Dynamics of the aorta and its sidebranches : implications for endovascular treatment of aortic disease

Abstract

The main objective of this thesis is to critically evaluate the clinical results of emerging aortic endovascular therapies and then to utilize dynamic imaging modalities [EKG gated dynamic computerized tomographic angiography (CTA) and magnetic resonance angiography (MRA)] to understand the limitations of these technologies and potential source of any complications. The first published mid-term results of aneurysm repair with fenestrated and branched endografts from a European center of excellence is described in Chapter 2. The use of fenestrated and branched devices for difficult re-operative aortic surgery as a salvage procedure was examined in Chapter 3. These two clinical trials revealed new complications specific to fenestrated and branched devices. For example, fractured or bent side-branches and occluded renal branch vessels were observed. The potential of repeated dynamic stresses related to the cardiac cycle was postulated as a source of the problems. The dynamic effect of placing a relatively stiff endograft into a compliant, pulsatile aorta was examined in Chapter 4 through EKG-gated cine CTA. The cardiac based dynamics of the aorta was confirmed in a separate cohort of patients in Chapter 5 using the different modality of EKG-gated cine MRA. Furthermore, stent-graft design specific differences in compliance of the aorta and endograft were noted following EVAR. The renal arteries are the most commonly preserved aortic branch vessels using a fenestrated or branched technique. Furthermore, the complications identified in the fenestrated and branched clinical papers were typically related to the renal arteries. Therefore, we focused our attention on the effects of EVAR on renal artery motion in Chapter 6. Based on earlier work noting differences in stent-graft design on aortic dynamics, we evaluated the effect of three stent-graft designs (infra-re-nal fixation, supra-renal fixation, and branched) on renal artery motion in Chapter 7. Clinicians are increasingly placing thoracic endografts for 'off-label' indications such as traumatic aortic rupture in an effort to provide a less invasive and more effective treatment for these seriously injured poly-trauma patients. Chapter 8 is a systematic analysis of anatomic factors which may predict the rare, potentially devastating complication of thoracic endoprosthesis collapse. Based in part on dynamic CT imaging of thoracic endoprosthesis collapse outlined in Chapter 8, an examination of normal descending aortic pulsatility was undertaken. The results are presented in Chapter 9 and provide insight into the local environment into which these thoracic stent-grafts are being placed. Chapter 10 provides a summary of the most important findings