Top Things to Know: The Impact of Undertreated Antithrombotic Therapy on Adverse Patient Outcomes

Updated: October 01, 2026

Prepared by Youssef Bessada, PharmD, BCPS, BCCP and Kelly M. Rudd, PharmD, BCPS, CACP, FCCP

  1. Antithrombotic therapy is a cornerstone in the approach to reducing the complications of several vascular disorders, including atrial fibrillation (AF), venous thromboembolic disease (VTE), and peripheral vascular disease (PVD). However, balancing the benefits of thrombosis prevention and risks, particularly of medication-related bleeding, is a significant concern for healthcare providers.
  2. Antithrombotic undertreatment encompasses several potential clinical scenarios, including 1) the prescribing doses of oral anticoagulant (OAC) medications that intentionally fall below the approved and/or evidence-based suggested dosing; 2) omitting OAC therapy when clinically indicated; 3) fostering situations where antithrombotic agent levels fall below therapeutic thresholds (i.e., drug-drug interactions or inappropriate dose adjustments); and/or 4) patient nonadherence with antithrombotic therapy.
  3. This scientific statement summarizes the current knowledge that antithrombotic undertreatment remains a widespread and clinically significant issue in AF, VTE, and PAD, contributing to preventable morbidity, mortality, and increased health care burden.
  4. In AF, large real-world datasets reveal that antithrombotic undertreatment remains widespread and multifactorial, particularly among older adults, frail individuals, those with cognitive impairment, and racial/ethnic minority populations. Nonadherence, OAC underuse, and underdosing are the primary modalities of antithrombotic undertreatment.
  5. The AF data indicate that OAC underdosing of direct-acting oral anticoagulants (DOACs) offered no reduction in bleeding but was associated with increased thromboembolic events and mortality, reinforcing the importance of evidence-based dosing strategies.
  6. In VTE, therapy omission, underdosing, and inconsistent use of prophylaxis are present despite well-defined guideline-supported anticoagulation strategies for both acute treatment and extended management phases. Data indicate this is a multifactorial challenge driven by bleeding concerns, dosing uncertainty, and system-level barriers.
  7. In PAD, antithrombotic undertreatment, including underuse of antiplatelet agents and low adoption of dual pathway inhibition (DPI), contributes to increased major adverse cardiac events (MACE), major adverse limb events (MALE), and higher amputation-related mortality. These adverse outcomes are amplified by socioeconomic and race-ethnic disparities.
  8. In addition to the populations noted above, data indicate that additional populations are at increased risk for undertreatment. These include patients with impaired renal function or dementia, frail or fall-prone individuals, pregnant and postpartum individuals, and those experiencing barriers related to cost, pharmacy access, or socioeconomic disadvantage.
  9. Antithrombotic Stewardship, defined as coordinated, system-level, interdisciplinary efforts to optimize antithrombotic therapy, has emerged as a critical strategy to reduce underdosing, improve adherence, minimize adverse events, improve outcomes, and standardize evidence-based care.
  10. Addressing antithrombotic undertreatment requires sustained system-level change, expansion of antithrombotic stewardship, improved access to therapy, and focused efforts within at-risk populations. As health care teams continue to strengthen interdisciplinary collaboration and integrate evidence-based, stewardship strategies, meaningful progress can be achieved in reducing preventable thrombotic events and improving long-term patient outcomes across AF, VTE, and PAD.

View the summary for The Impact of Undertreated Antithrombotic Therapy on Adverse Patient Outcomes

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Citation

Rudd K, Bessada Y, Barnes GD, Bronas UG, Budd AN, Goot T, Montanez NA, Trujillo T; on behalf of the American Heart Association Council on Peripheral Vascular Disease; Council on Arteriosclerosis, Thrombosis and Vascular Biology; Council on Cardiovascular and Stroke Nursing; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Surgery and Anesthesia; Council on Clinical Cardiology; Council on Lifelong Congenital Heart Disease and Heart Health in the Young; and Stroke Council. The impact of antithrombotic therapy undertreatment on adverse patient outcomes: a scientific statement from the American Heart Association. Circulation. Published online October 1, 2026. doi: 10.1161/CIR.0000000000001474
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