Elaine M. Hylek

Age and the risk of warfarin-associated hemorrhage: the anticoagulation and risk factors in atrial fibrillation study.

OBJECTIVES: To assess whether older age is independently associated with hemorrhage risk in patients with atrial fibrillation, whether or not they are taking warfarin therapy.

Factor V Leiden and risk of ischemic stroke in nonvalvular atrial fibrillation: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study.

AbstractBackground: Atrial fibrillation is a major cause of cardioembolic stroke. Since atrial and venous pressures are similar, genetic variants that promote venous thromboembolism may increase the risk of atrial thrombi and subsequent stroke in atrial fibrillation. Methods: We conducted a nested case-control study of the association between the presence of factor V Leiden polymorphism and incident ischemic stroke within a prospective cohort of 13,559 adult patients with diagnosed nonvalvular atrial fibrillation between July 1, 1996 and December 31, 1997. Incident cases with ischemic strokes were identified through August 31, 1999 and matching stroke-free controls were enrolled. Results: One hundred thirty-seven case patients with incident stroke and 214 controls were enrolled. Cases were older, more likely to be women, and more likely to have a prior stroke, heart failure, hypertension, diabetes, and coronary disease. The factor V Leiden polymorphism was present in 5.8% of cases and 3.7% of controls (P = 0.36). Among non-anticoagulated patients, 7/96 (7.3%) case patients and 3/81 (3.6%) control subjects were heterozygous for factor V Leiden (Odds Ratio 2.1 [95% CI: 0.5–8.4]). Adjustment for known stroke risk factors did not significantly change the observed association in non-anticoagulated patients (adjusted OR 1.9 [0.5–8.0]). Conclusions: Within a large nested case-control sample of patients with atrial fibrillation, factor V Leiden was not significantly associated with risk of stroke. However, given the suggestive nature of our findings, further study in even larger numbers of patients is needed to clarify the impact of factor V Leiden on stroke risk in atrial fibrillation.

Trends in anticoagulation management across community-based practices in the United States: the Anticoagulation Consortium to Improve Outcomes Nationally (ACTION) study.

Randomized trials have demonstrated the effectiveness of warfarin in preventing thromboembolism. Translating the results of randomized trials into usual care is difficult, however, as trial patients are highly selected and closely monitored. The Anticoagulation Consortium to Improve Outcomes Nationally (ACTION) study is a prospective observational assessment of anticoagulation care in 98 office-based practices and 3 hospital-based clinics in the United States. Site enrollment began in August 2000 and ended in February 2002 with 6761 patients recruited. The goals of this large prospective cohort study are (1) to gather data on complication rates associated with warfarin therapy across a broad range of patient ages and indications; (2) document trends in anticoagulation management and treatment practices; and (3) establish quality benchmarks for anticoagulation control and frequency of monitoring. This report describes the methodology and preliminary results. Analysis is ongoing, and full results will be reported in the future.