Novel methods for the mechanical characterization of patches used in carotid artery repair.

Carotid endarterectomy (CEA) is one of the approaches available for the treatment of carotid artery disease, with carotid patch angioplasty the pertinent technique mostly preferred by vascular surgeons. This technique entails an arteriotomy succeeded by closure with a textile, polymer or biological tissue patch. In this work, we propose microbuckling and microindentation as novel methodologies for acquiring the mechanical properties of patches used in carotid artery repair. Regarding microbuckling, the patch is loaded by a sensitive dynamometer at one end and its motion is recorded, at three different levels of axial deformation: δ/ℓ = 0.1, 0.3 and 0.5 (in the post-buckling regime). The corresponding experimental loads are recorded, as well. Following pertinent closed-from equations, various material metrics are obtained, such as the Young's modulus of elasticity and the so-called frictional couple of the material. Regarding microindentation, the material's hardness number is measured with the aid of a durometer. Similar to microbuckling, indentation analytical expressions allow for the determination of key material properties, such as the modulus of elasticity, indentation forces and depths. Where possible, we perform microtension to verify acquired results. Results demonstrate that measured properties may vary substantially for materials which are of the same type, due to variations of the material microstructure, as observed with optical and scanning electron microscopes (SEM). Several commercial patches were tested in this work. To shortly present the main results, the microbuckling technique furnished (for the Young's modulus) 40.17 MPa for the B/Braun Aesculap cardiovascular patch and 71.49 MPa for the Vasutek Terumo, while the microindentation technique, for bovine patches, provided 6.356 MPa for the Xeno Sure and 4.701 MPa for the Vascu-Guard. A test type recommendation is provided, relating the type of the patch material to the method more plausible in each case, in order to achieve better measurement accuracy. Results of this study can contribute in establishing guidelines and criteria determining material selection in CEA.