Background Patients with atrial fibrillation (AF) are at increased risk of thromboembolic events. Oral anticoagulation (OAC) reduces the risk of thromboembolic events, especially stroke. Whether restoration of sinus rhythm (SR) through direct current cardioversion (DCCV) favourably improves thrombotic profile and reduces stroke risk, is unknown.

Methods We enrolled 40 patients (73% men, 67 ± 13 yrs) with newly diagnosed non-valvular AF, on OAC and scheduled to undergo DCCV. Assessment of thrombotic status was performed before and 6 weeks after DCCV, using the Global Thrombosis Test. This automated, point-of-care test assesses both platelet reactivity and endogenous thrombolysis from a native, non-anticoagulated blood sample. The time taken to form an occlusive thrombus under high shear stress (occlusion time, OT), and the time required to restore flow by endogenous thrombolysis (lysis time, LT) are measured. We compared thrombotic profiles of patients who remained in SR at follow up (n = 20) to patients who had reverted to AF (n = 20).

Results Amongst the whole cohort (n = 40), there was no difference in OT or LT before and after DCCV. However, patients who reverted to AF demonstrated significant prolongation of LT after DCCV (1776 ± 382s vs. 2923 ± 1770s; p = 0.009), compared to no change in LT between pre- and post-DCCV in those who maintained SR (1691 ± 581s vs. 1480 ± 786s; p = 0.2). Between groups comparison showed significantly prolonged LT in those who reverted to AF compared to those who maintained SR after DCCV (2894 ± 1728s vs. 1407 ± 828s; P = 0.002). No change in OT was observed in between groups. There was no difference in baseline OT and baseline LT between those who stayed in SR and those who did not. The groups were well matched for variables, including age, sex, OACs, and CHA²DS²VASc score.

Conclusions Patients who revert to AF after DCCV have exhibit a more pro-thrombotic profile, with impaired endogenous fibrinolysis, than those who maintain SR, despite OAC. Whether more prolonged maintenance of SR improves thrombotic status, and reduces stroke risk, requires evaluation.