Study of endovascular devices: Guidewires and balloon catheters
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A guide wire is a flexible wire positioned in an organ, vessel, or duct for the purpose of directing the passage of a larger device threaded over or along its length. The mechanical properties of a guide wire could help determine its success during positioning and determining the effects of the guidewire on the inner lining of the vessel i.e. endothelial cell erosion. There have been recent advances in guide wire technology with the advent of minimally invasive endovascular treatments. Various companies manufacture guidewires with improved radio opacity, torquability and pushability. All these variables are qualitatively defined; however they do not indicate quantitatively the amount of influence they have on the usability of the guide wire. For these purposes, various experimental evaluations were carried out to assess and compare all the available guidewires quantitatively. Our research involved, studying the torquability of the guidewires and elucidating the effects of various parameters that inhibited torque transfer from the proximal end to the distal end. With this view in mind, the experiments were divided into two groups. In the first group torsional rigidity of guidewires from leading companies were evaluated. In the second group, we studied the relationship between torque transfer from proximal end to the distal end, while the guidewire was located in tortuous simulated blood vessels of different curvatures and bends. The actual path of the guidewire from the femoral artery to the aorta in our simulated phantoms while not precisely derived from actual human morphology was in the range of actual tortuosities. However, we aimed to concentrate on the mechanical properties like torsional rigidity, frictional force and the effect of number of bends and radius of curvature to help the future engineers and designers to make guidewires which would transmit torque from the site of operation to the site of action with maximum efficiency and least damage. For this, a correlation between both the groups was done and we came to the conclusion that as the torsional rigidity increased, the transfer of torque from the proximal to the distal end was more continuous and efficient. However, this was at the cost of higher stresses at the wall of the phantom. Our research may help designers and engineers manufacture guidewires with mechanical properties that make a compromise between the torsional rigidity and the compliancy of the guidewire. Both the properties are important; however keeping in mind that de-endothelialization does not necessarily make the vessel dysfunctional, torsional rigidity is the property that should be high in an ideal guidewire. The exact value of torsional rigidity would require further research into how the guidewire contacts the surfaces of the phantoms with varying number of bends and radius of curvatures.