Evaluation of the Safety and Efficacy of the Multilayer Stent

Evaluation of the Multilayer Flow Modulator (MFM) for Endovascular Thoracoabdominal Aneurysm Repair. The objectives of the study is to determine the efficacy, safety and performance of the MFM and its delivery system in patients at high surgical risk presenting with a type II, III thoracoabdominal aneurysm, below the left subclavian and above the iliac bifurcation, according to the Crawford classification.

Conventional treatments of thoracoabdominal aneurysm are medical treatments (based on hypertension control) on one hand and surgical treatment on the other hand. The standard treatment is surgery consisting of an exclusion of the aneurysm with restoration of continuity by means of a prosthesis usually made of Dacron. * The rates of surgical morbidity and mortality differ according to whether the patient is treated electively or in an emergency setting. The most feared complication is spinal cord ischemia inducing paraplegia. * In elective surgery, operative mortality is estimated to be between 6% and 15% depending on the series, and around 50% to 60% of patients are treated in an emergency setting. The rate of neurological complications such as paraparesis or paraplegia is estimated to be between 3% and 15%. * In addition to the above, the following major complications have been shown to have an impact on the morbidity of this major surgery (5% each): * Bleeding requiring surgical hemostasis * Respiratory distress syndrome requiring prolonged ventilation support * Acute renal failure * Infections * Central neurological events (stroke and coma) * Peripheral neurological events (sensory-motor deficits, paraparesis, paraplegia) Analyses identify risk factors increasing the morbidity and mortality: * Patients over 80 years * Chronic obstructive pulmonary disease * Renal failure * Coronary artery disease * Comorbidities (malignancy, etc.) Compared to surgery, endovascular stenting reduces: * Pulmonary morbidity (suppression of thoracotomy and ventilation), in patients with impaired lung function; * Renal dysfunction; * Myocardial failure; * Risk of spinal cord ischemia and paraplegia. However, this treatment has a number of limitations * Availability of device in case of emergency * Topography of the neck must be far enough from the left subclavian artery to allow satisfactory fixation of the stent and exclusion of the lesion; * Obstruction of the branches near the aneurysm. In the current available treatment for this pathology, there are still some disadvantages such as the difficulty of precise positioning of the prosthesis and its branches which must cover the aneurysm tissue without endoleaks. Each lesion having anatomical specificities, the device must be designed for each individual patient, and the operator's technical ability must be extreme. So, the current technique is difficult to reproduce, and any emergency treatment is impossible. The multilayer flow modulator (non-covered) is the device used in this trial The complications mentioned above are inherent in the concept of covered stent treatment plus endoleaks that continues to fuel the aneurismal sac untreated, thus subject to the persistent risk of rupture. With this technique, the visceral arteries are occluded or have a retrograde flow (which pressurizes the aneurysm again). The multilayer flow modulator (non-covered) treatment approach avoids the major problems mentioned above: * It allows the aneurismal sac to thrombose whilst maintaining the patency of collateral branches arising from the aneurysm; * It improves the flow in the collateral branches, which becomes laminar flow through a mechanism of hemodynamic pressure drop from layer to layer and an increase in speed by rolling; * Deployment is easier and it is not different from peripheral stent deployment; * The device is available in all sizes and all lengths that can be stored, allowing the management of emergencies. The space-age 3D geometrical design of a Cardiatis multilayer flow modulator modifies flow within the aorta in a way that reduces pressure within the aneurysm thus collapsing the aneurismal sac while preserving any vital collateral circulation.