Dynamics of Endovascular Aneurysm Repair.

Endovascular aneurysm repair (EVAR) was in 1996 started at the St. Antonius Hospital, Nieuwegein, The Netherlands, with use of the AneuRx stent-graft system (Medtronic AVE, Santa Rosa, CA, USA). All data were captured prospectively in a vascular database. In Chapter 2 a general overview of recent literature of EVAR is evaluated. Chapter 3 contains mid-term single-center results with the AneuRx device in the first 77 patients with a minimum follow-up of 12 months. In Chapter 4, the application of EVAR to repair paraanastomotic aneurysms (PAA's) is described. In our series of 14 patients, PAA's were successfully excluded with EVAR without perioperative mortality and with morbidity in one patient. Median follow-up was 12 months. In patients who were treated with bifurcated stent-grafts, no conversions were performed, and a secondary intervention was necessary in one patient. Reconstructions of proximal aortic anastomotic aneurysms with endovascular tube grafts were not durable, however. In Chapter 5, stent-graft explantation is discussed. In our series of 355 patients treated with stent-grafts, late conversion rate was 3.1%. Mortality rate for acute conversions was 50%. Of the six patients who needed elective conversion, mortality rate was 0% and morbidity rate was 67%; These results advocate timely explantation if EVAR-related problems occur cannot be solved with endovascular techniques. Chapter 6 focuses on the long-term single-center results with the AneuRx device which was used in 212 patients. Perioperative mortality rate was 2.4 %. Freedom from secondary interventions was 48% at 9 years. The aneurysm-related death rate was relatively small, with an annual risk of about 1%. Most secondary interventions were needed for fixation-related problems in the proximal aortic anchoring zone. Therefor we decided to start dynamic studies on the area of the proximal aortic neck by means of dynamic magnetic resonance angiography (MRA). Chapter 7 describes a study on dynamics of the proximal anchoring zone studied with dynamic MRA before and after EVAR in 11 patients. Preoperatively, mean diameter changes at each level were about 8%. These diameter changes differed between patients and even within each patient they varied over the studied axes. Pulsatility of the aneurysm neck appeared not to be influenced by stent-graft placement. In Chapter 8, wall stiffness of the aneurysm neck and the aneurysm sac were studied with dynamic MRA, before and after stent-graft placement in 11 patients. We measured an increased stiffness at the level of the aneurysm sac after EVAR Neither EVAR nor endoleaks resulted in changes of stiffness within the aneurysm neck. Stent-graft design did influence compliance at the level of the neck. Conclusion This thesis has shown acceptable results during mid-term and long-term follow-up for patients with severe comorbidities. Proximal fixation of the stent-graft was identified as the Achilles' heel of EVAR and therefore should be of major interest for further investigation and improvement. We presented new information on dynamic features of the aneurysm neck before and after stent-graft placement. This information gains insight into a whole new area for further studies and will have its effects on inclusion criteria and stent-graft designs.