Are self-expanding stents superior to balloon-expanded in dilating aortas? An experimental study in pigs

Incidence of Renal Infarctions after Endovascular AAA Repair: Relationship to Infrarenal versus Suprarenal Fixation

Purpose:

To analyze the incidence and etiology of renal infarctions following endovascular abdominal aortic aneurysm (AAA) repair detected on computed tomography (CT) and determine any association with infrarenal versus suprarenal fixation.

Methods:

Between August 1994 and October 2001, 663 patients (604 men; mean age 68.5 years, range 40–98) underwent endovascular AAA repair with predominately bifurcated (505, 77%) stent-grafts. About a third (202, 30%) of the devices were deployed in a suprarenal position. Contrast-enhanced CT scans were performed on days 10, 90, and 365 after operation and then annually. Two radiologists blinded to procedural details compared the preoperative and postoperative scans to identify renal infarctions from inadvertent renal artery occlusion by the endograft. Only patients with inadvertent infarctions were analyzed relative to endograft fixation position and stent-graft type.

Results:

Mean follow-up was 37 months (range 0.1–75). Overall renal infarction rate was 11.9% (n=79); 23 (3.4%) patients suffered from limited, segmental infarction due to intentional covering of preoperatively diagnosed accessory renal arteries. Unintentional renal ischemia was identified in 56 (8.5%) patients. In this subgroup, 39 (19%) were observed in the 202 patients with suprarenal fixation versus 17 (3.7%) in the 461 stent-grafts positioned infrarenally (RR 3.35, 95% CI 2.20 to 5.04, p < 0.00001). There was a significant correlation between the incidence of infarction and the device type (14.3% for modular grafts versus 5.6% for unibody designs, p = 0.0002). Seventeen (2.6%) patients suffered from unilateral kidney loss, with dialysis required in 2 cases. Creatinine and urea showed no significant postoperative elevation in the overall patient population, but both levels were significantly (p < 0.02) elevated in patients with complete unilateral renal infarcts.

Conclusions:

Transrenal fixation of aortic endografts had a 3-fold higher risk for renal infarction in this large patient population. There is no significant difference for specific endografts, but modular designs were associated with a higher rate of renal infarction. The need to occlude preoperatively diagnosed accessory renal arteries with an endograft should be considered a contraindication for current available devices.

Dilatation of the Infrarenal Aneurysm Neck after Endovascular Exclusion of Abdominal Aortic Aneurysm

Purpose:

To determine the fate of the infrarenal aneurysm neck and suprarenal aorta after endovascular exclusion of abdominal aortic aneurysms (AAAs).

Methods:

Thirty-four patients underwent endovascular AAA repair between January 1994 and December 1995 using custom-made stent-grafts constructed from polyester graft material and modified self-expanding Gianturco Z-stents sutured to the graft orifices. Thirty-one patients were available for follow-up. Pre- and postimplantation diameters were measured using spiral computed tomography in the infrarenal aneurysm neck and the suprarenal aorta at the level of the superior mesenteric artery (SMA).

Results:

The mean follow-up time was 25 months. There was a significant increase of the diameter of the infrarenal aneurysm neck (+ 1.65 mm, p = 0.002), but not in the aorta at the level of the SMA (+ 0.52 mm, p = 0.100). There was no difference in the change in diameter in the infrarenal neck in the group with a stent adjacent to the level of measurement (n = 20) compared with the group without an adjacent stent (n = 11, p = 0.790). There was no correlation between preimplantation size of the infrarenal neck and its diameter change (r = 0.14, p = 0.488). There was no correlation (r = 0.10, p = 0.603) or association (chi-square test, p = 0.211) between aortic diameter change at the level of the SMA and the infrarenal neck.

Conclusions:

This investigation shows a significant dilatation of the infrarenal aneurysm neck, but not in the suprarenal aorta, after endovascular AAA repair with this device. The clinical significance of these findings is unclear. Whether such a dilatation in the infrarenal aneurysm neck may affect the long-term attachment of stent-grafts remains to be shown in the future.

Another late complication after endovascular aneurysm repair: aneurysmal degeneration at the iliac artery landing site

The purpose of this article is to describe a hitherto underreported late complication of infrarenal endovascular aneurysm repair (EVAR), namely type Ib endoleakage resulting from aneurysmal degeneration at the iliac artery landing site. In a prospectively recorded audit, between 1994 and 2007, 297 patients underwent EVAR. All cases that developed iliac artery aneurysm (IAA) were studied. Ten cases of IAA in seven patients (2.4% of the cohort) developed 5 to 9 years after EVAR. Eight of the 10 involved the lower landing site of the stent graft. Landing site diameter before EVAR was 12 mm (range 10-15 mm). Three IAAs presented as emergencies with rapidly expanding sacs and impending rupture. All cases underwent further endovascular intervention with no < 30-day mortality. Iliac artery landing site aneurysm formation after EVAR occurs uncommonly after 5 or more years. It should be regarded as an indication for intervention prior to type Ib endoleakage development. The need for lifelong surveillance is highlighted.

Atualização sobre endopróteses vasculares (stents): dos estudos experimentais à prática clínica

Atualmente, o tratamento das doenças vasculares periféricas é uma das áreas da medicina de maior expansão. O número de intervenções vasculares aumenta e os resultados das novas técnicas endovasculares estão muito próximos aos das tradicionais cirurgias vasculares. Embora a angioplastia ofereça bons resultados em curto prazo, o implante de stents procura melhorar o sucesso do procedimento e estender o seu uso a um número maior de pacientes com doença vascular periférica. Entretanto, a sua utilização ainda é controversa. O implante de stents no sistema aorto-ilíaco tem bons resultados; porém, a sua indicação para as lesões femoro-poplíteas ainda é discutida. Além disso, o rápido desenvolvimento de stents e sua escolha para uso no sistema vascular periférico têm sido uma difícil tarefa para o cirurgião endovascular. Muitos fatores influenciam a escolha do stent, e um amplo conhecimento desse material é essencial. Tal escolha depende da avaliação pré-operatória, da localização e das características da lesão e também do uso do stent primário ou seletivo. Nesse trabalho, são realizadas revisão do histórico do desenvolvimento dos stents, desde os estudos experimentais até os ensaios clínicos e também discussão sobre a sua aplicação no tratamento das doenças vasculares periféricas.

Self-expandable nitinol stent placement in homocysteinemic porcine aorta

PURPOSE

To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs (induced with a methionine-rich diet) following placement of a self-expanding nitinol stent.

METHODS

Eighteen Macau pigs were used. They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C (control), was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis.

RESULTS

Under microscopic evaluation, the intima was significantly thicker in Group C than in Group M. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. In group C the levels of plasma homocysteine ranged from 14,40 to 16,73 micromol/l; in Group M, plasma homocysteine levels ranged from 17.47 to 59.80 micromol/l after 30 days of a methionine-rich diet.

CONCLUSION

Compared to normal pigs, less intimal hyperplasia was observed in the abdominal aortas of hyperhomocysteinemic pigs thirty days after the insertion of a self-expandable nitinol stent.

Banding in aortic stent-graft fixation in EVAR

The authors describe the method of surgical aortic banding for better stent-graft fixation in cases of problematic aortic neck in the endovascular infrarenal aneurysms repair.

Ingrowth of aorta wall into stent grafts impregnated with basic fibroblast growth factor: a porcine in vivo study of blood vessel prosthesis healing

OBJECTIVE

Endovascular aneurysm repair is an alternative treatment of abdominal aortic aneurysm. The procedure is less invasive, and morbidity and most probably mortality are reduced. However, some problems, such as endoleakage, are yet to be resolved. Endoleakage can occur after graft migration, as a result of insufficient fixation of the stent graft. One cause is deficient healing between the aortic neck and the stent graft. We hypothesize that better healing, achieved by induction of vascular cell ingrowth into the graft material, results in better graft fixation. Previously we demonstrated ingrowth of neointima into the graft material if the stent graft is impregnated with a coat of basic fibroblast growth factor (bFGF), heparin, and collagen. In this study we evaluated healing with bFGF-heparin-collagen-coated stent grafts in vivo.

METHODS

In 4 pigs, 32 endovascular stent grafts, manufactured from standard Dacron and Gianturco Z-stents, were placed in the aorta. The stent grafts were impregnated with either bFGF-heparin containing collagen (n=16) or control collagen (n=16). After 4 and 8 weeks animals were killed, and ingrowth and healing of the stent grafts were macroscopically and electron microscopically evaluated.

RESULTS

After 8 weeks all bFGF-impregnated stent grafts demonstrated ingrowth of tissue and healing between the graft and the aorta, whereas the control nonimpregnated stent grafts showed no ingrowth. Microscopic evaluation demonstrated alpha-smooth muscle actin-positive cells, most probably smooth muscle cells or myofibroblasts, growing from the vascular wall through the graft material.

CONCLUSION

A Dacron prosthesis impregnated with collagen, heparin, and bFGF induced graft healing in an in vivo pig model, in contrast to nonimpregnated stent grafts. This in vivo study confirms our previous findings in vitro. These results indicate that healing between Dacron and the aorta can be achieved, and suggest that type I endoleakage may be resolved by inducing healing between the aortic wall and the prosthesis with graft material containing growth factor.

Does large oversizing of self-expandable endoprostheses compensate for aortic growth?

PURPOSE

There is experimental evidence that self-expandable endoprostheses are appropriate for compensation of aortic growth. A potential future application includes their use in the treatment of aortic coarctation. Yet their behavior is poorly investigated. The present study evaluates the performance of largely oversized self-expandable endoprostheses (EPs) in the growing porcine aorta and the biologic response toward them.

METHODS

Twenty oversized EPs (Talent, TalentLoPro, Stenway, and Wallstent; nominal lumen area 314 mm(2) [diameter 20 mm]) were implanted in the descending thoracic aorta of juvenile pigs. Four nonoversized EPs (TalentLoPro; nominal lumen area 154 mm(2) [diameter 14 mm]) served as controls. Cross sections of aorta and EPs were measured by intravascular ultrasound (IVUS) at implantation and 3 months follow-up. The histologic response was assessed by microscopy.

RESULTS

At implantation, the EPs were 99 +/- 41% oversized relative to the aortic area [48 +/- 22% in diameter]. At follow-up, the area of the aortic lumen increased 60 +/- 50%, P <.001 [29 +/- 23% in diameter]. The Stenway EPs demonstrated the largest prosthetic lumen with 80 +/- 10% of their nominal area (P =.001). However, the prosthetic lumen area was reduced by intimal hyperplasia in all devices. The largest perfused lumen was obtained by the TalentLoPro EPs due to their progressive expansion. Nonoversized EPs resulted in a significantly smaller perfused lumen (P =.012). The inflammatory response to polyester was moderate, whereas polyurethane evoked an extensive body-foreign reaction.

CONCLUSION

Large oversizing of self-expandable EPs is essential in order to maintain a large perfused lumen during aortic growth, thereby minimizing the adverse effect of intimal hyperplasia. This was best achieved by the TalentLoPro EPs.

Mechanical properties of various z-stent designs: an endovascular stent-grafting perspective

PURPOSE

To comparatively assess the mechani-cal behavior of various clinically relevant Z-stent designs.

METHODS

A total of 16 Z-stents of original, biliary, spiral, and double-skirted designs (n=4 for each) were constructed using similar specifications for all. Stents were then evaluated for stiffness, snap opening force (SOF), flexibility, and displacement force using a novel tensiometer. Differences among the stents were determined using statistical methods. Stents explanted from dog aorta after a mean follow-up of 13 months were examined under a scanning electron microscope for surface defects.

RESULTS

Forces required for about 50% reduction in diameter were 1.88 +/- 0.16 N, 3.81 +/- 0.21 N, 2.76 +/- 0.22 N, and 3.35 +/- 0.19 N for original, biliary, spiral, and skirted designs, respectively. Differences among the four designs were statistically significant at almost all points of measurement (P < 0.0001). Biliary and skirted designs showed higher SOF values in the early measurements. Stents explanted from dog aorta after a mean duration of 13 months showed no obvious corrosion or breakage in the wire struts.

CONCLUSIONS

Significant differences exist among the various Z-stent designs in terms of their mechanical properties. Understanding them should help to select the appropriate stent for a given lesion. 316L stainless steel shows a favorable long-term tissue interaction.

Fixation of infrarenal aortic stent-grafts using laparoscopic banding -- an experimental study in pigs

PURPOSE

to test whether a laparoscopically-placed external band around the infrarenal aorta could stop vessel dilatation and prevent stent-graft detachment from the aortic wall.

METHODS

in 13 growing pigs Gianturco-based stent-grafts were placed in the infrarenal aorta. In eight pigs, an external PTFE band (1 cm width) was placed laparoscopically around the infrarenal aorta. The remaining five pigs served as controls. Angiographic aortic diameters were measured: (1) at the most distal renal artery; (2) 1.5 cm further distally; (3) at the middle of the stent-graft; and (4) below the stent-graft, 1 cm above the aortic bifurcation.

RESULTS

at a median follow-up of 16 weeks the pigs in the control group (n =5) and in the banded group ( n =7) increased their weight from 24 kg to 107 kg and 23 to 83 kg, respectively. In the control group, aortic dimensions increased by approximately 40% at all levels. In the banded group, aortic dimensions were unchanged at levels 2 and 3, but increased significantly at levels 1 and 4 (i.e. above and below the stent-graft). In the control group all stent-grafts detached causing a proximal perigraft leakage. No detachment or proximal perigraft leak was observed in the banded group.

CONCLUSION

a laparoscopically placed external band around the infrarenal aorta of growing pigs seems to counteract the vessel dilatation and thereby provides a stable fixation of self-expandable stent-grafts.

Differing morphological changes following endovascular AAA repair using balloon-expandable or self-expanding endografts

PURPOSE

To determine whether changes in aneurysm morphology after endovascular abdominal aortic aneurysm (AAA) repair differ according to the type of endograft (self-expanding versus balloon-expandable).

METHODS

Among 88 patients with AAA treated with either homemade polytetrafluoroethylene (PTFE) aortomonoiliac endografts or Talent stent-grafts, 30 patients (24 males; mean age 73 years, range 55-93) were selected for this study based on a >2-year follow-up and freedom from endoleak or conversion. Of these, 12 had PTFE endografts and 18 Talent devices. All patients had spiral computed tomographic angiography with 3-dimensional reconstruction at 5 days posttreatment and 6-month intervals thereafter. Neck dimensions (length and diameters at 3 levels) were measured, along with volumes and maximal diameters of the sac and lengths of the aneurysm and endograft. Intra- and interobserver errors were <5% for linear and volume measurements.

RESULTS

Both groups had an initial 20-mL increase in median volume (p = 0.02) followed, only in Talent patients, by marked shrinkage at 6 months (-87.4 mL; p = 0.09). PTFE patients had no further changes in sac volume. Maximal sac diameters reflected volumes, but only after day 5. PTFE patients had an immediate increase (p = 0.03) in aneurysm neck diameters, which then remained stable. Talent patients had continuing increases in diameter to 6 months (p < 0.05), with no change thereafter. Length changes were not significant in either group. PTFE patients had an increase in median aneurysm length at day 5 (+3.2 mm, p = 0.04) and again at 1.5 years (+6.4 mm, p = 0.03). Endograft length slowly increased (+18.7 mm) over 1.5 years (p = 0.02). Talent patients had no length changes in the device or aneurysm.

CONCLUSIONS

Aneurysm morphology appeared to alter according to the type of endograft deployed. With PTFE endografts, aneurysm volume does not change, whereas impressive sac shrinkage occurs in conjunction with the Talent system. Aneurysm/graft lengths increase with unsupported stent-grafts. Neck diameter increases immediately with balloon-expandable endografts and then remains constant. In the self-expanding models, neck diameter increases at 6 months but not thereafter.

Stent attachment site-related endoleakage after stent graft treatment: An in vitro study of the effects of graft size, stent type, and atherosclerotic wall changes

OBJECTIVE

Perigraft endoleakage is a major complication of the endovascular treatment of abdominal aortic aneurysms. The factors that cause this form of endoleakage are not completely identified. The effect of sizing of the prosthesis in combination with either self-expandable or balloon-expandable stents is evaluated in this study. Further, the influence of atherosclerotic changes on endoleakage is evaluated.

METHODS

Eight human abdominal aortas were assessed macroscopically at 11 sites for the presence of atherosclerotic changes with intravascular ultrasound scanning (IVUS) and with computed tomography (CT). Five aortas were placed in in vitro circulation with physiologic parameters. After the determination of the proximal and distal landing site of the stent graft, the diameter and surface measurements of the cross sections were taken. The stent graft diameters were chosen from 4-mm undersizing to 6-mm oversizing, both for Gianturco stent grafts (William Cook Europe A/S, Bjaeverskov, Denmark) and for Palmaz stent grafts (Cordis/Johnson & Johnston Co, Warren, NJ). After placement of the stent graft, the diameter and surface measurements of the aortic cross section were determined at the proximal and distal stent attachment sites. The presence and size of the folds at the stent attachment site and the interface with the aortic wall were determined with IVUS and angioscopy. Endoleakage was evaluated with angiography. After angioplasty of the stent attachment site, IVUS, angioscopy, and angiography were repeated.

RESULTS

Regarding atherosclerotic changes of the aortic wall, the correlations between clinical impression and CT, clinical impression and IVUS, and CT and IVUS were high (r = 0.77, r = 0.79 and r = 0.79, respectively). For the Gianturco stent grafts, no significant relationship existed between the diameters measured before and after stent graft placement, leading to great differences in intended and achieved oversizing. The achieved oversizing was less in the case of minimal atherosclerotic changes of the aortic wall. The Gianturco stent graft followed the aortic wall closely during the heart cycle. The sizes of the folds of the fabric were clearly correlated with the achieved oversizing (r = 0.83; P =.04) and the grade of endoleakage (r = 0.88; P =.022). Angioplasty after stent graft placement had no effect on the diameter and the grade of endoleakage. Palmaz stent grafts did not follow the aortic wall during the heart cycle. A significant correlation existed between oversizing and both space between aortic wall and stent graft (r = -0.88; P =.02) and grade of endoleakage (r = 0.84; P =.036). Grade of endoleakage in the Palmaz stent graft group was less than in the Gianturco stent graft group.

CONCLUSION

With the use of Gianturco stents, a great difference between intended and achieved oversizing is accomplished. The atherosclerotic changes of the aortic wall possibly affect this finding. The configuration of the Gianturco stent results in the formation of fold in the case of oversizing, which is associated with endoleakage. However, the self-expandable character of the stent leads to a close relation to the aortic wall during the heart cycle, and this may possibly accommodate future aortic neck dilation. The Palmaz stent grafts do not follow the aortic wall during the heart cycle, but they do lead to better interface between the graft and the aortic wall, which results in less endoleakage.

Histopathologic evaluation of an expanded polytetrafluoroethylene-nitinol stent endoprosthesis in canine iliofemoral arteries

PURPOSE

The authors assess a new ePTFE-nitinol stent for its long-term patency, healing, and properties of endothelialization.

MATERIALS AND METHODS

Adult greyhounds (n = 18) underwent bilateral iliofemoral placement of an endoprosthesis (Hemobahn) consisting of a nitinol stent lined with an ultrathin expanded polytetrafluoroethylene (ePTFE) material. Histologic and quantitative morphometric analyses were performed on devices explanted at 2 weeks and 1, 3, 6, and 12 months. The source of endothelialization was examined in four additional devices modified by sealing either the proximal and distal ends or the entire graft with poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), a nonporous laminate to prevent potential transgraft endothelial cell migration.

RESULTS

Device patency assessed with both intravascular ultrasound and histologic study showed minimal arterial stenosis, irrespective of implant duration. The neointima at less than 3 months consisted of fibrin and inflammatory infiltrate; at later time points, it was composed of mostly smooth muscle cells. Flow surfaces were more than 75% endothelialized by 3 months, which was nearly complete by 6 months. Modified endoprostheses entirely enveloped with FEP resulted in endothelialization of only the proximal and distal ends; the middle regions showed nonocclusive thrombi. Conversely, devices wrapped proximally and distally showed nearly complete endothelialization.

CONCLUSIONS

This ePTFE-nitinol endoprosthesis demonstrated long-term patency at up to 1 year after implantation and showed early and nearly complete endothelialization by 6 months. The design promoted rapid endothelialization of flow surfaces, particularly in the midregion of the device possibly by transgraft migration.

Distal migration of stent-grafts after endovascular repair of abdominal aortic aneurysms

PURPOSE

To analyze patients after endovascular repair of abdominal aortic aneurysm (AAA) with respect to distal migration of stent-grafts and its underlying causes.

MATERIALS AND METHODS

Sixty-five patients underwent endovascular repair between January 1994 and February 1997. There were seven women and 58 men, with a mean age of 71 years (range, 51-84 years). Three patients died in the perioperative period (one of myocardial infarction and two of multiorgan failure) and two patients died within 4 months of the procedure of non-procedure-related causes. In addition, two patients were followed at another hospital. The remaining 58 patients were followed up with spiral computed tomography scans at 1, 3, and 6 months, and biannually thereafter. Angiography was performed at 1 month and 1 year after the procedure and additionally when deemed clinically necessary. Mean follow-up was 29 months (range, 1-49). Migration more than 5 mm was considered significant.

RESULTS

Twenty-six patients (45%) showed distal migration of stent-grafts during follow-up. Mean follow-up time at detection of migration was 13 months (range, 1-36 months). Thirteen cases of migration were ascribed to dilatation of the proximal aneurysmal neck during follow-up. Ten cases of migration were ascribed to causes other than neck dilatation or poor patient selection. In three cases, no obvious cause for the migration was found. The migration was complete in eight cases, leading to late conversion to open surgical repair. On two of these occasions, complete migration lead to aneurysm rupture. In addition, four patients received additional stent-grafts as proximal extensions.

CONCLUSIONS

Distal migration of stent-grafts after endovascular AAA repair occurred frequently in this series. Dilatation of the proximal aneurysmal neck is a major cause of distal migration of stent-grafts. Improved proximal fixation is needed to secure long-term durability.

Experimental assessment of proximal stent-graft (InterVascular) fixation in human cadaveric infrarenal aortas

OBJECTIVES

This paper investigates the radial deformation load of an aortic endoluminal prosthesis and determines the longitudinal load required to cause migration in a human cadaveric aorta of the endoprosthesis.

DESIGN AND METHODS

The endovascular prosthesis under investigation was a 24 mm diameter, nitinol, self-expanding aortoaortic device (InterVascular, Clearwater, Florida, U.S.A.). Initially, a motorised digital force gauge developed an incremental load which was applied to the ends of five stent-grafts, to a maximum of 10 mm (42%) compression. Secondly, using a simple bench model, each ends of four stent-grafts were deployed into 10 cadaveric experimental aneurysm necks and a longitudinal load applied to effect distraction.

RESULTS

Increasing load produced increasing percentage deformation of the stent-grafts. The mean longitudinal distraction load for an aneurysm neck of 20 mm was 409 g (200-480 g), for 15 mm was 277 g (130-410 g) and for 10 mm was 218 g (130-340 g). The aneurysm diameter and aortic calcification had p values of 0.002 and 0.047, respectively, while the p value for aneurysm neck length was less than 0.00001.

CONCLUSIONS

These results suggest that there is a theoretical advantage of oversizing an aortic prosthesis and that sufficient anchorage is achieved in an aortic neck of 10 mm to prevent migration when fully deployed.

Dilatation of the infrarenal aneurysm neck after endovascular exclusion of abdominal aortic aneurysm

PURPOSE

To determine the fate of the infrarenal aneurysm neck and suprarenal aorta after endovascular exclusion of abdominal aortic aneurysms (AAAs).

METHODS

Thirty-four patients underwent endovascular AAA repair between January 1994 and December 1995 using custom-made stent-grafts constructed from polyester graft material and modified self-expanding Gianturco Z-stents sutured to the graft orifices. Thirty-one patients were available for follow-up. Pre- and postimplantation diameters were measured using spiral computed tomography in the infrarenal aneurysm neck and the suprarenal aorta at the level of the superior mesenteric artery (SMA).

RESULTS

The mean follow-up time was 25 months. There was a significant increase of the diameter of the infrarenal aneurysm neck (+ 1.65 mm, p = 0.002), but not in the aorta at the level of the SMA (+0.52 mm, p = 0.100). There was no difference in the change in diameter in the infrarenal neck in the group with a stent adjacent to the level of measurement (n = 20) compared with the group without an adjacent stent (n = 11, p = 0.790). There was no correlation between preimplantation size of the infrarenal neck and its diameter change (r = 0.14, p = 0.488). There was no correlation (r = 0.10, p = 0.603) or association (chi-square test, p = 0.211) between aortic diameter change at the level of the SMA and the infrarenal neck.

CONCLUSIONS

This investigation shows a significant dilatation of the infrarenal aneurysm neck, but not in the suprarenal aorta, after endovascular AAA repair with this device. The clinical significance of these findings is unclear. Whether such a dilatation in the infrarenal aneurysm neck may affect the long-term attachment of stent-grafts remains to be shown in the future.

Comparison of computed tomography and duplex imaging in assessing aortic morphology following endovascular aneurysm repair

BACKGROUND

Computed tomography (CT) has been used to assess patients following endovascular aneurysm repair to determine the need for secondary endoluminal or operative procedures. This prospective study compared CT and duplex imaging to evaluate aneurysm morphology following endoluminal aortic grafting.

METHODS

Twenty patients were evaluated at regular intervals following successful endoluminal aneurysm repair. CT and duplex scanning were compared in their ability to determine aneurysm and aortic diameter, the presence of perigraft extravasation (endoleaks) and technical defects in the endograft.

RESULTS

In 20 patients who were assessed 6 months after operation, duplex imaging identified four endoleaks (two early, two late; one proximal, three distal). In three cases, the aneurysm diameter progressively increased after operation. In patients with a thrombosed aneurysm sac, the aneurysm regressed at a median of 0.40 (range 0.13-0.8) cm per year. The CT findings were similar (median regression 0.43 (range 0-1.0) cm per year), although CT was unable to predict the site of the leak as accurately as duplex imaging. CT demonstrated that the diameter of the juxtarenal aorta increased following endografting.

CONCLUSION

Duplex imaging is a less invasive, less costly alternative to CT in the follow-up of patients after endoluminal aortic surgery. Increase in size of the aneurysm sac following endovascular aneurysm repair strongly suggests the presence of an endoleak.

Renal arteries covered by aortic stents: clinical experience from endovascular grafting of aortic aneurysms

OBJECTIVES

During the endovascular repair of abdominal aortic aneurysms (AAAs), effective anchoring of the stent-graft is difficult in the presence of a short infrarenal aneurysm neck. The aim of this study was to investigate renal artery patency and renal function after deployment of graft anchoring stents across the renal arteries.

DESIGN

Retrospective open study.

PATIENTS

Twenty-five renal arteries, in 18 patients treated by endovascular exclusion of an AAA, were intentionally covered with the Gianturco Z-stent to ensure stent graft attachment.

METHODS

Renal artery patency was assessed by repeated spiral computed tomography (CT) scans and angiography. Creatinine levels, blood pressure and antihypertensive medication were recorded. Follow-up was a median 6 months (2-9).

RESULTS

All 25 stent-covered renal arteries remained patent. CT showed a small infarct in one kidney. Creatinine was 108 mumol/l (89-133) before intervention and 98 mumol/l (87-127) at follow-up. Blood pressure was 150/80 mmHg on both occasions. Antihypertensive therapy was intensified in one patient whose creatinine level remained stable and whose separate renin sampling was normal.

CONCLUSIONS

Covering the renal arteries with the Gianturco Z-stent does not seem to affect renal function within 6 months. Further follow-up is needed before suprarenal stent deployment can be advocated.

The use of intravascular ultrasound as control procedure for the deployment of endovascular stented grafts

OBJECTIVE

To assess whether intravascular ultrasound (IVUS), used systematically in a series of patients with abdominal aortic aneurysms (AAA), is a feasible control procedure to ensure correct transfemoral placement of endovascular stent grafts (TPEG).

DESIGN

Descriptive study.

MATERIALS AND METHODS

Fourteen patients with infrarenal aortic aneurysms were treated by the placement of one tube graft, 10 aorto-uni-iliac and three aorto-bi-iliac grafts. Arteriography and IVUS were performed before, during and after deployment of the graft to ensure correct placement in relation to side branches, and proper adaptation of the stents to the aortic wall. Postoperative CT-scan and arteriography served as control procedures.

RESULTS

IVUS identified both renal arteries before graft deployment in eight of 13 (62%) patients. In the remaining patients only one renal artery was visualised due to interference from guidewires or the introducer system. Imaging during stent deployment was abandoned after IVUS catheter damage in two of three cases. Postprocedural IVUS was able to evaluate the expansion of the stents and the adaptation to the aortic wall in all instances. In four (29%) cases a leak was identified. Additional intervention included deployment of a further stent (n = 2) or redilation (n = 2). Covering of the renal arteries could only be indirectly determined by IVUS.

CONCLUSION

IVUS can provide important decisive information before and after stented graft deployment, with the limitations that guidewires, introducer system and stents may cause interference. Contemporary IVUS designs are unsuitable for monitoring stent deployment.

Changing aneurysmal morphology after endovascular grafting: relation to leakage or persistent perfusion

PURPOSE

To relate changing abdominal aortic aneurysm (AAA) morphology after endovascular grafting to the presence of leakage, collateral perfusion, and other factors.

METHODS

Thirty-five patients who underwent successful AAA endovascular grafting were evaluated. Self-expanding Z-stents and Dacron grafts were applied in bifurcated and aortomonoiliac systems. Postoperative diameter changes were calculated from repeated spiral computed tomographic scans, angiograms, and ultrasonic phase-locked echo-tracking scans during a median 6-month follow-up (interquartile range [IQR] 3 to 12).

RESULTS

At 12 months, the diameters of completely excluded aneurysms had decreased 6 mm (IQR 2 to 11; p = 0.006). The proximal graft-anchoring stents had dilated 2 mm (IQR 0.5 to 3.3; p = 0.01). The aortic diameters immediately below the renal arteries but above the stents had not changed. Endoleakage and collateral perfusion (n = 13) were each associated with preserved aneurysm size and a 12 times higher risk of aneurysm dilation. After the leakage or the collateral perfusion had been treated, the aneurysm size decreased. Aneurysms with extensive intraluminal thrombi presented a reduced risk of leakage or perfusion.

CONCLUSIONS

The diameters of endovascularly excluded AAAs decrease, except in cases of leakage or perfusion. Careful follow-up of patients with aortic endografts is necessary.