J.A. van Herwaarden

Management of Abdominal Aortic Aneurysms Clinical Practice Guidelines of the European Society for Vascular Surgery

Department of Vascular Surgery, University Medical Center Utrecht, Utrecht, The Netherlands b Imperial College, London, UK University Hospital Innsbruck, Austria Azienda Ospedaliera di Perugia, Italy Hopital Cardiologique, CHRU de Lille, Lille, France f St Thomas’ Hospital, London, UK g St George’s Vascular Institute, London, UK Yale University School of Medicine, New Haven, Connecticut, USA University of Siena, Siena, Italy University of Poitiers, Poitiers, France

Oversizing of Aortic Stent Grafts for Abdominal Aneurysm Repair: A Systematic Review of the Benefits and Risks

OBJECTIVE Sizing of aortic endografts is an essential step in successful endovascular treatment of aortic pathology, although consensus regarding the optimal sizing strategy is lacking. Some proximal oversizing is necessary to obtain a seal between the stent graft and the aortic wall and to prevent the graft from migrating, but excessive oversizing might influence the results negatively. In this systematic review, we investigated the current literature to obtain an overview of the risks and benefits of oversizing and to determine the optimal degree of oversizing of stent grafts used for endovascular abdominal aortic aneurysm repair. METHODS PUBMED, EMBASE and Cochrane Library databases were searched for articles related to the impact of proximal endograft oversizing on complications after endovascular aneurysm repair. After in- and exclusion, 23 relevant articles reporting on 8415 patients remained for analysis and critical appraisal. RESULTS Most studies that investigated neck dilatation are flawed by poor methodology. No clear relationship between proximal oversizing and neck dilatation relative to the first post-operative scan was found. None of the studies described a positive relationship between the degree of oversizing and the incidence of endoleaks. On the contrary, oversizing up to 25% seems to decrease the risk of proximal endoleaks. There are conflicting data regarding the risk of graft migration when oversizing by more than 30%. CONCLUSIONS Based on the best available evidence, the current standard of 10-20% oversizing regime appears to be relatively safe and preferable. Oversizing >30% might negatively impact the outcome after EVAR. Studies of higher quality are needed to further assess the relationship between proximal oversizing and the incidence of complications, particularly regarding the impact on aneurysm neck dilatation.

Dynamics of the aorta before and after endovascular aneurysm repair: a systematic review.

OBJECTIVE An overview of the knowledge of thoracic (TAA), and abdominal aortic aneurysm (AAA) dynamics, before and after endovascular repair, is given. METHODS Medline, EMBASE and the Cochrane database were searched for relevant articles. After inclusion and exclusion, 25 relevant articles reporting on aneurysm dynamics remained, allowing for comparison. Results provided in the included studies were assumed (statistically) significant if they were larger than the repeatability of the used method. RESULTS The sample size of dynamic studies is limited and translational studies are missing. Magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) were shown to have lower inter-observer variabilities than ultrasonography (US). The distension of several relevant stent-graft-landing zones during the cardiac cycle in both the abdominal and thoracic aorta are significant (mean diameter change of the AAA neck in the included studies ranged from 0.9 mm to 2.4 mm; mean area change of the thoracic aorta ranged from 4.8% to 12.7% at various levels). This distension remained preserved after stent-graft placement. Preoperatively, the renal arteries displace per heartbeat. Significant movement of the aorta in the anteroposterior (AP) and lateral direction, during the cardiac cycle, was observed. CONCLUSION The aorta exhibits a wide variety of morphologic changes throughout the cardiac cycle. CTA and MRA are reliable modalities to investigate aortic shape changes during the cardiac cycle. Significant changes per heartbeat are reported in the AAA neck and thoracic aorta. The renal artery displaces per heartbeat. The clinical relevance of dynamic imaging has not been proven yet, but dynamic changes of the aorta have to be taken into account in stent-graft selection and future stent-graft design.

The Incidence of Arterial Stent Fractures with Exclusion of Coronary, Aortic, and Non-arterial Settings

BACKGROUND This study aimed to review the literature regarding fracture of arterial stents, especially its relation to location of placement, clinical relevance, and type of stents. MATERIAL AND METHODS We searched published articles in PubMed up to February 2008 by using the terms: stent fracture or stent breakage. RESULTS Thirty-one articles met our inclusion and exclusion criteria. Most of the studies reported fractures in stents placed in the superficial femoral artery or popliteal arteries. The cumulative incidence of stent fractures ranged from 2% to 65%, i.e. 0.6 to 60 per 1000 person-months. Stent fractures occur more frequently in the superficial femoral artery and are common when multiple stents are deployed and overlap. Stent fractures are associated with a higher risk of in-stent restenosis and re-occlusion. CONCLUSION The incidence of stent fracture, its location of placement, and type of stent used were diverse across studies. Stent fracture may cause clinical deterioration especially in the femoropopliteal segment, and it should be detected before clinical manifestation appears. Further studies with larger study population involving new type of stents for a longer follow up period are warranted.

Severe Proximal Aneurysm Neck Angulation: Early Results Using the Endurant Stentgraft System

OBJECTIVE Angulation of the proximal aneurysm neck has been associated with adverse outcome after EVAR. We aim to investigate the influence of angulation on early results when using the Endurant Stentgraft System. METHODS A retrospective analysis of a prospective multicentre database identified 45 elective patients treated with the Endurant stentgraft with severe angulation of the proximal neck, which were compared to a control group without significant angulation. Endpoints were early technical and clinical success, deployment accuracy and differences in operative details. RESULTS Mean age was 74 with 86.4% males. Mean infrarenal angle (β) was 80.8° ± 16 and mean suprarenal angle (α) was 51.4° ± 21. Patients in the angulated group had larger aneurysms (mean 309 cc vs. 187 cc), shorter necks (mean 27 mm ± 14 vs. 32.6 mm ± 13) and 74% (vs. 56%) were ASA III/IV. Technical success was 100%, with one patient requiring an unplanned proximal extension. No differences were found regarding early type-I endoleaks (0% vs. 0%), major postoperative complications (6.7% vs. 6.2%; p = 0.77) or early survival (97.8% vs. 96.9%, p = 0.79). Distance from lowest renal artery to prosthesis was 2.4 mm ± 2.7 vs. 2.3 mm ± 4.8, p = 0.9. Operative details were equivalent for both groups. CONCLUSIONS Treatment with the Endurant stentgraft is technically feasible and safe, with satisfactory results in angulated and non-angulated anatomies alike. No sealing length was lost in extremely angulated cases, confirming the devices high conformability. Mid- and long-term data are awaited to verify durability, but early results are promising and challenge current opinion concerning neck angulation.

Magnetic Resonance Imaging is More Sensitive than Computed Tomography Angiography for the Detection of Endoleaks after Endovascular Abdominal Aortic Aneurysm Repair: A Systematic Review

OBJECTIVES The purpose of this systematic review was to examine whether magnetic resonance imaging (MRI) or computed tomography angiography (CTA) is more sensitive for the detection of endoleaks in patients with abdominal aortic aneurysm (AAA) after EVAR. DESIGN Systematic review. MATERIALS AND METHODS A systematic electronic search was performed. Articles were included when post-EVAR patients were evaluated by both MRI as index test and CTA as comparison. Methodological quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Primary outcome was the proportion of patients in whom MRI detected additional endoleaks, which were not seen with CTA. RESULTS Eleven articles were included. The overall methodological quality of the articles was good. In total, 369 patients with 562 MRI and 562 CTA examinations were included. A total of 146 endoleaks were detected by CTA; MRI detected all but two of these endoleaks. With MRI 132 additional endoleaks were found. CONCLUSIONS MRI is more sensitive compared to CTA for the detection of post-EVAR endoleaks, especially for the detection of type II endoleaks. MRI should be considered in patients with continued AAA growth and negative or uncertain findings at CTA.

Final results of the prospective European trial of the Endurant stent graft for endovascular abdominal aortic aneurysm repair.

OBJECTIVES The Endurant Stent Graft System (Medtronic Vascular, Santa Rosa, CA) is specifically designed to treat patients with abdominal aortic aneurysm, including those with difficult anatomies. This is the 1-year report of a prospective, non-randomised, open-label trial at 10 European centres. METHODS Between November 2007 and August 2008, 80 patients were enrolled for elective endovascular aneurysm repair (EVAR) with the Endurant; 71 with moderate (≤ 60°) and nine with high (60-75°) infrarenal aortic neck angulation. Safety and stent-graft performance were assessed throughout a 1-year follow-up period. RESULTS The device was successfully delivered and deployed in all cases. All-cause mortality was 5% (4/80), with one possibly device-related death. Serious adverse events were comparable between the high and moderate angulation groups. There were no device migrations, stent fractures, aortic ruptures or conversions to open repair. Maximal aneurysm diameter decreased >5 mm in 42.7% of cases. A total of 28 endoleaks were observed (26 type II, two undetermined). Three secondary endovascular procedures were performed for outflow vessel stenosis, graft limb occlusion and iliac extension, resulting in a secondary patency rate of 100%. No re-interventions were required in the high angulation group. CONCLUSIONS The Endurant Stent Graft was successfully delivered and deployed in all cases and performed safely and effectively in all patients, including those with unfavourable proximal neck anatomy.

Aortic Compliance following EVAR and the Influence of Different Endografts: Determination Using Dynamic MRA

Purpose: To utilize dynamic magnetic resonance angiography (MRA) to characterize aortic stiffness (β) and elastic modulus (Ep) as indexes of wall compliance during the cardiac cycle and determine any influence of different endograft designs or the presence of endoleaks on these indexes. Methods: Eleven consecutive patients (11 men; median age 74 years, range 63–78) with abdominal aortic aneurysm (AAA) selected for endovascular repair were scanned pre- and postoperatively. Aortic area and diameter changes during the cardiac cycle were determined using dynamic MRA at 4 levels: 3 cm above the renal arteries, between the renal arteries, 1 cm below the renal arteries, and at the level of maximum aneurysm sac diameter. Ep and β were calculated. Data are presented as median (range); p<0.05 was considered significant. Results: Preoperatively, Ep and β were significantly higher at the level of the aneurysm sac compared to all other levels (p<0.05). Following EVAR, stiffness increased at this level (p<0.05). After implantation, patients with an Excluder endograft demonstrated Ep and β measurements at the aneurysm neck that were 94% and 60% higher, respectively, compared to those with a Talent (p<0.05) endograft. The presence of an endoleak had no effect on Ep or β. Conclusion: This study introduces the feasibility of dynamic MRA imaging—based calculations of aortic elastic modulus and stiffness. AAA patients demonstrate increased Ep and β at the level of the aneurysm sac. EVAR results in increased aneurysm sac Ep and β. Stent-graft design seems to alter Ep and β within the aneurysm neck, which may have consequences for endograft durability. The presence of an endoleak does not seem to have an effect on Ep or β.

Pilot study of dynamic cine CT angiography for the evaluation of abdominal aortic aneurysms: Implications for endograft treatment

Purpose: To utilize 40-slice electrocardiographically (ECG)-gated cine computed tomographic angiography (CTA) to characterize normal aortic motion during the cardiac cycle at relevant anatomical landmarks in preoperative abdominal aortic aneurysm (AAA) patients. Methods: In 10 consecutive preoperative AAA patients (10 men; mean age 78.8 years, range 69–86), an ECG-gated CTA dataset was acquired on a 40-slice CT scanner using a standard radiation dose. CTA quality was graded and scan time was measured. Pulsatility measurements at multiple relevant anatomical levels were performed in the axial plane. Changes in aortic circumference were determined for both the aortic wall and the luminal diameter. Results: All 10 CT scans were of good quality. All patients could be scanned in 14 to 33 seconds (mean 21). At each anatomical level measured, there was a 2.2- to 3.4-mm increase in the aortic wall circumference per cardiac cycle. A similar increase was observed in luminal circumference, with a 2.4- to 3.6-mm increase per cycle. Conclusion: This study introduces the concept of dynamic cine CTA imaging of aortic motion, providing insight into the pathophysiology of abdominal aortic and iliac pulsations. Patients with AAAs selected for EVAR demonstrate changes in aortic circumference with each cardiac cycle that may have consequences for endograft sizing and future design. The potential for graft migration, intermittent type I endoleak, and poor patient outcome following EVAR can be anticipated. Complex aortic dynamics deserve increased scrutiny in an effort to prevent potential complications.

Aortic Pulsatile Distention in Young Healthy Volunteers is Asymmetric : Analysis with ECG-gated MRI

OBJECTIVE Knowledge of aortic shape changes throughout the cardiac cycle can offer improved understanding of vascular pathophysiology and may have crucial impact on stentgraft design and EVAR durability. To understand underlying mechanisms of dynamic changes in aortic aneurysm (neck) morphology, the undiseased aorta has to be studied first. Objective is to visualize and characterize dynamic aortic shape changes in young healthy volunteers. MATERIALS AND METHODS Fifteen healthy volunteers (7 male, median age 24 year, range 18-28) were scanned using ECG-gated balanced gradient-echo MRI, with 16 reconstructed cardiac phases. Transverse scans were made perpendicular to the aorta: (A) above the aortic bifurcation, (B) infrarenal, (C) juxtarenal, (D) suprarenal and (E) above the celiac trunk. After aortic lumen segmentation, radial changes during the cardiac cycle were measured, from the center of mass, over 360 degrees, and plotted. An ellipse was fitted over the distention plots, yielding the direction (AP:0 degrees, Right: -90 degrees, Left: 90 degrees ) and magnitude of radius change over the major and minor axis. RESULTS Asymmetric distention was observed, with a variable rate per patient and level. Radius changes decreased from the proximal to distal aorta. Radius changes over the major axis ranged from 14% to 41%. At level A mean change in radius over the minor versus major axis was 1.4+/-0.2mm (17%) versus 1.6+/-0.2mm (20%), respectively. At B 1.7+/-0.4mm (22%) versus 2.0+/-0.4mm (25%), at C 1.7+/-0.4mm (22%) versus 2.2+/-0.4mm (27%) at D 2.0+/-0.4mm (25%) versus 2.4+/-0.5mm (30%) and at E 2.2+/-0.3mm (27%) versus 2.6+/-0.3mm (32%). Mean orientation of the major axis was (A) 0.8+/-23.3 degrees , (B) 1.8+/-31.3 degrees , (C) 14.0+/-15.5 degrees , (D) -28.8+/-48.0 degrees and (E) 18.4+/-22.2 degrees. CONCLUSIONS Aortic pulsatile distention in young healthy volunteers is asymmetric, with up to 41% radius change in the descending aorta. This study offers a frame of reference for dynamic imaging studies in patients with aortic pathology and provides a valuable non-invasive tool for future research into aortic distention, development and localization of vascular pathology.