EVAR - the devices part2

http://dqsendovascular.blogspot.kr/2012/10/evar-devices-summary.html

A number of investigational devices are in early clinical testing phases. The essential features of the grafts approved for use in the United States and clinical data supporting them are discussed below.

AneuRx® — The AneuRx® AAAdvantage® stent-graft (table 1) is a modular, bifurcated graft of woven polyester sutured to and supported by a self-expanding nitinol exoskeleton introduced as a second-generation device in 2008 with alterations to the delivery system.

The main device is available in diameters that range from 20 to 28 mm for the main body and 12 to 16 mm for the ipsilateral limb, and in lengths of 13.5 or 16.5 cm [7]. The contralateral iliac stent component ranges from 12 to 16 mm in diameter with 8.5 and 11.5 cm lengths. The internal diameter of the delivery sheath for all the bifurcated grafts is 21 French (7 mm) and the sheaths for other components range from 15 to 19 French (5 to 6.33 mm).

The AneuRx® stent graft was approved for use in the United States in 1999 based upon the outcomes of phase II trials that included 1192 patients, 1019 of whom received the device configuration that is currently marketed [8,9]. The early stiff graft design used in phase I and early phase II studies was replaced with a more flexible, segmented graft.
The Phase II trial was a prospective, nonrandomized study that compared endovascular repair using the AneuRx® stent graft with standard open surgical repair . The AneuRx® stent graft was associated with a significant reduction in surgical blood loss, decreased transfusion requirements, decreased length of intensive-care unit (ICU) stay, earlier return of gastrointestinal function, and earlier time to discharge. Two intraoperative ruptures were reported (0.17 percent) and three patients suffered from postoperative aneurysm rupture (
Using a subgroup of the patient cohort from Medtronic's investigational premarket study, aneurysm-related mortality with the AneuRx® graft was evaluated . The perioperative (30-day) death rate was 1.61 percent. Among 931 patients followed for an average of 3.48 years, the rate of abdominal aortic aneurysm-related mortality was 0.18 percent after 3 years (excluding perioperative deaths), and 1.39 percent thereafter. The authors concluded that the longer-term mortality associated with implantation of an AneuRx® graft (as determined in this study) probably exceeds the mortality rate of open repair (based on historical data) at some point in time, likely about four years after implantation.

Zenith® — The Zenith® abdominal endograft (table 1) is a bifurcated, modular, three-component system. It is composed of woven polyester (ie, Dacron®) sutured to stainless steel Gianturco Z-stents, with a bare suprarenal stent for active fixation of the proximal graft.
The main body is available in diameters that range from 22 to 36 mm and lengths that range from 82 to 149 mm [12]. The iliac limbs are available in 8 and 24 mm diameters in lengths ranging from 3.7 to 12.4 cm. The delivery sheath for bifurcated grafts is between 18 and 20 French (6.0 to 7.67 mm) depending upon the size of the graft, and the sheaths for other components range from 14 to 16 French (3.67 to 5.33 mm).
The safety and efficacy of the Zenith abdominal endograft was evaluated in a comparison study involving 352 patients in four study groups: an open surgical control group, a standard-risk (SR) group, a high-risk group, and a roll-in group [13]. Eighty control patients were enrolled with the intent of comparing them with the standard repair endovascular group. The technical success rate for endovascular repair was 99.7 percent. Perioperative (30-day) morbidity (cardiac, pulmonary, renal) was significantly decreased compared with the control group. Endovascular repair was also associated with fewer transfusion requirements, diminished blood loss, shorter length of hospital and intensive care unit stay, and quicker return to daily activities. Perioperative (30-day) mortality was significantly lower in the endovascular repair group (0.5 versus 2.5 percent) compared with the open surgical group. At one year of follow-up, all-cause mortality was not significantly different between the groups (3.5 percent in the standard risk endovascular repair group versus 3.8 percent in the control group). There were no significant differences in all-cause mortality or aneurysm-related death between the standard risk endovascular group and the control group on Kaplan-Meier analysis.
There were no immediate conversions reported, but three late conversions were performed: one for endoleak, one for a rapidly expanding supraceliac pseudoaneurysm, and one for rupture at 222 days postoperatively. The need for reintervention was significantly higher (11 versus 2.5 percent) for the standard risk endograft group compared with the control group at one year follow-up. The incidence of endoleak (mostly Type II) was 7.4 percent at 12 months and 5.4 percent at 24 months. Migration was not seen in any patient after 12 months. At two years follow-up, the majority of the aneurysms demonstrated shrinkage of the aneurysm sac.

Excluder® — The Excluder® device (table 1) is a self-expanding modular bifurcated two-component graft made of expanded polytetrafluoroethylene (ePTFE) material bonded to a nitinol exoskeleton and covered with a reinforcing sleeve of ePTFE/fluorinated ethylene propylene (FEP) composite film. The proximal graft and ipsilateral limb have scalloped flares lined with graft material. The proximal graft and distal limbs have an ePTFE sealing cuff to improve apposition to the arterial wall.
The main body graft is available in diameters ranging from 23 to 31 mm with an ipsilateral limb measuring 12 or 14.5 mm [14]. The length of the body of the graft ranges from 12 to 18 cm. The contralateral limb is available in diameters ranging from 12 to 20 mm and lengths from 9.5 to 13.5 cm. The main device is delivered in an 18 or 20 French (6 to 6.67 mm) sheath. The device employs a unique delivery system that relies upon a pull-cord similar to a dog food bag. Once the device is positioned, the deployment line unlaces from the middle of the device toward both ends.
The safety and efficacy of the Excluder® graft was evaluated in a prospective nonrandomized trial that enrolled 334 patients (235 endovascular and 99 open surgical control patients) in 19 different centers. Compared with the control group, the Excluder® group had less blood loss, shorter length of hospital stay, and decreased length of recovery. At one-year and two-year follow-up, the Excluder® group had a significantly lower incidence of major complications (33 versus 67 percent). There were no significant differences between the groups in survival rate at two-year follow-up. In the Excluder® group, the incidence of aneurysm-related death was 2.6 percent, but there were no late aneurysm ruptures at four-year follow-up .
Aneurysm sac enlargement, defined as ≥5 mm change from baseline size, occurred in 3 and 36 percent of patients at one and five years, respectively, after graft placement in the Excluder® 98-03 Pivotal Trial, the majority occurring without any apparent endoleaks . This phenomenon led the company to release an updated version of the Excluder® device in July 2004. The new device incorporated the additional low-permeability layer (FEP) to reduce exudation of fluid flow across the graft material. Following these improvements, minimal aneurysm sac expansion and significant aneurysm sac regression have been found after endovascular repair of abdominal aortic aneurysms using the new Excluder® device at one year , and with longer follow-up at five years.
AFX and Powerlink® — The AFX and IntuiTrak Powerlink® systems  are modular bifurcated grafts composed of expanded polytetrafluoroethylene (ePTFE) supported by a self-expanding internal cobalt-chromium alloy skeleton. The main body of the endograft has symmetric iliac limbs. The proximal graft has a bare stent for active fixation and the bifurcation of the graft rests on the aortic bifurcation for anatomic distal fixation. The AFX graft has replaced the initial Powerlink® graft design, and is distinguished by a lower profile and a multilayered STRATA ePTFE graft material that is intended to provide greater strength and better conformability.
The main device is available in diameters ranging from 22 to 28 mm in lengths ranging from 6 to 10 cm with limbs measuring 13 or 16 mm in diameter and lengths from 3 to 5.5 cm [20]. The limb extensions range from 16 to 20 mm in diameter in lengths from 5.5 to 8.8 cm. The main device is delivered in a 21 French (7 mm) sheath and the contralateral limb is delivered through a 17 or 19 French (5.67, 6.33 mm) sheath.
The safety and efficacy of the Powerlink® graft was evaluated in a multicenter, nonrandomized comparison study conducted at 15 sites that enrolled 192 patients who received the graft and 66 open surgical patients between 2000 and 2003 . Technical success was achieved in 97.9 percent of patients. Patients treated with the Powerlink® stent-graft had significantly decreased blood loss (341 versus 1582 mL), operative time (133 versus 222 minutes), length of intensive care unit stay (0.78 versus 4.1 days) and hospital stay (3.3 versus 9.5 days) compared with the open control group. There were no significant differences in mortality rates. There were no reported graft-related endoleaks (Type I, III, or IV) at four years of follow-up, and also no reports of ruptures, graft fabric defects, or wire fractures. Aneurysm sac regression was noted in 83 percent of patients. The six-year follow-up results also reported no stent fractures, graft disruptions, or aneurysm ruptures [22]. No differences in all-cause morbidity were found between the Powerlink® and open surgical groups.

Talent™ — The Talent™ abdominal stent-graft (table 1) is a modular, bifurcated graft that is composed of a woven polyester fabric with an external self-expanding support structure of M-shaped nitinol stents. The proximal graft has an uncovered stent for aortic fixation.
The main device is available in diameters ranging from 22 to 36 mm with limbs measuring 8 to 24 mm in diameter [23]. The diameter of the limb extensions ranges from 8 to 22 mm with lengths from 7.5 to 14 cm. The main device is delivered in a 22 French (7.33 mm) sheath and the contralateral limb is delivered through an 18 or 20 French (6, 6.67 mm) sheath.
The safety and efficacy of the Talent™ device was established in phase I and II clinical studies [24,25]. The success rate in the phase II study of 127 high-risk patients was 94 percent. Perioperative (30-day) mortality was 1.5 percent. The phase II low-risk trial included a first-generation and a second-generation Talent™ stent-graft. Deployment success rates were 97 to 99 percent. Perioperative mortality was 2 percent in the phase II low-risk study, and the mortality and adverse-event rates for the second-generation device were 0 and 1.8 percent, respectively.
The long-term results for Talent™ grafts placed between the years 2000 and 2007 have been reported [26]. Perioperative mortality (30-day) for the entire Talent™ group was 1.1 percent (4 of 365 patients). Primary clinical success rates were 98 percent at one year, 93 percent at two years, 88 percent at three years, 79 percent at four years, 64 percent at five years, 51 percent at six years, and 48 percent at seven years using Kaplan-Meier estimates. Secondary interventions were performed in 20 percent of patients, and included 10 conversions for failed endografts (10/365). Follow-up to 84 months was available for 24 patients. During follow-up, 122 patients (33 percent) died; in nine, death was related to the abdominal aortic aneurysm (AAA) (including 30-day mortality). Life-table analysis identified an annual risk for AAA-related reintervention of 6 percent, annual risk for conversion to open repair of 1.1 percent, annual risk for total mortality of 8.9 percent, and annual risk for AAA-related mortality of 0.8 percent. The results of this trial indicate a high initial technical success rate, with an acceptable annual risk for conversion and AAA-related mortality. However, a substantial number of endovascular re-interventions were needed during long-term follow-up.
Endurant® — The Endurant® endograft (table 1) is a modular, bifurcated device composed of a multifilament polyester fabric with an external self-expanding support structure of M-shaped electro-polished nitinol stents. Proximally, it has a suprarenal nitinol stent with anchoring pins for suprarenal fixation. The graft design is intended to treat aneurysms with more challenging anatomy (eg, neck angulation).
The main device is available in diameters that range from 23 to 36 mm for the main body and 13 to 20 mm for the ipsilateral limb, and in lengths of 12.4, 14.5 and 16.6 cm [27]. The contralateral iliac stent component ranges from 10 to 28 mm in diameter with 8.2, 9.3 and 12.4 cm lengths. The internal diameter of the delivery sheath for the bifurcated grafts is 18 or 20 French (6.0, 6.67 mm) and the sheaths for other components range from 14 to 16 French (4.67 to 5.33 mm).
A single arm, multicenter trial evaluating the safety and performance of the Endurant® graft was conducted at 26 sites in the United States and enrolled 150 patients between April 2008 and May 2009 [28]. The technical success rate was 99.3 percent. One failure was due to inability to cannulate the contralateral gate and one patient ruptured during the procedure, but was still treated successfully. The perioperative mortality (30-day) rate was zero and the incidence of major adverse events was 4 percent. At one-year follow-up there were no migrations, ruptures, open conversions or graft-related endoleaks (type I or III). Ten aneurysm-related re-interventions were performed during the first year of follow-up, mostly for graft limb thrombosis or stenosis (five) or type II endoleak (two). Aneurysm sac diameter decreased >5 mm at one year in 47 percent of patients and remained stable in 53 percent. No instances of sac growth were reported. Late deaths occurred in 4.7 percent of patients but were not related to the aneurysm repair.
A European trial enrolled 80 patients between November 2007 and August 2008, 71 of whom had moderate infrarenal aortic neck angulation and nine with a high degree of angulation (60° to 75°) [29]. The device was successfully delivered and deployed in all cases. At one-year follow-up, all-cause mortality was 5 percent, with potentially one device-related death. Serious adverse events were comparable between the high and moderate angulation groups. There were no device migrations, stent fractures, aortic ruptures, or conversions to open repair. Maximal aneurysm diameter decreased >5 mm in 43 percent of cases. Three secondary endovascular procedures were performed for outflow vessel stenosis, graft limb occlusion, and iliac extension, resulting in a secondary patency rate of 100 percent. No re-interventions were required in the high angulation group.
Withdrawn and investigational devices — Several devices introduced for endovascular repair of abdominal aortic aneurysm (AAA) have been withdrawn from the market, were not used clinically, or are still awaiting approval after the initial trial data. Their status is briefly reviewed.
The Ancure graft was a flexible, unsupported fabric graft with active fixation at the ends of the graft using wire hooks that penetrated the aortic wall. The graft was approved for use in the United States in 1999 but was recalled in 2001. Production of the graft was suspended in 2003 due to device malfunctions and adverse events associated with device deployment.
Other devices that are no longer available include the Lifepath device, which had problems with stent fractures, and the Fortron and Quantum grafts which were re-designed into the Incraft™ device.

The Aorfix™ AAA bifurcated endograft is a bifurcated woven polyester graft supported by a nitinol skeleton. Active fixation is provided by proximal nitinol hooks. The graft is intended to treat angulated aortic necks for up to 90 degrees and tortuous iliac anatomy. The proximal portion of the main graft body is fish-mouthed (rather than circular) in shape, and when positioned properly, the surface area of the potentially achievable seal-zone is increased in the anterior-to-posterior dimension. Because of this feature, the distance from the superior mesenteric artery to the lowest renal artery needs to be at least 15 mm in length to prevent inadvertent coverage of the superior mesenteric artery orifice during graft deployment.
The Aorfix™ graft is currently approved for clinical use and available in Europe, and is awaiting approval in the United States. Short-term and mid-term data from European trials have confirmed the safety of the device and its suitability for treating hostile aorto-iliac anatomy [30]. The PYTHAGORAS trial is currently recruiting participants .
Emerging technologies are focusing on improving the delivery profile and are awaiting approval or further testing in clinical trials. These include the 14-French (4.7 mm) Ovation endograft system, the 14-French (4.7 mm) Incraft™ AAA stent graft system, and the 18-French (6 mm) Zenith LP device.
Advanced graft designs that are investigational are discussed below.
 Several trials have compared endovascular aneurysm repair using a variety of endografts to open surgical repair for the treatment of infrarenal AAA

Characteristics of abdominal endovascular devices

Endograft	Materials graft/support	Suprarenal fixation	Active proximal fixation/hooks	Native aortic neck diameter (range in mm)	Native iliac diameter (range in mm)	Maximum bifurcated main body device/introducer sheath diameter (French, OD*)	Potential advantages
AneuRx® (Medtronic)	Polyester/nitinol	No	No	20 to 26	8 to 22	21	Hydrophilic delivery system
Endurant® (Medtronic)	Polyester/ electropolished nitinol	Yes	Yes	19 to 32	8 to 25	20	Indications include short (10 mm) aortic neck, angulated neck
Powerlink® (Endologix)	PTFE/cobalt chromium alloy	Yes	No	18 to 32	10 to 23	17	Anatomic fixation at iliac bifurcation, low profile
Excluder® (Gore)	PTFE/nitinol	No	Yes	19 to 29	10 to 18.5	20	C3 delivery system, ability to recapture and reposition body, delivery sheath with hemostatic seal
Talent® (Medtronic)	Polyester/nitinol	Yes	No	18 to 32	8 to 22	24	Indication for short (10 mm) aortic neck, angulated necks
Zenith® (Cook Medical)	Polyester/stainless steel	Yes	Yes	18 to 32	8 to 20	26	Spiral Z flexible limbs

PTFE: polytetrafluoroethylene.
* OD: outer diameter.