Mid-Term Outcomes of the Double-Barrel Technique for Patients Who Are Unfit for Standard Endovascular Aortic Aneurysm Repair

Abstract

Background: Endovascular aortic aneurysm repair (EVAR) is a commonly used treatment for abdominal aortic aneurysms (AAAs), but anatomical complexities limit its application in certain cases. Objective: This study evaluates the mid-term outcomes, referring to a follow-up period with a mean of 29.9 ± 24.1 months (approximately 1–5 years), of a novel double-barrel technique that employs overlapping tubular stent grafts to address these challenges. Methods: A retrospective analysis was conducted on seven patients treated with this technique from May 2014 to February 2023. Patients had narrow and short proximal necks, inadequate landing zones, or required re-do procedures. Results: The double-barrel technique achieved technical success in 85.7% of cases with zero mortality. Patients had an average hospital stay of 11.9 ± 10.0 days and attended follow-up for a mean of 29.9 ± 24.1 months. Minimal complications and no significant adverse events were reported. Conclusions: These findings suggest that the double-barrel technique is a cost-effective and viable alternative for anatomically complex cases where standard EVAR is unsuitable. While promising mid-term outcomes were observed, further studies with larger cohorts are necessary to confirm its long-term effectiveness and broader applicability.

1. Introduction

Endovascular aortic aneurysm repair (EVAR) is considered as a beneficial treatment method for abdominal aortic aneurysms (AAAs), as it offers many more advantages compared to open surgical repair [1,2]. Recently, EVAR has been widely performed due to advancements in graft materials and techniques. Although its outcomes have improved, concerns remain about its long-term efficacy [3,4]. Additionally, efforts are being made to keep up with the growing need for re-interventions [5,6] or for challenging neck anatomies [7,8]. Instead of relying on a single established treatment approach, novel devices and patient-specific solutions have been proposed [9,10]. Obstacles in performing re-do EVAR include the difficulty in securing a proximal margin for renal artery salvage and avoiding limb jailing due to the previous graft, which makes it impossible to insert a new bifurcated graft for standard EVAR.

Meanwhile, an increasing trend in endovascular treatment for iliac artery aneurysms has demonstrated promising outcomes [11,12]. However, for isolated iliac artery aneurysms, a challenge in treatment may arise if there is no proximal or distal landing zone available to anchor a graft [13]. And even if we plan for the endovascular repair of an iliac artery aneurysm not by using solely a tubular graft but using EVAR, the aortic diameter and distal landing zone anatomy may not suitable for deploying it.

We attempted to develop a cost-effective and relatively straightforward approach for use in situations where standard EVAR was not feasible, as described in aforementioned situations. This study presents a single-center study of the mid-term outcomes of patients who were treated with a double-barrel aorto-iliac stent graft (double-barrel technique), which allowed the use of the existing stent graft product, in cases of patients unfit for standard EVAR.

2. Materials and Methods

2.1. Patient Selection

This is a single-center, retrospective study. A total of 7 patients who were treated with a double-barrel technique were identified. These patients were unable to receive a standard EVAR due to various reasons, such as the aortic neck diameter being outside the range of 19 to 32 mm, the proximal neck length not being secured due to the previous graft in cases of re-do EVAR, or the absence of an adequate landing zone for an isolated common iliac artery aneurysm with a size of 25 mm or larger. This study protocol was approved by the institutional review board of Gachon University Gil Medical Center.

2.2. Procedure and Techniques

As shown in Figure 1, the first step was a retrograde femoral approach through both common femoral arteries and the simultaneous deployment of two tubular-type main bodies with the same diameter over a guide wire and through a delivery device. Then, balloon catheters of the same size were used to sequentially perform ballooning from the proximal to the distal landing zone in the same segment, with the balloons in contact. In cases where further limb extension was required, we performed embolization of the ipsilateral internal iliac artery. The decision on internal iliac artery salvage or embolization followed the same considerations as in standard EVAR procedures, and thus, we will not provide additional discussion on this aspect. This approach ensured proper distal sealing and limb extension when necessary. Finally, completion arteriography was performed to confirm the graft deployment status and the presence of any leakage.

Two methods were employed to calculate the graft diameter via the double-barrel technique: the isoperimetric equation [14] and the geometrical calculation of arc length [15]. The isoperimetric inequality equation states that among all closed curves in the plane of a fixed perimeter, a circle maximizes the area of its enclosed region:

$$R^{\prime }\ge \sqrt{1.44R^2-r^2}$$

(1)

where $R^{\prime }$ is the radius of the one of the two stent grafts, R is the radius of the native aorta or previous installed stent graft, and r is the radius of the other stent graft. $R^{\prime }$ should be same as r in the double-barrel technique; the final equation is given below:

$$R^{\prime }=r,R^{\prime }\approx 0.8485R$$

(2)

The geometrical calculation of arc length states that the two stent grafts change from circular to D-shaped when deployed in a parallel fashion, but their perimeter does not change; however, the total area changes:

$$C=2\pi r=2R+{\displaystyle \frac{2\pi R}{2}}$$

(3)

where C is the circumference, R is the radius of the previously installed stent graft or native aorta, and r is the radius of the stent graft. The two stent grafts should be the same in the double-barrel technique; the final equation is given below:

$$r\approx 0.8183R$$

(4)

Using these two equations, we chose a commercialized endograft with a diameter most closely approximating the calculated number. As for the length of the stent graft, its selection was determined on a case-by-case basis. The primary considerations were ensuring sufficient lesion coverage and securing an adequate landing zone, while also taking into account the available stent graft configurations.

2.3. Definitions and Statistical Analysis

Technical success was defined as successful deployment as intended with the preservation of antegrade flow to the iliac arteries and without any endoleak. The demographic data and anatomical details of the patients were recorded based on the most recent assessment prior to treatment with the double-barrel technique. Complications were evaluated at least 6 months after the treatment. All follow-up assessments were performed using triple-phase computed tomography (CT) to thoroughly evaluate the presence of complications.

The collected clinical information was presented using appropriate statistical measures. For continuous variables, the mean ± standard deviation was used. Categorical variables were expressed as the number and percentage. This approach allowed for clear and concise representation of the clinical data in a standardized format.

3. Results

This study included all patients who underwent the double-barrel technique in a single institution from May 2014 to February 2023. The primary inclusion criterion was anatomical unsuitability for standard EVAR, such as a narrow or short proximal neck, an inadequate landing zone, or the need for a re-do procedure. There were no predefined exclusion criteria based on age, comorbidities, or previous EVAR complications. A total of seven patients participated in this study, with an average age of 74.1 ± 4.0 years. Among them, four patients (57.1%) were female (

Table 1. Demographic data and comorbidities.

	Total Patients (n = 7)
Age (years)	74.1 ± 4.0
Gender
Male	3 (42.9%)
Female	4 (57.1%)
Height (cm)	158.8 ± 9.4
Weight (kg)	58.4 ± 16.4
Cigarette smoking	1 (14.3%)
Serum Creatinine level (mg/dL)	0.8 ± 0.2
Hypertension	6 (85.7%)
Diabetes Mellitus	3 (42.9%)
Congestive heart failure	0 (0%)
Cerebrovascular accident	2 (28.6%)
Coronary artery disease	0 (0%)
Chronic obstructive pulmonary disease	0 (0%)

Data presented as mean ± standard deviation or number (%, percentage).

). The average height was 158.8 ± 9.4 cm, and the average weight was 58.4 ± 16.4 kg. There were no obese patients within the study population. Only one patient (14.3%) was identified as a current smoker, while all other patients were non-smokers. The serum creatinine levels of all patients were within the normal range. Hypertension was found in six patients (85.7%), diabetes mellitus in three patients (42.9%), and cerebrovascular accident in two patients (28.6%). There were no patients with congestive heart failure, coronary artery disease, or chronic obstructive pulmonary disease in the study population.

Preoperative diagnoses and indications for performing the double-barrel technique are summarized in

Table 2. Preoperative clinical data.

	Total Patients (n = 7)
Previous endovascular treatment	3 (42.9%)
Diagnosis
Infrarenal AAA	4 (57.1%)
CIA aneurysm	4 (57.1%)
Ruptured aneurysm	2 (28.6%)
Endoleak	3 (42.9%)
Type Ia	1 (14.3%)
Type III	1 (14.3%)
Endotension	1 (14.3%)
Indications for double-barrel stent graft
Re-do endovascular treatment	3 (42.9%)
Small proximal neck diameter (<19 mm)	3 (42.9%)
CIA aneurysm without landing zone	2 (28.6%)
Short proximal neck length (<10 mm)	1 (14.3%)

Data presented as number (%, percentage). AAA—abdominal aortic aneurysm; CIA—common iliac artery.

. This table reflects the diagnoses that directly led to the decision for the procedure, specifically the patient’s condition immediately before surgery. Other prior complications or issues that had already been addressed before the decision to proceed with double-barrel EVAR are not included. A total of three patients (42.9%) had previously received endovascular treatment. Specifically, two patients had undergone EVAR, while one patient had previously undergone stent graft insertion for a common iliac artery (CIA) aneurysm. Based on the preoperative diagnoses, it was found that four patients (57.1%) had an infrarenal abdominal aortic aneurysm, and two out of those four patients had ruptured aneurysms. Additionally, four patients (57.1%) were diagnosed with a CIA aneurysm. Out of the three patients who had previously undergone endovascular treatment, their diagnoses were as follows: one was diagnosed with endoleak type Ia, another with type III, and the third with endotension. In the context of indications for performing the double-barrel technique, the following observations were made: Three patients (42.9%) fell into the re-do case category, having previously undergone endovascular treatment. One patient (14.3%) exhibited a proximal neck length of less than 10mm, while three patients (42.9%) exhibited a proximal neck diameter below 19mm. Within this subset of three patients, two individuals presented concurrent CIA aneurysms, along with an inadequate landing zone.

Table 3. Preoperative anatomic details.

Patient Number	ØAo (mm)	ØCIA (Rt/Lt) (mm)	ØEIA (Rt/Lt) (mm)	Proximal Neck (L1) (mm) (Length/Diameter)	L1 + L2 (mm)
1	64	11/12	9/8	7/26	127
2	60	14/12	6/5	40/30	40
3	97	13/11	10/10	28/20	37
4	n/a	50/n/a	n/a	n/a/n/a	n/a
5	35	12/11	8/8	35/18	98
6	18	13/11	8/8	n/a/18	81
7	18	31/74	9/9	n/a/18	80

Ø—diameter; Ao—abdominal aorta; CIA—common iliac artery; EIA—external iliac artery; Rt—Right; Lt—Left; L1—length of proximal neck; L2—length of aneurysm.

presents the measurement values of the abdominal aorta, iliac arteries, and proximal neck length/diameter, and the combined value of the proximal neck and aneurysm lengths (L1 + L2) based on preoperative CT scans. Unfortunately, for one patient, the measurement values based on the preoperative CT scan were not available due to missing data. Even in cases where patients did not have an abdominal aortic aneurysm (AAA), such as patients 5, 6, and 7, the proximal neck diameter was still measured near the renal artery and recorded. These measurements were utilized in the calculation of the double-barrel graft diameter. We also recorded the combined value of proximal neck and aneurysm length, denoted as L1 + L2. For patients with isolated aneurysms or re-do cases, we measured the length from the renal artery to the aortic bifurcation or graft bifurcation, respectively.

Table 4. Calculated device diameter and used devices.

Patient Number	ØCalculated Double-Barrel Graft (mm)		Devices Used for Double-Barrel Aorto-Iliac Stent Graft
	Arc Length Method	Isoperimetric Method
1	21.3 (20.7 *)	22.1	Medtronic (Endurant) $20\times 20\times 82$
2	24.5	25.5	Medtronic (Endurant) $23\times 14\times 102$
3	16.4	17.0	Medtronic (Endurant) $16\times 16\times 93$
4	n/a	n/a	Gore (Excluder) $12\times 14\times 120$ (Rt), $12\times 10\times 100$ (Lt)
5	14.7	15.3	Gore (Excluder) $16\times 14\times 100$
6	14.7	15.3	Medtronic (Endurant) $16\times 10\times 156$
7	14.7	15.3	Medtronic (Endurant) $16\times 16\times 156$

Ø—diameter; Rt—Right; Lt—Left. Device configuration: manufacturer proximal diameter (mm)–distal diameter (mm) × length (mm). * Calculated considering chimney graft (6 mm).

presents the values of graft diameter measured using the Arc length and isoperimetric methods, as mentioned earlier. Additionally, it includes the actual products used in the double-barrel technique. In cases where only one product is indicated, it signifies the use of the same product for performing the double-barrel technique. However, in instances where slightly different products were used, with variations in distal diameter and length, the right- and left-side products are specified separately in the table. In the case of patient number 1, a chimney graft with a diameter of 6mm was inserted. When calculating using both methods, the values presented initially did not consider the chimney graft. The additional values listed under the Arc length method represent the calculation excluding the area of the chimney graft.

The technical success rate was 85.7%, as indicated in

Table 5. Perioperative and mid-term outcomes.

	Total Patients (n = 7)
Technical success	6 (85.7%)
30-day mortality	0 (0%)
6-month mortality	0 (0%)
Length of hospital stay (days)	11.9 ± 10.0
Follow-up period (months)	29.9 ± 24.1
Complications
Limb occlusion	1 (14.3%)
Endoleak	0 (0%)
Device migration	0 (0%)
Access complication	0 (0%)
Sac enlargement	0 (0%)
Aneurysm rupture	0 (0%)

Data presented as mean ± standard deviation or number (%, percentage).

. This rate accounts for the presence of cases where limb occlusion was observed immediately after surgery which was corrected with additional intervention. The 1-month and 6-month mortality rates were both 0%. The average length of hospital stay was 11.9 ± 10.0 days, and the follow-up period lasted for 29.9 ± 24.1 months and during that period showed zero mortality. We enrolled patients starting from 2014, but the follow-up period turned out to be shorter than expected. This is because we calculated the follow-up period based on the most recent medical records, and due to patients experiencing follow-up loss in the middle, the period ended up not being as long as anticipated. Within the follow-up period after surgery, apart from one patient of postoperative stent graft kinking, there were no any other complications observed, such as endoleak, graft migration, access complication, sac enlargement, or aneurysm rupture.

4. Discussion

Endovascular aneurysm sealing (EVAS) is proposed for cases that deviate from the instructions for the use of standard EVAR. This involves inserting two balloon-expandable stent grafts, and then filling the aneurysm sac with a polymer solution through an endobag [16]. The double-barrel technique that we implemented shares a somewhat similar concept. It involves deploying two tubular stent grafts in an overlapping manner and extending them from the abdominal aorta to the iliac limbs without filling the aneurysmal sac.

In EVAR, the feasibility of utilizing standard endograft is contingent on the products available from different manufacturers or countries and their suitability based on anatomic requirements. Typically, assessments are made by measuring the anatomic configurations of the proximal aortic neck, aortic bifurcations, and iliac arteries to evaluate their viability for the procedure. According to the instructions for use of various manufacturers for proximal aortic neck anatomy configuration in EVAR procedures, the following criteria need to be met: the neck diameter should fall within the range of 19 mm to 32 mm, the proximal neck length should be 10 mm or more, and the angle of the neck should be within the range of 45 to 60 degrees. When facing challenging proximal aortic neck anatomy, several alternative techniques that are often attempted are fenestrated endovascular aneurysm repair (FEVAR) and chimney endovascular aneurysm repair (chEVAR) [17,18]. But these options are currently unavailable in our region (South Korea). And another important anatomic configuration is the combined length of the proximal neck and aneurysm (L1 + L2). This can predict potential scenarios where limb jailing could occur. In the case of re-do procedures, it was expected that this length might not be sufficient for inserting a new bifurcated graft. Additionally, for patients 6 and 7, even with the use of the shortest graft (Gore Excluder, 70 mm) among the available options we had, limb jailing could occur. Research papers have reported short- to mid-term outcomes that closely align with those presented in this study [19,20,21]; however, due to the intricate structure of such grafts, there remains a concern that they might incur more complications than the double-barrel technique.

Common iliac aneurysms are the second most common type following AAAs and are generally recommended for treatment when their size exceeds 3 cm. EVAR has shown comparable or even superior outcomes to open surgical repair [22,23] in treating these patients. Recently, EVAR has been increasingly favored over open surgery as the preferred treatment approach. Mizoguchi et al. [24] treated CIA aneurysms with the double D technique, as they named it, which is also similar to our double-barrel technique except that it requires using the proximal aortic cuff. Meanwhile, the patients with common iliac aneurysms we treated had abdominal aortic diameters slightly smaller than the recommended size for standard EVAR, measuring 18 mm. Furthermore, some patients lacked suitable landing zones for the conventional EVAR procedure.

As the number of initial EVAR procedures increases, the need for re-do EVAR is expected to rise in the future [25]. This expectation arises due to potential complications like aneurysm growth, endoleak, and other factors that may necessitate additional intervention or management over time. One of the major challenges in re-do EVAR, especially when inserting the bifurcated main body within the previously placed main body, is the difficulty in simultaneously achieving both the salvage of renal arteries and the deployment of the distal limbs. Careful planning and consideration of alternative techniques are necessary to overcome this limitation.

The patients in this study appeared to have a relatively low surgical risk, so exploring the possibility of open surgical repair could be another option. However, open surgical repair can be a difficult option and has a prolonged operation time, which may hinder patients’ recovery. In our region (South Korea), devices like chimney grafts and the EVAS system are not available for use. While other commercial devices exist, their off-label use is often restricted due to economic and regulatory constraints. Therefore, in such cases, the double-barrel technique serves as a pragmatic and viable alternative. So, if considering the double-barrel technique as an endovascular treatment option, utilizing commercially and practically available devices can achieve cost-effectiveness. Furthermore, due to its relatively straightforward procedure, it can contribute to early patient recovery as well. Based on the findings here, during an average follow-up period of approximately 29 months, no significant complications were observed except for a single case of postoperative stent graft kinking. Importantly, this complication was promptly addressed and resolved. Therefore, considering its favorable mid-term outcomes, the double-barrel technique may be regarded as a safe and effective option for endovascular treatment in patients with a small proximal neck, common iliac aneurysms lacking an adequate landing zone, and cases requiring re-do EVAR. But there are no specific indications for the procedure, and details regarding procedural aspects have not been discussed. Moreover, there is a lack of guidance on additional treatment options based on the occurrence of complications like endoleak or gutter leakage because, despite selecting patients over a period of several years, the number of patients who underwent this procedure was extremely limited. Even so, if it were to occur, we could consider options like embolization. However, as of now, there have been no occurrences, and we have not attempted it, so some more time may be required before we can assess its feasibility. While our mid-term results demonstrate the feasibility and safety of this technique, further extended observation is necessary to evaluate long-term complications such as graft migration, endoleaks, and aneurysm rupture.

In this study, we shared our experience with cases that were outside of the IFU where the double-barrel technique was applied. Our analysis confirmed that these cases had some common indications, such as proximal neck issues or re-do procedures, and we hope that this study will serve as a foundation for future patients facing similar situations. However, this study is limited by its small sample size, which lacks statistical power and reduces generalizability. Additionally, its retrospective nature introduces potential selection bias, and the heterogeneity in patient characteristics makes drawing definitive conclusions difficult. Thus, our findings should be viewed as an alternative option for complex cases rather than a definitive guideline. Nonetheless, they may provide useful insights for clinicians facing similar challenges. With more cases reported of additional attempts by various operators in different settings, the double-barrel technique may become a reliable option in the near future.

5. Conclusions

The double-barrel aorto-iliac stent graft insertion technique may provide patients who are unfit for standard EVAR with an alternative option for treatment, but it requires long-term observation and greater patient involvement to be established in a reliable manner.