Relationship between electronically monitored adherence to direct oral anticoagulants and ischemic or hemorrhagic events after an initial ischemic stroke—A case control study
Authors: Rekk Katharina , Arnet Isabelle , Dietrich Fine , Polymeris Alexandros A. , Lyrer Philippe A. , Engelter Stefan T. , Schaedelin Sabine , Allemann Samuel S. 
Published: April 2024

Background
Patients with atrial fibrillation (AF) have a high risk for recurrent clinical events after an ischemic stroke. Direct oral anticoagulants (DOAC) are prescribed for secondary prevention. Adherence to DOAC is crucial mainly because of their short elimination half-life. Non-adherence to DOAC can negatively impact patients’ outcomes. The relationship between (non-)adherence and recurrent clinical events is unknown in AF patients after initial stroke. We investigated adherence to DOAC in stroke survivors with AF who were included in the MAAESTRO study at the University Hospital Basel, Switzerland, between 2008 and 2022.

Methods
This study is a secondary analysis of data from MAAESTRO with a matched nested case-control design and 1:2 ratio. DOAC intake was measured with a small electronic device (Time4MedTM). We defined two arbitrary intervals of 17 days and 95 days as the longest time spans with electronic monitoring data per patient to maximize the number of participants with adequate amount of observation time available for analysis. Taking and timing adherence were calculated retrospectively i.e., prior to the recurrent event for cases. Trendline analysis of adherence over 95 days was calculated. Linear regression analysis was performed after adjusting for the co-variables age and daily pill burden. Sensitivity analysis was performed with controls for intervals in the reverse direction (prospectively).

Results
We analyzed 11 cases and 22 matched controls (mean age: 75.9 ± 9.2 years vs. 73.1 ± 8.4 years; n.s.) with similar stroke characteristics (NIHSS, mRS, MoCA) and 36.4% women in each group. Mean adherence values were high and similar between cases and controls (95 days taking: 87.0 ± 18.9% (cases) vs. 90.8 ± 9.8% (controls), n.s.; similar values for timing adherence). Six hemorrhagic and five ischemic events had occurred. Compared to controls, a significantly higher 95 days taking adherence was observed for hemorrhagic events (96.0 ± 5.0% (cases) vs. 88.1 ± 11.5% (controls); p<0.01) and a significantly lower 95 days taking adherence was observed for ischemic events (75.7 ± 24.8% (cases) vs. 94.2 ± 6.2% (controls), p = 0.024). Values for timing adherence were similar. A non-significant downward linear trend of adherence was observed over 95 days independently of the clinical events. The sensitivity analysis showed that the direction of the interval had negligible impact on the 95 days adherence.

Conclusion
Because recurrent ischemic events after an AF-related stroke were associated with low adherence to DOAC <76%, adherence enhancing interventions seem crucial in anticoagulated AF-patients. However, AF-patients with high adherence might benefit from a regular re-assessment of the bleeding risk as hemorrhagic complications were associated with adherence to DOAC >96%.

Trial registration
ClinicalTrials.gov NCT03344146.