In-vitro study of effect of the design of the stent on the arterial waveforms

Peripheral arterial disease (PAD) occurs as a result of atherosclerosis, which involves plaque formation on the inner walls of the arteries. This reduces the size of the vessel's lumen and restricts blood flow to the leg muscles, leading to pain, the death of tissue and even the amputation of the lower leg. One treatment method for PAD is the placement of a stent, which acts as a scaffold holding open the artery, increasing blood flow to the lower extremities. However, the stents for PAD are known to fail more regularly due to the complicated biomechanical conditions such as heavy calcified and long atherosclerotic lesions. Stenting in the peripheral arteries still fail in 25% of vessels after 2 years. One of the major influences on the rate of restenosis is the rate at which the platelets become activated. This activation is controlled by changes of wall shear stress, which is in turn influenced by the flow rate, and pressure. This study hypothesizes that stents in the arteries can cause the reflection of the waveform, which would alter the flow rate and pressure waveforms, causing increase in the rate of restenosis. This is potentially why various in-vivo studies have found that stents with thicker struts cause increased levels of restenosis. In this study, the effect of stent design on haemodynamic flow will be investigated, with the intention of optimising the designs currently in use in medicine. By setting up an in-vitro experiment, with an artificial artery, it is possible to record the flow rate, change in diameter and pressure caused to the blood flow by the stent. In this experiment, it is intended to use a series of 3D printed stents of two designs (Palmaz and Zigzag), with differing, strut thickness to determine which causes the most reflection, in an attempt to optimise the stent design.