AHA Statement Examines Antithrombotic Undertreatment in AF, VTE, and PAD

Antithrombotic undertreatment remains common among patients with atrial fibrillation (AF), venous thromboembolism (VTE), and peripheral artery disease (PAD), according to a scientific statement from the American Heart Association (AHA) published online October 1 in Circulation.

The statement authors define undertreatment as omission, nonadherence, underdosing, and clinical circumstances that result in subtherapeutic antithrombotic levels. They wrote that undertreatment has been shown to increase rates of ischemic stroke, systemic embolism, recurrent thrombosis, and mortality. They attributed it to deviation from evidence-based practice, misperceptions of bleeding versus thrombotic risk, and inequities in healthcare access.

In AF, a US Medicare claims analysis cited in the statement found that 59% of patients newly diagnosed with AF and a CHA₂DS₂-VASc score of 2 or higher were not prescribed any anticoagulant. The authors reported that inappropriate direct oral anticoagulant (DOAC) dosing occurs in up to 20% of patients with AF. In one meta-analysis, reduced-dose DOACs prescribed without a clear clinical indication were not associated with lower bleeding risk. However, they were associated with a 28% increase in all-cause mortality (hazard ratio, 1.28; 95% CI, 1.10-1.49).

In VTE, off-label DOAC underdosing was associated with increased mortality and new thromboembolism, with no reduction in bleeding. In PAD, a meta-analysis of 125 observational studies including more than 14 million patients found that 28% of eligible individuals lacked an antiplatelet prescription. The authors identified several groups at higher risk of antithrombotic underuse. These include older adults; patients with impaired renal function, frailty, fall risk, or dementia; patients with lower socioeconomic status, limited pharmacy access, or inadequate insurance coverage; and Black, Hispanic, and Native American populations.

The authors described antithrombotic stewardship as an opportunity to address these gaps through structured, interdisciplinary approaches. They noted that further study is needed to clarify what drives underdosing and underprescribing. They also noted that older adults with frailty, fall risk, or cognitive impairment are underrepresented in clinical trials.

Source: Rudd K, Bessada Y, Barnes GD, et al. Impact of undertreated antithrombotic therapy on adverse patient outcomes: a scientific statement from the American Heart Association. Circulation. Published online October 1, 2026. doi:10.1161/CIR.0000000000001474