, patients with apixaban and dabigatran took their last dose half a day before the procedure. Accordingly, the blood level of apixaban and dabigatran must have been higher than that of edoxaban and rivaroxaban. The second proposed mechanism may thus be possible. Third, we previously proved in a review article [21] that dabigatran prolongs the ACT in synchronization with heparin. The aforementioned study [20] further showed that the positive interaction on the ACT with heparin was greater with dabigatran than apixaban and rivaroxaban. Therefore, the third mechanism may also be likely.