Endovascular treatment of complex abdominal aortic aneurysms by combining different types of endoprostheses

Introduction

Endovascular aneurysm repair (EVAR) is the treatment of choice for most patients suffering from an aneurysm of the abdominal aorta (AAA).^1,2 The principal advantages of EVAR over open surgery are associated with the minimal invasive aspect of the procedure, which leads to reduced early morbidity and mortality.^3,4 The limitations of EVAR compared to open surgery are mainly expressed in terms of reduced flexibility in adaptation to unfavorable anatomy and, consequently, a reduced durability.^5,6 Unfavorable or hostile aortic anatomy is predominantly caused by variations in the shape of the aortic neck, which do not meet the criteria for instruction for use of the commercially available endografts. These aspects include short neck length (<1 cm), large diameter (>28 mm), severe infrarenal angulation (>75°), and abundant mural thrombus or calcium.^5,7,8

Recently, data was published from the ANCHOR registry, a patient cohort with a high prevalence of challenging aortic anatomy and failure of sealing. ⁹ It was shown that increased infrarenal aortic diameter (>26 mm at the lowest renal artery) and a conical neck configuration were risk factors for type 1A endoleaks.

Endovascular therapy by using chimney/snorkel or fenestrated endografts may be a good alternative endovascular treatment option; however, the reintervention rate is substantial, there is a need for stents into the visceral arteries, and it is relatively more expensive. ¹⁰ Also, these treatment options have their limitations with respect to renal artery diameters and severe neck angulation. Another limitation of EVAR is a small diameter distal aorta (<20 mm). The use of most of the commercially available modular endoprostheses in these challenging accesses will lead to increased risk of obstruction of the competing limbs. Use of unilateral devices may be an option in these patients, but do need an additional femoral–femoral crossover bypass.

In order to be able to treat AAA patients with a large aortic neck and/or small aortic bifurcation, and unfit or unwilling to undergo open surgery, we chose to combine the AFX endoprosthesis (Endologix Inc., Irvine, CA, USA) topped with the Valiant Captiva endograft (Medtronic, Minneapolis, MN, USA).

Methods

Between 2013 and 2015 five patients were treated with the AFX stent graft combined with the Valiant Captiva stent graft as proximal extension. When indicated the Heli-FX Aortic Securement system (Medtronic, Minneapolis, MN, USA) was used to increase migration resistance.

All patients had an infrarenal aortic aneurysm with indication for treatment and underwent pre-operative computed tomography angiography (CTA) imaging studies. Post-processing and stentgraft planning was performed with 3-Mensio Vascular software (Pie Medical Imaging, Maastricht, The Netherlands). The selected patients were unwilling or unfit to undergo open surgery and fell outside instructions for use criteria for the currently commercially available endografts, due to the diameter (>31 mm), or angulation of the infrarenal neck, and/or a small distal aorta (≤20 mm). Chimney/snorkel or fenestrated endografts in these cases were also not feasible for anatomical (small renal artery diameter) or logistic reasons (symptomatic patients).

Follow-up consisted of a CTA 1 month post-operatively, followed by yearly CTA or duplex ultrasound. All patients had a minimum follow-up of 6 months.

Results

All five patients were male (age 62–76 years), had a mean AAA diameter of 62 mm and were treated for a nonruptured AAA. Comorbidity scores ranged 2–4, following the Charlson Comorbidity Index. All patients were considered to have a hostile aortic neck due to diameter, angulation or shape, which is shown in Table 1. Patient no. 5 suffered from a conical infrarenal neck (24 mm diameter at the level of the lowest renal artery and 30 mm, 1 cm below the renal artery) in combination with small aortic bifurcation (18 mm).

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Table 1.

Patient characteristics.

Patient no.	Age	Comorbidity	CCI	Aneurysm diameter (mm)	Infrarenal diameter (mm)	Neck length (mm)	Neck shape	Neck thrombus present	Neck angulation (degrees)	Bifurcation diameter (mm)
1	65	CHD, MVI, PVD	2	62	32	20	conical	+	44	37
2	62	MI, DM, CHD, PVD	4	79	36	20	straight	−	45	35
3	76	KI, COPD, PVD	4	61	35	20	straight	+	55	17
4	75	MI, PVD	2	57	26	20	sigma	−	91	20
5	76	MI, PVD	2	65	24	15	conical	+	82	18

The procedure is illustrated in Figure 1(a) to (g) showing case no. 2 as an example. Two AFX limbs needed distal extension with a Smart stent (Cordis, Johnson and Johnson, NJ, USA) due to pre-existent iliac artery stenosis (Table 2). In two patients, prophylactic endoanchors were used to increase the proximal migration resistance. In one patient (no. 4), endoanchors in combination with a giant Andras bare metal stent (Andramed, Reutlingen, Germany) were deployed to treat an acute type 1A endoleak, which was done successfully. OPEN IN VIEWER

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Table 2.

Intervention.

Patient no.	Procedure date	AFX	Valiant Captiva	Additional	Endoanchors	Endoleak at procedure	Intervention
1	29-10-2013	BA28-100/l16-40	VAMF4040C100TE		+	−	−
2	02-02-2015	BA28-100/l20-40	VAMF4040C100TE	Left extension Smart stent 9×40	+	−	−
3	10-04-2015	BA28-100/l16-40	VAMF4040C100TE	Right extension Smart stent 9×60	−	−	−
4	01-05-2015	BA28-100/l16-40	VAMF3434C100TE		−	+	Endo anchors, Andras stent, small type 1A endoleak accepted
5	07-08-2015	BA28-80/l16-40	VAMF3434C100TE		−	+	Cuff Endurant ETTF2828C70EE

Follow-up ranged from 228 to 875 days (Table 3). A contrast CTA was made 4 to 6 weeks after the initial procedure, and no type I or III endoleaks were seen. One patient (no. 1) was successfully treated for a type 1A and 1B endoleak 490 days after the index procedure, by deploying a proximal Valiant extension with endoanchors and by two distal extensions (Table 3). In retrospect, 4 of 6 primary deployed endoanchors had not penetrated the aortic wall due to significant thrombus load (>2 mm thickness) in the infrarenal neck. Type IB endoleak was due to progressive dilatation of the native common iliac artery.

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Table 3.

Follow-up.

Patient no.	Follow-up (days)	Endoleak (type)	Days to endoleak diagnosis	Revision type	Endoleak
1	875	+ (1A, 1B)	446	VAMF4040C100TE proximal cuff, endoanchors, embolization internal iliac artery, bilateral distal extension	–
2	413	–
3	347	–
4	326	–
5	228	–

Discussion

Treatment of AAAs by EVAR has become the preferred method in the majority of patients. ¹¹ However, a considerable part (20%) of patients presenting with an AAA do not have a favorable anatomy according to the instructions for use of the commercially available endografts. ¹² For instance, the maximum proximal diameter of currently available endoprostheses is 36 mm (Zenith (Cook Medical Inc., Bloomington, USA) Endurant II (Medtronic, MN, USA)), 34 mm (AFX), or 31 mm (Anaconda, Terumo, Renfrewshire, Scotland). Taking into account that a ∼20% oversizing is required for adequate long-term sealing, treatment of aortic necks >29–30 mm are outside instructions for use.

What treatment can we offer patients unwilling or unfit to undergo open aortic surgery, with larger infrarenal aortic necks?

FEVAR does have the limitations of relative high costs, and the need for a manufacturing period of 6–8 weeks in case of a custom-made device. The use of chimney grafts has been advocated recently, but robust longer term follow-up is lacking. ¹³ Both options are limited by the use of stents in visceral arteries, a required minimum diameter of the visceral arteries to avoid early obstructions, and require an experienced endovascular team with advanced equipment and substantial radiation exposure for the patient and physicians.

Moreover, a diameter <20 mm of the distal aorta is a limiting factor for modular devices with increased risk of obstructions of the limbs. The advantage of the AFX endograft is its anatomical fixation at the aortic bifurcation. There are no competing limbs in the distal aorta and risk of obstruction is minimized. The endograft acts like a pillar and allows the use of a proximal, larger diameter tube endograft for sealing in the aortic neck. This additional tube endograft is of course not limited to the Captiva Valiant.

A few important technical considerations should be taken into account. To avoid a late type IIIa endoleak, overlap between the AFX unibody and proximal component should be at least 4 cm. ¹⁴ Also, when two proximal components are needed due to a long distance between the renal arteries and the aortic bifurcation, the increase in diameters of these components should be as gradual as possible. Therefore, we advise to always choose the largest possible diameter of the AFX unibody, which is 28 mm. Moreover, the stents and fabric of the proximal component must have enough space to completely unfold. Therefore, it is important that the distance between the top of the AFX unibody and the lowest renal artery is at least 4 cm.

Prophylactic use of endoanchors is best planned on the pre-EVAR CT scan to avoid positioning in thrombus or mural calcium. The endoanchors should be evenly spaced along the circumference of the endograft and at least six endoanchors must be used in endografts >28 mm in diameter.

The currently described strategy is applicable to patients who are unsuitable for chimney/snorkel or fenestrated EVAR, and unfit or unwilling to undergo open surgery. Moreover, it is an off-the-shelf solution, and less expensive in contrast to the tailor-made endografts.

However, one can criticize the quality of the used proximal landing zones in this case series. An infrarenal neck diameter >30 mm may be prone to progressive dilatation during follow-up. We have limited the current technique to neck diameters with a maximum of 35 mm, and do not advocate sealing in larger diameter necks.

Limitations of these case series are the limited number of patients and the lack of long-term follow-up. Moreover, the combination of the AFX endograft and Valiant Captiva endograft is off-label use.

Although the currently described combination of endografts for treatment of challenging aortic aneurysm anatomy is feasible and noncomplex, it should be reserved for selected patients without other treatment options.