Fenestration in Endovascular Grafts for Aortic Aneurysm Repair: New Horizons for Preserving Blood Flow in Branch Vessels

Thoracic stent graft with distal fenestration for the superior mesenteric artery for treatment of thoracic aortic aneurysm

An 86-year-old man with a 75-mm TAA that terminated just above the celiac artery was treated with a customized Zenith stent graft that had a distal fenestration for the superior mesenteric artery (SMA). Because angiography demonstrated a type IB endoleak, an additional extension stent graft was deployed, and coil embolization of the aneurysmal sac was performed. Three months later, there was no endoleak and good visceral blood flow. Placement of a fenestrated thoracic stent graft with a scallop-like fenestration for the SMA is a promising procedure for the treatment of TAAs with a short distal neck.

Balloon-assisted coil embolization of the celiac trunk before endovascular aortic repair of thoracoabdominal aortic aneurysm

PURPOSE

Celiac trunk coil embolization before thoracic endovascular aneurysm repair (TEVAR) of a thoracoabdominal aortic aneurysm involving the celiac trunk can prevent type II endoleaks. One disadvantage of conventional coil embolization is the risk of coil displacement. We performed coil embolization under balloon occlusion of the celiac trunk to address this issue.

MATERIALS AND METHODS

Between December 2008 and January 2011, 5 patients (3 men and 2 women, mean age 76 years) were included in this study. For all patients, after confirming the collateral blood flow from the superior mesenteric artery via the pancreaticoduodenal arcades by using the balloon occlusion test, celiac trunk coil embolization proceeded under balloon occlusion of the proximal part of the celiac trunk.

RESULTS

Balloon-assisted coil embolization of the celiac trunk was completed for all patients without any complications. All coils were deployed as planned in the short segment of the celiac trunk without displacement. Coil migration, ischemic complications, and endoleaks via the celiac trunk did not arise in any of the patients over a follow-up period of 77-637 (mean 258) days.

CONCLUSIONS

Balloon-assisted coil embolization of the celiac trunk before TEVAR could be a feasible treatment option for suitable patients.

Abdominal aortic aneurysm: Treatment options, image visualizations and follow-up procedures

Abdominal aortic aneurysm is a common vascular disease that affects elderly population. Open surgical repair is regarded as the gold standard technique for treatment of abdominal aortic aneurysm, however, endovascular aneurysm repair has rapidly expanded since its first introduction in 1990s. As a less invasive technique, endovascular aneurysm repair has been confirmed to be an effective alternative to open surgical repair, especially in patients with co-morbid conditions. Computed tomography (CT) angiography is currently the preferred imaging modality for both preoperative planning and post-operative follow-up. 2D CT images are complemented by a number of 3D reconstructions which enhance the diagnostic applications of CT angiography in both planning and follow-up of endovascular repair. CT has the disadvantage of high cummulative radiation dose, of particular concern in younger patients, since patients require regular imaging follow-ups after endovascular repair, thus, exposing patients to repeated radiation exposure for life. There is a trend to change from CT to ultrasound surveillance of endovascular aneurysm repair. Medical image visualizations demonstrate excellent morphological assessment of aneurysm and stent-grafts, but fail to provide hemodynamic changes caused by the complex stent-graft device that is implanted into the aorta. This article reviews the treatment options of abdominal aortic aneurysm, various image visualization tools, and follow-up procedures with use of different modalities including both imaging and computational fluid dynamics methods. Future directions to improve treatment outcomes in the follow-up of endovascular aneurysm repair are outlined.

Endovascular device design in the future: transformation from trial and error to computational design

Endovascular devices have been designed by trial and error, with bench and animal testing followed by human clinical trials to determine whether the devices are safe and effective. Despite remarkable advances over the past 15 years, there are persistent concerns regarding the long-term durability of endovascular devices. This may be due to deficiencies in device design, which has lagged behind other industries in adopting computational methods that are now routinely used to design, develop, and test new aircraft and automobiles. Similar computational design and failure mode simulations that evaluate performance under stress conditions have not been widely applied in the development of endovascular devices. Advances in medical imaging and computational modeling now allow simulation of physiological conditions in patient-specific 3-dimensional vascular models, which can provide a framework to design and test the next generation of endovascular devices. This modeling will allow the prospective design of devices that can withstand the force variations in the cardiovascular system that occur during bending, coughing, and varying degrees of exercise, as well as the extremes encountered during sudden impact in contact sports. Utilization of computational design methodology that takes into consideration the physiology of the cardiovascular system will improve future endovascular devices so that they are safer and more effective and durable.

Helical CT angiography of fenestrated stent grafting of abdominal aortic aneurysms

Fenestrated stent grafts have been developed to treat patients with abdominal aortic aneurysms (AAA) associated with complicated aneurysm necks, such as short necks, severe angulated or poor quality necks (presence of calcification or thrombus). The technique is performed by creating an opening in the graft material so that the stent graft can be placed above the renal and other visceral branches without compromising blood perfusion to these vessels. In most situations, a supporting stent is inserted into the fenestrated vessel to provide fixation of the fenestrated vessel against stent grafts, as well as to preserve patency of the vessel. Helical CT angiography (CTA) is the preferred imaging modality in both pre-operative planning and post-procedural follow-up of fenestrated repair of AAA. The main concerns of fenestrated stent grafting lie in the following two aspects: patency of the fenestrated vessels and position of the fenestrated stents in relation to the artery branches. In this article, the author presents the clinical applications of 2D and 3D visualizations in the follow-up of patients with AAA treated with fenestrated stent grafts, with the aim of providing useful information to readers and increasing their knowledge of an increasingly used technique, fenestrated stent grafting in the treatment of AAA.

Multislice CT angiography in the follow-up of fenestrated endovascular grafts: effect of slice thickness on 2D and 3D visualization of the fenestration stents

PURPOSE

To investigate the effect of multislice computed tomography (CT) protocols on the visualization of target vessel stents in patients with abdominal aortic aneurysm (AAA) treated with fenestrated endovascular grafts.

METHODS

Twenty-one patients (19 men; mean age 75 years, range 63-86) undergoing fenestrated endovascular repair of AAA were retrospectively studied. Multislice CT angiography was performed with several protocols, and the section thicknesses used in each were compared to identify any relationship between slice thickness and target vessel stents visualized on 2-dimensional (2D) axial, multiplanar reformatted (MPR), and 3-dimensional (3D) virtual intravascular endoscopy (VIE) images. Image quality was assessed based on the degree of artifacts and their effect on the ability to visualize the configuration, intra-aortic location, and intraluminal appearance of the target vessel stents and measure their protrusion into the aortic lumen.

RESULTS

There were 7 different multislice CT scanning protocols employed in the 21 patients (25 datasets, with 2 sets of follow-up images in 4 patients). The slice thicknesses and numbers (n) of studies included were 0.5 (n=3), 0.625 (n=6), 1.0 (n=1), 1.25 (n=9), 2.5 (n=3), 3.0 (n=1), and 5.0 mm (n=2). Of these CT protocols, images (especially 2D/3D reconstructions) acquired at 2.5, 3.0, and 5.0 mm were significantly compromised by interference from artifacts. Images acquired with a slice thickness of 1.0 or 1.25 mm were scored equal to or lower than those acquired with a submillimeter section thickness (0.5 or 0.625 mm), with minor degrees of artifacts resulting in acceptable image quality.

CONCLUSION

Visualization of the target vessel stents depends on the appropriate selection of multislice CT scanning protocols. Our results showed that studies performed with a slice thickness of 1.0 or 1.25 mm produced similar image quality to those with a thickness of 0.5 or 0.625 mm. Submillimeter slices are not recommended in imaging patients treated with fenestrated stent-grafts, as they did not add additional information to the visualization.

CT virtual intravascular endoscopy in the visualization of fenestrated stent-grafts

PURPOSE

To report the diagnostic value of computed tomographic (CT) virtual intravascular endoscopy (VIE) in the assessment of patients with abdominal aortic aneurysm (AAA) treated with fenestrated endovascular grafts.

METHODS

Eight patients (7 men; mean age 76 years, range 70-82) with AAAs unsuitable for open surgery or conventional endovascular repair had fenestrated endovascular grafts implanted. Both pre- and post-fenestration multislice CT data were used to generate VIE images of the visceral artery ostia and the side branch fenestrated stents. CT VIE images were compared with conventional 2-dimensional (2D) axial CT and multiplanar reformatted (MPR) images for the ability to visualize the intraluminal appearance of stents, as well as to measure the length of stents that protruded into the aortic lumen.

RESULTS

Various fenestrations were deployed in 27 aortic branches. Scalloped and large fenestrations were implanted in 6 side branch ostia, respectively, and small fenestrations in 15 renal artery ostia. Fewer than half of the stents (37%) were found to be circular on VIE images, while the remaining stents were flared to varying extents at the inferior portion. The majority (96%) of stents protruded into the lumen up to 7.0 mm. Although the configuration of the side branch ostia changed to a variable extent, no significant difference was apparent between the diameters of branch ostia before and after fenestration (p>0.05).

CONCLUSION

Our preliminary study shows that VIE proved superior to conventional 2D or MPR images in visualizing the final configuration of the fenestrated vessels and was comparable to the other techniques in measuring stent protrusion into the aortic lumen. VIE could be a valuable technique to identify any suspected abnormalities associated with fenestrated endovascular grafts by demonstrating the final intraluminal configuration of the stents in the fenestrated vessels.

Fenestrated and Branched Stent-Grafts for Thoracoabdominal, Pararenal and Juxtarenal Aortic Aneurysm Repair

The neck of a juxtarenal aneurysm is often too short for stable hemostatic stent-graft implantation. Fenestrations (holes) in the stent-graft permit implantation at a more favorable level by providing a route for flow to the renal arteries. In cases of pararenal and thoracoabdominal aortic aneurysm, the aorta around the renal and visceral arteries is too dilated for hemostatic contact with the wall of the stent-graft. There is a gap, which must be bridged by a branch of the stent-graft. In a fenestrated branched stent-graft, balloon-expanded covered stents run transaxially from fenestrations in the wall of the primary stent-graft to the branch arteries (renal or visceral). In a cuffed branched stent-graft, self-expanding covered stents curve outward from axially oriented cuffs on the primary stent-graft to the branch arteries. The two approaches share the same basic modular pattern of in situ construction, but differences between them have important consequences for the long-term efficacy and stability of the resulting branched stent-graft. Unibody branched stent-grafts suffer from an irreducible complexity of stent-graft manufacture and insertion technique, which has limited their application to a small number of cases. Most published reports contain a mixture of fenestrated and branched techniques, focus on short-term results, and provide little information on the relative merits of each approach. However, the enormous potential advantages of endovascular repair of visceral segment aneurysms and promising short-term results continue to drive the dissemination of branched stent-graft technology.

Funnel technique for first-line endovascular treatment of an abdominal aortic aneurysm with an ectatic proximal neck

PURPOSE

To describe a novel endovascular technique for proximal stent-graft fixation in an abdominal aortic aneurysm (AAA) with an ectatic aortic neck.

CASE REPORT

An 84-year-old man with multiple comorbidities and an asymptomatic 7-cm infrarenal AAA with a 38-mm aortic neck diameter was treated with a 3-component Talent-LPS stent-graft system. After the left internal iliac artery was embolized with coils, a 34 x 16 x 170-mm Talent bifurcated stent-graft was placed in the lower part of the AAA. A 44-mm-diameter, 90-mm-long free-flow thoracic tube endograft (6-mm oversizing) was delivered to the proximal neck through the bifurcated device and deployed with at least 30 mm of overlap, leaving more than 40 mm extending into the infrarenal aorta to ensure expansion to its nominal diameter as well as an adequate seal. An iliac extension was deployed into the left external iliac artery, and 2 sequential iliac extensions were inserted from the bifurcated stent-graft limb to the right common iliac artery in a bell-bottom configuration. Serial computed tomographic angiograms at up to 18 months have documented the intact 3-component stent-graft, with no endoleak or migration and no increase in aneurysm sac diameter.

CONCLUSION

This case illustrates the feasibility of placing a straight thoracic endograft as a proximal extension of a bifurcated aortic endograft into a dilated proximal aortic neck. This endograft configuration appears secure and effective, with no type I endoleak or migration over a midterm follow-up.

Short to Midterm Outcomes of Fenestrated Endovascular Grafts in the Treatment of Abdominal Aortic Aneurysms:A Systematic Review

PURPOSE

To perform a systematic review of the short to midterm outcomes of fenestrated endovascular grafts in patients with abdominal aortic aneurysms (AAA).

METHODS

A search of PubMed and Medline databases for English-language literature was performed to find studies published between 1999 and 2006. Studies investigating the short to midterm results of fenestrated endovascular grafts for AAA were analyzed for clinical outcomes and postprocedural complications.

RESULTS

Nineteen studies involving fenestrated endovascular grafting were retrieved, and 6 of them met criteria for inclusion in the analysis. The remaining studies were excluded because they dealt with technical or case reports or cumulative addition of previous cases. Pooled estimates (95% confidence interval) of postprocedural complications were 1.1% (0.4%-2.7%) for 30-day mortality; 8.3% (2.9%-13.6%) for late mortality; 97% (92%-100%) and 90% (85%-95%) for perfusion of fenestrated vessels at perioperative and late follow-up, respectively; 13.3% (4.1%-22.5%) for postprocedural renal dysfunction; and 11.2% (3.2%-22.5%) and 9.4% (2.6%-16.3%) for early and late endoleak, respectively. There was correlation between preoperative renal insufficiency and postprocedural renal dysfunction, although this was not a statistically significant difference (p=0.2).

CONCLUSION

Our systematic review showed that fenestrated endovascular grafting provides an alternative technique to treat patients with complex aneurysm necks, achieving lower mortality than open repair under comparable conditions. Preoperative renal impairment is a strong indicator of postoperative renal dysfunction. Long-term stability and patency of the fenestrated vessels deserves to be validated.

Clinical Experience with a Customized Fenestrated Endograft for Juxtarenal Abdominal Aortic Aneurysm Repair

Despite the numerous stent-graft devices available, unsuitable anatomy is still the greatest exclusion criterion for endovascular abdominal aortic aneurysm (AAA) repair (EVAR). The present report describes an on-site preprocedural customization of a conventional Zenith stent-graft device just before the endovascular procedure that includes the creation of fenestrations and scallops as necessary for the patient's anatomy. Three patients with difficult anatomy in whom conventional AAA repair posed a high degree of risk were treated with customization of the stent-graft device to fit disparate renal arteries. A single fenestration for the left renal artery was made in two cases, and a single scallop was made in the other case to accommodate the superior mesenteric artery. Gold beads were used to mark the location of the fenestration and scallop. The three cases were successfully performed without perceptible endoleaks in the follow-up period, which ranged from 4 to 14 months. No procedure-related complications were detected; however, pneumonia developed in one patient 3 weeks after EVAR. The initial results with this technique are encouraging, and the role of EVAR can be significantly increased with the use of this customization technique when the interventionalist does not have access to the commercially available devices or when the waiting time is too prolonged to accommodate the patient's clinical situation.

Aortic Aneurysm, Thoracoabdominal Aneurysm, Juxtarenal Aneurysm, Fenestrated Endografts, Branched Endografts, and Endovascular Aneurysm Repair

The development of endovascular devices to treat aneurysms that abut or involve the visceral vessels has occurred in an effort to reduce the significant procedural morbidity and mortality associated with conventional repair. To accomplish this, three systems have been trialed. The first technique was developed to treat juxtarenal aneurysms and involves the placement of customized fenestrations strategically placed within the fabric of the graft. These are aligned with the ostia of the visceral vessels incorporated by the repair and supplemented by the placement of a balloon expandable stent. In a similar fashion, aneurysms that involve the visceral vessels can be treated with a fenestrated graft where the fenestration is reinforced with a nitinol ring. This is then mated with a balloon-expandable stentgraft, allowing the devices to seal at the level of the nitinol ring. An alternative means of incorporating the visceral vessels is to use directional branches where one or more additional limbs (typically 8 mm) are anastomosed to the aortic graft, through which access into the visceral vessel is attained. Mating stentgrafts for the later design can be of a self-expanding or balloon expandable nature. The experience with fenestrated devices is mature and associated with a low perioperative mortality (<2%) without many long-term complications. The treatment of thoracoabdominal aneurysms with branches has provided us with optimism regarding the technique, but results are only short term in nature. Further device development is ongoing and dissemination of this technology is now occurring in Europe, Australia and Canada.

FIFTY YEARS OF VASCULAR SURGERY IN AUSTRALIA AND NEW ZEALAND

Over the 50 years that vascular surgery has been practised in Australia and New Zealand there have been major advances and refinements of surgical techniques, particularly with the advent of endovascular surgery, spurred on especially with the introduction of endovascular aortic aneurysm stent grafting. At the same time, there has been a revolution in medical imaging, with the introduction of ultrasound, computed tomography scanning and magnetic resonance scanning. Vascular surgery in Australia and New Zealand was initially an interest of either general or cardiothoracic surgeons, but was recognized as a subspecialty of general surgery with the formation of the Section of Vascular Surgery within the Division of General Surgery of the Royal Australasian College of Surgeons in 1972. In 1981, a 2-year training programme in vascular surgery was established and in 1983 an Australian and New Zealand Chapter of the International Society for Cardiovascular Surgery was formed. In 1995, vascular surgery was recognized as a specialty in its own right with the formation of the Division of Vascular Surgery within the College. There has been a separate examination for Fellowship of the Royal Australasian College of Surgeons (Vascular) since 1997. In 2001, the Chapter changed its name to The Australian and New Zealand Society for Vascular Surgery and in 2002 it amalgamated with and took over the functions of the Division of Vascular Surgery, which was formally dissolved.

A Laparoscopic Access Technique for Endovascular Procedures:Surgeon Training in an Animal Model

PURPOSE

To present a laparoscopic technique for placing a transperitoneal conduit in the common iliac artery (CIA) or distal aorta to circumvent stenosed or occluded iliac systems and to assess the success of this laparoscopic access in a live animal model.

TECHNIQUE

A porcine model was used owing to similarities in anatomy and size of the pig aorta to the human common iliac artery (CIA). Ethical approval was obtained, and the technique was developed in 8 animals under general anesthesia. A curved hollow needle, a partially stented Dacron conduit, an airtight laparoscopic port and a sealing sheath and valve were developed specifically for percutaneous access through the abdominal wall. A transperitoneal approach was used to the distal aorta. Cannulation by the curved hollow needle via the new port was under direct vision. The conduit was inserted over a guidewire after needle removal and deployed under fluoroscopy. The distal end of the conduit was secured by the sealing sheath and valve, enabling wire and catheter exchange thereafter. A 2-day educational workshop was held for 12 vascular surgeons with a range of laparoscopic experience. After learning the technique on a simulator model, they worked in pairs, alternating surgeon/assistant roles to insert conduits into 12 animals under general anesthesia. Laparoscopic cannulation in all 12 animals was successful. There was no bleeding around the conduit at the aortic arteriotomy. All animals were euthanized after confirmation of conduit patency by back-bleeding.

CONCLUSION

This novel technique bridges the gap between laparoscopic and endovascular techniques in striving for minimally invasive solutions to the treatment of vascular disease. Adaptation to human beings is currently underway and will mean increasing the applicability of endovascular solutions to those patients in whom it would otherwise be denied. The technique would appear not to require specialist laparoscopic skills.

Outcomes of Fenestrated Endografts in the Treatment of Abdominal Aortic Aneurysm in Western Australia (1997–2004)

PURPOSE

To describe a 7-year experience with abdominal aortic aneurysm (AAA) repair using fenestrated Zenith endovascular endografts.

METHODS

Six endovascular surgeons from 7 medical centers in Perth, Western Australia, contributed data to this retrospective study of 58 AAA patients (51 men; mean age 75.5+/-8.5 years, range 60-94) treated with fenestrated endografts. Fenestrations were applied to 116 target vessels; more than half of patients had >/=2 target vessels. The results were based on satisfactory deployment of the stent-graft and fenestrations (technical success), technical success and no complications (procedural success), and aneurysm exclusion with no endoleak, rupture, unresolved complications, or dialysis (treatment success).

RESULTS

Technical success was 82.8% for patients (90.5% for target vessels), procedural success was 74.1%, and treatment success was 94.8%. There were no cases of conversion or rupture. The 30-day mortality rate was 3.4% (n=2). Over a mean follow-up of 1.4+/-1.2 years, 10 (17.2%) patients experienced loss of a target vessel (9.5% of target vessels). Factors associated with target vessel loss were no stent, >60 degrees neck angulation, multiple renal vessels, and vessel diameter </=4 mm. Four (6.9%) patients developed renal impairment, but none required dialysis. Fourteen (24.1%) patients had a secondary intervention. Unresolved endoleaks persisted in 1 (1.7%) patient.

CONCLUSION

Fenestrated endografts extend the treatment options for infrarenal AAAs with necks unsuitable for standard endovascular repair. This early data show a trend toward higher mortality of selected patients with fenestrated endografts than for standard stent-graft repair, but the mortality rate is comparable to open repair. Target vessel occlusion predominantly results from pre-existing disease or the lack of a stent. The lessons learned from this experience contributed toward guidelines for users of fenestrated endografts.

Current Status of Branched Stent-Graft Technology in Treatment of Thoracoabdominal Aneurysms

Endovascular aortic aneurysm repair has been established as an alternative to open surgical reconstruction in appropriately selected patients. Until recently, this approach has been limited to aneurysms not involving critical aortic branches due to the complex nature of designing devices that would preserve important end-organ flow. This article reviews the current status of endovascular approaches to aneurysms involving the thoracoabdominal aorta. The evolution of fenestrated devices and further developments, including reinforced fenestrated branched grafts and directional branches for more complex aneurysms are discussed.

Movement and Dislocation of Modular Stent-Grafts Due to Pulsatile Flow and the Pressure Difference Between the Stent-Graft and the Aneurysm Sac

PURPOSE

To investigate the stability and movement of modular aortic stent-grafts subjected to oscillating forces from pulsatile blood flow, with particular reference to the thoracic aorta.

METHODS

Analytical mathematical modeling was used to understand the forces on modular grafts. In a benchtop experiment, a transparent acrylic box was filled with water to mimic an aneurysm. Two stent-grafts were placed inside the box in a nested, arched configuration where one component was partly inside the other. A pump produced a pulsatile approximately 5-L/min flow of water through the stent-grafts at a mean inlet pressure of approximately 100 mmHg (approximately 13,330 Pa), with systolic and diastolic pressures of approximately 130 and approximately 80 mmHg, respectively (pulse pressure 50 mmHg). The movement of the 2 modular stent-grafts was observed.

RESULTS

The curved stent-graft system oscillated transversely when there was zero mean pressure difference between the stent-graft and the aneurysm. As the mean pressure difference was increased, this transverse graft movement was damped and then disappeared. A relatively large pressure difference caused the stent-graft to inflate and become sturdier. In terms of stability, the analytical mathematical model for a 30-mm-diameter Zenith modular stent-graft curved through 90 degrees (with the ends of the graft fixed in place) showed that the modular components will separate at a pressure difference of 0 mmHg for 1 stent segment overlap (20 mm) and at an average 59 mmHg pressure difference for 2 stent overlaps, but the device would not separate at a pressure difference of 90 mmHg for 3 stent overlaps.

CONCLUSION

Transverse cyclic movement of the curved stent-graft system with pulsation indicates a pressurized sac. When the pressure difference is large and there is a blood-tight seal between the aneurysm and the stent-graft, then the transverse movement of the stent-graft is minimal, but the risk for modular separation is highest. Curved thoracic endografts are subject to forces that may cause migration or separation, the latter being more likely if the seal between the graft and the sac is blood tight, if the blood pressure is high, and if the diameter of the graft is small and the sac large. Operators should plan for maximum overlap of modular components when treating large or long thoracic aneurysms.

Fenestrated and Branched Endografts: Assessment of Proximal Aortic Neck Fixation

PURPOSE

To investigate proximal fixation characteristics of different aortic endograft designs: a suprarenally placed fenestrated endograft, a modular branched endograft, an infrarenal endograft with suprarenal bare stent fixation, and the gold standard, a conventional hand-sewn anastomosis.

METHODS

Ten human cadaveric aortas were obtained at autopsy and transected 20 mm below the renal arteries to mimic an infrarenal aneurysm neck. In random order, the infrarenal, fenestrated, and branched endografts were deployed into the aorta. Using a hydraulic material testing machine, longitudinal load was applied to the distal end of each endograft until migration occurred, thus defining the displacement force (DF). Subsequently, a hand-sewn infrarenal anastomosis was tested in a similar manner.

RESULTS

The median DF was 4.67 N (3.82-6.37) for the infrarenal endograft, 9.17 N (8.03- 10.81) for the fenestrated endograft, and 16.95 N (14.78-19.67) for the branched endograft. The differences in DF between the infrarenal and fenestrated endografts and between the fenestrated and branched designs were statistically significant (both p=0.005). The median force to dislodge the graft from the conventional anastomosis was 89.16 N (71.24-105.23).

CONCLUSIONS

Suprarenally placed endografts, especially with additional branch grafts, provide improved proximal fixation compared to an infrarenal endograft with suprarenal bare stent fixation. However, none of the tested endografts approached the optimal, time-proven fixation, the hand-sewn anastomosis.

Transrenal fixation of aortic stent-grafts: current status and future directions

Aortic stent-graft repair has been widely used in clinical practice for more than a decade, achieving satisfactory results compared to open surgical techniques. Transrenal fixation of stent-grafts is designed to obtain secure fixation of the proximal end of the stent-graft to avoid graft migration and to prevent type I endoleak. Unlike infrarenal deployment of stent-grafts, transrenal fixation takes advantage of the relative stability of the suprarenal aorta as a landing zone for the uncovered struts of the proximal stent. These transostial wires have sparked concern about the patency of the renal arteries, interference with renal blood flow, and effects on renal function. Although short to midterm results with suprarenal stent-grafts have not shown significant changes in renal function, long-term effects of this technique are still not fully understood. This review will explore the current status of transrenal fixation of aortic stent-grafts, potential risks of stent struts relative to the renal ostium, alternative methods to preserve blood flow to the renal arteries, and future directions or developments in stent-graft design to prevent myointimal proliferation around the stent struts.

Past, Present, and Future Endograft Devices

Since the original descriptions of endovascular grafts for treatment of aneurysms, a number of devices and approaches have been developed. The following is a discussion summarizing the number of devices which have been developed and used in patients, as well as chosen the directions of this technology. The diversity of approach from an engineering and materials point of view speaks of the fact that opportunity exists for continued development in the future.

Branched Stent-Grafts for Endovascular Repair of Aortic and Iliac Aneurysms

Endovascular technique, which gains access through indirect transarterial routes and isolates the aneurysm without interrupting flow, has particular advantages in aneurysms of the aortic arch and thoracoabdominal aorta. Yet progress has been slow. The necessary branched stent-grafts face several unique technical challenges. The simplest, most versatile approach involves assembling a modular stent-graft in situ from multiple parts. Techniques vary according to the presence or absence of an overlap zone, or cuff. The first cases of this type, reported over 4 years ago, had axially oriented cuffs. Recent efforts have seen the intercomponent attachment site reduced to a ring of Nitinol around a simple fenestration, with various hybrids of cuffed and fenestrated technique in between. Other advances, such as better sheaths, better covered stents, and commercial manufacture (Cook, Australia), have helped to extend the use of branched stent-grafts to a wider range of users and a wider range of aneurysms. Although their future role remains unclear, all these devices have gone beyond the proof of concept stage, and some, such as the bifurcated component for the endovascular iliac reconstruction, are ready to become standard parts of the endovascular.

Suprarenal stents and other advances in endovascular aneurysm repair

The history of endovascular aneurysm repair has already passed through its phases of "endoexuberance" and "endoscepticism" and there is now a balanced and broad understanding of the technology,its limits and advantages. Current endovascular technique and stent-graft design is the refinement of the accumulated endovascular experience til now. It is important to make note of these technological features incorporated in current stent-grafts and the clinical experience that precipitated their introduction as the technology progresses and new applications are proposed.

In Situ Stent-Graft Fenestration to Preserve the Left Subclavian Artery

PURPOSE

To report our first clinical application of a new technique for in situ fenestration of a thoracic stent-graft.

CASE REPORT

After completing a series of in vitro and in vivo experiments, in situ stent-graft fenestration was employed during endograft repair of a saccular thoracic aortic aneurysm in a 77-year-old woman. Because the stent-graft would have covered the left subclavian artery ostium, a modified Zenith TX1 thoracic stent-graft was deployed then fenestrated transluminally using a guidewire followed by serial cutting balloons, which created a fenestration over the LSA sufficiently large to accommodate a Jomed covered stent on an 8-mm balloon. Completion angiography showed exclusion of the aneurysm and brisk flow into the LSA. Following the procedure, the arm pressures were nearly equal. The 6-month CT scan showed no endoleak and a patent subclavian artery stent.

CONCLUSIONS

In situ graft fenestration to preserve the left subclavian artery after deliberate coverage during endovascular repair of a thoracic aortic aneurysm appears feasible in this initial clinical application. There are uncertainties regarding the long-term stability of the fabric tears that are an inherent part of this technique.