Technical and clinical success analysis of transarterial embolization therapy in type II endoleaks following endovascular aortic repair

Abstract

Purpose

This single-center study investigated the safety and efficacy of transarterial embolization of type II endoleaks for expanding aneurysm sacs following endovascular aortic repair (EVAR).

Materials and Methods

36 patients (33 men, 75.9±6.6 years) underwent a total of 50 endovascular procedures for type II endoleak embolization between 2008 and 2023. Analyses included the assessment of patient risk profiles, aneurysm morphology, and endoleak characteristics. Outcome parameters comprised the technical success (i.e., complete lack of blood flow in the previously perfused aneurysm sac) and complication rates, while clinical success was defined as the absence of endoleak persistence or recurrence and freedom from aneurysm enlargement > 0.5 cm over the follow-up period.

Results

Transarterial embolization was technically successful in 84% of procedures with a complication rate of 2%. Most interventions were coil-based (72%), while a small number relied solely on liquid embolic agents (14%). Absence of a persisting endoleak in the earliest follow-up could be demonstrated in 75.6% of cases, whereas the absence rate for endoleak recurrence was substantially lower (46.3%). No aneurysm enlargement > 0.5 cm during follow-up was ascertained after 73.2% of interventions.

Conclusion

Transarterial embolization represents a safe treatment for type II endoleaks after EVAR. While embolization was moderately effective in preventing further expansion of aneurysms due to endoleak recurrence, most procedures were successful in permanently eliminating the targeted feeder vessels.

Key Points

• Transarterial embolization of type II endoleaks has a high technical success rate.

• The emergence of new feeder vessels may necessitate multiple procedures over time.

• Patient risk profiles did not factor into the clinical outcome.

Citation Format

• Krompaß K, Grunz JP, Augustin AM et al. Technical and clinical success analysis of transarterial embolization therapy in type II endoleaks following endovascular aortic repair. Fortschr Röntgenstr 2024; DOI 10.1055/a-2384-4601

Zusammenfassung

Ziel

In dieser monozentrischen Studie wurden Sicherheit und Wirksamkeit der transarteriellen Embolisation von Typ-II-Endoleaks untersucht.

Material und Methoden

Bei 36 Patienten (33 Männer, 75,9 ± 6,6 Jahre) wurden zwischen 2008 und 2023 insgesamt 50 endovaskuläre Embolisationen eines Typ-II-Endoleaks durchgeführt. Diese Studie umfasste die Analyse der Aneurysma-Morphologie und der Endoleak-Charakteristika. Neben dem technischen Erfolg (d.h. fehlende Kontrastierung des vormals perfundierten Aneurysmasacks) und der Komplikationsrate wurde der klinische Erfolg untersucht, definiert als das Fehlen einer persistierenden oder neuen Leckage und das Ausbleiben einer Größenzunahme des Aneurysmas um >0,5 cm.

Ergebnisse

Die transarterielle Embolisierung war in 84% der Eingriffe erfolgreich, während die Komplikationsrate bei 2% lag. Die meisten Interventionen erfolgten Coil-basiert (72%), während ein kleiner Teil der Prozeduren ausschließlich mit Flüssigembolisaten durchgeführt wurde (14%). In 75,6% konnte kein persistierendes Endoleak festgestellt werden, während Rezidivfreiheit über das gesamte Follow-up deutlich seltener erreicht wurde (46,3%). Ausbleibendes Aneurysmawachstum >0,5 cm wurde in 73.2% der Fälle dokumentiert.

Schlussfolgerung

Die transarterielle Embolisation stellt eine sichere Behandlung für Typ-II-Endoleaks nach EVAR dar. Obwohl die Therapie bei der Verhinderung einer weiteren Aneurysma-Ausdehnung aufgrund rezidivierender Endoleaks nur mäßigen Erfolg zeigte, waren die meisten Interventionen erfolgreich bei der dauerhaften Ausschaltung der anvisierten Feeder-Gefäße.

Kernaussagen

• Die transarterielle Embolisation von Typ-II-Endoleaks hat eine hohe technische Erfolgsrate.

• Das Entstehen neuer Feeder-Gefäße kann im Verlauf mehrere Eingriffe erforderlich machen.

• Das patientenspezifische Risikoprofil hat keinen Einfluss auf das klinische Ergebnis.

Keywords

Type II endoleak - Digital subtraction angiography - Transarterial embolization - Procedural success - Outcome analysis

Introduction

With an incidence of 10–25%, type II endoleaks are more common than any other type of endoleak and represent the most frequent complication after endovascular aortic repair (EVAR) [1]. Type II endoleaks facilitate retrograde perfusion of an aneurysm sac through lateral feeder vessels, most often from lumbar segmental arteries or the inferior mesenteric artery but also from intercostal arteries in the case of thoracic EVAR [2]. In order to detect endoleaks promptly, patients are advised to undergo lifelong, periodic imaging after EVAR [3]. CT angiography and contrast-enhanced ultrasound are the examination methods of choice, whereas diagnostic digital subtraction angiography (DSA) has become less important for follow-up imaging due to its invasiveness [4]. MRI may also play a role in long-term follow-up [5].

If a type II endoleak is documented and the aneurysm’s size increases substantially, endovascular feeder embolization represents a potential method to cut off the blood flow into the aneurysm sac. While other routes exist, the most common techniques are retrograde catheterization via the common femoral artery and percutaneous translumbar or transabdominal access [6]. Regardless of the access route, coils or liquid embolic agents or a combination of both can be used to disrupt the perfusion of feeder vessels [7]. While the former come in the form of microcoils and macrocoils, the group of liquid embolic agents includes cyanoacrylate derivates or ethylene vinyl alcohol copolymer-based adhesives [8]. Due to their material properties, liquid embolic agents fill a target volume more completely than coils, which may support embolization of the endoleak nidus, i.e., the intraaortic cavity or connecting zone of the afferent and efferent supply arteries [9]. However, a disadvantage is the higher risk of vascular injury if the catheter becomes stuck in the target area. In addition, non-target embolization occurs more frequently with liquid embolization than with the use of coils [10].

Due to the heterogeneous nature of the data and the fact that embolization of type II endoleaks is a relatively rare and highly specialized procedure, the 2024 clinical practice guidelines of the European Society for Vascular Surgery (ESVS) do not contain a clear recommendation regarding the optimal access route and embolization material for interventional closure of type II endoleaks [4]. Therefore, this study was designed to address the need for more data as well as to investigate the safety and efficacy of transarterial embolization of type II endoleaks via the common femoral artery following EVAR.

Materials and Methods

Study design

In this monocentric study, the data of patients who underwent endovascular treatment of a type II endoleak between January 2008 and September 2023 at a tertiary-care university hospital were retrieved from the institution’s electronic database and analyzed retrospectively. By definition, previous EVAR of an abdominal or thoracic aortic aneurysm was necessary for study inclusion. Patients with recurrent endoleaks and repeated endovascular treatment after EVAR were also included. The study design received the approval of the local ethics committee (2023072601), who waived the need to obtain separate written informed consent due to the retrospective nature of the investigation.

Patient analysis

Sociodemographic parameters and clinical risk profiles were registered for each patient. The analyzed sample comprised 36 individuals (75.9 ± 6.6 years), including 33 men (91.7%). Nine patients (22.2%) received at least two endovascular interventions, bringing the total number of procedures to 50. All but three patients were regularly taking anticoagulant medication (91.7%). [Table 1] provides an overview of the risk profile of the study sample including common underlying diseases. Notably, 341 abdominal and 130 thoracic EVAR procedures were performed in our hospital during the study enrollment period.

Table 1 Patient sample.

Patient age	75.9 ± 6.6 years (mean ± standard deviation)
Patient sex	33 men (91.7%) and 3 women (8.3%)
Risk factor	Frequency	Risk factor	Frequency
Note: Relative frequencies were calculated for the entire patient sample (i.e., 36 individuals). COPD: chronic obstructive pulmonary disease; TIA: transitory ischemic attack.
Arterial hypertension	29 (80.6%)	Atrial fibrillation	7 (19.4%)
Smoking (current or past)	17 (47.2%)	Arteriosclerosis	6 (16.7%)
Dyslipidemia	14 (38.9%)	Heart failure	4 (11.1%)
Coronary heart disease	12 (33.3%)	COPD	4 (11.1%)
Obesity	10 (27.8%)	Post-stroke	3 (8.3%)
Diabetes mellitus	9 (25.0%)	Post-TIA	1 (2.8%)

Aneurysm analysis

Both the aneurysm morphology and the position of the inserted stent graft were assessed. The maximum diameter of the aneurysm (centerline measurements in CT angiography or determined via contrast-enhanced ultrasound) was recorded for each patient at different time points: The first size measurement was performed before EVAR, and further control points were defined before the primary and each subsequent endovascular procedure. Based on these measurements, the time intervals between EVAR and type II endoleak detection, between EVAR and the angiographic intervention, and between the first endoleak detection and angiography were evaluated.

Endoleak analysis

Due to the study-specific inclusion criteria, all recorded and treated endoleaks were type II leaks according to the classification of White and Stavropoulos [7]. The number of feeder vessels perfusing the aneurysm sac was recorded before each intervention. If a single feeder vessel could be identified, the endoleak was determined as type IIa (i.e., simple), whereas endoleaks with two or more feeders were classified as type IIb (i.e., complex). For each feeder, the originating vessel was determined.

Procedure analysis

Transarterial endoleak embolization was performed in dedicated angiography suites. Either the Axiom Artis Zee (Siemens Healthineers, Forchheim, Germany) or Azurion Clarity IQ (Philips Medical Systems, Best, The Netherlands) angiography system was used to perform DSA during the study period. All procedures were performed by a board-certified interventional radiologist with 27 years of clinical experience. During interventions, both intermittent fluoroscopy and DSA (with both selective/super-selective manual injections as well as non-selective, high-pressure injections) were employed to identify and catheterize feeder vessels before embolization. Once the desired catheter position was verified by imaging, either coils or liquid embolic agents, or a combination thereof was utilized to occlude the feeder vessel. (Push) coil embolization was the preferred method if super-selective catheterization of an endoleak’s nidus was achieved, whereas liquid embolization was performed in cases with distal rarefication of feeding vessels preventing microcatheter placement within the nidus. A combination of coils and liquids was used in certain cases to avoid non-target embolization. Frequently used coil types included the manufacturer-specific pushable models Nester (Cook Medical, Bjaeverskov, Denmark), VortX (Boston Scientific, Marlborough, MA, USA), and Tornado (Cook Medical), or the detachable Concerto microcoils (Medtronic, Dublin, Ireland) in various lengths and sizes; the number of coils was documented for coil-based interventions. The two most commonly used liquid embolic agents were n-butyl-2-cyanoacrylate (Histoacryl; B.Braun, Melsungen, Germany) and synthetic surgical glue (Glubran 2; GEM, Viareggio, Italy).

Outcome analysis

The success of interventions was measured according to two criteria. Technically successful embolization required the complete lack of blood flow in the previously perfused aneurysm sac, i.e., no accumulation of contrast medium in the final DSA series. In addition, all procedural complications were recorded and the complication rate in the patient population was calculated. A complication was defined as any unforeseen event with potentially negative consequences for a patient's state of health that originated from the intervention and would not have occurred otherwise. Complications were classified according to the reporting standards of the Society of Interventional Radiology as major or minor [11].

In order to evaluate the long-term clinical success, the image-based control examinations following the respective angiography examination were analyzed. The parameters assessed in follow-up imaging included the perfusion of the aneurysm sac via a persistent or new endoleak, the maximum extent of the aneurysm sac, and the change in the sac’s maximum diameter compared to pre-angiographic imaging. In accordance with Iwakoshi et al. and a meta-analysis by Akmal et al., embolization was considered successful if the maximum diameter of the aneurysm sac either decreased, remained constant, or increased ≤ 0.5 cm over all follow-up examinations [12] [13]. Leaks that continued to cause perfusion of the aneurysm sac in the first follow-up examination after endovascular therapy were defined as persistent endoleaks. In contrast, a feeder which could not be delineated on the DSA scan used to guide the embolization procedure was considered a new endoleak. Based on this consideration, the freedom rates for recurrence and persistent endoleaks were calculated. In addition, the re-intervention rate was determined as the ratio of patients who underwent multiple transarterial embolization treatments for type II endoleaks to the total size of the patient sample.

Statistical analysis

Data analyses were performed using specific software (SPSS Statistics version 28.0; IBM, Armonk, New York, USA). In a first step, metric variables were tested for the presence of normal distribution using Kolmogorov-Smirnov tests. For metric items without normal distribution and ordinal or nominal items, the absolute and relative frequencies are given with median values and interquartile ranges. For normally distributed metric variables, mean values and standard deviations are provided instead. In order to examine the connection between two items with a metric scale level, correlation analyses were carried out using the Pearson coefficient (r). If one variable was nominally scaled, the Eta coefficient was determined instead. In the case of two nominally or dichotomously scaled items, the Phi coefficient was used. Null hypotheses were rejected if the corresponding alpha error was below a value of 0.05.

Results

Aneurysm morphology

Based on preoperative imaging, 17 aneurysms were classified as fusiform, 14 as sacciform, and 5 as a fusisacciform mixed type. Preexisting occlusion of the inferior mesenteric artery was ascertained in 19.4% of patients. Meanwhile the median number of perfused lumbar arteries was 4 (interquartile range 2–6). Most patients displayed minor intra-aneurysmal thrombosis (91.7%). During EVAR, the vast majority of patients had received an aorto-bi-iliac prosthesis (80.6%). Before stent graft insertion, the average maximum aneurysm diameter was 5.8 cm (5.3–6.3 cm). Before endoleak embolization, the median aneurysm diameter was 6.7 cm (6.1–7.9 cm), which corresponds to an average size increase of 0.8 cm (0.6–1.2 cm) between insertion of the stent graft and the interventional endoleak therapy. The average time between implantation of the endograft and first detection of a type II endoleak was 8 days (0–196 days). In eleven patients (30.6%), the first documentation of a type II endoleak already occurred intraoperatively during EVAR. The average time between EVAR and the first transarterial embolization was 820 days (364–1436 days), while the interval between endoleak detection and first endovascular therapy was 511 days (87–1246 days).

Endoleak characterization

Of the 50 type II endoleaks treated, a single feeder vessel (type IIa) was identified in 32 cases. More than one feeder vessel (type IIb) was detected in the remaining 18 cases. The majority of endoleaks analyzed in this study originated in one of the iliac vessels. Less common were endoleaks stemming from the mesenteric arteries and the lumbar or gluteal arteries. In the two patients with thoracic stent grafts, type II endoleaks originated from the intercostal arteries. [Table 2] summarizes the morphological characteristics of aneurysms, stent grafts, and endoleaks in the study sample, while Supplemental Table S1 provides a detailed overview of the endoleak origins in all 50 procedures.

Table 2 Aneurysm and endoleak characterization.

Parameters	Frequency
Note: Relative frequencies were calculated either for the entire patient sample (i.e., 36 individuals) or the entirety of interventions (i.e., 50 procedures).
Aneurysm morphology	Reference: 36 patients
Fusiform	17 (47.2%)
Sacciform	14 (38.9%)
Fusisacciform	5 (13.9%)
Type of endograft	Reference: 36 patients
Aorto-bi-iliac graft	29 (80.6%)
Aorto-mono-iliac graft	4 (11.1%)
Thoracic tube graft	2 (5.6%)
Abdominal tube graft	1 (2.8%)
Number of feeder vessels	Reference: 50 interventions
One feeder (type IIa)	32 (64.0%)
Two feeders (type IIb)	11 (22.0%)
Three feeders (type IIb)	6 (12.0%)
Four feeders (type IIb)	1 (2.0%)

Technical success

The exclusive use of coils was recorded for 29 embolizations (58.0%), with the number of coils varying from a minimum of one to a maximum of 39 coils during one procedure ([Table 3]). A successful coil embolization is shown in [Fig. 1]. In seven interventions (14.0%), a liquid embolic agent was used in addition to coil embolization. In seven other procedures (14.0%), endoleaks were treated exclusively with liquid embolic agents ([Fig. 2]).

Table 3 Number of coils used per embolization procedure.

Number of coils	Frequency
Note: Relative frequencies were calculated for coil-based interventions (i.e., 36 of 50).
< 5	9 (25.0%)
5–10	10 (27.8%)
10–20	11 (30.6%)
> 20	6 (16.7%)

Fig. 1 Successful transarterial embolization for the treatment of a type II endoleak originating from the inferior mesenteric artery after EVAR (A). Two 5 mm coils were used in this 83-year-old patient (B). Aneurysm perfusion was permanently absent after the interventional procedure (C).

Fig. 2 In a 64-year-old man, a lumbar artery branch was seen feeding a type II endoleak after EVAR had been performed for an abdominal aortic aneurysm with insertion of a bi-iliac stentgraft. Due to a continuously enlarging right iliac artery aneurysm associated with the endoleak, endovascular therapy was requested (A). Technically successful super-selective embolization was performed using a combination of cyanoacrylate glue and lipiodol because of the feeder vessel’s corkscrew-like morphology (B). No recurring endoleak was observed during follow-up.

Successful embolization of target vessels with complete elimination of aneurysm perfusion was achieved in 42 procedures. Therefore, the technical success rate was 84%. Reasons for unsuccessful embolization were pronounced kinking of the iliac arteries (n = 2), a corkscrew-like tortuous course of the lumbar arteries (n = 1), or the presence of a particularly narrow caliber vascular plexus (n = 5). Follow-up imaging via CTA was available after six unsuccessful embolization attempts. In all of these cases, the initially targeted type II endoleak was classified as persistent with four aneurysm sacs showing further enlargement. However, only one patient was referred to open surgery (i.e., ligation). The other patients received periodic follow-up scans. Nine patients required more than one endovascular embolization procedure during the observation period, resulting in a re-intervention rate of 25%. Five patients (13.9%) underwent a single re-intervention, three patients (8.3%) required two further interventions, and one patient (2.8%) underwent three re-interventions for recurrent type II endoleaks ([Fig. 3]).

Fig. 3 Multiple transarterial embolization procedures for recurrent type II endoleaks in an 83-year-old man finally resulting in permanent cessation of aneurysm growth. A/B Before and after coiling of a feeder from the main trunk of the left internal iliac artery. C/D Before and after coiling of a total of three feeder vessels from the right internal iliac artery. E/F Before and after coiling of a feeder from the left superior gluteal artery. G/H Before and after coiling of a feeder vessel from the inferior mesenteric artery.

Clinical success

Since no follow-up was available for nine of the 50 endovascular interventions, the following key figures could only be calculated for the 41 interventions with subsequent CT angiography and/or ultrasound controls. The median follow-up interval was 221 days (101–615 days). The average time interval between endoleak embolization and the first follow-up examination was 88 days (31–117 days) ([Fig. 4]). No persistent endoleak was detectable in 31 of the earliest follow-up examinations. Therefore, the clinical success rate in this respect was 75.6%. Over the entire control period, no endoleak recurrence was recorded after 19 procedures, hence the recurrence-free rate was 46.3%. Size progression of the aneurysm sac during follow-up was detected after 21 interventions (51.2%). However, a progression of > 0.5 cm was only ascertained in eleven instances (26.8%) ([Table 4]). No significant correlation could be determined between any of the recorded risk factors and the technical or clinical success parameters (all p > 0.05). In contrast, the maximum aneurysm sac size before endovascular therapy correlated strongly with the largest diameter during follow-up (r = 0.87; 95% confidence interval 0.76–0.93).

Fig. 4 Median time intervals with interquartile ranges in parentheses.

Table 4 Maximum aneurysm diameter during follow-up.

Note: Relative frequencies were calculated for the number of interventions with available imaging follow-up with either contrast-enhanced ultrasound or CT angiography (i.e., 41 of 50).
	Size difference	Frequency
Regression	All	12 (29.3%)
	–0.1 to -0.5 cm	8 (19.5%)
	–0.6 to -1.0 cm	4 (9.8%)
Consistency	All	8 (19.5%)
Progression	All	21 (51.2%)
	+0.2 to +0.5 cm	10 (24.4%)
	+0.6 to +2.0 cm	8 (19.5%)
	more than +2.0 cm	3 (7.3%)

Rate of complications

No major complications were recorded in the investigated patient sample. After one endovascular embolization, a self-limiting pseudoaneurysm of the right common femoral artery was registered, accounting for a minor complication. Accordingly, the overall procedural complication rate was 2%.

Discussion

In this large single-center study, a high technical success rate (84%) and low complication rate (2%) were established for transfemoral embolization of type II endoleaks after previous endovascular aortic repair. Clinical success, defined by the absence of a persistent endoleak in the earliest imaging follow-up, was ascertained in 75.6% of cases, demonstrating the general efficacy of endovascular therapy. While the endoleak recurrence rate was comparatively high at 53.7%, transarterial embolization was able to prevent a relevant growth of the aneurysm sac in 73.2% of the interventions. As a major finding, individual risk profiles were not substantially related to the angiographic or clinical success.

Regarding the effect of patient risk profiles, a study by Vandelbulcke et al. postulated that active smoking and hyperlipidemia would have a positive influence on the “radiological success”, which they defined as follows: No persistent endoleak and no increase in maximal axial diameter in the first postinterventional control [14]. Interestingly, the results of Sarac et al., who found that smokers have a higher risk of postinterventional expansion of the aneurysm sac, are in exact contrast to this. In this study, hyperlipidemia was the only variable associated with a higher risk of a second interventional procedure [15]. The contrasting findings of Vandelbulcke et al. and Sarac et al. underline that a scientific consensus on the effects of the individual risk profile does not exist so far. Therefore, the absence of a substantial correlation between risk profile and outcome within our data appears plausible. Another central aim of many studies is to determine which endoleak- or aneurysm-related characteristics influence the success of treatment. In our study, we observed that the maximum pre-interventional diameter is a predictive variable for the maximum post-interventional diameter of the aneurysm sac. This is consistent with the results of Iwakoshi et al., who postulated that the maximum diameter before endovascular treatment represents a risk factor for further aneurysm growth after the intervention [12].

The technical success rates in the present investigation are comparable with the results of other studies. While Vance et al. recorded an overall success rate of 98%, the authors compared the success of different access routes [16]. While direct translumbar or transabdominal access led to success in 100% of cases, perigraft access was successful in 86%. It should be noted that the transarterial route, which was used exclusively in the present patient sample, resulted in a success rate of merely 76% for Vance et al. [16]. A meta-analysis by Ultee et al. found different success rates depending on the chosen access route: 98.7% for translumbar access, 93.3% for transcaval procedures, and 98.1% for open ligation. Interestingly, the technical success rate for transarterial access was again significantly lower at 84% [8]. Since transarterial embolization is obviously a demanding procedure, our high success rates may be attributed to the profound expertise of the specialized interventional radiologist who performed all 50 procedures in the present study.

Another important indicator for evaluating an interventional procedure is the number of complications. In this study, the complication rate was 2%, as only one self-limiting inguinal pseudoaneurysm occurred, classified as a minor complication. In contrast, Ultee et al. described minor and major complications in 3.8% of 1073 interventions in their meta-analysis. These included, among others, ischemic colitis, coil misplacement, and cardiac decompensation [8]. It can be assumed that the low complication rate in the present study is partly due to the high number of transarterial embolization procedures in a single center. For comparison, Iwakoshi et al. were able to include a total of 315 patients from 19 Japanese centers, which corresponds to approximately 17 patients per center [12]. More than twice as many patients were included in the current study, supporting the hypothesis that highly specialized procedures, such as transarterial embolization of type II endoleaks, should be conducted in high-performance centers whenever possible.

The re-intervention rate in the current study was 25%, which is in line with the results of Iwakoshi et al. (24.7%) and Sarac et al. (24%) [12] [15]. In the study sample of Arenas Azofra et al., the frequency of additional procedures was even higher at 35.7% [17]. It should be noted that the overall re-intervention rate described by Ultee et al. was by far the lowest with just 14.7% [8]. However, this may be attributed to the meta-analysis also including several studies in which an open surgical procedure was used, since some of these studies recorded a re-intervention rate of 0% [18] [19] [20]. In the earliest follow-up, no persistent endoleak was determined after 75.6% of interventions in our study, while the goal of postinterventional endoleak elimination was only achieved in 41.7% of cases by Vandenbulcke et al. [14]. A potential explanation lies in the fact that endoleaks were primarily closed with coils in the current study (83.7%). In contrast, Vandenbulcke et al. used liquid embolization exclusively in 48.3% of interventions, additional coils in 43.3% and coils exclusively in only 5% of procedures [14]. Whereas 73.2% of our patients did not experience aneurysm growth > 0.5 cm during follow-up, other groups reported weaker results in this respect. In the investigations of Iwakoshi et al., Sarac et al., and Arenas Azofra et al., only 55.4%, 44%, and 62.5% of interventions were deemed clinically successful under the same criteria (no diameter increase > 0.5 cm) [12] [15] [17]. In the light of these findings, the use of coils may be considered most effective if the nidus of an endoleak can be probed directly. In this scenario, higher procedure safety constitutes a particular advantage of coil usage due to a lower rate of non-target embolization. In other situations, however, we believe that liquid embolic agents should be selected. Notably, the 2024 ESVS guidelines do not recommend endovascular embolization for aneurysm sac growth of less than 1 cm [4], hence the clinical impact of enlargement between 0.5 and 1 cm may be lower than expected in the past.

Several methodological limitations must be taken into account when interpreting the results of the present investigation. First, it should be emphasized that this study is based on a monocentric data analysis with a retrospective design over a period of 15 years. Compared to multicenter studies, there was no external validation of results. Second, the follow-up varied individually without a standardized scheme, which makes a structured comparison of patient aftercare difficult. Furthermore, a median follow-up interval of 221 days is rather short when considering the frequently slow progress of type II endoleaks. Third, no CT-guided embolization was performed in this patient series. The main reason for this lies in our hospital’s policy of subjecting patients to a surgical approach, if type II endoleaks have a blurred or unsharp character on pre-interventional CTA. Therefore, this alternative option for type II endoleak treatment was not explored in the present study. Fourth, the techniques and materials used for transarterial access of the endoleak nidus and the embolic agents employed for its occlusion were at the discretion of the interventional radiologist who performed all 50 procedures. Fifth, since neither CT angiography nor contrast-enhanced ultrasound are performed directly after an embolization procedure, the DSA from the embolization itself was used as the baseline to differentiate persistent from newly arising endoleaks. Sixth, no prophylactic mesenteric or lumbar artery embolization took place prior to EVAR in the investigated patient sample. Therefore, the effect of this procedure could not be analyzed. Finally, there is a lack of scientific consensus as to whether coils or liquid embolic agents provide better long-term results for the treatment of type II endoleaks. The best way to evaluate this would be in a prospective, randomized controlled study design. However, as the treatment of type II endoleaks is a rare intervention for most interventional radiologists, a multicenter study with standardized conditions would be desirable.

Conclusion

Despite being a challenging interventional procedure, transarterial embolization of type II endoleaks after EVAR constitutes a safe form of treatment with a low complication rate. While endoleak recurrences limit the effectiveness in the long-term prevention of aneurysm enlargement, most interventions succeeded in permanently eliminating the targeted feeder vessels.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Publication History

Received: 16 May 2024

Accepted after revision: 09 August 2024

Article published online:
01 October 2024