Endovascular stent grafting of thoracic aortic aneurysm

Thoracic aortic aneurysm (TAA) can be a silent killer if left untreated. Open surgery needs a longer recovery process and is not suitable for highrisk patients. Thoracic endovascular aortic repair (TEVAR) has been introduced as a less invasive approach to management of thoracic aortic aneurysm (TAA). Common TEVAR approaches involve implantation of a simple Dacron stent graft through a catheter. However, the effectiveness of TEVAR in the management of TAA is often limited by the complex anatomy of the aortic arch. Branched and fenestrated stent grafts have been developed to preserve perfusion of superior branches with a low incidence of sealing zone failure. The disadvantage of the branched and fenestrated techniques is that they require custom-made devices and complex procedures, which make them less promising in urgent TEVAR. Moreover, the branched and fenestrated stent grafts have been shown to be prone to proximal endoleak that could lead to increased mortality. Another novel technique is called chimney technique. Chimney technique is a stent placed parallel to the aortic stent graft to preserve the blood flow to superior branches that was overstented to achieve an adequate seal. Even though the technique outcome is encouraging, it is difficult to fabricate a dedicated covered stent for chimney repair. In this chapter, we will discuss the novel stenting technique for TAA which applies engineering fluid mechanics knowledge on the innovation of medical device. Innovative devices such as the multilayer flow modulator (MFM) have recently been proposed to provide an alternative endovascular treatment. The main purpose of MFM is to decrease the risk of rupture by modulating the flow pattern which can then lead to a reduction in local shear stress along the weakened artery wall. We will evaluate the pros and cons of disruptive technologies such as MFM and compare them with the above-mentioned methods such as conventional TEVAR, fenestrated, and chimney repair. An overview of the elective and emergency approach using MFM and other innovative approaches published in the existing literature will be discussed. This review indicates that although most of the innovative techniques appear to be successful, the expansion of aneurysm does not slow down immediately, and usually, only a short period of follow up results are presented. These innovations will require more clinical trials and longer follow up studies to confirm the feasibility of this disruptive technology. The presented review in this chapter can provide great insight into the nature, diagnosis, and potential improvements for the intervention involving TAA.