- Konstantinos P. Donas
- Giovanni Torsello
Use of endovascular techniques in the treatment of abdominal aortic aneurysms (AAAs) was revolutionary. Less invasive approaches and improved endovascular equipment led to expanded treatment of AAAs in technically demanding anatomies. At the same time, however, late complications such as type I endoleaks have increasingly occurred.
A primary reason for type Ia endoleaks after endovascular aneurysm repair (EVAR) is an undersized, previously deployed endograft, with insufficient apposition and fixation with the aortic wall. In this case, optimization of the fixation with EndonAchors or balloon-expandable stents, or administration of fluid agents in the gap between the device and the aortic wall, should be considered. EndoAnchors (Aptus Endosystems, Sunnyvale, California) or Palmaz bare-metal stents (Cordis, Fremont, California) can be an option only in the case of neck enlargement without significant migration of the previous endograft. The Aneurysm Treatment using the Heli-FX Aortic Securement System Global Registry (ANCHOR) demonstrated high technical success of 95% in 319 patients, but also 9.1% residual type Ia endoleak at the end of the procedure.
Regarding the use of Palmaz stents, a retrospective review from the Cleveland Clinic (Ohio, USA) showed primary reported technical success of 100%. However, in 35% of the treated cases, the authors observed midterm loss of the proximal seal zone and adaptation of the Palmaz stent with the aortic stent-graft and wall. Major limitations of the Palmaz stents are the rigidity and inability of the device to follow the natural neck enlargement, which can lead to new type Ia endoleak.
A common reason for the majority of the migrated endografts is severe aortic neck angulation, which provokes stent-graft migration and partial occlusion of the origin of the renal arteries from the struts of the suprarenal bare-metal stent. In this particular case, creation of new sealing zone is the recommended approach. This can be accomplished by using fenestrated endografts.
Katsargyris et al. reported one of the largest series in the literature regarding treatment of 26 patients by fenestrated EVAR. The authors confirm the technical difficulty of catheterizing the renal ostia through the fenestrations in 23.1% of the treated cases, with the struts of the suprarenal stent between the target vessels and the fenestrations. In addition, in five patients (19.2%), iliac access through the previous stent graft was tedious and caused some dislodgment of the preexisting stent-graft and alterations in the available working length. In agreement with the Nurnberg experience, the Cleveland Clinic reported that branched and fenestrated repair after failed EVAR is more complex than repair in the native aorta.
In contrast to fenestrated endografts, use of parallel grafts has some clear advantages. First, using off-the-shelf devices permits immediate treatment without delay. This is important for these rupture-threatening pathologic processes; in the experience of our cohort, the median aortic diameter of the treated cases was 7.1 cm.
From a technical point of view, catheterization from the upper extremity in a normally downward-oriented target vessel is easier and feasible. In addition, use of Endurant tubes with the short, M-shaped stents allows harmonic adaptability of the device in angulated necks, leading to successful exclusion of the pathologic process. At the same time, the low-profile introducer system allows trackability of severe iliac calcifications and angulations. Finally, placement of the abdominal device by chimney-graft EVAR follows insertion and positioning of the sheaths in the target vessels. In the event of unsuccessful catheterization of the target vessels, interruption of the intervention is always possible. In contrast, inability to catheterize the target vessels through the fenestrations after placement of a fenestrated endograft will lead to surgical conversion and explantation of the fenestrated endograft. This may be associated with a high-risk patient who is unfit for open repair, with profound clinical complications.
On the other hand, a major issue with the chimney technique remains the ideal combination of chimney and abdominal grafts to minimize the risk for persistent gutters. Based on our advanced experience with parallel and fenestrated grafts, use of balloon-expandable covered stents in the renovisceral target vessels has clear benefits regarding fluoroscopic visibility, precise positioning, and radial force.
In one patient, we observed a contained rupture caused by gutter-associated endoleak, demonstrating the substantial need for meticulous follow-up. The patient was treated successfully by endovascular means, with no need for surgical conversion. In this case we used a sandwich configuration with a migrated Zenith device, the periscope Viabahn graft from transfemoral access because of inability to catheterize the left renal artery from the upper extremity, and finally Endurant tubes from outward to inward. One possible explanation of the persistent and unplanned created gutters is the inappropriate interaction of the flexible Viabahn periscope graft with the rigid, stainless steel endoskeleton of the Zenith device.
Fig. 18.1 presents the treatment algorithm of type Ia endoleaks after EVAR based on the causative mechanisms. Clinical data are needed to establish the presented approach.
