Additive role of plasma von Willebrand factor levels to clinical factors for risk stratification of patients with atrial fibrillation.

BACKGROUND AND
PURPOSE: To aid decisions for thromboprophylaxis in atrial fibrillation (AF), several risk stratification schemes that predict stroke risk according to clinical and echocardiographic features have been published. von Willebrand factor (vWf) is a plasma markers of endothelial damage/dysfunction and is associated with the risk of stroke and vascular events in AF patients. This study determined the additive role of plasma vWf levels to clinical factors for risk stratification in patients with AF.
METHODS: We classified 994 AF patients who were enrolled in the SPAF III trial as being at low, moderate, or high risk of stroke and thromboembolism according to the Birmingham and CHADS(2) risk stratification schemes. vWf levels were classified as elevated when >or=158 IU /dL. Rates of ischemic stroke and vascular events within each clinical risk stratum with and without plasma vWf levels were compared.
RESULTS: The accuracy of both clinical risk stratification schemes was similar for predicting event rates (Birmingham: ischemic strokes, 0.642; vascular events, 0.670; CHADS(2): ischemic strokes, 0.672; vascular events, 0.672). Subsequent addition of categorized vWf levels to both clinical risk stratification schemes further refined risk stratification for stroke and vascular events. When added to the Birmingham and CHADS(2) clinical risk stratification, high vWf levels were independently associated with a risk of vascular events (hazard ratio, 2.05; 95% confidence interval, 1.30 to 3.22 and 2.01, 1.27 to 3.18 with Birmingham and CHADS(2), respectively) but not ischemic stroke.
CONCLUSIONS: When added to clinical risk stratification schemes (Birmingham; CHADS(2)), plasma vWf levels refined clinical risk stratification for stroke and vascular events among AF patients. vWf levels may aid decisions about thromboprophylaxis, particularly among AF patients at moderate risk.