Commentary: Could the Chimney Technique Become the “Holy Grail” of Endovascular Treatment for Type Ia Endoleaks After EVAR?

After nearly 30 years,^1,2 endovascular aneurysm repair (EVAR) has evolved to take on the most challenging thoracic and abdominal aortic anatomies, often using devices outside their instructions for use to complete a successful repair. However, type I endoleaks, the “Achilles’ heel” of EVAR, still plague long-term durability. Short and severely angled aneurysm necks contribute to the development of late type Ia endoleaks, ³ which correlate with higher risk for late complications based on the EUROSTAR registry. ⁴ Additionally, the majority of the patients were unfit for open repair at the time of their EVAR procedure, and when a late complication such as type Ia endoleak occurs, the patients are older and likely in poorer general health, making any attempt to manage the endoleak by surgical correction inappropriate.

The article from Montelione et al ⁵ in this issue of the JEVT highlights the utility of the chimney endovascular technique to save failed EVARs. Implanting chimney/periscope grafts parallel and outside the main abdominal endograft can compensate for a short or otherwise inadequate sealing zone.^6–13 The Zurich colleagues have taken the next step with the chimney technique, presenting their 12-year experience using these parallel grafts in the treatment of 24 patients with type I endoleaks, moving the seal zone proximally (or distally) and maintaining side branch perfusion. The mean diameter of the aneurysm sacs was 88.3 mm, reflecting the need for urgent treatment due to the high risk for rupture. After a mean follow-up of almost 2 years, the 24 patients showed no aneurysm-related mortality, overall aneurysm sac reduction, and high target vessel patency.

In contrast to the Zurich experience and their use of 3 different abdominal stent-grafts, we prefer the standard combination of Endurant stent-grafts with balloon-expandable covered stents (BECS), which was shown to achieve narrow gutters and lower stent compression in an in vitro study by Mestres et al. ¹⁴ Use of BECS is associated with high fluoroscopic visibility and no tendency to dislocate during placement compared to the more flexible and less easily visualized Viabahn grafts.

Endovascular repair of type Ia endoleaks has to deal with several anatomic challenges. The majority of the patients suffer from large aneurysms (>6-cm diameter), often in combination with abdominal symptoms or rupture, requiring urgent treatment without delay. Migration of the stent-graft can partially occlude the origin of the renal arteries due to the struts of the suprarenal bare metal stent. Figure 1A presents this technically demanding situation involving a patient with type Ia endoleak and a 7.1-cm aneurysm sac 4 years after EVAR.

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Figure 1.

(A) Type Ia endoleak after endovascular aneurysm repair with a Talent endoprosthesis; the sac diameter measures 7.1 cm. Note that the suprarenal stent struts of the previously deployed endograft are at the origin of the high calcified right renal artery. (B) Successful treatment of the type Ia endoleak by placement of 2 Advanta V12 covered stents in the renal arteries and an Endurant tube in the abdominal stent-graft.

Treatment of type I endoleak/migration using fenestrated endografts may be associated with difficulty in catheterizing the renal origins through the fenestrations, which Katsargyris et al ¹⁵ documented. Advancement of a sheath or catheter through the fenestrations was tedious in 23.1% of the treated patients. ¹⁵ In agreement with this, the Cleveland Clinic reported that fenestrated repair after failed EVAR is more complex than repair in the native aorta. ¹⁶ In case of unsuccessful cannulation of the renal arteries, urgent conversion with explantation of the extant endograft would probably be necessary.

Contrariwise, for chimney EVAR the abdominal stent-grafts will be deployed after the sheaths are positioned in the target vessels. If catheterization of the target vessels is blocked by the struts of the previously deployed stent-graft system, the intervention can be stopped, avoiding an urgent surgical conversion. Normally, the downward orientation of the renal arteries facilitates cannulation of the target renal arteries from the upper extremity. After placement of the sheaths at least 2 cm into the renal arteries, deployment of flexible stent-grafts (Medtronic Cardiovascular, Santa Rosa, CA, USA) and subsequently of the chimney grafts creates a new, adequately long neck, sufficiently excluding the type Ia endoleak. Figure 1B shows the postoperative reconstruction of the computed tomographic angiogram with the successful use of 2 chimney grafts in the renal arteries parallel and outside of the Endurant tube graft; the type Ia endoleak was not present in imaging follow-up.

In conclusion, the chimney technique has clear clinical and technical advantages for the management of type Ia endoleaks. The promising experience in Zurich should be confirmed in other centers to demonstrate reproducibility of their good results and move toward establishing the chimney technique as the possible “holy grail” for the endovascular treatment of type I endoleaks and failed EVAR.