Management of a Type Ia Endoleak With the Nellix Endovascular Aneurysm Sealing System

Case Report

An 87-year-old man presented to our unit with an asymptomatic 7.6-cm infrarenal AAA (Figure 1A) and a 4.5-cm right internal iliac artery aneurysm. He underwent embolization of the right internal iliac artery followed by EVAR (Figure 1B) using an aortouni-iliac device (Zenith ZAUI-36-161-ZT; William A. Cook Australia, Brisbane, Queensland, Australia) with a 13-mm limb extension to the right external iliac artery (EIA) due to a tortuous left common iliac artery (CIA). The left CIA was occluded using an Amplatzer Vascular Plug (St. Jude Medical, St. Paul, MN, USA), ⁵ and a right-to-left femorofemoral crossover bypass was performed with an unsupported 8-mm Dacron graft.

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Figure 1.

(A) Preoperative computed tomographic angiogram (CTA). (B) CTA after endovascular aneurysm repair (EVAR). CTA (C) and digital subtraction angiogram (D) 24 months after EVAR showing type Ia endoleak. Nellix endovascular aneurysm sealing (EVAS) and bilateral renal chimney grafts prior to (E) and after (F) deployment. (G) CTA 2 days after Nellix EVAS with bilateral renal chimney grafts. (H) CTA at 6 months demonstrating continued successful resolution of the type Ia endoleak.

Routine duplex ultrasonography surveillance was unremarkable at 3, 6, and 12 months with a stable sac size; however, 24 months after the index EVAR, an asymptomatic type Ia endoleak was detected. Following ultrasound assessment, the endoleak was confirmed on arterial-phase computed tomographic angiography (CTA) of the aorta (Figure 1C). The CTA demonstrated evidence of significant sac size enlargement compared with the preprocedure CTA, and it showed device migration. Expedited intervention, within days, was deemed necessary to treat this complication and prevent aneurysm rupture.

Digital subtraction angiography of the aorta was performed through a 6-F arterial sheath. Aortography (Figure 1D) confirmed the presence of a type Ia endoleak with ~15 mm between the renal arteries and the proximal end of the endograft material. The endograft seal was extended proximally by 2 aortic cuff devices (Zenith Renu; Cook Medical, Bloomington, IN, USA). The size of the endoleak was reduced by this procedure, but it persisted postoperatively; the leak remained unsuitable for Onyx or coil embolization.

Clinical review suggested that the patient was not a candidate for graft explantation or fenestrated repair as his right CIA was very long, tortuous, and stented previously. The patient had a significant cardiac history, including a myocardial infarction, coronary artery bypass grafting, and severely impaired left ventricular function (ejection fraction 20%−25%); because of his American Society of Anesthesiologists class 4 status, it was deemed unsafe to perform complex open aortic surgery.

The treatment options were discussed with the patient, and he gave informed consent for the off-label use of a Nellix (EVAS) device. He was also apprised of the possibility of using chimney grafts to increase the proximal sealing zone above his existing stent-graft in an attempt to seal the endoleak.

Under general anesthesia, the right superficial femoral artery (SFA) distal to the crossover graft was used for arterial access. The left axillary artery was exposed and cannulated with a 7-F sheath. Through the axillary approach, both renal arteries were cannulated; balloon-expandable covered stents (Atrium Advanta V12; Maquet Getinge Group, Rastatt, Germany) were deployed (7-×38-mm on the left and 6-×38-mm on the right) with the proximal stents just distal to the origin of the superior mesenteric artery (SMA).

A single 180-mm Nellix device was inserted through the right SFA and advanced over a wire into a position parallel with the renal ostia at the lower border of the SMA. The endobag was inflated with an aqueous polyethylene glycol–based polymer after first conducting a saline “pre-fill” stage to define the required polymer volume. During balloon expansion of the Nellix device and all stages of subsequent polymer injection, the chimney stent-grafts were supported by continuously inflated balloons (Figure 1E). Completion angiography demonstrated successful resolution of the type Ia endoleak with bilaterally patent chimney stent-grafts (Figure 1F).

The patient recovered uneventfully, with serial biochemical testing demonstrating normal postoperative renal function (eGFR >60 mL/min/1.73 m²). CTA 48 hours (Figure 1G) and 19 days postoperatively demonstrated successful resolution of the endoleak and continuing patency of both renal artery chimney stent-grafts. CTA at 6 months (Figure 1H) confirmed persistent sealing of the endoleak.

Discussion

Partial or total endograft explantation combined with conventional open repair remains an option for patients with a persistent type Ia endoleak that is not amenable to endovascular therapy (including branched or fenestrated solutions). ⁶ A significant proportion of patients with this pathology will be considered unsuitable for open repair due to cardiovascular risk factors or other comorbidity.

Previous case reports^7,8 and experimental studies ⁹ have demonstrated the utility of the novel EVAS technology alongside chimney stents in the management of juxtarenal aneurysms. The present case illustrates that EVAS can provide an alternative treatment option for the salvage of failing endografts. Although a single Nellix device was employed in this case, when revising a bifurcated endograft, it may be technically easier to use bilateral endovascular sealing devices compared to a fenestrated cuff or another bifurcated graft, as the Nellix is not dependent on the distance from the renal artery to the flow divider.

The chimney technique has been widely utilized as an adjunct to conventional endografts for the treatment of pararenal aneurysms where open surgery or fenestrated/branched technology is not feasible.^10–14 A disadvantage of the chimney technique with standard endografts relates to the formation of “gutters” between the main endograft body and the aneurysm wall created by the chimney devices. ¹⁵ These gutters are a potential source of persistent type Ia endoleak. An attractive aspect of the EVAS system is that the polymer-filled endobags are able to conform more precisely around adjunctive chimney stent-grafts, thus reducing the potential impact of the gutters.

Conclusion

A novel category of endovascular solutions can be added to the clinician’s repertoire for treating type Ia endoleak after conventional EVAR of infrarenal AAA. While the EVAS technique is feasible and the early results are encouraging, the durability of this method remains unknown. Greater experience with this device is required before its routine use can be recommended in the management of patients with complex endoleaks.