Annals of Vascular Surgery
Volume 22, Issue 1 , Pages 30-36, January 2008

Endovascular Stent-Graft Repair of Failed Endovascular Abdominal Aortic Aneurysm Repair

Division of Vascular Surgery, Department of Surgery, Mount Sinai School of Medicine, New York, NY

published online 17 December 2007.

Article Outline

Despite high initial technical success, the long-term durability of endovascular abdominal aortic aneurysm repair (EVAR) continues to be a concern. Following EVAR, patients can experience endoleaks, device migration, device fractures, or aneurysm growth that may require intervention. The purpose of this study was to review all patients treated with secondary endovascular devices at our institution for failed EVAR procedures. Over an 8-year period, 988 patients underwent EVAR, of whom 42 (4.3%) required secondary interventions involving placement of additional endovascular devices. Data regarding patient characteristics, aneurysm size, initial device type, time until failure, failure etiology, secondary interventions, and outcomes were reviewed. The mean time from initial operation until second operation was 34.1 months. Failures included type I endoleaks in 38 patients (90.5%), type III endoleaks in two patients (4.8%), and enlarging aneurysms without definite endoleaks in two patients (4.8%). The overall technical success rate for secondary repair was 92.9% (39/42). Perioperative complications occurred in nine patients (21.4%), including wound complications (n = 6), cerebrovascular accident (CVA) (n = 1), foot drop (n = 1), and death (n = 1). Mean follow-up following secondary repair was 16.4 months (range 1-50). Eighty-six percent of patients treated with aortouni-iliac devices had successful repairs compared to 45% of patients treated with proximal cuffs. Ten patients (23.8%) had persistent or recurrent type I or type III endoleaks following revision. Of these, four had tertiary interventions, including two patients who had additional devices placed. Failures following EVAR occur in a small but significant number of patients. When anatomically possible, endovascular revision offers a safe means of treating these failures. Aortouni-iliac devices appear to offer a more durable repair than the proximal cuff for treatment of proximal type I endoleaks. Midterm results indicate that these patients may require additional procedures but have a low rate of aneurysm-related mortality. Longer-term follow-up is necessary to determine the durability of these endovascular revisions.

 

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Introduction 

Endovascular abdominal aortic aneurysm (AAA) repair (EVAR) has been shown in midterm studies to be a safe and effective means of treating AAAs.1, 2, 3, 4, 5 In comparison to conventional open repair, EVAR has a lower associated morbidity and shorter hospital stay.6, 7, 8, 9 Despite its high initial technical success, the long-term durability of EVAR continues to be a concern, and all patients require lifelong radiographic surveillance to assure that aneurysm exclusion is maintained. Following EVAR, patients may experience endoleaks, device migration, device fractures, or aneurysm growth that requires intervention to prevent aneurysm rupture. These interventions may require the placement of additional endovascular devices or, in select cases, conversion to conventional open repair. The purpose of this study was to evaluate the clinical outcomes of patients treated with supplemental endovascular devices for failed primary EVAR.

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Methods 

A review of a prospectively maintained database was performed for all patients undergoing EVAR at our institution between January 1997 and July 2005. Patients gave written informed consent and were treated in accordance with the institutional review board of the Mount Sinai Medical Center. All patients underwent preoperative contrast-enhanced computed tomography (CT) and arteriography to evaluate AAA anatomy. All initial EVAR procedures were performed in the operating room under epidural or spinal anesthesia with portable C-arm fluoroscopy. Access to the arterial system was via cutdown across one or both femoral arteries. Completion angiograms were obtained in all patients following deployment of the stent graft to confirm aneurysm exclusion.

Follow-up for all patients undergoing EVAR consisted of an office visit with the operating surgeon as well as plain abdominal radiography and three-phase contrast-enhanced CT angiography at 1 month, 6 months, 12 months, and annually thereafter. CT angiography consisted of a noncontrast study to assess for calcium in the sac followed by dynamic and late-phase angiographic assessment of the abdominal aorta. Our definition of “failure” was the development of a type I or type III endoleak or sac enlargement without a documented endoleak following the initial repair. Patients who developed a type II endoleak requiring intervention were not included in this study since these endoleaks were treated by methods other than endografts. Patients who were suspected of having a type I or type III endoleak on CT scan underwent a diagnostic angiogram to confirm the presence and location of the endoleak. Patients were prospectively followed, and data including demographics, aneurysm size, medical comorbidities, complications, and secondary interventions were obtained. Preoperative, perioperative, and postoperative follow-up data were collected from these medical records and archived radiology studies. Patients who underwent secondary procedures with the placement of additional endovascular devices were identified and form the study group of this report. Association between success rates and type of secondary intervention was calculated with Fisher's exact test using SPSS software (SPSS, Chicago, IL). Survival curves for patients undergoing intervention for endoleaks were calculated using GraphPad Prism 4 (GraphPad Software, San Diego, CA).

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Results 

Over the 8-year time period reviewed, 988 patients underwent EVAR at our institution. A total of 60 patients were identified who required revision. Forty-two (4.3%) patients underwent secondary interventions involving placement of additional endovascular devices. Eighteen patients (1.8%) underwent conversion to open repair following EVAR due to neck dilatation with no sufficient proximal neck to extend the repair. Of the 42 patients who underwent endovascular revisions, two had their initial operation at an outside institution. One patient initially had an open AAA repair and then went on to have his first endovascular procedure to treat pseudoaneurysms which developed at both the proximal and distal aspects of his original graft, followed by endovascular revision.

The patients' demographics and comorbidities are presented in Table I. Initial preoperative mean aneurysm sac size was 60.5 mm (range 48-82). Mean neck width was 25.0 mm (range 18-32). Table II reports the initial devices implanted in the original group and the devices used in the study group. The majority of failed devices (45%) were Talent (Medtronic World Medical, Sunrise, FL) bifurcated endografts. The two tube endografts, the Talent and the Vanguard (Boston Scientific, Oakland, NJ), together made up 30% of failed devices. AneuRx bifurcated grafts (Medtronics/AVE, Santo Rosa, CA) made up 5% of the failures. Etiology of failures included proximal and distal type I endoleaks or both, type III endoleaks, and enlarging aneurysms without definite endoleaks (Table III). The majority of the tube-graft failures were distal type I endoleaks (10/13). Among the bifurcated devices, the proportion of proximal to distal type I endoleaks was equal. Three of the type I endoleaks were associated with stent migration. Prior to the second endovascular repair, 11 patients underwent internal iliac artery coil embolization as part of a staged procedure before placing additional devices to avoid potential future type II endoleaks.

Table I. Patient characteristics
n (%)
Sex (M/F)33/9 (78.6/21.4)
Age (mean)76.0
CVA/transient ischemic attack7 (16.7)
Coronary artery disease26 (61.9)
Chronic obstructive pulmonary disease23 (54.8)
Diabetes mellitus1 (2.4)
Hypercholesterolemia28 (66.7)
Hypertension32 (76.2)
Malignancy9 (21.4)
Table II. Devices used at initial operation
Devices requiring secondary interventions (total = 42), n (%)Total devices implanted (total = 988), n (%)Device-specific failure rate (%)
Talent bifurcated19 (45)433 (44)4
Talent tube8 (19)44 (4)18
Vanguard tube5 (12)8 (1)63
AneuRx bifurcated5 (12)102 (10)5
Talent aortouni-iliac2 (5)108 (11)2
Gore1 (2)93 (9)1
Cordis/Teramed1 (2)44 (4)2
Ancure bifurcated1 (2)9 (1)11
MEGS aortouni-iliac0109 (11)0
Vanguard bifurcated029 (3)0
Zenith09 (1)0
Table III. Etiology of primary failures
n (%)
Proximal type I endoleak19 (45)
Distal type I endoleak16 (38)
Proximal and distal type I endoleaks3 (7)
Type III endoleak2 (5)
Enlarging aneurysm without definite endoleak2 (5)

The mean time from initial operation until second operation was 34.1 months (range 1-92). At the time of the second operation, the aneurysm sac size was greater than prior to initial repair, with a mean sac size of 67.5 mm (range 48-118). In this revision group with proximal type I endoleaks, films were available for review of neck characteristics in 20 of 22 patients. The mean neck width and length in this group were 26.1 mm (range 19-32) and 18.6 mm (range 5-55), respectively.

A variety of different devices were used for the secondary endovascular procedures (Table IV). The most common device utilized was the Talent aortouni-iliac, which was used in one-third of the cases. Talent bifurcated devices were used in seven cases, all for repair of failed tube grafts. Other devices used were Talent proximal cuffs, Talent distal extensions, and others. The rate of primary technical success, defined as the absence of type I or type III endoleak at the end of the case, was 93%. Perioperative complications occurred in nine patients (21%), including wound complications (four groin hematomas, one groin infection, and one lymphocele, none of which required surgical intervention), CVA (one patient), and foot drop (one patient). There was a single mortality in the perioperative period due to a ruptured thoracic aortic aneurysm. The mean follow-up was 16.4 months (range 1-50) following the second operation for 40 patients in the endovascular revision group. This excludes one patient who was lost to follow-up. There were three late complications: one limb occlusion, one infected femoral-femoral bypass graft, and a mortality from a ruptured AAA. The patient who expired from a ruptured AAA was initially treated for a distal type I endoleak following insertion of a Talent bifurcated device. One year later, she developed a proximal type I endoleak; however, she declined open conversion and expired 2 months later due to AAA rupture.

Table IV. Devices used for endovascular revisions
Devicen (%)
AneuRx proximal cuff1 (2.4)
AneuRx distal extension + Palmaz stent1 (2.4)
Gore distal extension3 (7.1)
Palmaz stent1 (2.4)
Talent aorto-aorto tube1 (2.4)
Talent aortouni-iliac14 (33.3)
Talent aortouni-iliac + Palmaz stent1 (2.4)
Talent bifurcated7 (16.7)
Talent distal extension3 (7.1)
Talent proximal cuff7 (16.7)
Talent proximal cuff + distal extension1 (2.4)
Talent proximal cuff + Palmaz stent1 (2.4)
Vanguard proximal cuff1 (2.4)

Following the secondary repair, there were 10 recurrent or persistent endoleaks, making the overall success rate for sealing of treated endoleaks 76%. Of the 10 secondary failures, nine were type I endoleaks and one was a type III endoleak. All type I endoleaks were from the proximal attachment site. Of these, three were identified intraoperatively, three 1 month postoperatively, and three distantly. Kaplan-Meier analysis of the success rate of sealing of proximal type I endoleaks following secondary interventions is shown in Figure 1. No cases of recurrent endotension were observed. Table V reports the success of secondary intervention in relation to device type. Eighty-six percent of the aortouni-iliac devices used were successful at achieving a seal, while only 45% of the cuffs used achieved a seal. Additionally, bifurcated devices used for failed tube grafts achieved a seal in 86% of cases.

Table V. Success of secondary intervention related to device configuration
Total devices (n = 42)Successful (n = 32, 76%)
Aortouni-iliac1513 (87%)∗
Proximal cuffs115 (45%)∗
Distal extensions87 (88%)
Bifurcated76 (86%)
Tube11 (100%)

∗Statistically significant (p < 0.05) using Fisher's exact test.

Four out of the nine patients with recurrent type I endoleaks underwent additional procedures. Two underwent insertion of proximal cuffs. One cuff placement was successful at achieving endoleak seal. The other failed to achieve a seal and required an additional cuff placement. Two patients underwent coil embolization of the aneurysm sac. The type III endoleak developed in a patient who initially underwent placement of a Vanguard tube device, developed a distal type I endoleak, and was subsequently treated with a Talent bifurcated device. He underwent successful placement of a Gore (Flagstaff, AZ) extension limb to bridge the endoleak between the components of the Talent device. None of the patients who failed a secondary repair underwent open surgery. Patients not treated by endovascular methods were observed. During the follow-up of these patients, four mortalities occurred but only one was aneurysm-related.

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Discussion 

EVAR is associated with lower morbidity and shorter recovery time compared to standard open repair.6, 7, 8, 9 However, midterm results have shown that patients undergoing EVAR will require a second procedure in 15-35% of cases for all types of endoleak complications.10, 11, 12, 13 There is a subset of patients who will develop EVAR failures in the form of type I or type III endoleaks, aneurysm enlargement without demonstrable endoleaks, or aneurysm rupture who will require additional device implantation or conversion to open repair.

EVAR failure has been addressed in multiple studies. First-generation tube devices were prone to distal type I endoleaks and migration due to distal neck degeneration and failure.14 Since these initial devices, the vast majority of devices implanted have had either a bifurcated or aortouni-iliac configuration. While these configurations have avoided the majority of the distal aortic neck failures encountered with the first-generation devices, they continue to be plagued by proximal neck degeneration, migration, and endoleaks. Failure of these devices at the proximal neck has been related to neck dilatation in patients with large aneurysms and necks with circumferential thrombus, significant tortuosity, and angulation.15, 16 Similarly, migration is increased in patients with large AAAs as well as in smokers and hypertensive patients.17

In efforts to overcome these anatomic limitations, device development has been focused on means of generating a better proximal seal. This has led to the placement of hooks and barbs for direct structural adherence to the aortic wall. Additionally, efforts have been made to oversize stents, to increase the radial force of stents, and to use balloon expansion to improve the proximal seal zone. In particular, the Talent device has been studied in complicated proximal necks and associated with favorable outcomes.18, 19

Despite these advances, there continues to be a subgroup of patients who undergo EVAR and ultimately require a secondary operation for repair failure. Although the percentage of patients who require open conversion is low, with reported rates of 0.5-4.5%,20, 21, 22 the mortality of these operations exceed 20%.21 Given this high risk, the question that surgeons must address is whether these patients can continue to be managed using endovascular techniques or if they require conversion to open repair. For the majority of these patients, the initial procedure was performed as an endovascular repair because their comorbidities were prohibitive for an open repair. Clearly, these comorbidities are present, if not worse, at the time of their need for revision, while the minimally invasive benefits of endovascular repair are maintained even in secondary or tertiary procedures. Additional considerations before revision is undertaken include surgeon expertise with both endovascular and open techniques as well as device availability. Perhaps the most limiting factor is the aortic anatomy following the initial operation. In particular, the presence of a short, angulated proximal neck may preclude endovascular options.

For patients to undergo an endovascular revision of their failed initial EVAR, the most important anatomic factor is an adequate length of undilated aorta distal to the renal arteries. This is less of a concern distally, where aneurysmal disease of the iliacs can be managed with further graft extension and relatively liberal coverage of the internal iliac arteries. The choice of device for endovascular revision is individualized to the patient, the initial device, the etiology of the failure, and the present aortic anatomy. Talent proximal cuffs, which were used frequently in our group, offer both increased proximal suprarenal attachment and increased graft coverage. However, this device is not yet commercially available in the United States. The Zenith Renu AAA Ancillary Graft (Cook, Bloomington, IN) offers some of the same features as the Talent proximal cuff, including suprarenal fixation. Alternatively, a Palmaz stent (Johnson & Johnson, New Brunswick, NJ) provides some of the same benefits and is a useful device when there is no additional aorta to cover with graft without interruption of the renal orifices. Palmaz stents, used alone or in conjunction with other devices, may improve fixation of the proximal portion of the stent and may help to straighten a tortuous proximal neck. Palmaz stents may also improve opposition between the graft and the aortic wall. However, from our experience, proximal cuffs achieved a seal in only 45% of the patients. This may be due to neck angulation leading to failure to achieve a seal at junctional points between the cuff and the existing device. Bifurcated devices may provide more stability than merely the addition of proximal cuffs and are an ideal device for revision in patients who originally had aorto-aorto tube devices. The key to successful deployment of a bifurcated device in these revision cases is to assure that there is adequate space to open the main body to allow for cannulation from the contralateral iliac artery. This may prove to be difficult in cases where a prior bifurcated or tube device has migrated distally. Aortouni-iliac devices provide several benefits over some of the other devices. In particular, the Talent aortouni-iliac device allows for transrenal fixation and relies on only a single limb of the prior repair or native artery depending on the length. Additionally, the Zenith Renu device is commercially available in an aortouni-iliac configuration and offers many of these same features. This configuration also forgoes the addition of various junction points, which will be at risk for type III endoleaks in the future. One application in particular which may benefit from an aortouni-iliac device is in cases of aneurysm enlargement without a defined endoleak. Although some have advocated that this situation may require open conversion,23 placement of an aortouni-iliac device successfully relines the entire length of the previous repair and creates new proximal and distal seal zones using endovascular techniques. In our series, use of aortouni-iliac devices allowed for successful secondary endovascular repair in 86% of cases. For select cases, a branched or fenestrated graft, when available, may be useful for endovascular revisions, particularly in the setting of a short and wide neck. In addition, other techniques, such as debranching via use of visceral bypasses in conjunction with endovascular methods, have been described.

Our perioperative complication rate was 21%; however, most were minor complications related to wound problems, most probably related to the fact that these were reoperative groins. Ten of our patients failed their secondary repair. Few reports have specifically examined endovascular revision; however, Azizzadeh et al.24 reported a series of 20 patients with proximal attachment failures requiring secondary procedures, all cuffs and Palmaz stents. In their series, only two patients required tertiary procedures. They had no major perioperative complications and did not report minor complications. The mean neck width was was 20 mm, which was larger than that reported in our series (25 mm). This could explain the higher rate of failure in our series.

For the majority of patients who fail endovascular revision, several endovascular options exist. Patients may undergo tertiary or even quaternary placement of additional devices if this is required. Patients may also undergo angioplasty of the involved area of the graft in order to obtain a better seal. Perhaps the least invasive option is coil embolization of endoleak channels or the aneurysm sac itself. This has been a successful treatment of type I endoleaks in select circumstances.25, 26 Coil embolization for some patients may be the only endovascular option if there is limited normal artery length needed for deployment of an extension device. However, in experimental models, intra-aneurysmal pressure has been transmitted through coils despite radiographic resolution of an endoleak27 and, thus, should be reserved for this select group of patients. Finally, following endovascular revision, open revision remains an option, although it may be complicated by the additional devices within the aorta.

In conclusion, failures following EVAR occur in a small but significant number of patients. When anatomically possible, endovascular revision appears to be a safe and efficacious means of treating these failures. Although this is a retrospective review, it is our current practice that aortouni-iliac devices be the preferred endograft for repair of proximal type I endoleaks and enlarging aneurysms in the absence of documented endoleak. This approach is somewhat different from our previous reported experience, which focused on cuffs, extensions, and coils as the primary method of repair of endoleaks.25 These devices appear to offer a more durable repair than a simple proximal cuff or balloon angioplasty and stenting. The midterm results of these patients indicate that they may require additional procedures but have a low rate of aneurysm-related mortality. Longer-term follow-up will be necessary to determine the durability of these endovascular revisions.

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References 

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PII: S0890-5096(07)00356-1

doi:10.1016/j.avsg.2007.10.003

Annals of Vascular Surgery
Volume 22, Issue 1 , Pages 30-36, January 2008

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