Abstract 3389: Why Warfarin was not used for Stroke Prevention in Atrial Fibrillation: A Detailed Review of Electronic Medical Charts

Abstract

Purpose: In an automated analysis of Regenstrief Medical Record System (RMRS) data, approximately half of patients with atrial fibrillation or flutter (AF) and a CHADS2 score of ≥2 had not been treated with warfarin for stroke prevention. The automated query of diagnoses and other coded patient data identified predefined barriers to warfarin use (e.g. history of bleeding, alcohol abuse, or history of falls) in only about half of these patients. Therefore, a detailed review of electronic medical charts (including text reports) was conducted to explore why patients with AF at high risk of stroke are not treated with warfarin. Methods: This retrospective study was a review of records from 1998 to 2007. Patients older than 18 with a diagnosis of non-valvular AF, CHADS2 score ≥2, at least one RMRS encounter within one year after the first record of AF diagnosis, and no barrier to warfarin in the automated RMRS analysis were included. A structured chart abstraction form was used to extract data. To confirm AF diagnosis, a record of AF in a clinical problem list, admission/discharge/progress report, or EKG report was required. In patients with confirmed AF, reasons why warfarin had not been prescribed were searched for, through one-by-one review of the patients, in the clinicians’ user interface. This interface displays laboratory results, diagnoses, medications, and text reports such as hospital admission and discharge summaries. Explicit (treating physician’s rationale) and implicit (potential barriers that were documented but not explicitly attached to the warfarin decision) reasons why warfarin was not used were reported using descriptive statistics. Results: Among 408 patients (mean age 73.6; 62% women), the distribution of CHADS2 scores at baseline was 2: 49%; 3: 34%; 4:12%; and 5+:6%. AF diagnosis was confirmed in 319 patients, 41% (132) of whom did not have any records in the RMRS explaining why they were not on warfarin. Among the 59% (187) with reasons (explicit 47%, or implicit 53%) why warfarin had not been started, the most common category (52% of 187) was indicative of the risk of bleeding: either the risk of fall (40%) or a history of recent bleeding (13%). The second most common category (16% of 187) reflected that the patient was back in sinus rhythm: the AF was “intermittent,” “situational,” or paroxysmal, or had been converted or ablated. Other reasons included the patient’s desire not to take warfarin, use of enoxaparin, loss to follow up, or death. Conclusion: Many patients with AF and at high risk of stroke are not treated with warfarin, and reasons for not using warfarin could not always be identified in patient records. Among patients with reasons recorded in charts, the most common reasons for not prescribing warfarin were indicative of avoiding the increased risk of bleeding.