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

Degradation Phenomena on "Homemade" Explanted Aortic Textile Endografts

Objective

In the 1990s, the concept of “homemade” endografts (EGs) using commercially available materials was proposed in clinical practice for endovascular abdominal aortic repair (EVAR). The aim of this study was to analyse the ageing phenomena of these EGs in light of explant analyses.

Methods

The study focused on five explanted homemade EGs collected from 2012 to 2014. The explants were assessed in accordance with the ISO 9001/13485 certified standard protocol, which included naked eye evaluation, organic remnant cleaning, and microscopic and endoscopic examinations and analysis (magnification range from 20% to 200%). The observations report followed a classification based on 12 features assessing the fabric cover, the stitch filament, and the stents.

Results

The reasons for explantation were type 1 endoleak in three cases and aneurysm sac growth in two. The implantation duration ranged from 56 to 202 months. Sixty three per cent of the fabric surface lesions (holes and tears) were related to abrasion between the fabric and the stents. Up to 33% of the knots used to connect adjacent stents were broken on one EG. Other defects including running suture rupture and stent corrosion were also observed. The overall hole cumulated surface ranged from 0.377 mm² (56 month of implantation) up to 3.21 mm² (78 month of implantation).

Conclusion

In this study, various ageing phenomena on homemade textile EGs were identified and classified. The main damaging mechanisms were related to abrasion stress leading to tears and holes in the fabric, stitch ruptures, and detachment of stent segments responsible for serious EG deformations and further degradation.

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Main homemade endografts damaging mechanisms are related to abrasion stress (friction wear).

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Abrasion stent–metal, knot ruptures, and kinking phenomena were associated.

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Some damaging mechanisms were related to the creation technique (one piece stent skeleton).

Novel Embolic Protection Device: a Feasibility Study

Stroke is ranked as the second leading cause of death worldwide. Ischemic stroke commonly results from emboli that originate in the heart among high-risk patients, such as those who develop atrial fibrillation. Yet, treatment is currently limited to anticoagulants, which may be associated with life-threatening bleeding. Our aim was to develop an alternative, device-based approach for continuous stroke prevention in high-risk patients. To this end, a novel endovascular tubular mesh was designed to be implanted in the aortic arch and to reroute emboli away from critical cerebral arteries. The feasibility of this approach as a means of ischemic stroke prevention was tested in vitro. The simulated cerebral perfusion pressures were not affected by the device. Also, the device efficiently diverted clinically meaningful embolic particles away from the cerebral circulation. It is proposed that this device could be used to reroute cardio-emboli away from intracranial vessels as a means of stroke prevention among patients for which anticoagulants are contraindicated.

Custom-made Stent-Grafts for Aortic Aneurysm Repair Using Gianturco Z Stents and Woven Polyester: Healing in an Animal Model

The purpose of this study was to evaluate the healing at 6 months of aortic stent-grafts custom-made by using Z stents and woven polyester in an animal model. Stent-grafts were built by a published method using autoexpandable stainless steel stents continuously compiled with polyester sutures and covered with a woven polyester membrane. Fourteen stent-grafts of 3 different designs were deployed under fluoroscopic control into the thoracic and the abdominal aorta of 7 adult sheep. At 6 months, all the implants of the sheep that survived the implantation were angiographed and harvested for macroscopy and microscopy. All stentgrafts were implanted successfully and remained patent from then to the explantation procedure. All stent-grafts implanted among the 6 of 7 (86%) animals that survived after the implantation remained patent, stayed free from local complications, and did not migrate during more than 6 months. In all these cases during this period, the implant functioned as a satisfactory aortic substitute while the aortic segment containing the graft kept a normal structure. There was no adverse effects of the presence of the implant upon the aorta or the animal. Stent-grafts home-made according to the described methods gave results at 6 months in this animal model compatible with a safe clinical application among humans.

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.

Improvement in Proximal Aortic Endograft Fixation: An Experimental Study Using Different Stent-Grafts in Human Cadaveric Aortas

Purpose:

To compare the proximal fixation characteristics of different types of stent-grafts (SG) and the adjunctive effect of a proximally placed Palmaz stent.

Methods:

Human cadaveric aortas were obtained at autopsy and cut into 30 aortic segments. Appropriately oversized (10% to 20%) commercial stent-grafts (Zenith, Ancure, Excluder, Talent) and 4 configurations of homemade Palmaz-based stent-grafts (polytetrafluoroethylene or polyester coverings each with no uncovered proximal edge or a 20-mm bare section of stent) were implanted 20 mm into an aortic segment and balloon dilated. Each segment was placed in an experimental apparatus to measure the dislodgment force. Bare Palmaz stents were used to reinforce the proximal fixation of the commercial stent-grafts, and the measurements were repeated. Manual anastomoses were made and their dislodgment force tested for comparison.

Results:

The median dislodgment force ranged from 6.5 N for the Excluder to 26.5 N for the Zenith (8.0 N for the Talent, 11.8 N for the Ancure, and 8.1 to 10.7 N for the various Palmaz stent-graft designs). There was no significant difference between the Zenith and the Ancure groups or between the Excluder and the Talent groups. However, the Zenith and Ancure devices required significantly higher (p = 0.0004) force (∼25%) to displace them than the other stent-grafts tested. With the Palmaz stent added to the proximal attachment site, the median dislodgment force for the different commercial endografts was significantly improved for all devices (p < 0.03): 34% for the Zenith device, 69% for the Ancure, 73% for the Talent, and 80% for the Excluder endoprosthesis.

Conclusions:

The Zenith stent-graft had the best resistance to dislodgment. An additional Palmaz stent placed at the proximal attachment site greatly improves endograft fixation regardless of the type of stent-graft. For complex aneurysm necks or for intraoperative type I endoleak management, an adjunctive Palmaz stent could be used.

Aorto—Left Renal Vein Fistula: Is There a Place for Endovascular Management?

Purpose:

To describe the endovascular treatment of an aorto-left renal vein fistula.

Methods and Results:

A 77-year-old man with multiple comorbidities presented with low back pain, hematuria, cyanosis, and a pulsatile abdominal mass. Imaging confirmed a 7-cm abdominal aortic aneurysm with a contained rupture into the left renal vein. Owing to the patient's high surgical risk, a Talent Endoluminal Stent-Graft was implanted to satisfactorily exclude the aneurysm. Hemodynamic stability and normal renal function were restored; however, continued perfusion of the sac prompted an attempt to percutaneously repair the renal vein defect. This effort failed, so open laparotomy was necessary.

Conclusions:

Although total endovascular management was not successful in this case, the initial use of a minimally invasive approach allowed the patient's clinical status to improve and lower the risk of subsequent surgery.

Endoluminal Repair of Aneurysms Containing Ostia of Essential Branch Arteries: An Experimental Model

Purpose:

To examine experimentally the feasibility of transfemoral endoluminal repair of aneurysms containing the ostia of essential branch arteries.

Methods:

In a canine model (n = 4), suprarenal aortic aneurysms were created by suturing an artificial patch onto an anterior arteriotomy. Following a 2-week recovery period, the dogs underwent endovascular exclusion of their aneurysms using an aortic stent-graft with separate renal artery branch grafts. Outcome was evaluated using angiography, intravascular ultrasound (IVUS), Doppler flow, invasive pressure monitoring, and autopsy, respectively.

Results:

Successful creation and subsequent endovascular exclusion of the aneurysm using aortic stent-grafts and separate bilateral renal artery stent-grafts was achieved in all trials. Angiographically, all aneurysms were excluded from aortic flow and all renal arteries were patent at completion of the procedure. With IVUS, good graft apposition and absence of perigraft flow were demonstrated in all animals. Mean pressure in the aneurysmal sac at completion of the procedure was 40 ± 7 mmHg, compared to a mean systemic blood pressure of 105 ± 8 mmHg (p < 0.05). At autopsy, no gross intimal damage was seen in the aorta or the renal arteries, and intact aortic grafts and branch grafts without twisting, coiling, or kinking were found in all trials.

Conclusions:

In an acute animal model, suprarenal aortic aneurysms can be excluded from the circulation with preservation of renal flow using an endoluminally placed aortic stent-graft with separate branch grafts.

Endovascular AAA Exclusion: Will Stents with Hooks and Barbs Prevent Stent-Graft Migration?

Purpose:

To investigate if stents with hooks and barbs will improve stent-graft fixation in the abdominal aorta.

Methods:

Sixteen- to 24-mm-diameter Dacron grafts were deployed inside cadaveric aortas. The grafts were anchored by stents as in endovascular abdominal aortic aneurysm repair. One hundred thirty-seven stent-graft deployments were carried out with modified self-expanding Z-stents with (A) no hooks and barbs (n = 75), (B) 4 5-mm-long hooks and barbs (n = 39), (C) 8 10-mm-long, strengthened hooks and barbs (n = 19), or (D) hooks only (n = 4). Increasing longitudinal traction was applied to determine the displacement force needed to extract the stent-grafts. The radial force of the stents was measured and correlated to the displacement force.

Results:

The median (interquartile range) displacement force needed to extract grafts anchored by stent A was 2.5 N (2.0 to 3.4), stent B 7.8 N (7.4 to 10.8), and stent C 22.5 N (17.1 to 27.9), p < 0.001. Both hooks and barbs added anchoring strength. During traction, the weaker barbs were distorted or caused intimal tears. The stronger barbs engaged the entire aortic wall. The radial force of the stents had no impact on fixation, while aortic calcification and graft oversizing had marginal effects.

Conclusions:

Stent barbs and hooks increased the fixation of stent-grafts tenfold, while the radial force of stents had no impact. These data may prove important in future endograft development to prevent stent-graft migration after aneurysm exclusion.

The quantification of hemodynamic parameters downstream of a Gianturco Zenith stent wire using newtonian and non-newtonian analog fluids in a pulsatile flow environment

Although deployed in the vasculature to expand vessel diameter and improve blood flow, protruding stent struts can create complex flow environments associated with flow separation and oscillating shear gradients. Given the association between magnitude and direction of wall shear stress (WSS) and endothelial phenotype expression, accurate representation of stent-induced flow patterns is critical if we are to predict sites susceptible to intimal hyperplasia. Despite the number of stents approved for clinical use, quantification on the alteration of hemodynamic flow parameters associated with the Gianturco Z-stent is limited in the literature. In using experimental and computational models to quantify strut-induced flow, the majority of past work has assumed blood or representative analogs to behave as Newtonian fluids. However, recent studies have challenged the validity of this assumption. We present here the experimental quantification of flow through a Gianturco Z-stent wire in representative Newtonian and non-Newtonian blood analog environments using particle image velocimetry (PIV). Fluid analogs were circulated through a closed flow loop at physiologically appropriate flow rates whereupon PIV snapshots were acquired downstream of the wire housed in an acrylic tube with a diameter characteristic of the carotid artery. Hemodynamic parameters including WSS, oscillatory shear index (OSI), and Reynolds shear stresses (RSS) were measured. Our findings show that the introduction of the stent wire altered downstream hemodynamic parameters through a reduction in WSS and increases in OSI and RSS from nonstented flow. The Newtonian analog solution of glycerol and water underestimated WSS while increasing the spatial coverage of flow reversal and oscillatory shear compared to a non-Newtonian fluid of glycerol, water, and xanthan gum. Peak RSS were increased with the Newtonian fluid, although peak values were similar upon a doubling of flow rate. The introduction of the stent wire promoted the development of flow patterns that are susceptible to intimal hyperplasia using both Newtonian and non-Newtonian analogs, although the magnitude of sites affected downstream was appreciably related to the rheological behavior of the analog. While the assumption of linear viscous behavior is often appropriate in quantifying flow in the largest arteries of the vasculature, the results presented here suggest this assumption overestimates sites susceptible to hyperplasia and restenosis in flow characterized by low and oscillatory shear.

How to design the optimal stent graft--what have we learnt?

It is now more than 20 years since the first report of stent graft insertion in the human arterial system was published. The first "homemade" devices proved that the technique was possible but could not show any durability. Using these devices, it was possible to get a good seal but not a good anchorage. Not even the first generation of commercially available stent grafts proved to be durable. First after gaining knowledge about the forces acting on the stent graft, it was realized that attachment was important for the durability and the hooks and barbs or a longitudinal stability are needed to minimise the risk for distal migration. Not much of a difference in the overall performance is noticed between the ePTFE graft or the polyester graft or when comparing stainless steel stents with those made out of nitinol. The systems are made much more flexible and hydrophilic leading to a better performance and a greater chance of percutaneous approach. The optimal stent graft is not out on the market yet, but hopefully will come with further development.

A novel endovascular device for emboli rerouting: part I: evaluation in a Swine model

BACKGROUND AND PURPOSE

The feasibility and safety of a novel endovascularly delivered tubular mesh designed to reroute emboli away from a critical artery as a means of ischemic stroke prevention was tested in vitro and in vivo.

METHODS

Emboli rerouting efficacy was assessed in vitro. Perfusion through the external femoral artery that was jailed by the device, cellular proliferation rate over the jailing mesh, and the resulting tissue coverage of the orifice were assessed in the swine iliofemoral bifurcation. Device-induced embolization was assessed in a swine kidney model.

RESULTS

In vitro experiments demonstrated that particles as small as 60% of the pore dimension can be rerouted by the device, although at low efficacy, and rerouting efficacy approached 100% as the particle size approached the pore dimension. Repeat assessment of flow preimplantation and at various follow-up times by Doppler ultrasound showed no significant changes in the perfusion ratio of the jailed branch to the parent artery or the jailed branch to the naive contralateral artery either as a result of device implantation or at the follow-up times. Tissue coverage over the jailed ostium was limited to approximately 12% after stabilization. Cellular proliferation rate gradually decreased to diminishing level approximately 22 weeks postimplantation. The devices implanted across the renal arteries did not demonstrate any device-induced embolization after 1 month.

CONCLUSIONS

It is proposed that this device could be used to reroute emboli away from important intracranial vessels as a means of stroke prevention.

Dynamic Cine-Computed Tomography Angiography Imaging of Standard and Fenestrated Endografts: Differing Effects on Renal Artery Motion

Different endograft configurations (fenestrated, transrenal, infrarenal) may varyingly affect aortic side branch movement. Renal artery motion was evaluated with 64-slice dynamic cine-computed tomography angiography before and after endovascular aneurysm repair in 16 patients (46 renal arteries). Center-of-mass displacement of the renals was determined per heartbeat for before repair for 3 different endografts; differences were compared, with significance at P < 0.5. Preoperative renal artery motion is significant (1.2 [SD 0.5] mm, range, 0.6-2.). Neither transrenal nor infrarenal endografts alter renal artery motion compared with before repair ( P < .05). Renal artery motion after fenestrated endovascular repair with renal stents reduces motion to 25% of the preoperative value (0.3 [SD, 0.1] mm, range, 0.2-0.5 mm; P = .01). Endograft implantation without stented side branches does not change renal artery motion, potentially allowing significant movement of the renal artery relative to the fenestration. Routine stenting of fenestrations limits postoperative renal artery motion to 0.3 mm, thereby preventing significant branch movement in relation the fenestration.

Suprarenal endograft fixation and medium-term renal function: systematic review and meta-analysis

BACKGROUND

Suprarenal fixation is widely used in endovascular aneurysm repair. Numerous small, underpowered studies have concluded that it does not increase the risk of renal impairment compared with infrarenal fixation. A recent meta-analysis demonstrated that renal infarction is more common with suprarenal fixation, but the effect on renal function remains unclear.

METHODS

Electronic abstract databases, article reference lists, and conference proceedings were searched for series reporting renal function data after suprarenal fixation. There was considerable study heterogeneity with respect to key factors such as pre-existing renal dysfunction and length of follow-up. Authors were contacted to obtain individual patient data for a pooled reanalysis using standardized criteria.

RESULTS

Of 46 potentially relevant citations, only 11 were eligible for inclusion in the meta-analysis. Complete data sets were available for four studies (1065 patients), with a median follow-up of 33 months. Kaplan-Meier curves were constructed for postoperative renal impairment in the suprarenal fixation and infrarenal fixation groups and compared by the log-rank test. Median time free of renal impairment was 38.5 months in the infrarenal fixation group compared with 32.4 months in the suprarenal fixation group (P = .0038). However, to account for significant methodologic differences, further analysis was required using a Weibull regression model fitted in open Bayesian inference using Gibbs sampling (BUGS). The pooled hazard ratio for deterioration of renal function after suprarenal fixation was 0.6 (95% confidence interval, 0.3-10).

CONCLUSION

Currently available data are insufficient to determine the precise effect of suprarenal fixation on medium-term renal function. Conventional Kaplan-Meier analysis of the pooled data set suggested that suprarenal fixation increased the risk of renal dysfunction; however, the effect disappeared when sophisticated statistical modelling was performed to account for study heterogeneity. A randomised controlled trial of suprarenal fixation may resolve this issue.

Visceral and Renal Artery Complications of Suprarenal Fixation during Endovascular Aneurysm Repair

BACKGROUND

The effect of suprarenal fixation of endovascular grafts on renal and visceral artery function remains undefined. This study aimed to determine renal and visceral artery complications following suprarenal fixation during endovascular aneurysm repair (EVR).

METHODS

Prospectively collected data from 112 patients who received suprarenal fixation (group SF) and 36 patients who received infrarenal fixation (group IF) in a single institution from December 1997 to April 2005 were reviewed retrospectively. Median follow-up was 26 months (range 0.1-101 months).

RESULTS

Stent struts extended to or above the level of 106 (94.6%) right renal arteries, 104 (92.9%) left renal arteries, 49 (43.8%) superior mesenteric arteries (SMA), and 7 (6.3%) celiac arteries in group SF. This group had 2 (1.8%) unintentional main renal artery occlusions, of which 1 was successfully treated at the first procedure with a renal stent. There was 1 (0.9%) SMA occlusion which resulted in bowel infarction and death. Group IF had no renal or visceral artery complications. There were no late-onset occlusions or infarcts. There was no significant difference in median serum creatinine between groups SF and IF at 1 month (p = 0.18) and 6 months to 12 months (p = 0.22) follow-up. The change in serum creatinine over time was also not significantly different within each group (SF, p = 0.09; IF, p = 0.38).

CONCLUSIONS

In this study, suprarenal fixation was associated with a very small incidence of immediate renal and visceral artery occlusion. There did not appear to be any medium-term sequelae of suprarenal fixation.

Durability of renal artery stents in patients with transrenal abdominal aortic endografts

OBJECTIVE

The management of renal artery stenosis in patients with abdominal aortic aneurysms continues to be complex and technically challenging despite advances in endovascular therapy. There is growing concern about the durability of renal artery stents in the setting of transrenal abdominal aortic endografts. This study reports a single-center experience of renal artery stenting with transrenal abdominal aortic endografts for patients with renal artery stenosis.

METHODS

All patients undergoing endovascular abdominal aortic aneurysm repair preceded or followed by renal artery stent placement between January 1999 and December 2005 were retrospectively reviewed from a prospectively gathered endovascular database. Patients were surveyed after renal stent procedures with multidetector computed tomography angiography or duplex sonography. The surveillance data were analyzed for primary patency of the renal artery stent at 6 months, incidence of complications, need for secondary interventions, and changes in creatinine clearance (CrCl).

RESULTS

Sixty-two renal artery stents were placed in 56 patients (44 men, 12 women) with a mean age of 77.3 years (range, 61 to 94 years). Forty-one were placed before the endograft procedure, eight were placed during the endograft procedure, and 13 were placed postoperatively. There were no major or minor complications related to the renal artery stent procedures. Transrenal aortic endografts were used in 44 of the 56 patients, and 12 had devices with infrarenal fixation. The mean follow-up was 18.5 months (range, 1 to 73 months). The 6-month primary patency, which could be evaluated for 51 renal artery stents, was 97.4% (37/38) in patients with transrenal fixation and 84.6% (11/13) in patients with infrarenal fixation. The overall rate of in-stent restenosis was 8.5% (4/47) in the transrenal fixation group and 20.0% (3/15) in the infrarenal fixation group. The overall occlusion rate was 2.1% (1/47) in the transrenal fixation group and 0% (0/15) in infrarenal fixation group. Five (83.3%) of six patients underwent successful treatment of in-stent restenosis with placement of a new stent in all five cases. CrCl decreased in the total group by 4.2 +/- 11.8 mL/min, by 4.7 +/- 12.0 mL/min in patients with transrenal fixation, and by 2.2 +/- 11.0 mL/min in patients with infrarenal fixation.

CONCLUSION

The presence of a transrenal aortic endograft did not affect the outcome of the renal artery revascularization procedure in this cohort. Renal artery stenting in the presence of transrenal abdominal aortic endografts appears to be a safe procedure without adverse effect on renal artery stent patency or renal function.

The Mid-term Effect of Bare Metal Suprarenal Fixation on Renal Function Following Endovascular Abdominal Aortic Aneurysm Repair

OBJECTIVE

The aim of this study was to assess the mid term effect of proximal bare metal fixation design on renal function in patients undergoing endovascular repair (EVR) of abdominal aortic aneurysm (AAA).

METHODS

Consecutive EVR patients for AAA from December 1995-2001 were included and grouped to either infrarenal (Group 1) or uncovered suprarenal (Group 2) fixation. Peri-operative renal function and at 6, 12 and 24 months was determined by serum creatinine (sCr mmol l(-1)) and Cockroft-Gault creatinine clearance (CrC ml min(-1)). Changes in renal function were compared using non-parametric analysis.

RESULTS

Of the 179 EVR procedures during this six-year period, paired renal data was available for 135 patients at a minimal follow-up of 6 months (Gp1, n = 63; Gp2, n = 72). Median pre-EVR sCr and CrC were 113, 57 in Group 1 and 108, 58 in Group 2, p = NS. There was no significant deterioration in renal function within or between either group at 2 years post-EVR: median sCr, CrC values were 118, 56 (Group 1) and 111, 56 (Group 2), all p = NS.

CONCLUSION

This study suggests mid-term renal function remains unaffected following EVR of AAA, irrespective of proximal fixation type. Designs to improve stent durability and EVR applicability do not appear to compromise renal function.

Does N-Acetylcysteine Prevent Contrast-Induced Nephropathy During Endovascular AAA Repair? A Randomized Controlled Pilot Study

PURPOSE

To examine if N-acetylcysteine (NAC) reduces the incidence of contrast nephropathy during endovascular abdominal aortic aneurysm repair (EVAR) as evidenced by changes in markers of renal function.

METHODS

Twenty consecutive men (mean age 72 years, range 65-79) undergoing EVAR were randomized to receive standard intravenous fluid hydration or standard fluid hydration and NAC (600 mg BID orally, 4 doses). Venous blood and urine were collected prior to the procedure and for 5 postoperative days and analyzed blindly for serum creatinine, urinary retinol-binding protein (RBP), and albumin/creatinine ratio (ACR).

RESULTS

There were no significant differences in baseline demographics between the groups. No patient developed acute renal failure. In both groups, urinary RBP rose significantly from baseline (median 15 microg/mmol to peak 699 microg/mmol in controls versus 17 to 648 microg/mmol in the treatment group, p<0.003). There were similar significant rises in ACR (p<0.02). There was, however, no significant difference in the postoperative RBP or ACR between the groups at any time point.

CONCLUSION

EVAR causes significant acute renal injury in most patients. This was not attenuated by N-acetylcysteine. The causes of renal injury are probably multifactorial, the long-term clinical significance of which is unclear.

Endovascular Aneurysm Repair Alters Renal Artery Movement: A Preliminary Evaluation Using Dynamic CTA

PURPOSE

To observe the natural renal artery motion during cardiac cycles in patients with abdominal aortic aneurysm (AAA) and how the implantation of stent-grafts may distort this movement.

METHODS

Data on 29 renal arteries from 15 male patients (mean age 72.6 years, range 66-83) treated with Talent or Excluder stent-grafts were acquired using an electrocardiographically (ECG)-gated dynamic 64-slice CT scanner. ECG-triggered retrospective reconstructions were made at 8 equidistant time points over the R-R cardiac cycle. The gated datasets were reconstructed perpendicular to the center flow lumen of each renal artery at 1.2 and 2.4 cm from the renal ostium. Center of mass displacement was determined per cardiac cycle for pre- and post-EVAR renal arteries and compared.

RESULTS

Normal renal artery motion in AAA patients was impressive, with up to 3-mm movement both near and distant from the aorta (mean 2.0+/-0.6 mm, range 1.1-3.0). EVAR inhibited proximal renal motion, resulting in a 31% decrease in maximal movement (mean 1.4+/-0.7 mm, range 0.7-2.0; p < or = 0.05). Distal renal artery motion was unaffected by EVAR, with motion similar to the pre-EVAR state.

CONCLUSION

ECG-gated dynamic CTA is feasible on a 64-slice scanner with a standard radiation dose and can detect potentially serious consequences of EVAR. EVAR alters renal artery motion by limiting proximal motion while leaving distal motion unaffected.

The impact of aortic endografts on renal function

OBJECTIVE

To determine the impact on late postoperative renal function of suprarenal and infrarenal fixation of endografts used to treat infrarenal abdominal aortic aneurysm (AAA).

METHODS

Retrospective analysis of 277 patients treated from 2000 to 2003 with three different endografts at two clinical centers. Five patients on dialysis for preoperative chronic renal failure were excluded. Group IF of 135 patients treated with an infrarenal device (Medtronic AneuRx) was compared with group SF of 137 patients treated with a suprarenal device (106 Cook Zenith and 31 Medtronic Talent). Renal function was evaluated by calculating preoperative and latest postoperative creatinine clearance (CrCl) using the Cockcroft formula. Patients who developed a >20% decrease in CrCl were considered to have significantly impaired renal function.

RESULTS

There were no significant differences in patient age, sex, aneurysm size, preoperative risk factors, dose of intra- and postoperative contrast, or baseline CrCl (IF: 69.3 mL/min, SF: 71.7 mL/min, P = .4). Follow-up time of 12.2 months was the same in both groups. CrCl decreased significantly during the follow-up period in both groups (IF: 69.3 mL/min to 61.7 mL/min, P < .01; SF: 71.7 mL/min to 64.9 mL/min, P < .03). Postoperative CrCl (IF: 61.7 mL/min, SF: 64.9 mL/min, P = .3), and the rate of CrCl decrease during the follow-up period (IF: -10.9%, SF: -9.5%, P = .2) was not different between the two groups. The number of patients with a >20% decrease in CrCl was not different between the two groups (IF: n = 35 [25.9%], SF: n = 41 [29.9%], P = .46). However, the magnitude of decrease in CrCl in patients with renal impairment was greater in patients treated with suprarenal fixation endografts (SF: -39%) compared with those treated with infrarenal endografts (IF: -31%, P = .005). This greater degree of renal impairment was not due to identifiable differences in preoperative risk factors, age, or baseline CrCl. No patients in these series required dialysis.

CONCLUSIONS

Regardless the type of endograft used, there is a 10% decrease in CrCl in the first year after endovascular aneurysm repair. Suprarenal fixation does not seem to increase the likelihood of postoperative renal impairment. Decline in renal function over time after endovascular aortic repair is probably due to multiple factors, and measures known to be effective in protecting kidneys should be considered for these patients. Long-term follow-up with measurement of CrCl, along with renal imaging and regular blood pressure measurements, should be performed to detect possible late renal dysfunction. Prospective studies comparing suprarenal versus infrarenal fixation are needed to confirm those results.

The Management of Abdominal Aortic Aneurysms in Patients with Concurrent Renal Impairment

INTRODUCTION

Patients with concurrent renal impairment and abdominal aortic aneurysms present a significant challenge in terms of pre-operative, intra-operative and post-operative management. This aim of this review was to determine the risks of surgery in this patient group and determine whether any clear management strategies exist to enhance their clinical management.

METHODS

Systematic review of published literature giving details of the outcome of open or endovascular abdominal aortic aneurysm repair in patients with pre-operative renal impairment. Papers concerning the management of post-operative acute renal failure in patients with normal pre-operative renal function has not been included.

RESULTS

There is little data regarding patients with end-stage renal failure and AAA although these patients appear to have a high peri-operative mortality rate. In contrast, those with renal impairment do not have a significantly higher mortality rate than those with normal renal function, rather they have a higher risk of complications associated with surgery and may require more intensive post-operative organ system support than normal patients. Many have a transient deterioration in renal function in the immediate peri-operative period that will resolve. In the case of patients with ruptured AAA, it is not clear whether pre-operative renal impairment affects mortality.

Single Center Experience with a New Commercially Available Thoracic Endovascular Graft

PURPOSE

To evaluate the intra-operative performance and clinical outcome of a new commercially available stent-graft for the treatment of thoracic aortic diseases.

METHODS AND PATIENTS

From January 2003 to October 2004, 45 consecutive patients received endovascular treatment with the Zenith TX1 device for diseases of the thoracic aorta at a single center in northern Italy. Indications included disease of the descending thoracic aorta in 26 cases, of the aortic arch in 17 cases and of the thoraco-abdominal aorta in two cases. We treated 38 atherosclerotic aneurysms, two post-traumatic aortic ruptures, two penetrating ulcers, two chronic dissections and one case was treated for aortic bleeding after voluntary acid ingestion for attempted suicide. General anesthesia was used in 20 cases. Combined or hybrid endovascular and open surgical repair was performed in 11 patients. Mean follow-up was 7 months (range 1-22 months).

RESULTS

Technical success was obtained in 44 patients (98%). One primary type I endoleak occurred (2%). ICU was used in 12 cases with a mean stay of 1 day. The mean hospital stay was 6 days (range 4-13 days). There were no hospital deaths or strokes but one transient paraplegia (2%). A type II endoleak was observed in one case and resolved spontaneously 1 month later. No aneurysm enlargement, endograft migration or structural failures were observed during follow-up. Two late unrelated-deaths were observed.

CONCLUSIONS

This stent-graft does not fulfill all the characteristics of the ideal graft, however, it proved to be safe and allowed satisfactory short term results in this group of patients treated at a single center.

Cross-sectional area reduction of the aortic ostium by suprarenal stent wires: in vitro phantom study by CT virtual angioscopy

The study aims to investigate the reduction of cross-sectional area of the aortic ostium by the presence of aortic stent wires observed using CT virtual angioscopy in an aorta phantom. A human aorta phantom was built with a commercial stent graft placed in situ to simulate a repaired aortic aneurysm. Virtual angioscopic images of the aortic ostium and stent wires were generated in the locations of renal arteries, superior mesenteric artery and corresponding cross-sectional area reduction caused by stent wires was measured by virtual angioscopy in various scanning parameters. Our study showed that cross-sectional area reduction of the aortic ostium was determined by the diameter of renal ostium and stent wires, as well as the number of stent wires crossing the aortic ostium.

Suprarenal fixation of endograft in abdominal aortic aneurysm treatment: focus on renal function

OBJECTIVE

The objective of this work was to evaluate any variation of renal function detected by renal scintigraphy after the suprarenal fixation of endografts for abdominal aortic aneurysm (AAA) repair.

SUMMARY BACKGROUND DATA

In the few articles that have considered this problem, renal function was evaluated only by biochemical tests, which are inadequate in demonstrating small changes in renal function and in appreciating the worsening of a single kidney's function.

METHODS

Between April 1999 and May 2002, 47 patients with an inappropriate infrarenal proximal neck had a suprarenal fixation for AAA. To assess renal function, a technetium-99m diethylene triamine penta-acetic acid (TC-DTPA) perfusion scintigraphy was performed preoperatively on the third postoperative day and at 6, 12 months, and then yearly thereafter. Worsening of renal function was defined as a decrease of glomerular filtration rate (GFR) > or =20% (detected with Gates method). Serum creatinine level was tested preoperatively and at the first and third postoperative day.

RESULTS

Endograft deployment was technically successful in 44 patients (93.6%); clinical perioperative success was obtained in 46 patients (97.8%). In 12 patients (25.5%), a permanent reduction of the GFR was observed using postoperative TC-DTPA perfusion scintigraphy. By 99m TC-DTPA perfusion scintigraphy, a permanent reduction of GFR was observed postoperatively in 12 patients. A slight GFR reduction (<20%) was present in 7 (14.9%) patients, due to the planned occlusion of accessory renal arteries. A more significant GFR reduction (>20%) was present unexpectedly in 5 (10.6%) patients, in 3 of these a single kidney was involved, in 5 both with an increase of the serum creatinine level >20%.

CONCLUSIONS

Suprarenal fixation of endografts in AAA treatment is a safe procedure with good early and midterm procedural results and a risk of GFR impairment (>20%) of 10.6%.

Treatment of short-necked infrarenal aortic aneurysms with fenestrated stent-grafts: short-term results

INTRODUCTION

A proximal neck of 15 mm length is usually required to allow endovascular repair of abdominal aortic aneurysms (EVAR). Many patients have been refused EVAR due to a short neck. By customising fenestrated grafts to the patients' anatomy, we can offer an endovascular solution, especially for patients who are unsuitable for open repair.

METHODS

Eighteen patients were selected for fenestrated stent-grafting if they presented with an abdominal aneurysm of at least 55 mm in diameter, a short neck (less than 15 mm), plus contra-indications for open repair (cardiopulmonary impairment or a hostile abdomen). The stent-graft used was a customised fenestrated model based on the Cook Zenith composite system. We used additional stents to ensure apposition of the fenestrations with the side branches.

RESULTS

All endovascular procedures were successful. Out of the 46 targeted side branches (10 superior mesenteric arteries, 36 renal arteries), 45 were patent at the end of the procedure. One accessory renal artery became occluded by the stent-graft. There was one possible proximal type I endoleak, which later proved to be a type II endoleak. There was no mortality, but complications occurred in six patients: two cardiac complications, three urinary complications and one occlusion of a renal artery. At follow-up (mean 9.4 months, range 1-18), there were no additional renal complications and all the remaining targeted vessels stayed patent.

DISCUSSION

By customizing fenestrated stent-grafts, it is possible to position the first covered stent completely inside the proximal neck, thus achieving a more stable position. The additional side-stents may also contribute to a better fixation. This technique may become a valuable alternative for patients who are at high risk from open surgery.

Relationship of proximal fixation to postoperative renal dysfunction in patients with normal serum creatinine concentration

OBJECTIVES

This study was performed to determine whether there is deterioration in renal function during follow-up in patients who have undergone endovascular aneurysm repair (EVAR), as recommended by the device manufacturers; to determine whether suprarenal fixation correlates with impairment of renal function; and to explore the potential implication of life-long surveillance of renal function with contrast-enhanced computed tomography.

METHODS

One hundred forty-six consecutive patients underwent EVAR at our institution. Data from 113 of these patients who were free from preoperative renal insufficiency or postoperative renal disease were analyzed. Fifty-three patients received infrarenal (IR) fixation devices, and 60 patients received suprarenal (SR) fixation devices. All SR fixation devices were placed under investigational device exemption protocols. The average follow-up was 688 days. Sixty-five consecutive patients who had undergone open repair of an abdominal aortic aneurysm (AAA) served as the control group.

RESULTS

Preoperative creatinine concentration, intraoperative blood loss, contrast volume, and number of contrast-enhanced procedures were not significantly different between the IR and SR groups. Two renal artery occlusions (1 SR, 1 IR; P=NS) were identified, and 8 renal infarcts (5 SR, 3 IR; P=NS). There was an increase in mean creatinine concentration in the open AAA, IR, and SR fixation groups at each time point in the analysis. Mean elevation in creatinine concentration at 12, 24, and 36 months was 0.10, 0.10, and 0.04 mg/dL, respectively, for open AAA repair; 0.20, 0.21, and 0.28 mg/dL for IR fixation; and 0.15, 0.21, and 0.12 mg/dL for SR fixation. At life table analysis, renal impairment at 36 months was seen in 36% +/- 9% of patients in the IR group, 25% +/- % of patients in the SR group, and 19% +/- 6% of patients in the open AAA group (P=.04 for IR fixation vs open AAA repair).

CONCLUSIONS

A decrease in kidney function is seen after EVAR, regardless of fixation level, that is independent of renal disease and renal arterial occlusion. In patients with normal renal function the site of proximal fixation does not affect postoperative creatinine concentration. The decrease in renal function is likely related to the repetitive administration of contrast agent.

Does transrenal fixation of aortic endografts impair renal function?

OBJECTIVES

Transrenal fixation (TFX) of aortic endografts is thought to increase the risk for renal infarction and impaired renal function. We studied the late effects of TFX on renal function and perfusion.

METHODS

Of 189 patients with commercial aortic endografts, which we inserted between 1995 and 2002, we reviewed data for 130 patients (112 men, 18 women) with available creatinine (Cr) concentration and contrast enhanced computed tomography (CT) scans preoperatively and 1 to 97 months after the procedure. Of the 130 patients, 69 patients had TFX and 61 patients had infrarenal fixation (IFX). Both groups were physiologically comparable. Average age was 76 +/- 8 years for patients with TFX and 75 +/- 8 years for patients with IFX. Presence of renal infarct or renal artery occlusion was determined by nephrograms on serial contrast-enhanced CT scans.

RESULTS

Mean follow-up was 17 +/- 16 months (range, 1-54 months) for TFX and 21 +/- 21 months (range, 1-97 months) for IFX. Mean serum Cr concentration increased significantly during long-term follow-up in both groups (TFX, 1.3 +/- 0.5 mg/dL to 1.5 +/- 0.8 mg/dL, P <.01; IFX, 1.3 +/- 0.7 mg/dL to 1.4 +/- 0.8 mg/dL, P <.03). Creatinine clearance (CrCl) similarly decreased over long-term follow-up in both groups (TFX, 53.3 +/- 17.7 mL/min/1.73 m(2) to 47.9 +/- 16.2 mL/min/1.73 m(2), P <.01; IFX, 58.1 +/- 22.7 mL/min/1.73 m(2) to 53.1 +/- 23.4 mL/min/1.73 m(2), P <.02). There were no significant differences in the increase in Cr concentration (P =.19) or decrease in CrCl (P =.68) between TFX and IFX groups. Small renal infarcts were noted in four patients (5.8%) in the TFX group and one patient (1.6%) in the IFX group. No increase in Cr concentration or decrease in CrCl was noted in any patient with a renal infarct. Postoperative renal dysfunction developed in 7 of 69 patients (10.1%) in the TFX group and 7 of 61 patients (11.5%) in the IFX group. There were no statistically significant differences between groups with respect to number of patients with new renal infarcts (P =.37) or postoperative renal dysfunction (P =.81).

CONCLUSION

There is a slight increase in serum Cr concentration and decrease in CrCl after aortic endografting. However, there was no significant difference in these changes between patients with TFX and IFX. Although TFX may produce a higher incidence of small renal infarcts, these do not impair renal function. Thus our midterm results suggest that TFX can be performed safely, with no greater change in renal function than observed after IFX.

The Zenith AAA endovascular graft for abdominal aortic aneurysms: clinical update

PURPOSE

The aim of this study was to provide an update regarding the US clinical trial assessing the performance of the Zenith AAA Endovascular Graft in the treatment of abdominal aortic aneurysms.

MATERIALS AND METHODS

A prospective, nonrandomized, concurrent control-based study design was used to contrast conventional repair of infrarenal aneurysms with endovascular repair in patients that would otherwise be candidates for open surgical procedures. Additional study arms allow high-physiologic-risk patients and roll-in patients to be treated using the same endovascular device in a registry format. Patients were evaluated clinically and radiographically computed tomography (CT) and abdominal radiographs) before any intervention, at hospital discharge, 30 days, 6 months, 12 months, and yearly thereafter. Data were analyzed with the intent of assessing acute and chronic morbidity and mortality, radiographic parameters indicative of successful aneurysm repair, and device integrity.

RESULTS

A total of 352 patients were treated with the Zenith graft (one patient did not receive an implant in the standard-risk group), and 80 patients underwent conventional surgical repair. Two hundred patients were enrolled in the standard-risk group, 100 in the high-risk group, and 52 underwent endovascular repair as roll-in patients. All cause mortality, aneurysm-related deaths, and ruptures were statistically identical between the groups. Procedural morbidity was significantly lower for patients treated with endovascular grafts with respect to cardiac, pulmonary, renal, and vascular complications. Secondary interventions were more commonly required in the endovascular group. The endoleak rate was 4.9% at 12 months in the standard-risk endovascular group. There was one rupture in the high-risk subset of patients and 3 elective conversions. A total of 1.6% of the endovascular patients were noted to have a barb separation without evidence of significant migration or clinical events. No other device integrity issues were observed.

CONCLUSIONS

The safety of the Zenith endovascular graft was superior to conventional management with respect to morbidity and clinical utility. The short-term device efficacy was satisfactory; however, longer-term follow-up will be necessary to establish the duration of this observation.

Effect of suprarenal versus infrarenal aortic endograft fixation on renal function and renal artery patency: a comparative study with intermediate follow-up

PURPOSE

Suprarenal fixation of aortic endografts appears to be a safe option in patients with a short or conical proximal aortic neck. However, concern persists regarding the long-term effect on renal function when renal artery ostia are crossed by the uncovered stent. We investigated the effect of suprarenal versus infrarenal endograft fixation on renal function and renal artery patency after endovascular aortic aneurysm repair.

METHODS

Records of 91 patients who underwent endovascular aortic aneurysm repair with a modular bifurcated stent graft between November 1999 and January 2002 were reviewed retrospectively. Two patients receiving dialysis because of chronic renal failure were excluded. Infrarenal fixation was used in 57 patients (group 1), and suprarenal fixation was used in 32 patients (group 2). In two patients in group 1 a Gianturco Z stent was inserted transrenally because of intraoperative proximal type I endoleak, and data for these patients were excluded from analysis. Follow-up evaluation was performed at 1, 6, and 12 months, and yearly thereafter, and included clinical assessment, measurement of serum creatinine concentration (SCr), and computed tomography angiography, per standard protocol. Median follow-up was 12 months (range, 1-36 months).

RESULTS

There was no statistically significant difference in patient demographic data, aneurysm size, or preoperative risk factors. Median SCr was significantly higher in group 2 (suprarenal fixation) than in group 1 (infrarenal fixation) preoperatively (1.2 mg/dL [range, 0.6-2.3 mg/dL] vs 0.9 mg/dL [range, 0.6-1.9 mg/dL], P =.008) and at 1 month postoperatively (1.1 mg/dL [range, 0.8-5.6 mg/dL] vs 1.0 mg/dL [range, 0.6-2.1 mg/dL], P =.045). There was a significant increase in median SCr in both groups at 1 month postoperatively (group 1, 1.0 mg/dL [range, 0.6-2.1 mg/dL], P =.05; group 2, 1.1 mg/dL [range, 0.8-5.6 mg/dL] [mean SCr, 1.35 mg/dL vs 1.15 mg/dL, respectively], P <.05). In group 1 SCr was increased significantly at 6 and 12 months (P <.001), whereas in group 2 SCr also increased at 6 and 12 months, but not significantly. The change in SCr over time was not significantly different between the two groups. In two of 32 patients in group 2, renal artery occlusion developed, associated with perfusion defects in renal parenchyma and persistently elevated SCr. Analysis of renal artery patency did not demonstrate any association between patency and treatment. No patient developed hypertension during follow-up.

CONCLUSIONS

Suprarenal endograft fixation does not lead to significant renal dysfunction, and renal artery occlusion is uncommon within 12 months. A larger study with longer follow-up is essential to determine overall effects on renal function and renal artery patency.

Long-term renal function following endovascular aneurysm repair with infrarenal and suprarenal aortic stent-grafts

PURPOSE

To determine in a retrospective analysis the incidence of renal impairment (RI) following endovascular repair (EVR) of abdominal aortic aneurysm (AAA), to assess the morbidity and mortality in endograft patients with preoperative RI, and to examine the impact of suprarenal stent-grafts on renal function.

METHODS

From March 1994 to October 2001, 315 AAA patients (289 men; mean age 72.4+/-7.0 years) undergoing EVR were entered prospectively into a vascular registry. The patients received either an in-house custom-made stent-graft or one of several commercially made devices implanted with infrarenal or suprarenal fixation. Renal function was monitored by serum creatinine measurements prior to discharge and at 3, 6, and 12 months and annually thereafter. Preoperative RI was defined as a serum creatinine >130 micro mol/L and/or long-term dialysis. Postoperative RI referred to a >20% increase in the serum creatinine over baseline. Additional deterioration of renal function in patients with preoperative RI was referred to as postoperatively worsened RI.

RESULTS

Of the 315 patients treated, 220 (69.8%) were considered high risk (ruptured AAA or ASA grade III or IV). Sixty-nine (21.9%) patients had preoperative RI (6 [1.9%] on preoperative dialysis). A suprarenal stent-graft was used in 169 (53.7%) patients and infrarenal stent-graft in the remaining 146 (46.3%). The mean follow-up was 30.1+/-22.7 months. Postoperative RI occurred in 53 (16.8%) patients (24 [7.6%] transient, 29 [9.2%] persistent). Patients with preoperative RI had a significantly higher incidence of postoperatively worsened RI (37.7% versus 11.0%, p<0.0001) and a higher mortality related to RI (7.2% versus 1.6%, p=0.02). Suprarenal fixation had no influence on the incidence of RI, on perioperative mortality, or on mortality related to RI. The only significant predictive factor of postoperative RI was preoperative RI (risk ratio 5.09, 95% CI 2.38 to 10.87, p=0.0001).

CONCLUSIONS

Endovascular AAA repair may lead to persistent postoperative RI in nearly 10% of cases, especially in patients with preoperative RI. Suprarenal stent-graft fixation does not seem to have any deleterious effect on renal function. Further long-term studies are required to confirm the innocuous nature of transrenal stent placement.

Transrenal fixation of endovascular stent-grafts for infrarenal aortic aneurysm repair: mid-term results

PURPOSE

We evaluated mid-term results of a single-center consecutive series of endovascular stent-grafts implanted for aortic aneurysm repair with transrenal fixation, to determine clinical outcome, aneurysm anatomy, renal artery patency, and renal complications.

METHODS

Modular stent-grafts were placed with transrenal fixation in 37 patients between November 1998 and July 2000. Follow-up evaluation included clinical examination, laboratory evaluation of serum creatine concentration, computed tomographic angiography, and renal duplex scanning.

RESULTS

Thirty-seven patients underwent transrenal fixation of aortic stent-grafts as part of a Phase II US Food and Drug Administration study. Two patients subsequently underwent follow-up at institutions closer to their homes, and thus provided clinical information but no long-term renal or aneurysm morphologic data. There were no perioperative deaths. Five patients died during follow-up, at a mean of 9 months, because of myocardial infarction in 4 patients and respiratory failure in 1 patient. Thirty patients, ages 75 +/- 8 years, have been followed up for 28.5 +/- 7.2 months. Aneurysm diameter at follow-up was 5.0 +/- 0.8 cm, compared with 5.7 +/- 0.8 cm preoperatively. In 5 patients, endoleak developed during follow-up: 1 type I leak was treated with an aortic cuff, with temporary stabilization of the aneurysm and correction of the endoleak; 2 type II endoleaks were treated with translumbar coil embolization, and 1 resolved spontaneously; and 1 type III endoleak was treated with a combination of coil embolization and stent-graft extension to cover a graft defect. Preoperatively, serum creatinine concentration was normal in 23 patients, but increased persistently in 2 patients and was abnormal in 7 patients. Postoperatively, creatine concentration increased in 4 patients to greater than 20% of baseline level. Seventeen patients had no evidence of renal artery stenosis, compared with 13 patients with renal artery stenosis. Of 41 normal renal arteries, 90% remained unchanged, 1 became occluded, 3 demonstrated 60% stenosis. Nephrectomy was necessary in 1 patient because of cancer. Of 19 abnormal renal arteries, progression of disease was noted in 3 arteries.

CONCLUSIONS

Transrenal fixation of aortic stent-grafts can be performed with acceptable mid-term outcome with respect to mortality, need for follow-up intervention, and aneurysm exclusion with protection from rupture. Postprocedural stenosis can develop in both normal and abnormal renal arteries. Rate of progression of disease was greater in patients with preprocedural renal dysfunction compared with patients with normal renal arteries. This is merely an observation, and may not be related to transrenal fixation. Long-term follow up is needed.

Transrenal versus infrarenal endograft fixation: influence on type I endoleaks

The purpose of this study was to compare the rate of proximal type I endoleaks in patients undergoing endoluminal repair of infrarenal abdominal aortic aneurysms with endografts having either transrenal or infrarenal fixation. From September 1998 to May 2000, 42 patients received endoluminal aortic grafts for the treatment of infrarenal abdominal aortic aneurysms. Patients received either transrenal or infrarenal devices, based on the surgeon's preference. All patients had infrarenal aortic neck lengths measuring at least 1.5 cm and proximal neck angulation of <60 degrees. The endoluminal grafts were oversized by 10-20% relative to the diameter of the infrarenal aorta. The presence of endoleaks was determined at the initial procedure by contrast angiography and during subsequent follow-up at 1 month and 3 months by CT scan or duplex ultrasound. No significant differences in the rate of proximal type I endoleaks can be demonstrated between transrenal and infrarenal device types in this small cohort. Proper patient selection is more important than type of proximal fixation in preventing endoleaks.