Clinical Aspects on Chimney Stent Graft Technique in Endovascular Repair of the Aorta.

Introduction: Open repair of the aorta carries a high risk for morbidity and mortality especially in the elderly population and in patients unfit for major surgery. Endovascular aortic repair is safe, durable and effective when there is adequate proximal and distal sealing zone for the aortic stent graft. Fenestrated and branched stent grafts have made the repair possible for complex but elective cases that do not have an adequate sealing zone. Urgent complex cases and patients with midaortic occlusive diseases do not have any therapeutic alternative if they are not fit for open repair. Chimney graft technique fills this gap and allows the sealing zones for aortic stent graft to be extended as required. The aim of the present thesis is to study the applicability, safety and durability of CG technique in urgent cases with complex lesions in the thoracic and abdominal aorta including the midaortic occlusive diseases. Patients and Methods: All patients who received CG were treated urgently or semi-urgently. The majority of the treated aortic lesions were aneurysms, dissections, pseudoaneurysms, infection, and accidental overstented vital aortic side branches. The median age of all patients was 75 years (IQR, 69-78), of them 32% were female except for the first study where all ten patients were female with midaortic occlusive diseases. The second study evaluated the mid to long-term efficacy and durability of the CG technique in 29 patients with urgent and complex lesions of the thoracic aorta. The third study examined the long-term results of CG in preserving the visceral flow of 51 patients with urgent complex aortic lesions. The fourth study evaluated the CTA images of 206 patients with ruptured abdominal aortic aneurysm. The study measured the applicability of CG in patients for whom standard EVAR was contraindicated because of a short aneurysmal neck. Results: The results showed that CG is applicable and safe for midaortic occlusive diseases with high technical success and patency rate without major adverse effect. The treated patients with thoracic aortic lesions had 14% 30-day mortality, 21% type I endoleak, 7% CG-related mortality, 98% secondary patency and 68% of the aortic lesions shrank significantly. Visceral CG had a 10% 30-day mortality, 6% CG-related mortality, 12% type I endoleak, 93% secondary patency and 63% of the aortic lesions shrank significantly. Twenty-two patients had one renal arteriy sacrificed, 57% of these required permanent renal dialysis. The fourth study proved that CG technique increased the overall suitability for endovascular repair from 34% to 40-46%. Conclusions: Chimney graft seems effective and safe for treating midaortic occlusive diseases in patients unfit for open surgery. The early and mid to long-term results of the CG technique for urgent and complex lesions of the thoracic and abdominal aorta in high-risk patients are promising with a low early mortality, acceptable rate of type I endoleaks and long durability of the CGs, which may justify a broader applicability of this technique. Most endoleaks could be sealed endovascularly. However, sacrificing a kidney in such elderly population was associated with permanent dialysis in 55% of patients and should be avoided whenever possible. CGs in one or both renal arteries may increase overall suitability of rAAA for EVAR by 6-12%. Key words: Chimney stent graft, snorkel technique, endovascular aortic repair, thoracic endovascular aortic repair, endoleak, patency, rupture, urgent, stent graft, aorta, computed tomography, ultrasound, stenosis, EVAR, TEVAR