Feasibility and Safety of Sac Embolization Using N-Butyl Cyanoacrylate in Emergency Endovascular Aneurysm Repair for Ruptured Abdominal Aortic Aneurysms or Isolated Iliac Artery Aneurysms

Abstract

Purpose:

To evaluate the feasibility and safety of sac embolization with N-butyl cyanoacrylate (NBCA) in emergency endovascular aneurysm repair (EVAR) for ruptured abdominal aortic aneurysm (AAA) and iliac artery aneurysm (IAA) in comparison to EVAR without sac embolization.

Materials and Methods:

Between February 2012 and December 2019, among 44 consecutive patients with ruptured AAA or IAA, 29 underwent EVAR. Of these, 22 patients (median age 77.5 years; 18 men) had concomitant sac embolization using NBCA; the remaining 7 patients (median age 88 years; 6 men) underwent EVAR without sac embolization and form the control group. The technical success, clinical success (hemodynamic stabilization), procedure-related complications, and mortality were compared between the groups.

Results:

All EVAR procedures and embolizations were successful. The clinical success rates in the NBCA and control groups were 95% (21/22) and 71% (5/7), respectively (p=0.14). There was no complication related to the procedure. Type II endoleak occurred in 4 of 21 patients (19%) in the NBCA group vs none of the control patients. One patient (5%) died in the NBCA group vs 3 (43%) in the controls (p=0.034).

Conclusion:

Sac embolization using NBCA in emergency EVAR appears to be feasible and safe for ruptured AAA and IAA.

Keywords

abdominal aortic aneurysm emergency endovascular aneurysm repair glue hemodynamic stabilization iliac artery aneurysm N-butyl cyanoacrylate sac embolization ruptured aneurysm

Introduction

Endovascular aneurysm repair (EVAR) is a valuable treatment option for patients with a ruptured abdominal aortic aneurysm (AAA) or iliac artery aneurysm (IAA).^1-4 However, a drawback of EVAR during follow-up is endoleaks.^5,6 Type II is the most common endoleak and is related to retrograde flow via collaterals, mostly in the lumbar arteries and inferior mesenteric artery.⁷ In ruptured AAA and IAA, when a type II endoleak occurs, bleeding may persist from the rupture site.⁸ Several authors have reported that sac embolization using embolic materials such as coils and thrombin during elective EVAR was useful in preventing type II endoleaks.^9-16

Several years ago, Koike et al¹⁷ reported an initial experience with embolization of ruptured AAAs using N-butyl cyanoacrylate (NBCA) in 3 emergency EVAR cases.¹⁷ At that time our group hypothesized that sac embolization using NBCA could be useful not only to prevent type II endoleaks but also to seal the rupture site. Herein we report our experience with NBCA sac embolization during emergency EVAR for ruptured AAA and IAA and compare the outcomes to emergency EVAR without sac embolization.

Materials and Methods

Study Design and Patient Sample

Of 44 consecutive patients with ruptured AAA or IAA treated at our hospital between February 2012 and December 2019, 29 patients underwent emergency EVAR. Among them, 22 patients (median age 77.5 years; 18 men) had concomitant sac embolization using NBCA; the remaining 7 EVAR patients (median age 88 years; 6 men) did not have sac embolization and constitute the control group (Figure 1).

In all patients, rupture of the aneurysm was confirmed by computed tomography (CT), and the suitability for EVAR was then decided by consensus of an interventional radiologist and a vascular surgeon based on anatomical information such as the proximal neck length, access vessel tortuosity, and the presence of a shaggy aorta. Use of NBCA sac embolization was at the discretion of the operators because not all were familiar with NBCA.

This retrospective study was approved by the Institutional Review Board (approval number 60-18-0156).

Emergency EVAR and Sac Embolization

All 29 EVAR cases were approached from surgically exposed femoral arteries under local (n=27) or general anesthesia (n=2). In all cases, anticoagulation was not performed to prevent further bleeding. Standard EVAR was performed across the aortoiliac bifurcation in all but 1 patient with an internal IAA; in this case the stent-graft was limited to the ipsilateral iliac artery. The main body of the stent-graft [Excluder (Gore Medical, Flagstaff, AZ USA) or Endurant (Medtronic, Minneapolis, MN, USA)] was advanced into the abdominal aorta and deployed below the renal arteries. An Excluder was used for the limb stent-graft in all cases. After the limb stent-graft was deployed, the proximal neck, docking zone, and iliac legs were molded with a balloon.

In the cases with sac embolization, the contralateral limb was placed in position, but before deployment a 4-F cobra catheter was inserted through the same sheath (upsized by one size, eg, from 16 to 18 F) and positioned at the rupture site. The contralateral limb was then deployed, and all junctions were balloon molded. NBCA was mixed with iodized oil at a proportion of 20% or 25%, and sac angiography was performed to identify the site of extravasation. The cobra catheter was positioned at the site and NBCA was injected until sealing was documented on angiography. When there was no extravasation seen, the NBCA was injected near the rupture site according to the preoperative CT. The 4-F cobra catheter was then immediately removed, and the iliac limb on the same side was balloon molded.

Procedure Variables

Data were extracted from the medical records and/or review of imaging studies to characterize the ruptured aneurysm and determine the type of hematoma expansion, the Glasgow aneurysm score, the Hardman index, and the Edinburgh ruptured aneurysm score. All images were interpreted by 2 radiologists with >10 years of experience in diagnostic and interventional radiology; any discrepancies were resolved by consensus. Data were also collected on preoperative anemia, shock, coagulopathy, amount of blood transfusion, presence of the abdominal compartment syndrome, and length of stay.

Expansion of the hematoma in ruptured AAA patients was evaluated according to the Fitzgerald classification,¹⁸ in which type 1 included intramural bleeding or a small hematoma; type 2 was a hematoma below the renal arteries, including the pelvis; type 3 comprised a hematoma extending above the renal arteries and into the pelvis; and type 4 indicated free blood in the peritoneal cavity. Ruptured IAA was categorized as slight (intramural bleeding or a small hematoma), mild (bleeding limited to the retroperitoneal cavity), or severe (blood penetrating the peritoneal cavity).

The Glasgow aneurysm score was calculated using the following formula: risk score = age in years + 17 (for shock) + 7 (for myocardial disease) + 10 (for cerebrovascular disease) + 14 (for renal disease). Myocardial disease was previously documented myocardial infarction, ongoing angina, or both. Cerebrovascular disease referred to all grades of stroke, including transient ischemic attacks. Renal disease was any history of chronic or acute renal failure, urea >20 mmol/L, or creatinine >150 μmol/L at presentation.¹⁹

The Hardman Index includes 5 preoperative variables: age >76 years, serum creatinine >190 μmol/L, hemoglobin <9 g/dL, myocardial ischemia on electrocardiography, and a history of loss of consciousness after hospital arrival.²⁰ The Edinburgh ruptured aneurysm score derives from 3 preoperative variables: hemoglobin <9 g/dL, in-hospital Glasgow Coma Scale <15, and in-hospital blood pressure <90 mm Hg.²¹

Anemia was defined by a hemoglobin level <12.0 g/dL.²² Hemorrhagic shock was indicated by a systolic blood pressure ≤70 mm Hg or systolic blood pressure 71 to 90 mm Hg with a heart rate ≥108 bpm.²³ Coagulopathy was defined as an international normalized ratio ≥1.5 and/or platelets ≤50×10⁹/L.²⁴

Outcomes

The technical success, clinical success, procedure-related complications, and mortality were compared between the groups. Technical success was defined as completion of the procedure. Clinical success referred to hemodynamic stabilization without evidence of further bleeding. Complications prolonging hospitalization or causing permanent adverse sequelae or death were classified as major complications, and the remaining complications were considered to be minor. Complications were recorded and graded according to the Common Terminology Criteria for Adverse Events (version 4.0).²⁵

Statistical Analysis

Continuous data are presented as the median (minimum–maximum); categorical data are given as the number. Differences between groups were analyzed using the Fisher exact test for categorical data and the Mann-Whitney U test for continuous variables. A p<0.05 was considered significant. All statistical analyses were carried out using GraphPad Prism (GraphPad Software, Inc., La Jolla, CA, USA).

Results

EVAR was successfully completed in all 29 cases (Table 1). In 21 of 29 cases, an aortic occlusion balloon catheter was percutaneously inserted before stent-graft placement to control blood pressure. Transcatheter arterial embolization (TAE) of the internal iliac artery was performed before EVAR in 9 of the NBCA group and in 3 of the 7 control cases.

Table 1.

Details of the Patients Undergoing EVAR With vs Without Sac Embolization.^a

	With Embolization (n=22)	Without Embolization (n=7)
Age, y	77.5	88
Men	18	6
AAA / CIAA / IIAA	19 / 1 / 2	7 / 0 / 0
Aneurysm size, mm	65 (33–94)	64 (56–96)
Hematoma expansion type^b	1 (1), 2 (2), 3 (14), 4 (2); mild (3)	2 (1), 3 (5), 4 (1)
Anemia	19	7
Coagulopathy	5	1
Shock	12	5
Glasgow aneurysm score	82.5 (61–97)	91 (69–109)
Hardman index	0 (2), 1 (7), 2 (11), 3 (2)	0 (1), 1 (1), 2 (4), 3 (1)
Edinburgh ruptured aneurysm score	0 (8), 1 (7), 2 (5), 3 (2)	0 (1), 1 (3), 2 (3)
Stent-graft, Excluder / Endurant	12 / 10	4 / 3
NBCA dose, mL (strength)	4 (20%), 5 (25%)	NA
Procedure time, min	108.5 (60–259)	90 (80–130)
Technical success	22	7
Follow-up, mo	14 (2–58)	6.5 (0–31)

Abbreviations: CIAA, common iliac artery aneurysm; EVAR, endovascular aneurysm repair; IIAA, internal iliac artery aneurysm; NA, not applicable; NBCA, N-butyl cyanoacrylate.

Continuous data are presented as the median (minimum–maximum); categorical data are given as the number.

After the procedure, hemodynamic stabilization was achieved without evidence of further bleeding in 21 of 22 patients (95%) in the NBCA group (Figure 2). One patient with shock, anemia, and coagulopathy had cardiopulmonary arrest that necessitated cardiopulmonary resuscitation before EVAR. However, the hemodynamic condition of this patient was unstable and he died 6 hours after EVAR. In the control group, 5 of 7 patients (71%) were stabilized after the procedure; 2 died intraoperatively.

After EVAR, 4 type II endoleaks (19%) were detected at follow-up CT in the NBCA group (Figure 3) vs no endoleak in the control group. Comparing these 4 cases with type II endoleak to the remaining 18 NBCA cases (Table 2), no significant differences were found in the outcomes between the subgroups. Two of the 4 type II endoleaks required TAE due to sac enlargement.

Table 2.

Comparison of Cases Without vs With Type II Endoleak.^a

	No Endoleak (n=18)	Endoleak (n=4)	p
Clinical success	17	4	>0.99
Complications	0	0	>0.99
Blood transfusion, mL	1540 (0–4200)	1400 (840–1680)	0.71
Length of stay, d	12.5 (1–54)	10 (9–35)	0.85
Abdominal compartment syndrome	1	0	>0.99
Shrinkage rate, %	18 (4–41)	11 (0–31)	0.4
Mortality	1	0	>0.99

Continuous data are presented as the median (minimum-maximum); categorical data are given as the number.

Regarding clinical outcomes, 21 patients of the NBCA group were alive with a median follow-up of 14 months (range 2–58). Of the 5 surviving control patients, 1 died 3 months after EVAR due to infection. The 4 survivors have been observed over a median follow-up of 6.5 months (range 1–31). Comparing the outcomes between the NBCA and control groups (Table 3), there was no difference in any of the examined outcome variables except for mortality. Notably, the NBCA group had fewer deaths (1, 5%) vs the control group (3, 43%; p=0.034).

Table 3.

Comparison of the Sac Embolization and Control Groups.

	Embolization (n=22)	No Sac Embolization (n=7)	p
Clinical success	21	5	0.14
Complications	0	0	>0.99
Type II endoleak	4	0	0.55
Blood transfusion, mL	1400 (0–4200)	1400 (240–3640)	0.61
Length of stay, d	11 (1–54)	11 (1–22)	0.59
Abdominal compartment syndrome	1	0	>0.99
Shrinkage rate, %	21 (0–41)	15 (2–36)	0.67
Mortality	1	3	0.034

Continuous data are presented as the median (minimum-maximum); categorical data are given as the number.

Discussion

In this study, EVAR with sac embolization using NBCA was clinically successful in stabilizing patients with ruptured AAA and IAA, although over half had shock and a quarter had coagulopathy. In the literature, significant mortality ranging between 20% and 70% has been reported with the surgical treatment of ruptured AAA.^26-30 By comparison, a 21% mortality for emergency EVAR of ruptured AAA was reported in a 2008 meta-analysis.³¹ More recently, Mayer et al³² observed 27% mortality in a 2-center 14-year experience with EVAR for ruptured AAA. While the mortality rate in the current study was considerably lower, suggesting that NBCA sac embolization may improve outcomes, the patient sample was small and most of the patients were referred from neighboring areas, which did not prolong transport to the hospital.

Type II endoleak is an important issue in ruptured AAA. Although type II endoleak has low pressure due to retrograde collateral flow, it may induce persistent bleeding through the rupture site, as witnessed by Ogawa et al.⁸ Even though the NBCA procedure could not prevent type II endoleak completely, hemodynamic stabilization was achieved regardless in our cases. Since NBCA was injected at the rupture site, we believe the glue can seal the rupture site and prevent persistent bleeding even in the presence of a type II endoleak. On the other hand, Quinn et al³³ reported a lower rate of type II endoleak in emergency EVAR vs elective cases. They considered it might be due to a lack of surveillance because patients undergoing emergency EVAR were poorly followed due to referral from remote areas or to hemodynamic collapse secondary to aneurysm rupture and blood loss. In our cases, hemodynamic collapse was prevented, so the rate of type II endoleak was slightly high.

Difficulties have been reported with NBCA^34-36 because the liquid embolic material may induce non-target embolization of the spinal cord. Therefore, before injecting NBCA, sac angiography must be performed to confirm no perfusion of the spinal artery. Furthermore, the catheter needs to be removed immediately after NBCA embolization because the catheter tip may adhere to the vessel wall due to the rapid polymerization of NBCA. When removing the catheter, a cast of NBCA may adhere to the tip of the catheter. If there is a space between the arterial wall and contralateral limb stent-graft, the NBCA cast may migrate to the external iliac artery. Thus, molding of the contralateral stent-graft needs to be performed as a preventive step. In our procedures, the 4-F catheter for NBCA injection was inserted into the sheath containing the contralateral limb. However, if the femoral artery is large enough, upsizing the sheath for the contralateral limb would be possible and a 4-F sheath can be inserted, which may be a useful support for the 4-F catheter and any second catheter insertion.

Patients with ruptured AAA or IAA may be in a coagulopathic state due to the loss of a large volume of blood, and the outcomes may be worse than in patients without coagulopathy. However, the polymerization of NBCA starts immediately upon contact with anions, and it makes a permanent cast of the vessel, independent of inherent coagulation.⁴

Regarding the amount and concentration of NBCA in this procedure, Koike et al.¹⁷ used 1 mL of a 50% mixture of NBCA and iodized oil. In our experience, we had difficulty delivering the catheter to the rupture site; thus, we had to inject a considerable amount of NBCA to seal the rupture. NBCA may adhere to the catheter under these conditions, so we used a 20% or 25% NBCA to oil mixture. As a result, the catheter was removed in all cases without adhesion of NBCA. Thus, this low concentration appears to be safe.

Preoperative TAE of the lumbar arteries and inferior mesenteric artery has been reported to be successful in decreasing the incidence of type II endoleaks.^37,38 Since this type of TAE may be very challenging and time consuming, it may be difficult to perform under emergency conditions. On the other hand, sac embolization using NBCA is a relatively quick procedure that may be more appropriate for ruptures. However, the present results demonstrated that sac embolization using NBCA did not prevent type II endoleaks, and thus follow-up examinations are important for detecting endoleaks and the need for additional TAE.

NBCA was used in our study, but ethylene vinyl alcohol copolymer mixed with dimethyl sulfoxide and tantalum powder for radiopacity (Onyx) is a liquid embolic material that has been used for treatment of type I and type II endoleak.^39,40 The most important difference from NBCA is that Onyx is a non-adhesive material, so one does not have to pay attention to adhesion of the catheter. However, it is not covered by medical insurance in our country. One disadvantage of Onyx is that the tantalum powder leaves artifacts on the CT image, so follow-up examination should be performed with ultrasonography.

Coils and thrombin have also been used for sac embolization in elective EVAR.^9-16 However, thrombin is also not covered with medical insurance in our country. Coils are a useful material for embolotherapy in general, but it may induce severe artifacts on CT images. Besides, coils may not work in coagulopathy, so in our opinion NBCA is an appropriate material for sac embolization during emergency EVAR for ruptured aneurysm.

The present study was limited by its retrospective study and small sample size. There was no single operator performing EVAR, and the procedure was not completely standardized due to the variability of the technique according to individual operator preferences. Therefore, further studies are needed using a larger study cohort.

Conclusion

Sac embolization using NBCA in emergency EVAR for ruptured AAA and IAA appears to be feasible and safe.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

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

ORCID iDs

Shota Ohba

Masashi Shimohira

Yosuke Nakai

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