Direct sac puncture versus transarterial embolization of type II endoleaks: An evaluation and comparison of outcomes

Abstract

Purpose

To determine the outcomes of type II endoleak embolization with aneurysm sac obliteration and whether the approach – direct sac puncture or transarterial – affects outcome.

Methods

A retrospective review of patients who underwent endovascular aneurysm repairs and subsequent type II endoleak embolization over 10 years was performed. Twenty-three patients (median age: 73 years, range: 40–88 years) underwent 35 embolizations. Embolization was performed with the goal of obliterating both the endoleak sac and feeding vessels. Embolization agents used include cyanoacrylate glue only (48%), glue and coils (36%), coils only (13%), and other (3%).

Results

Mean follow-up was 21.8 months. Patients underwent an average of 1.5 embolizations, with 35% requiring more than one. Technical success rate was 89%. Freedom from aneurysm sac expansion was achieved in 91%. Freedom from type II endoleak was accomplished in 70%. There were no ruptured aneurysms during the follow-up period. Direct sac puncture and transarterial approaches had similar incidences of aneurysm sac growth (p = 0.74), persistent type II endoleak (p = 0.32), and complications (p = 0.64). However, direct sac puncture had significantly shorter fluoroscopy (p < 0.001) and total procedure times (p < 0.001) than transarterial embolizations.

Conclusion

Direct sac puncture and transarterial embolization of type II endoleak with aneurysm sac obliteration are similarly effective for the prevention of aneurysm sac growth. However, direct sac puncture is our preferred approach given its significantly shorter fluoroscopic and procedural times.

Keywords

Embolization endoleak abdominal aortic aneurysm endovascular aneurysm repair treatment outcome

Introduction

Type II endoleaks (T2EL) are a frequent problem that occur following endovascular aneurysm repairs (EVAR).^1,2 Although most T2EL do not require secondary intervention,^3–6 persistent T2EL leading to aneurysm sac enlargement are more likely to result in adverse outcomes,^7,8 prompting the need for treatment. Despite the incidence of T2EL, a wide range of outcomes have been reported and the optimal technique for embolization is not known.⁹ Options include embolization via the transarterial or direct sac puncture (DSP) routes, endoscopic ligation of feeder vessels, aneurysm sac plication, and surgical explant of the graft. A variety of embolization materials have also been used including particles, coils, thrombin, Onyx®, N-butyl-cyanoacrylate (NBCA) glue, and gelatin sponge. It is widely agreed upon that successful T2EL embolization requires obliteration of the aneurysm sac as though it were the nidus of a vascular malformation.¹⁰

Reported clinical success of T2EL embolization with transarterial or DSP range from 15% to 89%.⁹ Factors affecting the efficacy of endoleak treatment are not fully understood. Furthermore, only a relatively small number of transarterial and DSP embolization outcomes have been examined in existing literature – 120 and 57 total interventions, respectively.⁹ The purpose of this study was to assess the outcomes of T2EL embolization with aneurysm sac obliteration, and to determine whether the embolization approach (transarterial vs. DSP) had an impact on the efficacy of the procedure.

Methods

Study population

Institutional research ethics board approval was obtained. A retrospective review was conducted on all patients who underwent T2EL embolization between January 2003 and December 2012 at our multisite, tertiary academic center. Twenty-seven patients underwent 40 embolization procedures. Four patients were lost to follow up and have been excluded from subsequent analyses. In total, 23 patients (83% male, 17% female) and 35 embolization procedures were examined. The median age was 76 years (95% CI 71–79 years, range: 40–88 years). Initial and repeat embolization was pursued if the patient had a persistent T2EL and the aneurysm grew > 5 mm post-EVAR or post-embolization. Each patient underwent a minimum of two computed tomographic angiography (CTA) studies, one pre-EVAR and one pre-embolization. All embolizations were performed by one of three fellowship-trained vascular and interventional radiologists with 7–10 years of experience.

Techniques

Type 2 endoleak embolization

T2EL embolization was performed by DSP or transarterially. The exact embolization technique was individualized to the patient’s anatomy and endoleak configuration, at the discretion of the radiologist. Embolization materials used include NCBA glue (TRUFILL®, Cordis Corp., Bridgewater, NJ), plantinum microcoils (MicroNester®, Cook Medical, Bloomington, IN), particulate embolic materials (Embosphere®, Merit Medical, South Jordan, UT), Amplatzer™ Vascular Plug (St. Jude Medical, St. Paul, MN), and gelatin sponge slurry. The goal of embolization by any route was always obliteration of the endoleak sac and potentially any large inflow and outflow vessels. Pressure measurements within the aneurysm sac were not routinely obtained before or after embolization. All procedures were performed on an outpatient basis with moderate sedation.

Transarterial embolization

Initial arterial access was obtained through a common femoral artery approach by using the Seldinger technique and a 5- or 6-French vascular sheath was inserted. T2EL originating from the inferior mesenteric artery (IMA) was accessed through the middle colic artery via the arc of Riolan and superior mesenteric artery (SMA). T2EL arising from lumbar arteries were most commonly accessed through the iliolumbar arteries via the internal iliac arteries. In each case, a microcatheter was advanced into the aneurysm sac. Digital subtraction angiography (DSA) was then performed to confirm the type of endoleak, its configuration, and identify any additional inflow or outflow vessels. The embolization agent was then deployed to achieve stasis of blood flow in the aneurysm sac. For glue embolizations, NBCA glue and lipiodol mixture were used (1:3–1:4 glue:lipiodol ratio, at the discretion of the radiologist based on flow dynamics in the aneurysm sac). Post-embolization arteriography was performed to confirm obliteration of the T2EL.

Transabdominal and translumbar DSP embolization

The transabdominal approach was selected if the endoleak sac was located anteriorly or extended anteriorly from the posterior aspect of the aneurysm sac. The translumbar technique was used when anterior access was not suitable. The patient was placed supine (transabdominal) or prone (translumbar). Ultrasound (US) and CT/fluoroscopic guidance were used for transabdominal and translumbar approaches, respectively. Local anesthesia was administered at the puncture site in the abdomen (transabdominal) or back (translumbar). A micro puncture access set (Neff percutaneous access set, Cook Medical or AccuStick™, Boston Scientific, Natick, MA) was placed into the unthrombosed segment of the aneurysm sac. Once flash back of blood was obtained, an arteriogram was performed to confirm correct location within the endoleak. A mandril wire (Cook Medical) or 0.018 hydrophilic wire (Terumo Medical, Tokyo, Japan) was then advanced into the sac. The larger introducer sheath, and subsequently a 4F angiographic catheter were advanced into the sac. An angiogram of the aneurysm sac was performed to confirm the type of endoleak, its configuration, and identify the inflow and outflow vessels. If the IMA was identified with antegrade flow, i.e. away from the sac, suitable coils were placed in the IMA origin or if not possible, in the sac of the aneurysm adjacent to the origin of the artery. This was done to prevent non-target glue embolization of the IMA. The same NBCA glue and lipiodol mixture as above were used to embolize the endoleak sac. The entire sac was filled until there was some glue extruding into the proximal lumbar arteries.

Imaging follow-up

Patients were followed by CTA, DUS, or both modalities post-embolization to monitor the aneurysm sac size and the development of any endoleaks. Patients with normal renal function were imaged by CTA within the first six weeks after the procedure and subsequently every six months. Patients with renal insufficiency were preferentially followed by DUS or non-contrast CT, unless there was an increase in aneurysm size which was large enough to warrant further intervention, in which case a CTA would be performed.

Outcome measures and definitions

The primary outcome is freedom from aneurysm growth. Secondary outcomes included safety, immediate technical success, freedom from persistent T2EL, and repeat embolization rate. Freedom from aneurysm growth was defined as <5% increase in aneurysm sac volume when evaluated by CTA, and <5 mm increase on the largest diameter of the aneurysm in the case of patients who only had DUS follow-up. Freedom from persistent T2EL was defined as lack of enhancement in the aneurysm sac on CTA or lack of flow on DUS after embolization.

Localized endoleaks were defined as having a discrete, definable endoleak lumen, usually visibly communicating with at least one inflow or outflow vessel and having and “aneurysm-in-aneurysm” appearance on CTA (Figure 1). Diffuse endoleaks were defined as lacking a discrete and measurable lumen, most often not visualized on the arterial phase of the scan and showing patchy enhancement of the aneurysm sac on delayed imaging (Figure 2).

Figure 1.

Arterial (a) and delayed (b) phase CTA images of a localized type II endoleak. As shown on the images, the endoleak has a discrete and definable endoleak lumen.

Figure 2.

Arterial (a) and delayed (b) phase CTA images of a diffuse type II endoleak. As shown on the images, the endoleak lacks a discrete and measurable lumen. It is very difficult to visualize in the aneurysm sac on the arterial phase, and demonstrates patchy enhancement (arrow) on the delayed phase.

Statistical analysis and data collection

Data were analyzed in SPSS Statistics (Version 18.0, IBM Corp., Armonk, NY). Continuous variables were compared with Student’s t-test. Categorical variables were compared with Fisher’s exact test. All tests were two-sided and a p value of <0.05 was considered statistically significant. All demographics, imaging data, and reports relevant to the study from pre-EVAR to last follow-up were retrieved for each patient from institutional PACS, Radiology Information System, and Electronic Patient Record. To measure the aneurysm sac size, images from three specific time points were analyzed: immediately prior to EVAR, immediately prior to embolization, and the final available follow-up. The true cross-sectional diameter and the volume of the aneurysm sac were measured using commercial 3D post-processing software (Vitrea fX, Version 4.0, Toshiba Medical Systems). For patients who had follow-up using only DUS, the maximal diameter of the aneurysm sac was recorded. Procedural and immediate post-procedural complications were documented.

Results

The mean duration from EVAR to embolization of the T2EL was 17.7 ± 12.1 months. Following the embolization procedure, patients were followed for a mean duration of 21.8 ± 11.1 months (range: 6–48 months) by CTA and/or DUS. Patients underwent an average of 1.5 ± 0.8 embolization procedures (range: 1 to 4 procedures). Eight patients (35%) required more than one embolization procedure. Glue alone was used in 48% of the technically successful embolizations, followed by glue and coils in 36%, coils alone in 13%, and a combination of microcoils and Embosphere® in 3%.

Among the 23 patients analyzed, 16 had at least one follow-up CTA, and the other 7 were followed with DUS only. Among all 23 patients, 21 (91%) had freedom from aneurysm expansion (Table 1). Persistent T2EL was present at final follow-up imaging in seven (30%) patients. No patients with initial technical success and freedom from aneurysm expansion post-initial embolization later presented with aneurysm expansion.

Table 1.

Outcomes of type II endoleak embolization.

	Freedom from aneurysm sac expansion^a	Sac expansion
All patients	91%	9%
Embolizaion approach ^b
Transarterial	57%	43%	p = 0.74^c
Direct sac puncture	64%	36%

Includes decreased and stable aneurysm sac size with or without persistent type II endoleak.

Analyzed by number of procedures as opposed to the outcome for all patients, which was analyzed per patient each of whom had 1 to 4 embolizations.

Comparison of sac expansion rate between transarterial and DSP embolization approaches.

Outcomes of transarterial and DSP embolizations were compared. They showed similar rates of aneurysm sac expansion (Table 1, p = 0.74) and persistent T2EL post-embolization (p = 0.32). Furthermore, no significant difference was seen between the two approaches with regard to the mean number of embolizations per patient (Table 2, p = 0.10) or number of patients who required multiple embolizations (p = 0.56). On the contrary, DSP embolizations had significantly shorter mean fluoroscopy time (Table 2, p < 0.001) and total procedure time (p < 0.001) than transarterial embolizations.

Table 2.

Procedural information and secondary outcomes.

	All patients	Embolization approach
		Transarterial	Direct sac puncture	p ^a
Mean fluoroscopy time (min)	28.7	42.4	11.2	<0.001
Mean procedure time (min)	150	181	103	<0.001
Mean no. of embolizations per patient^b	1.48	1.65	1.17	0.10
Repeat embolization rate^b	35%	41%	17%	0.56
Technical success rate	89%	81%	100%	0.28
Complication rate^c	12%	15%	6%	0.64

Comparison between transarterial and DSP approaches.

With respect to each individual embolization approach, these analyses are based on the embolization approach taken on the patient’s initial procedure.

Includes major and minor complications.

Whether the addition of coils is more efficacious than using glue alone in preventing aneurysm growth was examined. Both groups had similar rates of aneurysm sac expansion (p = 0.63) and persistent T2EL (p = 0.65). Moreover, we investigated whether configuration of the T2EL impacted the success of the embolization procedure. Patients with the two different T2EL configurations showed similar rates of aneurysm sac expansion (p = 1.0) and persistent T2EL post-embolization (p = 1.0).

In 11% of cases, inadequate access to the aneurysm sac or immediate feeding vessel was obtained, thus no embolization agents were used. All four cases with inadequate access were attempted through the transarterial approach. These patients underwent additional embolization procedure(s), via DSP, which were technically successful. All DSP embolizations were technically successful. The overall per-procedure technical success rate for embolization of T2EL was 89%. Transarterial and DSP approaches did not have significantly different technical success rates (Table 2, p = 0.28).

There was one major procedure-related complication, where an arterial injury of a lumbar artery occurred during the embolization. Transarterial embolization was performed to stop the bleed. The patient was asymptomatic and was admitted overnight for observation (<24 h). Furthermore, there were four minor complications. Two patients had small non-target glue embolizations with no consequence. One patient developed a puncture site hematoma and required an additional 15 min of puncture site compression at the end of the procedure with no sequela. One patient had a microperforation of a lumbar artery that was immediately embolized with a tiny amount of polyvinyl alcohol particles. No significant difference was found between overall complication rates of transarterial and DSP approaches (Table 2, p = 0.64).

Discussion

Endoleaks are the primary reason that long-term surveillance post-EVAR is needed, because of their potential impact on the durability of the repair.¹¹ T2EL occur in approximately 10% to 30% of patients who undergo EVAR, 35% of these resolve spontaneously,⁹ and 40% to 60% require further intervention.^12,13 It is generally accepted that T2EL that persist longer than six months and those that result in growth of the aneurysm sac require treatment. Transarterial and DSP embolization are the two most common approaches^14,15 because of their minimally invasive nature and resulting low morbidity and mortality. Alternatives for treatment include ligation of lumbar or mesenteric arteries,¹⁶ aneurysm sac plication,¹⁷ or as a last resort, surgical explant.¹³ The ideal technique for management of T2EL remains unknown and outcomes of treatment vary widely. Given the prevalence of T2EL post-EVAR and the cost of repeat interventions to treat them, an optimal management strategy is essential.

In this study, we examined 23 patients with T2EL and associated aneurysm enlargement who underwent embolization via either the transarterial or DSP approach with the goal of obliterating the aneurysm sac. Our results indicate that at one to three years post-treatment, embolization of the aneurysm sac via transarterial or DSP approach using glue with or without coils is similarly effective at preventing further aneurysm growth as a result of T2EL, with 91% of all patients having freedom from aneurysm sac expansion. Likewise, the two embolization approaches had similar technical success, persistent T2EL, and complication rates.

Although the primary outcome of the two embolization approaches is similar, compared to DSP embolizations, transarterial embolizations required a nearly four-fold increase in the duration of fluoroscopy time needed during the procedure (11 vs. 42 min, respectively, p < 0.001), and almost double the total procedure time (103 vs. 181 min, respectively, p < 0.001). Consequently, DSP embolizations result in considerably less ionizing radiation, particularly if the procedure is US-guided. Furthermore, shorter procedure time also has many innate advantages, such as decreased risk of infection and sedation, as well as potentially cost-saving.

Among the existing studies investigating the outcomes of T2EL treatment with longer follow-up periods, freedom from aneurysm sac expansion was noted in 44%¹⁸ and 76%¹⁹ of patients. Our center was able to achieve a better outcome. Part of this may be due to the longer follow-up period in these studies (5 and 3.5 years, respectively). However, at two years post-embolization, freedom from sac expansion in the series by Sarac et al.¹⁸ was approximately 70%, which remains lower than the 91% rate in the current study.

We hypothesize that the high success rate in this study relates to the extensive use of glue to obliterate the aneurysm sac. For example, in the present study, there was a lower proportion of embolizations performed using coils only (13% vs. 29%) compared to the study by Sarac et al. This is supported by the generally poor short-term outcomes reported in literature for coil embolizations.^20–22 Although we tried to place coils in the inflow and/or outflow vessel origin whenever possible in DSP embolizations, for technical reasons, the position of the puncture makes this impossible at times. In these cases where we are unable to advance the tip of the catheter far enough to the inflow/outflow vessel origin, only glue would be used to obliterate the aneurysm sac. Importantly, the current report did not show a difference in outcome related to the approach to embolization (DSP vs. transarterial), suggesting that any method that effectively obliterates the aneurysm sac and inflow/outflow vessels could be equally effective. A sizable proportion (35%) of the study patients did require more than one embolization. This is comparable to published studies with reintervention rates ranging from 24% to 45% and highlights the difficulties in the treatment of this complex problem.^18,19,23 Despite the low rate (9%) of aneurysm growth, a higher percentage of patients (30%) did have persistent T2EL on imaging follow-up.

Two other studies reported persistent T2EL at last follow-up in 75% and 72% of patients.^19,23 The rate in the current report was lower at 30%. Again, the focus on obliterating the aneurysm sac likely contributed to this improved outcome. However, it may also be partially attributable to the fact that some of our patients only had DUS follow-up post-embolization, which is not as sensitive in detecting T2EL as CTA.²⁴ However, DUS has been shown to be equivalent to CTA in monitoring aneurysm sac diameter post-EVAR,²⁵ although the actual diameters would likely differ slightly when measured with the two different modalities.²⁶ Moreover, it is generally accepted that stabilization or decreased size of the aneurysm with absence of aneurysm rupture is the most important outcome and the importance of persistent enhancement alone in the aneurysm sac is uncertain, but likely of no consequence.^3–5

Although no statistically significant difference was noted in the eventual embolization outcome between localized and diffuse T2EL (68% vs. 67% freedom from aneurysm growth, respectively), only three patients in the current study population had diffuse T2EL. Rather than a lack of true difference, the small sample size of diffuse T2EL patients may have limited the ability to demonstrate a difference in outcome. It is premature to conclude that embolization of localized and diffuse T2EL have similar outcomes.

This study is limited by its small sample size. The retrospective nature of the study design means that there is innate selection bias with no control over the timing or type of T2EL embolization treatment performed. In addition, follow-up imaging modality and duration were not standardized, which reduced the number of post-embolization aneurysm volume measurements that could be made since some patients only had DUS follow-up. In our practice, patients with normal renal function are imaged with CTA by patients with chronic renal insufficiency are often monitored by DUS only, with CTA reserved for the evaluation of aneurysm sac growth or other concerning findings. Furthermore, in part due to the tertiary nature of our referral base, patients are often followed-up by centers in their community on a long-term basis, resulting in smaller numbers of patients with follow-up imaging and lack of longer term follow-up data for many of them.

In summary, the current study suggests that both transarterial and DSP embolizations of T2EL with sac obliteration are similarly effective at preventing further aneurysm sac growth. Earlier in the cohort, we preferred the transarterial approach. Over time, based on our own experience and emerging literature, which highlighted the importance of aneurysm sac obliteration in type 2 endoleak embolization, as well as the significantly shorter procedure and fluoroscopy time offered by DSP, it has become our preferred approach for treating T2EL, and we would now only use the transarterial approach if there is no suitable approach to DSP.

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.

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