Introduction: Complex abdominal aortic aneurysms (CAA) are defined as abdominal aneurysms that are anatomically unsuitable for a standard endovascular repair because of a short infrarenal neck or no infrarenal neck. These CAAA are usually treated either by fenestrated endovascular aortic repair (FEVAR) or open repair (OR). Data comparing these thechniques remain scarce, mainly consisting of systematic reviews based on retrospective studies. Although mid-term and long-term results remain uncertain, FEVAR has gained widespread acceptance in the vascular community. However, this practice is not evidence base. Beyond clinical results, whether FEVAR is cost-effective or not is not demonstrated. A randomized controlled trial comparing FEVAR and OR is unlikely to be conducted since centers have developed specific expertise and practice, and most of surgeons are not keen to randomize patients. Thus, we believe that a prospective comparative multicentric cohort, with a propensity score and minimization of selection, classification and confusion bias is the most realistic way to provide reliable comparative data on cost effectiveness of FEVAR and OR. Overall, 382 patients are expected to be included (159 in each group).

Objective: The objective of this prospective non-randomized comparative multicenter cohort study is to compare the cost effectiveness incremental ratio at 36 months of FEVAR and OR for CAAA.

Method: Patients with CAAA discussed for FEVAR or OR in 37 french vascular centers in during a two years inclusion period constitute the population study. Preoperative and postoperative clinical and imaging data will are collected prospectively in eCRF forms. QOL before and after treatment is assessed by the E5D5L. The follow-up period is three years. The primary outcome is the Incremental cost-utility ratio (cost/QALY) at 36 months. We plan to minimize indication biases by using a proposensity score (proposnsity score maching and Inverse probablility of treatment weighting) based on clinical and anatomic characteristics. Patient at prohibitive risk for OR are excluded. Patient anatomically unsuitable for FEVAR are also excluded .

Conclusion: This study should provided valuable data on cost effectiveness of FEVAR for CAAA. Sub-goup analysis will be also conducted.

Inclusion Criteria:

1. Presence of an abdominal aortic aneurysm greater than 50 mm in diameter, anatomically unsuitable for a standard infrarenal stent graft because of an inadequate infrarenal neck and for which a treatment by FEVAR or OR is considered. The AAA can be identified as follows, according to preoperative imaging:

   • Short-neck or juxtarenal aneurysm: if treated by OR, would require an infrarenal proximal aortic suture, regardless of the level of clamping.
   • Suprarenal aneurysm: if treated by OR, would require a suprarenal/supramesenteric/ supraceliac aortic cross clamping, and a proximal bevelled suture and/or a separate revascularization of at least one renal artery.
   • Type IV thoracoabdominal aneurysm: aneurysm extending up to the level of the diaphragm pillars, requiring a supracoeliac clamping with a proximal bevelled suture and/or separate revascularization of at least one renal artery if treated by open surgery.

2. Patients aged 18 and over

3. Patient who expressed a non-opposition to participating in the study.

4. Patient affiliated to the French healyh care system

Exclusion Criteria:

1. Presence of a type I, II, III or V thoracoabdominal aneurysm according to the modified Crawford Classification.

2. Patients for whom an alternative surgical technique is being considered and listes below: laparoscopic aortic repair, hybrid repair, CHIMPS, surgeon modified stent grafting, in situ fenestrations.

3. Patients deemed at prohibitive risk for OR :

   • uncompensated cardiac failure with LVEF <40% (NYHA class III and IV)
   • Coronary revascularization < 1 month
   • Large myocardial ischemia >3 segments not revascularized or not revascularizable
   • Non-revascularized or non-revascularizable unstable angina
   • Non-operable tight aortic stenosis (mean gradient > 40 mmHg, valve area < 1 cm2, peak transvalvular velocity > 4 m/s)
   • Non operable significant mitral shrinkage (area <1.5cm²)
   • FEV1 < 50% of the theoretical value
   • Home oxygen therapy
   • Chronic renal failure with clearance < 30 ml/min

4. presence of a main renal artery less than 4 mm in diameter

5. Special anatomical configurations: horseshoe kidney, pelvic kidney.

6. Lesions of "shaggy" aorta at the visceral segment or at the lower thoracic aorta

7. History of abdominal aortic surgery (open or endovascular)

8. Dissecting, infected, ruptured or painful aneurysm

9. Life expectancy less than 2 years

10. Person under judicial protection

11. Person under tutorship or curatorship

12. Pregnant or breastfeeding woman

Patients with complex AAA (juxtarenal AAA, suprarenal AAA and type IV AAA) needing elective surgical repair (diameter < 50 mm) either by FEVAR or OR.

Patients at prohibitive risk for OR are excluded. Patients anatomically unsuitable for FEVAR are also excluded.