Characterisation of clot microstructure properties in stable coronary artery disease

Figures

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  Figure 1. Diagram of a double-gap concentric cylinder measurement geometry. The double-gap geometry consists of a stationary cup or stator into which a 6.6 mL sample of blood is added after which a bob that is free to rotate called a rotor is then lowered into the sample. The movement of the rotor is controlled by an AR-G2-controlled stress rheometer and will oscillate at four different frequencies (0.20, 0.43, 0.93 and 2.00 Hz) sequentially over time.

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  Figure 2. Gel point (GP) trace. This represents a typical GP result for one sample of blood. The illustration demonstrates how phase angle, δ, changes as coagulation progresses. δ has a range of 0° to 90°, where 90° identifies a purely viscous response and 0° identifies a purely elastic response with any value in between being a measure of the viscoelastic response to imposed stress. In a material that is changing from a liquid to a solid such as blood, there will be a decrease in δ. At the establishment of the incipient clot, when the clot becomes a viscoelastic solid, there is a point where the value of δ will be independent of frequency called the GP. The structural property of the incipient clot (in terms of its fractal dimension, df) is derived from this frequency independent value of δGP.

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  Figure 3. A graph showing the dispersion of df measurements among the unobstructed and the obstructed coronary artery disease (CAD) groups, where a significant increase in the value of df was observed for those patients with obstructive CAD when compared with unobstructed (df=1.748±0.057 vs 1.732±0.052, p=0.028).

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  Figure 4. Fractal dimension (df) versus mass. Graph showing the simplified non-linear relationship between df and the amount of mass incorporated into the incipient clot microstructure. Fibrin networks have fractal properties, where the mass, M, is related to df by the following power law equation (M≈ɛdf, where ɛ is some length scale value in the range 100 nm to 10 µm). The mass value on the y-axis is normalised to the unobstructed CAD value of df=1.732, where at a df of 1.732 the normalised mass value is equal to 1 (blue dotted lines). The figure illustrates that a structure that forms with a df of 1.748, like the mean value of the obstructive CAD group (red dotted lines) would have an increased relative mass compared with a structure that formed with a df value of 1.732, having 1.27 times more mass.