Initial Study Of The Model Of Vascular Graft With Helical Slot

Although large- and medium-sized arterial grafts are very satisfactory, small-calibre grafts, with 5-6 mm diameter and less, have been disappointing because of acute thrombus formation in the short term and intimal hyperplasia in the long term and are in large demand for coronary and peripheral bypass procedures. Based on the vascular anatomical characters and low shear stress hypothesis, a new type of graft with special internal surface configuration, which can increase the velocity near the internal surface, impede the occurring of thrombus formation and intimal hyperplasia to enhance graft patency rate,was designed.First, the model of rigid tube with spiral slot and the control model of rigid tube with nothing on the internal face were set up by Computer Aided Design (CAD) software Solid Works. Then simulation was carried out with Computational Fluid Dynamics (CFD) software to compare the velocity distribution in the two tubes. Then optimum flow field system and vision system were set up. Under pulsing flow, which is closer to the physiological condition, the flow in both kinds of tubes was taken pictures to prepare for future Particle Image Velocimetry (PIV). At last, by cooperation with a company abroad, polyester vascular grafts with helicoidal crimps and concentric crimps were manufactured. Preparatory canine model experiment was carried out.The result of simulation of the flow in the two kinds of tubes with CFD software PHOENICS stated that the slot made the velocity near the internal surface increase while the velocity in the axes area decrease. So the aim to enhance the velocity near the internal surface to shorten particle residence time was achieved. The system of PIV was set up. At four different parts of the tubes, pictures were taken respectively under four levels of velocity. Vascular grafts with helicoidal crimps were implanted in abdominal aorta bypass surgery in preparatory canine model experiment.This research proved the model of vascular graft with helical slots could change the velocity distribution near the internal surface, which could enhance graft patency rate. The rigid model could also be applied in polyester vascular graft manufacturing and the grafts with helicoidal crimps and concentric crimps could be used in animal experiment to compare their patency.