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Original Investigation
Association of VA Surgeons
December 26, 2018

Association Between Antithrombotic Medication Use After Bioprosthetic Aortic Valve Replacement and Outcomes in the Veterans Health Administration System

Author Affiliations
  • 1Health Services Research and Development, Center for Health Information and Communication, Richard L. Roudebush VA Medical Center, Department of Veterans Affairs, Indianapolis, Indiana
  • 2Health Services Research and Development, Precision Monitoring to Transform Care, Quality Enhancement Research Initiative, Department of Veterans Affairs, Indianapolis, Indiana
  • 3Department of Internal Medicine, Indiana University School of Medicine, Indianapolis
  • 4Department of Neurology, Indiana University School of Medicine, Indianapolis
  • 5Regenstrief Institute, Indianapolis, Indiana
  • 6VA Evidence-Based Synthesis Program, Portland, Oregon
  • 7Department of Internal Medicine, Portland VA Medical Center, Portland, Oregon
  • 8Department of Internal Medicine, Oregon Health & Science University, Portland
  • 9Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland
  • 10Department of Biostatistics, Indiana University School of Medicine, Indianapolis
  • 11Department of Surgery, VA Boston Healthcare System, West Roxbury, Massachusetts
JAMA Surg. Published online December 26, 2018. doi:10.1001/jamasurg.2018.4679
Key Points

Question  Because the recommendations about antithrombotic medication use after bioprosthetic aortic valve replacement (bAVR) vary, how does post-bAVR antithrombotic practice across the Veterans Health Administration differ, and what are the associations between antithrombotic strategies and outcomes?

Findings  Among 9060 veterans with bAVR at 47 facilities in this cohort study, the most commonly prescribed antithrombotic strategy was aspirin only. Adverse events were uncommon; patients receiving the combination of aspirin plus warfarin sodium had higher odds of bleeding than patients receiving aspirin only.

Meaning  The combination of aspirin plus warfarin does not improve either mortality or thromboembolism risk but may increase the risk of bleeding compared with aspirin only for patients with bAVR.

Abstract

Importance  The recommendations about antithrombotic medication use after bioprosthetic aortic valve replacement (bAVR) vary.

Objectives  To describe the post-bAVR antithrombotic medication practice across the Veterans Health Administration (VHA) and to assess the association between antithrombotic strategies and post-bAVR outcomes.

Design, Setting, and Participants  Retrospective cohort study. Multivariable modeling with propensity scores was conducted to adjust for differences in patient characteristics across the 3 most common antithrombotic medication strategies (aspirin plus warfarin sodium, aspirin only, and dual antiplatelets). Text mining of notes was used to identify the patients with bAVR (fiscal years 2005-2015).

Main Outcomes and Measures  This study used VHA and non-VHA outpatient pharmacy data and text notes to classify the following antithrombotic medications prescribed within 1 week after discharge from the bAVR hospitalization: aspirin plus warfarin, aspirin only, dual antiplatelets, no antithrombotics, other only, and warfarin only. The 90-day outcomes included all-cause mortality, thromboembolism risk, and bleeding events. Outcomes were identified using primary diagnosis codes from emergency department visits or hospital admissions.

Results  The cohort included 9060 veterans with bAVR at 47 facilities (mean [SD] age, 69.3 [8.8] years; 98.6% male). The number of bAVR procedures per year increased from 610 in fiscal year 2005 to 1072 in fiscal year 2015. The most commonly prescribed antithrombotic strategy was aspirin only (4240 [46.8%]), followed by aspirin plus warfarin (1638 [18.1%]), no antithrombotics (1451 [16.0%]), dual antiplatelets (1010 [11.1%]), warfarin only (439 [4.8%]), and other only (282 [3.1%]). Facility variation in antithrombotic prescription patterns was observed. During the 90-day post-bAVR period, adverse events were uncommon, including all-cause mortality in 127 (1.4%), thromboembolism risk in 142 (1.6%), and bleeding events in 149 (1.6%). No differences in 90-day mortality or thromboembolism were identified across the 3 antithrombotic medication groups in either the unadjusted or adjusted models. Patients receiving the combination of aspirin plus warfarin had higher odds of bleeding than patients receiving aspirin only in the unadjusted analysis (odds ratio, 2.58; 95% CI, 1.71-3.89) and after full risk adjustment (adjusted odds ratio, 1.92; 95% CI, 1.17-3.14).

Conclusions and Relevance  These data demonstrate that bAVR procedures are increasingly being performed in VHA facilities and that aspirin only was the most commonly used antithrombotic medication strategy after bAVR. The risk-adjusted results suggest that the combination of aspirin plus warfarin does not improve either all-cause mortality or thromboembolism risk but increases the risk of bleeding events compared with aspirin only.

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