Towards the development of guidelines for the endovascular treatment of peripheral artery disease: a tissue characterisation approach

The femoral arteries are one of the most susceptible vascular locations for the development of atherosclerosis. The occurrence of this disease process in these vessels is the leading cause of lifestyle-limiting claudication and ischemic rest pain. Common femoral endarterectomy has been the standard treatment for focal occlusive disease of the femoral arteries for over 50 years. However, morbidity rates remain high due to its invasive nature and certain groups of patients are considered high risk for surgery. The use of Percutaneous Transluminal Angioplasty (PTA) has been advocated as a treatment alternative for patients at higher risk of surgical morbidity and mortality. Despite this, the long term results for PTA in the femoral arteries are disappointing due to uncontrolled dissections in complex lesions, inadequate luminal expansion in rigid strictures and recurrent stenosis in the dilated segment. PTA therefore requires procedural, technological, and suitable patient selection enhancements to function effectively as a treatment modality. Cutting Balloon Angioplasty (CBA) is an additional treatment alternative that employs a non-compliant balloon with radially positioned microblades to incise the plaque and propagate a controlled crack thereby reducing elastic recoil, vessel dilation, vessel injury, and subsequent restenosis. Preliminary reports have highlighted the possibility of CBA application in the peripheral arteries. However, various complications have also been reported including arterial rupture, delayed perforation and fracture of microsurgical blades. Arterial injury response to endovascular treatment varies significantly with plaque composition and it has been previously stated that the mechanisms of CBA affected by plaque composition need to be clarified. Therefore, a need exists to characterise the fracture behaviour of atherosclerotic femoral tissue and relate it to plaque biological content and structural morphology. Consequently, the research objective of this thesis is to enhance the implementation of endovascular treatments of the femoral arteries by presenting novel information regarding the characteristics of the target lesion. To achieve this, the mechanical properties and fracture behaviour of human atherosclerotic femoral tissue is characterised and related to plaque biological content and structural morphology. This will facilitate for more informed patient stratification, treatment approaches, and device design. A standardised uniaxial extension protocol is proposed and employed to characterise the mechanical behaviour of 20 endarterectomised femoral plaque samples in order to determine the tissue’s response to large circumferential deformation, the conditions induced during endovascular treatment. Guillotine testing is also employed to determine the Mode I fracture toughness of 30 sections from 5 endarterectomised femoral plaque samples to examine the tissue’s ability to resist crack propagation, the conditions induced specifically during CBA. This mechanical behaviour and fracture…