Objective: We sought to investigate whether patients with in-stent thrombosis (IST) display altered plasma fibrin clot properties.
Methods and results: We studied 47 definite IST patients, including 15 with acute, 26 subacute and 6 late IST, and 48 controls matched for demographics, cardiovascular risk factors, concomitant treatment and angiographic/stent parameters. Plasma clot permeability (K(s)), which indicates a pore size, turbidity (lag phase, indicating the rate of fibrin clot formation, DeltaAbs(max), maximum absorbance of a fibrin gel, reflecting the fiber thickness), lysis time (t(50%)) and maximum rate of D-dimer release from clots (D-D(rate)) were determined 2 to 73 (median 14.7) months after IST. Patients with IST had 21% lower K(s), 14% higher DeltaAbs(max), 11% lower D-D(rate), 30% longer t(50%) (all P<0.0001) and 5% shorter lag phase compared to controls (P=0.042). There were no correlations between clot variables and the time of IST or that from IST to blood sampling. Multiple regression analysis showed that K(s) (odds ratio=0.36 per 0.1 microm(2), P<0.001), D-D(rate) (odds ratio=0.16 per 0.01 mg/L/min, P<0.001) and stent length (odds ratio=1.1 per 1 mm, P=0.043) were independent predictors of IST (R(2)=0.58, P<0.001).
Conclusions: IST patients tend to form dense fibrin clots resistant to lysis, and altered plasma fibrin clot features might contribute to the occurrence of IST.