Use of Oral Anticoagulant Therapy for Veterans with Atrial Fibrillation Declines over 10-Year Period in VA Healthcare
In the more than two million Americans with atrial fibrillation (AF), oral anticoagulants (OACs) — either warfarin or one of several non-vitamin K antagonist oral anticoagulants — are recommended when the risk of stroke is moderate or high, but not when the risk of stroke is low. Rates of stroke among patients with a CHADS2 score of 0 are low (<2.0 per 100 patient years), but rise with greater CHADS2 scores. [CHADS2 is a score used to evaluate stroke risk and guide selection of anti-thrombotic therapy for non-valvular AF.] Over the decade following the introduction of CHADS2, a number of medical organizations adopted its usage into their guidelines and began suggesting OAC therapy for patients with CHADS2 scores of at least 1. This study sought to quantify trends and evaluate guideline adherence with OACs in Veterans with newly diagnosed AF over a ten-year period (October 2001 – September 2011) within the VA healthcare system. CHADS2 scores were determined using the Veteran's age and diagnoses of hypertension, diabetes, heart failure, and stroke or TIA (transient ischemic attack) during the 12 months prior to AF diagnosis. Investigators used VA pharmacy data to evaluate receipt of an OAC (warfarin or dabigatran) within 90 days of a new AF diagnosis. New AF was defined by at least two clinical encounters documenting AF within 120 days of each other – and with no previous AF diagnosis (N=297,611). Prescriptions for the anti-platelet agent clopidogrel also were identified.
- Among Veterans with new atrial fibrillation and additional risk factors for stroke, only about half received an oral anticoagulant, and the proportion is declining, including among patients with higher risks for stroke. Overall, initiation of an OAC fell from 51% in 2002 to 43% in 2011.
- For patients with a CHADS2 score of 0, 1, 2, 3, 4, and 5-6, the proportions of Veterans prescribed an OAC showed a relative decrease of 26%, 23%, 14%, 12%, 9%, and 13%, respectively. Patterns persisted even after controlling for contraindications to anticoagulation.
- The decrease in oral anticoagulant use was partially offset by a modest increase in the use of clopidogrel. From 2002 through 2011, the overall use of clopidogrel increased from 9% to 10%.
- The decline in oral anticoagulant use shown in these results is concerning because patients with AF who fail to receive recommended OAC therapy have high rates of preventable stroke. This study, as well as others, shows an opportunity to improve rates of guideline adherence.
- The accuracy of some ICD-9-CM AF diagnoses may be questionable. Investigators were unable to capture prescriptions received outside VA or aspirin use (sold over the counter); however, it is unlikely that aspirin use increased enough to explain the decrease in prescription OACs.
This study was partly funded by HSR&D. Drs. Buck, Kaboli, and Vaughan Sarrazin are part of HSR&D's Comprehensive Access and Delivery Research and Evaluation Center (CADRE), Iowa City, IA.
Buck J, Kaboli P, Gage B, Cram P, and Vaughan Sarrazin M. Trends in Antithrombotic Therapy for Atrial Fibrillation: Data from the Veterans Health Administration Health System. American Heart Journal. June 21, 2016; ePub ahead of print.