Endovascular Aneurysm Repair versus Open Aneurysm Repair: Comparison of Treatment Outcome and Procedure-Related Reintervention Rate

We conducted a retrospective study to compare treatment outcome and procedure-related reintervention rates of endovascular aneurysm repair (EVAR) with those of open repair. Clinical and radiological data of patients treated at the Rijnstate Hospital (Arnhem, The Netherlands) for nonsymptomatic aortic abdominal aneurysm during October 1998-January 2004 were reviewed and analyzed for demographic data, aneurysm specifics, comorbid condition status, and perioperative outcome. There were 99 patients treated with EVAR and 116 patients treated with open repair. Significant differences in age were seen between treatment groups, patients under the age of 80 being more likely to have open repair (p < 0.004). The EVAR group consisted of significantly fewer women (p < 0.029). Of seven comorbid conditions, four reached significant differences between treatment groups; patients with ischemic heart disease (p < 0.044), heart failure (p < 0.006), renal failure (p < 0.033), or peripheral arterial disease (p < 0.006) were more likely to have EVAR. Comparison of aneurysm anatomy showed no difference in size between EVAR (mean 57.7 mm, 95% CI 55.9-59.5 mm) and open repair (mean 60.1 mm, 95% CI 57.9-62.3 mm). Significant differences were seen in aneurysm neck length and diameter. Operative outcome showed differences in length of hospital stay (median, EVAR 7 vs. open repair 11 days), 30-day mortality (p < 0.048), postoperative hematoma (p < 0.001), and postoperative pulmonary infections (p < 0.001), all in favor of EVAR. Follow-up of the EVAR group showed a decrease (mean 10 mm, 95% CI 7-14 mm) of aneurysm diameter in 15% of cases during follow-up (mean 18 months, range 1-66). Despite higher age and more comorbidity of patients undergoing EVAR, 30-day mortality, postoperative pulmonary infection rate, and length of hospital stay were lower than for those undergoing open repair. Both EVAR and open repair can be performed on a subset of patients with low mortality, complication, and reintervention rates.

Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms

BACKGROUND

Two randomized trials have shown better outcomes with elective endovascular repair of abdominal aortic aneurysms than with conventional open repair in the first month after the procedure. We investigated whether this advantage is sustained beyond the perioperative period.

METHODS

We conducted a multicenter, randomized trial comparing open repair with endovascular repair in 351 patients who had received a diagnosis of abdominal aortic aneurysm of at least 5 cm in diameter and who were considered suitable candidates for both techniques. Survival after randomization was calculated with the use of Kaplan-Meier analysis and compared with the use of the log-rank test on an intention-to-treat-basis.

RESULTS

Two years after randomization, the cumulative survival rates were 89.6 percent for open repair and 89.7 percent for endovascular repair (difference, -0.1 percentage point; 95 percent confidence interval, -6.8 to 6.7 percentage points). The cumulative rates of aneurysm-related death were 5.7 percent for open repair and 2.1 percent for endovascular repair (difference, 3.7 percentage points; 95 percent confidence interval, -0.5 to 7.9 percentage points). This advantage of endovascular repair over open repair was entirely accounted for by events occurring in the perioperative period, with no significant difference in subsequent aneurysm-related mortality. The rate of survival free of moderate or severe complications was also similar in the two groups at two years (at 65.9 percent for open repair and 65.6 percent for endovascular repair; difference, 0.3 percentage point; 95 percent confidence interval, -10.0 to 10.6 percentage points).

CONCLUSIONS

The perioperative survival advantage with endovascular repair as compared with open repair is not sustained after the first postoperative year.

Sexual Dysfunction After Conventional and Endovascular AAA Repair:Results of the DREAM Trial

PURPOSE

To assess sexual function in the first postoperative year after elective endovascular aneurysm repair (EVAR) and open repair (OR) of abdominal aortic aneurysm (AAA).

METHODS

In the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial, 153 patients (141 men; mean age 71 years, range 53-85) were randomly allocated to EVAR (n=77) or OR (n=76). Sexual functioning was evaluated preoperatively and at 5 times in the first postoperative year (3, 6, 13, 26, and 52 weeks) using a questionnaire derived from the Medical Outcomes Study. The proportions of patients reporting sexual dysfunction for any of 5 aspects (interest, pleasure, engagement, orgasm, and erection) and any increase in the magnitude of dysfunction were compared between EVAR and OR.

RESULTS

Preoperatively, the proportion of patients reporting sexual dysfunction in at least 1 aspect was 66% for the OR group and 74% in the EVAR group (p=NS). Surgery had a clear impact on sexual dysfunction. The proportion of patients reporting sexual dysfunction on at least 1 aspect increased to 79% in the OR group and 82% in the EVAR group. The magnitude of sexual dysfunction increased in both groups on all 5 aspects at 3 weeks postoperatively, but this was more pronounced in the OR group (interest: OR p=0.038 vs. EVAR p=0.071; pleasure: OR p=0.009 vs. EVAR p=0.065; engagement: OR p=0.006 vs. EVAR p=0.054; orgasm OR p=0.023 vs. EVAR p=0.112, and erection: OR p=0.046 vs. EVAR p=0.030). At 6 weeks, the OR group still reported a significant increase in 3 aspects (pleasure p=0.031, engagement p=0.010, and orgasm p=0.003), whereas the EVAR group no longer showed a significant difference. From 3 months on, both groups had returned to baseline.

CONCLUSIONS

EVAR and open elective AAA repair both have an impact on sexual function in the early postoperative period. After EVAR, recovery to preoperative levels is faster than after open repair, but at 3 months, sexual dysfunction levels are similar in both groups.

Application of a clinical grade CD34-mediated method for the enrichment of microvascular endothelial cells from fat tissue

BACKGROUND

Microvascular endothelial cells (MVEC) derived from s.c. fat are seeded on vascular grafts to prevent early occlusion. We have demonstrated the presence of contaminating cells contributing to MVEC seeding-related intimal hyperplasia in MVEC isolates from fat tissue. We found that cell isolates additionally purified after the isolation process, were associated with a reduced thrombogenicity and development of intimal hyperplasia in vitro. A combination of 11Fibrau (F11)- and CD14-coated Dynabeads was used to deplete the contaminating cells, fibroblasts, and monocytes/macrophages. Unfortunately, clinical-grade F11 is not available, and thus cannot be used for clinical practice. CD34 selection with clinical-grade products is widely used for the isolation of hematopoietic progenitors, and endothelial cells (EC) express CD34 on their surfaces. The aims of this study were to test the effectiveness of two different CD34-selection techniques for purification of MVEC, and to compare the results with those of the F11/CD14-method.

METHODS

Liposuction fat was enzymatically digested and centrifuged twice to remove adipocytes and collagenase. CD34 selection was performed using the commercially available methods from Nexell or Miltenyi. Both techniques were modified for our use. The purity after isolation and culture, and recovery were determined by flow-cytometry (CD31-expression) and compared with that of cells purified with the F11/CD14-method.

RESULTS

Besides MVEC, the contaminating fibroblasts and macrophages/monocytes weakly expressed the CD34 Ag. Enrichment of MVEC was not successful with the Miltenyi method. Variations in neither the dose of Ab nor the use of direct selection and different separation programs improved the results. With the Nexell method, MVEC were enriched to 86%, a comparable purity to that obtained with the F11/CD14-method. However, a lower recovery was achieved with the Nexell method.

CONCLUSION

Enrichment of MVEC could be achieved with a modified protocol of the clinical grade CD34(+) selection method from Nexell, but not with the CD34 method from Miltenyi.

A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms

BACKGROUND

Although the initial results of endovascular repair of abdominal aortic aneurysms were promising, current evidence from controlled studies does not convincingly show a reduction in 30-day mortality relative to that achieved with open repair.

METHODS

We conducted a multicenter, randomized trial comparing open repair with endovascular repair in 345 patients who had received a diagnosis of abdominal aortic aneurysm of at least 5 cm in diameter and who were considered suitable candidates for both techniques. The outcome events analyzed were operative (30-day) mortality and two composite end points of operative mortality and severe complications and operative mortality and moderate or severe complications.

RESULTS

The operative mortality rate was 4.6 percent in the open-repair group (8 of 174 patients; 95 percent confidence interval, 2.0 to 8.9 percent) and 1.2 percent in the endovascular-repair group (2 of 171 patients; 95 percent confidence interval, 0.1 to 4.2 percent), resulting in a risk ratio of 3.9 (95 percent confidence interval, 0.9 to 32.9). The combined rate of operative mortality and severe complications was 9.8 percent in the open-repair group (17 of 174 patients; 95 percent confidence interval, 5.8 to 15.2 percent) and 4.7 percent in the endovascular-repair group (8 of 171 patients; 95 percent confidence interval, 2.0 to 9.0 percent), resulting in a risk ratio of 2.1 (95 percent confidence interval, 0.9 to 5.4).

CONCLUSIONS

On the basis of the overall results of this trial, endovascular repair is preferable to open repair in patients who have an abdominal aortic aneurysm that is at least 5 cm in diameter. Long-term follow-up is needed to determine whether this advantage is sustained.

Durability and Validity of a Remote, Miniaturized Pressure Sensor in an Animal Model of Abdominal Aortic Aneurysm

PURPOSE

To investigate whether a remote, miniaturized pressure sensor could maintain calibration and function through organized thrombus over an extended period in a porcine model of abdominal aortic aneurysm (AAA).

METHODS

Six adult pigs had an AAA surgically created and excluded. A sensor zeroed to atmospheric pressure was placed within the aneurysm sac and another within the suprarenal aorta of each animal. Pressure measurements were taken at the initial operation and then on a weekly basis over 2 months. The aortic sensors were correlated to an intra-arterial pressure catheter at the initial operation and at the time of sacrifice. Back-table sensor correlation with atmospheric pressure was done at the time of explantation.

RESULTS

Three animals died during the follow-up period. Five animals were available for 6-week follow-up, of which 3 survived for the complete 8-week protocol. Two of the surviving animals had an intra-aortic sensor. All 5 aneurysm sac sensors functioned throughout the experimental period. At the time of sacrifice, the sacs contained a large amount of organized thrombus in which the sac sensors were deeply embedded. The 3 aortic sensors also functioned throughout the course of the experiments. The pressures correlated within 5 mmHg to the catheter-based measurements taken at the initial operation and at the time of sacrifice. Comparison to atmospheric pressure revealed no calibration offset in any sensor.

CONCLUSIONS

This chronic implantation study demonstrates the durability of a remote, miniaturized pressure sensor within a surgically created aneurysm sac as well as the suprarenal aorta of a porcine AAA model. There was no calibration offset in any of the sensors, and they remained valid at explantation. We believe that this is further evidence of the potential applicability of this sensor for clinical use.

Suitability of 7 Aortic Stent-Graft Models for MRI-Based Surveillance

PURPOSE

To evaluate the magnetic resonance imaging (MRI) characteristics of commercially available stent-grafts used for abdominal aortic aneurysm repair.

METHODS

Seven endovascular grafts (AneuRx, Lifepath, Talent, Excluder, Zenith, Quantum LP, and Ancure) were suspended in a water bath containing gadolinium and scanned using a 1.5-T clinical MRI scanner. Two different scan techniques (T(1)-weighted spoiled gradient echo and spin echo) based upon a clinical MRI endograft surveillance protocol were used for each stent-graft. The scans were evaluated for susceptibility artifacts and radiofrequency (RF) shielding and caging artifacts.

RESULTS

For most endografts, the lumen and structures surrounding the endograft were well visualized. However, the ferromagnetic properties of the Zenith and Lifepath devices resulted in large susceptibly artifacts that obliterated the endograft lumen as well as adjacent structures. All fully supported grafts showed some amount of signal loss from the graft lumen caused by RF caging. For the Ancure graft, evaluation around the attachment sites might be problematic.

CONCLUSIONS

An MRI-based surveillance protocol appears to be a viable option for the AneuRx, Talent, Excluder, and Quantum LP stent-grafts.

Surveillance after Endovascular Aneurysm Repair: Diagnostics, Complications, and Associated Costs

The purpose of this study is to describe the diagnostic tests used, the complications that occurred the reinterventions performed, and the costs incurred after endovascular aneurysm repair. Retrospective review was performed of 77 consecutive individuals in whom endovascular aortic grafts had been successfully deployed. The series represents a single institution's experience with prospective application of a surveillance program using high-resolution CT scanning. Follow-up was available for all individuals. Mean interval of follow-up was 19.9 months (range 1-72 months), yielding a cumulative follow-up of 1540 months. There were no cases of aneurysm rupture. A total of 315 CT scans were performed during follow-up. On the basis of predetermined criteria, 28 interventions were performed in 21 patients. Indications for intervention included change in aneurysm sac volume (21 procedures), limb ischemia (5 procedures), and infection (2 procedures). Seven individuals were converted to open repair an average of 28.5 months after graft implantation (range 4-69 months). Twenty-one additional procedures were performed in 15 individuals after an average of 14.8 months (range 1-63 months). Cumulative risk of intervention and overall costs were estimated as a function time from implantation. Estimated costs at one and five years were 3631 dollars and 9729 dollars. The cumulative risk of intervention at one year was 7.2%. The frequency and cost of post-implantation procedures after endovascular aortic intervention are substantial. As longer follow-up becomes available, continued postoperative expenses may cancel out the already marginal cost STET benefits of EVAR benefits of EVAR.

The Impact of Endovascular Treatment on In-hospital Mortality Following Non-ruptured AAA Repair over a Decade: A Population Based Study of 16,446 Patients

OBJECTIVES

We hypothesised that over the past decade, the nation-wide outcome of infrarenal abdominal aortic aneurysm (AAA) repair has improved with the introduction of endovascular treatment. The aim of the study was to identify endovascularly-treated patients in a national registry and to assess the impact on in-hospital mortality of non-ruptured AAA repair, if any, after the introduction of endovascular repair.

MATERIALS AND METHODS

We retrospectively studied the nation-wide outcome of non-ruptured AAA repair over the past decade. Variables studied were age and gender of the patients, hospital size and type and the year in which treatment was performed and the outcome on in-hospital mortality. The in-hospital mortality of non-ruptured AAA repair in 16,446 patients in the 10-year period from 1991 to 2000 was 7.3% (6.2-8.2%). In the 15,589 (95%) patients that underwent conventional treatment, in-hospital mortality was 7.6% (7.0-8.1%), whereas in the endovascular group it was 1.9% (0.6-3.5%). In the multivariate analysis, age and endovascular repair were the most important independent predictors of in-hospital mortality.

CONCLUSION

With the limitations of a national registry aside, the introduction of endovascular aneurysm repair seems to have had a small but significant impact on in-hospital mortality following infrarenal AAA repair.

New post-imaging software provides fast and accurate volume data from CTA surveillance after endovascular aneurysm repair

PURPOSE

To quantify intra- and interobserver variabilities when measuring total aneurysm volume after endovascular aneurysm repair using the Vitrea 2 System and to compare it in terms of accuracy and processing time with the gold standard methods using the Easy Vision workstation.

METHODS

Total aneurysm volumes from 30 postendograft CTA datasets were randomly selected from a database consisting of approximately 400 CTA datasets recorded in 89 patients. The intra- and interobserver variabilities were measured on the Vitrea workstation by 2 investigators. The intermodality variability was calculated for the same measurements using the Easy Vision workstation. The differences of each pair of measurements were plotted against their mean, and the repeatability coefficient (RC) was calculated. The mean differences were also expressed as a percentage of the first measurements.

RESULTS

The intraobserver mean difference was 1.6 mL (1.4%) with an RC of 10.8 mL (10.1%) and the interobserver mean difference was -1.4 mL (-1.4%) with an RC of 11.7 mL (10.2%). The intermodality mean difference was 1.8 mL (2.0%) with an RC of 15.8 mL (11.1%). The Vitrea workstation required a median of 8 minutes (interquartile range 7-10) for 1 observer and 6 minutes (interquartile range 5-8) for the other to perform a complete volume segmentation of each patient dataset compared to an estimated average of 30 minutes using the Easy Vision workstation.

CONCLUSIONS

The Vitrea workstation provides fast and accurate volume data from spiral CTA follow-up of endovascular aneurysm repair. This software may enhance the acceptability of volume surveillance in daily practice.

In vivo transluminal microvascular endothelial cell seeding on balloon injured rabbit arteries

AIM

Seeding venous endothelial cells (EC) onto damaged vascular surfaces attenuates the development of intimal hyperplasia. Unlike venous EC, fat derived microvascular endothelial cells (MVEC) do not require a culture step to increase the yield. The authors investigated whether fat derived MVEC are suitable to reduce intimal hyperplasia after PTA.

METHODS

Five rabbits were subjected to percutaneous transluminal angioplasty (PTA) of both iliac arteries. One side was seeded transluminally with autologous perirenal fat derived MVEC, using a double balloon catheter. The contralateral side was sham seeded, and served as a control. Follow-up was 4 weeks. Another rabbit was used for a feasibility experiment. This rabbit was subjected to a 1-sided seeding procedure and was sacrificed after 1 week. In a 7th rabbit, a 1-sided PTA was transformed, and autologous labelled cells were injected in the distal aorta instead of seeded, follow-up was 1 week. Histological investigation was per-formed.

RESULTS

The MVEC seeded artery of the pilot experiment was patent. All sham seeded arteries (5) except for 1 were patent. The patent ones showed moderate intimal hyperplasia. MVEC seeding (5) resulted in occlusion twice. In the patent MVEC seeded arteries intimal hyperplasia was present in more extended form than in the sham seeded arteries. Both the patent MVEC- and sham-seeded arteries were covered with an EC layer. Injected labelled MVEC were not found again on the de-endothelialized artery.

CONCLUSION

In this study seeding of fat derived MVEC on damaged native arteries results in an increased development of intimal hyperplasia and a decreased patency. One of the reasons may be the presence of non-EC in the seeded cell population.

Matrix metalloproteinase inhibition reduces intimal hyperplasia in a porcine arteriovenous-graft model

BACKGROUND

The patency of arteriovenous (AV) polytetrafluoroethylene grafts for hemodialysis is impaired by intimal hyperplasia (IH) at the venous outflow tract. IH mainly consists of vascular smooth muscle cells, fibroblasts, and extracellular matrix proteins. Because matrix metalloproteinases (MMPs) are enzymes able to degrade extracellular matrix proteins such as elastin and collagen and also stimulate migration of vascular smooth muscle cells, we hypothesized that BB2983 (a broad-spectrum MMP inhibitor) could reduce IH in AV grafts.

METHODS

In 12 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein. Six pigs received the oral MMP inhibitor (MMPi), and six pigs served as a control. Four weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis. Quantification of elastin content was performed on Elastin von Gieson-stained sections.

RESULTS

At the venous outflow tract, IH was strongly inhibited after MMPi when compared with the control group (1.02 +/- 0.26 mm(2) vs 2.14 +/- 0.38 mm(2); P =.027). The medial area did not differ significantly. In the control group elastin density decreased compared with nonoperated veins. This decrease was not observed in the MMPi group (nonoperated, 6.3% +/- 0.4%; MMPi, 7.2% +/- 0.7% vs untreated, 3.6% +/- 0.5%; P =.0004). Outward remodeling of the vein was not influenced by MMP inhibition.

CONCLUSION

MMPi reduces IH formation at the venous outflow tract of AV grafts in pigs, probably by inhibiting elastin degradation. These data suggest that MMP inhibitors might be useful for minimizing IH in AV grafts, thus prolonging patency rates of AV grafts in patients on hemodialysis.

Quality of Life after Endovascular and Open AAA Repair. Results of a Randomised Triala

AIM

To compare the quality of life (QoL) in the first postoperative year after elective endovascular abdominal aortic aneurysm repair (EVAR) and open repair (OR) in a randomised study.

METHODS

In the Dutch Randomised Endovascular Aneurysm Management (DREAM) trial, patients are randomly allocated to EVAR or OR. QoL questionnaires (SF-36 and EuroQoL-5D) were sent to all patients preoperatively (PREOP) and at five time points in the first postoperative year (3W, 6W, 3M, 6M and 12M). Between November 1999 and August 2002, 153 patients (141 male; 12 female) were randomised (78 EVAR and 75 OR; one crossover from OR to EVAR). The EuroQoL-5D scores and the eight domains of the SF-36 for the two groups were compared using the Mann-Whitney test. Changes over time were analysed using the Wilcoxon sign test.

RESULTS

There were no statistically significant differences in baseline characteristics (age, gender and SVS risk factors). The preoperative QoL scores of the study group were similar to the QoL scores of the general population of the same age. After 3W the OR group showed a significant decrease on the EuroQol-5D (p=0.022) and in six of the eight SF-36 domains. The EVAR group also showed a significant decrease on the EuroQol-5D (p=0.004) and in 5 of the 8 domains of the SF-36. At 6W the EuroQol-5D had recovered to baseline in the OR group and the decreased domains of the SF-36 had partially recovered. In the EVAR group the EuroQol-5D and three of the five decreased SF-36 domains, had returned to baseline. From 6M on, the OR group reported a significantly higher score on the EuroQoL-5D than the EVAR group (p=0.045 (6M) and p=0.001 (12M)).

CONCLUSION

In the early postoperative period there is a small, yet significant QoL advantage for EVAR compared to OR. At 6 months and beyond, patients reported better QoL after OR than after EVAR.

[Endovascular treatment of 4 patients with a traumatic rupture of the thoracic aorta]

OBJECTIVE

To present our initial results with the endovascular treatment of traumatic rupture of the thoracic aorta.

DESIGN

Retrospective.

METHOD

Between April and October, 2002, 4 men between the ages of 22 and 46 were treated endovascularly for a traumatic rupture of the thoracic aorta. The diagnosis 'rupture of the thoracic aorta' was made on the basis of CT-angiography in all cases. In the first case, a thoracic Gore TAG-endoprosthesis (Gore & Associates; Den Bosch) was used, and in 3 cases a Talent-endoprosthesis (Medtronic AVG; Heerlen).

RESULTS

There was an average of 2.5 days (limits: 0-5 days) between admission and the placement of the endoprosthesis. There was one intra-operative complication in the form of a dissection of the right femoral artery when the endoprosthesis was inserted. In 3 cases, the left subclavian artery was occluded by the prosthesis. This had no negative consequences for the patients during the follow-up period (limits: 4-12 months). The CT-angiogram taken 3 months after the operation consistently showed a good position of the endoprosthesis with no signs of leakage.

CONCLUSION

For a limited follow-up period, the endovascular treatment of a traumatic rupture of the thoracic aorta has been shown to be safe and effective. The long term results must be awaited.

Fabric tears as a new cause of type III endoleak with ancure endograft

PURPOSE

We present two case reports of type IIIb endoleak. One was due to fabric erosion caused by placement of a stent (Wallstent; W. L. Gore & Associates, Flagstaff, Ariz) after endovascular aneurysm repair; the other arose spontaneously. In both cases, an Ancure endograft (Guidant/EVT, Menlo Park, Calif) was placed.

CASE REPORTS

In case 1, a large endoleak developed 36 months after uncomplicated endovascular treatment of an abdominal aortic aneurysm. In case 2, endoleak developed 30 months after a complicated procedure. In both cases, two Wallstents were used to treat type I endoleak and limb kinking in the first postoperative months. One type III endoleak was within the endograft at the level of the stents.

CONCLUSION

To our knowledge, these are the first type III endoleaks reported in association with Ancure endografts. Placement of Wallstents inside endografts is of concern, and another indication for close monitoring during follow-up.

Salvage of a difficult situation: method for conversion of failed endograft

Complications of endovascular aneurysm repair can be difficult to manage. One of the more difficult situations is conversion to open surgery because of a failed endograft. We describe a technique for conversion that allows the proximal attachment system to remain intact. It may also enable infrarenal clamping of the aorta during the operation. The anastomosis is performed by incorporating the proximal attachment system of the endograft. This technique simplifies both vascular control of the aorta and the necessary reconstruction during creation of the proximal anastomosis. We believe this technique has important advantages when conversion of a failed endograft is required.

Decision-making in follow-up after endovascular aneurysm repair based on diameter and volume measurements: a blinded comparison

OBJECTIVE

to assess whether volume, in addition to diameter, measurements facilitate decision-making after endovascular aneurysm repair (EVAR).

MATERIAL/METHODS

patients (n = 82) with an immediately post-EVAR, and at least one follow-up (3-60 months), computed tomographic angiogram (CTA) were studied. The actual and all preceding proportional sac size changes were recorded. The resulting 347 diameter and 347 volume data were placed in random order and reviewed by three blinded observers who then recommended one of three treatment policies: "good/wait", "uncertain/intensify follow-up" or "not good/further diagnostics (Dx) or intervention (Rx)". The observers were instructed to consider changes of 10% relevant. One observer reviewed the graphs twice.

RESULTS

the interobserver agreements (kappa) for the diameter were 0.92, 0.81 and 0.76 and for volumes 0.91, 0.88 and 0.86. The intra-observer agreement was 0.93 for both diameter and volume. Volume data resulted in significantly more "good/wait" decisions out to 36 months. Diameter data resulted in more "not good/Dx or Rx"-decisions out to 36 months (all p < 50.005).

CONCLUSION

post-EVAR aneurysm sac volume data appears to provide earlier reassurance, reduce unnecessary interventions and to be more sensitive to secondary problems than diameter data alone.

Rapid, arteriovenous graft failure due to intimal hyperplasia: a porcine, bilateral, carotid arteriovenous graft model

BACKGROUND

The loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future.

MATERIALS AND METHODS

In 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis.

RESULTS

From 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation.

CONCLUSIONS

Implantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.