The device is a self-expanding modular system composed of serpentine-shaped nitinol stents integrated into a woven polyester matrix (Fig. 34.2). The stents are discontinuous and are spaced along a full-length nitinol spine. The latter wire provides columnar strength to a graft that is otherwise flexible enough to accommodate aortoiliac angulations. The spine also prevents twisting and longitudinal infolding of the endograft during deployment. The proximal aortic fixation end has a 1.5-cm uncovered nitinol frame that allows for transrenal fixation of the device. These characteristics may allow increased potential for treating patients with challenging aortic neck configurations [4, 5]. Since its original introduction, the endograft has been modified to include the use of a thinner, low-profile graft fabric to create the Talent Low-Porosity System (LPS). Later, the Talent endograft nitinol springs were chemically treated to enhance durability, and the position of the iliac longitudinal connecting bar was moved from lateral to medial to improve conformability and decrease risk of kinking and thrombosis, resulting in the latest-generation Talent eLPS device. The Talent Abdominal Stent endograft has a 22F delivery system with a hydrophilic coating which does not require a delivery sheath. A 24F delivery system is required for 30 to 36-mm devices and allows treatment of up to 32-mm neck diameters with a neck length of 10 mm and <60° of angulation.

This device features a polyester graft material externally supported by an electropolished nitinol stent structure attached to the graft by sutures (Fig. 34.3). An M-shaped proximal stent with anchoring hooks is designed to fix the endograft above the renal arteries. The hydrophilic, low-profile delivery system for the main body measures between 18F and 20F, while for the iliac extensions, the sizes are 14F and 16F. A tip-capture mechanism allows separate control-release deployment of the suprarenal stent. The Endurant endograft is loaded into a low-profile delivery system, with an outer diameter ranging from 18F to 20F for the main body and from 14F to 16F for the extenders. The delivery system features a tip-capture release mechanism to ensure accurate control of suprarenal stent deployment.

This is a modular endograft system that utilizes an exoskeleton of 1-cm self-expanding elements (Fig. 34.4). The self-expanding, thin-wall polyester graft material, supported by diamond-shaped elements, supplies high radial force for reliable and secure sealing without barbs, hooks, or balloons. To date, the AneuRx Abdominal Stent Graft has undergone eight modifications since the original clinical trial. The first-generation device consisted of a stiff-body design with a pre-reduced porosity graft material and a bullet delivery system. In 1998, the endograft flexibility was increased by changing the body of the endograft from a single 5-cm nitinol stent to a series of 1-cm diamond-shaped rings. Furthermore, the graft material was changed to a reduced porosity material. In 2002, the delivery system was changed to the Xpedient Delivery System with a tapered nose cone, allowing the device to be placed without a sheath. In 2004, the graft material was again changed to the Resilient graft material, which was associated with the greatest amount of sac shrinkage as compared to other contemporary graft materials [6]. In 2005, the Xcelerant Delivery System was added, allowing for easier deployment of the endograft. In 2006, the AneuRx AAAdvantage Stent Graft was offered, which added an extended aortic body of 4 cm, contoured stent rings, longer, larger, and flared iliac limbs to decrease the number of components required for repair and enhanced radiopaque markers. Finally, in 2008 a hydrophilic coating was added to the delivery system. Currently, the AneuRx AAAdvantage Stent Graft has a 21F delivery system and may be used to treat up to 26-mm aortic neck diameters that are 15 mm in length with <45° of angulation.

This device is a modular system covered with expanded polytetrafluoroethylene (ePTFE) and supported by a nitinol stent frame (Fig. 34.5). The endograft material is bonded to the nitinol frame and thus has no suture holes in the material. The microstructure in the original device permitted selective permeability of serous fluid in a subset of patients that could be associated with endotension [7, 8], but with the addition of a non-permeable, very thin, and highly durable fluoropolymer layer, this drawback was overcome [9, 10]. The endograft consists of a bifurcated main body with a single docking limb and assorted iliac limbs. Iliac and proximal extenders are also available. The main proximal portion of the main body has a scalloped end that is entirely covered with paired nitinol anchors for fixation set at 45°. There is no mechanism for suprarenal fixation. The proximal edge is identifiable by three gold markers designed to be placed immediately below the most inferior renal artery. The main body of the device is contained in an ePTFE jacket that is stitched with a single strand of ePTFE string. This is the mechanism for deployment: the string is pulled and the stitches are released, causing endograft deployment (proximal to distal). Rotational orientation is facilitated by different length markers on the ipsilateral and contralateral endograft sides. In the new C3 Delivery System, deployment is now a three-step maneuver, including the option of re-constraining and repositioning the device. If the position is believed to be too high or too low with regard to the renal arteries, the device can be easily adjusted to reach the ideal final location. Similarly, reorientation of the contralateral gate is possible, which makes cannulation easier and less time consuming. Currently, introducer sheaths are available in 30-cm length as 12F, 18F, and 20F sheaths. Main trunks with ipsilateral leg are available in 23-mm, 26-mm, and 28.5-mm diameters with 12-mm and 14.5-mm iliac diameters. The endoprosthetic length ranges from 12 to 18 cm in 2-cm increments. The recommended aortic neck diameter ranges from 19 to 28 mm. The ipsilateral iliac treatment diameter ranges from 10 to 13.5 mm. All these devices can be delivered via the 18F sheath except for the 31-mm endograft, which requires the 20F sheath. The contralateral endograft ranges from 12 to 20 mm in 2-mm increments and is available in 9.5-cm, 10-cm, 11.5-cm, 12-cm, 13.5-cm, and 14-cm length increments. The larger diameter contralateral leg endograft (16, 18, and 20 mm) can also be used as iliac extenders. The Excluder device contains flared iliac extenders to attach to aneurysmal iliac vessels. Dedicated iliac extenders range from 10 to 14.5 mm and are available in 7-cm length increments. The recommended iliac treatment diameters range from 8 to 18.5 mm. All may be delivered via the 12F sheath except for the 16-mm to 20-mm endograft, which requires an 18F sheath. Aortic extenders range 23, 26, and 28.5 mm and are available in 3.3-cm length increments. Their recommended aortic neck diameter is 19 to 26 mm in the United States, and a range of 19 to 29 mm has been used outside the United States.

The system is tri-modulare and is composed of a bifurcated body to which the ipsilateral and contralateral branch may engage (Fig. 34.6). A wide range of bodies and bifurcated iliac branches allows to treat patients with an aortic neck from 17.5 to 31 mm and iliac arteries from 8.5 to 21 mm. The tri-modulare system allows adapting the stent to the size and characteristic anatomy of each patient. The flexibility of the body is allowed by the fact that distally to the two rings of nitinol for the proximal anchorage, the prosthesis is supported by two other very flexible rings, which, while supporting the bifurcated body, will not impair flexibility. The end of the contralateral side has a thin support of nitinol and radiopaque markers to ensure an open and visible lumen during the procedure of cannulation. The iliac branches, straight and/or flared, are equipped with support rings and radiopaque markers for the correct positioning inside the main body. The rings of support are varied but independent of one another so as to ensure an excellent flexibility to the iliac branches and prevent kinking. The iliac branches can be used to treat isolated aneurysmal iliac arteries. The flexibility characterizes also the introduction and release system that allows placing the stent in vessels anatomically very tortuous. The proximal part of the aortic bifurcated body has two rings of nitinol supported by four pairs of hooks that ensure safe anchorage of the device.

This Endovascular AAA System integrates anatomical fixation with an advanced delivery system and graft material technology (Fig. 34.7).

This new system was designed so that a few sizes will fit most vessels with respect to both diameters and length (Fig. 34.8). The modular components can be tailored during the implant procedure, with “in situ length adjustment” of the limb prostheses. This permits up to 2–3 cm of variability that can be achieved by varying the modular overlap length on each side reducing the risk of inadvertent coverage of the hypogastric orifice and, at the same time, allowing the maximum length of iliac fixation for migration prevention. The endograft design provides appropriate radial force over a relatively large range of diameters, so that four sizes can be used for aortic diameters ranging from 17 to 31 mm. Similarly, five different iliac limb diameters will accommodate iliac arteries ranging from 7 to 22 mm in size. Each iliac limb is supplied in four distinct lengths ranging from 8 to 14 cm, allowing a total aortoiliac coverage length between 13 and 21 cm. Therefore, a combination of 23 different modular components allows the operator to customize the device to the wide variety of AAA anatomy, with a significant reduction in the complexity of device selection, which is so critical in emergency settings. The Incraft device has a flared bare transrenal stent with 8–10 laser-cut barbs (size depending) located on the most cranial part of the stent for suprarenal fixation. The transrenal stent, the short segmented sealing infrarenal endoskeleton stent and the non-tilting deployment mechanism maximize the proximal seal, especially in the presence of a challenging aortic neck. The endograft is constructed of a seamless, woven polyester material supported by a series of laser-cut nitinol stents throughout its entire length. Such a design was chosen for kinking prevention, which has been associated with limb thrombosis. The Incraft stents are attached to the graft with a unique suture scheme to minimize micromotion between the stent and graft component, a mechanism believed to have a negative impact on endograft integrity with prior devices. Finally, one of the most innovative features of the device is the ultra-low profile: the integrated delivery system is 13F with a 14F (4.7 mm) outer diameter. The “catheter-like” flexibility and the elimination of sheath exchange minimize delivery problems, particularly in patients with small, diseased, and otherwise challenging access anatomy.

General accepted guidelines for EVAR include at least 10–15 mm of non-aneurysmal proximal neck, proximal neck diameter less than 30 mm, adequate access vessels (femoral/iliac arteries) at least 7 mm in diameter, minimal vessel calcification and thrombus, and a neck–body aneurysm angle ≤60°. The 2005 Excluder instructions for use recommend the following selection criteria: adequate iliac/femoral access, infrarenal aortic neck diameter ranging from 19 to 26 mm, minimum aortic neck length of 15 mm, proximal aortic neck angulation ≤60°, iliac artery treatment diameter ranging from 8 to 18.5 mm, and iliac distal vessel seal zone of at least 10 mm. Device delivery may be hindered by excessive tortuosity, calcification, or occlusive disease of femoral or iliac arteries. Additional considerations relate to the adequacy of collateral flow for occluded branches, such as an indispensable inferior mesenteric artery or accessory renal artery. The most common obstacle for EVAR is inadequate proximal anatomy. Self-expanding stents may be used more frequently to treat AAA with neck dilatation compared with balloon-expandable stents. An analysis comparing Excluder and the balloon-expandable Lifepath found this factor to be correlated with a higher rate of device migration seen in the Excluder device in this series [11]. A review from the EUROSTAR database analyzed 1,152 patients treated with EVAR having severe neck angulation (>60°) with Excluder, Talent, or Zenith endografts [12]. All three had acceptable outcomes in patients with severe neck angulation, with the Excluder and Zenith having increased risk for short-term type I endoleak and device migration and the Talent device having increased long-term risk of type I endoleak and secondary intervention. Favorable anatomic criteria allow use of any of the current commercially available endografts for EVAR. However, it has become apparent that certain features of proximal neck diameter, length, and angulation, or iliac anatomy characteristics favor some devices over another. The low-profile delivery is one such example. Also, the scalloped proximal edge makes precision delivery possible for tight proximal anatomy. A unique characteristic of the Excluder is its rapid deployment mechanism. This rapid deployment of a self-expanding device with proximal fixation in the setting of tortuosity and path rotation may lead to unexpected shortening and a more distal position than expected in inexperienced hands. Potential consequences of unexpected distal migration could include inadvertent hypogastric artery occlusion. Whittaker et al. found that this event occurred in 11 % of limbs studied with a shortening of graft path 1 cm or more [13]. Moreover, they noted that graft path shortening was affected more by anatomic factors than by Excluder device factors. Graft rotation was the most difficult pattern to predict preoperatively. Most patients will be assessed with three-dimensional reconstruction of multi-detector CT angiography (MDCTA). This has replaced previous modalities such as “road-map” angiogram or marker catheter as the best method for pre-intervention planning. Features such as tortuosity and rotation require special consideration in preoperative planning. Whittaker et al. reported that three-dimensional computer-aided measurement, planning, and simulation software was very accurate for preoperative planning with the Excluder device and more accurate than using marker catheter angiography [14]. Availability of several commercial devices with different properties with regard to proximal fixation, deployment accuracy, endograft flexibility, and size of introduction system enables to tailor the device selection according to each patient’s AAA anatomy. Zenith endografts were mainly used for short proximal necks in view of the suprarenal fixation of the bare stent with hooks and barbs. In addition, in view of the versatility of the Zenith Tri-Fab system in which the length of both limbs can be chosen after insertion of the main body, the endograft may be appropriate also in aneurysms where accurate length measurement proves difficult (e.g., angulation or short common iliac arteries). This feature is shared also by the Incraft Stent Graft System. The Talent endografts were initially used for proximal necks with a large diameter, but this advantage was lost when the Zenith equally featured larger proximal diameter sizes. Excluder endografts were preferred in patients with narrow and angulated iliac arteries because of flexible and thinner wall limbs. In July 2004, the Excluder underwent an important modification with the introduction of a lower porosity graft material. The Talent prosthesis was recently replaced by Medtronic with the Endurant. This new prosthesis, always with suprarenal attachment, has greater flexibility and conformability in the aortic vessel and requires thinner, dedicated introducers.

The deployment technique for a two-piece modular device involves passage through one femoral artery of a sheath containing a body and the ipsilateral iliac limb. The superior end of the body is positioned just below the lowermost renal artery. The contralateral iliac limb is inserted through the opposite femoral artery and is overlapped with a short stump in the body of the device. The end result is a percutaneous Y-graft, with some important differences as compared to surgical grafts: the attachment sites in the infrarenal aortic neck, iliac arteries, and within the endograft are not sutured, and the aortic side branches are not ligated. Since the attachment sites are not hand sutured, they rely on the radial force of the stents to provide a hemostatic seal. Fixation at the attachment sites is also important to prevent endograft migration. Some manufacturers achieve this by adding hooks or barbs on the infrarenal stent. Some devices incorporate a bare suprarenal stent with or without hooks. This suprarenal stent may extend as high as the superior mesenteric artery.

The anatomic classification of endoleaks is based upon the source of the inflow into the aneurysm sac, regardless of the number and type of other vessels involved in the outflow. The initial definition differentiated between four types of endoleak, but it was expanded in 1999 to include endotension (type V) (Table 34.1).

Contrast MDCTA is considered the imaging technique of choice for endoleak detection. Indeed, MDCTA is reported to be superior to aortography for the demonstration of small leaks. However, selective angiography is superior to MDCTA for the detection of inflow and outflow vessels (Fig. 34.11b). Deceitful MDCTA images, including calcifications, contrast within the folds of unsupported portions of the endograft, and residual contrast inside the aneurysm sac from the initial procedure may erroneously suggest the presence of endoleaks when noninvasive angiographic follow-up is obtained within 1–3 days after implantation. Of note, “pseudo-endoleaks” are seen in up to 57 % of patients.

Color Doppler ultrasound (CDUS) is a noninvasive and cost-effective imaging modality that can be used for endoleak assessment. It is highly dependent on the operator and has limitations in obese patients and in those with excessive bowel gas. Patients should be evaluated after 5–6 h fasting, in the supine and lateral position. The aorta is evaluated both transversally and longitudinally. A leak is suspected when a reproducible color and Doppler signal inside the aneurysm is visualized. Variable success is reported for the detection and localization of the source of endoleaks with ultrasound, depending on technical factors, imaging protocol, and image quality. Overall, the reported sensitivity for endoleak detection ranges between 12 and 100 %, with specificities ranging between 74 and 99 % [34]. Although these noninvasive techniques are reliable in detecting an endoleak, the characterization and type of endoleak, as well as endovascular treatment planning can still be difficult.

Metals subjected to aortic pulsation pressures may fracture. The iliac limbs of the device may also become distorted and angulated within the residual space of the aneurysm.

These adverse events during or after EVAR can be categorized as complications owing to surgical exposure of the access arteries or the percutaneous approach, ischemic complications owing to intentional or inadvertent clot embolization or covering of an aortic side branch, stenosis or occlusion of an endograft limb, infection of the endograft or aneurysm sac, and contrast-induced nephropathy.

Endograft limb thrombosis is a known complication of EVAR, especially in unsupported endografts. Indeed, it can occur in as many as 40 % of cases treated with this type of devices [49, 50]. The underlying mechanism is most frequently kinking of the unsupported endograft limb. Second-generation supported endografts perform significantly better with regard to limb thrombosis and have shown a significantly lower rate of limb occlusion, ranging between 0 and 5 % [51]. Most of the limb thrombotic events occur within the first 2 months after EVAR, and the underlying causes are endograft kinking and extension of the small-diameter endograft into the external iliac artery [52, 53]. Recently, it has been demonstrated that limb occlusion may also occur 4–5 years after EVAR [54]. The mechanism of late limb occlusion can be migration and dislocation of an endograft component causing major hemodynamic turbulence and, eventually, limb or entire endograft thrombosis. Treatment of limb occlusion includes various surgical and endovascular revascularization techniques. The best treatment option depends on the patient’s general status as well as on specific endograft and excluded aneurysm changes.

In contrast to limb thrombosis, incidentally found mural thrombotic deposits are much more frequent in both first-generation endografts (20 %) and second-generation supported endografts (17–33 %) [55]. A circumferential layer of thrombotic material has been observed more in the Zenith endografts than in the Excluder endografts, but they are clinically silent and are not associated with potential endograft thrombosis or distal embolization (Fig. 34.17). Additionally, there is no difference in survival among patients presenting with mural deposits in their endograft compared with patients without this thrombotic layer. Based on these observations, additional treatment in the form of relining the endograft with another endograft or administering any type of anticoagulant therapy cannot be recommended.

The incidence of endograft infection is 0.5–1 %. If untreated, infection can result in generalized sepsis and death [56]. There are multiple causes of this complication. Endograft contamination during EVAR seems to be the source of early infection. Secondary infection from a remote source is another pathophysiological mechanism. van den Berg et al. reported an endograft infection following septic complication of a kidney stone 1 year after EVAR [57]. Another case of endograft infection after EVAR has been reported in a patient who underwent an appendectomy for appendicitis and peri-appendicular abscess formation 1 month prior to EVAR. Another cause of infection is an aortoenteric fistula. Multiple mechanisms of aortoenteric fistula creation have been described and include endograft migration, erosion of the aorta and duodenum by embolization coils, fabric rupture, inflammatory nature of the aneurysm, and bacterial aortitis with chronic duodenal erosion [58–61]. Diagnosis of endograft infection is based on clinical and radiological findings. Leukocytosis, fever, and back pain are typical clinical signs, while MDCTA may show fluid collection around the rim of the aneurysmal sac. Air bubbles may also be seen within the aneurysm sac [62, 63]. Puncture of the collection or sac for microbiological analysis often gives the definitive diagnosis. After intravenous administration of antibiotics, treatment is always resection of the endograft and aneurysm sac, followed by extra-anatomic bypass or in situ venous bypass.

Although patients receiving EVAR are spared the ischemic insult of aortic cross-clamping and have less perioperative hemorrhage [64, 65], the potential nephrotoxicity of large contrast volume must be considered. Correct positioning and deployment of the endograft strictly needs high-quality fluoroscopy and digital subtraction angiography imaging using injection of a contrast agent. In addition, repeated administration of contrast during periprocedural evaluation and follow-up surveillance with MDCTA represents an additional risk for progressive renal dysfunction [66, 67]. Although an average contrast volume of 50–100 mL is commonly needed for an EVAR procedure, higher amounts are not infrequently used as a result of multiple angiographies that may be needed, particularly in complex anatomy for correct endograft positioning and for assessment and treatment of type I endoleak at the proximal or distal fixation sites after endograft implantation. Contrast-induced nephropathy, resulting in acute renal failure, occurs in 6.7 % of cases according to a nationwide survey by Wald et al. [68]. To avoid contrast-induced renal complications, carbon dioxide (CO₂) can be used as an alternative contrast agent [69, 70].

In addition to contrast agents, other factors may be responsible for acute kidney injury after EVAR. Manipulation and positioning of the endograft within the aneurysm together with balloon inflation at the proximal fixation site may result in thromboembolism of the renal arteries and renal infarction. Moreover, the type of endograft used for proximal fixation in AAA may have an influence on renal function. Indeed, suprarenal fixation of the endograft is still creating concerns in regards to long-term effects. Interference with renal artery flow, narrowing of the renal ostium, renal infarction, and biological response of the aorta may be the result of continued injury from the suprarenal fixation stent and may play a role in renal function deterioration over time [71, 72].

The most common method of evaluating changes in aneurysm sac size is serial MDCTA and measuring the widest diameter for comparison (Fig. 34.14). Ultrasound screening is useful to evaluate sac diameter and to look for evidence of endoleaks, but it may not be sensitive enough to adequately assess early changes. Also, lateral plain X-ray has been used to evaluate graft migration by correlating graft markers with bony landmarks. The most sensitive method for detecting sac changes appears to be three-dimensional volumetric analysis by MDCTA [8]. Serial MDCTA has the benefit of enhanced information compared with ultrasound or plain radiograph. However, the financial burden, cumulative radiation exposure, and potential renal impairment from repeated contrast agent loads are a concern. It has been suggested that if an aneurysm is stable or reduced in size at 12-month MDCTA, it could safely be followed with clinical and ultrasound evaluation. This recommendation is based, in part, on the improved performance of the low-permeability endograft that markedly reduced the rates of endotension and sac expansion at 1-year follow-up. Although this improved short-term performance is encouraging, late expansion is still a concern and the importance of long-term serial evaluation should be emphasized. Another screening approach is to obtain a non-contrast CT image at follow-up. This would provide good information about device migration or deformation, aneurysm sac size, and stent fracture without exposing the patients to contrast agent administration. Screening with magnetic resonance angiography (MRA) is another option and is suitable for the Talent, Excluder, and Quantum low-permeability endografts but not for Zenith or Lifepath endografts due to artifact susceptibility [73].

Although, in general, cardiac surgeons manage thoracic segments of the aorta and vascular surgeons take care of abdominal aneurysms, the diagnosis and medical care of most aortic pathologies is frequently the responsibility of cardiologists. In light of this fact and considering the emergence of endovascular interventions for this disorder, it is important for cardiologists to gain confidence in managing at least the most frequent presentations of thoracic aortic aneurysms (TAA). Accordingly, it is also important for cardiologists to know the clinical and endovascular management of patients with TAA.