Essentials of Endovascular Abdominal Aortic

Va s c u l a r a n d I n t e r ve n t i o n a l R a d i o l o g y • R ev i ew Picel and Kansal Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair

FOCUS ON:

Downloaded from www.ajronline.org by 54.152.109.166 on 10/22/15 from IP address 54.152.109.166. Copyright ARRS. For personal use only; all rights reserved

Vascular and Interventional Radiology Review

Andrew C. Picel1 Nikhil Kansal2 Picel AC, Kansal N

Essentials of Endovascular Abdominal Aortic Aneurysm Repair Imaging: Postprocedure Surveillance and Complications OBJECTIVE. Lifelong postprocedural imaging surveillance is necessary after endovascular abdominal aortic aneurysm repair (EVAR) to assess for complications of endograft placement, as well as device failure and continued aneurysm growth. Refinement of the surveillance CT technique and development of ultrasound and MRI protocols are important to limit radiation exposure. CONCLUSION. A comprehensive understanding of EVAR surveillance is necessary to identify life-threatening complications and to aid in secondary treatment planning.

E

Keywords: abdominal aortic aneurysm, endoleak, endovascular aortic aneurysm repair, EVAR complications, imaging surveillance DOI:10.2214/AJR.13.11736 Received October 18, 2013; accepted after revision May 29, 2014. N. Kansal is a consultant for Endologix, Inc.. 1 Department of Radiology, University of California San Diego, 200 W Arbor Dr, San Diego, CA 92103-8756. Address correspondence to A. C. Picel ([email protected]). 2 Department of Vascular Surgery, St. Elizabeth’s Medical Center, Brighton, MA.

WEB This is a web exclusive article. AJR 2014; 203:W358–W372 0361–803X/14/2034–W358 © American Roentgen Ray Society

W358

ndovascular abdominal aortic aneurysm repair (EVAR) consists of placing a stent-graft within the aorta to exclude the aneurysm from arterial circulation and reduce the risk of rupture. The procedure may be performed with surgical groin exposure or by a totally percutaneous technique using vascular closure devices. Detailed preprocedural anatomic evaluation is necessary to properly plan the EVAR procedure and reduce the risk of endograft failure and secondary complications. Postprocedural surveillance is performed to evaluate for complications that may lead to aneurysm rupture and to help plan secondary treatments. Complications after EVAR can be life threatening and necessitate prompt diagnosis and intervention. Overall complication rates are as high as 30%, and the rate of late complication requiring intervention is 2–3% [1, 2]. Effective surveillance should monitor for persistent aneurysm growth, new aneurysm formation, endoleak, device migration and kinking, graft thrombosis, infection, and access site complications. Patients who undergo EVAR often have complex disease, and surveillance must be effective in the presence of associated vascular pathology, such as dense aortic calcification, arterial stenosis, occlusions, and dissection. Lifelong imaging surveillance is necessary to detect complications, which are often asymptomatic. Early detection allows the potential to intervene and prevent aneurysm growth and rupture. Complications may pres-

ent immediately after endograft placement or may result from hemodynamic stress incurred on the device over time. Proper surveillance relies on appropriate imaging protocols and interpretation. The initial procedure, secondary procedures that may be necessary to address complications, and surveillance scans expose patients to a significant radiation dose. Cumulative radiation risk is a concern as techniques and devices advance and patients live longer after treatment. This article reviews post-EVAR surveillance imaging modalities and complications that must be recognized and appropriately reported by the interpreting physician. Posttreatment Surveillance CT angiography (CTA) is the current reference standard for surveillance and is the primary imaging modality at most centers. CTA provides a sensitive evaluation for many important complications, and patients will commonly undergo numerous surveillance scans during their lifetime. However, CT may not be the ideal modality for surveillance primarily because of high accumulative radiation doses and the risk of contrast-induced nephropathy. Several studies show the benefits of alternative ultrasound and MRI surveillance protocols. Each imaging modality has advantages and disadvantages that should be considered when developing a surveillance program. CT CTA effectively detects migration, kinking, structural failure, endoleak, infection, and aneurysm growth [3]. Surveillance CTA

AJR:203, October 2014


Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair traditionally includes unenhanced, arterial phase (30-second delay), and delayed phase (120- to 300-second delay) sequences. Unenhanced images are used to differentiate hyperdense calcifications from an endoleak that may appear on the arterial or delayed phase. The delayed phase is important to assess for a low-flow endoleak that may not be apparent on the earlier arterial phase images. A study using a dynamic CT technique with multiple early scan phases [4] found that the highest rate of endoleak detection occurred 27 seconds after reaching the preset bolustracking threshold. This finding suggests that the ideal timing for endoleak detection occurs at a time point between standard arterial phase and venous phase images [4]. CTA is more sensitive than conventional angiography for detecting endoleak. However, angiography better determines the directionality of blood flow and more accurately classifies the type of endoleak. Blood flowing out of the lumbar arteries or the inferior mesenteric artery (IMA) suggests a type I or type III endoleak. Inflow of blood through these vessels is consistent with a type II endoleak. The timing at which contrast appears in the aneurysm sac is also important for classification. A type I endoleak will be manifest as early contrast opacification along the stent-graft attachment sites, whereas a type II endoleak will appear on more delayed images [5–7]. For each surveillance study, CT size measurements should be precisely compared with prior measurements. A standardized measurement protocol helps limit interobserver variability. Measurements should be obtained in a plane perpendicular to the aneurysm centerline with fine calipers using the outer aneurysm wall as the boundary (adventitia-to-adventitia) [8]. Advanced reconstruction techniques should be used to ensure accurate measurements, including 2D multiplanar reformations, curved planar reformations created on lumen centerline, and 3D reconstructions. In tortuous vessels, in the absence of multiplanar reformatted images, measuring greatest diameters may be inaccurate. However, if compared with similar measurements on prior studies, interval change can be appropriately assessed. CT also provides the ability to calculate the aneurysm sac volume. Studies suggest that changes in aneurysm diameter and volume may be discordant with calculated volumes providing a more accurate assessment

of aneurysm growth [6, 9, 10]. Volume calculations commonly require manual segmentation on a dedicated workstation, with postprocessing taking up to 45 minutes. A 2% volume increase is proposed as a threshold to identify endoleaks after EVAR [9]. Calculating volumes is more time consuming than simple diameter measurements and does not allow coregistration of interval studies. As automated reconstruction software is developed, CT volumetry will become less time consuming and more practical for clinical use. Contrast-induced nephropathy, cumulative radiation exposure, and cost are concerns in lifelong CTA surveillance. Traditional surveillance protocols consist of a baseline CT at 1 month after repair, followed by 6-month interval scans with a transition to yearly studies in the absence of complications. Early aneurysm sac shrinkage may be associated with fewer late complications after EVAR [11]. Therefore, it may be feasible to lengthen the interval to 1 year when the aneurysm sac is smaller than 5 cm or has decreased by 5 mm. When the sac size decreases to 4 cm, CT may then be obtained every 2–3 years [12]. Studies also suggest that the surveillance interval can be lengthened in the absence of complications on the 1-month posttreatment scan, and the 6-month follow-up scan may be eliminated without adverse outcomes [13, 14]. Adjusting the CT scan technique can also reduce the radiation exposure. A triphasic CT scan may not be necessary for routine surveillance. It is possible that the unenhanced scan is needed on only the first surveillance examination and may be omitted thereafter in the absence of complications. Routine delayed images may also be unnecessary, although a low-flow endoleak could be missed on the arterial phase study [15]. Others propose that eliminating the arterial phase would lead to reduced radiation exposure and still allow the detection of an endoleak on delayed images [16]. In addition, a comparison of aortic volumes calculated from contrast-enhanced and unenhanced sequences found no difference in volume measurements, with a significant reduction in radiation exposure [17, 18]. This implies that unenhanced CT with volume analysis may be sufficient for follow-up in patients with contraindications to IV contrast agent administration or to limit the radiation exposure from multiple series. A change in the aneurysm sac volume would prompt an immediate contrast-enhanced study to evaluate for endoleak [19].

Several radiation dose–reduction tools are available on modern CT scanners and should be used for surveillance scans. Automatic exposure control adjusts the radiation dose according to patient size and tissue attenuation. Automatic exposure control modulation software can reduce the dose by up to 40– 50% [20]. Iterative reconstruction loops can be used to reduce image noise and improve resolution, which results in the production of diagnostic-quality studies at a significantly lower dose [21]. Dual-energy CT allows simultaneous acquisition of CT data with two different photon energy levels. Using this method, iodine can be subtracted and virtual unenhanced images can be created. Dualphase dual-energy CT can reduce the radiation dose 19.5% compared with a standard triphasic CT examination [22]. Additional proposals to reduce radiation exposure include performing primary surveillance with ultrasound and radiography [18]. CTA would then be obtained to further examine a positive finding, such as expansion of the aneurysm sac [6, 23]. Some authors suggest that, in asymptomatic patients, it may be sufficient to abandon CT after 1 year of surveillance and follow diameter measurements and structural stability with ultrasound and abdominal radiographs [24]. Radiography Anteroposterior and lateral radiographs are often obtained with CTA to provide a global assessment of stent-graft position and integrity [23] (Fig. 1). Device migration, wire frame fracture, and kinking may be identified. Radiographs should be consistently centered to reduce geometric distortion. The position of the stent-graft relative to anatomic landmarks is compared on serial radiographs. Oblique projections are acquired to improve the detection of wire frame fractures [6]. Radiographs should be obtained before the CTA examination to avoid contrast material in the urinary collecting system obscuring the endograft framework. Ultrasound and MRI provide a limited evaluation of stent-graft integrity, and concurrent radiographs are required for complete evaluation. The importance of accurately describing the stent-graft appearance and position on radiographs may increase as radiation-sparing ultrasound and MRI protocols are developed and become more common in clinical practice. Radiographs do not provide an assessment of aneurysm sac size and are not useful as a standalone screening modality.

AJR:203, October 2014 W359


Picel and Kansal Ultrasound Imaging Duplex ultrasound can be technically demanding in obese patients, as well as those with extensive arterial wall calcifications, but in many cases it can accurately reveal the proximal and distal fixation sites and determine the aneurysm sac size [12] (Fig. 2). Ultrasound measurements appear to be comparable to those obtained by CTA [25–27]. In certain cases, ultrasound dimensions may be more accurate because of overestimation on axial CT measurements. It is likely that ultrasound diameters are equivalent to those measured on reconstructed CT centerline of flow images [28]. A high degree of interobserver and intraobserver variability in diameter measurements suggests that ultrasound and CT should not be used interchangeably, but consistent use of an ultrasound or CT protocol should be adopted for surveillance [28]. Color Doppler and spectral waveforms provide useful hemodynamic information. Endoleaks appear as pulsatile color-flow within or adjacent to the aneurysm sac. Bidirectional flow and lower peak systolic velocities are associated with spontaneous endoleak closure [5, 29, 30]. A recent study suggests that 3D ultrasound can provide volume estimation of the aortic sac with high technical success. Although 3D ultrasound is not currently used clinically, it may provide a sensitive measure of aneurysm growth, similar to volumetric CTA [31, 32]. Ultrasound is limited in revealing kinking and migration of the stent-graft, and we suggest obtaining concurrent radiographs for surveillance. Contrast-enhancement increases the sensitivity of ultrasound surveillance [33]. Several reports agree that contrast-enhanced ultrasound (CEUS) is at least as sensitive as CT for detecting endoleak, and there are instances of CEUS identifying endoleaks not seen on CT [34–37]. This may be because CEUS allows a dynamic scan time of several minutes compared with static CT images. It is possible that CEUS will detect endoleaks in cases of endotension that are not explained by CT. CEUS also provides improved endoleak classification because of the dynamic visualization of the direction of blood flow into the aneurysm sac [38, 39]. In addition, a recent study described a 3D CEUS technique that more effectively visualizes endoleak inflow vessels and may be more sensitive in detecting endoleak than 2D CEUS or CTA [40]. No major adverse effects have been found with ultrasound contrast agents [33]. Ultrasound-only surveillance protocols are under development, with some groups starting

W360

as early as 6 months after intervention. Others initiate ultrasound surveillance depending on sac shrinkage at 1 year. Any suspicious ultrasound finding is then evaluated with CTA [34]. Studies suggest that ultrasound can provide surveillance comparable to CT and is sufficient to identify complications requiring intervention. However, 1- and 12-month postprocedural CT examinations may remain necessary to evaluate stent-graft position, integrity, aneurysm morphologic features, and visceral vessel patency, which are not well evaluated by ultrasound [39]. Selective CTA would be performed in cases with endoleak detected on ultrasound, abdominal aortic aneurysm diameter increase, migration on radiograph, or poor visibility of the stent-graft on ultrasound examination [27]. If ultrasound-predominant surveillance is widely accepted, it promises to significantly reduce radiation exposure and cost [41, 42]. MRI MR angiography (MRA) can detect luminal patency, device positioning, and residual sac flow. Nitinol stents are best suited for MRA, whereas stainless steel and cobalt-chromium-nickel alloy stents are ferromagnetic and may result in significant artifact [5]. Several reports suggest that MRA is more sensitive than CTA in endoleak detection [6, 7, 43–45]. In cases of endotension, the aneurysm sac increases in size without an appreciable endoleak on imaging. MRI should be considered in these cases because it is especially effective in identifying type II endoleaks that may otherwise be undetected and classified as endotension [45]. A typical MRA protocol consists of axial T1-weighted echo-gradient images and contrast-enhanced MRA with arterial and late phase imaging. Late phase T1-weighted gadolinium-enhanced sequences are recommended for detecting endoleak [7]. Time-resolved MRA and flow analysis show the evolution of contrast material in the aneurysm sac and may help classify the type of e ndoleak [6]. However, these sequences have inferior spatial resolution and are more sensitive to susceptibility artifacts than T1-weighted contrast-enhanced images [45]. Blood-pool MRI contrast agents have prolonged intravascular retention and have the potential to detect endoleaks with slow flow rates that may be occult on CT. MRI results in multiplanar images with 3D reconstructions similar to CT but is limited by imaging artifacts from ferromagnetic stents and coil material, relatively

high cost, and long examination times. MRI is ineffective in evaluating stent-graft integrity, and concurrent radiographs should be obtained for complete evaluation. MRA avoids exposure to ionizing radiation and iodinated contrast material but is associated with a potential for nephrogenic systemic fibrosis resulting from exposure to gadolinium-based contrast material. Unenhanced MRI sequences provide an effective alternative to avoid the risk of contrast material administration in patients with renal failure. One study suggests that a balanced morphologic true fast imaging with steady-state precession (true-FISP) sequence is effective in imaging the aorta and its main branches and allows a sensitive evaluation for endoleak with a high negative predictive value [46]. Superparamagnetic iron oxide particle–enhanced dynamic MRI may provide another useful imaging alternative in patients with renal insufficiency, with a recent small study showing excellent sensitivity for type II endoleak [47]. Pressure Measurement An investigational approach to surveillance consists of monitoring the pressure within the aneurysm sac to predict negative outcomes. Pressure sensors implanted during endograft placement measure local pressures adjacent to the stent-graft limbs. Low pressure may indicate a shrinking aneurysm sac, and pulsatile high pressure suggests an enlarging aneurysm with possible e ndoleak [3, 48]. Remote pressure measurements have the potential to reduce or replace surveillance imaging, but further investigation is warranted before the devices are widely used. This technique does not evaluate stentgraft integrity and would not likely provide a stand-alone screening modality. Conclusion Lifelong imaging surveillance is mandatory to detect complications that may lead to aneurysm sac pressurization and rupture. CTA is the current reference standard for surveillance, but because of concerns of cumulative radiation exposure, several centers are investigating alternative imaging protocols. These protocols may consist of reduceddose CT techniques or surveillance protocols based primarily on ultrasound or MRI. We currently perform a 1- to 2-month postoperative triple-phase CTA to evaluate for early complications and endograft positioning. This is followed by a repeat CTA in 6 months. If no complications are detected and



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair the aneurysm sac size is stable or decreased, then yearly surveillance is performed. Uncomplicated cases are transitioned to yearly duplex ultrasound surveillance to follow the aneurysm sac size and evaluate for endoleak. Complications are typically followed with 6-month CT scans or go to catheter angiography for diagnosis and treatment. Posttreatment Complications Several complications detected on surveillance imaging result in pressurization of the aneurysm sac and increase the risk of rupture. Because of postprocedural complications, repeat interventions are necessary in 12–35% of cases [49, 50]. Most of these interventions are performed with endovascular techniques and require minimal additional hospitalization [49, 51]. The following complications detected on surveillance imaging may lead to repeat intervention and must be accurately recognized and described by the interpreting physician. Endoleak An endoleak results in blood flow outside the stent-graft but within the aneurysm sac. Endoleaks occur in 15–25% of patients within the first 30 days after EVAR and are often asymptomatic [5, 52]. Lifelong imaging surveillance is required for detection. Endoleaks are classified according to the origin of blood flow (Table 1). Although CTA is superior for the detection of endoleak, catheter angiography better reveals the dynamics of blood flow critical for endoleak classification [53]. A type I endoleak results when blood enters the aneurysm sac from an attachment site and occurs after approximately 10% of EVAR procedures [54] (Fig. 3). There is direct communication with the arterial circulation, resulting in an increased risk of rupture. Landing zone characteristics that are beyond the device-specific instructions for use, such as a large, angulated, tapered, or calcified proximal neck, increase the risk of endoleak [6, 52, 55]. It is traditionally thought that extensive thrombus results in a poor proximal seal and leads to a type I endoleak. However, recent reports suggest that neck thrombus may not lead to adverse outcomes in early and midterm results [56, 57]. CTA suggests the presence of a type I endoleak when contrast material within the aneurysm sac appears closely apposed to the proximal or distal attachment sites. Type I endoleaks are subdivided as type Ia when the leak originates from the proximal attachment site and as type Ib from the distal attachment

TABLE 1: Endoleak Classification Type of Endoleak

Source of Blood Flow

Type I

Stent-graft attachment sites

Type II

Inflow from collateral vessels

Type III

Structural stent-graft failure

Type IV

Endograft material porosity

Type V

Endotension

site. Type Ic is a rare situation, with backfilling of the aneurysm sac resulting from failed embolization of the contralateral common iliac artery when an aortouniiliac device is placed in conjunction with a femoral-femoral bypass [5]. Type I endoleaks can appear in the immediate perioperative period or can present in a delayed fashion. Remodeling may result in mechanical or hemodynamic change, aortic neck dilation, iliac artery dilation, or increased iliac artery angulation that results in a delayed attachment site leak [58]. An adequate proximal seal is necessary to reduce the risk of type I endoleak. Stentgrafts were developed with hooks and barbs to help reduce migration and proximal endoleak. Oversizing the endograft by 15–20% also helps achieve an adequate seal [52]. In cases of type I endoleak, early intervention is necessary to reduce the risk of rupture. Treatment typically consists of securing the attachment sites with angioplasty balloons, stents, or endograft extensions [52, 59]. Treatment with coil embolization and glue has been successful in select cases. If the neck has expanded, placement of a fenestrated graft or chimney grafts may prevent surgical conversion [60]. Advanced EVAR techniques, such as chimney or snorkel graft placement, require vigilant postprocedural surveillance. Variations of this technique may be used when the main endograft device is positioned or extended in such a manner to cover and preclude flow to the renal arteries, celiac artery, superior mesenteric artery (SMA), or internal iliac arteries. In these cases, additional stents are placed parallel to the main stentgraft device. These additional stents extend beyond the sealing zone of the main endograft and provide a conduit to preserve flow to the otherwise covered aortic branches (Fig. 4). If the aorta is highly calcified, the chimney stents may not conform tightly to the aortic wall and result in a persistent type I endoleak that may require treatment. However, type I endoleaks seen in the early postprocedural period may represent low flow in

the gutter formed around the chimney graft, and many resolve spontaneously. For the renal arteries, a literature review revealed type I endoleaks in 7% of cases after placement of a single chimney graft and in 15.6% of patients receiving two grafts [61]. A type II endoleak is the most common type, occurring after 10–25% of cases [54]. This type of endoleak results from retrograde flow into the aneurysm sac from collateral vasculature, often the IMA or lumbar arteries (Fig. 5). Type II endoleaks are classified as type IIa when there is a single feeding vessel and as type IIb when there are multiple contributing vessels [5]. CT contrast agent found in an anterior location within the aneurysm sac suggests that the leak is from the IMA, and contrast agent in a posterolateral location is assumed to be from the lumbar arteries. One study suggests that a larger cross-sectional aortic diameter at the IMA ostium and a greater number of patent aortic side branches is associated with a higher incidence of type II endoleak [62]. Pre-EVAR coil embolization of the IMA may reduce the incidence of type II endoleak and aneurysm sac enlargement [63–66]. However, aortic side branch occlusion, particularly involving the lumbar arteries, is time consuming, often incomplete, and not routinely performed [67, 68]. The number of patent collateral vessels and the thickness and total circumference of mural thrombus correlate with the risk of developing a type II endoleak and aneurysm growth [59, 69–71]. Although it is suggested that lysis of thrombus within the aneurysm sac at the origin of collateral vessels may lead to a delayed type II endoleak, some studies also show a protective effect from thick circumferential thrombus. The thickness and percentage circumference of aortic thrombus, particularly at lumbar artery and IMA ostia, may be inversely related to the formation of persistent type II endoleaks [72]. Up to 40% of type II endoleaks spontaneously thrombose and immediate intervention is not always required [52]. Delayed type II endoleaks appear more than 1 year



Picel and Kansal after EVAR and are often associated with increasing aneurysm size [73]. Treatment is often initiated because of the potential for increased sac pressure and rupture [74]. Although criteria are not evidence based, 5–10 mm of aneurysm sac expansion is often used as a threshold for intervention. However, there are reported cases of rupture without sac expansion, suggesting that a more aggressive approach to type II endoleak treatment may be warranted [75]. Endovascular treatment consists of embolization by a transarterial approach or direct translumbar puncture. The transarterial approach consists of navigating microcatheters into the feeding or draining arteries and placing metallic coils to prevent retrograde flow. The IMA is catheterized through Riolan arcades from the SMA, and lumbar arteries are accessed through iliolumbar artery collaterals. The recurrence rate is high because of the dynamic nature of multiple contributing vessels, similar to a vascular malformation [76]. After embolization, inflow tends to shift to other collateral vessels and the endoleak may persist. During treatment, occluding the inflow and outflow vessels reduces the risk of recanalization, and shortterm occlusion can be achieved if the embolic material reaches the aneurysm sac [52]. The translumbar approach is typically more effective than transarterial embolization, which tends to require multiple interventions [76, 77]. In the translumbar approach, the aneurysm sac is directly punctured under fluoroscopic or CT guidance for placement of coils and glue into the endoleak cavity and feeding vessels, if identified. By treating the endoleak cavity with embolization of the aneurysm sac itself, this technique is similar to treating the nidus of an arteriovenous malformation and eliminates the communication between aortic side-branches. It is suggested that transarterial embolization with microcatheter selection and embolization of the endoleak cavity, in addition to the feeding artery, has similar efficacy to translumbar embolization [78]. Secondary interventions for type II endoleak are associated with high failure rates, and multiple treatments may be required, often necessitating a combination of transarterial and translumbar approaches [77] (Fig. 6). Ethylene vinyl alcohol copolymer (Onyx, ev3) used as a secondary intervention for persistent type II endoleak is more successful than coil embolization alone [79]. Onyx is nonadhesive, which allows a slower precise delivery. It shows predictable behavior

W362

and is easily seen under fluoroscopy. One group achieved 73% success using Onyx as a transarterial embolic agent with improved results when Onyx reached the endoleak cavity [80]. Onyx may be used in combination with coils and plugs, which may protect from nontarget embolization and reduce the volume of liquid embolic required [81]. Surveillance after endoleak treatment is complicated by beam-hardening artifact from coils and glue used as embolic material. The tantalum component of Onyx improves visibility under fluoroscopy but results in CT streak artifact. This artifact may obscure fine detail, but measurement of aneurysm sac size to assess interval growth is often possible [82]. It is important to obtain an unenhanced CT series to differentiate high-density embolic material from enhancement that may be identified on the contrast-enhanced series and indicate the presence of a persistent or new endoleak. A type III endoleak results from a structural stent-graft failure or disconnection between components, with an estimated incidence of 4% after 1 year [52]. CTA reveals contrast material adjacent to the endograft but often not in the aneurysm sac periphery, as seen with a type II endoleak. Arterial pulsation and sac shrinkage may distort the device or lead to migration and result in a type III endoleak [6] (Fig. 7). A tear in the graft material is classified as type IIIa. Type IIIb is a junctional gap between modular components, and type IIIc refers to other causes of device failure, such as suture breakage [6]. Repair is emergent because of rapid arterial pressurization of the aneurysm sac and the potential for rupture. Endovascular repair often consists of placement of a stent-graft extension or cuff to cover the site of leakage. Type IV endoleaks result from porosity in the graft material and are seen on angiography immediately after placement. They usually resolve when coagulation is normalized. Type IV endoleaks were seen primarily during placement of early-generation devices and are typically of no clinical consequence [5]. With production advances in the newgeneration devices, this type of endoleak is now uncommonly seen [52]. A type V endoleak, also referred to as endotension, occurs when there is enlargement of the aneurysm sac without a detectable leak on imaging [5]. This may be due to ultrafiltration of blood across the stent-graft, with thrombus providing an ineffective barrier to pressure transmission, infection, seroma, or failure to detect the leak on imaging [6, 52]. A type V endoleak is a diagnosis of

exclusion. Imaging with additional modalities, such as ultrasound and MRA, should be attempted to exclude an alternate type of endoleak that was not detected on the initial surveillance study. Intervention, including conversion to open repair, may be necessary in the presence of increasing aneurysm size. Migration Surveillance imaging should be evaluated for migration and compared with prior images; 5–10 mm of migration is generally considered significant [6]. Landmarks, such as the SMA and renal arteries, can be used to measure migration and provide a standard for comparison. The risk of migration depends on the type of device, neck diameter and configuration, and length of the landing zones [83]. The degree of stent-graft oversizing may also contribute to migration, with greater than 30% oversizing resulting in an inadequate proximal seal [84]. Neck enlargement or other changes in aneurysm morphologic features over time may lead to migration, whereas suprarenal fixation is associated with a lower rate of migration [85]. Migration can result in endoleak, limb occlusion, and rupture. Extension cuffs are often placed for treatment. Long-term results are expected to yield lower rates of migration with new-generation devices. Limb Kinking or Thrombosis Stent-graft kinking may result from migration or decreasing aneurysm sac diameter and length. Kinking can lead to migration, thrombosis, and type I or III endoleak. Excessive aortic neck angulation and a narrow distal aortic diameter predispose to kink formation [86]. The reported incidence varies depending on the degree of kinking but is in the range of 1.7–3.7% [52, 86]. It is possible that new lowprofile devices will have higher rates of limb kinking and occlusion because of less radial force and columnar stent strength [87]. Additional high-radial-force uncovered stents may be placed in an attempt to straighten kinks and avoid thrombosis. Limb occlusion is often related to kinking of the metallic skeleton, extension of the stentgraft into tortuous or diminutive iliac arteries, or migration and dislocation of an endograft limb [88]. Excessive oversizing, resulting in folding of the graft material, and twisting of the limbs during deployment are two possible causes of thrombosis [58, 89]. The incidence of thrombosis is reported to be 0.5–11% [52]. In cases of diminutive iliac arteries, it may be



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair necessary to place an aortouniiliac graft with a surgical bypass to avoid thrombosis. Thrombectomy and stent placement may be attempted to salvage a thrombosed limb. Otherwise, a femoral-to-femoral artery bypass may be required to revascularize the limb supplied by the thrombosed segment (Fig. 8). In cases with an aneurysmal common iliac artery, snorkel stents or bifurcated iliac side branch devices may be used to preserve flow to the internal iliac artery. Surveillance imaging should carefully evaluate these devices for limb thrombosis, which may result in buttock claudication, especially when both internal iliac arteries are occluded. Infection Endograft infection is associated with high mortality but is relatively uncommon, occurring in less than 1% of cases [90, 91]. Procedural contamination is the most likely cause of early infection. Although the stent-graft is protected by the intact aneurysm sac, remote sites of infection may lead to late colonization. Infection presents as leukocytosis, fever, and back pain. CT shows mesenteric inflammation adjacent to the stent-graft, perigraft fluid collections, abnormal enhancement, or air bubbles (Fig. 9). An aortoenteric fistula is a rare complication after EVAR that may lead to massive hemorrhage, endograft infection, and hypovolemic shock [92] (Fig. 10). Endoleaks resulting in aneurysm expansion may lead to erosion and aortoenteric fistula formation [93]. Endograft infection and placement in inflammatory aneurysms are other commonly proposed causes for fistula formation [94]. Treatment may consist of in situ repair with resection of the infected graft and placement of antibiotic-soaked polyester graft, autologous vein graft, or cryopreserved graft. Extraanatomic reconstruction is often performed in high-risk cases. Patients will first receive IV antibiotics and then be converted to an oral suppressive antibiotic regimen. The optimal duration of antibiotic therapy is not yet determined but may be lifelong in complicated cases [91]. Renal Complications EVAR requires a minimum of 50–100 mL of iodized IV contrast material. The lowest possible dose of 50%/50% diluted isoosmolar contrast material should be used in patients with renal insufficiency. Renal function declines after EVAR, with renal failure estimated to occur in 6.7% of cases [95]. A recent study suggests that patients who undergo EVAR have a greater continuous decline in re-

nal function over time compared with patients who undergo open aneurysm repair. This is likely due to contrast agent given during the initial procedure, secondary procedures to treat complications, and routine surveillance scans. Alternative unenhanced surveillance protocols should lessen the long-term risk of renal function impairment [96]. End-organ ischemia attributed to clot formation or embolic phenomena related to catheter manipulation in heavily diseased vessels may also result in ischemia and deteriorating renal function. Patients should be well hydrated before and after the procedure. Pretreatment with sodium bicarbonate reduces contrast-induced nephrotoxicity, and acetylcysteine is also frequently given despite limited evidence of its efficacy. Intravenous ultrasound can be used to evaluate the anatomy before treatment and assess the endograft after placement [97]. Using intravenous ultrasound can significantly reduce the amount of IV contrast material administered during stent-graft placement [98]. Renal artery stenting may be performed before EVAR in patients with renal artery stenosis and marginal renal function. Stents placed in the proximal renal arteries extend a short distance into the aortic lumen and are flared to minimize kinking or fracture by the stent-graft [52]. If renal artery occlusion results from poor aortic endograft placement, attempts may be made to pull the device inferiorly and uncover the renal arteries. Patients with complicated proximal neck anatomy may require suprarenal placement of the endograft and restricted blood flow to the kidneys. Chimney grafts or fenestrated grafts may be placed in these situations [99]. Despite the administration of IV contrast material, EVAR is associated with improved short-term postoperative renal function compared with open repair [100]. Bowel Ischemia Bowel ischemia is a serious but rare complication after EVAR. Thrombotic deposits and atheroma in the suprarenal aorta may be dislodged during endograft placement and travel to the SMA, IMA, internal iliac arteries, and lower extremities. When involving the mesenteric circulation, microemboli may result in multifocal patchy bowel ischemia. Inadequate mesenteric collateral circulation is another proposed cause [52, 101]. Colonic ischemia is a strong independent predictor of postprocedural mortality. The incidence of colonic ischemia in EVAR is predicted to be lower than that of open repair, during which it occurs in 1–6% of cases [92, 102].

Device Failure Structural endograft failure is a rare complication that was more common with early-generation devices [103]. It results from fatigue, corrosion, suture breakage, or graft fabric tear. Structural failures may occur in up to 5.5% of cases and result in ineffective attachment zone seal, migration, and endoleak [58]. Turbulent flow in the aneurysm sac due to an endoleak can contribute to early device fatigue and eventual failure [6]. It is possible that more device failures will be found as patients and devices age. A recent study found that metallic ring failure and suture breakage detected on 3D CTA correlate with the development of migration and type I and type III endoleaks, thus supporting the concept that fatigue degradation leads to delayed endoleaks [104]. Structural failures are often late occurrences, and vigilant long-term surveillance should be maintained for these complications [103]. Access Site Complications EVAR is now commonly performed with a totally percutaneous technique using arterial closure devices. Percutaneous EVAR is possible in 76–96% of patients with success rates depending on patient selection [105]. Percutaneous EVAR decreases the rate of wound complications, operative time, and length of hospital stay when compared with traditional open femoral access [105, 106]. Obesity, repeat groin access, larger sheath size, severe femoral artery calcification, access vessel size less than 5 mm, and lack of operator experience are associated with percutaneous EVAR failure and conversion to open femoral access [105, 107, 108]. A study suggests that femoral artery calcification involving greater than 50% of the anterior vessel wall increases the risk of closure device failure [106]. Ultrasound guidance allows proper puncture in the common femoral artery and enables the operator to avoid areas with large anterior calcifications. Access site complications occur in up to 3% of percutaneous EVAR procedures [92]. Several potential complications include arterial thrombosis, dissection, pseudoaneurysm formation, and local wound complications. The large delivery system and sheath size can result in dissection and avulsion of the access arteries. Arterial dissection may be repaired with stenting if it is discovered during the procedure. Vessel rupture may occur when entering small or heavily calcified vessels and may not become apparent until the vascular sheath is removed at the end of the procedure.



Picel and Kansal Angioplasty can be attempted to allow access through severely stenotic vessels. A surgically placed retroperitoneal iliac artery conduit provides another option for access in patients with small, tortuous, or heavily calcified iliofemoral vessels [92]. A 10-mm polyester fiber (Dacron, DuPont) graft is commonly used for the conduit, which is placed to provide large-vessel access. The conduit is often attached to the common iliac artery near the terminal bifurcation [107]. Distal placement is necessary to preserve the landing zone for the endograft device. At the end of the procedure, the conduit may be ligated near its origin or closed and left in place for future access. Abdominal Aortic Aneurysm Rupture Delayed abdominal aortic aneurysm rupture after EVAR is rare, reported to occur in 0.5% of cases per year [59]. Treatment consists of endovascular revision or open surgical conversion. Ruptures may occur in patients without evidence of increasing aneurysm size on surveillance. This is likely due to sudden pressurization of the aneurysm sac from a type I or III endoleak [59]. Mortality rates are significantly higher for secondary procedures performed after abdominal aortic aneurysm rupture. Detailed imaging evaluation to determine the cause of the endograft failure assists in surgical planning for either endovascular or open repair [50]. Endovascular therapy to treat the underlying failure will likely involve graft extensions within the proximal or distal landing zones or within the stent-graft components to adequately seal the rupture. Conclusion EVAR depends on imaging for preprocedural treatment planning and detection of postprocedural complications. As devices continue to advance, more patients will become amenable to endovascular repair. Refinement in the surveillance CT technique and the development of ultrasound and MRI protocols are important to limit radiation and contrast material exposure. Proper EVAR surveillance requires close collaboration between imagers and interventionalists to ensure that appropriate and safe screening is performed and for prompt notification when urgent intervention is required. A comprehensive understanding of EVAR surveillance and associated complications is necessary for the interpreting physician to create a detailed and clinically useful imaging report and assist in the care of these complex patients.

W364

References 1. d’Audiffret A, Desgranges P, Kobeiter DH, Becquemin JP. Follow-up evaluation of endoluminally treated abdominal aortic aneurysms with duplex ultrasonography: validation with computed tomography. J Vasc Surg 2001; 33:42–50 2. Kranokpiraksa P, Kaufman JA. Follow-up of endovascular aneurysm repair: plain radiography, ultrasound, CT/CT angiography, MR imaging/MR angiography, or what? J Vasc Interv Radiol 2008; 19:S27–S36 3. van der Vliet JA, Kool LJ, van Hoek F. Simplifying post-EVAR surveillance. Eur J Vasc Endovasc Surg 2011; 42:193–194 4. Lehmkuhl L, Andres C, Lucke C, et al. Dynamic CT angiography after abdominal aortic endovascular aneurysm repair: influence of enhancement patterns and optimal bolus timing on endoleak detection. Radiology 2013; 268:890–899 5. Shah A, Stavropoulos SW. Imaging surveillance following endovascular aneurysm repair. Semin Intervent Radiol 2009; 26:10–16 6. Stavropoulos SW, Charagundla SR. Imaging techniques for detection and management of endoleaks after endovascular aortic aneurysm repair. Radiology 2007; 243:641–655 7. Alerci M, Oberson M, Fogliata A, Gallino A, Vock P, Wyttenbach R. Prospective, intraindividual comparison of MRI versus MDCT for endoleak detection after endovascular repair of abdominal aortic aneurysms. Eur Radiol 2009; 19:1223–1231 8. Cayne NS, Veith FJ, Lipsitz EC, et al. Variability of maximal aortic aneurysm diameter measurements on CT scan: significance and methods to minimize. J Vasc Surg 2004; 39:811–815 9. Kauffmann C, Tang A, Therasse E, et al. Measurements and detection of abdominal aortic aneurysm growth: accuracy and reproducibility of a segmentation software. Eur J Radiol 2012; 81:1688–1694 10. Wever JJ, Blankensteijn JD, Th M Mali WP, Eikelboom BC. Maximal aneurysm diameter follow-up is inadequate after endovascular abdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg 2000; 20:177–182 11. Bastos Gonçalves F, Baderkhan H, Verhagen HJ, et al. Early sac shrinkage predicts a low risk of late complications after endovascular aortic aneurysm repair. Br J Surg 2014; 101:802–810 12. Back MR. Surveillance after endovascular abdominal aortic aneurysm repair. Perspect Vasc Surg Endovasc Ther 2007; 19:395–400 13. Go MR, Barbato JE, Rhee RY, Makaroun MS. What is the clinical utility of a 6-month computed tomography in the follow-up of endovascular aneurysm repair patients? J Vasc Surg 2008; 47:1181–1187 14. Kirkpatrick VE, Wilson DE, Williams RA, Gordon IL. Surveillance computed tomographic arteriogram (CTA) does not change management before

three years in patients who have a normal postEVAR study. Ann Vasc Surg 2014; 28:831–836 15. Iezzi R, Cotroneo AR, Filippone A, et al. Multidetector CT in abdominal aortic aneurysm treated with endovascular repair: are unenhanced and delayed phase enhanced images effective for endoleak detection? Radiology 2006; 241:915–921 16. Macari M, Chandarana H, Schmidt B, Lee J, Lamparello P, Babb J. Abdominal aortic aneurysm: can the arterial phase at CT evaluation after endovascular repair be eliminated to reduce radiation dose? Radiology 2006; 241:908–914 17. Nambi P, Sengupta R, Krajcer Z, Muthupillai R, Strickman N, Cheong BY. Non-contrast computed tomography is comparable to contrast-enhanced computed tomography for aortic volume analysis after endovascular abdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg 2011; 41:460–466 18. Bley TA, Chase PJ, Reeder SB, et al. Endovascular abdominal aortic aneurysm repair: nonenhanced volumetric CT for follow-up. Radiology 2009; 253:253–262 19. Bobadilla JL, Suwanabol PA, Reeder SB, Pozniak MA, Bley TA, Tefera G. Clinical implications of non-contrast-enhanced computed tomography for follow-up after endovascular abdominal aortic aneurysm repair. Ann Vasc Surg 2013; 27:1042–1048 20. Raman SP, Johnson PT, Deshmukh S, Mahesh M, Grant KL, Fishman EK. CT dose reduction applications: available tools on the latest generation of CT scanners. J Am Coll Radiol 2013; 10:37–41 21. Willemink MJ, Leiner T, de Johg PA, et al. Iterative reconstruction techniques for computed tomography. Part 2. Initial results in dose reduction and image quality. Eur Radiol 2013; 23:1632–1642 22. Flors L, Leiva-Salinas C, Norton PT, Patrie JT, Hagspiel KD. Endoleak detection after endovascular repair of thoracic aortic aneurysm using dualsource dual-energy CT: suitable scanning protocols and potential radiation dose reduction. AJR 2013; 200:451–460 23. Harrison GJ, Oshin OA, Vallabhaneni SR, Brennan JA, Fisher RK, McWilliams RG. Surveillance after EVAR based on duplex ultrasound and abdominal radiography. Eur J Vasc Endovasc Surg 2011; 42:187–192 24. Dias NV, Riva L, Ivancev K, Resch T, Sonesson B, Malina M. Is there a benefit of frequent CT followup after EVAR? Eur J Vasc Endovasc Surg 2009; 37:425–430 25. Wolf YG, Johnson BL, Hill BB, Rubin GD, Fogarty TJ, Zarins CK. Duplex ultrasound scanning versus computed tomographic angiography for postoperative evaluation of endovascular abdominal aortic aneurysm repair. J Vasc Surg 2000; 32:1142–1148 26. Raman KG, Missig-Carroll N, Richardson T, Muluk SC, Makaroun MS. Color-flow duplex ultra-



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair sound scan versus computed tomographic scan in the surveillance of endovascular aneurysm repair. J Vasc Surg 2003; 38:645–651 27. Nyheim T, Staxrud LE, Rosen L, Slagsvold CE, Sandbaek G, Jorgensen JJ. Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans? Acta Radiol 2013; 54:54–58 28. Han SM, Patel K, Rowe VL, Perese S, Bond A, Weaver FA. Ultrasound-determined diameter measurements are more accurate than axial computed tomography after endovascular aortic aneurysm repair. J Vasc Surg 2010; 51:1381–1387 29. Parent FN, Meier GH, Godziachvili V, et al. The incidence and natural history of type I and type II endoleak: a 5-year follow-up assessment with color duplex ultrasound scan. J Vasc Surg 2002; 35:474–481 30. Arko FR, Filis KA, Siedel SA, et al. Intrasac flow velocities predict sealing of type II endoleaks after endovascular abdominal aortic aneurysm repair. J Vasc Surg 2003; 37:8–15 31. Bredahl K, Long A, Taudorf M, et al. Volume estimations of the aortic sac after EVAR using 3-D ultrasound: a novel, accurate, and promising technique. Eur J Vasc Endovasc Surg 2013; 45:450–455 32. Arsicot M, Lathelize H, Martinez R, Marchand E, Picquet J, Enon B. Follow-up of aortic stentgrafts: comparison of the volumetric analysis of the aneurysm sac by ultrasound and CT. Ann Vasc Surg 2014 [Epub ahead of print] 33. Mirza TA, Karthikesalingam A, Jackson D, et al. Duplex ultrasound and contrast-enhanced ultrasound versus computed tomography for the detection of endoleak after EVAR: systematic review and bivariate meta-analysis. Eur J Vasc Endovasc Surg 2010; 39:418–428 34. Bakken AM, Illig KA. Long-term follow-up after endovascular aneurysm repair: is ultrasound alone enough? Perspect Vasc Surg Endovasc Ther 2010; 22:145–151 35. Ten Bosch JA, Rouwet EV, Peters CT, et al. Contrast-enhanced ultrasound versus computed tomographic angiography for surveillance of endovascular abdominal aortic aneurysm repair. J Vasc Interv Radiol 2010; 21:638–643 36. Cantisani V, Ricci P, Grazhdani H, et al. Prospective comparative analysis of colour-Doppler ultrasound, contrast-enhanced ultrasound, computed tomography and magnetic resonance in detecting endoleak after endovascular abdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg 2011; 41:186–192 37. Gürtler VM, Sommer WH, Meimarakis G, et al. A comparison between contrast-enhanced ultrasound imaging and multislice computed tomography in detecting and classifying endoleaks in the followup after endovascular aneurysm repair. J Vasc Surg

2013; 58:340–345 38. Millen A, Canavati R, Harrison G, et al. Defining a role for contrast-enhanced ultrasound in endovascular aneurysm repair surveillance. J Vasc Surg 2013; 58:18–23 39. Iezzi R, Cotroneo AR, Basilico R, Simeone A, Storto ML, Bonomo L. Endoleaks after endovascular repair of abdominal aortic aneurysm: value of CEUS. Abdom Imaging 2010; 35:106–114 40. Abbas A, Hansrani V, Sedgwick N, Ghosh J, McCollum CN. 3D contrast enhanced ultrasound for detecting endoleak following endovascular aneurysm repair (EVAR). Eur J Vasc Endovasc Surg 2014; 47:487–492 41. Beeman BR, Doctor LM, Doerr K, McAfee-Bennett S, Dougherty MJ, Calligaro KD. Duplex ultrasound imaging alone is sufficient for midterm endovascular aneurysm repair surveillance: a cost analysis study and prospective comparison with computed tomography scan. J Vasc Surg 2009; 50:1019–1024 42. Chaer RA, Gushchin A, Rhee R, et al. Duplex ultrasound as the sole long-term surveillance method post-endovascular aneurysm repair: a safe alternative for stable aneurysms. J Vasc Surg 2009; 49:845–850 43. Pitton MB, Schweitzer H, Herber S, et al. MRI versus helical CT for endoleak detection after endovascular aneurysm repair. AJR 2005; 185:1275– 1281 44. van der Laan MJ, Bartels LW, Viergever MA, Blankensteijn JD. Computed tomography versus magnetic resonance imaging of endoleaks after EVAR. Eur J Vasc Endovasc Surg 2006; 32:361– 365 45. Habets J, Zandvoort HJ, Reitsma JB, et al. Magnetic resonance imaging is more sensitive than computed tomography angiography for the detection of endoleaks after endovascular abdominal aortic aneurysm repair: a systematic review. Eur J Endovasc Surg 2013; 45:340–350 46. Resta EC, Secchi F, Giardino A, et al. Non-contrast MR imaging for detecting endoleak after abdominal endovascular aortic repair. Int J Cardiovasc Imaging 2013; 29:229–235 47. Ichihashi S, Marugami N, Tanaka T, et al. Preliminary experience with superparamagnetic iron oxideenhanced dynamic magnetic resonance imaging and comparison with contrast-enhanced computed tomography in endoleak detection after endovascular aneurysm repair. J Vasc Surg 2013; 58:66–72 48. Ellozy SH, Carroccio A, Lookstein RA, et al. Abdominal aortic aneurysm sac shrinkage after endovascular aneurysm repair: correlation with chronic sac pressure measurement. J Vasc Surg 2006; 43:2–7 49. Becquemin JP, Kelley L, Zubilewicz T, Desgranges P, Lapeyre M, Kobeiter H. Outcomes of secondary interventions after abdominal aortic aneurysm

endovascular repair. J Vasc Surg 2004; 39:298– 305 50. Mehta M, Sternbach Y, Taggert JB, et al. Longterm outcomes of secondary procedures after endovascular aneurysm repair. J Vasc Surg 2010; 52:1442–1449 51. Elkouri S, Gloviczki P, McKusick MA, et al. Perioperative complications and early outcome after endovascular and open surgical repair of abdominal aortic aneurysms. J Vasc Surg 2004; 39:497–505 52. Liaw JV, Clark M, Gibbs R, Jenkins M, Cheshire N, Hamady M. Update: complications and management of infrarenal EVAR. Eur J Radiol 2009; 71:541–551 53. Stavropoulos SW, Clark TW, Carpenter JP, et al. Use of CT angiography to classify endoleaks after endovascular repair of abdominal aortic aneurysms. J Vasc Interv Radiol 2005; 16:663–667 54. 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 55. Aburahma AF, Campbell JE, Mousa AY, et al. Clinical outcomes for hostile versus favorable neck anatomy in endovascular aortic aneurysm repair using modular devices. J Vasc Surg 2011; 54:13– 21 56. Bastos Gonçalves F, Verhagen HJ, Chinsakchai K, et al. The influence of neck thrombus on clinical outcome and aneurysm morphology after endovascular aneurysm repair. J Vasc Surg 2012; 56:36–44 57. Wyss TR, Dick F, Brown LC, Greenhalgh RM. The influence of thrombus, calcification, angulation, and tortuosity of attachment sites on the time to the first graft-related complication after endovascular aneurysm repair. J Vasc Surg 2011; 54:965–971 58. Hellinger JC. Endovascular repair of thoracic and abdominal aortic aneurysm: pre- and postprocedural imaging. Tech Vasc Interv Radiol 2005; 8:2–15 59. Becquemin JP, Allaire E, Desgranges P, Kobeiter H. Delayed complications following EVAR. Tech Vasc Interv Radiol 2005; 8:30–40 60. Arko FR 3rd, Murphy EH, Boyes C, et al. Current status of endovascular aneurysm repair: 20 years of learning. Semin Vasc Surg 2012; 25:131–135 61. Moulakakis KG, Mylonas SN, Avgerinos E, et al. The chimney graft technique for preserving visceral vessels during endovascular treatment of aortic pathologies. J Vasc Surg 2012; 55:1497–1503 62. Güntner O, Zeman F, Wohlgemuth WA, et al. Inferior mesenteric arterial type II endoleaks after endovascular repair of abdominal aortic aneurysm: are they predictable? Radiology 2014; 270:910–919 63. Ward TJ, Cohen S, Fischman AM, et al. Preoperative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow-up. J Vasc Interv Radiol



Picel and Kansal 2013; 24:49–55 64. Axelrod DJ, Lookstein RA, Guller J, et al. Inferior mesenteric artery embolization before endovascular aneurysm repair: technique and initial results. J Vasc Interv Radiol 2004; 15:1263–1267 65. Alerci M, Giamboni A, Wyttenbach R, et al. Endovascular abdominal aneurysm repair and impact of systematic preoperative embolization of collateral arteries: endoleak analysis and long-term followup. J Endovasc Ther 2013; 20:663–671 66. Burbelko M, Kalinowski M, Heverhagen JT, et al. Prevention of type II endoleak using the AMPLATZER vascular plug before endovascular aneurysm repair. Eur J Endovasc Surg 2014; 47:28–36 67. Sheehan MK, Hagino RT, Canby E, et al. Type 2 endoleaks after abdominal aortic aneurysm stent grafting with systematic mesenteric and lumbar coil embolization. Ann Vasc Surg 2006; 20:458–463 68. Gould DA, McWilliams R, Edwards RD, et al. Aortic side branch embolization before endovascular aneurysm repair: incidence of type II endoleak. J Vasc Interv Radiol 2001; 12:337–341 69. Fan CM, Rafferty EA, Geller SC, et al. Endovascular stent-graft in abdominal aortic aneurysms: the relationship between patent vessels that arise from the aneurysmal sac and early endoleak. Radiology 2001; 218:176–182 70. Aburahma AF, Mousa AY, Campbell JE, et al. The relationship of preoperative thrombus load and location to the development of type II endoleak and sac regression. J Vasc Surg 2011; 53:1534–1541 71. Ward TJ, Cohen S, Patel RS, et al. Anatomic risk factors for type-2 endoleak following EVAR: a retrospective review of preoperative CT angiography in 326 patients. Cardiovasc Intervent Radiol 2014; 37:324–328 72. Brountzos E, Karagiannis G, Panagiotou I, Tzavara C, Efstathopoulos E, Kelekis N. Risk factors for the development of persistent type II endoleaks after endovascular repair of infrarenal abdominal aortic aneurysms. Diagn Interv Radiol 2012; 18:307–313 73. Nolz R, Tuefelsbauer H, Asenbaum U, et al. Type II endoleak after endovascular repair of abdominal aortic aneurysms: fate of the aneurysm sac and neck changes during long-term follow-up. J Endovasc Ther 2012; 19:193–199 74. Zhou W, Bley E Jr, Varu V, et al. Outcome and clinical significance of delayed endoleaks after endovascular aneurysm repair. J Vasc Surg 2014; 59:915–920 75. Sidloff DA, Stather PW, Choke E, Bown MJ, Sayers RD. Type II endoleak after endovascular aneurysm repair. Br J Surg 2013; 100:1262–1270 76. Baum RA, Carpenter JP, Golden MA, et al. Treatment of type 2 endoleaks after endovascular repair of abdominal aortic aneurysms: comparison of transarterial and translumbar techniques. J Vasc Surg 2002; 35:23–29

W366

77. Nevala T, Biancari F, Manninen H, et al. Type II endoleak after endovascular repair of abdominal aortic aneurysm: effectiveness of embolization. Cardiovasc Intervent Radiol 2010; 33:278–284 78. Stavropoulos SW, Park J, Fairman R, Carpenter J. Type 2 endoleak embolization comparison: translumbar embolization versus modified transarterial embolization. J Vasc Interv Radiol 2009; 20:1299– 1302 79. Abularrage CJ, Patel VI, Conrad MF, Schneider EB, Cambria RP, Kwolek CJ. Improved results using Onyx glue for the treatment of persistent type 2 endoleak after endovascular aneurysm repair. J Vasc Surg 2012; 56:630–636 80. Müller-Wille R, Wolhlgemuth WA, Heiss P, et al. Transarterial embolization of type II endoleaks after EVAR: the role of ethylene vinyl alcohol copolymer (Onyx). Cardiovasc Intervent Radiol 2013; 36:1288–1295 81. Khaja MS, Park AW, Swee W, et al. Treatment of type II endoleak using Onyx with long-term imaging follow-up. Cardiovasc Intervent Radiol 2014; 37:613–622 82. Stavropoulos SW, Marin H, Fairman RM, et al. Recurrent endoleak detection and measurement of aneurysm size with CTA after coil embolization of endoleaks. J Vasc Interv Radiol 2005; 16:1313– 1317 83. Sampaio SM, Panneton JM, Mozes G, et al. AneuRx device migration: incidence, risk factors, and consequences. Ann Vasc Surg 2005; 19:178–185 84. Sternbergh WC 3rd, Money SR, Greenberg RK, Chuter TA; Zenith Investigators. Influence of endograft oversizing on device migration, endoleak, aneurysm shrinkage, and aortic neck dilation: results from the Zenith Multicenter Trial. J Vasc Surg 2004; 39:20–26 85. Resch T, Ivancev K, Brunkwall J, Nyman U, Malina M, Lindblad B. Distal migration of stent-grafts after endovascular repair of abdominal aortic aneurysms. J Vasc Interv Radiol 1999; 10:257–264 86. Fransen GA, Desgranges P, Leheij RJ, Harris PL, Becquemin JP; EUROSTAR Collaborators. Frequency, predictive factors, and consequences of stent-graft kink following endovascular AAA repair. J Endovasc Ther 2003; 10:913–918 87. Early H, Atkins M. Technical tips for managing difficult iliac access. Semin Vasc Surg 2012; 25:138–143 88. Maleux G, Koolen M, Heye S, Nevelsteen A. Limb occlusion after endovascular repair of abdominal aortic aneurysms with supported endografts. J Vasc Interv Radiol 2008; 19:1409–1412 89. Lalka S, Dalsing M, Cikrit D, et al. Secondary interventions after endovascular abdominal aortic aneurysm repair. Am J Surg 2005; 190:787–794 90. Cernohorsky P, Reijnen MM, Tielliu IF, van Sterkenburg SM, van den Dungen JJ, Zeebreqts CJ.

The relevance of aortic endograft prosthetic infection. J Vasc Surg 2011; 54:327–333 91. Fatima J, Duncan AA, de Grandis E, et al. Treatment strategies and outcomes in patients with infected aortic endografts. J Vasc Surg 2013; 58:371–379 92. Maleux G, Koolen M, Heye S. Complications after endovascular aneurysm repair. Semin Intervent Radiol 2009; 26:3–9 93. Ruby BJ, Cogbill TH. Aortoduodenal fistula 5 years after endovascular abdominal aortic aneurysm repair with the Ancure stent graft. J Vasc Surg 2007; 45:834–836 94. Saratzis N, Saratzis A, Melas N, Ktenidis K, Kiskinis D. Aortoduodenal fistulas after endovascular stent-graft repair of abdominal aortic aneurysms: single-center experience and review of the literature. J Endovasc Ther 2008; 15:441–448 95. Wald R, Waikar SS, Liangos O, Pereira BJ, Chertow GM, Jaber BL. Acute renal failure after endovascular vs open repair of abdominal aortic aneurysm. J Vasc Surg 2006; 43:460–466 96. Antonello M, Menegolo M, Piazza M, Bonfante L, Gergo F, Frigatti P. Outcomes of endovascular aneurysm repair on renal function compared with open repair. J Vasc Surg 2013; 58:886–893 97. Murphy EH, Arko FR. Technical tips for abdominal aortic endografting. Semin Vasc Surg 2008; 21:25–30 98. Belenky A, Atar E, Orron DE, et al. Endovascular abdominal aortic aneurysm repair using transvenous intravascular US catheter guidance in patients with chronic renal failure. J Vasc Interv Radiol 2014; 25:702–706 99. Coscas R, Kobeiter H, Desgranges P, Becquemin JP. Technical aspects, current indications, and results of chimney grafts for juxtarenal aortic aneurysms. J Vasc Surg 2011; 53:1520–1527 100.Donas KP, Torsello G, Bisdas T, Osada N, Schonefeld E, Pitoulias GA. Early outcomes for fenestrated and chimney endografts in the treatment of pararenal aortic pathologies are not significantly different: a systemic review with pooled data analysis. J Endovasc Ther 2012; 19:723–728 101. Dadian N, Ohki T, Veith FJ, et al. Overt colon ischemia after endovascular aneurysm repair: the importance of microembolization as an etiology. J Vasc Surg 2001; 34:986–996 102. Perry RJ, Martin MJ, Eckert MJ, Sohn VY, Steele SR. Colonic ischemia complicating open vs endovascular abdominal aortic aneurysm repair. J Vasc Surg 2008; 48:272–277 103. Rutherford RB. Structural failures in abdominal aortic aneurysm stentgrafts: threat to durability and challenge to technology. Semin Vasc Surg 2004; 17:294–297 104. Ueda T, Takaoka H, Petrovitch I, Rubin GD. Detection of broken sutures and metal-ring fractures



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair in AneuRx stent-grafts by using three-dimensional CT angiography after endovascular abdominal aortic aneurysm repair: association with late endoleak development and device migration. Radiology 2014 [Epub ahead of print] 105. Bensley RP, Hurks R, Huang Z, et al. Ultrasoundguided percutaneous endovascular aneurysm re-

pair success is predicted by access vessel diameter. J Vasc Surg 2012; 55:1554–1561 106. Manunga JM, Gloviczki P, Oderich GS, et al. Femoral artery calcification as a determinant of success for percutaneous access for endovascular abdominal aortic aneurysm repair. J Vasc Surg 2013; 58:1208–1212

107. Minion DJ, Davenport DL. Access techniques for EVAR: percutaneous techniques and working with small arteries. Semin Vasc Surg 2012; 25:208–216 108. Mousa AY, Campbell JE, Broce M, et al. Predictors of percutaneous access failure requiring open femoral surgical conversion during endovascular aortic aneurysm repair. J Vasc Surg 2013; 58:1213–1219

A

B

C

D

E

Fig. 1—68-year-old man who underwent endovascular abdominal aortic aneurysm repair (EVAR) and experienced device migration and structural failure. A, CT maximum-intensity-projection (MIP) image obtained 1 month after EVAR shows stent-graft positioned just below most inferior renal artery (arrow). B, Abdominal radiograph obtained 2 years later suggests increased angulation of proximal portion of stent-graft as well as stent fracture (arrow). C and D, Interval surveillance scout radiograph (C) and CT MIP image (D) show increased angulation of stent-graft as well as migration. Stent-graft is now 2.5 cm inferior to left renal artery (arrow, D). E, Postoperative radiograph was obtained after failed endovascular repair. Proximal portion of stent-graft was resected and aorta repaired with polyester fiber (Dacron, DuPont) graft.



Picel and Kansal

A

B

Fig. 2—71-year-old man who underwent ultrasound surveillance after endovascular abdominal aortic aneurysm repair. A, Sagittal gray-scale ultrasound image identifies stent-graft (arrow) and accurately measures maximal aortic diameter. B, Sagittal color ultrasound image shows blood flow entering proximal neck of stent-graft (arrow) without evidence of endoleak.

Fig. 3—77-year-old woman with type I endoleak. A, Axial CT image shows contrast material outside stent-graft but within aneurysm sac (arrow) indicating endoleak near proximal landing zone. B, Sagittal reformatted CT image shows contrast material within region of proximal attachment site (arrow) consistent with type Ia endoleak.

A

W368

B



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair Fig. 4—75-year-old man with chimney grafts placed to preserve flow to renal arteries. A, Unenhanced axial CT image shows bilateral chimney stents (arrows) running parallel to aortic stent-graft. B, Coronal maximum-intensity-projection CT image shows renal chimney stents (arrows) extending proximal to covered portion of aortic stent-graft to preserve flow to renal arteries.

A

A

B

B

Fig. 5—81-year-old man with type II endoleak. A and B, Axial (A) and oblique sagittal reformatted (B) CT images show contrast material within aneurysm sac adjacent to patent inferior mesenteric artery (arrow) consistent with type II endoleak. In type II endoleak, contrast material will often appear in periphery of aneurysm sac.



Picel and Kansal

A

B

C Fig. 6—86-year-old man with type II endoleak. A, Axial CT image shows contrast material within periphery of aneurysm sac (arrow). Contrast material was also seen anteriorly in aneurysm sac adjacent to inferior mesenteric artery (IMA). This patient has type II endoleaks supplied by both IMA and lumbar arteries. B, Fluoroscopic image obtained during transarterial therapy. Microcatheter was navigated from superior mesenteric artery through collateral vessels and into IMA. Coils were placed (arrow) to occlude IMA and treat type II endoleak. Coil embolization was also performed of contributing lumbar artery. C, Endoleak persisted and translumbar therapy was performed. Axial CT image shows percutaneous placement of needle (arrow) to directly access aneurysm sac. D, Contrast material injection through percutaneous access shows type II endoleak supplied by left L4 lumbar artery (arrow). Embolization was performed with metallic coils and ethylene vinyl alcohol copolymer (Onyx, ev3). E, Posttreatment sagittal CT image shows metallic artifact (arrow) and high-density material within aneurysm sac from coils placed during endoleak treatment.

D

W370

E



Postprocedure Monitoring of Endovascular Abdominal Aortic Aneurysm Repair

A

B

C

Fig. 7—78-year-old man with stent-graft migration and type III endoleak. A, Axial CT image shows separation of proximal portion of stent-graft resulting in large type III endoleak with immediate risk of rupture. B, Coronal CT reconstructed maximum-intensity-projection image shows disassociation of endograft main body from proximal cuff (arrow). C, Repair was accomplished by placement of additional stent-graft component (arrow) to seal large type III endoleak.

A

B

C

Fig. 8—88-year-old woman with limb occlusion. A and B, Axial (A) and oblique sagittal reformatted (B) CT images show occlusion of left iliac limb (arrow) extending proximally to bifurcation of endograft. C, Three-dimensional reconstructed CT image shows femoral-to-femoral artery bypass (arrow) placed to salvage endovascular repair and perfuse left lower extremity. Left external iliac artery fills in retrograde fashion from surgical bypass.


Picel and Kansal


Fig. 9—62-year-old man with endograft infection. A, Axial CT image shows inflammatory reaction (arrow) near proximal attachment of infected stent-graft. B, Axial CT image at level of stent-graft limbs shows perigraft inflammation and gas (arrow) consistent with infection. Bacteremia persisted after several weeks of IV antibiotic therapy. Infected endograft was removed, and aortobiiliac bypass graft was placed.

A

A

B

B

Fig. 10—77-year-old man with aortoenteric fistula. A and B, Axial (A) and sagittal (B) unenhanced CT images show air and oral contrast material (arrow) adjacent to endograft within aneurysm sac, consistent with aortoenteric fistula due to erosion of endograft into duodenum.

F O R YO U R I N F O R M AT I O N

The reader is directed to a related article, titled “Essentials of Endovascular Abdominal Aortic Aneurysm Repair Imaging: Preprocedural Assessment,” which begins on page W347.

W372
