Abstract 2641: Plasma Von Willebrand Factor and ADAMTS13 Concentrations in Atrial Fibrillation

Background : Von Willebrand factor (VWF) is released from damaged endothelium, and has a role in platelet aggregation through a receptor on the platelet surface. A metalloprotease that cleaves VWF multimers has been identified, namely, ADAMTS13. We recently reported that the serial changes in plasma VWF and ADAMTS13 antigen levels in patients with acute myocardial infarction (AMI), and that the VWF/ADAMTS13 ratio was a useful prognostic indicator of long-term thrombotic events after AMI. Although previous studies have shown raised plasma VWF in patients with atrial fibrillation (AF), little is known about the role of ADAMTS13 in the pathogenesis of AF. In the present study, we examined the relation between VWF and ADAMTS13 in AF patients. Methods and Results : We measured the plasma VWF and ADAMTS13 antigen levels by ELISA in 45 AF patients and 49 control subjects, and also performed echocardiography to examine the relations between these markers and left atrial or ventricular functions. The plasma VWF antigen levels were significantly higher in AF patients compared with controls (2017±749 vs. 1504±497 mU/ml, P=0.0002). In contrast, the plasma ADAMTS13 antigen levels were significantly lower in AF patients compared with controls (825±181 vs. 911±193 mU/ml, P=0.03). The VWF/ADAMTS13 ratio was significantly higher in AF patients compared with controls (2.59±1.20 vs. 1.75±0.76, P<0.0001). The number of patients who received aspirin and warfarin was significantly higher in AF group than control subjects, however, those medical therapy did not affect the VWF and ADAMTS13 antigen levels. There was significant positive correlation between VWF antigen levels and the left atrial dimension (n=128, r=0.228, P=0.0095). Furthermore, there was significant negative correlation between VWF antigen levels and the left atrial appendage peak flow velocity measured by transesophageal echocardiography (n=23, r=-0.611, p=0.0015). Conclusions : These findings suggest that the balance between VWF and ADAMTS13 levels may play an important role in the intra-atrial thrombus formation in AF patients. The present results would open a new therapeutic target for prevention of thromboembolic complications in AF.