Background: Direct oral anticoagulants (DOACs) are first line therapy in venous thromboembolism (VTE), and non-valvular atrial fibrillation. Gastrointestinal (GI) surgeries involving removal or rearrangement of the proximal GI tract may alter DOAC absorption, and thereby its anticoagulant effect, but data is lacking.
METHODS AND RESULTS: We conducted a retrospective single center cohort study comparing peak plasma anti-Xa DOAC levels (PPDL) in those post-GI surgeries with removal or rearrangement of the proximal GI tract, to expected levels from pharmacokinetic studies, and calculated their rates of VTE, arterial thrombosis (AT), major bleeding (MB) and all-cause mortality. PPDLs were measured using anti-Xa assays calibrated to the respective DOAC. Our cohort consisted of 61 patients with a mean age of 58.7 years, of which 63.9% were female and 57.3% had cancer. The median PPDLs on therapeutic Apixaban (n=38) and Rivaroxaban (n=17) were 139 (interquartile range (IQR) 102.5 to 188.5) ng/mL and 261.5 (IQR 160 to 340.75) ng/mL, respectively. In total, 71.2% of PPDLs were in the expected range, including 85.0% on Apixaban and 45.5% on Rivaroxaban. The total rate of recurrent VTE, AT, MB and all-cause mortality were 2.72 (95% confidence interval (CI) 1.10 to 5.66), 1.36 (95% CI 0.35 to 3.70), 1.81 (95% CI 0.58 to 4.37) and 3.63 (95% CI 1.68 to 6.89), respectively per 100-person years.
Conclusion: After proximal GI surgery, 71.2% of PPDLs were in the expected range on therapeutic anti-Xa DOACs, with Apixaban twice as often in range compared to Rivaroxaban. Rates of VTE, AT and MB were low.
