Altered fibrin clot properties are associated with residual vein obstruction: Effects of lipoprotein(a) and apolipoprotein(a) isoform

We tested the hypothesis that fibrin structure/function is unfavorably altered in patients with residual vein obstruction (RVO). Ex vivo plasma fibrin clot permeability, turbidimetry and efficiency of fibrinolysis were investigated in 86 patients with RVO following first-ever proximal deep vein thrombosis (DVT), and 86 DVT controls with no evidence of RVO. The RVO patients had 14.1% lower clot permeability (p = 0.011), 11.3% longer lysis time (p = 0.009) and 7.8% lower rate of D-dimer release from fibrin clots than controls (p = 0.022), with no differences related to thrombophilia, and duration or stability of anticoagulant therapy. RVO patients showed higher lipoprotein(a) (p = 0.014) with overrepresentation of smaller apolipoprotein(a) isoforms, corresponding approximately to 21 or fewer kringle IV type 2 repeats (p = 0.09), both associated with alterations to plasma fibrin clot characteristics. In conclusion, prothrombotic plasma fibrin clot phenotype related to elevated lipoprotein(a) with smaller apolipoprotein(a) isoforms might represent a novel risk factor for RVO.