Duplex ultrasound imaging alone is sufficient for midterm endovascular aneurysm repair surveillance: A cost analysis study and prospective comparison with computed tomography scan

Ultrasound Surveillance is Feasible After Endovascular Aneurysm Repair

BACKGROUND

Surveillance after endovascular aneurysm repair (EVAR) is traditionally done with computed tomography angiography (CTA) scans that exposes patient to radiation, nephrotoxic contrast media, and potentially increased risk for cancer. Ultrasound (US) is less labor intensive and expensive and might thus provide a good alternative for CTA surveillance. The aim of this study was to evaluate in real-life patient cohorts whether US is able to detect post-EVAR aneurysm-related complications similarly to CTA.

METHODS

This retrospective study compared the outcome of consecutive patients who underwent EVAR for intact abdominal aortic aneurysm and were surveilled solely by CTA (CTA-only cohort, n = 168) in 2000-2010 or by combined CTA and US (CTA/US cohort, n = 300) in 2011-2016, as a standard surveillance protocol in the department of vascular surgery, Helsinki University Hospital. The CTA-only patients were imaged at 1, 3, and 12 months and annually thereafter. The CTA/US patients were imaged with CTA at 3 and 12 months, US at 6 months and annually thereafter. If there were suspicion of >5 mm aneurysm growth, CTA scan was performed. The patients were reviewed for imaging data, reinterventions, aneurysm ruptures, and death until December 2018. The 2 groups were compared for secondary rupture, aneurysm-related and cancer-related death, reintervention related to abdominal aortic aneurysm, and maximum aneurysm diameter increase ≥5 mm. The mean follow-up in the CTA-only cohort was 67 months and in CTA/US cohort 43 months.

RESULTS

The 2 cohorts were alike for basic characteristics and for the mean aneurysm diameter. The total number of CT scans for detecting aneurysm was 84.1/100 patient years in the CTA-only cohort compared to 74.5/100 patient years for US/CTA cohort. Forty percent of patients under combined CTA/US surveillance received 1 or more additional CTA scans. The 2 cohorts did not differ for 1-year, 5-year and 8-year freedom from aneurysm related death, secondary sac rupture, nor the incidence of rupture preventing interventions.

CONCLUSIONS

Based on the follow-up data of this real-life cohort of 468 patients, combined surveillance with US and additional CTA either per protocol or due to suspicion of aneurysm-related complications had comparable outcome with sole CTA-surveillance. Thus, US can be considered a reasonable alternative for the CTA. However, our study showed also that the need of additional CTAs due to suspicion of endoleak or aneurysm nonrelated reasons is substantial.

Safety of Utilizing Ultrasound as the Sole Modality of Follow-Up after Endovascular Aneurysm Repair

BACKGROUND

Post endovascular aneurysm repair (EVAR), surveillance with computed tomography-aortography (CTA) remains the most common practice, per Society for Vascular Surgery (SVS) guidelines. Chronic exposure to both radiation and intravenous (IV) contrast has raised concerns about long-term CTA follow-up (FU). As we have selectively used ultrasound (US) as a sole modality for post-EVAR surveillance, we sought to review our outcomes in this subset of patients.

METHODS

Retrospective review of our institution's vascular database identified 213 EVAR patients from 2013 to 2021. Fenestrated-EVAR and snorkel reconstructions were excluded. Patient demographics/outcomes, abdominal aortic aneurysm (AAA) characteristics, and FU modalities and outcomes were analyzed. Unpaired Student's t-test, ANOVA, and chi-squared test were used to assess group differences.

RESULTS

Eighty-five of the 213 EVAR patients (39.9%) were lost to FU within 3 months. Among the 128 remaining patients, 91 underwent FU using initial US, while 37 patients underwent post-EVAR FU initially using CTA. There were no significant differences (P > 0.05) between patient age (75.5 ± 9.4 vs. 75.3 ± 8.5), body mass index (BMI) (27.7 ± 5.4 vs. 28.9 ± 7.4), or mean AAA size (5.6 ± 1.1 vs. 5.9 ± 1.2) in US-surveilled and computed tomography (CT)-surveilled groups, respectively. Of the 91 patients, initially surveilled with US, 15 patients demonstrated endoleak and/or AAA growth (>5 mm). The 15 patients with US-demonstrated endoleak and/or growth underwent confirmatory CTA, with 3 patients eventually requiring EVAR revision. Among 37 patients initially surveilled with CT, 10 demonstrated significant growth and 2 patients eventually required EVAR revision. There were no patients with AAA rupture during post-EVAR surveillance. FU data were analyzed among a select lower-risk group of patients (preoperative AAA diameter ≤5.5 cm, BMI ≤30, and no endoleak at completion of EVAR). Among this group, there were no surveilled patients who required EVAR reintervention, regardless of surveillance modality (US n = 32; CT n = 4). The average FU was 29.5 ± 26.4 months in the US group and 26.4 ± 22.3 months in the CT group (P > 0.05).

CONCLUSIONS

Although initial CT surveillance following EVAR remains ideal, in select lower-risk patients, US is a viable alternative even for the initial post-procedure study. Advantages include decreased radiation exposure and cost. Our data suggest that US is a safe sole modality for surveillance following EVAR in selective patients.

Imaging modalities for endoleak surveillance

As the global population ages, the issue of abdominal aortic aneurysm continues to grow. With the evolution of new devices and refined operative technique, aneurysm treatment via endovascular aortic repair is becoming increasingly favourable. This, however, is not without drawbacks, where regular surveillance is paramount to long-term success and detection of post-procedure complications. Of these complications, endoleak is the most notable and poses the greatest risk of potential future aortic rupture. The purpose of this review paper is to discuss the armada of imaging modalities used in the detection and evaluation of endoleak and their varying usefulness. Plain abdominal X-ray is a cost-effective tool in detecting gross graft abnormalities such as stent migration or deformity (kinking or fracture). Though it may raise suspicion for endoleak, X-ray does not allow accurate classification of endoleak type when used alone. Duplex ultrasonography quantifies both aortic anatomy and real time flow dynamics. Most screening programmes are conducted using two-dimensional ultrasound. Unfortunately, observer and equipment variability may lead to surveillance discrepancies-but reduced when utilising a dedicated vascular sonography laboratory. Contrast enhanced ultrasonography is a promising alternative to computed tomography, though still is emerging. Computed tomography angiography certainly has disadvantages (ionising radiation, contrast-nephropathy, limited differentiation of endoleak type)-however, it provides near-real surgical dimensions and highlights graft complications and concomitant disease (such as neighbouring infection). With widespread availability and short scan time, it certainly remains valuable in surveillance. Magnetic resonance angiography has a similar sensitivity to computed tomography (minus the radiation), however is plagued by movement and metal artefact. Other novel modalities in endoleak surveillance include four-dimensional ultrasound, multiplanar intra-operative probes, nuclear medicine and wall stress analysis.

Simple diameter measurements with ultrasound can be safely used to follow the majority of patients after infrarenal endovascular aneurysm repair

BACKGROUND

The optimal imaging follow-up after infrarenal EVAR is still undefined. The objective was to study the outcome of a personalized follow-up program after infrarenal EVAR based on ultrasound AAA diameter measurements for low-risk patients.

METHODS

All consecutive patients followed-up locally after elective and acute infrarenal EVAR between 2010 and 2015 were retrospectively reviewed. Patients underwent CTA at 1 month post-EVAR whereby the attending surgeon defined the subsequent follow-up. Patients considered at low risk were followed with ultrasound only assessing AAA diameter at 1, 2, 3 and every 5 years postoperatively (group A). Low-risk required a favourable preoperative anatomy especially regarding the aneurysm neck, satisfactory intraoperative result and uneventful 1 month CTA (type 2 endoleaks acceptable). Patients not fulfilling the criteria for group A were followed with yearly 3-phase-CTAs (group B).

RESULTS

222 patients with a AAA median diameter of 58 (54-68) mm were included. 191 were allocated into group A and 31 in group B. Median follow-up time was 36 (24-59) months. Five year primary and primary assisted success was 82 ± 5 % and 93 ± 3 % for group A and 70 ± 13% and 93 ± 5% for group B, respectively (P= 0.042 and P= 0.504, respectively). 16 late aneurysm-related re-interventions were performed in 12 patients (7 in group A and 9 in group B). In group A, 5 re-interventions were rupture-preventing and 2 were symptomatic. All late re-interventions in group B were performed following findings on follow-up imaging. Five-year late re-intervention-free survival was 95 ± 2 % and 84 ± 7 % for groups A and B, respectively (P=0.046). Five-year survival was 80 ± 3 % and 63 ± 10 % for group A and B, respectively (P= 0.024).

CONCLUSIONS

A customized follow-up program after infrarenal EVAR based on ultrasound AAA diameter measurements in low-risk patients seems to be effective in maintaining a very high mid-term clinical success rate.

Editor's Choice - A Comparison of Computed Tomography Angiography and Colour Duplex Ultrasound Surveillance Post Infrarenal Endovascular Aortic Aneurysm Repair: Financial Implications and Impact of Different International Surveillance Guidelines

OBJECTIVE

Use of colour duplex ultrasound (CDUS) and computed tomography angiography (CTA) for infrarenal endovascular aortic aneurysm repair (EVAR) surveillance differs in internationally published guidelines. This study aimed firstly to compare CDUS detection of significant sac abnormalities with CTA. Secondly, a sensitivity analysis was conducted to compare financial estimates of the, predominantly CDUS based, local and Society of Vascular Surgery (SVS) protocols, the risk stratified European Society of Vascular Surgery (ESVS) protocol, and the CTA based National Institute of Health and Care Excellence (NICE) protocol.

METHODS

Agreement between CDUS and CTA was assessed for detection of significant sac abnormalities. Surveillance protocols were extrapolated from published guidelines and applied to infrarenal EVAR patients active on local surveillance at a large, single centre. Surveillance intensity was dependent on presence of endoleak and subsequent risk of treatment failure in accordance with surveillance recommendations. Estimates for each surveillance protocol were inclusive of a range of published incidences of endoleak, contrast associated acute kidney injury (AKI), and excess hospital bed days, and estimated for a hypothetical five year surveillance period.

RESULTS

The kappa coefficient between CDUS and CTA for detecting sac abnormalities was 0.68. Maximum five year surveillance cost estimates for the 289 active EVAR patients were £272 359 for SVS, £230 708 for ESVS, £643 802 for NICE, and £266 777 for local protocols, or £1 270, £1 076, £3 003, and £1 244 per patient. Differences in endoleak incidence accounted for a 1.1 to 1.4 fold increase in costs. AKI incidence accounted for a 3.3 to 6.2 fold increase in costs.

CONCLUSION

A combined CTA and CDUS EVAR surveillance protocol, with CTA reserved for early seal assessment and confirmatory purposes, provides an economical approach without compromising detection of sac abnormalities. AKI, as opposed to direct imaging costs, accounted for the largest differences in surveillance cost estimates.

Duplex Ultrasound Can Successfully Identify Endoleaks and Renovisceral Stent Patency in Patients Undergoing Complex Endovascular Aneurysm Repair

Efficacy of duplex ultrasound (DU) surveillance of complex EVAR such as FEVAR and ChEVAR has not been studied. All patients undergoing FEVAR or ChEVAR at a single multihospital institution were retrospectively reviewed. Postoperative surveillance included DU at 1 month and CTA at 3 months. 82 patients met inclusion criteria including 39 (47.6%) ChEVAR and 43 (52.4%) FEVAR cases. DU identified endoleak with aneurysm sac enlargement in 3 cases requiring reintervention. CTA at 3 months detected 2 new endoleaks without growth and 1 renal artery stent occlusion. Replacement of initial postoperative imaging with DU did not result in any missed endoleaks, deaths, ruptures, or branch occlusions.

Color Doppler ultrasound for surveillance following EVAR as the primary tool

OBJECTIVE

As aneurysm-related events and rupture is not eliminated, postoperative lifelong surveillance is mandatory after endovascular aneurysm repair (EVAR). For surveillance colored Doppler ultrasound (CDUS) is a standard method of noninvasive evaluation having the advantages of availability, cost-effectiveness, and lack of nephrotoxicity and radiation. We evaluated CDUS for primary surveillance tool after elective EVAR by comparing with computerized tomography.

METHODS

Between January 2018 and March 2020, 84 consecutive post-EVAR patients were evaluated. First, CDUS was performed by two Doppler operators from the Radiology Department and then computed tomographic angiography (CTA) was performed. The operators were blind to CTA reports. A reporting protocol was organized for endoleak detection and largest aneurysm diameter.

RESULTS

Among 84 patients, there were 11 detected endoleaks (13.1%) with CTA and seven of them was detected with CDUS (r = .884, p < .001). All Type I and III endoleaks were detected perfectly. There is an insufficiency in detecting low flow by CDUS. Eliminating this frailty, there was a strong correlation of aneurysm sac diameter measurement between CTA and CDUS (r = .777, p < .001). The sensitivity and specificity of CDUS was 63.6% and 100%, respectively. The accuracy was 95.2%. Positive and negative predictive values were 100% and 94.8%. Bland-Altman analysis and linear regression analysis showed no proportional bias (mean difference of 1.5 ± 2.2 mm, p = .233).

CONCLUSIONS

For surveillance, CDUS promises accurate results without missing any potential complication requiring intervention as Type I or III endoleak. Lack of detecting Type II endoleaks may be negligible as sac enlargement was the key for reintervention in this situation and CDUS has a remarkably high correlation with CTA in sac diameter measurement. CDUS may be a primary surveillance tool for EVAR and CTA will be reserved in case of aneurysm sac enlargement, detection of an endoleak, inadequate CDUS, or in case of unexplained abdominal symptomatology. By this way we not only avoid ionizing radiation and nephrotoxic agents, but also achieve cost saving issue also.

Computed Tomography-Aortography Versus Color-Duplex Ultrasound for Surveillance of Endovascular Abdominal Aortic Aneurysm Repair

Background

Color-duplex ultrasonography (DUS) could be an alternative to computed tomography-aortography (CTA) in the lifelong surveillance of patients after endovascular aneurysm repair (EVAR), but there is currently no level 1 evidence. The aim of this study was to assess the diagnostic accuracy of DUS as an alternative to CTA for the follow-up of post-EVAR patients.

Methods

Between December 16, 2010, and June 12, 2015, we conducted a prospective, blinded, diagnostic-accuracy study, in 15 French university hospitals where EVAR was commonly performed. Participants were followed up using both DUS and CTA in a mutually blinded setup until the end of the study or until any major aneurysm-related morphological abnormality requiring reintervention or an amendment to the follow-up policy was revealed by CTA. Database was locked on October 2, 2017. Our main outcome measures were sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratios of DUS against reference standard CTA. CIs are binomial 95% CI.

Results

This study recruited prospectively 659 post-EVAR patients of whom 539 (82%) were eligible for further analysis. Following the baseline inclusion visit, 940 additional follow-up visits were performed in the 539 patients. Major aneurysm-related morphological abnormalities were revealed by CTA in 103 patients (17.2/100 person-years [95% CI, 13.9–20.5]). DUS accurately identified 40 patients where a major aneurysm-related morphological abnormality was present (sensitivity, 39% [95% CI, 29–48]) and 403 of 436 patients with negative CTA (specificity, 92% [95% CI, 90–95]). The negative predictive value and positive predictive value of DUS were 92% (95% CI, 90–95) and 39% (95% CI, 27–50), respectively. The positive likelihood ratio was 4.87 (95% CI, 2.9–9.6). DUS sensitivity reached 73% (95% CI, 51–96) in patients requiring an effective reintervention.

Conclusions

DUS had an overall low sensitivity in the follow-up of patients after EVAR, but its performance improved meaningfully when the subset of patients requiring effective reinterventions was considered.

Registration

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01230203.

Velocities of type II endoleaks on Doppler ultrasonography predict outcome

OBJECTIVE

We sought to determine whether flow velocities measured using Doppler ultrasonography after endovascular aortic aneurysm repair (EVAR) can predict for resolution of type II endoleaks without intervention. We also assessed the relationship of the flow velocities to sac growth and the need for intervention. We hypothesized that hemodynamic properties suggesting low flow velocity would predict for resolution of type II endoleaks.

METHODS

The data from 23 patients with type II endoleaks identified on Doppler ultrasonography after EVAR from January 2014 to December 2017 were retrospectively analyzed. The 23 patients with type II endoleaks were split into two groups. Group 1 included the 13 patients with resolved endoleaks or shrinking sac size and group 2, the 10 patients with an increasing sac size or those requiring intervention to seal the endoleak because of an increased sac size. We analyzed the velocities of the endoleak nidus.

RESULTS

Doppler ultrasound velocities were significantly lower in patients with resolved type II endoleaks and those with a shrinking aneurysm sac size compared with those demonstrating an increase in aneurysm sac size (42.6 ± 25.2 cm/s vs 219.5 ± 84.1 cm/s; P < .0001). Of the 10 patients in group 2, nine had required intervention with either translumbar embolization or transarterial embolization, with only two experiencing complete resolution of the type II endoleak, despite the intervention. All patients in group 2 had had ≥1 duplex ultrasound scan with endoleak nidus velocities >100 cm/s. In contrast, no patient in group 1 had had any duplex ultrasound scan with endoleak nidus velocities >100 cm/s.

CONCLUSIONS

The Doppler ultrasound velocities of type II endoleaks might be able to predict for spontaneous resolution of type II endoleaks or increased sac growth. Type II endoleaks on Doppler ultrasonography with endoleak nidus velocities >100 cm/s can persistent, even with attempted treatment.

Contrast-enhanced ultrasound and/or colour duplex ultrasound for surveillance after endovascular abdominal aortic aneurysm repair: a systematic review and economic evaluation

BACKGROUND

Endovascular abdominal aortic aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA) is less invasive than open surgery, but may be associated with important complications. Patients receiving EVAR require long-term surveillance to detect abnormalities and direct treatments. Computed tomography angiography (CTA) has been the most common imaging modality adopted for EVAR surveillance, but it is associated with repeated radiation exposure and the risk of contrast-related nephropathy. Colour duplex ultrasound (CDU) and, more recently, contrast-enhanced ultrasound (CEU) have been suggested as possible, safer, alternatives to CTA.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of imaging strategies, using either CDU or CEU alone or in conjunction with plain radiography, compared with CTA for EVAR surveillance.

DATA SOURCES

Major electronic databases were searched, including MEDLINE, EMBASE, Science Citation Index, Scopus' Articles-in-Press, Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE) and NHS Economic Evaluation Database from 1996 onwards. We also searched for relevant ongoing studies and conference proceedings. The final searches were undertaken in September 2016.

METHODS

We conducted a systematic review of randomised controlled trials and cohort studies of patients with AAAs who were receiving surveillance using CTA, CDU and CEU with or without plain radiography. Three reviewers were involved in the study selection, data extraction and risk-of-bias assessment. We developed a Markov model based on five surveillance strategies: (1) annual CTA; (2) annual CDU; (3) annual CEU; (4) CDU together with CTA at 1 year, followed by CDU on an annual basis; and (5) CEU together with CTA at 1 year, followed by CEU on an annual basis. All of these strategies also considered plain radiography on an annual basis.

RESULTS

We identified two non-randomised comparative studies and 25 cohort studies of interventions, and nine systematic reviews of diagnostic accuracy. Overall, the proportion of patients who required reintervention ranged from 1.1% (mean follow-up of 24 months) to 23.8% (mean follow-up of 32 months). Reintervention was mainly required for patients with thrombosis and types I-III endoleaks. All-cause mortality ranged from 2.7% (mean follow-up of 24 months) to 42% (mean follow-up of 54.8 months). Aneurysm-related mortality occurred in < 1% of the participants. Strategies based on early and mid-term CTA and/or CDU and long-term CDU surveillance were broadly comparable with those based on a combination of CTA and CDU throughout the follow-up period in terms of clinical complications, reinterventions and mortality. The economic evaluation showed that a CDU-based strategy generated lower expected costs and higher quality-adjusted life-year (QALYs) than a CTA-based strategy and has a 63% probability of being cost-effective at a £30,000 willingness-to-pay-per-QALY threshold. A CEU-based strategy generated more QALYs, but at higher costs, and became cost-effective only for high-risk patient groups.

LIMITATIONS

Most studies were rated as being at a high or moderate risk of bias. No studies compared CDU with CEU. Substantial clinical heterogeneity precluded a formal synthesis of results. The economic model was hindered by a lack of suitable data.

CONCLUSIONS

Current surveillance practice is very heterogeneous. CDU may be a safe and cost-effective alternative to CTA, with CTA being reserved for abnormal/inconclusive CDU cases.

FUTURE WORK

Research is needed to validate the safety of modified, more-targeted surveillance protocols based on the use of CDU and CEU. The role of radiography for surveillance after EVAR requires clarification.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016036475.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Duplex scanning as an alternative to computer tomography with contrast enhancement for the control of complications after endovascular aneurysm repair

EVAR (endovascular aneurism repair) is the preferred method for the surgical treatment of ananeurysm. The advantage of this type of surgical intervention is that a smaller number of postoperative complications will occur. The main diagnostic tasks for patients after EVAR are to determine the size of the aneurysmal sac, detection of an endoleak, detection of the endoprosthesis migration and the deformation of the stent graft itself. Conclusion: early detection of complications in the postoperative period remains the main problem for monitoring patients after EVAR. Duplex scanning is a safe, non-invasive and effective method of measuring the size of an aneurysmal sac and detecting possible complications after EVAR.

Patient satisfaction and chronic illness are predictors of postendovascular aneurysm repair surveillance compliance

OBJECTIVE

Although lifelong surveillance is recommended by the Society for Vascular Surgery for patients undergoing endovascular aneurysm repair (EVAR) reported that compliance with long-term follow-up has been poor. We sought to identify factors that predict compliance with EVAR surveillance through analysis of patient variables and post-EVAR questionnaire results.

METHODS

We analyzed 28 patient variables gathered from our computerized registry, patient charts, and phone questionnaires of patients who underwent EVAR between January 1, 2010, and December 31, 2014. These factors included patient demographics, education, postoperative complications, satisfaction with vascular surgery care, transportation mode, distance to our medical center, and living situation. Compliance was defined as a patient who underwent the most recent recommended follow-up surveillance study within the prescribed timeframe. Post-EVAR surveillance protocol consisted of office evaluation and duplex ultrasound examination performed in our accredited noninvasive vascular laboratory at 1 week, 6 months, then annually. Computed tomography angiography was obtained only if duplex ultrasound examination suggested endoleak, sac enlargement of more than 5 mm, or a failing limb.

RESULTS

Of 144 patients who underwent EVAR during this time period, 89 patients (62%) were compliant with the most recent recommended follow-up study. One hundred two patients completed the questionnaire or their families did if patients died or were incapacitated. Of those, 80 were compliant with follow-up and 22 were not. Based on the questionnaires of these 102 patients, estimated compliance at 3 years after EVAR was 69.6 ± 6.0% based on Kaplan-Meier analysis. In the compliant vs noncompliant groups, the estimated 3-year survival rate was 93.2 ± 3.4% vs 52.4 ± 12.7%, respectively (P < .001), and the estimated 5-year survival rate was 83.1 ± 6.4% vs 34.4 ± 13.4%, respectively (P < .001), respectively. However, none of the mortalities observed in the noncompliant group were aneurysm related. Adverse neurologic events after EVAR demonstrated a trend predicting noncompliance after 5 years based on multivariate Cox regression analysis (hazard ratio [HR], 2.57; 95% confidence interval [CI], 0.95-6.90; P = .062). Patient dissatisfaction with their vascular surgeon and hospital care predicted noncompliance with recommended postoperative surveillance (HR, 5.0; 95% CI, 1.52-16.7; P = .008). College education or higher was associated with compliance (HR, 0.28; 95% CI, 0.06-1.23; P = .092). No other variables, including postoperative complications or distance from the hospital, predicted follow-up noncompliance.

CONCLUSIONS

Patient satisfaction with their vascular surgeon and hospital experience predicted compliance with post-EVAR surveillance regardless of postoperative complications. Noncompliant patients had decreased survival, but mortality and surveillance noncompliance were likely due to disabling chronic disease.

Late type II endoleaks after endovascular aneurysm repair require intervention more frequently than early type II endoleaks

OBJECTIVE

Type II endoleaks (T2ELs) are commonly observed after endovascular aneurysm repair (EVAR). We sought to determine whether time at onset of T2ELs correlated with the need to intervene based on sac expansion or rupture.

METHODS

Between 1998 and 2015, 462 EVARs performed at our institution had duplex ultrasound surveillance in our accredited noninvasive vascular laboratory. Computed tomography and arteriography were reserved for abnormal duplex ultrasound findings. The need for intervention for T2ELs was classified according to time at onset after EVAR. Interventions for T2ELs were performed only for sac expansion >5 mm or rupture. We defined early-onset T2ELs as <1 year after EVAR and delayed or late onset as >1 year of follow-up.

RESULTS

Of the 462 EVARs, 96 patients (21%) developed T2ELs after implantation. Of these, 65 (68%) had early and 31 (32%) had late onset (mean, 12 months; range, 1-112 months). Early T2ELs resolved without treatment in 75% (49/65) of cases compared with only 29% (9/31) of late T2ELs (P < .0001). Intervention was required for only 8% (5/65) of patients with early T2ELs (5 sac expansions, 0 ruptures) compared with 55% (17/31) for late T2ELs (16 sac expansions, 1 rupture; P < .0001). The remaining patients were observed for persistent T2ELs with no sac growth (17% [11/65] early vs 16% [5/31] late; P = .922).

CONCLUSIONS

Less than one-third (29%) of T2ELs that develop after 1 year will resolve spontaneously and about half (55%) will require intervention for sac growth or rupture. T2ELs that develop >1 year after EVAR should be followed up with a more frequent surveillance protocol and perhaps with a lower threshold to intervene.

Abdominal aortic aneurysms: pre- and post-procedural imaging

Abdominal aortic aneurysm (AAA) is a relatively common, potentially life-threatening disorder. Rupture of AAA is potentially catastrophic with high mortality. Intervention for AAA is indicated when the aneurysm reaches 5.0-5.5 cm or more, when symptomatic, or when increasing in size > 10 mm/year. AAA can be accurately assessed by cross-sectional imaging including computed tomography angiography and magnetic resonance angiography. Current options for intervention in AAA patients include open surgery and endovascular aneurysm repair (EVAR), with EVAR becoming more prevalent over time. Cross-sectional imaging plays a crucial role in AAA surveillance, pre-procedural assessment, and post-EVAR management. This paper will discuss the current role of imaging in the assessment of AAA patients prior to intervention, in evaluation of procedural complications, and in long-term follow-up of EVAR patients.

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.

Direct sac puncture versus transarterial embolization of type II endoleaks: An evaluation and comparison of outcomes

Purpose To determine the outcomes of type II endoleak embolization with aneurysm sac obliteration and whether the approach - direct sac puncture or transarterial - affects outcome. Methods A retrospective review of patients who underwent endovascular aneurysm repairs and subsequent type II endoleak embolization over 10 years was performed. Twenty-three patients (median age: 73 years, range: 40-88 years) underwent 35 embolizations. Embolization was performed with the goal of obliterating both the endoleak sac and feeding vessels. Embolization agents used include cyanoacrylate glue only (48%), glue and coils (36%), coils only (13%), and other (3%). Results Mean follow-up was 21.8 months. Patients underwent an average of 1.5 embolizations, with 35% requiring more than one. Technical success rate was 89%. Freedom from aneurysm sac expansion was achieved in 91%. Freedom from type II endoleak was accomplished in 70%. There were no ruptured aneurysms during the follow-up period. Direct sac puncture and transarterial approaches had similar incidences of aneurysm sac growth ( p = 0.74), persistent type II endoleak ( p = 0.32), and complications ( p = 0.64). However, direct sac puncture had significantly shorter fluoroscopy ( p < 0.001) and total procedure times ( p < 0.001) than transarterial embolizations. Conclusion Direct sac puncture and transarterial embolization of type II endoleak with aneurysm sac obliteration are similarly effective for the prevention of aneurysm sac growth. However, direct sac puncture is our preferred approach given its significantly shorter fluoroscopic and procedural times.

Contemporary Applications of Ultrasound in Abdominal Aortic Aneurysm Management

Ultrasound (US) is a well-established screening tool for detection of abdominal aortic aneurysms (AAAs) and is currently recommended not only for those with a relevant family history but also for all men and high-risk women older than 65 years of age. The advent of minimally invasive endovascular techniques in the treatment of AAAs [endovascular aneurysm repair (EVAR)] has increased the need for repeat imaging, especially in the postoperative period. Nevertheless, preoperative planning, intraoperative execution, and postoperative surveillance all mandate accurate imaging. While computed tomographic angiography and angiography have dominated the field, repeatedly exposing patients to the deleterious effects of cumulative radiation and intravenous nephrotoxic contrast, US technology has significantly evolved over the past decade. In addition to standard color duplex US, 2D, 3D, or 4D contrast-enhanced US modalities are revolutionizing AAA management and postoperative surveillance. This technology can accurately measure AAA diameter and volume, and most importantly, it can detect endoleaks post-EVAR with high sensitivity and specificity. 4D contrast-enhanced US can even provide hemodynamic information about the branch vessels following fenestrated EVARs. The need for experienced US operators and accredited vascular labs is mandatory to guarantee the reliability of the results. This review article presents a comprehensive overview of the literature on the state-of-art US imaging in AAA management, including post-EVAR follow-up, techniques, and diagnostic accuracy.

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.

Endovascular Repair of Abdominal Aortic Aneurysm: Follow-up with Noninvasive Vascular Elastography in a Canine Model

PURPOSE

To assess the ability of noninvasive vascular elastography (NIVE) to help characterize endoleaks and thrombus organization in a canine model of abdominal aortic aneurysm after endovascular aneurysm repair with stent-grafts, in comparison with computed tomography (CT) and pathologic examination findings.

MATERIALS AND METHODS

All protocols were approved by the Animal Care Committee in accordance with the guidelines of the Canadian Council of Animal Care. Stent-grafts were implanted in a group of 18 dogs with aneurysms created in the abdominal aorta. Type I endoleak was created in four aneurysms; type II endoleak, in 13 aneurysms; and no endoleak, in one aneurysm. Doppler ultrasonography and NIVE examinations were performed at baseline and at 1-week, 1-month, 3-month, and 6-month follow-up. Angiography, CT, and macroscopic tissue examination were performed at sacrifice. Strain values were computed by using the Lagrangian speckle model estimator. Areas of endoleak, solid organized thrombus, and fresh thrombus were identified and segmented by comparing the results of CT and macroscopic tissue examination. Strain values were compared by using the Wilcoxon rank-sum and Kruskal-Wallis tests.

RESULTS

All stent-grafts were successfully deployed, and endoleaks were clearly depicted in the last follow-up elastography examinations. Maximal axial strains over consecutive heart cycles in endoleak, organized thrombus, and fresh thrombus areas were 0.78% ± 0.22, 0.23% ± 0.02, 0.10% ± 0.04, respectively. Strain values were significantly different between endoleak and organized or fresh thrombus areas (P < .000) and between organized and fresh thrombus areas (P < .0002). No correlation was found between strain values and type of endoleak, sac pressure, endoleak size, and aneurysm size.

CONCLUSION

NIVE may be able to help characterize endoleak and thrombus organization, regardless of the size, pressure, and type of endoleak.

Ultrasonographic Surveillance of Abdominal Aortic Endovascular Aneurysm Stent Graft Repair in a Dedicated Vascular Laboratory

Surveillance following abdominal aortic endovascular aneurysm repair (EVAR) is imperative to confirm graft patency, analyze residual sac size (RSS), and evaluate for complications. This retrospective study evaluated ultrasonographic (US) surveillance after EVAR compared to computed tomography (CT). US was done by 1 of 11 experienced registered technologists. US was ordered for surveillance more frequently than CT, with a ratio of 4:1. Compared to CT, US endoleak evaluations were 74% sensitive and 76% specific with a 63% positive predictive value and 84% negative predictive value. However, 11 CT scans were likely false negatives, and 1 CT was a false positive. For true positives that stated endoleak type, there was a 93% agreement between the type on US and CT. US had a 75% accuracy for RSS (95% CI, −1.02 to 1.16). These data support the use of US along with clinical symptoms as a first-line surveillance program after EVAR and are widely applicable to the majority of vascular laboratories that employ multiple registered vascular technologists. The adaptation of increased US surveillance would decrease the number of CT scans, thereby significantly reducing cost and radiation/contrast exposure to patients.

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.

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.

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.