In vitro clot model to evaluate fibrin-thrombin effects on fractal dimension of incipient blood clot.

INTRODUCTION: This aim of this study is to investigate the individual effects of varying concentrations of thrombin and fibrinogen on clot microstructure (characterised through the fractal dimension of the incipient clot network, df) and clot formation time ( TGP) using a fibrin-thrombin clot model. df and TGP markers are measured using a haemorheological method that has already been investigated for whole blood. METHODS: This is an in vitro study using three thrombin concentrations (0.1, 0.05 and 0.02 NIH/ml) and two fibrinogen concentrations (8 mg/ml and 12 mg/ml) to investigate a fibrin-thrombin clot model. The haemorheological changes were measured at the gel point using df and TGP. RESULTS: Fractal dimension (df) increased with increasing concentrations of thrombin both at 8 mg/ml (1.60 +/- 0.024, 1.67 +/- 0.022, 1.74 +/- 0.079) and 12 mg/ml fibrinogen concentrations (1.63 +/- 0.02, 1.87 +/- 0.019, 1.95 +/- 0.014). On the other hand, TGP decreased for both 8 mg/ml (1089 +/- 265, 637 +/- 80, 223 +/- 22 seconds) and 12 mg/ml fibrinogen concentrations (2008 +/- 247, 776 +/- 20, 410 +/- 20 seconds). In contrast to previous studies investigating whole blood, TGP increased with higher fibrinogen levels. CONCLUSIONS: The findings from this fibrin-thrombin clot model confirmed that df and TGP can detect changes in the incipient clot following manipulation of fibrinogen and thrombin concentration. df increases (indicating stronger clot) with higher concentrations of thrombin and fibrinogen. On the other hand, TGP decreased as expected with higher thrombin level but not with higher fibrinogen concentrations.