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^ CLINICAL
INVESTIGATION ——————————————————————————
^
Treatment of Type I Endoleaks Using Transcatheter Embolization With Onyx Karla Maria Eberhardt, MD1; Mojtaba Sadeghi-Azandaryani, MD2; Stefanie Worlicek, MD1; Thomas Koeppel, MD3; Maximilian F. Reiser, MD, FRCR1; and Marcus Treitl, MD, EBIR1 Institute for Clinical Radiology and 3Department of Vascular Surgery, Hospitals of the Ludwig Maximilian University of Munich, Germany. 2Division of Vascular Surgery, Department of Surgery, District Hospital of Erding, Germany.
1
^
^
Purpose: To report a single-center experience with transcatheter embolization of type I endoleaks using the liquid embolic agent Onyx, an ethylene vinyl alcohol copolymer. Methods: Eight patients (4 men; mean age 74.8 years, range 63–86) with 10 type I endoleaks (6 abdominal and 4 thoracic) diagnosed 2 days to 9 years after endovascular repair were treated with Onyx embolization because cuff extension was precluded by an insufficient landing zone in 6 cases and an unsuitable aortic diameter in 2. Endoleaks were accessed with a 4-F diagnostic catheter and a coaxially introduced dimethylsulfoxide-compatible microcatheter. Onyx-34 was predominantly applied due to its high viscosity; patent side branches were coil embolized prior to Onyx delivery in 3 cases. Results: Technical success of the procedure was achieved in all cases. The mean volume of Onyx used for abdominal endoleaks was 11.8 mL (range 3.0–25.5) and 19.4 mL (range 4.5– 31.5) for thoracic endoleaks. The average duration of the procedure was 76.7 minutes (range 34.5–110.6), and the average radiation dose area product was 18.8 cGy*cm2 (range 10.6–55.8). Reperfusion of the endoleak was detected in one case 2 days after the procedure. A second case showed an occluded endoleak but a small trace of contrast between the aortic wall and the stent-graft. Non-target embolization was not found in any case. Mean follow-up was 13.2 months (range 8–24). The mean reduction in diameters for thoracic aneurysms after 6 and 12 months was 0.4 and 0.9 cm, respectively, and 0.6 and 1.2 cm, respectively, for abdominal aneurysms. Conclusion: Transcatheter embolization of type I endoleaks using Onyx is a simple, safe, and sustainable treatment option with a high primary success rate for cases in which stentgraft extension is not possible. The benefit of additional coil embolization remains uncertain. J Endovasc Ther. 2014;21:162–171 Key words: aortic aneurysm, endovascular aneurysm repair, type I endoleak, embolization, ethylene vinyl alcohol copolymer, Onyx, tantalum, coil embolization ^ ^
Because type I endoleaks are associated with an increased risk of rupture and aneurysmrelated death in patients who have undergone endovascular repair of abdominal or thoracic aneurysm [(T)EVAR], treatment is mandatory.
Ethylene vinyl alcohol copolymer Onyx is a newer alternative1 to the well known arsenal of materials for transcatheter embolization of type I endoleaks, such as coils, glues, and thrombin. This liquid embolic agent, which
Marcus Treitl is a consultant for Covidien. The other authors declare no association with any individual, company, or organization having a vested interest in the subject matter/products mentioned in this article. Corresponding author: Karla Maria Eberhardt, MD, Institute for Clinical Radiology, Hospitals of the Ludwig Maximilian University of Munich, Pettenkoferstr. 8a, 80336 Munich, Germany. E-mail: [email protected]. de Q 2014 by the INTERNATIONAL SOCIETY
OF
ENDOVASCULAR SPECIALISTS
Available at www.jevt.org
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combines good controllability, excellent visibility, and a low risk of secondary recanalization, is well adapted to embolizing aortic type I endoleak cavities that typically exhibit a turbulent, high-velocity flow and have a high risk of non-target embolization. There are only a few published cases to date reporting the use of Onyx for this indication,2–4 including the report of our first 2 cases.5,6 We now present our experience with transcatheter embolization of type I endoleaks with Onyx in a larger group of patients, including followup data.
METHODS Study Design and Patient Population This is a single-center, prospective, longitudinal study approved by the institutional review board. Written informed consent was obtained from all patients prior to initial treatment and any reinterventions. From February 2010 to February 2013, 130 patients underwent (T)EVAR in our institution. In addition to the final angiographic series obtained at the endograft procedures, all patients had a duplex ultrasound examination prior to discharge; suspicion of endoleak was investigated with computed tomographic angiography (CTA). The location of endoleaks was defined by the surgical classification of aortic segments (I: aortic root to origin of brachiocephalic trunk, II: origin of the brachiocephalic trunk to the left common carotid artery, III: origin of the left subclavian artery to diaphragm, IV: origin of the visceral arteries, and V: infrarenal aorta and iliac arteries. During the observation period, transcatheter embolization was selected as the therapy for 10 type I endoleaks in 8 patients (4 men; mean age 74.8 years, range 63–86) because the landing zone was too short for a stentgraft extension. The endoleaks in 6 patients were detected between 3 days to 2 weeks after the index stent-graft procedure. One endoleak was detected during the index procedure, but immediate treatment was not possible due to the patient’s condition. The other patient had developed an abdominal type Ia endoleak 9 years after the index procedure, which was classified as type II for
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more than 2 years. The time between diagnosis and treatment varied from 5 days to 2 months, mostly due to concomitant morbidities (Table 1). Four endoleaks were located in the thoracic aorta and 6 in the abdominal aorta. Three of the thoracic endoleaks were type Ia following TEVAR of non-dissecting thoracic aneurysms (patients #5, 6, 8; Table 1, Fig. 1). The other thoracic endoleak was a type Ib in a patient (#1) with abdominal endoleaks that had developed after a complex multistage treatment of a chronic type B aortic dissection. Initially, the dissection had been treated at another hospital with a bare metal stent in segment IV. Due to progressive growth of the aneurysm and after open surgery to implant a 3-vessel visceral artery bypass, 2 non-overlapping stent-grafts were implanted into the thoracic and the abdominal aorta and both developed type I endoleaks (Fig. 2). Four of the abdominal endoleaks were type Ia owing to insufficient proximal sealing (e.g., patient #4; Fig. 3). Two distinct abdominal endoleaks developed in one patient (#3) after EVAR of a thoracoabdominal aortic aneurysm with a normal segment IV diameter. The thoracic part of the aneurysm was treated with a tube stent-graft, and the abdominal part was treated with a bifurcated stent-graft that extended into the iliac arteries. A multilayer flow modulating stent (Multilayer Aneurysm Repair System; Cardiatis, Isnes, Belgium) was deployed in segment IV, but sealing was inadequate, causing 2 distinct abdominal endoleaks.
Procedure A transbrachial access was used in 3 cases and a transfemoral access in 7. After sheath placement and administration of 5000 units of heparin, a 4-F diagnostic catheter (Cordis Corporation, Johnson & Johnson Health Care Systems Inc., Piscataway, NJ, USA) was inserted over a standard guidewire under fluoroscopic guidance. The catheter acted as a guiding catheter and was placed between the aortic wall and the stent-graft to access the endoleak, followed by coaxial introduction of a dimethylsulfoxide (DMSO)–compatible microcatheter [2.7-F Progreat (Terumo Medical
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^ TABLE 1 Etiology, Type, and Location of the Endoleaks Aortic Pathology
Age, y/Sex
Initial Treatment
Type/Aortic Segment*
Detected After
Treated After
Pre-treated with bare stent in segment IV; Hybrid TEVAR þ EVAR with 3vessel visceral bypass EVAR
Ib/tho III; Ib/abd V
3d
2 mo
Unfit for open surgery; unsuitable for extension cuff due to visceral bypass
Ia/abd V
9y
2 y†
14 d
1 mo
Unsuitable for extension cuff Unfit for open surgery; unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff, aborted endostapling, and unfit for open surgery Unsuitable for extension cuff
1. 59/F
Chronic type B dissection extending to expanding infrarenal AAA
2. 86/M
Infrarenal AAA
3. 71/M
TAAA
TEVAR, EVAR, MARS for segment IV
Ib/abd IV; Ia/abd V
4. 70/M
Infrarenal AAA
EVAR
Ia/abd V
2d
5d
5. 77/F
TAA
TEVAR
Ia/tho II
14 d
1 mo
6. 76/M
TAA
TEVAR
Ia/tho II
3d
7d
7. 68/F
Infrarenal AAA
EVAR þ endostapling
Ia/abd V
5d
7d
8. 75/F
TAA
TEVAR
Ia/tho II
7d
14 d
Treatment Indication
^
^ AAA: abdominal aortic aneurysm, TAA: thoracic aortic aneurysm, EVAR: endovascular aneurysm repair, TEVAR: thoracic endovascular aortic repair, tho: thoracic, abd: abdominal, MARS: Multilayer Aneurysm Repair System. * Surgical definition of aortic segments: I: aortic root to origin of brachiocephalic trunk, II: origin of brachiocephalic trunk to the left common carotid artery, III: origin of left subclavian artery to diaphragm, IV: origin of the visceral arteries, and V: infrarenal aorta and iliac arteries. † The endoleak was declared as type II for 2 years before it was recognized as a type I.
Corporation, Somerset, NJ, USA) or Echelon 14 and Rebar-27 (Covidien, Mansfield, MA, USA)]. The correct position of the microcatheter tip within the endoleak was verified by contrast injection. It was also applied to mark the endoleak margins and to identify side branches as potential targets for nontarget embolization.7 Any feeding/draining side branches 3 mm in diameter or wide entry endoleaks were coil embolized [Concerto (Covidien) or MREye (Cook Medical Inc., Bloomington, IN, USA)] to prevent the uncontrolled outflow of Onyx into the side branches or beyond the stent-graft margin. Reducing blood flow velocity in this way diminished the risk of non-target embolization.
The angiogram visualized turbulent, highvelocity blood flow in 5 cases and side branches involved in the endoleak in 3 cases (1 inferior mesenteric and 2 lumbar arteries). Onyx LES (Covidien) was prepared according to the instructions for use. After preparation of the microcatheter, Onyx was slowly injected under fluoroscopic control at a steady rate of 0.3 mL/min. Embolization was always started at the area that was most distant to the entry of the endoleak; during injection, the microcatheter was slowly retracted to the entry to achieve complete filling. After the injection, the catheters were removed without any complication. Onyx-34 was used in most cases due to its higher viscosity; additional
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Figure 1 ^ (A) CTA scan of a large thoracic type Ia endoleak (black arrow) in a patient (#6) after TEVAR. (B) Access to the endoleak over the partially covered left subclavian artery, depicting contrast flow within the endoleak (white arrow). (C) Angiogram after microcatheter placement to determine the extent of the endoleak. (D) Injection of 31.5 mL of Onyx with different viscosities, and (E) finally occlusion of the left subclavian artery with a Vascular Plug II (black arrow). The endoleak was completely occluded in the final angiogram. (F) CTA 6 months later showed partial reperfusion next to the stent (black arrow). This was limited to the area shown; no reperfusion within the rest of the sac has been detected up to 14 months.
charges of Onyx-20 and Onyx-18 were employed if needed.
Follow-up Evaluation The follow-up schedule for thoracic endoleaks included CTA prior to discharge, after 6 and 12 months, and annually thereafter. Abdominal endoleaks were monitored with duplex ultrasound prior to discharge, after 3, 6, and 12 months, and annually thereafter. A CTA scan was performed after 6 and 12 months. If the duplex ultrasound prior to discharge showed an endoleak, a CTA scan was carried out immediately. Aortic diameters were measured using OsiriX (version 4.1.2; Pixmeo SARL, Bernex, Switzerland).
RESULTS Technical success of the procedure was achieved in all cases. Accessing the endoleak
cavity with the 4-F guiding catheter was possible in only 1 case, but this had no impact on technical success, as the DMSO-compatible microcatheter could be advanced into the endoleak cavity in all cases. The mean volume of Onyx used for abdominal endoleaks was 11.8 mL (range 3.0–25.5) and 19.4 mL (range 4.5–31.5) for thoracic endoleaks. The average duration of the procedure was 76.7 minutes (range 34.5–110.6), and the average radiation dose area product was 18.8 cGy*cm2 (range 10.6–55.8). Details of the procedure by patient are given in Table 2. The high viscosity of the Onyx-34 kept the growing Onyx cast connected to the catheter tip in 9 cases; in a large type Ia thoracic endoleak, the initial drops of Onyx formed a long string that streamed into the endoleak cavity but remained connected to the catheter. The subsequent Onyx injection formed the expected growing cast. There was non-target embolization owing to preliminary coil embo-
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Figure 2 ^ Type Ib endoleaks (A) in segment III (arrowhead) and (B) segment V (arrowhead) in a female patient (#1) with chronic type B dissection and growing thoracic and abdominal dissecting aneurysm. Note the visceral bypass next to the endoleak in B. (C) After advancing a 4-F catheter between the stent-graft and the aortic wall, the extent of the thoracic type Ib endoleak is seen. Note the intercostal outflow vessel. (D) The abdominal type Ib endoleak after advancing the 4-F catheter between the infrarenal aortic wall and the stentgraft from the distal end. Note the lumbar artery outflow. (E) Single shot exposure after the procedure without contrast demonstrating the two non-communicating type Ib endoleaks (arrows) completely filled with Onyx-34 (4.5 mL for the thoracic endoleak and 7.5 mL for the abdominal endoleak). There has been no endoleak reperfusion or sac expansion for 24 months.
lization of involved side branches in 3 cases using an average of 7 fibered bioactive coils. Additional amounts of Onyx-20 and Onyx-18 were used in 2 cases as there was not enough Onyx-34 in stock. The less viscous Onyx formulations were used only after pre-embolization of a large portion of the endoleak with Onyx-34 to minimize the risk of non-target embolization. Although the final angiogram always indicated complete endoleak occlusion, one severe reperfusion was found 2 days after
embolization of a late abdominal type Ia endoleak (patient #2). A second embolization failed, so the patient had endoanchors implanted. In a thoracic type Ia endoleak (patient #6), a follow-up CT scan demonstrated occlusion of the endoleak, but revealed a small stripe of contrast flow between the aortic wall and the stent-graft heading toward the endoleak cavity. This patient is monitored every 6 months for early detection of endoleak reperfusion or sac growth, which has not been detected so far. The procedure was clinically
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Figure 3 ^ (A,B) CTA demonstrating the large type Ia abdominal endoleak (white arrow in A, black arrow in B) in an enlarged infrarenal landing zone not suitable for placement of a bare or cuff stent (patient #4). (C) A microcatheter was introduced into the endoleak between the aortic wall and the stent-graft via a transbrachial 4-F catheter. (D,E) Large lumbar (white arrowhead in E) and mesenteric (black arrowhead in E) outflow vessels were embolized with detachable coils prior to Onyx embolization. (F) The entire endoleak was filled with a total of 9 mL of Onyx-34, starting at the deepest point within the endoleak cavity. Follow-up for 8 months did not reveal recurrence of the endoleak or sac growth.
successful in all other cases, and the endoleaks remained completely occluded with a mean follow-up of 13.2 months (range 8–24). Overall, the mean shrinkage of the abdominal aneurysm was 0.6 cm (range 0.1–0.3) within the first 6 months and 1.2 cm (range 0.3–2.2) after 12 months. The mean reductions in diameter for thoracic aneurysms after 6 and 12 months were 0.4 and 0.9 cm (range 0.4– 1.3), respectively. Aneurysm growth was not detected in any case. No procedural complications, such as non-target embolization, access site sequelae, or renal failure, were observed. No Onyx or DMSO-associated complications, such as allergic reactions, bronchospasm, or pulmonary edema, were detected. The mean volume of Onyx injected
and the amount of DMSO were far below the toxic dose range of 600 mg/kg body weight.8
DISCUSSION Type I endoleaks place patients at risk for sac enlargement or rupture, and since spontaneous resolution is very rare, these leaks demand specific treatment.7,9 Balloon angioplasty of the leaking site during the index procedure is the simplest method, but implantation of additional bare metal stents or extension cuffs is often employed. Endoanchors are a new endovascular means of enhancing proximal endograft fixation.10,11 However, they need a 16-F access system, which in a reintervention may require an access site cutdown. No case of endoanchor
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^ TABLE 2 Details of the Embolization Procedures and Outcomes Patient
Access / Sheath Size, F
1
RCFA/7
34
2 3
RCFA/6 RCFA/6
34 34
4 5 6
RCFA/6 Right BA/6 Left BA/6
7
LCFA/7
8
Right BA/6
34 34 34 20 18 34 18 34
Onyx Type
Onyx Volume, mL 4.5 (th)/ 7.5 (abd) 3 12 (Ib)/ 13.5 (Ia) 9 25.5 18 10.5 3 15 10.5 16
Coil Type / Count
Endoleak Occlusion
DAP, cGy*cm2
Time, min
Follow-up, mo
—
20.9
69.2
24
— Concerto/10 Concerto/8 Concerto/3 — —
Yes Yes No* Yes Yes Yes Yes Yes†
11.1 55.8
34.5 94.2
12 12
N/A 14.8 10.6
63.0 59.7 80.2
8 8 14
—
Yes
32.0
110.6
9
—
Yes
23.6
102.0
9
^
^ DAP: dose area product, RCFA: right common femoral artery, BA: brachial artery, LCFA: left common femoral artery. * No flow detected post procedure, but recurrence after 6 months. Repeat transcatheter embolization failed; now planned for vascular endostapling procedure. † Flow between the aortic wall and stent-graft was detected during follow-up. Neither the endoleak cavity nor the sac itself was perfused.
fracture or migration has been reported so far. One of our patients (#7) had endoanchors during EVAR to treat an abdominal type Ia endoleak, but the procedure was inadequate because only 5 endoanchors could be implanted in the limited space, and the endoleak persisted. Transcatheter embolization of aortic endoleaks is rarely applied, although the procedure is not technically challenging for interventionists with adequate training. It is fast, does not require general anesthesia, and entails only a short hospital stay, so both the patient and the healthcare system benefit. However, there are only a few embolic agents that can be applied securely under high-flow conditions. Thrombin is frequently used for ultrasound-guided injections of iatrogenic pseudoaneurysms. It was tested for treatment of endoleaks,12,13 but it was associated with a high risk of recanalization and a reasonable risk of reflux and non-target embolization under high-flow conditions. N-butyl cyanoacrylate (NBCA), a component of several synthetic glues, is already used for the treatment of type I endoleaks.14 The combination of ethiodol and NBCA acts as a permanent occluder and is controllable under high-flow conditions, but the use of NBCA requires extensive expertise, as the
catheter often occludes after a few injections or can be entrapped in the injected cast.1,8 Coils are frequently used for embolization of type II endoleaks,15 and there are few reports of successful treatment of type I endoleaks.16 However, coil embolization of large cavities is associated with a relevant risk of recanalization, since coils may cause small recesses that cannot be sufficiently occluded. Platinum coils, furthermore, cause CT beam hardening artifacts and limit diagnostic imaging in follow-up examinations. Onyx was initially approved for treatment of intracranial arteriovenous malformations and, in comparison to other embolic agents, it showed significantly lower recanalization rates and a lower rate of inflammatory reactions of the vessel wall.17 As Onyx-18 and Onyx-34 are approved for peripheral application, they are increasingly used for treatment of type I and II endoleaks1,18,19 and aortic pseudoaneurysms.5,20 General application steps and technical details have been reported previously.1,8 Embolization with Onyx is well tolerated and no adverse events, such as anaphylactic symptoms, psychotic episodes, or respiratory distress syndromes,6,8 have yet been reported in peripheral application or observed in our
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cohort. The injection is usually painless, although high concentrations of DMSO can irritate the endothelium. Only one patient (#5) of the cohort mentioned slight prickling during the first seconds of the embolization when the DMSO filling the dead space volume of the microcatheter was injected. General or regional anesthesia was not necessary. No access site complications were observed because the microcatheter is coaxially introduced into a 4-F diagnostic catheter to ensure a stable position. Onyx-34 is about twice as viscous as Onyx18 and is adequate for embolizations under high-flow conditions. The first drops of Onyx should be injected very slowly so that they can form a plug around the microcatheter tip that prevents further backflow. The catheter is slowly retracted to the entry zone during injection, while the target area is progressively filled with Onyx. Since the copolymer is non-adhesive, catheter tip entrapment is unlikely, at least if the catheter is ,1.5 cm into the cast. Copolymerization takes about 5 minutes and starts at the outer layers, which prolongs the injection times and allows correct dosage, while the distribution of Onyx within the target area can be observed. Embolization may also be interrupted for a control angiogram to prevent non-target embolization.1,8 The viscosity of Onyx ensures contact between the injected cast and the residual column within the microcatheter, minimizing the risk of non-target embolization, which also enables occlusion of the proximal orifice of side branches (Fig. 3). One case (patient #6) had a high antegrade flow that entrained the initial cast, forcing it into a string-like configuration, but it was not disconnected from the microcatheter and deployed safely. Protective measures, such as previous coil embolization of side branches, are therefore not necessary. Onyx can be combined with bare metal stents, extension grafts or cuffs, and endoanchors.21 EVAR and endoleak embolization with Onyx may be combined within the one session when the development of an endoleak is expected immediately after stent placement due to deficiencies of the landing zone.6 The combination of both procedures may be a bailout procedure for selected
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patients with an anomalous configuration of the aneurysm that exceeds the measurements of the stent-grafts. The mean shrinkage of the abdominal aneurysm was greater than for thoracic aneurysms, but it may improve with growing experience. The procedure failed in only patient #2 who underwent treatment for a late abdominal type Ia endoleak appearing 9 years after EVAR. Endoanchoring is now planned for this patient. Additional embolization with coils was applied in 3 cases as an additional precaution when angiography revealed very high-flow conditions or a large entry site. However, additional embolization with coils is not mandatory and can be associated with potential drawbacks. Coils may prohibit complete spread of the liquid embolic agent within the endoleak by causing small recesses. This bears a relevant risk of recanalization and limits further treatment options, but was not observed in the cohort presented. Drawbacks of the procedure are the costs of Onyx and the high radiation doses in our cohort. The high radiation exposure was due to the lack of experience with this new procedure and can be reduced dramatically, for example, by using high magnification or small fields of view and by reducing the frame rate per second for fluoroscopic imaging (one image per 3 seconds or lower). This maneuver reduces the radiation doses by more than half, achieving values comparable to the treatment alternatives mentioned earlier. Reimbursement by the healthcare system is still lacking. Consequently, the publication of all experiences with this new procedure is required to collect data for negotiations with health insurance companies. This issue has already been discussed in Germany and other countries will soon follow. To the best of our knowledge, the largest published case series enrolled 6 patients.2,3 The present cohort adds 10 type I endoleaks in 8 patients to this experience.
Limitations First of all, the sample size was very small and the follow-up was rather short. Data on the potential action of Onyx as a pressure transmitter are not available yet, but it is
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known that thrombus can transmit pressure to the aneurysm sac, which may cause it to grow. This could also be true for Onyx, but it has to be addressed in animal studies. The tantalum content of Onyx ensures its fluoroscopic visualization, but it can also disguise the tip of the microcatheter during embolization. It is therefore recommended that a stable position of the microcatheter is maintained to minimize the risk of non-target embolization. 2 Tantalum results in pronounced CT beam hardening artifacts that interfere with the imaging quality of the follow-up examinations. Therefore, diagnostic information from follow-up CTA is limited. Color Doppler sonography with or without contrast enhancement was applied in the cohort presented as an alternative surveillance modality. Its combination with CT-based sac diameter measurements makes the detection of endoleak reperfusion possible. Finally, the means and timing of treatment of type I endoleaks are still under debate. Although spontaneous occlusion of type I endoleaks may occur, we have never observed one, so it is our policy to treat them promptly after detection according to the practice guidelines of the European Society of Vascular Surgery22 for management of aortic aneurysms.
Conclusion Onyx is well tolerated by patients and exhibits several characteristics that increase the safety of embolization under high-flow conditions. The results with this technique are promising, with high primary success rates, absence of complications, and satisfying midterm results. Onyx is associated with low recanalization rates and can be combined with other endovascular devices.
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3. Henrikson O, Roos H, Falkenberg M. Ethylene vinyl alcohol copolymer (Onyx) to seal type 1 endoleak. A new technique. Vascular. 2011;19: 77–81. 4. Grisafi JL, Boiteau G, Detschelt E, et al. Endoluminal treatment of type Ia endoleak with Onyx. J Vasc Surg. 2010;52:1346–1349. 5. Eberhardt KM, Treitl M, Sadeghi-Azandaryani M. An endovascular technique for treatment of high-risk iatrogenic aortic pseudoaneurysms with the ethylene vinyl alcohol copolymer Onyx and aortic stent grafting. Rofo. 2012;184:1163– 1165. 6. Sadeghi-Azandaryani M, Strube H, Heyn J, et al. Penetrating aortic ulcer in the infrarenal stent-graft landing zone: treatment with coils and the ethylene vinyl alcohol copolymer Onyx. J Endovasc Ther. 2011;18:123–129. 7. Rosen RJ, Green RM. Endoleak management following endovascular aneurysm repair. J Vasc Interv Radiol. 2008;19:S37–43. 8. Vaidya S, Tozer KR, Chen J. An overview of embolic agents. Semin Interv Radiol. 2008;25: 204–215. 9. Veith FJ, Baum RA, Ohki T, et al. Nature and significance of endoleaks and endotension: summary of opinions expressed at an international conference. J Vasc Surg. 2002;35:1029– 1035. 10. Perdikides T, Melas N, Lagios K, et al. Primary EndoAnchoring in the endovascular repair of abdominal aortic aneurysms with an unfavorable neck. J Endovasc Ther. 2012;19:707–715. 11. Donas KP, Kafetzakis A, Umscheid T, et al. Vascular endostapling: new concept for endovascular fixation of aortic stent-grafts. J Endovasc Ther. 2008;15:499–503. 12. Uthoff H, Katzen BT, Gandhi R, et al. Direct percutaneous sac injection for postoperative endoleak treatment after endovascular aortic aneurysm repair. J Vasc Surg. 2012;56:965– 972. 13. Gabrielli R, Rosati MS, Vitale S, et al. Thrombin injection and compression with removable guidewire in the treatment of postcatheterization femoral pseudoaneurysm. J Cardiovasc Surg (Torino). 2012 May 28. [Epub ahead of print] 14. Choi SY, Lee do Y, Lee KH, et al. Treatment of type I endoleaks after endovascular aneurysm repair of infrarenal abdominal aortic aneurysm: usefulness of N-butyl cyanoacrylate embolization in cases of failed secondary endovascular intervention. J Vasc Interv Radiol. 2011;22:155– 162.
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15. Funaki B, Birouti N, Zangan SM, et al. Evaluation and treatment of suspected type II endoleaks in patients with enlarging abdominal aortic aneurysms. J Vasc Interv Radiol. 2012; 23:866–872. 16. Faries PL, Cadot H, Agarwal G, et al. Management of endoleak after endovascular aneurysm repair: cuffs, coils, and conversion. J Vasc Surg. 2003;37:1155–1161. 17. Vanninen RL, Manninen I. Onyx, a new liquid embolic material for peripheral interventions: preliminary experience in aneurysm, pseudoaneurysm, and pulmonary arteriovenous malformation embolization. Cardiovasc Intervent Radiol. 2007;30:196–200. 18. Abularrage CJ, Patel VI, Conrad MF, et al. Improved results using Onyx glue for the treatment of persistent type 2 endoleak after
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endovascular aneurysm repair. J Vasc Surg. 2012;56:630–636. Massis K, Carson WG, Rozas A, et al. Treatment of type II endoleaks with ethylene-vinyl-alcohol copolymer (Onyx). Vasc Endovasc Surg. 2012; 46:251–257. Vulev I, Klepanec A, Madaric J, et al. Endovascular treatment of a giant aorto-ostial renal artery pseudoaneurysm. Ann Vasc Surg. 2011; 25:1140 e13-6. Stone JR, Evans AJ, Angle JF, et al. In vitro assessment of aortic stent-graft integrity following exposure to Onyx liquid embolic agent. J Vasc Interv Radiol. 2009;20:107–112. Moll FL, Powell JT, Fraedrich G, et al. Management of abdominal aortic aneurysms clinical practice guidelines of the European Society for Vascular Surgery. Eur J Vasc Endovasc Surg. 2011;41 Suppl 1: S1–S58.
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^ CLINICAL
INVESTIGATION ——————————————————————————
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Treatment of Type I Endoleaks Using Transcatheter Embolization With Onyx Karla Maria Eberhardt, MD1; Mojtaba Sadeghi-Azandaryani, MD2; Stefanie Worlicek, MD1; Thomas Koeppel, MD3; Maximilian F. Reiser, MD, FRCR1; and Marcus Treitl, MD, EBIR1 Institute for Clinical Radiology and 3Department of Vascular Surgery, Hospitals of the Ludwig Maximilian University of Munich, Germany. 2Division of Vascular Surgery, Department of Surgery, District Hospital of Erding, Germany.
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Purpose: To report a single-center experience with transcatheter embolization of type I endoleaks using the liquid embolic agent Onyx, an ethylene vinyl alcohol copolymer. Methods: Eight patients (4 men; mean age 74.8 years, range 63–86) with 10 type I endoleaks (6 abdominal and 4 thoracic) diagnosed 2 days to 9 years after endovascular repair were treated with Onyx embolization because cuff extension was precluded by an insufficient landing zone in 6 cases and an unsuitable aortic diameter in 2. Endoleaks were accessed with a 4-F diagnostic catheter and a coaxially introduced dimethylsulfoxide-compatible microcatheter. Onyx-34 was predominantly applied due to its high viscosity; patent side branches were coil embolized prior to Onyx delivery in 3 cases. Results: Technical success of the procedure was achieved in all cases. The mean volume of Onyx used for abdominal endoleaks was 11.8 mL (range 3.0–25.5) and 19.4 mL (range 4.5– 31.5) for thoracic endoleaks. The average duration of the procedure was 76.7 minutes (range 34.5–110.6), and the average radiation dose area product was 18.8 cGy*cm2 (range 10.6–55.8). Reperfusion of the endoleak was detected in one case 2 days after the procedure. A second case showed an occluded endoleak but a small trace of contrast between the aortic wall and the stent-graft. Non-target embolization was not found in any case. Mean follow-up was 13.2 months (range 8–24). The mean reduction in diameters for thoracic aneurysms after 6 and 12 months was 0.4 and 0.9 cm, respectively, and 0.6 and 1.2 cm, respectively, for abdominal aneurysms. Conclusion: Transcatheter embolization of type I endoleaks using Onyx is a simple, safe, and sustainable treatment option with a high primary success rate for cases in which stentgraft extension is not possible. The benefit of additional coil embolization remains uncertain. J Endovasc Ther. 2014;21:162–171 Key words: aortic aneurysm, endovascular aneurysm repair, type I endoleak, embolization, ethylene vinyl alcohol copolymer, Onyx, tantalum, coil embolization ^ ^
Because type I endoleaks are associated with an increased risk of rupture and aneurysmrelated death in patients who have undergone endovascular repair of abdominal or thoracic aneurysm [(T)EVAR], treatment is mandatory.
Ethylene vinyl alcohol copolymer Onyx is a newer alternative1 to the well known arsenal of materials for transcatheter embolization of type I endoleaks, such as coils, glues, and thrombin. This liquid embolic agent, which
Marcus Treitl is a consultant for Covidien. The other authors declare no association with any individual, company, or organization having a vested interest in the subject matter/products mentioned in this article. Corresponding author: Karla Maria Eberhardt, MD, Institute for Clinical Radiology, Hospitals of the Ludwig Maximilian University of Munich, Pettenkoferstr. 8a, 80336 Munich, Germany. E-mail: [email protected]. de Q 2014 by the INTERNATIONAL SOCIETY
OF
ENDOVASCULAR SPECIALISTS
Available at www.jevt.org
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combines good controllability, excellent visibility, and a low risk of secondary recanalization, is well adapted to embolizing aortic type I endoleak cavities that typically exhibit a turbulent, high-velocity flow and have a high risk of non-target embolization. There are only a few published cases to date reporting the use of Onyx for this indication,2–4 including the report of our first 2 cases.5,6 We now present our experience with transcatheter embolization of type I endoleaks with Onyx in a larger group of patients, including followup data.
METHODS Study Design and Patient Population This is a single-center, prospective, longitudinal study approved by the institutional review board. Written informed consent was obtained from all patients prior to initial treatment and any reinterventions. From February 2010 to February 2013, 130 patients underwent (T)EVAR in our institution. In addition to the final angiographic series obtained at the endograft procedures, all patients had a duplex ultrasound examination prior to discharge; suspicion of endoleak was investigated with computed tomographic angiography (CTA). The location of endoleaks was defined by the surgical classification of aortic segments (I: aortic root to origin of brachiocephalic trunk, II: origin of the brachiocephalic trunk to the left common carotid artery, III: origin of the left subclavian artery to diaphragm, IV: origin of the visceral arteries, and V: infrarenal aorta and iliac arteries. During the observation period, transcatheter embolization was selected as the therapy for 10 type I endoleaks in 8 patients (4 men; mean age 74.8 years, range 63–86) because the landing zone was too short for a stentgraft extension. The endoleaks in 6 patients were detected between 3 days to 2 weeks after the index stent-graft procedure. One endoleak was detected during the index procedure, but immediate treatment was not possible due to the patient’s condition. The other patient had developed an abdominal type Ia endoleak 9 years after the index procedure, which was classified as type II for
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more than 2 years. The time between diagnosis and treatment varied from 5 days to 2 months, mostly due to concomitant morbidities (Table 1). Four endoleaks were located in the thoracic aorta and 6 in the abdominal aorta. Three of the thoracic endoleaks were type Ia following TEVAR of non-dissecting thoracic aneurysms (patients #5, 6, 8; Table 1, Fig. 1). The other thoracic endoleak was a type Ib in a patient (#1) with abdominal endoleaks that had developed after a complex multistage treatment of a chronic type B aortic dissection. Initially, the dissection had been treated at another hospital with a bare metal stent in segment IV. Due to progressive growth of the aneurysm and after open surgery to implant a 3-vessel visceral artery bypass, 2 non-overlapping stent-grafts were implanted into the thoracic and the abdominal aorta and both developed type I endoleaks (Fig. 2). Four of the abdominal endoleaks were type Ia owing to insufficient proximal sealing (e.g., patient #4; Fig. 3). Two distinct abdominal endoleaks developed in one patient (#3) after EVAR of a thoracoabdominal aortic aneurysm with a normal segment IV diameter. The thoracic part of the aneurysm was treated with a tube stent-graft, and the abdominal part was treated with a bifurcated stent-graft that extended into the iliac arteries. A multilayer flow modulating stent (Multilayer Aneurysm Repair System; Cardiatis, Isnes, Belgium) was deployed in segment IV, but sealing was inadequate, causing 2 distinct abdominal endoleaks.
Procedure A transbrachial access was used in 3 cases and a transfemoral access in 7. After sheath placement and administration of 5000 units of heparin, a 4-F diagnostic catheter (Cordis Corporation, Johnson & Johnson Health Care Systems Inc., Piscataway, NJ, USA) was inserted over a standard guidewire under fluoroscopic guidance. The catheter acted as a guiding catheter and was placed between the aortic wall and the stent-graft to access the endoleak, followed by coaxial introduction of a dimethylsulfoxide (DMSO)–compatible microcatheter [2.7-F Progreat (Terumo Medical
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^ TABLE 1 Etiology, Type, and Location of the Endoleaks Aortic Pathology
Age, y/Sex
Initial Treatment
Type/Aortic Segment*
Detected After
Treated After
Pre-treated with bare stent in segment IV; Hybrid TEVAR þ EVAR with 3vessel visceral bypass EVAR
Ib/tho III; Ib/abd V
3d
2 mo
Unfit for open surgery; unsuitable for extension cuff due to visceral bypass
Ia/abd V
9y
2 y†
14 d
1 mo
Unsuitable for extension cuff Unfit for open surgery; unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff Unsuitable for extension cuff, aborted endostapling, and unfit for open surgery Unsuitable for extension cuff
1. 59/F
Chronic type B dissection extending to expanding infrarenal AAA
2. 86/M
Infrarenal AAA
3. 71/M
TAAA
TEVAR, EVAR, MARS for segment IV
Ib/abd IV; Ia/abd V
4. 70/M
Infrarenal AAA
EVAR
Ia/abd V
2d
5d
5. 77/F
TAA
TEVAR
Ia/tho II
14 d
1 mo
6. 76/M
TAA
TEVAR
Ia/tho II
3d
7d
7. 68/F
Infrarenal AAA
EVAR þ endostapling
Ia/abd V
5d
7d
8. 75/F
TAA
TEVAR
Ia/tho II
7d
14 d
Treatment Indication
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^ AAA: abdominal aortic aneurysm, TAA: thoracic aortic aneurysm, EVAR: endovascular aneurysm repair, TEVAR: thoracic endovascular aortic repair, tho: thoracic, abd: abdominal, MARS: Multilayer Aneurysm Repair System. * Surgical definition of aortic segments: I: aortic root to origin of brachiocephalic trunk, II: origin of brachiocephalic trunk to the left common carotid artery, III: origin of left subclavian artery to diaphragm, IV: origin of the visceral arteries, and V: infrarenal aorta and iliac arteries. † The endoleak was declared as type II for 2 years before it was recognized as a type I.
Corporation, Somerset, NJ, USA) or Echelon 14 and Rebar-27 (Covidien, Mansfield, MA, USA)]. The correct position of the microcatheter tip within the endoleak was verified by contrast injection. It was also applied to mark the endoleak margins and to identify side branches as potential targets for nontarget embolization.7 Any feeding/draining side branches 3 mm in diameter or wide entry endoleaks were coil embolized [Concerto (Covidien) or MREye (Cook Medical Inc., Bloomington, IN, USA)] to prevent the uncontrolled outflow of Onyx into the side branches or beyond the stent-graft margin. Reducing blood flow velocity in this way diminished the risk of non-target embolization.
The angiogram visualized turbulent, highvelocity blood flow in 5 cases and side branches involved in the endoleak in 3 cases (1 inferior mesenteric and 2 lumbar arteries). Onyx LES (Covidien) was prepared according to the instructions for use. After preparation of the microcatheter, Onyx was slowly injected under fluoroscopic control at a steady rate of 0.3 mL/min. Embolization was always started at the area that was most distant to the entry of the endoleak; during injection, the microcatheter was slowly retracted to the entry to achieve complete filling. After the injection, the catheters were removed without any complication. Onyx-34 was used in most cases due to its higher viscosity; additional
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Figure 1 ^ (A) CTA scan of a large thoracic type Ia endoleak (black arrow) in a patient (#6) after TEVAR. (B) Access to the endoleak over the partially covered left subclavian artery, depicting contrast flow within the endoleak (white arrow). (C) Angiogram after microcatheter placement to determine the extent of the endoleak. (D) Injection of 31.5 mL of Onyx with different viscosities, and (E) finally occlusion of the left subclavian artery with a Vascular Plug II (black arrow). The endoleak was completely occluded in the final angiogram. (F) CTA 6 months later showed partial reperfusion next to the stent (black arrow). This was limited to the area shown; no reperfusion within the rest of the sac has been detected up to 14 months.
charges of Onyx-20 and Onyx-18 were employed if needed.
Follow-up Evaluation The follow-up schedule for thoracic endoleaks included CTA prior to discharge, after 6 and 12 months, and annually thereafter. Abdominal endoleaks were monitored with duplex ultrasound prior to discharge, after 3, 6, and 12 months, and annually thereafter. A CTA scan was performed after 6 and 12 months. If the duplex ultrasound prior to discharge showed an endoleak, a CTA scan was carried out immediately. Aortic diameters were measured using OsiriX (version 4.1.2; Pixmeo SARL, Bernex, Switzerland).
RESULTS Technical success of the procedure was achieved in all cases. Accessing the endoleak
cavity with the 4-F guiding catheter was possible in only 1 case, but this had no impact on technical success, as the DMSO-compatible microcatheter could be advanced into the endoleak cavity in all cases. The mean volume of Onyx used for abdominal endoleaks was 11.8 mL (range 3.0–25.5) and 19.4 mL (range 4.5–31.5) for thoracic endoleaks. The average duration of the procedure was 76.7 minutes (range 34.5–110.6), and the average radiation dose area product was 18.8 cGy*cm2 (range 10.6–55.8). Details of the procedure by patient are given in Table 2. The high viscosity of the Onyx-34 kept the growing Onyx cast connected to the catheter tip in 9 cases; in a large type Ia thoracic endoleak, the initial drops of Onyx formed a long string that streamed into the endoleak cavity but remained connected to the catheter. The subsequent Onyx injection formed the expected growing cast. There was non-target embolization owing to preliminary coil embo-
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Figure 2 ^ Type Ib endoleaks (A) in segment III (arrowhead) and (B) segment V (arrowhead) in a female patient (#1) with chronic type B dissection and growing thoracic and abdominal dissecting aneurysm. Note the visceral bypass next to the endoleak in B. (C) After advancing a 4-F catheter between the stent-graft and the aortic wall, the extent of the thoracic type Ib endoleak is seen. Note the intercostal outflow vessel. (D) The abdominal type Ib endoleak after advancing the 4-F catheter between the infrarenal aortic wall and the stentgraft from the distal end. Note the lumbar artery outflow. (E) Single shot exposure after the procedure without contrast demonstrating the two non-communicating type Ib endoleaks (arrows) completely filled with Onyx-34 (4.5 mL for the thoracic endoleak and 7.5 mL for the abdominal endoleak). There has been no endoleak reperfusion or sac expansion for 24 months.
lization of involved side branches in 3 cases using an average of 7 fibered bioactive coils. Additional amounts of Onyx-20 and Onyx-18 were used in 2 cases as there was not enough Onyx-34 in stock. The less viscous Onyx formulations were used only after pre-embolization of a large portion of the endoleak with Onyx-34 to minimize the risk of non-target embolization. Although the final angiogram always indicated complete endoleak occlusion, one severe reperfusion was found 2 days after
embolization of a late abdominal type Ia endoleak (patient #2). A second embolization failed, so the patient had endoanchors implanted. In a thoracic type Ia endoleak (patient #6), a follow-up CT scan demonstrated occlusion of the endoleak, but revealed a small stripe of contrast flow between the aortic wall and the stent-graft heading toward the endoleak cavity. This patient is monitored every 6 months for early detection of endoleak reperfusion or sac growth, which has not been detected so far. The procedure was clinically
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Figure 3 ^ (A,B) CTA demonstrating the large type Ia abdominal endoleak (white arrow in A, black arrow in B) in an enlarged infrarenal landing zone not suitable for placement of a bare or cuff stent (patient #4). (C) A microcatheter was introduced into the endoleak between the aortic wall and the stent-graft via a transbrachial 4-F catheter. (D,E) Large lumbar (white arrowhead in E) and mesenteric (black arrowhead in E) outflow vessels were embolized with detachable coils prior to Onyx embolization. (F) The entire endoleak was filled with a total of 9 mL of Onyx-34, starting at the deepest point within the endoleak cavity. Follow-up for 8 months did not reveal recurrence of the endoleak or sac growth.
successful in all other cases, and the endoleaks remained completely occluded with a mean follow-up of 13.2 months (range 8–24). Overall, the mean shrinkage of the abdominal aneurysm was 0.6 cm (range 0.1–0.3) within the first 6 months and 1.2 cm (range 0.3–2.2) after 12 months. The mean reductions in diameter for thoracic aneurysms after 6 and 12 months were 0.4 and 0.9 cm (range 0.4– 1.3), respectively. Aneurysm growth was not detected in any case. No procedural complications, such as non-target embolization, access site sequelae, or renal failure, were observed. No Onyx or DMSO-associated complications, such as allergic reactions, bronchospasm, or pulmonary edema, were detected. The mean volume of Onyx injected
and the amount of DMSO were far below the toxic dose range of 600 mg/kg body weight.8
DISCUSSION Type I endoleaks place patients at risk for sac enlargement or rupture, and since spontaneous resolution is very rare, these leaks demand specific treatment.7,9 Balloon angioplasty of the leaking site during the index procedure is the simplest method, but implantation of additional bare metal stents or extension cuffs is often employed. Endoanchors are a new endovascular means of enhancing proximal endograft fixation.10,11 However, they need a 16-F access system, which in a reintervention may require an access site cutdown. No case of endoanchor
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^ TABLE 2 Details of the Embolization Procedures and Outcomes Patient
Access / Sheath Size, F
1
RCFA/7
34
2 3
RCFA/6 RCFA/6
34 34
4 5 6
RCFA/6 Right BA/6 Left BA/6
7
LCFA/7
8
Right BA/6
34 34 34 20 18 34 18 34
Onyx Type
Onyx Volume, mL 4.5 (th)/ 7.5 (abd) 3 12 (Ib)/ 13.5 (Ia) 9 25.5 18 10.5 3 15 10.5 16
Coil Type / Count
Endoleak Occlusion
DAP, cGy*cm2
Time, min
Follow-up, mo
—
20.9
69.2
24
— Concerto/10 Concerto/8 Concerto/3 — —
Yes Yes No* Yes Yes Yes Yes Yes†
11.1 55.8
34.5 94.2
12 12
N/A 14.8 10.6
63.0 59.7 80.2
8 8 14
—
Yes
32.0
110.6
9
—
Yes
23.6
102.0
9
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^ DAP: dose area product, RCFA: right common femoral artery, BA: brachial artery, LCFA: left common femoral artery. * No flow detected post procedure, but recurrence after 6 months. Repeat transcatheter embolization failed; now planned for vascular endostapling procedure. † Flow between the aortic wall and stent-graft was detected during follow-up. Neither the endoleak cavity nor the sac itself was perfused.
fracture or migration has been reported so far. One of our patients (#7) had endoanchors during EVAR to treat an abdominal type Ia endoleak, but the procedure was inadequate because only 5 endoanchors could be implanted in the limited space, and the endoleak persisted. Transcatheter embolization of aortic endoleaks is rarely applied, although the procedure is not technically challenging for interventionists with adequate training. It is fast, does not require general anesthesia, and entails only a short hospital stay, so both the patient and the healthcare system benefit. However, there are only a few embolic agents that can be applied securely under high-flow conditions. Thrombin is frequently used for ultrasound-guided injections of iatrogenic pseudoaneurysms. It was tested for treatment of endoleaks,12,13 but it was associated with a high risk of recanalization and a reasonable risk of reflux and non-target embolization under high-flow conditions. N-butyl cyanoacrylate (NBCA), a component of several synthetic glues, is already used for the treatment of type I endoleaks.14 The combination of ethiodol and NBCA acts as a permanent occluder and is controllable under high-flow conditions, but the use of NBCA requires extensive expertise, as the
catheter often occludes after a few injections or can be entrapped in the injected cast.1,8 Coils are frequently used for embolization of type II endoleaks,15 and there are few reports of successful treatment of type I endoleaks.16 However, coil embolization of large cavities is associated with a relevant risk of recanalization, since coils may cause small recesses that cannot be sufficiently occluded. Platinum coils, furthermore, cause CT beam hardening artifacts and limit diagnostic imaging in follow-up examinations. Onyx was initially approved for treatment of intracranial arteriovenous malformations and, in comparison to other embolic agents, it showed significantly lower recanalization rates and a lower rate of inflammatory reactions of the vessel wall.17 As Onyx-18 and Onyx-34 are approved for peripheral application, they are increasingly used for treatment of type I and II endoleaks1,18,19 and aortic pseudoaneurysms.5,20 General application steps and technical details have been reported previously.1,8 Embolization with Onyx is well tolerated and no adverse events, such as anaphylactic symptoms, psychotic episodes, or respiratory distress syndromes,6,8 have yet been reported in peripheral application or observed in our
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cohort. The injection is usually painless, although high concentrations of DMSO can irritate the endothelium. Only one patient (#5) of the cohort mentioned slight prickling during the first seconds of the embolization when the DMSO filling the dead space volume of the microcatheter was injected. General or regional anesthesia was not necessary. No access site complications were observed because the microcatheter is coaxially introduced into a 4-F diagnostic catheter to ensure a stable position. Onyx-34 is about twice as viscous as Onyx18 and is adequate for embolizations under high-flow conditions. The first drops of Onyx should be injected very slowly so that they can form a plug around the microcatheter tip that prevents further backflow. The catheter is slowly retracted to the entry zone during injection, while the target area is progressively filled with Onyx. Since the copolymer is non-adhesive, catheter tip entrapment is unlikely, at least if the catheter is ,1.5 cm into the cast. Copolymerization takes about 5 minutes and starts at the outer layers, which prolongs the injection times and allows correct dosage, while the distribution of Onyx within the target area can be observed. Embolization may also be interrupted for a control angiogram to prevent non-target embolization.1,8 The viscosity of Onyx ensures contact between the injected cast and the residual column within the microcatheter, minimizing the risk of non-target embolization, which also enables occlusion of the proximal orifice of side branches (Fig. 3). One case (patient #6) had a high antegrade flow that entrained the initial cast, forcing it into a string-like configuration, but it was not disconnected from the microcatheter and deployed safely. Protective measures, such as previous coil embolization of side branches, are therefore not necessary. Onyx can be combined with bare metal stents, extension grafts or cuffs, and endoanchors.21 EVAR and endoleak embolization with Onyx may be combined within the one session when the development of an endoleak is expected immediately after stent placement due to deficiencies of the landing zone.6 The combination of both procedures may be a bailout procedure for selected
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patients with an anomalous configuration of the aneurysm that exceeds the measurements of the stent-grafts. The mean shrinkage of the abdominal aneurysm was greater than for thoracic aneurysms, but it may improve with growing experience. The procedure failed in only patient #2 who underwent treatment for a late abdominal type Ia endoleak appearing 9 years after EVAR. Endoanchoring is now planned for this patient. Additional embolization with coils was applied in 3 cases as an additional precaution when angiography revealed very high-flow conditions or a large entry site. However, additional embolization with coils is not mandatory and can be associated with potential drawbacks. Coils may prohibit complete spread of the liquid embolic agent within the endoleak by causing small recesses. This bears a relevant risk of recanalization and limits further treatment options, but was not observed in the cohort presented. Drawbacks of the procedure are the costs of Onyx and the high radiation doses in our cohort. The high radiation exposure was due to the lack of experience with this new procedure and can be reduced dramatically, for example, by using high magnification or small fields of view and by reducing the frame rate per second for fluoroscopic imaging (one image per 3 seconds or lower). This maneuver reduces the radiation doses by more than half, achieving values comparable to the treatment alternatives mentioned earlier. Reimbursement by the healthcare system is still lacking. Consequently, the publication of all experiences with this new procedure is required to collect data for negotiations with health insurance companies. This issue has already been discussed in Germany and other countries will soon follow. To the best of our knowledge, the largest published case series enrolled 6 patients.2,3 The present cohort adds 10 type I endoleaks in 8 patients to this experience.
Limitations First of all, the sample size was very small and the follow-up was rather short. Data on the potential action of Onyx as a pressure transmitter are not available yet, but it is
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known that thrombus can transmit pressure to the aneurysm sac, which may cause it to grow. This could also be true for Onyx, but it has to be addressed in animal studies. The tantalum content of Onyx ensures its fluoroscopic visualization, but it can also disguise the tip of the microcatheter during embolization. It is therefore recommended that a stable position of the microcatheter is maintained to minimize the risk of non-target embolization. 2 Tantalum results in pronounced CT beam hardening artifacts that interfere with the imaging quality of the follow-up examinations. Therefore, diagnostic information from follow-up CTA is limited. Color Doppler sonography with or without contrast enhancement was applied in the cohort presented as an alternative surveillance modality. Its combination with CT-based sac diameter measurements makes the detection of endoleak reperfusion possible. Finally, the means and timing of treatment of type I endoleaks are still under debate. Although spontaneous occlusion of type I endoleaks may occur, we have never observed one, so it is our policy to treat them promptly after detection according to the practice guidelines of the European Society of Vascular Surgery22 for management of aortic aneurysms.
Conclusion Onyx is well tolerated by patients and exhibits several characteristics that increase the safety of embolization under high-flow conditions. The results with this technique are promising, with high primary success rates, absence of complications, and satisfying midterm results. Onyx is associated with low recanalization rates and can be combined with other endovascular devices.
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