VWF and pulmonary arterial hypertension: Serum levels of soluble vWF (fig 3A) were increased in patients with SSc-PAH (1043 (97) mU/ml) and patients with SSc without PAH (1061 (86) mU/ml) in comparison with the HD group (770 (54) mU/ml, p<0.05) and did not change after 12 months of bosentan therapy (980 (89) mU/ml, not significant vs baseline).