Switching from vitamin K antagonists to direct oral anticoagulants in non‐valvular atrial fibrillation patients: Does low time in therapeutic range affect persistence?

BACKGROUND: Non-valvular atrial fibrillation (NVAF) patients are advised to switch from a vitamin K antagonist (VKA) to direct oral anticoagulant (DOAC) when time in therapeutic range (TTR) is low. OBJECTIVE: To examine if pre-switch TTR determines persistence patterns in NVAF patients who are switched from a VKA to DOAC. PATIENTS/METHODS: Adult NVAF patients from three Dutch anticoagulation clinics who were newly switched from a VKA to DOAC between July 1, 2013 and September 30, 2018 were stratified by pre-switch TTR levels. DOAC prescription records were examined to determine persistence patterns according to a 100-day prescription gap. Cumulative incidences of non-persistence to DOAC were estimated using the cumulative incidence competing risk method. The association of pre-switch TTR levels with DOAC non-persistence was evaluated by Cox regression models. RESULTS: A total of 3696 NVAF patients were included, of whom 690 (18.7%) had a pre-switch TTR ≤ 45%. After switching from VKA to DOAC, 14.0% (95% confidence interval [CI] 11.3-17.0%) of the patients with a pre-switch TTR ≤ 45% became non-persistent to DOAC within 1 year, while 9.8% (95% CI 8.7-11.0%) did in those with a pre-switch TTR > 45%. In a multivariable model, a pre-switch TTR ≤ 45% was associated with a higher risk of non-persistence to DOAC (adjusted hazard ratio 1.55, 95% CI 1.22-1.97). Results were similar when using other cut-off points (60% or 70%) to define a low TTR. CONCLUSION: NVAF patients switching from VKA to DOAC due to a low pre-switch TTR saw a worse persistence pattern to DOAC after the switch compared to patients with a high pre-switch TTR.