Follow-up evaluation of endoluminally treated abdominal aortic aneurysms with duplex ultrasonography: validation with computed tomography

Comparative Analysis of Micro-Computed Tomography and 3D Micro-Ultrasound for Measurement of the Mouse Aorta

Aortic aneurysms, life-threatening and often undetected until they cause sudden death, occur when the aorta dilates beyond 1.5 times its normal size. This study used ultrasound scans and micro-computed tomography to monitor and measure aortic volume in preclinical settings, comparing it to the well-established measurement using ultrasound scans. The reproducibility of measurements was also examined for intra- and inter-observer variability, with both modalities used on 8-week-old C57BL6 mice. For inter-observer variability, the μCT (micro-computed tomography) measurements for the thoracic, abdominal, and whole aorta between observers were highly consistent, showing a strong positive correlation (R2 = 0.80, 0.80, 0.95, respectively) and no significant variability (p-value: 0.03, 0.03, 0.004, respectively). The intra-observer variability for thoracic, abdominal, and whole aorta scans demonstrated a significant positive correlation (R2 = 0.99, 0.96, 0.87, respectively) and low variability (p-values = 0.0004, 0.002, 0.01, respectively). The comparison between μCT and USS (ultrasound) in the suprarenal and infrarenal aorta showed no significant difference (p-value = 0.20 and 0.21, respectively). μCT provided significantly higher aortic volume measurements compared to USS. The reproducibility of USS and μCT measurements was consistent, showing minimal variance among observers. These findings suggest that μCT is a reliable alternative for comprehensive aortic phenotyping, consistent with clinical findings in human data.

Computed Tomography Angiography for Aortic Diseases

Aortic pathologies encompass a heterogeneous group of disorders, including acute aortic syndrome, traumatic aortic injury , aneurysm, aortitis, and atherosclerosis. The clinical manifestations of these disorders can be varied and non-specific, ranging from acute presentations in the emergency department to chronic incidental findings in an outpatient setting. Given the non-specific nature of their clinical presentations, the reliance on non-invasive imaging for screening, definitive diagnosis, therapeutic strategy planning, and post-intervention surveillance has become paramount. Commonly used imaging modalities include ultrasound, computed tomography (CT), and MR imaging. Among these modalities, computed tomography angiography (CTA) has emerged as a first-line imaging modality owing to its excellent anatomic detail, widespread availability, established imaging protocols, evidence-proven indications, and rapid acquisition time.

Peripheral Arterial Disease: A Narrative Review

Peripheral arterial disease (PAD) describes the partial or complete occlusion of blood flow in the distal arteries of the body. A decreased arterial patency may occur due to a reduction in the elasticity or diameter of the vessel. The goal of interventions is to decrease incidence and reduce complications by identifying and minimizing the primary causes. This paper discusses PAD affecting the aortoiliac, common femoral, and femoropopliteal arteries. In a significant portion of the population, PAD may lack usual symptoms such as limb pain, claudication, and diminished pulses. Imaging techniques become crucial to ensuring timely diagnosis, monitoring treatment effectiveness, and preventing recurrence. Duplex ultrasound (DUS) is a cheap and non-invasive preliminary technique to detect atherosclerotic plaques and grade arterial stenosis. Magnetic resonance angiography (MRA) provides the added advantage of minimizing artifacts. Digital subtraction angiography (DSA) remains the gold standard for grading the degree of stenosis but is only employed second-line to DUS or MRA due to the high dose of nephrotoxic contrast. Computed tomography angiography (CTA) is able to overcome the anatomical limitations of DUS and MRA and proves to be a suitable alternative to DSA in patients with renal disease. Preventative measures involve monitoring blood pressure, cholesterol levels, and tobacco usage. First-line treatment options include endovascular procedures as well as surgical interventions in cases of significant arterial involvement. Endovascular treatments involve the use of balloon angioplasty, drug-coated balloons, and drug-coated stents, to name a few, that serve as minimally invasive techniques to manage PAD. Surgical procedures, although more complex, are considered gold-standard treatment options for long and intricate lesions. Endovascular methods are generally preferred over surgical options as the complication risk is severely reduced and the rates of reintervention are comparable to surgical options.

Colour Duplex and/or Contrast-Enhanced Ultrasound Compared with Computed Tomography Angiography for Endoleak Detection after Endovascular Abdominal Aortic Aneurysm Repair: A Systematic Review and Meta-Analysis

This study aims to assess the role of Color Duplex Ultrasound with or without contrast media for surveillance following endovascular aortic aneurysm repair (EVAR). A systematic search of the literature published until April 2022 was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The pooled rates of endoleak detection through Contrast-Enhanced or Color Duplex Ultrasound (CEUS or CDUS) and Computed Tomography Angiography (CTA) with 95% confidence intervals (CIs) were estimated using random-effect analysis. Thirty-eight studies were considered eligible for inclusion. The total number of patients in the included studies was 5214 between 1997 and 2021. The overall pooled rate of endoleak detection using CDUS and CTA was 82.59% and 97.22%, while the rates for CEUS and CTA were 96.67% and 92.82%, respectively. The findings of the present study support the use of the CEUS for endoleak detection. However, it should be integrated into institutional protocols for EVAR surveillance to further evaluate its clinical utility in the post-EVAR period before it can be recommended as the sole imaging modality after EVAR.

Efficacy of contrast-enhanced ultrasound in detection of type II endoleak after abdominal aortic aneurysm surgery: A prospective cohort study

PURPOSE

This study aimed to evaluate the efficacy of conventional contrast-enhanced ultrasound (CEUS) in detection of type II endoleak after endovascular abdominal aortic aneurysm repair (EVAR).

METHODS

From January 2015 to April 2018, 205 patients underwent EVAR were included. CEUS and computed tomography angiography (CTA) were performed at 1-month follow-up postoperatively to detect type II endoleak. CEUS was performed at 3- and 6-month follow-up to evaluate the development of type II endoleak. The diameter extension of type II endoleak increased greater than 5 mm was defined as enlarge group, and that increased less than 5 mm was defined as stable group. The difference of arrival time (AT) of contrast agent, maximum cross-sectional area (MCSA) of contrast agent and the blood flow velocity (BFV) of the abnormal blood around the stent graft were compared.

RESULTS

At 1-month after EVAR, 65 cases of endoleak were detected by CEUS, including 25 cases of type I, 30 cases of type II endoleak and 10 cases of type III endoleak. Among them, 50 cases were also detected by CTA. The diameter extension of 12 cases of type II endoleak increased greater than 5 mm, and that of eight cases increased less than 5 mm. The average AT of the enlarge group was significantly shorter than that of the stable group, while the MCSA of contrast agent and the BFV were significantly higher than that of the stable group (p < 0.05).

CONCLUSION

CEUS has predictive value for the natural outcome of type II endoleak.

CT angiography for the assessment of EVAR complications: a pictorial review

Endovascular aneurysm repair (EVAR) is a minimally invasive treatment proposed as an alternative to open repair in patients with abdominal aortic aneurysms. EVAR consists in a stent-graft placement within the aorta in order to exclude the aneurysm from arterial circulation and reduce the risk of rupture. Knowledge of the various types of devices is mandatory because some stents/grafts are more frequently associated with complications. CT angiography is the gold standard diagnostic technique for preprocedural planning and postprocedural surveillance. EVAR needs long-term follow-up due to the high rate of complications. Complications can be divided in endograft device-related and systemic complications. The purpose of this article is to review the CT imaging findings of EVAR complications and the key features for the diagnosis.

Can we replace computed tomography angiography by contrast-enhanced ultrasound in the surveillance of patients submitted to aortoiliac aneurysm repair?

OBJECTIVES

This study was designed for evaluation of CEUS (contrast-enhanced ultrasound) for the detection of endoleaks after EVAR (endovascular aortic aneurysms repair) as an alternative to CTA (computed tomography angiography), the gold standard in post-EVAR surveillance.

METHODS

Post-EVAR surveillance of patients who underwent CEUS and CTA was retrospectively analyzed to compare the accuracy of CEUS compared to CTA. For that, the following parameters were analyzed: the largest aneurysm diameter, type of endoleaks, and the time elapsed after EVAR using both surveillance tests.

RESULTS

The study involved 110 pairs of exams in patients with infrarenal aortoiliac or isolated iliac artery aneurysm, covering predominantly a male population (89%). The time elapsed after EVAR using CEUS or CTA exams were statistically similar, ranging from one to 58 months (mean 12.2) and one to 65 months (mean 9.7), respectively (p = 0.124). CEUS sensitivity was 75.5%, specificity 96.7%, false positives were 24.5%, and false negatives were 3.3%. The accuracy between the two exams was 87.3%. A secondary analysis, comparing CTA with CEUS as a reference standard, revealed CEUS sensitivity of 24.5%, higher than CTA for detecting endoleaks, with a concordance rate of true positive results of 75.5%. Among the endoleaks detected solely by CEUS (12 cases), one case was type Ia and eleven were type II, while those detected only by CTA (2 cases), one was type Ia and one type II. Additionally, a type II endoleak associated with type Ib, identified by CEUS, was seen as type II for CTA only. There was no difference between the pre-EVAR and the post-EVAR diameters of aortoiliac aneurysm (p = 0.058), both for CEUS and CTA. Computed tomography angiography, on the other hand, showed significant aneurysm diameter reduction compared to CEUS for isolated iliac artery aneurysms (p < 0.001).

CONCLUSION

Contrast-enhanced ultrasound was more effective than CTA in identifying and characterizing endoleaks in patients undergoing EVAR, especially type II endoleaks. The advantages include efficacy and, particularly, safety, and must be considered in EVAR surveillance protocols so that its use becomes widespread. We understand that CEUS, as a surveillance exam, considerably reduces risks to patients compared to CTA.

General principles and overview of vascular contrast-enhanced ultrasonography

Ultrasonography (US) is the first-line modality for the evaluation of vascular pathology. Although well-established for many diseases, US has inherent limitations that can occasionally hinder an accurate diagnosis. The value of US was improved by the introduction of microbubbles as ultrasonographic contrast agents (UCAs) and the emergence of contrast-enhanced ultrasonography (CEUS), following the introduction of second-generation UCAs and the emergence of modern contrast-specific techniques. CEUS offers valuable information about vascular disease, both on a macrovascular and a microvascular level, with well-established applications for carotid disease, post-interventional follow-up of abdominal aortic aneurysms, and the assessment of portal vein thrombosis. The purpose of this review is to discuss the principles of CEUS and to present an overview of its vascular applications.

Contemporary imaging methods for the follow-up after endovascular abdominal aneurysm repair: a review

Abdominal aortic aneurysm (AAA) is defined as a localized enlargement of the aortic cross-section where the diameter is greater than 3 cm or more than 50% larger than the diameter in a normal segment. The most important complication of AAA is rupture, which, if untreated, results in mortality rates of up to 90%. Conventional open surgical repair is associated with significant 30-day mortality. Endovascular aneurysm repair (EVAR) is a significantly less invasive procedure; it is related to a lower early mortality rate and a lower number of perioperative complications. Although EVAR is a minimally invasive technique, lifelong follow-up imaging is necessary due to possible late complications including endoleak, recurrent aneurysm formation, graft infection, migration, kinking and thrombosis. The total rate of complications after EVAR is estimated at approximately 30%, and the rate of complications that require intervention is 2–3%. Early detection and progression analysis of such situations is crucial for proper intervention.

Editor's Choice - Systematic Review and Meta-Analysis of the Outcome of Treatment for Type II Endoleak Following Endovascular Aneurysm Repair

OBJECTIVES

The efficacy and need for secondary interventions for type II endoleaks following endovascular abdominal aortic aneurysm repair (EVAR) remain controversial. This systematic review aimed at investigating the clinical outcomes of different type II endoleak treatments in patients with a persistent type II endoleak after EVAR.

DATA SOURCES

Embase, Medline via Ovid, Web of Science Core Collection, the Cochrane CENTRAL, and Google Scholar.

REVIEW METHODS

This systematic review was performed in accordance with the PRISMA Statement. Outcomes of interest were technical and clinical success, change in sac diameter, complications, need for additional interventions, abdominal aortic aneurysm (AAA) rupture, and (AAA related) mortality. Meta-analyses were performed with random effects models.

RESULTS

A total of 59 studies were included, with a cumulative cohort of 1073 patients with persistent type II endoleak. Peri-operative complications following treatment of type II endoleaks occurred in 3.8% of patients (95% CI 2.7-5.2%), and AAA related mortality was 1.8% (95% CI 1.1-2.7%). Overall technical success was 87.9% (95% CI 83.1-92.1%), while clinical success was 68.4% (95% CI 61.2-75.1%). Among studies detailing sac dynamics, decrease or stable sac, with or without resolution, was achieved in 78.4% (95% CI 70.2-85.6%). Changes in sac diameter following type II endoleak treatment were documented in 157 patients to at least 24 months. Within this group an actual decrease in sac diameter was reported in only 27 of 40 patients.

CONCLUSION

There is little evidence supporting the efficacy of secondary intervention for type II endoleaks after EVAR. Although generally safe, the lack of evidence supporting the efficacy of type II endoleak treatment leads to difficulty in assessing its merits.

A Comparative Study of Ultrasound and Computed Tomography Scan for the follow-up of Abdominal Aortic Aneurysms after Endovascular Repair

Objective

To date, computed tomography (CT) scanning has been the gold standard for follow-up of abdominal aortic aneurysms (AAA) after endovascular repair (EVR). However, with increasing durability of the minimally invasive procedure and longer survival of patients, there is concern over the expense of CT and its associated risks. For this reason, many now believe that ultrasound (US) may be an adequate substitute for surveillance of patients after EVR. The aim of this study was to compare ultrasound and CT scan in our practice to ascertain whether ultrasound alone would be sufficient for follow-up of AAA patients after EVR.

Materials and Methods

A total of 121 patients underwent EVR of AAAs during a 6-year period. All patients were followed up annually using both CT scanning and US. The parameters assessed included the presence/absence of endoleaks, as well as diameters of the aneurysm sac and neck. Results were plotted graphically to determine the change in size of aneurysms over time, and patients with endoleaks were compared with those who had no endoleaks. The sensitivity, specificity, positive, and negative predictive values for detecting endoleaks was also calculated for US and CT. Normally distributed data were analyzed using the Student's t-test and the Wilcox-signed rank test was used for nonparametric data.

Results

A total of 573 (CT and US) scans were analyzed. Of these, 391 scans (91 patients) did not show endoleaks. There were 64 scans (18 patients) in which both CT and US detected endoleaks; 6 scans (6 patients) in which CT detected leaks and US did not; and 5 scans (4 patients) in which US detected leaks and CT did not. The aneurysm sac size increased over time in the endoleak group and decreased over time in the nonendoleak group, whereas neck sizes did not change in either patient group. The sensitivity, specificity, positive, and negative predictive values of US and CT scan for detecting endoleak were 92.7%, 98.5%, 91.4%, and 98.7%; and 91.4%, 98.7%, 92.7%, and 98.5% respectively.

Conclusion

In our practice, US was comparable with CT scan for the detection of endoleaks, and similar trends were seen over time with regard to changes in aneurysm neck and body sizes for both modalities. We believe that US should be the primary modality for follow-up of patients after EVR and that CT scan should be reserved for confirmation of endoleak where this is suspected.

Angiotensin II Infusion Does Not Cause Abdominal Aortic Aneurysms in Apolipoprotein E-Deficient Rats

The apolipoprotein E-deficient (apoE-/-) mouse model has advanced our understanding of cardiovascular disease mechanisms and experimental therapeutics. This spontaneous model recapitulates aspects of human atherosclerosis, and allows for the development of dissecting abdominal aortic aneurysms (AAAs) when combined with angiotensin II. We characterized apoE-/- rats and hypothesized that, similar to mice, they would develop dissecting AAAs. We created rats with a 16-bp deletion of the apoE gene using transcription activator-like effector nucleases. We imaged the suprarenal aorta for 28 days after implantation of miniosmotic pumps that infuse angiotensin II (AngII, 200 ng/kg/min). Blood pressure (BP), serum lipids and lipoproteins, and histology were also analyzed. These rats did not develop pathological aortic dissection, but we did observe a decrease in circumferential cyclic strain, a rise in BP, and microstructural changes in the aortic medial layer. We also measured increased serum lipids with and without administration of a high-fat diet, but did not detect atherosclerotic plaques. Chronic infusion of AngII did not lead to the formation of dissecting AAAs or atherosclerosis in the rats used in this study. While reduced amounts of atherosclerosis may explain this resistance to dissecting aneurysms, further investigation is needed to fully characterize species-specific differences.

Ultrasonography for endoleak detection after endoluminal abdominal aortic aneurysm repair

BACKGROUND

People with abdominal aortic aneurysm who receive endovascular aneurysm repair (EVAR) need lifetime surveillance to detect potential endoleaks. Endoleak is defined as persistent blood flow within the aneurysm sac following EVAR. Computed tomography (CT) angiography is considered the reference standard for endoleak surveillance. Colour duplex ultrasound (CDUS) and contrast-enhanced CDUS (CE-CDUS) are less invasive but considered less accurate than CT.

OBJECTIVES

To determine the diagnostic accuracy of colour duplex ultrasound (CDUS) and contrast-enhanced-colour duplex ultrasound (CE-CDUS) in terms of sensitivity and specificity for endoleak detection after endoluminal abdominal aortic aneurysm repair (EVAR).

SEARCH METHODS

We searched MEDLINE, Embase, LILACS, ISI Conference Proceedings, Zetoc, and trial registries in June 2016 without language restrictions and without use of filters to maximize sensitivity.

SELECTION CRITERIA

Any cross-sectional diagnostic study evaluating participants who received EVAR by both ultrasound (with or without contrast) and CT scan assessed at regular intervals.

DATA COLLECTION AND ANALYSIS

Two pairs of review authors independently extracted data and assessed quality of included studies using the QUADAS 1 tool. A third review author resolved discrepancies. The unit of analysis was number of participants for the primary analysis and number of scans performed for the secondary analysis. We carried out a meta-analysis to estimate sensitivity and specificity of CDUS or CE-CDUS using a bivariate model. We analysed each index test separately. As potential sources of heterogeneity, we explored year of publication, characteristics of included participants (age and gender), direction of the study (retrospective, prospective), country of origin, number of CDUS operators, and ultrasound manufacturer.

MAIN RESULTS

We identified 42 primary studies with 4220 participants. Twenty studies provided accuracy data based on the number of individual participants (seven of which provided data with and without the use of contrast). Sixteen of these studies evaluated the accuracy of CDUS. These studies were generally of moderate to low quality: only three studies fulfilled all the QUADAS items; in six (40%) of the studies, the delay between the tests was unclear or longer than four weeks; in eight (50%), the blinding of either the index test or the reference standard was not clearly reported or was not performed; and in two studies (12%), the interpretation of the reference standard was not clearly reported. Eleven studies evaluated the accuracy of CE-CDUS. These studies were of better quality than the CDUS studies: five (45%) studies fulfilled all the QUADAS items; four (36%) did not report clearly the blinding interpretation of the reference standard; and two (18%) did not clearly report the delay between the two tests.Based on the bivariate model, the summary estimates for CDUS were 0.82 (95% confidence interval (CI) 0.66 to 0.91) for sensitivity and 0.93 (95% CI 0.87 to 0.96) for specificity whereas for CE-CDUS the estimates were 0.94 (95% CI 0.85 to 0.98) for sensitivity and 0.95 (95% CI 0.90 to 0.98) for specificity. Regression analysis showed that CE-CDUS was superior to CDUS in terms of sensitivity (LR Chi² = 5.08, 1 degree of freedom (df); P = 0.0242 for model improvement).Seven studies provided estimates before and after administration of contrast. Sensitivity before contrast was 0.67 (95% CI 0.47 to 0.83) and after contrast was 0.97 (95% CI 0.92 to 0.99). The improvement in sensitivity with of contrast use was statistically significant (LR Chi² = 13.47, 1 df; P = 0.0002 for model improvement).Regression testing showed evidence of statistically significant effect bias related to year of publication and study quality within individual participants based CDUS studies. Sensitivity estimates were higher in the studies published before 2006 than the estimates obtained from studies published in 2006 or later (P < 0.001); and studies judged as low/unclear quality provided higher estimates in sensitivity. When regression testing was applied to the individual based CE-CDUS studies, none of the items, namely direction of the study design, quality, and age, were identified as a source of heterogeneity.Twenty-two studies provided accuracy data based on number of scans performed (of which four provided data with and without the use of contrast). Analysis of the studies that provided scan based data showed similar results. Summary estimates for CDUS (18 studies) showed 0.72 (95% CI 0.55 to 0.85) for sensitivity and 0.95 (95% CI 0.90 to 0.96) for specificity whereas summary estimates for CE-CDUS (eight studies) were 0.91 (95% CI 0.68 to 0.98) for sensitivity and 0.89 (95% CI 0.71 to 0.96) for specificity.

AUTHORS' CONCLUSIONS

This review demonstrates that both ultrasound modalities (with or without contrast) showed high specificity. For ruling in endoleaks, CE-CDUS appears superior to CDUS. In an endoleak surveillance programme CE-CDUS can be introduced as a routine diagnostic modality followed by CT scan only when the ultrasound is positive to establish the type of endoleak and the subsequent therapeutic management.

A Systematic Review of Ultrasound or Magnetic Resonance Imaging Compared With Computed Tomography for Endoleak Detection and Aneurysm Diameter Measurement After Endovascular Aneurysm Repair

PURPOSE

To analyze the literature comparing ultrasound [duplex (DUS) or contrast-enhanced (CEUS)] or magnetic resonance imaging (MRI) with computed tomography angiography (CTA) for endoleak detection and aneurysm diameter measurement after endovascular aneurysm repair (EVAR).

METHODS

A systematic review identified 31 studies that included 3853 EVAR patients who had paired scans (DUS or CEUS vs CTA or MRI vs CTA) within a 1-month interval for identification of endoleaks during EVAR surveillance. The primary outcome was the number of patients with an endoleak detected by one test but undetected by another test. Results are presented for all endoleaks and for types I and III endoleaks only. Aneurysm diameter measurements between CTA and ultrasound were examined using meta-analysis.

RESULTS

Endoleaks were seen in 25.6% (985/3853) of patients after EVAR. Fifteen studies compared DUS with CTA for the detection of all endoleak types. CTA had a significantly higher proportion of additional endoleaks detected (214/2346 vs 77/2346 for DUS). Of 19 studies comparing CEUS with CTA for the detection of all endoleak types, CEUS was more sensitive (138/1694) vs CTA (51/1694). MRI detected 42 additional endoleaks that were undetected by CTA during the paired scans, whereas CTA detected 2 additional endoleaks that MRI did not show. CTA had a similar proportion of additional types I and III endoleaks undetected by CEUS or MRI. Of 9 studies comparing ultrasound vs CTA for post-EVAR aneurysm diameter measurement, the aneurysm diameter measured by CTA was greater than ultrasound (mean difference -1.70 mm, 95% confidence interval -2.45 to -0.96, p<0.001).

CONCLUSION

This study demonstrated that CEUS and MRI are more accurate than CTA for the detection of post-EVAR endoleaks, but they are no better than CTA for detecting types I and III endoleaks specifically. Aneurysm diameter differences between CTA and ultrasound should be considered when evaluating the change in aneurysm diameter postoperatively.

The emergency medicine approach to abdominal vascular graft complications

INTRODUCTION

Abdominal aortic aneurysm (AAA) is a deadly condition, particularly with rupture. Emergency physicians provide vital frontline care to the diagnosis and treatment of this disease. Endovascular aortic repair (EVAR) has become the gold standard for treatment of AAA, but the management of EVAR complications is not well discussed in the emergency medicine literature.

OBJECTIVE OF THIS REVIEW

The purpose of this article is to provide an emergency medicine-focused review of the complications of EVAR.

DISCUSSION

Although many complications may arise after AAA repair, the most common include aortoenteric fistula, endoleak, limb ischemia, and graft infection. All potential complications should receive vascular surgery consultation and hemodynamic resuscitation. Aortoenteric fistula often presents nonspecifically with gastrointestinal (GI) bleeding, abdominal pain, and vomiting. Computed tomography with intravenous contrast is required for diagnosis. An endoleak is defined by vascular flow outside of the graft. The optimal diagnostic modality includes triple phase computed tomographic scan (noncontrast, arterial, delayed phase). Limb ischemia may occur before 2 months, or in a later period, with symptoms ranging from claudication to complete neurovascular compromise. Graft infection is most commonly due to Staphylococcus aureus, and imaging can suggest the diagnosis. Definitive diagnosis requires tissue or fluid sampling. Through an understanding of these complications, emergency physicians may improve patient outcomes.

CONCLUSIONS

With the growing use of EVAR, emergency physician exposure to complications of this procedure is increasing. Knowledge of the complication presentations, diagnoses, and management can play an integral role patient care.

Diagnostic imaging methods applied in long-term surveillance after EVAR. Will computed tomography angiography be replaced by other methods?

Endovascular implantation of a stent graft in the abdominal aorta (endovascular aneurysm repair – EVAR) is a widely accepted alternative to open surgery in treatment of abdominal aortic aneurysms. Although EVAR is connected with a significant reduction in the risk of peri- and post-operative complications, it does not eliminate them totally. Long-term surveillance of post-EVAR patients is aimed at early detection of and fast reaction to a group of complications called endovascular leaks. Currently, the gold standard in leak diagnostics is computed tomography angiography (CTA). The other methods are ultrasonography, magnetic resonance (MR) angiography, intra-aneurysm sac pressure measurement, X-ray, and digital subtraction angiography (DSA). Despite many analyses based on long-term research, emphasising the high value and competitiveness of less invasive tests such as US or X-ray compared to CTA, it is still difficult for them to win the trust and acceptance of clinicians. The persisting view is that computed tomography is the test that finally resolves any inaccuracies. Consequently, a patient with a number of concurrent diseases is subject to absurdly high radiation exposure and effects of a radiocontrast agent within a short time. It is therefore logical to acknowledge that the EVAR-related risk is catching up with the open surgery risk, while the endovascular procedure is much more costly. Nevertheless, the status of CTA as the gold standard ultimately seems to be unthreatened. This paper presents a description of the diagnostic imaging tests that make it possible to detect any vascular leaks and to develop strategies for therapeutic processes.

Contrast-enhanced ultrasound after endovascular aortic repair-current status and future perspectives

An increasing number of patients with abdominal aortic aneurysms (AAAs) are undergoing endovascular aortic repair (EVAR) instead of open surgery. These patients require lifelong surveillance, and the follow-up imaging modality of choice has been traditionally computed tomography angiography (CTA). Repetitive CTA imaging is associated with cumulative radiation exposure and requires the administration of multiple doses of nephrotoxic contrast agents. Contrast-enhanced ultrasound (CEUS) has emerged as an alternative strategy in the follow-up of patients with EVAR and demonstrates high sensitivity and specificity for detection of endoleaks. In fact, a series of studies have shown that CEUS is at least performing equal to computed tomography for the detection and classification of endoleaks. This article summarizes current evidence of CEUS after EVAR and demonstrates its usefulness via various patient cases.

Surveillance Imaging Following Endovascular Aneurysm Repair

There is a significant risk of complication following endovascular abdominal repair (EVAR), including endoleak, graft translocation, thrombosis, and infection. Surveillance imaging is important for detecting EVAR complication. Surveillance modalities include conventional X-ray, computed tomography, magnetic resonance imaging, ultrasound, and conventional angiography, with inherent advantages and drawbacks to each modality. The authors present common complications following EVAR, and recent advances in the key modalities for surveillance.

Comparison of colour duplex ultrasound with computed tomography to measure the maximum abdominal aortic aneurysmal diameter

Introduction. Maximum diameter of an abdominal aortic aneurysm (AAA) is the main indication for surgery. This study compared colour duplex ultrasound (CDU) and computed tomography (CT) in assessing AAA diameter. Patients and Methods. Patients were included if they had both scans performed within 90 days. Pearson's correlation coefficient, paired t-test, and limits of agreement (LOA) were calculated for the whole group. Subgroup analysis of small (<5.0 cm), medium (5.0-6.5 cm), and large (>6.5 cm) aneurysms was performed. A P value of <0.05 was considered statistically significant. Results. 389 patients were included, giving 130 pairs of tests for comparison. Excellent correlation was in the whole group (r = 0.95) and in the subgroups (r = 0.94; 0.69; 0.96, resp.). Small LOA between the two imaging modalities was found in all subgroups. Conclusion. Small aneurysms can be accurately measured using CDU. CDU is preferable for small AAAs, but cannot supplant CT for planning aortic intervention.

Essentials of endovascular abdominal aortic aneurysm repair imaging: postprocedure surveillance and complications

OBJECTIVE

Lifelong postprocedural imaging surveillance is necessary after endovascular abdominal aortic aneurysm repair (EVAR) to assess for complications of endograft placement, as well as device failure and continued aneurysm growth. Refinement of the surveillance CT technique and development of ultrasound and MRI protocols are important to limit radiation exposure.

CONCLUSION

A comprehensive understanding of EVAR surveillance is necessary to identify life-threatening complications and to aid in secondary treatment planning.

Duplex Ultrasound versus Computed Tomography for the Postoperative Follow-Up of Endovascular Abdominal Aortic Aneurysm Repair. Where Do We Stand Now?

In the last decade, endovascular aneurysm repair (EVAR) has rapidly developed to be the preferred method for infrarenal abdominal aortic aneurysm repair in patients with suitable anatomy. EVAR offers the advantage of lower perioperative mortality and morbidity but carries the cost of device-related complications such as endoleak, graft migration, graft thrombosis, and structural graft failure. These complications mandate a lifelong surveillance of EVAR patients and their endografts. The purpose of this study is to review and evaluate the safety of color-duplex ultrasound (CDU) as compared with computed tomography (CT), based on the current literature, for post-EVAR surveillance. The post-EVAR follow-up modalities, CDU versus CT, are evaluated questioning three parameters: (1) accuracy of aneurysm size, (2) detection and classification of endoleaks, and (3) detection of stent-graft deformation. Studies comparing CDU with CT scan for investigation of post-EVAR complications have produced mixed results. Further and long-term research is needed to evaluate the efficacy of CDU versus CT, before CDU can be recommended as the primary imaging modality for EVAR surveillance, in place of CT for stable aneurysms.

Vascular ultrasonography for follow-up of endovascular repair of abdominal aorta aneurysms

BackgroundThere is little information available on follow-up of abdominal aortic aneurysm patients treated with endovascular repair using vascular ultrasonography in Brazil or on how it compares with the results of angiotomography. Since ultrasonography is an examination that is risk-free, inexpensive and widely available, it is a very attractive method. In this study we attempted to evaluate the sensitivity and specificity of vascular ultrasonography for follow-up of these patients by comparing the method with angiotomography.Materials and methodsWe conducted a prospective study from June 2012 to May 2013. We examined patients followed-up at the endovascular surgery clinic run by the University Hospital of Londrina after endovascular repair of abdominal aortic aneurysms. All patients underwent angiotomography for follow-up and were also examined using simple abdominal X-rays and vascular ultrasonography.ResultsA total of 30 patients were analyzed, with a mean age of 73 years and a mean aneurysm diameter of 6 cm. Four endoleaks were detected. Vascular ultrasonography achieved sensitivity of 75% and specificity of 96% for classification of these endoleaks, in comparison with angiotomography.ConclusionsVascular ultrasonography is an excellent primary method for evaluation and post-surgical follow-up of patients treated with endovascular repair of abdominal aorta aneurysms. However, when ultrasonography detects problems or is difficult to accomplish, it should be supplemented with a more specific investigation for diagnostic confirmation.

Molecular imaging of experimental abdominal aortic aneurysms

Current laboratory research in the field of abdominal aortic aneurysm (AAA) disease often utilizes small animal experimental models induced by genetic manipulation or chemical application. This has led to the use and development of multiple high-resolution molecular imaging modalities capable of tracking disease progression, quantifying the role of inflammation, and evaluating the effects of potential therapeutics. In vivo imaging reduces the number of research animals used, provides molecular and cellular information, and allows for longitudinal studies, a necessity when tracking vessel expansion in a single animal. This review outlines developments of both established and emerging molecular imaging techniques used to study AAA disease. Beyond the typical modalities used for anatomical imaging, which include ultrasound (US) and computed tomography (CT), previous molecular imaging efforts have used magnetic resonance (MR), near-infrared fluorescence (NIRF), bioluminescence, single-photon emission computed tomography (SPECT), and positron emission tomography (PET). Mouse and rat AAA models will hopefully provide insight into potential disease mechanisms, and the development of advanced molecular imaging techniques, if clinically useful, may have translational potential. These efforts could help improve the management of aneurysms and better evaluate the therapeutic potential of new treatments for human AAA disease.

Surveillance of Endovascular Aneurysm Repair: An Audit of Sonographer-Led Ultrasound and Radiologist-Led Computed Tomography Services

Objectives

Postoperative complications associated with endovascular aneurysm repair (EVAR) mandate the need for lifelong surveillance. The aim of this audit was to compare the detection rates of endoleaks during the first 10 months of a combined sonographer-led colour Doppler ultrasound (CDUS) and radiologist-led contrast-enhanced computed tomography (CECT), postoperative EVAR surveillance programme, within a single National Health Service Hospital.

Methods

A prospective audit was carried out of all patients with EVAR, who had same-day CECT and CDUS surveillance examinations between March 2010 and January 2011. CECT examinations were reported by three consultant vascular radiologists. Of 66 CDUS examinations, 64 (97%) were performed and reported by four certified vascular sonographers. The reports of dual-modality, same-day scans were compared, to establish agreement on the presence and classification of the type, or absence of endoleaks. CECT was used as the gold standard, against which the sensitivity and specificity of CDUS in endoleak detection was determined.

Results

Sixty-six paired same-day CECT and CDUS reports were compared. Ten endoleaks were identified by CECT (15% incidence) and eight (80%) of 10 were type II. The number of observed agreements was 58 (88%) of 66; CDUS missed six endoleaks (five type II) and suggested two false-positives. CDUS had a sensitivity of 40% and a specificity of 96%. Conclusions: In our study, CDUS demonstrated an excellent specificity but had a low sensitivity for endoleak detection. We agree CDUS cannot effectively replace CECT as the sole imaging modality. Research to determine an international consensus for an effective and efficient postoperative EVAR surveillance patient pathway is required.

Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans?

BACKGROUND

Simplifying a postoperative surveillance protocol for endovascular aneurysm repair (EVAR) requires quality control comparing computerized tomography (CT) and ultrasound (US) results of abdominal aortic aneurysm (AAA) diameter measurements and endoleaks.

PURPOSE

To test if US is comparable to CT, then assess a simplified follow-up with our conventional surveillance to assess patient safety.

MATERIAL AND METHODS

During 2001-2006, data on 56 patients treated with Talent stent graft were prospectively registered. Median follow-up was 41.5 months (range, 2-94 months), with CT, US, and plain film abdomen X-rays (PFA) at 1, 6, and 12 months, then yearly. Bland-Altman plot was used to assess the agreement between CT and US measuring the AAA diameters and mixed model by the time effect to assess the difference in diameter over time. Sensitivity and specificity for detection of endoleaks by US, with CT as 'gold standard' were calculated. A simplified surveillance protocol with US/PFA at 6 and 8 weeks, CT/US/PFA at 1 year, and yearly US/PFA thereafter, was evaluated. CT was carried out when poor visibility, endoleak detected, AAA diameter increase (≥5 mm) on US or migration (≥10 mm) on PFA. This regime was compared with our conventional follow-up protocol.

RESULTS

Diameter measurements on US appear comparable to CT with 91% specificity and 85% sensitivity for endoleaks detected by US. Using the simplified surveillance protocol no endoleaks, migrations, or endotension requiring treatment were overlooked. The simplified protocol generated 53 selective CT scans, avoiding approximately 144 CT scans. If further simplified by omitting the 1-year CT scan, one type II endoleak would be missed with a 1-year delay, eliminating a further 45 CT scans.

CONCLUSION

US appears comparable to CT in the follow-up of Talent stent grafts in our institution. The proposed simplified surveillance protocol seems safe and can lead to a significant reduction in the number of CT scans.

Systematic review and meta-analysis of duplex ultrasonography, contrast-enhanced ultrasonography or computed tomography for surveillance after endovascular aneurysm repair

BACKGROUND

Previous analyses suggested that duplex ultrasonography (DUS) detected endoleaks after endovascular aneurysm repair (EVAR) with insufficient sensitivity; they did not specifically examine types 1 and 3 endoleak, which, if untreated, may lead to aneurysm-related death. In light of changes to clinical practice, the diagnostic accuracy of DUS and contrast-enhanced ultrasonography (CEUS) for types 1 and 3 endoleak required focused reappraisal.

METHODS

Studies comparing DUS or CEUS with computed tomography (CT) for endoleak detection were identified. CT was taken as the standard in bivariable meta-analysis.

RESULTS

Twenty-five studies (3975 paired scans) compared DUS with CT for all endoleaks. The pooled sensitivity was 0·74 (95 per cent confidence interval 0·62 to 0·83) and the pooled specificity was 0·94 (0·90 to 0·97). Thirteen studies (2650 paired scans) reported detection of types 1 and 3 endoleak by DUS; the pooled sensitivity of DUS was 0·83 (0·40 to 0·97) and the pooled specificity was 1·00 (0·97 to 1·00). Eleven studies (961 paired scans) compared CEUS with CT for all endoleaks. The pooled sensitivity of CEUS was 0·96 (0·85 to 0·99) and the pooled specificity was 0·85 (0·76 to 0·92). Eight studies (887 paired scans) reported detection of types 1 and 3 endoleak by CEUS. The pooled sensitivity of CEUS was 0·99 (0·25 to 1·00) and the pooled specificity was 1·00 (0·98 to 1·00).

CONCLUSION

Both CEUS and DUS were specific for detection of types 1 and 3 endoleak. Estimates of their sensitivity were uncertain but there was no evidence of a clinically important difference. DUS detects types 1 and 3 endoleak with sufficient accuracy for surveillance after EVAR.

Thoracic and abdominal aortic diameter measurement by MRI using plain axial volumetric interpolated breath-hold examination in epidemiologic research: a validation study

RATIONALE AND OBJECTIVES

This study evaluates the validity and reliability of measuring the diameters of the thoracic and abdominal aorta from plain volumetric interpolated breath-hold examination (VIBE) images.

MATERIALS AND METHODS

The study included 50 male subjects from the population-based Study of Health in Pomerania. They underwent imaging of the thoracic and abdominal aorta at 1.5 Tesla using a contrast-enhanced magnetic resonance angiography (CE-MRA) and plain VIBE sequence. Diameters were measured at five predefined anatomic sites from reformatted orthogonal CE-MRA images and axial plain VIBE images. The measurements were validated using Pearson correlation and Bland-Altman analysis. The Bland-Altman method was also used to assess reliability.

RESULTS

Comparison of the diameters measured from CE-MRA and VIBE images revealed strong correlation for the ascending, descending, suprarenal, and infrarenal aorta with r = 0.95 (P < .0001), r = 0.88 (P < .0001), 0.92 (P < .0001), and 0.87 (P < .0001), respectively. Measurement for the aortic arch was moderately correlated with r = 0.78 (P < .0001). Mean bias did not exceed 0.1 cm (6%). The 95% limits of agreement (LOA) were less than 0.5 cm (15%). Intra- and interobserver agreement showed a mean bias of less than 2%; the 95% LOA were less than 11%.

CONCLUSIONS

Axial measurement of the diameters of the thoracic and abdominal aorta using a plain axial VIBE sequence is highly valid and reliable, making it suitable for use in epidemiologic research.

Imaging Surveillance following Endovascular Aneurysm Repair

Endoleaks are unique complications of endovascular aneurysm repair (EVAR) that necessitate lifelong imaging surveillance for the patient. Several imaging modalities may be used to monitor the patient for endoleaks and other complications related to the stent graft. At present, computed tomographic angiography remains the gold standard for the detection of endoleaks. Other modalities that can be used to detect endoleaks include magnetic resonance, ultrasonography, nuclear medicine techniques, and pressure monitoring. In addition, follow-up imaging with digital subtraction angiography is important for endoleak classification and to guide decisions regarding therapy. In this article, we review the classification of endoleaks and discuss the different imaging strategies available for post-EVAR surveillance.

Duplex ultrasound evaluation of endoluminally treated aortic aneurysms with emphasis on diameter measurement: A comparison with computed tomography

PURPOSE

The aim of this study was to determine the accuracy of color Doppler ultrasound (CDUS) for endoleak detection and measurement of the aneurysm diameter after endovascular aortic aneurysm repair.

METHODS

Forty-eight CDUS and computed tomographic angiography (CTA) examinations performed concurrently on 29 patients who were treated with endovascular stent grafts for abdominal aortic aneurysms were included in the study. CTA and CDUS findings were retrospectively compared for aneurysm diameter, patency of the graft, and the presence of leaks in the aneurysm's lumen (the so-called "endoleaks").

RESULTS

The stent graft was patent in all patients. Including the follow-up examinations, endoleaks were detected in a total of 17 CTA studies. The sensitivity, specificity, and positive and negative predictive values for CDUS compared with CTA as the gold standard were 100%, 96%, 94.4%, and 100%, respectively. Kappa statistics showed a high level of agreement between CDUS ant CTA examinations (χ = 0.95). The aneurysm diameters measured with CDUS and CTA were significantly different, but within 5 mm of each other in 83% of patients.

CONCLUSIONS

Provided that a strict CDUS protocol including spectral analysis of perigraft flow is used, CDUS is comparable to CTA for endoleak detection and measurement of the aneurysm diameter.

Sonographic Evaluation of Aortic Endografts

The selective use of endovascular devices to repair abdominal aortic aneurysms was introduced in the early 1990s. Although placement of an aortic endograft offers patients a less morbid alternative to surgical repair, this procedure is not without complications. Persistent perfusion of the residual aneurysmal sac via endoleaks may place the patient at risk for aneurysmal enlargement and subsequent rupture. Historically, serial computed tomographic angiography has been used as the primary modality for assessment of aortic endografts. In recent years, sonography has been shown to provide a valued tool for ongoing surveillance of aortic endografts and identification of endoleaks, increasing aneurysmal size, hemodynamic disorders, and graft migration and/or kinking. Standardization of the sonographic evaluation yields accurate information vital to the long-term patency of these conduits.

Endovascular stent graft repair of abdominal aortic aneurysms: Current status and future directions

Endovascular stent graft repair of abdominal aortic aneurysm (AAA) has undergone rapid developments since it was introduced in the early 1990s. Two main types of aortic stent grafts have been developed and are currently being used in clinical practice to deal with patients with complicated or unsuitable aneurysm necks, namely, suprarenal and fenestrated stent grafts. Helical computed tomography angiography has been widely recognized as the method of choice for both pre-operative planning and post-operative follow-up of endovascular repair (EVAR). In addition to 2D axial images, a number of 2D and 3D reconstructions are generated to provide additional information about imaging of the stent grafts in relation to the aortic aneurysm diameter and extent, encroachment of stent wires to the renal artery ostium and position of the fenestrated vessel stents. The purpose of this article is to provide an overview of applications of EVAR of AAA and diagnostic applications of 2D and 3D image visualizations in the assessment of treatment outcomes of EVAR. Interference of stent wires with renal blood flow from the hemodynamic point of view will also be discussed, and future directions explored.

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.