Factors associated with delayed treatment initiation of oral anticoagulants among Medicare patients with atrial fibrillation
Authors: Luo X , Chaves J , Wang A , Steffen D R , Dhamane A D , Dai F 
Published: November 2023

Abstract

Background
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the United States (US) and is associated with increased risk of stroke.1 Oral anticoagulants (OACs) are the primary treatment to reduce stroke risk in patients with AF.2,3 However, there is recent evidence of underuse of OAC in AF patients.4

Purpose
To identify factors associated with delayed OAC treatment initiation among AF patients in the US clinical practice.

Methods
Medicare beneficiaries aged ≥65 years with a new diagnosis of AF without moderate-to-severe mitral stenosis or a mechanical heart valve after 1 Oct 2015 were included. Additional inclusion criteria included ≥1 claim for an OAC on or after 1st diagnosis of AF, ≥12 months of continuous Medicare Parts A, and D enrollment, and CHA2DS2-VASc score of ≥2 for males/≥3 for females. Time from 1st AF diagnosis to OAC initiation (index OAC), and demographic, sociodemographic, clinical and index OAC formulary characteristics were described. Delayed initiation was defined as OAC initiation &gt;3 months after and early initiation as OAC initiation 0-3 months after 1st AF diagnosis. Factors associated with delayed OAC initiation were assessed using multivariable logistic regressions.

Results
A total of 446,441 patients met the inclusion criteria. Time from 1st AF diagnosis to OAC initiation was &lt;1 month for 52.4% of patients, 1–≤3 months for 18.1%, &gt;3–≤6 months for 7.1%, &gt;6–≤12 months for 6.8%, and &gt;12 months for 15.7%. Accordingly, 30% had delayed vs. 70% had early OAC initiation.
Median age was 78 years (both), 48% and 47% were male, 87% and 89% were White, and median CHA2DS2-VASc score was 4 (both), respectively, for the delayed and early OAC initiation cohorts (Table 1).
Factors associated with delayed OAC initiation included Black race (odds ratio [OR]: 1.29, 95% confidence interval [CI]: 1.25–1.33), South and West US census regions (OR: 1.22, 95%CI: 1.19–1.24 and OR: 1.29, 95%CI: 1.26–1.32, respectively), dementia (OR: 1.27, 95%CI: 1.23–1.30), congestive heart failure (OR: 1.20, 95%CI: 1.26–1.32), bleeding hospitalization ≤3 months before 1st AF diagnosis (OR: 1.22, 95%CI: 1.18–1.27), prior authorization (OR: 1.69, 95%CI: 1.66–1.71), and tier 4 formulary for index OAC at AF diagnosis (OR: 1.26, 95%CI: 1.22–1.30). Additionally, having low-income subsidy or dual eligibility (for Medicare and Medicaid) was associated with increased odds of delayed OAC initiation (OR: 1.06, 95%CI: 1.02–1.10 and OR: 1.09, 95%CI: 1.05–1.14, respectively; Figure 1).

Conclusions
In this study on Medicare patients with AF, Black race, low-income subsidy, and dual eligibility were found to be associated with delayed OAC initiation, suggesting potential disparities in the care of AF with timely OAC treatment. Moreover, OAC requiring prior authorization (the strongest predictor) or being on formulary tier 4 were associated with delayed initiation, indicating formulary restrictions may create barriers to timely OAC access for AF patients.Table 1.Patient characteristicsFigure 1.Factors of delayed initiation