Safety and Efficacy of Multiple Overlapping Uncovered Stents for Pararenal Aortic Aneurysm Repair

Complex aortic aneurysms involving major branches have been difficult endovascularly. The primary purposes of this study is to evaluate the safety, feasibility, and efficacy of multiple overlapping uncovered stents in treating aortic aneurysm while preserving major visceral branches, including the celiac artery (CA), superior mesenteric artery (SMA) and renal artery (RA).

The traditional endovascular treatment of aneurysms is based on the utilization of stent-grafts that create a mechanical barrier between the aneurysmal sac and normal blood flow. Problems such as endoleak and occlusion of collateral arteries impede its application in complex aneurysms adjacent to or involving vital branches. Advanced branched/fenestrated endografts have been applied in many experienced centers, but the application of these techniques is limited in less-experienced centers due to the complicated and cumbersome nature of these procedures.

The concept of using bare metal stents to occlude aneurysms was firstly described about two decades ago. Geremia et al suggested that a metallic stent bridging a saccular aneurysm would alter the local flow pattern, promoting thrombus formation, thereby leading to aneurysm occlusion. Optimal flow modulation effect is reached with a mean stent porosity of 65%. To achieve such low mesh porosity while maintaining the flexibility of the stent, the investigators applied multiple stents in an overlapping fashion. Computational simulation in this study has demonstrated that with 3 or 4 bare metal stents deployed, the mesh porosity could be decreased to an effective value, slowing flow velocity within the sac. The use of overlapping stents has been reported in the treatment of peripheral aneurysms with satisfactory clinical outcome.

The primary purposes of this study is to evaluate the safety, feasibility, and efficacy of multiple overlapping uncovered stents in treating aortic aneurysm while preserving major visceral branches, including the celiac artery (CA), superior mesenteric artery (SMA) and renal artery (RA).

Eligibility Criteria:
Inclusion Criteria:

* Age\>18 years
* Life expectancy ≥ 12 months
* The patient or his legal representative has signed the informed consent form
* Contraindicated for open surgery, declared inoperable by surgeon and anesthetist (statement signed by each doctor) and must have at least one of the following:

  1. Age\>80 years
  2. ASA ≥3
  3. history of thoracic surgery or surgery of abdominal aorta
  4. coronary artery disease (history of angina myocardial infarction) with positive functional testing and coronary lesions for which revascularization is impossible or not indicated
  5. heart failure
  6. LVEF \< 40%
  7. chronic respiratory failure defined by one of the following criteria:

     1. FEV1 \<1.2 L/sec;
     2. VC \<50% of the predicted value according to age, sex and weight;
     3. Arterial blood gas analysis in the absence of oxygen: PaCO2\>45 mmHg or PaO2 \< 60 mmHg;
     4. Oxygen therapy.
  8. renal insufficiency if creatininaemia\> 200 micromol/L before injection of contrast product;
  9. hostile abdomen, including presence of ascites or other signs of portal hypertension;
  10. obesity.
* Conventional tubular stent-graft is not suitable due to complicated aneurysm anatomy, such as being adjacent to (proximal or distal landing zone \< 15mm) or involving vital branches, including the celiac artery, superior mesenteric artery, or renal artery.
* Adequate arterial anatomy of aneurismal lesion access.

Exclusion Criteria:

* Medical contraindications to a local or general anesthesia and angiography;
* Life expectancy less than one year, or clinical follow-up impossible;
* Congenital disorders of blood coagulation;
* Intercurrent infection;
* Allergy to aspirin, clopidogrel, or contrast agents;
* Patient (s) included in another clinical study;
* Patient pregnant or breastfeeding.