The Mechanical Characterisation of Bovine Embolus Analogues Under Various Loading Conditions

Abstract

Embolus Analogues (EAs) can provide understanding of the mechanical characteristics of blood clots of cardiac origin. Bovine EAs (n = 29) were fabricated with varying concentrations of thrombin (0-20 NIHU/ml blood). Histological staining confirmed that EA composition compared sufficiently with human samples reported in literature. EAs were mechanically described under seven testing conditions: tensile, compression, shear wave ultrasound elastography (SWE), parallel plate rheometry, indentation, creep and relaxation. The Young modulus of bovine EAs in tension varied from 7 kPa (5% strain) to 84 kPa (50% strain). The compressive Young modulus increased with increasing thrombin concentration, which was in agreement with the SWE results. There was no significant difference in Young modulus throughout the clot (p < 0.05). The EAs displayed a non-linear response under parallel plate rheometry, creep and stress relaxation. The 3rd order Mooney-Rivlin constitutive equation and Standard Linear Solid model were used to fit the non-linear stress-strain response and time-dependent properties, respectively. This is the first study in which bovine EAs, with and without addition of thrombin, are histologically and mechanically described with corresponding proposed constitutive equations. The equations and experimental data determined can be applied for future numerical and experimental testing of mammalian EAs and cardiac source clots.

Mechanical behavior of in vitro blood clots and the implications for acute ischemic stroke treatment

“…The clot analogues were found to have a similar, non-linear stress-strain relationship and mechanical behaviour to published data for clot material 5 7 8 22. The NCCs were found to be less stiff than the PCCs across all hematocrits.…”

“…MT procedures are significantly affected by the mechanical properties of the thrombus itself. Clinically relevant thrombus analogues provide a useful tool in the preclinical testing of thrombectomy devices to evaluate device design by measuring, among other things: the ability to capture and remove the occlusive thrombus, the number of attempts required, and the risk of procedure related embolism 4–8…”

Blood clot fracture properties are dependent on red blood cell and fibrin content

“…Previous studies have investigated clot hyperelastic and viscoelastic behaviour using compression testing [27][28][29][30] and tensile testing [18,[31][32][33][34]. However, no study to date has investigated the fracture properties of blood clots.…”

An in vitro assessment of atrial fibrillation flow types on cardiogenic emboli trajectory paths

“…34 Ovine, porcine and bovine blood is the most frequently used mammalian blood for EA replication. 17,26,35–38 Bovine blood was chosen for EA manufacture as the supply was in close proximity to the laboratory (Burkes Abattoir Ltd, Galway, Ireland) and also, on a macro level, the composition of bovine blood is similar to human. 39…”

“…The mechanical properties of the blood clots (Figure 1(f)) were validated by in-house methods. 26 The bovine blood clots (n = 29) were described under seven loading conditions: tensile, compression, shear wave ultrasound elastography (SWE), parallel plate rheometry, indentation, creep and relaxation. The EAs displayed a compressive Young’s modulus varying from 1.53–16.6 kPa for a percentage strain range of 5%–40%, which was similar to other compressive studies found for human retrieved emboli.…”