Operative and Midterm Outcomes of the Fenestrated Anaconda Stent-Graft in the Endovascular Treatment of Juxtarenal,Suprarenal,and Type IV Thoracoabdominal Aortic Aneurysms

Abstract

Purpose: To report operative and midterm outcomes of fenestrated endovascular aneurysm repair (FEVAR) with the Anaconda device. Methods: A retrospective analysis was conducted of 39 consecutive patients (median age 74 years; 36 men) treated with the fenestrated Anaconda stent-graft between July 2011 and December 2015 at a single center. Indications for FEVAR were abdominal aortic aneurysms (AAAs) with neck anatomy unsuitable for a standard stent-graft. Median infrarenal neck length was 4 mm (range 0–9). Four (10%) patients presented with type IV thoracoabdominal aortic aneurysm (TAAA), 12 (31%) with suprarenal aneurysms, and 23 (59%) with juxtarenal aneurysms. Four (10%) patients had previous infrarenal aortic repair. Five (13%) patients had an infrarenal neck angulation >60°. A total of 106 fenestrations were incorporated into the stent-grafts (73 renal arteries, 25 superior mesenteric arteries, and 8 celiac trunks). Technical success, perioperative and midterm mortality and morbidity, target vessel patency, endoleaks, and reinterventions were documented. Results: Technical success was 95% (37/39). Three (8%) patients died in-hospital from mesenteric embolism in 2 and renal artery rupture with consequent multiorgan failure in 1. Two (5%) patients suffered an intraoperative embolic stroke. During a median follow-up of 33 months (range 4–55), adjunctive maneuvers were performed in 9 (23%) patients, including reintervention for type II endoleak with enlarged aneurysm sac in 2 (5%). Four additional patients died of causes unrelated to the aortic pathology (overall mortality 18%). In 34 (94%) of the 36 patients seen in follow-up, aneurysm sac size was stable or decreased. Target vessel stent patency was 99% (95/96). Conclusion: FEVAR with the Anaconda device delivers satisfactory short-term technical and clinical success rates in patients with juxtarenal, suprarenal, and type IV TAAA. Midterm efficacy and durability with respect to aneurysm sac regression and target vessel patency appear very good. Overall mortality and the need for reintervention were significant in this patient cohort.

Keywords

abdominal aortic aneurysm endoleak endovascular aneurysm repair fenestrated stent-graft juxtarenal aneurysm mortality reintervention suprarenal aneurysm thoracoabdominal aortic aneurysm

Introduction

In the past 2 decades, endovascular aneurysm repair (EVAR), being less invasive and demonstrating lower mortality and morbidity, has replaced open repair as the treatment of choice for infrarenal abdominal aortic aneurysm (AAA) in a mostly elderly patient population.^1,2 This paradigm shift from open to endovascular repair has moved up to the juxtarenal and suprarenal level of the abdominal aorta with the use of fenestrated stent-grafts.^3-5 Even if randomized controlled trials comparing FEVAR vs open repair are still missing, most retrospective analyses of the published data demonstrate noninferiority of the endovascular approach regarding perioperative mortality and morbidity in anatomically suitable patients.^6-9

Yet unlike open surgery, FEVAR requires specific anatomic criteria that need to be met for the patient to be suitable for the procedure. For example, the suprarenal and infrarenal aortic neck angulations should not be too great, the target vessels should not be in close proximity, and both iliac axes should be patent for target vessel cannulation.^10,11 The Anaconda fenestrated device (Vascutek, Renfrewshire, Scotland) was introduced in 2010 to broaden some of these anatomic criteria. The initial experience with this new endograft was promising, but overall published outcomes are very limited.^12-14 The largest published series of 25 patients with an 11-month median follow-up reported 4% operative mortality and 96% target vessel patency.¹⁴ However, data are lacking about the performance of the device in the longer term.

The aim of this study was to analyze our experience with the Anaconda fenestrated device over a 5-year period and provide data on the midterm performance of the device.

Methods

Study Design

All patients receiving the fenestrated Anaconda device in a single institution were included in this study. The decision to treat was according to current guidelines.¹⁵ FEVAR was indicated in cases with neck anatomy unsuitable for conventional EVAR and with high operative risk for open repair (American Society of Anesthesiologists score ≥3). In this analysis, juxtarenal AAA referred to aneurysms that involved the infrarenal abdominal aorta adjacent to or including the lower margin of renal artery origins. Suprarenal aneurysms extended up to the superior mesenteric artery (SMA), involving one or both renal arteries. Type IV TAAAs extended from the 12th intercostal space to the iliac bifurcation, involving the visceral aortic segment and the origins of the renal, SMA, and celiac arteries. Cardiac and pulmonary assessment, including (stress) echocardiography, pulmonary function testing, and further cardiologic workup, if required, was performed preoperatively. Informed consent was obtained preoperatively for all patients.

Patient Population

Between July 2011 and December 2015, 39 patients (median age 74 years, range 59–86; 36 men) underwent FEVAR using the Anaconda device. Comorbidities are listed in Table 1. Mean aneurysm size was 6.2 cm (range 5.0–8.4). Mean infrarenal neck length was 4 mm (range 0–9). Four (10%) patients presented with type IV thoracoabdominal aortic aneurysm (TAAA), 12 (31%) with suprarenal aneurysms (2 following open infrarenal aortic repair), and 23 (59%) with juxtarenal aneurysms. Two patients had a proximal type I endoleak following EVAR. In 5 (13%) patients, the infrarenal neck angulation was >60° (Figure 1).

Table 1.

Characteristics of the 39 Study Patients.^a

Age, y	74 (59–86)
Men	36
ASA classification	3 (2–4)
Hypertension	34 (87)
Smoking history	16 (41)
Diabetes mellitus	5 (13)
GFR <60 mL/min/1.73 m²	16 (41)
Dialysis	2 (5)
BMI >30 kg/m²	34 (87)
CAD	24 (61)
Previous myocardial infarction	6 (9)
COPD	5 (17)
PAD	8 (20)
Previous infrarenal aortic surgery	4 (10)

Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; CAD, coronary artery disease; COPD, chronic obstructive pulmonary disease; GFR, glomerular filtration rate; PAD, peripheral artery disease.

Continuous data are presented as the median (range); categorical data are given as the counts (percentage).

Stent-Graft Planning and Configuration

All patients underwent preoperative computed tomography angiography (CTA) with 1-mm slice thickness. Three-dimensional and multiplanar workstation reconstructions (OsiriX; Pixmeo, Geneva, Switzerland) were generated to assess aneurysm morphology. Target vessels >4 mm were incorporated into the custom-made fenestrated Anaconda stent-graft, which has been described in detail before.¹² A composite 3-part system (bifurcated fenestrated graft and 2 limbs) was used in the majority of cases (n=36). A fenestrated cuff was chosen in 2 patients (one secondary to EVAR and another secondary to open aortic repair). One case with chronic total occlusion of the unilateral iliac vessels required an aortouni-iliac device. Before implantation, prototype grafts were deployed into plastic phantoms created from the CT data to simulate in vivo implantation.

A total of 106 fenestrations were incorporated (73 renal arteries, 25 SMA, and 8 celiac trunks). The most common configuration (n=17) was fenestrations for the renal arteries and SMA (commonly augmented with a scallop for the celiac trunk). Twelve stent-grafts had fenestrations for the renal arteries and a scallop for the SMA. Six stent-grafts with 4 fenestrations (renal arteries, SMA, celiac trunk) were designed and 2 with 5 fenestrations (3 renal arteries, SMA, celiac trunk). Two stent-grafts with only 1 fenestration for a single renal artery were also constructed.

Three cases with concomitant common iliac artery aneurysms needed a Zenith iliac side branch endograft (Cook Medical, Brisbane, Australia) combined with the fenestrated Anaconda.

Endovascular Procedure

Patients were taking 100 mg/d of acetylsalicylic acid prior to the procedure, which was performed in a surgical theater equipped with a recent-generation mobile C-arm (Philips, Best, the Netherlands). All patients were under general anesthesia. Bifemoral and left axillary cutdowns were performed, and 5000 units of heparin were administered prior to sheath placement; further heparin was given to keep the activated clotting time at 250 seconds throughout the procedure. Two additional 7-F sheaths were placed into both superficial femoral arteries and connected with the contralateral 20- or 22-F working sheath to maintain perfusion to both legs during the time the large sheaths were in place retrogradely.¹⁶

After deployment of the fenestrated main body, the fenestrations and target vessels were cannulated using a transfemoral or transaxillary approach. If necessary, the device was repositioned to enable target vessel cannulation. Subsequent stenting was performed using Atrium V12 (Atrium Maquet Getinge Group, Mijdrecht, the Netherlands) or BeGraft (Bentley Innomed, Hechingen, Germany) covered stents that were flared with 20-mm-long Admiral balloons (Medtronic Vascular, Santa Rosa, CA, USA). Completion angiography was performed after placement of the limb extensions. Patients continued the acetylsalicylic acid regimen postoperatively; clopidogrel (75 mg/d) was given for 4 weeks.

Follow-up

A postoperative CTA was performed in all patients with normal renal function before hospital discharge. In patients with severe renal insufficiency [glomerular filtration rate (GFR) <30 mL/min], duplex ultrasound was performed instead. After hospital discharge, patients had routine clinical examinations and CTA (with prior renal function testing) at 6 months, 1 year, and annually thereafter. The follow-up protocol has been individualized with growing experience and currently ultrasound alone is performed in uneventful cases after confirmation of aneurysm sac shrinkage.

Statistical Analysis

Outcomes are reported according to the Society for Vascular Surgery 2002 reporting standards for AAAs.¹⁷ Technical success was determined by successful completion of FEVAR with a patent endograft and target vessels and no evidence of type I or III endoleak on the first postoperative CT scan. Renal function was based on creatinine clearance (Cockcroft-Gault equation), and acute kidney injury was classified according to the RIFLE classification system (R, defined as GFR decrease of 25%; I, GFR decrease of 50%; F, GFR decrease of 75%; L, loss of kidney function >4 weeks; E, permanent hemodialysis).¹⁸

Continuous data are presented as the median and absolute range; categorical data are given as the counts (percentage). Survival and freedom from reintervention analyses were performed using the Kaplan-Meier method and are reported with the corresponding 95% confidence intervals (CIs). Statistical survival and event analyses were performed using SAS for Windows (version 9.4; SAS Institute, Cary, NC, USA). Survival curves were plotted using MedCalc for Windows (version 15.2.2; MedCalc Software, Ostend, Belgium).

Results

Technical success was achieved in 37/39 (95%) patients. One failure occurred in an 80-year-old patient who suffered renal artery rupture after predilation for stenosis. The vessel was occluded with a vascular plug and abdominal decompression was performed, but the patient died 3 days later of multiple organ failure. In the other case, a renal fenestration could not be cannulated and the renal artery occluded, culminating in shrinkage of the left kidney and severe renal impairment (RIFLE stage F) without the need for dialysis. Median procedure and fluoroscopy times were 274 minutes (range 193–626) and 71 minutes (range 35–239), respectively. Median contrast dose was 170 mL (range 80–380). The median hospital stay was 8 days (range 5–61).

Perioperative Mortality and Morbidity

In-hospital mortality was 8% (3/39). In addition to the death mentioned above, 2 patients died of small bowel ischemia at 7 days and 2 weeks, respectively, as a consequence of mesenteric embolism. Another patient underwent ascending colon resection due to ischemia 3 days postoperatively and survived.

Two (5%) patients suffered intraoperative right hemisphere embolic strokes. One patient recovered and is able to walk unaided following neurologic rehabilitation. The second patient is still not able to stand 9 months after the embolic episode. A patient with type IV TAAA developed paraplegia 48 hours after the procedure. Symptoms regressed completely after reducing the cerebrospinal pressure to <10 mm Hg through a preoperatively placed drain. In addition to the renal impairment in a technically unsuccessful case, 2 (5%) patients developed moderate kidney injury (RIFLE stage I) owing to partial embolic renal infarction. Another 5 (13%) patients had mild kidney injury (RIFLE stage R) according to the creatinine clearance assessment.

Two patients early in our experience before adopting the distal perfusion protocol mentioned above required a fasciotomy of the lower legs at the end of the operation for acute compartment syndrome.

Follow-up and Postoperative Adjunctive Maneuvers

Median follow-up was 33 months (range 4–55), during which time 4 patients died of causes unrelated to the aortic pathology (cardiac failure in 3 and lung cancer in 1). Estimated survival at 1 and 3 years was 87.2% (95% CI 76.9 to 97.7) and 81.1% (95% CI 68.5 to 3.8), respectively (Figure 2A).

Postoperative adjunctive maneuvers were performed in 9 (23%) patients. In 2, dislocation of the bridging covered renal stents without endoleak was observed on CT at 1 and 2 years, respectively; another covered stent was placed in both. In another 2 cases, a SMA and a renal artery were restented after detection of stent fracture on CT at 1 year. One patient underwent thrombectomy 2 months after FEVAR due to an acute graft limb occlusion. Coil embolization of the inferior mesentery artery in 1 patient and translumbar sac puncture and glue embolization in another patient were performed for type II endoleaks and aneurysm sac expansion at 1 and 2 years after FEVAR, respectively. In all other patients (34/36, 94.4%) aneurysm sac size was stable or decreased during follow-up. Estimated freedom from reintervention at 1 and 3 years was 92.0% (95% CI 83.4 to 100) and 69.4% (95% CI 52.1 to 86.7), respectively (Figure 2B).

One patient underwent successful TEVAR for ruptured thoracic aortic aneurysm 2 years after FEVAR. One stented renal artery occluded within 1 year after FEVAR, resulting in renal function deterioration (RIFLE stage I) and leading to an overall target vessel stent patency of 99% (95/96). No graft migration or component separation was observed during follow-up.

Discussion

Fenestrated stent-grafting of AAAs involving the renal and visceral arteries has been shown to be a feasible alternative to open repair in the armamentarium of the modern vascular surgeon.^3-7 In the authors’ institution, first-line treatment options for complex aortic aneurysms are not solely open or endovascular. The decision relies on the patient’s age, the results of cardiopulmonary testing, and the patient’s wishes. Younger fit patients, and especially those with connective tissue disease, are still undergoing open surgery. The majority of the patients, though, are offered endovascular repair mostly because of older age and comorbidities. Thus, in the 5-year period of this study, almost three quarters of patients with juxtarenal and suprarenal AAAs in the authors’ institution were treated with fenestrated stent-grafting.

The FEVAR procedure is sometimes limited by anatomic factors (>60° neck angulation and proximity of target vessels) that the Anaconda fenestrated device was designed to address.¹² In the authors’ institution, the fenestrated Zenith system (Cook Medical, Bloomington, IN, USA) has also been used for FEVAR. The Anaconda device has been employed in patients anatomically unsuitable for the Zenith stent-graft or when faced with sharp downward-directed takeoff target vessels that can be cannulated from above using the Anaconda device, which results in less distortion of native vessel anatomy.¹⁹ Moreover, the vicinity of target vessels is less often a problem with the Anaconda device, since the fenestration-bearing proximal body is unsupported by stents that could interfere with fenestration placement.^13,14 The unsupported body in combination with 2 proximal sealing rings and the possibility of reconstraint and repositioning during delivery facilitate treatment of even severely angulated aortic necks,^13,14 as in 5 patients in this series.

Despite these advantages, one renal artery could not be cannulated in this cohort due to infolding of the graft material covering the fenestration. The reason for the second technical failure in the patient with the renal artery rupture was clearly unrelated to the stent-graft and occurred very early in this series. Thus overall technical success was high in this cohort despite the fact that only one third of patients underwent “straightforward” FEVAR with 2 fenestrations for juxtarenal aneurysms. The majority of patients had involvement of at least 3 vessels. Of course, the learning curve with this new device is included in this series.

The clinical success is obviously even more important than the technical success. The 8% in-hospital mortality in this group has to be discussed critically and is clearly associated with the proximal extent of the aneurysms.²⁰ As reported by other groups^3,9 and nicely demonstrated by a recent multicenter prospective study,²⁰ the outcomes of FEVAR are strongly correlated to the level of the proximal extent of the aneurysm, which obviously increases the complexity of the repair. In the WINDOWS study,²⁰ the risk of in-hospital mortality was more than twice as high for suprarenal and type IV TAAAs vs juxtarenal aneurysms (14.3% vs 6.5%). In fact, suprarenal aneurysm was the single independent factor associated with an increased risk for mortality in the multivariate analysis in this 268-patient study.²⁰

The most frequent cause of death in FEVAR is reported to be bowel ischemia as a result of mesenteric embolism,^9,14 which occurred in 3 of our patients (all with stented SMA fenestrations) and was fatal in 2. Two of these patients had a shaggy aorta on preoperative CT; the third patient had the device repositioned at the level of the SMA before final deployment. As pointed out before,¹⁴ the occurrence of thromboembolic events warrants a very careful approach regarding device repositioning. Special caution should be given in cases with a heavily atheromatous visceral segment, with some suggesting that these patients should be preferably offered open repair.⁹

FEVAR was also associated with relevant morbidity and reintervention rates in this series. Both patients suffering intraoperative stroke presented with an atheromatous aortic arch, and while both strokes were right hemisphere and probably unrelated to the left transbrachial access used, one has to keep in mind that the transbrachial approach for target vessel cannulation increases the risk for iatrogenic stroke, as seen in patients undergoing transbrachial chimney graft implantation.⁶ Furthermore, the unsupported main body of the Anaconda device, while enabling treatment of severely angulated aortic necks and giving more options for placement of the fenestrations as mentioned above, also poses the risk of an increased range of motion of the unsupported fabric bearing the fenestrations.¹⁴ This can lead to dislocation of the bridging covered stent, as seen in 2 of our patients, who required stent extension.

Nevertheless, the overall 99% rate of target vessel patency after a median follow-up of almost 3 years demonstrates the midterm durability of these endovascular reconstructions. The high rate (94%) of aneurysm sac shrinkage / stabilization and the absence of an aneurysm-related death during follow-up also reflect the efficacy of FEVAR in this group of patients. Finally, since the majority of reinterventions were required in the first year after FEVAR, we, like other groups, would also advocate a more individualized surveillance protocol in these patients, aimed at reducing the number of CTAs by substituting duplex ultrasound in patients with documentation of sac shrinkage and patent target vessels.⁴

Conclusion

The fenestrated Anaconda stent-graft system performs well, with satisfactory short-term technical and midterm clinical success rates in patients with juxtarenal, suprarenal, and type IV thoracoabdominal aortic aneurysms who were not good candidates for open surgery. Because of its unique specifications, this system can broaden the indication for endovascular treatment in these patients in terms of anatomic suitability. Midterm efficacy and durability with respect to aneurysm sac regression and target vessel patency appear very good. Overall mortality and reintervention rates were significant in this patient cohort.

Footnotes

Declaration of Conflicting Interests

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Johannes Kalder is a consultant for Vascutek, Bentley Innomed, and Cook Medical.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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