Numerical Modelling and Simulations of Type B Aortic Dissection Treated by Stent-Grafts with Different Oversizing Ratios.

Retrograde type A dissection after thoracic endovascular aortic repair has been a major drawback of endovascular treatment. This study investigated the biomechanical mechanism of stent-graft induced new lesions after implantation and analyzed the relationship between radial force and spring-back force of the stent graft when it was implanted virtually under different oversizing ratios. Based on the computed tomography angiography images, a three-dimensional geometric model of a patient-specific aortic dissection was established. The stent was designed in CAD software, and the stent graft implantation procedure under different oversizing ratios were simulated in finite element analysis software. Implantation simulations were performed 6 times for each stent graft model under 0%, 3%, 6%, 9%, 12% and 15% oversizing ratios, and the peak stress of the aorta was compared among groups. It was observed that the peak stress of the aorta was located where the proximal bare stent interacted with aortic wall, and its value was increased by 62.2% from 0% to 15% oversizing ratio. The conclusions are reached that the long-term higher stress in the aortic wall may lead to the emergence of new lesions in these areas, and the radial force plays a key role in the formation of new entry in the real aorta model.