Hooks, Hypermagnets and Adjustable Deployment:  The Early Canadian Experience with the Anaconda™ Endovascular Stent Graft for Infrarenal Aortic Aneurysm Repair.

RD Moore MD MSC FRCSC, †Claudio Cinà MD MSC FRCSC, Wesam Abuznadah MD MEd, Mona Motamedi BA(Hons)
Divisions of Vascular Surgery, University of Calgary, Calgary Alberta, 
†McMaster University, Hamilton, Ontario, Canada.

Purpose: To describe the early Canadian experience with a novel Health Canada approved Anaconda™ endovascular stent graft for the treatment of infrarenal aortic aneurysms.

Background:  Despite technologic advances in modular endovascular stent graft design, challenges during deployment are predictably related to access tortuousity and stenosis, marginal landing zone quality and length, errors in pre-operative length measurements due to difficulties in predicting graft behaviour in vivo, and errors related to the often dynamic nature of the deployment process, which can result in mal-positioning of the stent graft.  In addition, the duration of the endovascular procedure can be significantly affected by difficulties with contra-lateral limb access, particularly if advanced techniques (e.g. “up and over wire”) are required.  We describe the use of a newly approved device that has unique features related to graft design and deployment that address many of these device-related issues, leading to potential improvements in EVAR.  

Study Design: Prospective cohort study of patients treated in a tertiary vascular center by surgeons experienced in endovascular repair. Standard clinical endovascular inclusion/exclusion criteria were used and anatomically, aneurysms with severe angulation of iliac access vessels and/or the aortic neck were included.
Methods:  Between January and March 2007, 16 male patients (mean age 73.6 ± 5.05 years, ASA status II N=4, ASA III N=11, ASA IV, N=1) with infrarenal AAA (mean diameter 5.68 ± 0.66cm, mean neck length 33.19 ± 11.62mm, mean neck angulation 33.25 ± 43.86 degrees, mean maximal iliac angulation 72.63 ±40.87 degrees ) had elective (N=11) or urgent (N=5) EVAR with the Anaconda device using the IFU protocols established for deployment.  Procedures were completed in the operating room under either local or general anesthesia with a mobile C-arm unit and fluoroscopic table. Patients were assessed for endoleak or graft complications with 64 slice spiral CT imaging within a week of surgery, and then at 3 months, with further planned follow-up at 6 month intervals.

Results:  Mean values were derived for operative time (141.38±46 minutes), fluoroscopy time(16.76±9.35 minutes), intra-operative dye load (132.31±68.72 mls), and blood loss (396.15±279.48 mls). Primary adjunctive procedures were required in 5 patients (31%) and included internal iliac embolization in 3 patients, limb extension and external iliac angioplasty in one patient, and internal/external iliac “kissing balloon” angioplasty in one patient.  Median LOS was 6.68 days (Range: 1-23 days), with one patient requiring an ICU stay of two days due to cardio-pulmonary complications. No peri-operative or late deaths were observed. Secondary interventions were required in 3 patients (18%). Two patients with marginally acceptable iliac access vessels (7mm diameter) developed limb ischemia post-operatively. One of these patients had acute iliac occlusion pre-operatively, and suffered ipsilateral graft limb thrombosis requiring cross femoral bypass. This patient also had a Type 1A endoleak requiring laparotomy and aortic cerclage. The second patient with limb ischemia had an iliac dissection requiring palmaz stent placement. The only patient with a Type 2 endoleak had immediate post-operative coil embolization due to the development of atrial fibrillation and the need for full-dose anti-coagulation. Common femoral artery dissection related to the “square-faced” profile of back of the delivery nose cone was observed in one patient and required suture repair.  Another patient had rupture of the delivery handle during attempted deployment, and was successfully converted using a different endograft and represented the only “intention to treat” failure.
 
Conclusions: The improvements in contra-lateral access, the proximal hook fixation, and the specific deployment features of the Anaconda™ endovascular device allowed for successful initial EVAR exclusion of infrarenal aortic aneurysms with high risk anatomy in 94% of patients. The short nose cone, and the sheath which has a tendency to kink and is not well tapered over the cone nose, poses challenges with calcified vessels and tortuous anatomy. Care must be observed during deployment to ensure that the device main body is rotated and canted with the fixation hooks perpendicular to the long axis of the neck in order to achieve stable endoseal. Modifications to the nose cone and of the delivery sheath will enhance the performance of this endovascular system. Ongoing follow-up and larger series are required to assess mid-term and long term EVAR performance.