Rate of change in abdominal aortic aneurysm diameter after endovascular repair

3D finite-element modeling of vascular adaptation after endovascular aneurysm repair

Aneurysm shrinkage is clinically observed after successful endovascular aortic aneurysm repair (EVAR). However, global understanding of post-operative aneurysm evolutions remains weak. In this work, we propose to study these effects using numerical simulation. We set up a 3D finite-element model of post-EVAR vascular adaptation within an open-source finite-element code, which was initially developed for growth and remodeling (G&R). We modeled the endograft with a set of uniaxial prestrained springs that apply radial forces on the inner surface of the artery. Constitutive equations, momentum balance equations, and equations related to the mechanobiology of the artery were formulated based on the homogenized constrained mixture theory. We performed a sensitivity analysis by varying different selected parameters, namely oversizing and compliance of the stent-graft, gain parameters related to collagen G&R, and the residual pressure in the aneurysm sac. This permitted us to evaluate how each factor influences post-EVAR vascular adaptation. It was found that oversizing, compliance or gain parameters have a limited influence compared to that of the residual pressure in the aneurysm sac, which was found to play a critical role in the stability of aneurysm after stent-graft implantation. An excessive residual pressure larger than 50 mmHg can induce a continuous expansion of the aneurysm while a moderate residual pressure below this critical threshold yields continuous shrinkage of the aneurysm. Moreover, it was found that elderly patients, with relatively lower amounts of remnant elastin in the arterial wall, are more sensitive to the effect of residual pressure. Therefore, these results show that elderly patients may present a higher potential risk of aortic sac expansion due to intra-aneurysm sac pressure after EVAR than younger patients.

Evaluation the Aortic Aneurysm Remodeling After a Successful Stentgraft Implantation

Background

Routine imaging follow-up after endovascular treatment of abdominal aortic aneurysms (EVAR) is mainly aimed at detection of endoleaks. The aim of the study was to assess changes in the size of the abdominal aortic aneurysm sack using CT angiography (CTA) after successful treatment using endovascular stent graft implantation.

Material/Methods

A retrospective analysis of CTA results included 102 patients aged 54–88, who had no postoperative complications. Patients underwent CTA before EVAR and after the treatment (mean time between studies, 7.6 months). The largest cross-sectional area of the aneurysm sac was measured using a curved multiplanar reconstruction. A change of the aneurysm cross-sectional over 10% was considered significant.

Results

The average cross-sectional area decreased after EVAR by 3% and this change was not statistically significant. Regression of the cross-sectional area was observed in 18.6% of patients, progression was in 23.5%, and no change was seen in 57.8%. Cross-sectional areas before and after EVAR were significantly correlated (r=0.75, p<0.0001). There was no correlation between the cross-sectional area change after EVAR and patients’ age or the time between the treatment and the follow-up CTA. Cross-sectional area before the treatment predicted changes in the aneurysm size after EVAR (p=0.0045).

Conclusions

Remodeling of abdominal aortic aneurysms after EVAR is not uniform. The change of aneurysm size depends on the initial aneurysm size but not on the time from EVAR. The size of the aneurysm after EVAR should not be considered as a measure of the treatment efficacy.

When Aortic Stenting Alone Does Not Solve It: Mass Effect of Thoracic Aneurysms

Thoracic aneurysms can potentially cause substantial compression of adjacent structures, creating substantial symptoms. We present a case of a 56-year-old woman with fatigue and dyspnea for 6 months. We discuss her initial endovascular treatment, which was insufficient to improve symptoms, and further surgical intervention was needed to solve the issue.

Endovascular treatment of a small infrarenal abdominal aortic aneurysm causing duodenal obstruction: Case report and literature review

Duodenal obstruction caused by abdominal aortic aneurysm was first described by Osler in 1905 and is named “aortoduodenal syndrome.” This condition has always been treated by open surgical repair. We report the first case of aortoduodenal syndrome successfully treated by endovascular aneurysm repair. A 74-year-old male patient referred to our hospital complaining postprandial vomit, reporting a consistent weight loss in the latest weeks. Enhanced computed tomography scans showed a small saccular abdominal aortic aneurysm compressing duodenum and inferior vena cava without any other evident pathological finding. As the patient underwent a successful endovascular treatment of the abdominal aortic aneurysm, symptoms immediately resolved so that he started back to feed and progressively gained body weight. Despite aortoduodenal syndrome is generally caused by large abdominal aortic aneurysm, this condition has to be suspected also in case of small abdominal aortic aneurysm. Differently from what has been reported in literature, endovascular aneurysm repair could be effective in the treatment of aortoduodenal syndrome.

Impact of contrast injection and stent-graft implantation on reproducibility of volume measurements in semiautomated segmentation of abdominal aortic aneurysm on computed tomography

PURPOSE

To assess the impact of contrast injection and stent-graft implantation on feasibility, accuracy, and reproducibility of abdominal aortic aneurysm (AAA) volume and maximal diameter (D-max) measurements using segmentation software.

MATERIALS AND METHODS

CT images of 80 subjects presenting AAA were divided into four equal groups: with or without contrast enhancement, and with or without stent-graft implantation. Semiautomated software was used to segment the aortic wall, once by an expert and twice by three readers. Volume and D-max reproducibility was estimated by intraclass correlation coefficients (ICC), and accuracy was estimated between the expert and the readers by mean relative errors.

RESULTS

All segmentations were technically successful. The mean AAA volume was 167.0 ± 82.8 mL and the mean D-max 55.0 ± 10.6 mm. Inter- and intraobserver ICCs for volume and D-max measurements were greater than 0.99. Mean relative errors between readers varied between -1.8 ± 4.6 and 0.0 ± 3.6 mL. Mean relative errors in volume and D-max measurements between readers showed no significant difference between the four groups (P ≥ 0.2).

CONCLUSION

The feasibility, accuracy, and reproducibility of AAA volume and D-max measurements using segmentation software were not affected by the absence of contrast injection or the presence of stent-graft.

KEY POINTS

• AAA volumetry by semiautomated segmentation is accurate on CT following endovascular repair. • AAA volumetry by semiautomated segmentation is accurate on unenhanced CT. • Standardization of the segmentation technique maximizes the reproducibility of volume measurements.

Statins Promote Residual Aneurysm Sac Regression Following Endovascular Aortic Aneurysm Repair

Background:

Regression of the residual sac is indicative of successful endovascular aortic aneurysm (EVAR) repair. Using color duplex ultrasound (CDU), we monitored the residual aneurysm sac following EVAR and correlated sac behavior with perioperative risk factors.

Methods:

Of 145 patients with EVAR, 106 (73.1%) patients between January 01, 2003, and July 01, 2010, had at least 2 consecutive postoperative scans and thus were eligible for inclusion. Mean (± standard deviation [SD]) CDU scans per person was 4.6 (±1.4). All were conducted by the same technologist using a standard protocol on the same machine. Aneurysm sac change in centimeters and percentage terms was calculated. The presence or absence of an endoleak was also recorded. Change in aneurysm sac size was correlated with preoperative risk factors.

Findings:

Mean sac size change at 1 month was a decrease of 0.24 cm, equating to a percentage change of 4.3%. At 7 months, the decrease was 0.59 cm (9.8%), at 12 months, 0.73 cm (12.4%), at 18 months 0.92 cm (15.8%), and at 36 months 1.0 cm (16.6%). Both univariate and multivariate analyses demonstrated that statin therapy ( P = .002) was the only risk factor variable positively associated with aneurysm regression while the presence of an endoleak was inversely related to sac reduction ( P = .01).

Interpretation:

Maximum aneurysmal sac reduction seems to occur in the first year following endograft implantation. Statin therapy appears to be associated with an increased likelihood of sac regression following EVAR. Further investigation of the role of statins in the biology of abdominal aortic aneurysmal disease is warranted.

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

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

Measurements and detection of abdominal aortic aneurysm growth: Accuracy and reproducibility of a segmentation software

PURPOSE

To validate the reproducibility and accuracy of a software dedicated to measure abdominal aortic aneurysm (AAA) diameter, volume and growth over time.

MATERIALS AND METHODS

A software enabling AAA segmentation, diameter and volume measurement on computed tomography angiography (CTA) was tested. Validation was conducted in 28 patients with an AAA having 2 consecutive CTA examinations. The segmentation was performed twice by a senior radiologist and once by 3 medical students on all 56 CTAs. Intra and inter-observer reproducibility of D-max and volumes values were calculated by intraclass correlation coefficient (ICC). Systematic errors were evaluated by Bland-Altman analysis. Differences in D-max and volume growth were compared with paired Student's t-tests.

RESULTS

Mean D-max and volume were 49.6±6.2mm and 117.2±36.2ml for baseline and 53.6±7.9mm and 139.6±56.3ml for follow-up studies. Volume growth (17.3%) was higher than D-max progression (8.0%) between baseline and follow-up examinations (p<.0001). For the senior radiologist, intra-observer ICC of D-max and volume measurements were respectively estimated at 0.997 (≥0.991) and 1.000 (≥0.999). Overall inter-observer ICC of D-max and volume measurements were respectively estimated at 0.995 (0.990-0.997) and 0.999 (>0.999). Bland-Altman analysis showed excellent inter-reader agreement with a repeatability coefficient <3mm for D-max, <7% for relative D-max growth, <6ml for volume and <6% for relative volume growth.

CONCLUSION

Software AAA volume measurements were more sensitive than AAA D-max to detect AAA growth while providing an equivalent and high reproducibility.

Preoperative thrombus volume predicts sac regression after endovascular aneurysm repair

PURPOSE

To examine whether preoperative aneurysm thrombus volume correlated with abdominal aortic aneurysm (AAA) sac regression following endovascular aneurysm repair (EVAR).

METHODS

Clinical records and computed tomographic angiograms (CTAs) from patients undergoing EVAR from 2003 to 2008 were reviewed. Inclusion criteria for this study were available preoperative CTA images, >or=12-month follow-up with surveillance imaging, lack of re-intervention at 12 months, and treatment with commercially available devices. Patients with ruptured AAAs, those requiring an aortomonoiliac stent-graft, and clinical trial cases were excluded. Based on these criteria, satisfactory images and clinical follow-up were available in 100 patients (90 men; mean age 76.8 years, range 55-95). Preoperative CTAs were categorized as demonstrating "minimal," "moderate," or "severe" aneurysm thrombus load by 2 independent examiners blinded to clinical outcome. Percentage of the aortic cross-sectional area occluded by clot (% clot area) was calculated as [(total area) - (luminal area)]/(total area). Multivariate logistic regression analysis was performed to determine predictors of sac shrinkage at long-term follow-up.

RESULTS

AAA thrombus was classified as minimal in 24%, moderate in 23%, and severe in 53%. Thrombus area averaged 11%+/-13%, 41%+/-14%, and 72+/-12% in each group, respectively. By multivariate analysis, minimal thrombus (OR = 1.47) and greater AAA diameter (OR = 1.3) were independent predictors of sac regression at 1, 6, and 12 months (all p<0.05). Presence of neck plaque and endoleak were also independent predictors of sac expansion (p<0.05). Patients with severe preoperative thrombus were less likely to demonstrate sac regression even in the absence of endoleak. Thrombus judgment (subjective) and percent clot area (objective) were strongly correlated (R = 0.82, p<0.05). Interobserver agreement on thrombus judgment was 86%.

CONCLUSION

Thrombus burden on preoperative CTA is a strong independent predictor of sac regression following EVAR. If validated by prospective studies, relative thrombus burden should be incorporated into postoperative surveillance algorithms to define procedural success and optimize the timing and cost-effectiveness of cross-sectional imaging.

Type II endoleaks: when is intervention indicated and what is the index of suspicion for types I or III?

One of the principal reasons for failure of endovascular aneurysm repair (EVAR) is the occurrence of endoleaks, which regardless of size or type can transmit systemic pressure to the aneurysm sac. There is little debate that type I endoleaks (poor proximal or distal sealing) are associated with continued risk of aneurysm rupture and require treatment. Similarly, with type III endoleak, there is agreement that the defect in the device needs to be addressed; however, what to do with type II endoleaks and their effect on long-term outcome are not so clear. Aneurysm sac change is a primary parameter for determining the presence of an endoleak and assessing its impact. While diameter measurement has been the most commonly used method for determining sac changes, volume measurement has now been proven superior for monitoring structural changes in the 3-dimensional sac. Determining the source of an endoleak and the direction of flow are necessary for proper classification; however, while computed tomographic angiography has high sensitivity and specificity for detecting endoleaks, it is limited in its ability to show the direction of flow. Contrast-enhanced duplex ultrasound, on the other hand, is better able to quantify flow and characterize endoleaks. Flow is evidence of pressure, and increasing intrasac pressure increases wall tension, thus inducing progressive aneurysm expansion until rupture. Hence, determining intrasac pressure is becoming a vital component of endoleak assessment. All endoleaks can create systemic pressure inside the aneurysm sac, and there are a variety of intrasac pressure transducers being evaluated to assess this effect. A clinical pathway for patients with suspected type II endoleaks is based on a combination of imaging and pressure measurements. Imaging alone requires at least two interval examinations to determine the trend, while pressure measurements give immediate reassurance or an indication to intervene. Although still under development, pressure measurement is destined for general use and will provide a scientific basis for the management of type II endoleaks.

Upper gastrointestinal obstruction secondary to aortoduodenal syndrome owing to a noninflammatory abdominal aortic aneurysm

Aortoduodenal syndrome is a rare complication of an abdominal aortic aneurysm wherein the aneurysm sac obstructs the patient's duodenum. It presents with the symptoms of an upper gastrointestinal tract obstruction and requires surgical intervention to relieve it. Previously, gastric bypass surgery was advocated, but now aortic replacement is the mainstay of treatment. We report a case of a 67-year-old woman whose aortoduodenal syndrome was successfully managed and review the literature on this topic.

A randomized, placebo-controlled trial of doxycycline after endoluminal aneurysm repair

BACKGROUND

The late durability of endovascular aneurysm repair (EVAR) has been limited by progressive aortic degeneration believed to be mediated by matrix metalloproteases (MMP). The goal of this study was to evaluate the effect of a MMP inhibitor, doxycycline, on EVAR.

METHODS

Patients undergoing EVAR were randomized to doxycycline (100 mg twice daily) or placebo for 6 months following the procedure. Clinical data, blood samples, and computed tomography (CT) scans were obtained preoperatively, postoperatively (blood only), and at 1- and 6-month follow-up. Forty-four subjects were analyzed based on intention-to-treat.

RESULTS

Plasma MMP-9 decreased significantly below baseline in the doxycycline (N = 20) treated patients at 6 months (-16.4% +/- 20.7%, P < .05) while there was a nonsignificant increase in the placebo (N = 24) group (128.1% +/- 73.5%). This was primarily related to changes between 1 and 6 months. In patients with endoleaks at 6 months, plasma MMP-9 increased in 83% of the placebo treated patients, but in only 14% of the doxycycline treated group (P < .03). Among endoleak-free patients with AneuRx or Excluder endografts, doxycycline treatment resulted in greater decreases in maximum aortic diameter than placebo treatment (-13.3% +/- 3.3% vs -3.8% +/- 3.0%, P < .05). Furthermore, doxycycline treatment significantly reduced the aortic neck dilatation at 6 months in Excluder treated patients.

CONCLUSION

There is evidence of persistent MMP release representing ongoing aortic degradation after endografting which can be inhibited by doxycycline therapy. In analyses based on the endograft used, treatment with doxycycline also demonstrated evidence of increased aortic dimensional stability, a surrogate marker for long-term success of EVAR. Although encouraging, these results require confirmation in larger patient populations. Doxycycline should undergo more thorough evaluation as a potential adjuvant treatment to improve the results of EVAR, particularly in certain subgroups.

MRI virtual biopsies: analysis of an explanted endovascular device and perspectives for the future

Information that can be obtained by magnetic resonance imaging (MRI) of explanted endovascular devices must be validated as this method is non-destructive. Histology of such a device together with its encroached tissues can be elegantly performed after polymethymethacrylate (PMMA) embedding, but this approach requires destruction of the specimen. The issue is therefore to determine if the MRI is sufficient to fully validate an explanted device based upon the characterization of an explanted specimen. An AneuRx device deployed percutaneously 25 months earlier in a 75-year-old patient was removed en bloc at autopsy together with the surrounding aneurysmal sac and segments of the upstream and downstream arteries. Macroscopic pictures were taken and a slice of the cross-section was processed for histology after polymethylmethacrylate (PMMA) embedding. For the magnetic resonance imaging investigation, the device was inserted in a Biospec 4.7 T MRI system with a 20 mm diameter birdcage resonator used for both emission and reception. A Spin-Echo (SE) was used to acquire both T1 proton density (PD) and T2 weighted images. A gradient-echo (GE) sampling of a free induction decay (GESFID) was used to generate multiple GE images using a single excitation pulse so that four images at different TE were obtained in the same acquisition. The selected explanted device was outstandingly well-healed compared to most devices harvested from humans. No inflammatory process was observed in contact or at distance of the materials. In MRI T1 images display no specific contrast and were homogeneous in the different tissues. The contrast was improved on proton density weighed images. On the T2 weighed images, the different areas were well identified. The diffusion images displayed in the surrounding B region had the greatest diffusion coefficient and the greatest anisotropy. The MRI analysis of the explanted AneuRx device illustrates the possibilities of this technique to characterize the interaction of the endovascular graft with the surrounding tissues. MRI is a breakthrough to investigate explanted medical devices but it also can be advantageously used in vivo to obtain virtual biopsies, because real biopsies to determine the 3 Bs (biocompatibility, biofunctionality and bioresilience) cannot be carried out as they could obviously initiate infection and degradation of the foreign materials.

Factors predictive of early or late aneurysm sac size change following endovascular repair

OBJECTIVE

The purpose of this study was to determine the relationship between aneurysm sac size change at 1, 6, 12, and 24 months and a set of 10 independent "predictive" variables by using a general linear model analysis.

METHODS

In a multicenter trial, 351 patients received the Zenith tri-modular bifurcated endograft. The predictive variables used for this analysis were endoleak by type, age, gender, smoking status, and the preprocedure variables of maximum aneurysm major diameter, minor neck diameter, proximal neck length, neck plaque/thrombus, and neck shape; and patent inferior mesenteric artery at predischarge. The aneurysm change was calculated as the difference from the predischarge (< or = 7 days of implant) maximum aneurysm major diameter measurement to the maximum aneurysm major diameter measurement at follow-up examination periods of 1, 6, 12, and 24 months. The same 10 predictive variables were used to assess the absolute change in maximum aneurysm minor diameter and aneurysm area. Additionally, the percent change from predischarge was also assessed for the major diameter, minor diameter, and aneurysm area.

RESULTS

None of the independent variables were predictive of absolute sac size change or percent change at 1 month. At 6 months, the presence of an endoleak (P < .01) and preprocedure neck thrombus/plaque (P = .01) were significant predictors of absolute and relative aneurysm size change for all measurements (major diameter, minor diameter, and area) and were more likely to be associated with less sac shrinkage or to have sac growth. Additionally, preoperative maximum aneurysm major diameter was a significant predictor for absolute change in area (P < .01). Larger preprocedure aneurysm diameters were more likely to experience more shrinkage. The significant predictors of size change at 12 months included preprocedure maximum aneurysm major diameter, the presence of endoleak at 12 months, preoperative neck thrombus/plaque, and gender. At 24 months, significant predictors of aneurysm size change included preprocedure maximum aneurysm major diameter, endoleak at 24 months, and preprocedure neck thrombus/plaque. When the longitudinal model was used, the presence of an endoleak, thrombus/plaque within the proximal neck at preprocedure, and preprocedure maximum aneurysm major diameter were found to be significantly related to the size of the maximum aneurysm major diameter over time.

CONCLUSIONS

This study supports the concept that early and late sac size change following EVAR is influenced by identifiable independent predictive variables.

Factors affecting the regression of surgically replaced abdominal aortic aneurysms

PURPOSE

After endovascular therapy for abdominal aortic aneurysms, aneurysm sac shrinkage is considered to be the best marker of successful treatment. Such shrinkage, however, is infrequent and the rate of shrinkage is variable because of endoleaks. To investigate the factors that influence such contraction, the aneurysm sac regression after a conventional surgical replacement of the abdominal aortic aneurysm in an inclusion fashion was studied.

METHODS

Abdominal aortic aneurysms that measured 5 cm in diameter or larger were studied in 35 patients who underwent surgical replacement. The aneurysm sac was closed anterior to the prosthesis. Of the 35 cases, 4 aneurysms were inflammatory and 10 had aneurysm wall circumferential calcification of greater than 40%. Computed tomography was performed preoperatively, and at 1 week, and then 3 months postoperatively.

RESULTS

The maximum major and minor diameters of the aneurysmal sac decreased significantly from 1 week to 3 months after surgery (major diameter: 49 +/- 12 to 32 +/- 8 mm and minor diameter: 39 +/- 10 to 26 +/- 7 mm). In inflammatory aneurysms, the maximum major and minor diameters were significantly larger at 3 months postoperatively, in comparison to nonspecific aneurysms. Among the 31 patients with nonspecific aneurysms, the maximum major diameter was significantly larger in those with aneurysmal calcification of greater than 40% of its circumference at 3 months postoperatively, in comparison to noncalcified aneurysms.

CONCLUSIONS

The surgically repaired abdominal aortic aneurysm contraction tends to develop over 3 months, and inflammation, thickening, and calcification of the aneurysm wall are all considered to influence the regression of the aneurysm.

Endovascular Repair of Abdominal Aortic Aneurysms: Analysis of Aneurysm Volumetric Changes at Mid-Term Follow-Up

PURPOSE

To evaluate the volumetric changes in abdominal aortic aneurysms (AAA) after endovascular AAA repair (EVAR) in 24 months of follow-up.

METHODS

We evaluated the volume modifications in 63 consecutive patients after EVAR. All patients underwent strict duplex ultrasound and computed tomography angiography (CTA) follow-up; when complications were suspected, digital subtraction angiography was also performed. CTA datasets at 1, 6, 12, and 24 months were post-processed through semiautomatic segmentation, to isolate the aneurysmal sac and calculate its volume. Maximum transverse diameters (Dmax) were also obtained in the true axial plane, Presence and type of endoleak (EL) were recorded. A statistical analysis was performed to assess the degree of volume change, correlation with diameter modifications, and significance of the volume increase with respect to ELs.

RESULTS

Mean reconstruction time was 7 min. Mean volume reduction rates were 6.5%, 8%, and 9.6% at 6, 12, and 24 months follow-up, respectively. Mean Dmax reduction rates were 4.2%, 6.7%, and 12%; correlation with volumes was poor (r = 0.73-0.81). ELs were found in 19 patients and were more frequent (p = 0.04) in patients with higher preprocedural Dmax, The accuracies of volume changes in predicting ELs ranged between 74.6% and 84.1% and were higher than those of Dmax modifications. The strongest independent predictor of EL was a volume change at 6 months < or = 0.3% (p = 0.005), although 6 of 19 (32%) patients with EL showed no significant AAA enlargement, whereas in 6 of 44 (14%) patients without EL the aneurysm enlarged.

CONCLUSION

The lack of volume decrease in the aneurysm of at least 0.3% at 6 months follow-up indicates the need for closer surveillance, and has a higher predictive accuracy for an endoleak than Dmax.

Aortic diameter is an insensitive measurement of early aneurysm expansion after endografting

PURPOSE

To determine the sensitivity of various methods of diameter measurement to detect abdominal aortic aneurysm (AAA) size change following endovascular grafting.

METHODS

Sixty-eight patients (59 men; mean age 68 years, range 47-84) with 3-dimensional reconstruction of 196 computed tomography (CT) studies (68 preoperative, 128 follow-up) were studied. Implanted devices included 50 bifurcated and 18 straight stent-grafts. All diameter measurements were obtained from reformatted CT slices perpendicular to the center of blood flow. Three diameter measurements were made for each study: (1) transverse (TR), (2) anteroposterior (AP), and (3) maximum diameter in any orientation (Dmax). Volume measurements were calculated from the lowest main renal artery to the aortic bifurcation. Changes in diameter and volume were determined by subtracting follow-up measurements from preop measurements. Diameter and volume changes >5 mm and 10%, respectively, were considered significant.

RESULTS

AAA volume significantly increased in 20 (15%) studies, decreased in 84 (66%), and remained unchanged in 24 (19%). Agreement between methods of diameter measurement (TR, AP, Dmax) and volume change were 35%, 15%, and 25% for volume increase >10%, respectively, and 70%, 88%, and 74%, respectively, for volume decrease >10%. The orientation of maximum diameter varied in individual serial exams in 19 (28%) patients. Three of 12 patients with a study showing volume increase failed to demonstrate endoleak.

CONCLUSIONS

Diameter measurements were not sensitive in detecting enlarging AAA after endografting. Volume measurement determined by 3D reconstruction is the preferred method for early diagnosis of patients with enlarging AAA that may indicate increased risk of rupture after aortic endografting.

Endovascular treatment of abdominal aortic aneurysm

BACKGROUND

Endovascular repair of abdominal aortic aneurysm has become widely used. Supporters claim high success rates, few complications and a dramatically reduced hospital stay. However, endoleak, endotension and reports of endoprosthesis rupture are causes of concern.

METHODS

A Medline search was undertaken to identify articles on endovascular repair of abdominal aortic aneurysm. Additional papers were identified by manual scanning of the references from key articles.

RESULTS AND CONCLUSION

Endoleak is a potentially serious complication of the endovascular technique and occurs in a significant proportion of patients. It is still not possible to judge whether the presence of an endoleak alone signifies failure of treatment, and the long-term durability of prosthetic covered stents is unknown. However, endovascular repair does appear to confer a degree of protection from rupture although patients must be advised of the need for life-long imaging surveillance and, perhaps, further intervention.

Changes in Abdominal Aortic Aneurysm Size after Endovascular Repair with Zenith, AneuRx, and Custom-made Stent-Grafts

The aim of this study was to determine the maximal aneurysm diameter (MAD), the total aneurysm volume (TAV), the intra-aneurysm vascular channel (IAVC), and total thrombus volume (TTV) and compare changes in those parameters during a 12-month time period. In addition, these parameters for three different endovascular grafts were compared. A retrospective review of 42 patients who had undergone endovascular aneurysm repair (EVAR) between July 1999 and March 2001, and without evidence of an endoleak or migration, was performed. The minimum follow-up in this group was 12 months. The three grafts deployed were Dacron-stainless steel bifurcated grafts with suprarenal fixation [Zenith; Cook, Inc. ( n = 14)], Dacron stainless steel aorto uni-iliac grafts with suprarenal fixation [custom-made ( n = 10)], and externally supported Dacron nitinol bifurcated grafts [AneuRx; Medtronic, Inc. ( n = 18)]. Volumetric measurements were obtained from CT images performed preoperatively, at 1 month and 12 months thereafter, using a 3-D Magicview 1000 workstation (Siemens, Inc.). Regardless of the type of endograft, a significant Change in MAD and TAV ( P = 0.008), IAVC ( P = 0.031), and TTV ( P = 0.001) was observed over the 12-month postoperative period. Both maximum diameter and total aneurysm volume appear to reflect accurately successful aneurysm exclusion. We conclude that both two-dimensional, maximal aneurysm diameter and three-dimensional, total aneurysm volume accurately reflect changes in morphology after endovascular aneurysm repair.

Pseudoaneurysm of the Dorsalis Pedis Artery Causing Neurological Deficit

Pseudoaneurysm of the dorsalis pedis artery is very rare. This case report describes a 71-year-old man with an idiopathic aneurysm of the dorsalis pedis artery that caused neurological deficit. Surgical resection was performed and his symptoms improved.

Late abdominal aortic aneurysm enlargement after endovascular repair with the excluder device

OBJECTIVES

Behavior of the abdominal aortic aneurysm (AAA) sac after endovascular abdominal aortic aneurysm repair (EVAR) is graft-dependent. The Excluder endograft has been associated with less sac regression than some other stent grafts. Long-term follow-up has not been reported.

METHODS

Between May 1999 and July 2002, 50 patients underwent EVAR with the Excluder bifurcated endoprosthesis. These patients were followed up prospectively with computed tomography (CT) at 1, 6, and 12 months and yearly thereafter. One immediate conversion to open surgery and three deaths occurred within 6 months. One additional patient was lost to follow-up. The remaining 45 patients, 35 men and 10 women, were followed up for at least 1 year, and form the basis for this report. Their mean age was 73 +/- 5.5 years. The minor axis diameter at the largest area of the AAA on CT examination was compared with the baseline measurement at 1 month and to the smallest size previously recorded during follow-up. Change in sac size of 5 mm or greater was considered significant. Mean follow-up was 2.7 +/- 1.2 years (range, 1-4 years). Nominal variables were compared with the chi(2) test, and continuous variables with the Student t test.

RESULTS

A significant decrease in average AAA sac diameter was observed at 6-month, 1-year, and 2-year follow-up. These differences were lost by the 3-year evaluation, because of delayed sac growth (n = 9) and re-expansion of once shrunken aneurysms (n = 3). The probability of freedom from sac growth or re-expansion at 4 years was only 43%. At last follow-up, sac expansion occurred in the absence of active endoleak in nine patients. Type II endoleak was associated with sac expansion in three patients (P =.003), resulting in one conversion to open surgery after the 4-year follow-up. No graft migrations, AAA ruptures, or aneurysm-related deaths were noted.

CONCLUSIONS

Late aneurysm sac growth or re-expansion after EVAR with the Excluder device is common, even in the absence of endoleak. Although the incidence of important clinical sequelae is low at this point, the incidence of aneurysm expansion should be taken into consideration during the risk-benefit assessment before EVAR repair with the Excluder device.

Change in Aneurysm Diameter After Stent-Graft Repair of Ruptured Abdominal Aortic Aneurysms

PURPOSE

To compare the changes in aneurysm size following endovascular aneurysm repair (EVAR) for ruptured versus elective abdominal aortic aneurysms (AAA).

METHODS

Aneurysm sac diameter was measured from computed tomographic (CT) scans in 14 hemodynamically stable patients (14 men; mean age 74+/-7 years, range 60 to 83) prior to emergent stent-graft repair for ruptured AAA. The aneurysm diameter change was followed postprocedurally with serial CT and the outcomes compared to 74 AAA patients (58 men; mean age 74+/-7 years, range 56 to 87) having elective EVAR in the same time period. The mean rate of sac decrease (mm/month) was calculated for each group.

RESULTS

There were 3 postoperative deaths in the ruptured AAA cohort, leaving 11 patients available for follow-up analysis (mean 16 months, range 2-49). Eight (73%) patients with ruptured AAA demonstrated significantly decreased (>5 mm) aneurysm diameters compared with 32 (43%) elective cases (p=0.07) followed a mean 20 months (range 3-51). The mean rate of sac diameter decrease was 1.50+/-1.03 mm/month in the rupture group versus 0.73+/-0.86 mm/month in the elective group (p=0.04).

CONCLUSIONS

This study suggests that ruptured AAAs treated with stent-graft experience sac regression at a higher rate compared with electively treated AAA. The reasons for these findings remain unclear.

Is a Type II Endoleak after EVAR a Harbinger of Risk? Causes and Outcome of Open Conversion and Aneurysm Rupture during Follow-up

OBJECTIVE

There is still debate whether type II endoleaks represent a risk for the patient after EVAR. Treatment policies vary from fairly conservative to active intervention. In this analysis risk factors for type II endoleak and adverse events during follow-up were assessed. In addition, risk factors and causes for conversion to open repair and for rupture post-EVAR were studied.

METHODS

The data of 3595 patients, who underwent operation between 1996 and 2002 in 114 European institutions that collaborated in the EUROSTAR Registry, were assessed. To accurately assess the influence of type II endoleaks patients with type I, III and combined endoleaks were excluded from the present study cohort.

RESULTS

A combined adverse outcome event consisting of aneurysmal growth, transfemoral reintervention, and transabdominal secondary procedures (including laparoscopic branch vessel clipping) occurred in 55% in patients with type II endoleak at 3 years, compared to 15% in patients without any endoleak (p<0.0001). Conversion to open repair or post-EVAR rupture was not significantly associated with type II endoleaks. An independent association of device migration and expansion of the aneurysm with late conversion was observed. The cumulative incidence of aneurysm rupture at 3 years of follow-up was 1.2% for an annual rate of 0.4%. Variables that significantly and independently correlated with rupture were size of the aneurysm at preoperative measurement and device migration during follow-up.

CONCLUSION

Endoleak type II may not be harmless as it was more frequently associated with enlargement of the aneurysm and reinterventions. Large aneurysms and migration of the device were the main risk factors for rupture. The clinical implications of these findings may involve more frequent surveillance visits for patients with type II endoleak. Aneurysm expansion is a clear indication for reintervention. Patients with large aneurysms, 65 mm or larger, may also benefit from a more comprehensive surveillance schedule.

Aneurysm enlargement following endovascular aneurysm repair: AneuRx clinical trial

OBJECTIVE

The purpose of this study was to determine the incidence and significance of aneurysm enlargement, with or without treatment, in relation to the primary end points of rupture, surgical conversion, aneurysm-related death, and survival following endovascular repair.

METHOD

Aneurysm (AAA) size changes and clinical outcome of all patients treated from 1997 through 1998 during the Phase II AneuRx multicenter clinical trial of endovascular AAA repair were reviewed. Aneurysm dimensions and the presence or absence of endoleak were determined by an independent core laboratory, with enlargement or shrinkage defined as a diameter change of 5 mm or more compared with baseline.

RESULTS

Among 383 patients (89% men, 11% women, age 73 +/- 9 years), with a mean device implant time of 36 +/- 11 months (median = 39 months), aneurysm diameter decreased from 5.7 +/- 1.0 at baseline to 5.2 +/- 1.0 at 3 years (P =.0001). A total of 46 patients (12%) experienced AAA enlargement, 199 patients (52%) had no change in AAA diameter, and 138 patients (36%) had a decrease in AAA diameter of 5 mm or more. Significant risk factors for enlargement included age (enlargement patients were 4 years older on average than patients with aneurysms that decreased in size; P =.002) and the presence of an endoleak (P <.001). Among patients with endoleak at any time, 17% had aneurysm enlargement, whereas only 2% of patients without endoleak had aneurysm enlargement (P <.001). Patients with enlargement were more likely to undergo secondary endovascular procedures and surgical conversions (P <.001). Twenty patients (43%) with enlargement underwent treatment, and 26 patients were untreated. There were two deaths following elective surgical conversion and one death in a patient with untreated enlargement and a type I endoleak. Three aneurysms ruptured: one with enlargement, one with no change, and one with a decrease in aneurysm size; all three aneurysms were larger than 6.5 cm. Kaplan-Meier analysis showed that freedom from rupture at 3 years was 98% with enlargement, 99% with no change, and 99% with decrease in AAA size (log-rank test, not significant). Freedom from AAA death at 3 years was 93% in patients with enlargement, 99% in no increase, and 99% in decrease (P =.005). Survival at 3 years was 86% with increase, 82% with no change, and 93% with decrease (P =.02).

CONCLUSIONS

Aneurysm enlargement following endovascular repair was not associated with an increased risk of aneurysm rupture or decrease in patient survival during a 3-year observation period. Aneurysm size rather than enlargement may be a more meaningful predictor of rupture. Close follow-up and a high re-intervention rate (43%) may account for the low risk of rupture in patients with enlargement. The long-term significance of aneurysm enlargement following endovascular repair remains to be determined.

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.

The significance and management of different types of endoleaks

Development of endovascular abdominal aortic aneurysm repair (EVAR) has been accompanied by previously unencountered complications. The most challenging but least understood of these complications is the incomplete seal of the endovascular graft (endoleak), a phenomenon that has a variety of causes. An important consequence of endoleakage may be persistent pressurization of the aneurysm sac, which may ultimately lead to post-EVAR rupture. Data of 110 European centers were recorded in a central database (EUROSTAR). Patient, anatomic characteristics, and operative and device details were correlated with the occurrence of different types of endoleaks. Outcome events during follow-up, particularly expansion of the aneurysm, incidence of conversion to open repair, and post-EVAR rupture were assessed in the different categories of endoleaks and in a group of patients without any endoleak. Type I and III endoleak were associated with an increased frequency of open conversions or risk of rupture of the aneurysm. Device-related endoleaks also correlated with an increased need for secondary interventions. These types of endoleaks need to be treated without delay, and when no other possibilities are present, an open conversion to avert the risk of rupture should be considered. Type II endoleaks do not pose an indication for urgent treatment. However, they may not be harmless, because there was a frequent association with enlargement of aneurysm and reinterventions. Our findings suggest that more frequent surveillance examinations are indicated than in patients without collateral endoleak. The indication for intervention is primarily dictated by documented expansion of the aneurysm.

Noninvasive evaluation of the effectiveness of endovascular AAA exclusion

PURPOSE

To evaluate the relationship between aneurysm sac pressure and endograft wall motion in vitro and in vivo and to compare this to sac volume changes after endovascular aneurysm repair.

METHODS

In a flow model of an aneurysm with a stent-graft in situ, sac pressure was incrementally increased by adding volume to an otherwise excluded sac; sac pressure waves were registered. Clinically, 43 patients who had unsupported endografts were monitored for stent-graft wall motion using electrocardiographically-guided M-mode ultrasonography. At 3 predetermined points in the cardiac cycle, 2 independent observers measured the maximal endograft diameter. Graft wall motion was then compared to changes in aneurysm thrombus volume (shrinking, static, growth) based on serial spiral computed tomographic angiography measurements.

RESULTS

In the in vitro model, as the sac was incrementally pressurized, the initially static pressure waveform changed to a more dynamic waveform identical to that of the systemic pressure. Additionally, graft wall motion was noted visually when the pressure exceeded 40 mm; it became increasingly vigorous at higher pressures. The 0.13-cm wall motion in the growth group (n=5) was significantly larger than the 0.04 cm in the static group (n=19; p=0.012) and the 0.03 cm in the shrinking group (n=19; p=0.002). No significant difference was found between the static and the shrinking groups (p=0.209).

CONCLUSIONS

Increases in sac pressure are reflected as increased wall motion in unsupported endografts. Clinically, increased endograft wall motion can be demonstrated by M-mode ultrasound; in growing aneurysms, the significant change in wall motion may suggest increased sac pressures as the etiology of the aneurysm growth.

Does endograft support alter the rate of aneurysm sac shrinkage after endovascular repair?

PURPOSE

To test the hypothesis that stent-graft support influences sac shrinkage independent of endoleak rates after endovascular repair of abdominal aortic aneurysms (AAA).

METHODS

Ninety AAA patients underwent treatment with bifurcated endoluminal devices at our institution between October 1996 and February 1999. Fifty-two patients were treated using a nonsupported (NS) Ancure endograft and 38 using a fully supported (FS) Excluder endograft. Computed tomographic (CT) scans were obtained during the first postoperative month and at 6, 12, and 24-month intervals. Aneurysm diameter was measured as the minor axis of the largest AAA axial slice on the CT scan. Six, 12, and 24-month sac sizes were compared to the first postoperative evaluation.

RESULTS

Successful endoluminal graft placement was accomplished in all patients. The two groups were matched for age, anatomical criteria, and comorbidities except for baseline AAA size: the mean diameter was 5.4 cm in the NS group and 5.0 cm for the FS group (p<0.01). Endoleak rates were 25% (13/52) in the NS group and 18% (7/38) in the FS group (p<0.05) at 1 month. All endoleaks that did not resolve spontaneously at 6 months were treated. Initial endoleak status did not affect the sac shrinkage rates at the 12 and 24-month evaluations. At 2 years, the NS group had greater shrinkage of the sac (1.2 cm) versus the FS cohort (0.3 cm, p<0.05). In addition, more patients in the NS group had sac shrinkage >or =5 mm (83% versus 18%, p<0.05).

CONCLUSIONS

Despite a higher endoleak rate, the nonsupported Dacron Ancure endografts were associated with greater sac shrinkage at up to 24 months following implantation.

Two-dimensional versus three-dimensional CT scan for aortic measurement

PURPOSE

To examine if 3-dimensional (3D) reconstructions of computed tomographic (CT) data, by imaging perpendicular to blood flow, can improve aortic diameter measurement accuracy over axial (2D) CT.

METHODS

Two independent, blinded observers used electronic calipers to measure the minor axis and the line perpendicular to it on 40 2.5-mm 2D CT scans from 31 patients. A circular electronic tool was used to estimate diameters on 3D reconstructions from the same 40 scans. Measurements of the aortic neck were obtained 5 mm below the renal arteries and the widest slice of the aneurysm was used to measure sac diameter. Only the minor axis was measured at the iliac arteries immediately above the left (LI) and right (RI) iliac bifurcations. Datasets were compared with an intraclass correlation coefficient (ICC), Bland and Altman variation assessments, and absolute differences.

RESULTS

ICC between 2D and 3D scans demonstrated high correlation with 2D minor axis measurements (neck=0.9282, sac=0.8956, RI=0.8755, LI=0.7381). 3D to 2D major axis correlation was lower (neck=0.6388, sac=0.8995). Variation between 3D and 2D minor axis measurements was low (0.51-mm average variation from the mean for the minor axis and 1.30-mm variation for the major axis). Average absolute difference between 3D and 2D diameters was 1.01 mm (minor axis) versus 2.61 mm (major axis). Interobserver correlation was highest for sac measurements both in 2D minor axis (ICC=0.8990) and 3D (ICC=0.9518).

CONCLUSIONS

Minor axis measurements on axial CT scan can substitute for diameters obtained from 3D reconstructions in most clinical situations.

Endovascular repair of abdominal aortic aneurysms: device-specific outcome

OBJECTIVES

Endovascular repair of abdominal aortic aneurysms, while advantageous because of its minimally invasive nature, falls short of achieving the long-term durability of traditional open surgical repair. Problems such as device migration, continued sac pressurization from endoleak, and graft limb thrombosis culminate in a high rate of secondary procedures and failure to protect against aneurysm rupture. While prior studies hint at a correlation between these postprocedural events and specific device design, a single comparative analysis that correlates device attributes with clinical outcome has not been performed.

METHODS

Over 6 years ending in 2002, 703 patients underwent endovascular treatment of infrarenal abdominal aortic aneurysms. During this time, five devices were used, ie, Ancure, AneuRx, Excluder, Talent, and Zenith, and six device-specific groups were analyzed; the Zenith group was subdivided into those placed as part of the multicenter trial (Zenith-MCT) and those under a sponsor-investigator investigational device exemption trial (Zenith-SIT). Results were assessed with the Kaplan-Meier method for censored data, and the log-rank test was used to ascertain differences between device groups.

RESULTS

While overall survival was diminished in the Zenith-SIT group (P =.046), risk for aneurysm-related death was similar in all groups (P =.336), averaging 2% or less at 12 months. Among the total cohort of patients, freedom from rupture was 98.7% +/- 0.9% at 24 months, without demonstrable differences between groups (P =.533). There were no statistically significant differences in rate of secondary procedures, conversion to open repair, or migration. There were, however, significant differences in risk for graft limb occlusion and rate of endoleak between groups. Limb occlusion occurred most often with Ancure devices (11% +/- 4.6% at 12 months, P =.009). Endoleak of any type was most common with Excluder devices (64% +/- 11% at 12 months, P =.003), a finding directly related to increased frequency of type II leaks in that group (58% +/- 11% at 12 months, P =.001). While there were no differences in frequency of type I or type III endoleak, a trend toward increased risk for microleak was observed with AneuRx devices (4.0% +/- 1.3%, P =.054), and more modular separations were observed with Zenith devices (3.5% +/- 2.3%, P =.032). Shrinkage at 12 months correlated with frequency of endoleak in the device groups, and was most common in the two Zenith groups (54% +/- 7.3% in the Zenith-MCT group and 56% +/- 7.8% in the Zenith-SIT group) and the Talent group (52% +/- 9.7%) and was least in the Excluder group (15% +/- 7.9% at 12 months, P <.001). By contrast, sac growth occurred most often in the Zenith-SIT group (13% +/- 4.5% at 12 months, P =.034), possibly as a result of the challenging aortoiliac anatomy frequently present in these patients.

CONCLUSIONS

There are significant differences in frequency of limb occlusion and endoleak between groups with different endovascular devices. Knowledge of these and other differences is instructional in development of next-generation endovascular devices, incorporating design features linked to satisfactory outcome while abandoning those associated with device failure.

Abdominal aortic aneurysm size regression after endovascular repair is endograft dependent

OBJECTIVE

This study was performed to determine whether abdominal aortic aneurysm (AAA) regression is different with various endografts after endovascular repair.

METHODS

A four-center retrospective review of size change after endovascular AAA repair was performed. Consecutive patients with at least 1-year follow-up and available imaging studies were included. Three hundred ninety patients received either the Ancure, AneuRx, Excluder, or Talent endograft. AAA size and endoleak status were recorded from computed tomography (CT) scans at the initial postoperative follow-up visit and at 1 and 2 years thereafter. AAA size was defined as the minor axis of the infrarenal aorta on the largest axial section on the two-dimensional CT scan. A change in AAA size of 0.5 cm or greater from baseline was considered clinically significant. The effect of initial size, endoleak, and type of endograft on AAA regression was analyzed.

RESULTS

Mean baseline size was significantly greater with Talent endografts and smaller with Excluder endografts. Clinically significant regression in AAA size occurred in nearly three fourths of patients with Ancure and Talent endografts at 2 years. Regression in AAA size was less frequent with the AneuRx (46%) and Excluder (44%) devices. Initial size, endoleak, and endograft type were significant predictors of regression at multivariate analysis at 1 year. However, by 2 years only endograft type was still an independent predictor of AAA shrinkage.

CONCLUSIONS

Long-term morphologic changes after endovascular aneurysm repair depend on endograft type.

Early changes in abdominal aortic aneurysm diameter after endovascular repair

PURPOSE

Endovascular repair of abdominal aortic aneurysm (AAA) is expected to alter the natural progression of diameter increase and rupture. The purpose of this study is to determine the rate of diameter change in AAA treated by endovascular repair.

MATERIALS AND METHODS

Sixty-three patients underwent endovascular repair of AAA and 12-month median follow-up by computed tomographic (CT) angiography or magnetic resonance (MR) angiography. The maximum cross-sectional outer diameters of aneurysms were measured with serial CT angiography and MR angiography. Immediate postrepair CT angiography and MR angiography were used for comparison to follow-up studies. Endoleak was also evaluated.

RESULTS

The mean and median follow-up interval was 12 months (range, 7-21 mo). There was a significant decrease in maximum diameter at follow-up (6.0 cm vs 5.1 cm; P <.001). The mean annual decrease of AAA diameter was 8.4 mm. Endoleak occurred immediately after repair in 12 patients (19%). Endoleak was detected in four patients at follow-up examination (6%). Two patients with persistent endoleaks had a mean diameter increase of 2.1 mm per year. Ten patients (16%) with successfully treated endoleak had a mean decrease in diameter of 11 mm per year. There is a significant difference in mean annual diameter change between patients with treated endoleak and those with persistent endoleak (P <.05). There was no difference in mean annual rate of change between patients with no endoleak and those with treated endoleak (8.4 mm/y vs 11 mm/y; P = NS). Seventeen of 21 patients without an appreciable decrease in aneurysm diameter had no endoleak.

CONCLUSIONS

Patients with resolved endoleak exhibit a similar shrinkage rate to patients who never had endoleak during imaging follow-up. There remains a group of patients without significant sac shrinkage after endovascular aneurysm repair (EVAR) yet have no endoleak on follow-up imaging (ie, endotension). It is still unclear whether these patients have received protection from AAA rupture from EVAR.

Patency of infrarenal aortic side branches determines early aneurysm sac behavior after endovascular repair

In this study we sought to determine whether initial abdominal aortic aneurysm (AAA) sac anatomy, morphology, and side branch patency influence changes in aneurysm size and development of endoleak following endovascular repair. A blinded, retrospective review of preintervention CT scans and angiograms was conducted on 70 consecutive patients treated for infrarenal AAA (mean size 6.0 +/- 0.8 cm) by AneuRx stent-graft exclusion. Initial AAA diameter and side branch (inferior mesenteric artery [IMA], lumbar artery pair) patency, AAA clot/sac diameter ratio, wall thrombus and calcification distributions, attachment site anatomy, endograft size, and other clinical parameters were correlated with postoperative persistent side branch patency, presence of type II endoleak, and change in AAA diameter (increase/decrease ? 5 mm) using contingency table analyses. Patients underwent CT scanning and/or color duplex imaging at 1 month and at 3 (with endoleak) or 6 (without) month intervals postoperatively with 50 patients followed beyond 6 months (mean follow-up 11 +/- 7 months). The majority of patients possessed patent side branches prior to intervention (lumbar [n = 60, 86%], IMA [n = 45, 64%]). Development of type II endoleak or persistence of side branches could not be predicted (p > 0.05) from preoperative AAA side branch patency or any of the other initial anatomic AAA variables. On serial post-repair CT or duplex cans, 42% (19/45) of IMAs and 27% (16/60) of lumbar artery pairs remained patent. For patients followed beyond 6 months, type II endoleaks persisted in half (13/25) of the patients with patent side branches with roughly equal proportions fed by IMA and lumbar sources. Persistent side branches or presence of type II endoleak was associated with AAA expansion or the failure of aneurysm size diminution after endografting (p <0.01). Aneurysm sac regression was most likely in the absence of endoleak and patent side branches. We conclude that persistent side branch patency not only fuels development of type II endoleak but also influences early aneurysm sac behavior after endovascular repair. Optimal anatomic patient selection for endografting may not be possible on the basis of our initial experience, since preoperative AAA variables did not predict persistence of side branches or type II endoleaks.

Conformational changes associated with proximal seal zone failure in abdominal aortic endografts

OBJECTIVE

Endovascular aneurysm repair (EVAR) has become a popular treatment for abdominal aortic aneurysm (AAA). This study examines conformational changes in the infrarenal aortas of patients in whom proximal seal zone failures (PSF) developed after EVAR.

METHODS

All 189 patients with aortic endograft underwent routine post-EVAR computed tomographic scan surveillance. Patients identified with proximal type I endoleaks, type III endoleaks, or proximal component separation without demonstrable endoleak underwent three-dimensional reconstruction of the computed tomographic scans from which measurements of the migration, length, volume, and angulation of the infrarenal aorta were made.

RESULTS

Five patients (3%) had PSF develop, four of whom had aortic extender cuffs. Although changes in the AAA volume and aortic neck angle were slight or variable, the mean AAA length increased 34 mm and the mean aortic body angulation increased 17 degrees (P =.03 and.01, respectively). Lengthening and migration caused proximal component separation in four patients, with concomitant migration in two patients. Two patients underwent endovascular repair, two patients needed explantation of the endograft, and one patient awaits endovascular repair. Proximal component separation and type III endoleak recurred in one patient and were repaired with a custom-fitted graft.

CONCLUSION

PSF of aortic endografts is associated with proximal angulation and lengthening of the infrarenal aorta. These findings reinforce the importance of proper initial deployment to minimize the need for aortic extender cuffs, which pose a risk of late endoleak development.

Aortic aneurysm sac shrinkage after endovascular repair is device-dependent: a comparison of Zenith and AneuRx endografts

Aneurysm sac shrinkage after endovascular aneurysm repair (EAR) provides objective evidence of successful aneurysm exclusion and absence of endotension. Attainment of this outcome parameter may be device-dependent. In this study, 169 patients underwent EAR with an AneuRx (n = 118) or Zenith (n = 51) endograft at a single institution. A prospectively maintained database was examined for significant changes in aneurysm sac diameter (> or = 5 mm) on the basis of computed tomography (CT) measurements at 6 and 12 months follow-up. Significant aneurysm sac shrinkage (> or = 5 mm) occurred in 73.1 % (19/26) vs. 43.1% (28/65) of patients in the Zenith and AneuRx groups, respectively, at 12 months (p = 0.03). At 6 months follow-up, sac shrinkage rates were 51.4% (19/37) vs. 25.8% (16/62) in the Zenith and AneuRx groups, respectively (p = 0.04). Mean reduction of sac diameter at 12 months was -7.6 +/- 1.6 mm vs. -3.5 +/- 0.8 mm in the Zenith and AneuRx groups, respectively (p = 0.01). There was a trend toward fewer Type I and III endoleaks at 1 month in the Zenith group (0 vs. 8.3%) that did not achieve statistical significance (p = 0.067). The presence of any endoleak (> or = 1 month) was associated with reduced 12 month shrink rates from 47.1% (25/51) to 28% (4/14) in the AneuRx group (p = 0.35) and from 77.3% (17/22) to 50% (2/4) in the Zenith group (p = 0.25). Patients treated with the Zenith endograft demonstrated a significantly higher rate and amount of aneurysm sac shrinkage than patients treated with an AneuRx device. Endoleaks appeared to negatively influence shrink rates with both endografts.

Stent-graft migration following endovascular repair of aneurysms with large proximal necks: anatomical risk factors and long-term sequelae

PURPOSE

To evaluate the outcome of aortic endografts deployed in large infrarenal necks and to identify any association of preoperative aneurysm characteristics and postoperative morphological changes with the incidence of neck dilatation and device migration in this patient subset.

METHODS

The records of 47 patients (41 men; mean age 74, range 55-84) with large aortic neck diameters treated with Talent stent-grafts from 1998 to 2001 were reviewed. Patients with anatomical criteria that precluded aneurysm exclusion with currently available devices were preferentially selected. Mean baseline aneurysm morphology included 27.6-mm (range 18-33.4) suprarenal and 28.1-mm (range 24-34) infrarenal neck diameters; the infrarenal neck length was 26 +/- 16 mm with angulation of 37 degrees +/- 18 degrees. Computed tomographic (CT) angiograms up to 3 years were analyzed using specialized interactive software; migration was defined as >1-cm change in the distance from the lower renal artery to the top of the device. Pre- and postoperative morphological characteristics of the aneurysm were compared between patients with and without migration.

RESULTS

Of the 45 patients successfully treated, 40 had complete CT data for analysis. During a mean 17-month follow-up, 7 (17.5%) of the 40 devices exhibited distal migration. Six patients required secondary procedures; 5 were in the migration cohort. No preoperative anatomical characteristic or degree of neck dilatation over time was predictive of stent-graft migration. Aneurysm sac regression was significant at 1 (-0.09 +/- 4.90 mm) and 2 (-1.48 +/- 2.56 mm) years in endografts without migration (p<0.001). Distal endograft migration >1 cm predicted the need for secondary interventions (p<0.001), with 83% sensitivity and 94% specificity.

CONCLUSIONS

Endovascular repair is successful in patients with large infrarenal necks and complex neck morphology. Changes in aneurysm remodeling over time were similar to reported observations in patients with more favorable neck criteria. Although no anatomical factor associated with migration could be identified from this analysis, distal displacement >1 cm correlated with the need for a secondary intervention.

Short-term results of endovascular AAA repair with the Excluder bifurcated stent-graft

PURPOSE

To evaluate the safety and efficacy of endovascular abdominal aortic aneurysm (AAA) repair with a commercial modular stent-graft.

METHODS

Between February 1998 and May 2000, 66 consecutive patients (56 men; mean age 70 years, range 51-87) were recruited for a single-center study to examine the safety and efficacy of the Excluder stent-graft for endovascular AAA repair. The patients were predominantly asymptomatic (2 symptomatic) and categorized as ASA III or IV (62, 94%), with aneurysms that ranged from 35 to 89 mm in diameter (mean 56). Surveillance included clinical examination and computed tomographic aortography at discharge, 6 weeks, and at 6, 12, and 24 months.

RESULTS

All endoprostheses were implanted as intended, but 1 patient succumbed to an intraprocedural brainstem infarction (1.5% 30-day mortality rate). The major and minor morbidity rates were 21% and 4.5%, respectively. Primary technical success at discharge was 68% (45/66), largely as the result of a 30% (20/66) endoleak rate. The aneurysm exclusion rate at 30 days was 88%. During the mean 5.8-month follow-up, no device migration, limb kinking, aneurysm rupture, or limb thrombosis was observed.

CONCLUSIONS

Endoluminal AAA repair with the bifurcated Excluder stent-graft is safe and efficacious in the short term. Longer surveillance will have to demonstrate if the excellent early results can be maintained over the years.

The sac shrinking process after EAR does not start immediately in most patients

OBJECTIVE

the aim of this study was to determine the pattern of shrinkage after endovascular aneurysm repair (EAR) using logarithmic, exponential and linear models and to calculate a lag time is present.

PATIENTS AND METHODS

patients with a complete CTA follow-up of 2 years and a primary shrinking aneurysm were included, resulting in a study group of 29 patients. Six functions, logarithmic, exponential and linear, all with and without lag time, were fitted to the thrombus volume obtained from measurements postoperative and after 6, 12 and 24 months. The correlation coefficient was used to determine the association between the calculated and measured values. A correlation coefficient >0.95 was considered a good fit.

RESULTS

a logarithmic model produced the best fits. From the 29 patients, two patients could not be described by any model. The remaining 27 patients could be fitted using a logarithmic function with a correlation coefficient of >0.95 (median 0.99, range 0.95-1.00). Twenty-two of these patients had a lag time (median 63.4 days, range 5.8-252.3). Only five of the initial 44 patients (11%) showed immediate sac shrinkage.

CONCLUSION

almost all shrinkage processes could be described by a logarithmic function. In over 75% of patients a lag time to shrinkage could be calculated. In only a small proportion did the shrinking process start immediately after EAR.