Hansen, RyanKatta, Arvind2023-08-142023-08-142023-08-142023Katta_washington_0250O_25633.pdfhttp://hdl.handle.net/1773/50168Thesis (Master's)--University of Washington, 2023Background and ObjectiveDirect oral anticoagulants (DOACs) have vastly improved care for atrial fibrillation (AF) as well as prevention of strokes and heart attacks. Although clinical trials and observational studies have confirmed superior safety and reduced bleeding rates for DOACs compared to warfarin, the risk of bleeding though relatively small is not zero. Little is known about the drug-utilization patterns of patients after a major bleed on a DOAC. The aim of this study was to characterize the real-world treatment patterns and evaluate risk of change of treatment of AF patients after experiencing a major bleed on a DOAC. MethodsThis study was a retrospective cohort analysis conducted using the Marketscan Research Databases between October 1, 2015 and December 31, 2021. Patients were  18 years old and initiated a DOAC after AF diagnosis. Patients with a hospitalization for a major bleed were matched to patients that did not bleed through the follow-up period. Patients were followed until 12 months after index, 1st disenrollment, or 2nd hospitalization for a major bleed. Outcomes included discontinuation, treatment switching, dose change, and reinitiating the same DOAC after discontinuation. Time-to-event analyses were conducted using Cox proportional hazards regression to calculate risk of experiencing outcomes. ResultsThe most common first outcome after a major bleed in the bleed group (n = 2,087) was discontinuation (54.8%) followed by no change in therapy (34.7%). Of patients who discontinued after a major bleed, 16.5% of patients reinitiated. The bleed group had a 3.84-fold increased risk (95% CI: 3.56 to 4.14, p < 0.0001) of change to treatment compared to the control group (n = 6,261). Among the bleed group, patients with prior warfarin use had a 2.93-fold increased risk (95% CI: 1.83 to 4.68, p < 0.0001) of switching and trended toward a decreased risk of discontinuation (HR: 0.87, 95% CI: 0.73 to 1.03, p = 0.11) compared to those without prior warfarin use. Among the bleed group, those with high stroke risk had 29% reduced risk (95% CI: 0.55 to 0.92, p = 0.01) of discontinuation compared to those with low stroke risk. ConclusionsOur study found AF patients to have significantly increased risk of DOAC discontinuation, switching, or dose changes after being hospitalized for a major bleed. Future studies focusing on DOACs may increase prescriber confidence in restarting anticoagulation after a major bleed.application/pdfen-USnoneAtrial FibrillationBleedingTreatment PatternEpidemiologyMedicinePharmaceutical sciencesThesis