Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Abstract

Introduction:

Fenestrated endovascular aneurysm repair (FEVAR) has emerged as a standard treatment for complex abdominal and thoracoabdominal aortic aneurysms (CAAAs/TAAAs), yet target vessel instability (TVI) remains a concern. This study evaluates mid-term outcomes and anatomical predictors of TVI following FEVAR using the Anaconda custom-made fenestrated stent-graft system (Terumo Aortic, Inchinnan, Scotland, UK).

Methods:

A retrospective single-center study included all consecutive patients treated with FEVAR using Anaconda stent-graft between September 2013 and December 2023. Preoperative and postoperative vessel geometry was assessed using Aquarius iNtuition software (TeraRecon, Foster City, CA). Primary endpoints were TVI (occlusion, stenosis, type I/III endoleak, or re-intervention) and freedom from re-intervention at 12 months. Secondary endpoints were intraoperative technical success and 30-day major adverse events (MAEs) rate.

Results:

A total of 101 patients with 359 target vessels were analyzed. Technical success was 97%. The 30-day MAE rate was 21.7%, with no mortality. Target vessel instability occurred in 7.8% (4.5% type IIIc endoleak, 1.4% stenosis, and 1.9% type Ic endoleak) during a median follow-up of 36 months (interquartile range [IQR]=22–55 months). Multivariate analysis identified increased sealing length (odds ratio [OR]=1.080, 95% confidence interval [CI]: 1.002, 1.164, p=0.044) and intra-aortic stent protrusion≥7 mm (OR=1.406, 95% CI: 1.067, 1.852, p=0.015) as independent predictors of TVI in visceral vessels. In renal target vessels, protrusion ≥ 7 mm (OR=1.284, 95% CI: 1.019, 1.618, p=0.034) was significantly associated with occlusion. Cumulative incidence of TVI with death as competing risk was 3.1%, 3.6%%, and 5.9% at 1, 2, and 5 years, respectively.

Conclusion:

Fenestrated endovascular aneurysm repair using the Anaconda stent-graft system demonstrates high technical success and mid-term freedom from TVI. Extended intra-aortic stent protrusion and sealing length, significantly impact TVI adversely. Optimizing bridging stent geometry may reduce re-intervention rates and improve outcomes in complex aortic repairs.

Clinical Impact

This study demonstrates that fenestrated endovascular aneurysm repair using the Anaconda custom-made fenestrated stent-graft system provides high technical success and durable mid-term target vessel stability in complex aortic aneurysm repair. Importantly, it identifies modifiable anatomical predictors—excessive intra-aortic bridging stent protrusion and increased sealing length—as independent risk factors for target vessel instability. These findings shift attention from device selection alone to precise geometric optimization of bridging stents during procedural planning and deployment. For clinicians, careful control of protrusion length and sealing configuration may reduce endoleaks and re-interventions. The innovation lies in linking quantitative vessel geometry to clinical outcomes, offering actionable parameters to improve durability in FEVAR.

Keywords

fenestrated endovascular aortic repair complex abdominal aortic endovascular repair bridging stent target vessel instability

Introduction

Fenestrated endovascular aneurysm repair (FEVAR) has gained widespread acceptance over the last few decades for the treatment of complex abdominal aortic aneurysms (CAAAs) demonstrating high technical success, low 30 day mortality, and a low perioperative reno-visceral artery occlusion rate.¹ However, almost 40% of patients may require an unscheduled re-intervention within 3 to 5 years, due to endoleak, stenosis, or occlusion of target visceral vessels (TVVs), known in the literature as target vessel instability (TVI).^2–4

Over time, FEVAR has evolved with increasing standardization and technical refinement, based on variety of balloon-expandable and self-expandable covered stents used as bridging devices. High technical success rates and favorable target vessel patency during short-term and mid-term follow-up were reported.^5–7 After an off-label introduction of Advanta V12 (Atrium Medical Corporation, Merrimack, NH, USA)¹ as bridging stent-grafts (BSGs) in FEVAR 20 years ago, the BeGraft Peripheral (Bentley InnoMed GmbH, Hechingen) became the first on-label BSG for FEVAR recently.⁷

Target vessel instability remains a significant clinical challenge, defined by the occurrence of occlusion, significant stenosis, endoleaks (type Ic or IIIc), or the need for re-intervention. Target vessel instability depends both on the fenestrated device and on the BSG. Most current evidence focuses on FEVAR procedures performed with Cook (Cook medical, Bloomington, New Jersey) devices, using the Advanta V12 as a BSG.¹ The performance of the Anaconda stent-graft system (Terumo Aortic, Inchinnan, Scotland, UK) as FEVAR device, independent of the BSG, has been less extensively studied. Its impact on target vessel behavior and postoperative anatomical geometry is unknown.

This retrospective study aims to analyze the mid-term outcome and geometrics of TVI after FEVAR with Anaconda stent-graft system.

Materials and Methods

Study Design

This was a retrospective single-center study of prospectively collected data. The study followed the reporting guidelines from the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology).⁸ The study was approved by the local ethical committee (BASEC-ID 2024-02142).

Study Population

All consecutive patients diagnosed with complex abdominal aortic aneurysms (CAAAs) or thoracoabdominal aortic aneurysms (TAAAs) who underwent elective FEVAR between September 2013 and December 2023 were included.

Only procedures performed using Anaconda stent-grafts were considered for analysis.

Patient data, including demographic details, clinical history, cardiovascular comorbidities, anatomical characteristics, as well as intraoperative and postoperative variables, were collected prospectively in a dedicated registry and analyzed retrospectively after anonymization.

The anatomical extent of aortic aneurysm was classified according the current reporting standards based on the preoperative contrast-enhanced computed tomography angiography (CTA).⁴

Characteristics of the Anaconda stent-grafts have been previously described.^9,10

Briefly, it is a custom-made device with an unsupported body, loaded into a 20F outside diameter sheath. Fixation in the aortic wall is achieved by 2 proximal rings and 3 or 4 pairs of proximal hooks. The rings are oversized by up to 25%, providing a specific design that offers a better proximal seal.¹⁰ The main advantage of the Anaconda custom-made device is its unsupported part, which allows for an unlimited number of nitinol-reinforced fenestrations. After deployment of the proximal part, repositioning throughout the procedure is possible, while additional access by the contralateral femoral or upper limb is achievable for cannulation and stenting of the fenestrations. In addition, the flexibility of the graft, due to its design, permits adaptation to severely tortuous and angulated anatomies. In contrast, the unsupported design can be associated with a risk of fabric folding and migration.

Advanta V12 and Bentley BeGraft peripheral stents were used as the main BSGs to establish the connection between the fenestration and the TVVs. Both are designed to be compatible with 0.035 inch systems in various diameters and lengths. The Advanta V12 balloon expandable covered stent (Atrium Medical Corporation, Merrimack, New Hampshire) is stainless steel with open cells constructed polytetrafluoroethylene (PTFE) and premounted on a non-compliant balloon catheter.¹ The BeGraft peripheral stent is a cobalt-chrome stent covered with a micro-porous extended PTFE (ePTFE) membrane. It is compatible with 6F catheters up to 8 mm in diameter. The ePTFE covering is securely affixed from the interior at both ends of the stent to minimize the risk of graft material detachment.⁷

As standardized flaring technique for we use a 2 cm long percutaneous transluminal angiography (PTA) balloon whose size depends on size of bridging stent and used to be 2 mm bigger than the bridging stent (6 mm bridging stent = 8 mm balloon, etc).

Planning of the Anaconda fenestrated graft and the BSGs was performed using CTA. Dedicated software for aorta and visceral vessel analysis was utilized. An aorto-iliac plastic reconstruction of the aortic endograft was created by the planning center, relying on the CTA data to ensure the correct position of the fenestrations. The estimated time from manufacturing to delivery of the aortic endograft was 6 weeks. Preoperative and postoperative anatomical measurements including target vessel evaluations were performed using Aquarius iNtuition software (TeraRecon, Foster City, California)

A circumferential calcification >50% and >50% obstruction of lumen was defined as a severe iliac calcification. Target vessel parameters were assessed on the last preoperative and the first follow-up CTA (Figure 1):

Vessel diameter (Figure 1A).

Total stent length (from branch origin to the distal end within the target vessel) (Figure 1B).

Protrusion (extent of the stent protruding from the fenestration into the aortic lumen) (Figure 1C).

Bridging length (distance between the main body of the stent-graft and the vessel origin) (Figure 1D).

Sealing length (segment of the bridging stent in contact with the native vessel without gaps) (Figure 1E).

Oversizing ratio (ratio between bridging stent diameter and native target vessel diameter).

These geometric parameters were analyzed for their association with TVI. Measurements were performed by a medical student after careful supervised preparation for 2 weeks, and then independently checked by 2 qualified vascular surgeons.

The early postoperative period was defined as occurring within the hospital stay or during the first 30 days. Major adverse events (MAEs) were defined as a composite endpoint, including death, acute kidney injury, new-onset dialysis, myocardial infarction, paraplegia, stroke, and bowel ischemia requiring surgical resection and any re-intervention. Technical success was defined as successful placement of main aortic stent-graft and delivery of bridging stents to the target vessels, and patent target vessels without stenosis or endoleak type I/III on the first postoperative CTA.⁴ Computed tomography angiography was performed before discharge or during the first 30 days after the procedure.

Follow-up assessments were conducted in a specialized outpatient clinic dedicated to aortic pathologies, with routine clinical and radiological evaluations scheduled at 6 and 12 months postoperatively, and annually thereafter. During follow-up, data regarding MAEs, TVI, re-interventions, and mortality were systematically recorded.

Study Endpoints

The primary study endpoints were TVI, defined as target vessel occlusion, stenosis, and/or type I/III endoleak, and re-interventions (freedom from overall and aortic-related re-intervention) at 12 months.⁴

Secondary endpoints included the incidence of TVI and MAEs within 30 days. Major adverse events were defined as death, acute kidney injury, new-onset dialysis, myocardial infarction, neurological complications (such as paraplegia or stroke), bowel ischemia requiring surgical resection, and any form of re-intervention. Other secondary endpoints were technical success, mortality, and long-term TVI. To assess the impact of preoperative target vessel anatomy (diameter) and postoperative geometry after stenting (total bridging stent length including sealing length, bridging length [gap] and protrusion and oversizing ratio) on the TVI, the latter mentioned parameters were analyzed.

Statistical Analysis

Data analysis was performed with SPSS Statistics (version 29; IBM, Chicago, Illinois) and R software. Continuous variables were expressed as mean ± standard deviation or median with interquartile ranges, according to the normality of distribution. Normality was assessed using Kolmogorov-Smirnov test. Categorical variables were presented as numbers and percentages. To evaluate freedom from TVI and re-intervention, time-dependent analysis was done using the Kaplan-Meier calculation.

For adequate reporting of freedom from TVI, a time-to-event analysis was performed with non-parametric cumulative-incidence (Aalen-Johansen) estimator of the sub-distribution function for instability, treating death as a competing event.

Significance was assessed using log-rank test (p<0.05).

To increase the number of events per target vessel and thereby the significance in statistical analysis, celiac trunk (CT) and superior mesenteric artery (SMA) were combined as visceral target vessels (VTV), while both renal arteries were grouped as renal target vessels (RTVs). Cross-tables and t test for independent variables were performed for analysis of the impact of preoperative target vessel anatomy and geometry after stenting on TVI. Covariates with a p value<0.2 in univariate analysis were entered into the multivariate model. Univariate and multivariate Cox proportional hazard models were used to identify clinical, procedural, and anatomical factors associated with TVI. Anatomical parameter, which was found to have a significant influence on TVI, was further evaluated with the receiver operating characteristics (ROC) curve analysis to determine a cut-off value associated with an increased risk of instability.

Results

General Cohort

A total of 101 consecutive patients, with 359 target vessels (VTVs, 161 and RTVs, 198) who underwent FEVAR with a custom-made Anaconda stent-graft between September 2013 and December 2023 were included. The mean age was 74±6.0 years and 75% (76/101) were male. The mean aneurysm diameter was 62±8.2 mm. The main indication for treatment were degenerative aneurysms (91/101, 90.1%). All patients were treated electively. Patients’ demographics and characteristics are described in Table 1.

Table 1.

Demographics, Baseline Characteristics, and Presenting Aortic Details of the Study Cohort.

	N=101 (%)
Demographics
Age (years)	74±6.0
Male sex	76 (75)
BMI (kg/m²)	28.4±7.6
Baseline characteristics
CAD	52 (51.5)
CHF	20 (19.8)
Arrhythmia	17 (16.8)
Stroke	11 (10.9)
COPD	34 (33.7)
Smoking	78 (77.2)
Diabetes mellitus	18 (17.8)
Renal impairment	41 (40.6)
Dialysis	2 (1.9)
Baseline serum creatinine (mg/dL)	100.8±56.0
Baseline estimated GFR (mL/min)	67.2±18.5
Malignancy	25 (24)
Previous thoracic and/or abdominal repair	40 (39)
Open	7 (7.5)
Endovascular:	37 (92.5)
TEVAR	28 (75.7)
Aortic details
Etiology
Degenerative	91 (90.1)
Postdissection	7 (6.9)
PAU	3 (3.0)
Type:
TAAA type I	1 (1.0)
TAAA type II	2 (2.0)
TAAA type III	11 (10.9)
TAAA type IV	14 (13.9)
TAAA type V	6 (5.9)
Suprarenal	8 (7.9)
Juxtarenal	51 (50.5)
Infrarenal	8 (7.9)
Aortic diameter (mm)	62.0±8.2

Abbreviations: BMI, body mass index; CAD, coronary artery disease; CHF, chronic heart failure; COPD, chronic obstructive pulmonary disease; GFR, glomerular infiltration rate; PAU, penetrating aortic ulcer; TAAA, thoracoabdominal aortic aneurysm; TEVAR, thoracic endovascular aortic repair.

Endograft configuration was 1 fenestration in 4 cases (3.9%), 2 fenestrations in 8 cases (7.9%), 3 fenestrations in 22 cases (21.8%), 4 fenestrations in 60 cases (59.4%), and 5 fenestrations in 7 cases (6.9%).

The analysis of preoperative and postoperative parameters showed significant differences in vessel diameter, stent diameter, stent length, sealing length, and oversizing ratio between the VTVs and RTVs (p<0.001). The VTV exhibited larger mean vessel (7.0±1.1 mm) and stent diameters (7.8±1.1 mm), as well as greater stent (30.9±5.6 mm) and sealing lengths (20.4±6.5 mm). Bridging length and stent protrusion showed no statistically significant differences between both groups (p=0.098 and 0.237, respectively). The oversizing ratio remained consistent among both (1.1±0.1–0.2, p<0.001) (Supplementary Table 1).

Technical success rate was 97% (3/101). Two patients presented a type Ib endoleak in the postoperative computed tomography scan and were successfully treated by limb extension. We could not catheterize one renal artery due to partial misplacement of main body with the coverage of vessel origin. Including this loss of target vessel, we observed 3 (0.84%) intraoperative TVIs. In another patient, renal bridging stent stenosis had to be dilated, and in another patient, celiac bridging stent showed a type Icendoleak and had to be extended distally. Perioperative data are shown in Table 2.

Table 2.

Operative, Postoperative, and Follow-Up Outcomes of the Study Cohort.

	N=101 (%)
Operative details
No. of patients with no. of TV
1	4 (3.9)
2	8 (7.9)
3	22 (21.8)
4	60 (59.4)
5	7 (6.9)
CT fenestration	71
SMA fenestration	90
RRA fenestration	97
LRA fenestration	101
Total aortic covered length (mm)	211.6±78.6
Operative time (min)	236.9±87.2
Contrast dose (mL)	158.9±65.5
Blood loss (mL)	400 (200–500)
CSF drainage	14 (13.9)
Technical success	98 (97)
Target vessel instability	3/359 (0.84)
In-hospital/30 day outcomes
Hospital length of stay (days)	6 (4–8)
Pneumonia	1 (0.9)
SCI	6 (5.9)
Stroke	0
Renal impairment	22 (21.8)
Dialysis	2 (1.9)
Mesenteric ischemia (conservative treatment)	2 (1.9)
In-hospital/30 day mortality	0
In-hospital/30 day re-intervention	14 (13.9)
Access-related	10 (9.9)
Aortic-related	4 (3.9)
Follow-up outcomes
Follow-up period (months)	36 (22–55)
Target vessel instability	28 (7.8)
Re-interventions	38
Aortic-related	10
Bridging stent-related	28
Mortality	22 (21.8)

Abbreviations: CSF, cerebrospinal fluid; CT, celiac trunk; LRA, left renal artery; RRA, right renal artery; SCI, spinal cord ischemia; SMA, superior mesenteric artery; TV, target vessel.

Thirty-Day Outcomes

A total of 45 MAEs occurred within 30 days. Spinal cord injury (SCI) was recorded in 5.9% (6/101) of the patients. In all patients FEVAR was the last step in a multi-step procedure in TAAA repair. All of them occurring immediately postoperatively and had a paraparesis score of 4 according to the Greenberg classification.^9,11 All patients were managed by hypertensive therapy, blood transfusion, and cerebrospinal fluid drainage (CSFD). Symptoms of SCI fully recovered at discharge in all patients. No strokes have been recorded in the early period.

Twenty-two (21.7%) patients presented deterioration of the renal function but only 2 patients required temporary hemodialysis. In one case, the cause of renal function worsening was stenosis of the BSG, which was treated successfully by PTA.

In 14 patients (4.0%), re-intervention was required within 30 days. Within 30 days, no patient died. The complete 30 day outcomes are demonstrated in Table 2.

Follow-Up Outcomes (>30 Days)

The median follow-up was 36 months (IQR=22–55). Within the follow-up, a total of 28 TVIs (7.8%) have been detected and needed re-intervention: 14 in visceral (5 CTs and 9 SMAs) as well as in RTVs (7 in each renal artery). The etiology was stent fracture in 7 patients (25%/1 CT, 2 SMA, 1 right renal artery [RRA], and 3 left renal arteries [LRAs]) (all BeGraft), detachment from fenestration (endoleak type IIIc) in 9 patients (32%/2 CTs, 3 SMAs, 2 RRAs, and 2 LRAs) (4 Advanta; 5 BeGraft), occlusion (2)/stenosis (3) in 5 patients (18%/1 TC, 2 SMA, 1 RRA, and 1 LRA) (3 Advanta; 2 BeGraft) and detachment from target vessel (type Ic endoleak) in 7 patients (25%/1 CT, 2 SMAs, 3 RRAs, 1 LRA) (3 Advanta; 4 BeGraft). All the cases were successfully treated with new BSG extension/re-lining. Estimated freedom from TVI was 96.3% at 1 and 2 years and 93.8% at 5 years (Supplementary Figure 1).

Cumulative incidence of TVI (with death as competing risk) was 3.1%, 3.6%, and 5.9% at 1, 2, and 5 years, respectively (Figure 2).

In the observation period, a total of 22 patients died (22/101, 21.8%). One due to aneurysm-related death, and in 4, the cause of death remained unknown. Two patients died due to cardiac failure at 56 and 65 months after the index operation, respectively, while 1 patient died due to stroke after 44 months. The rest of the patients died due to cancer: lung (n=4) and pancreas (n=2), while in 8 cases, the type was unknown. Estimated survival was 95% at 1 year, 89.6% at 2 years, and 76.5% at 5 years (Figure 3).

Ten patients had an aortic-related re-intervention, resulting in a freedom from aortic-related re-interventions of 90.9%. Three patients presented with type Ia endoleak at 12, 15, and 48 months. All patients received a 4× FEVAR with supraceliac landing zone. In 2 patients, proximal disease progression was the reason for type Ia endoleak. In 1 patient, migration was detected. An extension thoracic graft was used in all patients. Three patients showed a type Ib endoleak after 1, 23, and 60 months, and all received a limb extension. Two patients suffered from acute limb occlusion after 7 and 8 months and were successfully treated with lysis and stenting of stenosis. One patient was treated after 9 months for type III endoleak of the right limb. Another patient showed a persistent type II endoleak from the inferior mesenteric artery after 12 months, accompanied by a progressive increase in the aneurysm sac (>1 cm/year), which was successfully treated with coil embolization. The estimated freedom from overall re-intervention was 99% at 1 year, 95.4% at 2 years, and 74.6% at 5 years, and freedom from aortic-related re-intervention was 99.8% at 1 year, 98.9% at 2 years, and 88.5% at 5 years (Figure 4).

Analysis of TVI

Evaluation of the influence of demographic and procedural parameters on TVI

Multivariate analysis revealed that diabetes (odds ratio [OR]=0.086, 95% confidence interval [CI]: 0.013, 0.554, p=0.010) and operative time (OR=1.018, 95% CI: 1.005, 1.032, p=0.007) were independently associated with visceral TVI.

Regarding renal TVI, multivariate analysis showed significant association with chronic obstructive pulmonary disease (COPD) (OR=22.810, 95% CI: 1.405, 370.258, p=0.028) and iliac calcification (OR=0.038, 95% CI: 0.003, 0.477, p=0.011) (Table 3).

Table 3.

Analysis of Demographic, Baseline Characteristics, Aortic Details, and Procedural Parameters on Target Vessel Instability.

Factor	Univariate	Multivariate
Factor	p value	p value	OR	95% CI
Total TVI
BMI (kg/m²)	0.090	0.029	0.925	0.862, 0.992
COPD	0.189
Diabetes	0.046	0.063	0.195	0.035, 1.090
Arrhythmia	0.040
TAAA type V aneurysm	0.014
Juxtrarenal aneurysm	0.023
Type of aneurysm	0.036
CSF drainage	0.032
Largest aortic diameter (mm)	0.075
Total aortic covered length (mm)	0.003	0.032	1.017	1.001, 1.033
Operative time (min)	0.005	0.052	1.009	1.000, 1.018
VTV TVI
Diabetes	0.003	0.010	0.086	0.013, 0.554
Previous thoracoabdominal endovascular repair	0.035
Postdissection etiology	0.062
TAAA type V aneurysm	0.003
CSF drainage	0.025
Largest aortic diameter (mm)	0.181
Total aortic covered length (mm)	0.000
Operative time (min)	0.009	0.007	1.018	1.005, 1.032
RTV TVI
BMI (kg/m²)	0.067	0.079	0.921	0.840, 1.010
COPD	0.130	0.028	22.810	1.405, 370.258
Arrhythmia	0.059
TAAA type V aneurysm	0.034
Suprarenal aneurysm	0.081
Juxtarenal aneurysm	0.041
Severe iliac calcification	0.105	0.011	0.038	0.003, 0.477
CSF drainage	0.025
Total aortic covered length (mm)	0.076
Operative time (min)	0.004

Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; CSF, cerebrospinal fluid; RTV, renal target vessel; TAAA, thoracoabdominal aortic aneurysm; TVI, target vessel instability; VTV, visceral target vessel.

Geometrical analysis of TVI

Univariate analysis of target vessel geometrical parameters showed that re-intervention in VTV, was significantly associated with longer sealing lengths (23.4±10.3 mm vs 18.3±6.5 mm, p=0.006) and greater intra-aortic stent protrusion (6.6±2.2 mm vs 5.0±2.0 mm, p=0.003). Target vessel instability in VTV was also associated with increased sealing length (23.0±10.1 mm vs 18.3±6.5 mm, p=0.010) and intra-aortic stent protrusion (6.4±2.3 mm vs 5.0±2.0 mm, p=0.011). Multivariate logistic regression and Cox regression analyses in VTV supported this findings and showed that increased sealing length (OR=1.080, 95% CI: 1.002, 1.164, p=0.044/hazards ratio [HR]=1.065, 95% CI: 1.014,1.118, p=0.012 and aortic stent protrusion (OR=1.406, 95% CI: 1.067, 1.852, p=0.015) are independent predictors of re-intervention.

ROC curve analysis showed that an intra-aortic stent protrusion ≥ 7 mm was predictive for re-intervention (area under the curve [AUC]=0.710) (Supplementary Figure 2).

In RTV, greater intra-aortic stent protrusion was significantly associated with stent occlusion (8.4±1.5 mm vs 4.7±1.5 mm, p=0.001) (Table 4). This was confirmed in the multivariate analysis, where greater intra-aortic stent protrusion presented a significant risk to stent occlusion (OR=1.284, 95% CI: 1.019, 1.618, p=0.034). ROC curve analysis revealed that an intra-aortic stent protrusion≥7 mm was predictive of occlusion (AUC=0.970) (Supplementary Figure 3).

Table 4.

Analysis of Influence of Preoperative and Postoperative Parameters on VTV and RTV Events.

TV parameters	Events		p value
TV parameters	No	Yes
Occlusion
VTV
Vessel diameter (mm)	6.8±1.1	6.8±1.1	0.924
Stent diameter (mm)	7.7±1.1	7.0±1.1	0.534
Stent length (mm)	29.1±5.9	23.0±5.8	0.300
Sealing length (mm)	18.8±7.1	20.1±4.7	0.799
Bridging length (mm)	2.4±0.8	2.6±0.7	0.700
Protrusion (mm)	5.2±2.1	4.5±2.5	0.660
Oversizing ratio (mm/mm)	1.1±0.1	1.2±0.1	0.715
RTV
Vessel diameter (mm)	5.7±0.7	5.0±0.0	0.140
Stent diameter (mm)	6.3±0.7	5.5±0.7	0.091
Stent length (mm)	25.8±6.0	30.0±11.3	0.325
Sealing length (mm)	17.3±6.8	17.9±8.7	0.910
Bridging length (mm)	2.5±0.7	2.5±1.6	0.936
Protrusion (mm)	4.7±1.5	8.4±1.5	0.001
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.1	0.880
Endoleak
VTV
Vessel diameter (mm)	8.9±1.0	9.4±1.2	0.127
Stent diameter (mm)	7.7±1.1	7.0±1.1	0.534
Stent length (mm)	26.2±6.2	29.2±6.0	0.108
Sealing length (mm)	18.7±5.3	20.6±5.2	0.253
Bridging length (mm)	2.4±0.6	2.6±0.7	0.377
Protrusion (mm)	5.1±1.7	6.1±1.9	0.045
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.0	0.700
RTV
Vessel diameter (mm)	7.7±0.7	8.1±0.6	0.092
Stent diameter (mm)	6.3±0.7	5.5±0.7	0.091
Stent length (mm)	24.5±6.1	25.0±6.1	0.790
Sealing length (mm)	17.2±5.6	17.8±6.0	0.697
Bridging length (mm)	2.5±0.6	2.4±0.5	0.419
Protrusion (mm)	4.8±1.3	4.8±1.3	0.996
Oversizing ratio (mm/mm)	1.2±0.1	1.1 ± 0.1	0.242
Re-intervention
VTV
Vessel diameter (mm)	6.8±1.0	7.0±1.8	0.680
Stent diameter (mm)	7.7±1.0	7.9±1.9	0.938
Stent length (mm)	28.9±5.8	30.9±6.3	0.200
Sealing length (mm)	18.3±6.5	23.4±10.3	0.006
Bridging length (mm)	2.4±0.7	2.7±1.2	0.079
Protrusion (mm)	5.0±2.0	6.6±2.2	0.003
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.1	0.524
RTV
Vessel diameter (mm)	5.7±0.1	5.7±0.1	0.680
Stent diameter (mm)	6.3±0.1	6.3±0.1	0.938
Stent length (mm)	26.0±6.1	23.9±5.1	0.165
Sealing length (mm)	17.3±6.8	17.7±7.0	0.780
Bridging length (mm)	2.4±0.7	2.6±0.8	0.426
Protrusion (mm)	4.8±1.5	5.1±1.8	0.364
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.1	0.883
TVI
VTV
Vessel diameter (mm)	6.8±1.0	7.0±1.7	0.575
Stent diameter (mm)	7.7±1.0	7.9±1.8	0.433
Stent length (mm)	28.9±5.8	30.4±6.4	0.331
Sealing length (mm)	18.3±6.5	23.0±10.1	0.010
Bridging length (mm)	2.4±0.7	2.7±1.2	0.107
Protrusion (mm)	5.0±2.0	6.4±2.3	0.011
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.1	0.474
RTV
Vessel diameter (mm)	5.7±0.7	5.7±0.6	0.680
Stent diameter (mm)	6.3±0.7	6.3±0.6	0.938
Stent length (mm)	26.0±6.1	23.9±5.1	0.165
Sealing length (mm)	17.3±6.8	17.7±7.0	0.780
Bridging length (mm)	2.4±0.7	2.6±0.8	0.426
Protrusion (mm)	4.8±1.5	5.1±1.8	0.364
Oversizing ratio (mm/mm)	1.1±0.1	1.1±0.1	0.883

Abbreviations: RTV, renal target vessel; TV, target vessel; TVI, target vessel instability; VTV, visceral target vessel.

Discussion

Despite the plethora of studies available in the literature on the Anaconda fenestrated stent-graft, mid-term outcome and analysis of TVI remain limited.^10–17 This study specifically examined geometrical parameters associated with TVI after repair of CAAA and TAAA with the custom-made Anaconda stent-graft system, reporting short-term and long-term outcomes based on a single-center experience.

The technical success rate of TVV in our study was 98%, which is consistent with previously published outcomes.^10,11,14 This excellent technical success may be attributed to the repositioning feature and adaptability to most anatomical requirements of the Anaconda stent-graft system and the correct advancement of the BSGs through the recommended sheath size, allowing for smooth deployment. Upward tilting and flaring within the fenestrations were also performed without any issues.

During follow-up, type Ia endoleak rate was 2.9%. All occurring in patients treated with 4 vessel FEVAR and attributed to disease progression and graft migration. Although the Anaconda stent-graft system has a limited proximal sealing zone confined to the area between its proximal rings—a design feature that may predispose to type Ia endoleak—this incidence was comparable with the rate reported by the group from England et al¹⁸ (1.3%) using the Zenith fenestrated endograft (Cook Medical, Bloomington, Indiana). Complications associated with BSGs can have various causes, each potentially requiring different treatment approaches. The most common complication observed was the presence of type IIIc endoleak. Four percent of all bridging stents showed type IIIc endoleak (with stent fracture being the main cause) within the follow-up period and were successfully treated with the deployment of an additional BSG. A possible explanation could be the caudal orientation of BSGs within the fenestrations and visceral vessels. This scenario can result in stent compression and, ultimately, fracture.¹⁷ England et al¹⁸ reported a caudal migration of 6.0 (4.1, 10.0) mm in 23% of FEVAR patients after 36 months of follow-up. They concluded that continuous respiratory and hemodynamic forces caused by blood flow within the aorta create type III endoleaks between the fenestration and BSGs.¹⁸ Shedding more light on this conclusion, the authors noted that the LRA was more affected than the contralateral one. Similarly, in our study, the LRA was the more susceptible vessel for stent fracture, as it was involved in all cases. Our findings are consistent with the percentages of type IIIc endoleaks reported in other studies.^{10–12,14,15} Pini et al⁹ reported an overall rate of 1.7% for type IIIc endoleaks, although mixed (>2 BSGs) types of BSGs were used, with the Advanta V12 (Atrium Medical Corporation, Merrimack, New Hampshire) being the most commonly utilized. Similarly, another multicenter study reported a type IIIc endoleak rate of 2%.¹⁰

In our study, 2 BSG occlusion (0.5%) were recorded during the follow-up period. Both were detected and treated promptly, without severe outcome, although we were not able to recanalize the CT occlusion. Recent meta-analysis demonstrated a pooled occlusion rate of 3.5%.¹⁶ A possible explanation for these occlusions is the increased length of the flared part of the BSGs, which was intended to provide greater stability and sealing. However, this comes at the cost of an increased risk of stenosis and occlusion.¹⁹ In addition, excessive oversizing of the distal end of the BSGs in the visceral arteries may elevate the risk of dissections and dissection-associated occlusions.¹⁹

Univariate analysis revealed that in VTV, longer sealing lengths and greater stent protrusion were associated with re-intervention and TVI. These findings align with a previous study, suggesting that excessive aortic stent protrusion can lead to adverse outcomes due to increased turbulence.²⁰ Multivariate logistic regression further identified stent protrusion ≥7 mm as an independent predictor of both re-intervention and TVI in VTV, underscoring the importance of precise stent deployment.²⁰ In contrast to this finding, Squizzato et al reported an increased target vessel instability in case of a short bridging stent protrusion (<3 mm).²¹ Short protrusion might be associated with loss of main body connection and longer protrusion might be more prone to lead to occlusions due to flow turbulence. These findings are complementary suggesting that the ideal protrusion is located in between.

Cox regression analysis in VTV confirmed that longer sealing length was associated with an increased risk of re-intervention. These results suggest that while adequate sealing is crucial to prevent endoleaks, excessive sealing may predispose to adverse events, possibly due to increased mechanical stress or intimal hyperplasia.²⁰

Receiver operating characteristics analysis showed that an intra-aortic bridging stent protrusion ≥7 mm was associated with re-intervention in VTV and occlusion in RTV. The group of Tsilimparis from Munich also reported that intra-aortic protrusion ≥5.75 mm in RTV is associated with increase of TVI.²⁰

Limitation of Study

The study was a single-center, retrospective study with a limited number of patients and follow-up. The low number of events may have limited the power of the statistical analysis would be necessary for more robust conclusions. In the current study, only a single-center practice/treatment strategy is reported, with the implementation of certain preferred bridging stents and devices, which also represents a limitation of the study. Larger confirmatory studies may be useful to correlate the specific type of TVI with the postoperative geometric conformation. Finally, the patient sample originates from a high-volume academic center with extensive experience in complex aortic endovascular repair, and the reported outcomes may not be reproducible in lower-volume settings.

Conclusion

This series reports excellent technical success of target vessels the use of the Anaconda fenestrated stent-graft. Complications related to TVVs have a low incidence over time and are relatively easy to address. Although there is a need for re-intervention, this does not adversely affect survival during the follow-up period. The critical role of stent dimensions, particularly sealing length and protrusion, in determining clinical outcomes in endovascular interventions. Tailoring stent deployment to the specific anatomical and hemodynamic characteristics of the target vessel is essential to minimize the risk of TVI and re-intervention. Continued advancements in imaging and procedural techniques will further enhance the precision and efficacy of endovascular treatments.

Supplemental Material

sj-docx-4-jet-10.1177_15266028261424752 – Supplemental material for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Supplemental material, sj-docx-4-jet-10.1177_15266028261424752 for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System by Daniel Becker, Georgios I. Karaolanis, Ahmed A. Ali, Konstantinos Kotopoulos, Vaiva Dabravolskaite, Drosos Kotelis, Vladimir Makaloski and Michel Joseph Bosiers in Journal of Endovascular Therapy

Supplemental Material

sj-docx-5-jet-10.1177_15266028261424752 – Supplemental material for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Supplemental material, sj-docx-5-jet-10.1177_15266028261424752 for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System by Daniel Becker, Georgios I. Karaolanis, Ahmed A. Ali, Konstantinos Kotopoulos, Vaiva Dabravolskaite, Drosos Kotelis, Vladimir Makaloski and Michel Joseph Bosiers in Journal of Endovascular Therapy

Supplemental Material

sj-jpg-1-jet-10.1177_15266028261424752 – Supplemental material for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Supplemental material, sj-jpg-1-jet-10.1177_15266028261424752 for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System by Daniel Becker, Georgios I. Karaolanis, Ahmed A. Ali, Konstantinos Kotopoulos, Vaiva Dabravolskaite, Drosos Kotelis, Vladimir Makaloski and Michel Joseph Bosiers in Journal of Endovascular Therapy

Supplemental Material

sj-jpg-2-jet-10.1177_15266028261424752 – Supplemental material for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Supplemental material, sj-jpg-2-jet-10.1177_15266028261424752 for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System by Daniel Becker, Georgios I. Karaolanis, Ahmed A. Ali, Konstantinos Kotopoulos, Vaiva Dabravolskaite, Drosos Kotelis, Vladimir Makaloski and Michel Joseph Bosiers in Journal of Endovascular Therapy

Supplemental Material

sj-jpg-3-jet-10.1177_15266028261424752 – Supplemental material for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System

Supplemental material, sj-jpg-3-jet-10.1177_15266028261424752 for Geometrical Analysis of Target Vessel Instability After FEVAR With Anaconda Stent-Graft System by Daniel Becker, Georgios I. Karaolanis, Ahmed A. Ali, Konstantinos Kotopoulos, Vaiva Dabravolskaite, Drosos Kotelis, Vladimir Makaloski and Michel Joseph Bosiers in Journal of Endovascular Therapy

Footnotes

Acknowledgements

None.

ORCID iDs

Daniel Becker

Georgios I. Karaolanis

Ahmed A. Ali

Vladimir Makaloski

Ethical Considerations

The study was approved by the cantonal ethical committee (BASEC-ID 2024-02142).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: MJB: Travel and proctoring for Cook Medical and Shockwave. VM: Travel and institutional research grants from and proctoring for Terumo Aortic.

Data Availability Statement

Raw data were generated at University Hospital Bern, Inselspital, Department of Vascular Surgery. Derived data supporting the findings of this study are available from Daniel Becker on request.

Supplemental Material

Supplemental material for this article is available online.

References

Katsargyris

Hasemaki

Marques de Marino

, et al. Editor’s choice—long term outcomes of the Advanta V12 covered bridging stent for fenestrated and branched endovascular aneurysm repair in 1 675 target vessels. Eur J Vasc Endovasc Surg. 2023;66(3):313–321.

Dossabhoy

Simons

Diamond

, et al. Reinterventions after fenestrated or branched endovascular aortic aneurysm repair. J Vasc Surg. 2018;68(3):669–681.

Gibello

Ruffino

Varetto

, et al. Current results of balloon expandable visceral stent-grafts in fenestrated endografting. J Cardiovasc Surg. 2020;61(1):37–46.

Oderich

Forbes

Chaer

, et al. Reporting standards for endovascular aortic repair of aneurysms involving the renal-mesenteric arteries. J Vasc Surg. 2021;73(1S):4S–52S.

Clough

Spear

Mougin

, et al. Midterm outcomes of BeGraft stent grafts used as bridging stents in fenestrated endovascular aortic aneurysm repair. J Endovasc Ther. 2022;30(4):592–599.

Mazroua

Pandya

Aloziem

, et al. Comparison of bridging stent graft type in fenestrated endovascular repair of abdominal aortic repair. J Vasc Surg. 2025;81(4):E5.

Becker

Fernandez Prendes

Stana

, et al. Outcome of the BeGraft bridging stent in fenestrated endovascular aortic repair in a high-volume single center and an overview of current evidence. J Endovasc Ther. 2025;32:1969–1980.

Von Elm

Altman

Egger

, et al. The Strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007;370(9596):1453–1710.

Pini

Giordano

Ferri

, et al. The Italian multicentre registry of fenestrated anaconda endografts for complex abdominal aortic aneurysms repair. Eur J Vasc Endovasc Surg. 2020;60(2):181–191.

10.

de Niet

Zeebregts

Reijnen

MMPJ

, et al. Outcomes after treatment of complex aortic abdominal aneurysms with the fenestrated Anaconda endograft. J Vasc Surg. 2020;72(1):25–35.

11.

Kotelis

Schleimer

Foldenauer

, et al. Operative and midterm outcomes of the fenestrated anaconda stent-graft in the endovascular treatment of juxtarenal, suprarenal, and type IV thoracoabdominal aortic aneurysms. J Endovasc Ther. 2016;23(6):930–935.

12.

Rödel

SGJ

Zeebregts

Meerwaldt

, et al. Incidence and treatment of limb occlusion of the anaconda endograft after endovascular aneurysm repair. J Endovasc Ther. 2019;26(1):113–120.

13.

Colgan

Bungay

Burfitt

, et al. Operative and 1-year outcomes of the custom-made fenestrated anaconda aortic stent graft-a UK multicenter study. Ann Vasc Surg. 2018;46:257–264.

14.

Midy

Becquemin

Mialhe

, et al. Results of the French multicentric study of ANACONDA fenestrated endografts in the treatment of complex aortic pathologies (EFEFA Registry). Ann Vasc Surg. 2017;43:151–165.

15.

Falkensammer

Taher

Uhlmann

, et al. Rescue of failed endovascular aortic aneurysm repair using the fenestrated Anaconda device. J Vasc Surg. 2017;66(5):1334–1339.

16.

Karaolanis

Kotopoulos

Jungi

, et al. Fenestrated anaconda endograft for the treatment of complex aortic aneurysms: systematic review and meta-analysis [published online ahead of print January 24, 2025]. J Endovasc Ther. doi:10.1177/15266028251313947.

17.

Kärkkäinen

Tenorio

Jain

, et al. Outcomes of target vessel endoleaks after fenestrated-branched endovascular aortic repair. J Vasc Surg. 2020;72(2):445–455.

18.

England

García-Fiñana

McWilliams

, et al. Multicenter retrospective investigation into migration of fenestrated aortic stent grafts. J Vasc Surg. 2015;62(4):884–892.

19.

Kandail

Hamady

XY.

Effect of a flared renal stent on the performance of fenestrated stent-grafts at rest and exercise conditions. J Endovasc Ther. 2016;23(5):809–820.

20.

Becker

Sikman

Ali

, et al. Analysis of target vessel instability in fenestrated endovascular repair (f-EVAR) in thoraco-abdominal aortic pathologies. J Clin Med. 2024;13(10):2898.

21.

Squizzato

Antonello

Forcella

, et al. Geometrical determinants of target vessel instability in fenestrated endovascular aortic repair. J Vasc Surg. 2022;76(2):335–343. doi:10.1016/j.jvs.2022.01.146.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.01 MB

0.16 MB

0.13 MB

0.34 MB