Risk of reintervention after endovascular aortic aneurysm repair

In-hospital thromboembolic complications after frozen elephant trunk aortic arch repair

OBJECTIVE

This study evaluated the frequency and clinical impact of thromboembolic complications after frozen elephant trunk aortic arch repair using the Thoraflex device (Terumo Aortic).

METHODS

A total of 128 consecutive patients (mean age 67.9 ± 13.7 years, 31.0% female) underwent frozen elephant trunk aortic arch repair using the Thoraflex device between September 2014 and May 2021 in 4 Canadian centers. Patient baseline characteristics, intraoperative details, and frozen elephant trunk thromboembolic complications were collected retrospectively and analyzed.

RESULTS

Fifteen patients (11.7%) had thrombus visualized within the frozen elephant trunk stent graft on imaging (n = 8; 53.3%) or had a thromboembolic event (n = 9; 60.0%) before hospital discharge. Sites of embolism were mesenteric (n = 8; 88.9%), renal (n = 4; 44.4%), and iliofemoral (n = 1; 11.1%). Patients who experienced thromboembolic complications were more likely to have a history of autoimmune disease (n = 3; 20.0% vs n = 2; 1.8%; P = .01) and implantation of a longer frozen elephant trunk stent graft (150 mm vs 100 mm) (n = 13; 86.7% vs n = 45; 39.8%; P < .001). All patients with thromboembolic complications received therapeutic anticoagulation, and a smaller proportion required an open surgical (n = 5; 33.3%) or an endovascular (n = 2; 13.3%) intervention. Radiographic resolution of thromboembolic complications was observed in 86.7% of patients (n = 13). In-hospital mortality occurred in 1 patient, stroke occurred in 1 patient, and transient spinal cord injury occurred in 1 patient.

CONCLUSIONS

Thromboembolic complications occur more often than previously recognized after frozen elephant trunk aortic arch repair using the Thoraflex device and are associated with increased rates of surgical and endovascular reintervention. Prevention and management of these complications require further study.

Factors Related to Limb Occlusion After Endovascular Abdominal Aortic Aneurysm Repair (EVAR)

BACKGROUND

Limb occlusion is a potentially serious consequence of endovascular abdominal aortic aneurysm (EVAR). This case-control study identifies factors that predispose to limb occlusion.

METHODS

A consecutive series of patients from 2 centers undergoing EVAR over an 11-year period 2007-2017 were identified retrospectively. Patient records were interrogated allowing collations of demographics, intraoperative and perioperative data and surveillance data. The preoperative computed tomography angiogram was analyzed to determine EVAR relevant anatomical data. The primary outcome was occlusion of the iliac limb of the implanted EVAR. Raw data are presented as percentages, with comparative data analyzed using Mann-Whitney U-test and binomial logistic regression.

RESULTS

A total of 787 patients (702 males; median age 78 years, range 53-94 years old) were analyzed. Fifty patients reached the primary outcome, resulting in an overall limb occlusion rate of 6.35%. Factors predictive of limb occlusion were oversizing by >10% native vessel diameter, with oversizing of >20% in 50% of those that occluded. External iliac artery landing zone (12/50 limb occlusions) 24% and postoperative kinking (5/50 limb occlusions) 10% were also more common in those that occluded. Fifty randomly selected controls with similar baseline characteristics were studied. Oversizing of the iliac endograft was found to be significantly greater in the limb occlusion group compared to the controls (P < 0.001) which remained significant on regression analysis. There was no correlation with iliac tortuosity. The Cook stent graft had a 9% limb occlusion rate across sites. Medtronic and Vascutek endografts had 2.4% and 2.5% limb occlusion rates respectively.

CONCLUSIONS

Oversizing of iliac limbs by >20% could be a contributing factor to limb occlusion after EVAR and judicious oversizing should be used.

Editor's Choice -- European Society for Vascular Surgery (ESVS) 2024 Clinical Practice Guidelines on the Management of Abdominal Aorto-Iliac Artery Aneurysms

OBJECTIVE

The European Society for Vascular Surgery (ESVS) has developed clinical practice guidelines for the care of patients with aneurysms of the abdominal aorta and iliac arteries in succession to the 2011 and 2019 versions, with the aim of assisting physicians and patients in selecting the best management strategy.

METHODS

The guideline is based on scientific evidence completed with expert opinion on the matter. By summarising and evaluating the best available evidence, recommendations for the evaluation and treatment of patients have been formulated. The recommendations are graded according to a modified European Society of Cardiology grading system, where the strength (class) of each recommendation is graded from I to III and the letters A to C mark the level of evidence.

RESULTS

A total of 160 recommendations have been issued on the following topics: Service standards, including surgical volume and training; Epidemiology, diagnosis, and screening; Management of patients with small abdominal aortic aneurysm (AAA), including surveillance, cardiovascular risk reduction, and indication for repair; Elective AAA repair, including operative risk assessment, open and endovascular repair, and early complications; Ruptured and symptomatic AAA, including peri-operative management, such as permissive hypotension and use of aortic occlusion balloon, open and endovascular repair, and early complications, such as abdominal compartment syndrome and colonic ischaemia; Long term outcome and follow up after AAA repair, including graft infection, endoleaks and follow up routines; Management of complex AAA, including open and endovascular repair; Management of iliac artery aneurysm, including indication for repair and open and endovascular repair; and Miscellaneous aortic problems, including mycotic, inflammatory, and saccular aortic aneurysm. In addition, Shared decision making is being addressed, with supporting information for patients, and Unresolved issues are discussed.

CONCLUSION

The ESVS Clinical Practice Guidelines provide the most comprehensive, up to date, and unbiased advice to clinicians and patients on the management of abdominal aorto-iliac artery aneurysms.

Exploiting endovascular aortic repair as a minimally invasive method - Nine years of experience in a non-university hospital

Background

At the introduction of endovascular aortic repair (EVAR) in 2013 in our non-university hospital, we established a quality registry to monitor our EVAR activity.

Purpose

To observe if we over time were able to exploit EVAR as a minimally invasive method in an elective as well as emergency setting, and to monitor our treatment quality in terms of complications, secondary interventions and mortality.

Material and methods

From November 2013 to March 2022, we treated 207 patients with EVAR, including six patients with rupture. Follow-up regimen was partly based on contrast-enhanced computer tomography, and partly on contrast-enhanced ultrasound in combination with plain radiography.

Results

During the observation period, the method of anesthesia changed from general, via spinal, to local anesthesia. The groin access changed from surgical cut down to percutaneous and the median length of postoperative stay decreased from 3 days to 1 day. EVAR on ruptured aneurysm was done for the first time in 2019. Endoleak was detected in 85 patients (42%) and 37 patients (18%) had one or more secondary interventions, of which 85% were endovascular. Estimated five-year survival was 72% in patients below 80 years of age and 45% in patients 80 years or older.

Conclusion

Nine years of experience enabled us to exploit EVAR's advantages as a minimally invasive method in an elective as well as emergency setting. Complications, secondary interventions and survival rates in our low volume non-university hospital matches results from larger vascular centers.

Possible implications of device-specific variability in post-endovascular aneurysm repair sac regression and endoleaks for surveillance categorization

OBJECTIVE

Significant sac regression during early surveillance has been shown to best predict reintervention-free long-term surveillance after endovascular aneurysm repair (EVAR). Furthermore, a persistent endoleak has been related to a worse outcome. Individualized surveillance algorithms based on these findings have been suggested. There are no studies comparing the performance of different stent grafts regarding sac regression, the presence of type II endoleaks, and their possible implications for individualized surveillance. The objective of this study was to evaluate device-specific differences and how these may affect patient categorization for surveillance.

METHODS

Patients were treated electively with standard EVAR between 2005 and 2015 using three different devices (Zenith by Cook, Excluder by Gore, and Endurant by Medtronic). The data were reviewed retrospectively until 2020. Patients' computed tomography angiographies (CTAs) at 30 days and at 2 years were analyzed for freedom from endoleaks and for sac regression of ≥5 mm. Reinterventions during long-term surveillance were counted. Patients were categorized according to the presence of any endoleak and sac regression at 30 days and 2 years, and the probability of reintervention-free long-term surveillance was evaluated based on these findings.

RESULTS

A total of 435 patients were treated for an abdominal aortic aneurysm with EVAR during the study period. At 30 days, 80.0% (n = 339) of the patients were free from endoleaks, and at 2 years, 78.9% (n = 273) were free from endoleaks. There was a significant difference in endoleak rate at 30 days and 2 years between the devices (P < .001 and P = .001). There was no significant difference in sac regression between the devices at 2 years (P = .096). The categorization at 30 days based on endoleak status had a sensitivity of 44.9%, specificity of 87.4%, and negative predictive value of 84.1% for finding a reintervention-requiring complication during long-term follow-up. The corresponding figures at 2 years were 63.3%, 91.4%, and 89.4%, respectively. The combination of freedom from endoleaks and sac regression of ≥5 mm in the 2-year CTA best predicted an uneventful long-term surveillance. Patients who met this criterion had a 95.6% probability (negative predictive value) of having a reintervention-free long-term surveillance.

CONCLUSIONS

There are significant differences in the prevalence of endoleaks between devices at 30 days and 2 years, but there is no difference in sac regression. Patients with sac regression of ≥5 mm and no endoleaks in the 2-year CTA can be safely categorized for infrequent surveillance regardless of the stent graft model that has initially been used.

The benefits of a centralized remote surveillance program for vascular patients

OBJECTIVE

We aimed to assess the clinical and financial utility of a centralized remote surveillance program for vascular patients compared with traditional outpatient follow-up.

METHODS

In 2014, the Royal Adelaide Hospital Department of Vascular Surgery introduced a centralized remote surveillance program where suitable patients were monitored by remote imaging in lieu of traditional outpatient appointments (OPAs). Surveillance imaging was performed at a site local to the patient and was reviewed centrally by a dedicated surveillance nurse. We undertook a 5-year retrospective analysis of the program's prospectively maintained database since its inception. Costs for inpatient admissions and OPAs were retrieved from hospital financial databases. The surveillance database and electronic patient records were analyzed for number and outcome of surveillance scans, interventions, and OPAs. Additional savings in travel distance, fuel costs, and CO₂ emissions were also calculated.

RESULTS

Over 5 years, 1262 patients underwent a mean of four scans per patient. A total of 3718 OPAs were saved, approximating 930 hours of clinic and consultant time, with associated savings of Australian (A)$1,524,900 (United States [US]$ 1,065,684) over 5 years (A$ 304,980 [US$ 213,137] per year). For every OPA avoided, each patient saved 197 km travel and A$87 (US$ 61) fuel costs, with an associated 115 kg of CO₂ emissions saved. Over 5 years, this equated to savings of 248,173 km travel, A$ 110,136 (US$ 76,969) fuel costs, and 146 tons of CO₂ emissions. A total of 134 surveillance-detected pathologies (10.6%) required intervention, a further 28 despite surveillance (2.2%), and three following surveillance cessation (0.2%). Subgroup analysis demonstrated that interventions despite surveillance were three times more expensive and incurred four times longer admissions than those due to surveillance.

CONCLUSIONS

Remote vascular surveillance, particularly applicable in our current COVID-19 pandemic climate, is associated with quantifiable financial, clinical, patient, and environmental beneficial outcomes and can be safely delivered to populations spanning large geographical areas such as those in Australia.

Application of the AngioJet Ultra Thrombectomy Device for the Percutaneous Mechanical Treatment (PMT) of Iliac Limb Occlusion after Endovascular Aneurysm Repair (EVAR)

BACKGROUND

To investigate the safety and efficacy of applying the AngioJet Ultra thrombectomy device in treating endograft occlusions in the iliac arteries following endovascular aneurysm repair (EVAR).

METHODS

This study utilized a retrospective analysis of 452 patients with infrarenal abdominal aortic aneurysm (AAA). Twelve of the patients experienced iliac limb occlusion during their follow-up period, and the AngioJet Ultra thrombectomy device was used in tandem with iliac angioplasty to treat these patients. The safety of the device was assessed through the amount of blood drawn, the duration of the procedure, and the occurrence of post-operative complications, while its efficacy was assessed through aortic computed tomography angiography (CTA) imaging and post-operative symptomatology results.

RESULTS

All 12 patients were male, and they had a mean age of 62.8 ± 11.8 years. Iliac limb occlusion occurred on the left side of 4 patients and on the right side of 8 patients. The AngioJet Ultra thrombectomy device was used together with iliac angioplasty during surgery, with a success rate of 100%. A bifurcated endograft was successfully implanted in 9 patients following AngioJet Ultra thrombectomy and balloon dilation angioplasty, while a unibody endograft was successfully implanted in 3 patients following AngioJet Ultra thrombectomy and balloon dilation angioplasty. The mean surgery duration was 2.4 hrs, and the patients were hospitalized for an average of 4.5 days. After surgery, the patients' intermittent claudication/buttock claudication gradually vanished. Two patients experienced hemoglobinuria, with one of them developing mild renal dysfunction. Currently, the twelve patients have been followed up for an average of 12 months, and none have experienced any lower extremity ischemia.

CONCLUSIONS

The use of the AngioJet Ultra thrombectomy device as a supplementary treatment for iliac limb occlusion following abdominal EVAR is safe, effective, and minimally invasive.

Analysis of Outcomes After Endovascular Abdominal Aortic Aneurysm Repair in Patients With Abnormal Findings on the First Postoperative Computed Tomography Angiography

Purpose:

Lifelong follow-up after endovascular abdominal aortic aneurysm repair (EVAR) is recommended due to a continued risk of complications, especially if the first postoperative imaging shows abnormal findings. We studied the long-term outcomes in patients with abnormalities on the first postoperative computed tomography angiography (CTA) following EVAR.

Materials and Methods:

This is a retrospective study of all consecutive patients who underwent elective EVAR for nonruptured abdominal aortic aneurysm (AAA) between January 2007 and January 2012 in 16 Dutch hospitals with follow-up until December 2018. Patients were included if the first postoperative CTA showed one of the following abnormal findings: endoleak type I–IV, endograft kinking, infection, or limb occlusion. AAA diameter, complications, and secondary interventions during follow-up were registered. Primary endpoint was overall survival, and other endpoints were secondary interventions and intervention-free survival. Kaplan-Meier analyses were used to estimate overall and intervention-free survival. Cox regression analyses were used to identify the association of independent determinants with survival and secondary interventions.

Results:

A total of 502 patients had abnormal findings on the first postoperative CTA after EVAR and had a median follow-up (interquartile range IQR) of 83.0 months (59.0). The estimated overall survival rate at 1, 5, and 10 years was 84.7%, 51.0%, and 30.8%, respectively. Age [hazard ratio (HR) 1.06, 95% confidence interval (CI) 1.05 to 1.10] and American Society of Anesthesiologists (ASA) classification (ASA IV HR 3.20, 95% CI 1.99 to 5.15) were significantly associated with all-cause mortality. Overall, 167 of the 502 patients (33.3%) underwent 238 secondary interventions in total. Fifty-eight patients (12%) underwent an intervention based on a finding on the first postoperative CTA. Overall survival was 38.4% for patients with secondary interventions and 44.5% for patients without (log rank; p=0.166). The intervention-free survival rate at 1, 5, and 10 years was 82.9%, 61.3%, and 45.6%, respectively.

Conclusions:

Patients with abnormalities on the first postoperative CTA after elective EVAR for infrarenal AAA cannot be discharged from regular imaging follow-up due to a high risk of secondary interventions. Patients who had a secondary intervention had similar overall survival as those without secondary interventions.

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.

Results of adjunctive stenting with high-radial force stents to prevent or treat limb occlusion after EVAR

BACKGROUND

The aim of this study was to report the results of a multicenter experience on the use of adjunctive stents deployed inside abdominal aortic endografts with the purpose to prevent or treat limb occlusion after endovascular aneurysm repair (EVAR).

METHODS

Between 2010 and 2018, there were 35 patients with aorto-iliac aneurysm presenting one or more risk factors for endograft limb occlusion (narrow aortic bifurcation and/or stenotic, highly angulated or occluded iliac arteries), who were treated with standard bifurcated stent graft reinforced by the means of a single model of balloon-expandable platinum/iridium bare stent (CP Stent; NuMED, Inc., Hopkinton, NY, USA). Technical success, mortality, limb patency and reintervention rate during follow-up were the main endpoints assessed.

RESULTS

Technical success was 100%. No patients died perioperatively and no major complication was registered. During a mean follow-up of 48 months (range 1-87), neither aortic-related death nor secondary intervention was registered. At a mean follow-up imaging of 39.4 months (range 1-81) no endograft limb lost its patency.

CONCLUSIONS

The use of high-radial force balloon-expandable stents deployed inside bifurcated endografts to prevent or treat limb occlusion is a safe and effective adjunctive procedure, with outstanding long-term outcomes in terms of patency and reinterventions.

Comparison of Outcomes Following EVAR Based on Aneurysm Diameter and Volume and Their Postoperative Variations

PURPOSE

to evaluate the impact of bi- and 3-dimensional preoperative aortic morphological features and their immediate postoperative variations on the outcome of abdominal aortic aneurysms (AAA) treated by endovascular exclusion with standard devices (EVAR).

MATERIALS AND METHODS

Double centre retrospective analysis of prospectively collected registry data of EVAR patients. For all patients, preoperative and 30-day computed tomographic angiography images (CTA) were reviewed. Preoperative maximum AAA diameter >59 mm and volume >159 cm³, and any 30-day postoperative increasing at CTA, were considered as potentially influencing the outcome. The outcome measures were: primary technical success; 30-day, 1-year, and mean follow-up reintervention, all-cause and AAA-related mortality rates, and also endoleak-related reinterventions.

RESULTS

Three hundred and thrity-three patients were enrolled. Mean preoperative and 30-day AAA diameter and volume were 50.4 mm ± 11.8 vs. 49.1 mm ± 12.1, and 112.9 cm3 ± 79.5 vs. 112.1 cm3 ± 80.5, respectively. Primary technical success was achieved in all cases. At 34.9 months follow-up, cumulative reintervention rate was 12.0%, mortality rates 7.2%, without AAA-related deaths. Endoleak-related reintervention rate was 7.5%. At uni- and multi-variate analysis, preoperative AAA diameter >59 mm, and AAA volume >159 cm³ were significantly associated to reintervention (P = 0.012; P = 0.002), and reintervention and death (P = 0.002; P = 0.001) during follow-up. Additionally, any increase in postoperative AAA diameter or volume was significantly associated with reintervention (P = 0.001, P = 0.001) and reintervention and death (P = 0.006, P = 0.001). Endoleak-related reintervention were also significantly associated with all of the analysed morphological parameters (P = 0.019, P = 0.005, P = 0.005, and P = 0.002, respectively).

CONCLUSIONS

Patients with larger baseline AAA size and volume as well as unfavourable early remodelling of the sac are associated to worse long-term EVAR outcome.

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.

Surveillance Imaging following Endovascular Aneurysm Repair: State of the Art

Endovascular aneurysmal repair (EVAR) has become a prominent modality for the treatment of abdominal aortic aneurysm. Surveillance imaging is important for the detection of device-related complications, which include endoleak, structural abnormalities, and infection. Currently used modalities include ultrasound, X-ray, computed tomography, magnetic resonance imaging, and angiography. Understanding the advantages and drawbacks of each modality, as well available guidelines, can guide selection of the appropriate technique for individual patients. We review complications following EVAR and advances in surveillance imaging modalities.

Endurant stent graft demonstrates promising outcomes in challenging abdominal aortic aneurysm anatomy

OBJECTIVE

We aimed to assess the 5-year safety and effectiveness outcomes of patients enrolled in the Endurant Stent Graft Natural Selection Global Post Market Registry (ENGAGE) who were treated outside the approved indications for use (IFU) of the Endurant stent graft.

METHODS

Our primary outcome measure was 12-month treatment success, defined as successful endograft delivery and deployment and the absence of type I or III endoleak, stent migration or limb occlusion, late conversion, and abdominal aortic aneurysm diameter increase or rupture. Secondary outcome measures included 30-day all-cause mortality, major adverse events, secondary procedures, technical observations, aneurysm-related mortality, and all-cause mortality within 12 months.

RESULTS

Demographic characteristics of ENGAGE patients treated outside (225 [17.8%]) and within (1038 [82.2%]) the IFUs were similar, except that female patients comprised a much higher percentage of the outside IFU group (19.1% vs 8.7%; P < .001). The outside IFU group presented with lower rates of coronary artery disease and cardiac revascularization and a greater number of symptomatic patients compared with the within IFU group (21.3% vs 15.0%; P = .020). Technical success was achieved in more than 99% of all patients. The outside and within IFU groups showed a comparable and low occurrence of uncorrected type I (0.9% vs 1.2%; P = 1.00) and type III endoleak (0.4% vs 0.3%; P = .54) immediately after device implantation. The 5-year freedom from type IA endoleaks was 89.4% vs 96.7% (P < .0001) for those patients outside and within the IFUs, respectively, although both groups had similar type III endoleaks through 5 years (P = .61). Stent graft limb occlusion estimated overall survival, and freedom from aneurysm-related mortality and endovascular interventions were comparable in both patient groups through the 5-year follow-up. The Kaplan-Meier estimates at 5 years showed a trend for low but increased need for type I or III endoleak correction procedures in the outside IFU group compared with the within IFU group (7.2% vs 5.2%; P = .099).

CONCLUSIONS

Differences were not observed in all-cause mortality, aneurysm-related mortality, and secondary procedures between within and outside IFU patients through a 5-year follow-up in the ENGAGE registry. Proximal necks with angulation or diameters outside the IFUs were the most common reasons for patients identified as being outside IFU, and the cohort had increased incidence of type IA endoleaks. Despite the challenges presented from the broad range of aortic and abdominal aortic aneurysm morphologies, the Endurant stent graft showed promising 5-year outcomes.

Impact of Centralisation on Abdominal Aortic Aneurysm Repair Outcomes: Early Experience in Catalonia

OBJECTIVE

Several studies have revealed high volume centres have better outcomes in the treatment of abdominal aortic aneurysms (AAAs), thus supporting centralisation of this procedure into selected centres based on volume. To date however, the real benefit of centralisation of this pathology has not been well demonstrated. The aim of this study was to analyse the impact of centralisation in to high volume centres (defined as those performing more than 30 cases per year) on AAA treatment outcomes carried out in Catalonia (Spain).

METHODS

Data were collected from official national registries (HDMBD) for AAA treated by endovascular aneurysm repair (EVAR) or open repair (OR) over a nine year period. Two time periods were selected for comparison: before centralisation (2009-2014) and after complete centralisation (2015-2017). The primary objective was to determine short term mortality (in hospital and 30 day mortality) and length of stay (LOS) after intact AAA (iAAA) and ruptured AAA (rAAA) repair, before and after centralisation. Uni- and multivariable analyses were performed in order to identify independent outcomes predictors.

RESULTS

A total of 3 501 iAAAs, including 1 124 (32.1%) OR and 2377 (67.9%) EVAR, and 409 rAAAs, including 218 (53.3%) OR and 191 (46.7%) EVAR, were identified. After centralisation, there was a significant decrease in overall mortality in iAAA repair (4.7% vs. 2.0%, p < .001) and rAAA repair (53.1% vs. 41.9%, p = .028). Mortality reduction in iAAAs was significant for OR (8.7% vs. 3.6%, p = .005), but not for EVAR (2.2% vs. 1.5%, p = .25). Overall LOS decreased as well, mainly in iAAAs (9.49 ± 10.84 vs. 7.44 ± 12.23 days, p < .001), and in particular in elective EVAR (7.32 ± 7.73 vs. 6.00 ± 8.97 days, p < .001). Multivariable analysis was identified before the centralisation period as an independent predictor for both mortality (odds ratio 1.484, 95% CI 1.098-2.005, p = .010) and LOS (B coefficient 1.146, 95% CI 0.218-2.073, p = .016).

CONCLUSION

The implementation of a country based centralisation programme for AAA treatment led to a significant reduction in short term mortality, for both iAAA and rAAA, and mainly for elective OR. LOS also significantly decreased, mainly for elective EVAR. These results support the benefit of centralisation of AAA repair procedures.

Editor's Choice - Detection of Late Complications After Endovascular Abdominal Aortic Aneurysm Repair and Implications for Follow up Based on Retrospective Assessment of a Two Centre Cohort

OBJECTIVE

Endovascular aortic aneurysm repair (EVAR) is associated with the risk of late complications and mandates follow up. This retrospective study assessed post-EVAR complications in a two centre cohort. The study evaluated the rate of complications presenting with symptoms vs. those detected by imaging follow up. Additionally, the agreement between DUS and CTA in detecting complications was assessed in patients with both.

METHODS

All EVAR patients from 1998 to 2012 in two centres were included. Complications were classified based on whether they were symptomatic or detected by imaging, as well as based on imaging detection modality (DUS or CTA). For patients who had undergone DUS and CTA within three months of each other, the kappa coefficient of agreement was assessed.

RESULTS

Four hundred and fifty-four patients treated by EVAR were identified. The median follow up time was 5.2 (IQR 2.8-7.6) years. One hundred and eighteen patients (26%) developed 176 complications. One hundred and six (60.2%) of the complications were asymptomatic, and 70 (39.8%) were symptomatic. Two hundred and fifty-three patients had imaging with both modalities within three months of each other; the kappa coefficient for agreement between CTA and DUS for detecting clinically significant complications was 0.91. Regarding CTA as the standard modality, DUS had a sensitivity of 88.8% (95% CI 77.3-95.8%) and a specificity of 99.4% (95% CI 97.1-99.9%). Three of the complications missed by DUS were related to loss of proximal and distal seal, all occurring in patients with short sealing length on first post-operative CT scan.

CONCLUSION

Approximately a quarter of the patients developed complications, the majority of which were asymptomatic, underlining the importance of adequate surveillance. There was good agreement between CTA and DUS in detecting complications. Clinically significant complications related to inadequate seal were missed by DUS, suggesting that CTA still plays an important role in EVAR surveillance.

Postoperative surveillance and long-term outcome after endovascular aortic aneurysm repair in the Netherlands: study protocol for the retrospective ODYSSEUS study

INTRODUCTION

Strict imaging surveillance protocols to detect complications following endovascular aneurysm repair (EVAR) are common practice. However, controversy exists as to whether all EVAR patients need intense surveillance. The 2019 European Society for Vascular Surgery guidelines for management of abdominal aortic aneurysm (AAA) suggest that patients may be considered for limited follow-up with imaging if classified as 'low risk' for complications based on their initial postoperative imaging. The current study aims to investigate the intervention-free survival and overall survival stratified for patients with and without yearly imaging surveillance.

METHODS AND ANALYSIS

The Observing a Decade of Yearly Standardised Surveillance in EVAR patients with Ultrasound or CT Scan study comprises a national multicentre retrospective cohort study in 17 medical centres. Consecutive patients with an asymptomatic or symptomatic infrarenal AAA who underwent EVAR between January 2007 and January 2012 will be included in this study with follow-up until December 2018. Clinical variables and all follow-up information will be retrieved in extensive data collection from the patient's medical records. In addition, an e-survey was sent to vascular surgeons at the 17 participating centres to gauge their opinions regarding the possibility of safely reducing the frequency of imaging surveillance. Primary endpoints are intervention after EVAR and aneurysm-related mortality. The initial estimated sample size is 1997 patients.

ETHICS AND DISSEMINATION

The study has been approved by the Medical Ethics Review Committee of the Amsterdam UMC, location Academic Medical Centre, Amsterdam, the Netherlands. Study findings will be disseminated via presentations at conferences and publications in peer-reviewed journal.

TRIAL REGISTRATION NUMBER

The Netherlands Trial Registry, NL6953 (old: NTR28773).

Effect of Imaging Surveillance After Endovascular Aneurysm Repair on Reinterventions and Mortality: A Systematic Review and Meta-analysis

Purpose: To study the effects of imaging surveillance after endovascular aortic repair (EVAR) on reintervention and mortality. Materials and Methods: A systematic review was conducted comparing complication rates in EVAR patients compliant with the imaging surveillance protocol vs partially or noncompliant patients. Two authors independently selected articles and performed quality assessment and data extraction. Risk differences for reintervention and mortality between compliant and partially/noncompliant patients were meta-analyzed. The pooled risk difference (RD) is reported with the 95% confidence interval (CI). The review protocol is registered at Prospero (CRD42017080494). Results: A total of 11 cohort studies involving 21,838 patients were included. Studies differed in imaging, their surveillance protocols, and definitions of compliance subgroups. Median follow-up was 31.7 months (interquartile range 29.8, 49.3). The overall reintervention rate was 5%, while the overall mortality was 31%. The RD for the reintervention rate was 4% (95% CI 1% to 7%) in favor of partial/noncompliance [number needed to harm 25 (95% CI 14 to 100)], while mortality showed a nonsignificant RD of 12% (95% CI −2% to 26%) in favor of partial/noncompliance. Two studies reported that 41% to 53% of reinterventions were performed for complications detected through imaging surveillance; the other events were detected through patient symptoms. Conclusion: Patients who are compliant with imaging surveillance appear to undergo more reinterventions than those who are partially or noncompliant. However, imaging surveillance does not seem to protect against mortality. This suggests that the recommended yearly imaging surveillance may not be beneficial for all EVAR patients.

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.

Comparison of major adverse event rates after elective endovascular aneurysm repair in New England using a novel measure of complication severity

OBJECTIVE

Major adverse event (MAE) rates are used as an outcome measure after surgical procedures. Although MAE rates summarize the occurrences of adverse events, they do not reflect differences in severity of these events. We propose that a measure of complication severity could provide a more accurate assessment about the quality of care. We aimed to analyze and to describe the regional variation in elective endovascular aneurysm repair (EVAR) MAE rates across centers in the Vascular Study Group of New England and to create an index for describing complication severity.

METHODS

Patients undergoing elective EVAR (n = 4731) at 30 Vascular Study Group of New England centers between 2003 and 2016 were studied. The MAE composite end point was defined as the occurrence of any of the following postoperative events: myocardial infarction, dysrhythmia, congestive heart failure, leg ischemia, renal insufficiency, bowel complication, reoperation, surgical site infection, stroke, respiratory complication, and no home discharge. An adjustment factor (complication severity index) was calculated as a ratio of length of stay for complicated to uncomplicated cases. Multivariate logistic regression was used to calculate predicted MAE rates. The observed and predicted MAE rates as well as complication severity index rates were compared among centers and across quintiles of center volume.

RESULTS

Observed MAE rates varied widely, ranging from 0% to 39%. Multivariate predictors of MAE included abdominal aortic aneurysm diameter >6 cm (odds ratio [OR], 2.1; 95% confidence interval [CI], 2.0-2.3), female sex (OR, 2.0; 95% CI, 1.8-2.2), chronic renal insufficiency (OR, 1.9; 95% CI, 1.7-2.1), age >75 years (OR, 1.9; 95% CI, 1.8-2.1), congestive heart failure (OR, 1.7; 95% CI, 1.5-1.9), chronic obstructive pulmonary disease (OR, 1.5; 95% CI, 1.4-1.6), diabetes (OR, 1.4; 95% CI, 1.1-1.7), positive stress test result (OR, 1.2; 95% CI, 1.1-1.4), preoperative beta blocker (OR, 1.2; 95% CI, 1.1-1.3), and no preoperative statin (OR, 1.2; 95% CI, 1.1-1.3). Predicted MAE rates had little variation (range, 21%-29%). In comparing observed MAE rates and complication severity, there was an inverse relation between the two, suggesting that although certain centers had a greater number of MAEs, the complications were less severe.

CONCLUSIONS

MAE rates after elective EVAR vary widely. However, centers with higher MAE rates tended to have less severe complications, suggesting that observed MAE rates may not be a good measure of outcomes assessment after elective EVARs.

There Is Limited Value in the One Month Post Endovascular Aortic Aneurysm Repair Surveillance Computed Tomography Scan

BACKGROUND

Endovascular aortic aneurysm repair (EVAR) is the preferred first-line treatment for abdominal aortic aneurysms. Current postprocedure surveillance recommendations by manufacturers are a 1-month computed tomography angiography (CTA) followed by a 12-month CTA in most circumstances. The objective of this study is to determine the utility of the 1-month CTA following elective EVAR and determine if initial surveillance at 6-month CTA is appropriate.

METHODS

A single-center retrospective chart review of all elective EVARs at a tertiary medical center over a 12-year period was conducted. Patients were excluded if postoperative surveillance imaging was not available. Data analysis encompassed demographics, chart review, and imaging including angiogram and cross-sectional imaging to asses for endoleaks and other findings.

RESULTS

There were 363 patients who underwent elective EVAR and had available postoperative imaging during the study period. Within the 1-month follow-up, a CTA group of 316 patients was detected with 98 (31%) endoleaks. Of these, 5 (1.5%) required intervention: 1 for infolding of an iliac limb and 4 for type I endoleak which was present on completion angiogram-3 in patients treated outside of instructions for use and 1 with a type Ib endoleak on intraoperative completion imaging. In the 158 patients with 1 and 3-month CTAs, there were 47 persistent endoleaks, 9 previously undetected endoleaks not seen in 1-month CTA, and 13 resolved endoleaks. Three patients (1.2%) underwent intervention for type II endoleak and aneurysm expansion. In 47 patients with only a 6-month CTA, there were 16 endoleaks not seen on completion angiography and 2 of which were treated with reintervention-1 for a type I endoleak and 1 for a type II endoleak.

CONCLUSIONS

There is limited utility to 1-month surveillance CTA in patients undergoing elective EVAR within the device instructions for use that has no evidence of type I endoleak on completion angiography. It is safe to start routine EVAR surveillance at 6 months in this patient population. This has implications when considering bundled and value-based payments in the longitudinal care of abdominal aortic aneurysm patients.

Complications of endovascular aneurysm repair of the thoracic and abdominal aorta: evaluation and management

In recent decades, endovascular aneurysm repair or endovascular aortic repair (EVAR) has become an acceptable alternative to open surgery for the treatment of thoracic and abdominal aortic aneurysms and other aortic pathologies such as the acute aortic syndromes (e.g., penetrating aortic ulcer, intramural hematoma, dissection). Available data suggest that endovascular repair is associated with lower perioperative 30-day all-cause mortality as well as a significant reduction in perioperative morbidity when compared to open surgery. Additionally, EVAR leads to decreased blood loss, eliminates the need for cross-clamping the aorta and has shorter recovery periods than traditional surgery. It is currently the preferred mode of treatment of thoracic and abdominal aortic aneurysms in a subset of patients who meet certain anatomic criteria conducive to endovascular repair. The main disadvantage of EVAR procedures is the high rate of post-procedural complications that often require secondary re-intervention. As a result, most authorities recommend lifelong imaging surveillance following repair. Available surveillance modalities include conventional radiography, computed tomography, magnetic resonance angiography, ultrasonography, nuclear imaging and conventional angiography, with computed tomography currently considered to be the gold standard for surveillance by most experts. Following endovascular abdominal aortic aneurysm (AAA) repair, the rate of complications is estimated to range between 16% and 30%. The complication rate is higher following thoracic EVAR (TEVAR) and is estimated to be as high as 38%. Common complications include both those related to the endograft device and systemic complications. Device-related complications include endoleaks, endograft migration or collapse, kinking and/or stenosis of an endograft limb and graft infection. Post-procedural systemic complications include end-organ ischemia, cerebrovascular and cardiovascular events and post-implantation syndrome. Secondary re-interventions are required in approximately 19% to 24% of cases following endovascular abdominal and thoracic aortic aneurysm repair respectively. Typically, most secondary reinterventions involve the use of percutaneous techniques such as placement of cuff extension devices, additional endograft components or stents, enhancement of endograft fixation, treatment of certain endoleaks using various embolization techniques and embolic agents and thrombolysis of occluded endograft components. Less commonly, surgical conversion and/or open surgical modification are required. In this article, we provide an overview of the most common complications that may occur following endovascular repair of thoracic and AAAs. We also summarize the current surveillance recommendations for detecting and evaluating these complications and discuss various current secondary re-intervention approaches that may typically be employed for treatment.

Follow-up after endovascular aortic aneurysm repair can be stratified based on first postoperative imaging

Background

Lifelong postoperative surveillance is recommended following endovascular aneurysm repair (EVAR). Although the purpose is to prevent and/or identify complications early, it also results in increased cost and workload. This study was designed to examine whether it may be possible to identify patients at low risk of complications based on their first postoperative CT angiogram (CTA).

Methods

All patients undergoing EVAR in two Swedish centres between 2001 and 2012 were identified retrospectively and categorized based on the first postoperative CTA as at low risk (proximal and distal sealing zone at least 10 mm and no endoleak) or high risk (sealing zone less than 10 mm and/or presence of any endoleak) of complications.

Results

Some 326 patients (273 men) with a CTA performed less than 1 year after EVAR were included (low risk 212, 65·0 per cent; high risk 114, 35·0 per cent). There was no difference between the groups in terms of sex, age, co-morbidities, abdominal aortic aneurysm (AAA) diameter, preoperative AAA neck anatomy, stent-graft type or duration of follow-up (mean(s.d.) 4·8(3·2) years). Five-year freedom from AAA-related adverse events was 97·1 and 47·7 per cent in the low- and high-risk groups respectively (P &lt; 0·001). The corresponding freedom from AAA-related reintervention was 96·2 and 54·1 per cent (P &lt; 0·001). The method had a sensitivity of 88·3 per cent, specificity of 77·0 per cent and negative predictive value of 96·6 per cent to detect AAA-related adverse events. The number of surveillance imaging per AAA-related adverse event was 168 versus 11 for the low-risk versus high-risk group.

Conclusion

Two-thirds of patients undergoing EVAR have an adequate seal and no endoleak on the first postoperative CTA, and a very low risk of AAA-related events up to 5 years. Less vigilant follow-up after EVAR may be considered for these patients.

Comparison of Clinical Outcomes between Surgical Repair and Endovascular Stent for the Treatment of Abdominal Aortic Aneurysm

Purpose

This study was performed to compare the treatment outcomes between endovascular aneurysm repair (EVAR) and open surgical repair (OSR) of abdominal aortic aneurysms (AAAs) in a South Korean population.

Materials and Methods

We performed a retrospective review of the medical records of 99 patients with AAAs who were managed at Gyeongsang National University Hospital between January 2005 and December 2014. We reviewed the demographic characteristics and perioperative treatment outcomes of patients with AAA undergoing EVAR or OSR. In-hospital mortality and reintervention rates were assessed and compared between the EVAR and OSR groups.

Results

In-hospital mortality was not significantly higher in the OSR group versus the EVAR group (3.8% vs. 8.7%, respectively, P=0.41). Intervention time (209.6 mins vs. 350.9 mins, P<0.001) and length of hospital stay (7.79 days vs. 17.46 days, P<0.001) were significantly longer in the OSR group vs. the EVAR group. Median follow-up time was 24.1±20 months for the EVAR group and 43.9±28 months for the OSR group. The cumulative rate of freedom from reintervention at 60 months was 62.0% for the EVAR group and 100% for the OSR group (P<0.001).

Conclusion

EVAR was favorable in terms of intervention time and length of hospital stay, but the long-term durability of EVAR remains open for further debate.

Editor's Choice - The Implications of Non-compliance to Endovascular Aneurysm Repair Surveillance: A Systematic Review and Meta-analysis

OBJECTIVE/BACKGROUND

Increasingly, reports show that compliance rates with endovascular aneurysm repair (EVAR) surveillance are often suboptimal. The aim of this study was to determine the safety implications of non-compliance with surveillance.

METHODS

The study was carried out according to the Preferred Items for Reporting of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search was undertaken by two independent authors using Embase, MEDLINE, Cochrane, and Web of Science databases from 1990 to July 2017. Only studies that analysed infrarenal EVAR and had a definition of non-compliance described as weeks or months without imaging surveillance were analysed. Meta-analysis was carried out using the random-effects model and restricted maximum likelihood estimation.

RESULTS

Thirteen articles (40,730 patients) were eligible for systematic review; of these, seven studies (14,311 patients) were appropriate for comparative meta-analyses of mortality rates. Three studies (8316 patients) were eligible for the comparative meta-analyses of re-intervention rates after EVAR and four studies (12,995 patients) eligible for meta-analysis for abdominal aortic aneurysm related mortality (ARM). The estimated average non-compliance rate was 42.0% (95% confidence interval [CI] 28-56%). Although there is some evidence that non-compliant patients have better survival rates, there was no statistically significant difference in all cause mortality rates (year 1: odds ratio [OR] 5.77, 95% CI 0.74-45.14; year 3: OR 2.28, 95% CI 0.92-5.66; year 5: OR 1.81, 95% CI 0.88-3.74) and ARM (OR 1.47, 95% CI 0.99-2.19) between compliant and non-compliant patients in the first 5 years after EVAR. The re-intervention rate was statistically significantly higher in compliant patients from 3 to 5 years after EVAR (year 1: OR 6.36, 95% CI 0.23-172.73; year 3: OR 3.94, 85% CI 1.46-10.69; year 5: OR 5.34, 95% CI 1.87-15.29).

CONCLUSION

This systematic review and meta-analysis suggests that patients compliant with EVAR surveillance programmes may have an increased re-intervention rate but do not appear to have better survival rates than non-compliant patients.

Using multiple classifiers for predicting the risk of endovascular aortic aneurysm repair re-intervention through hybrid feature selection

Feature selection is essential in medical area; however, its process becomes complicated with the presence of censoring which is the unique character of survival analysis. Most survival feature selection methods are based on Cox's proportional hazard model, though machine learning classifiers are preferred. They are less employed in survival analysis due to censoring which prevents them from directly being used to survival data. Among the few work that employed machine learning classifiers, partial logistic artificial neural network with auto-relevance determination is a well-known method that deals with censoring and perform feature selection for survival data. However, it depends on data replication to handle censoring which leads to unbalanced and biased prediction results especially in highly censored data. Other methods cannot deal with high censoring. Therefore, in this article, a new hybrid feature selection method is proposed which presents a solution to high level censoring. It combines support vector machine, neural network, and K-nearest neighbor classifiers using simple majority voting and a new weighted majority voting method based on survival metric to construct a multiple classifier system. The new hybrid feature selection process uses multiple classifier system as a wrapper method and merges it with iterated feature ranking filter method to further reduce features. Two endovascular aortic repair datasets containing 91% censored patients collected from two centers were used to construct a multicenter study to evaluate the performance of the proposed approach. The results showed the proposed technique outperformed individual classifiers and variable selection methods based on Cox's model such as Akaike and Bayesian information criterions and least absolute shrinkage and selector operator in p values of the log-rank test, sensitivity, and concordance index. This indicates that the proposed classifier is more powerful in correctly predicting the risk of re-intervention enabling doctor in selecting patients' future follow-up plan.

Feature selection through validation and un-censoring of endovascular repair survival data for predicting the risk of re-intervention

Background

Feature selection (FS) process is essential in the medical area as it reduces the effort and time needed for physicians to measure unnecessary features. Choosing useful variables is a difficult task with the presence of censoring which is the unique characteristic in survival analysis. Most survival FS methods depend on Cox’s proportional hazard model; however, machine learning techniques (MLT) are preferred but not commonly used due to censoring. Techniques that have been proposed to adopt MLT to perform FS with survival data cannot be used with the high level of censoring. The researcher’s previous publications proposed a technique to deal with the high level of censoring. It also used existing FS techniques to reduce dataset dimension. However, in this paper a new FS technique was proposed and combined with feature transformation and the proposed uncensoring approaches to select a reduced set of features and produce a stable predictive model.

Methods

In this paper, a FS technique based on artificial neural network (ANN) MLT is proposed to deal with highly censored Endovascular Aortic Repair (EVAR). Survival data EVAR datasets were collected during 2004 to 2010 from two vascular centers in order to produce a final stable model. They contain almost 91% of censored patients. The proposed approach used a wrapper FS method with ANN to select a reduced subset of features that predict the risk of EVAR re-intervention after 5 years to patients from two different centers located in the United Kingdom, to allow it to be potentially applied to cross-centers predictions. The proposed model is compared with the two popular FS techniques; Akaike and Bayesian information criteria (AIC, BIC) that are used with Cox’s model.

Results

The final model outperforms other methods in distinguishing the high and low risk groups; as they both have concordance index and estimated AUC better than the Cox’s model based on AIC, BIC, Lasso, and SCAD approaches. These models have p-values lower than 0.05, meaning that patients with different risk groups can be separated significantly and those who would need re-intervention can be correctly predicted.

Conclusion

The proposed approach will save time and effort made by physicians to collect unnecessary variables. The final reduced model was able to predict the long-term risk of aortic complications after EVAR. This predictive model can help clinicians decide patients’ future observation plan.

Electronic supplementary material

The online version of this article (doi:10.1186/s12911-017-0508-3) contains supplementary material, which is available to authorized users.

A Systematic Review of Predictors of Reintervention After EVAR: Guidance for Risk-Stratified Surveillance

BACKGROUND

Current surveillance protocols after endovascular aneurysm repair (EVAR) are ineffective and costly. Stratifying surveillance by individual risk of reintervention requires an understanding of the factors involved in developing post-EVAR complications. This systematic review assessed risk factors for reintervention after EVAR and proposals for stratified surveillance.

METHODS

A systematic search according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was performed using EMBASE and MEDLINE databases to identify studies reporting on risk factors predicting reintervention after EVAR and proposals for stratified surveillance.

RESULTS

Twenty-nine studies reporting on 39 898 patients met the primary inclusion criteria for reporting predictors of reintervention or aortic complications with or without suggestions for stratified surveillance. Five secondary studies described external validation of risk scores for reintervention or aortic complications. There was great heterogeneity in reporting risk factors identified at the pre-EVAR, intraoperative, and post-EVAR stages of treatment, although large preoperative abdominal aortic aneurysm diameter was the most commonly observed risk factor for reintervention after EVAR.

CONCLUSION

Existing data on predictors of post-EVAR complications are generally of poor quality and largely derived from retrospective studies. Few studies describing suggestions for stratified surveillance have been subjected to external validation. There is a need to refine risk prediction for EVAR failure and to conduct prospective comparative studies of personalized surveillance with standard practice.

Endovascular aneurysm sealing addresses several limitations of conventional endovascular aneurysm repair

Endovascular aneurysm repair has enabled a broad population of patients with infrarenal abdominal aortic aneurysm to be treated by a less-invasive technique. However, endovascular aneurysm repair has therapeutic limitations, including the need for lifelong surveillance and a higher rate of secondary interventions than open repair. These outcomes can promote patient dissatisfaction and result in increased health care costs and associated morbidity and mortality. The primary reason for secondary interventions is continued abdominal aortic aneurysm sac enlargement due to endoleaks. Conventional endovascular aneurysm repair procedures do not address aortic branch vessels that are ligated during open repairs. Secondary measures to occlude these branch vessels have shown efficacy in limiting sac growth, but do not predictably eliminate the need for further interventions. Endovascular aneurysm sealing is a new technique that addresses some of the limitations of conventional endovascular repair. Endovascular aneurysm sealing secures the stent graft flow lumens within a biostable polymer. This stability prevents stent migration while also sealing branch vessels that are otherwise not addressed by other endovascular devices. This new approach to endovascular repair has shown early promise in reducing the rates of endoleak and need for secondary interventions, while opening up the possibility of durable endovascular repair to a more challenging type of anatomy.

Secondary interventions after endovascular aneurysm sac sealing: endoleak embolization and limb-related interventions

The Nellix endovascular aneurysm sealing system is a novel alternative to conventional endovascular aneurysm repair for aortic aneurysm management using paired balloon expandable endografts supported by polymer-filled endobags to achieve sealing and anatomic fixation. Part of the promise of endovascular aneurysm sealing is increased resistance to lateral and longitudinal forces and thus a potential for reduced rates of device-related failures, particularly endoleaks. Initial efficacy data on this device are encouraging, but our knowledge of its associated complications and their management is limited. Reported adverse events include Type 1 and 2 endoleaks, graft stenosis and occlusion. The aim of this article is to review the early experience of endovascular aneurysm sealing focusing on the incidence, significance, and management of device-related complications.

Extended use of endovascular aneurysm sealing: Chimneys for juxtarenal aneurysms

Hostile infrarenal aortic neck anatomy presents a challenge for the endovascular treatment of abdominal aortic aneurysm. Open surgical repair has been seen as the gold standard treatment for juxtarenal abdominal aortic aneurysm; however, endovascular techniques are now becoming more prevalent, particularly in patients deemed high risk for morbidity and mortality with open repair. The morphology of an aneurysm is a determinant of long-term outcomes, and short aneurysm necks are associated with poorer outcomes and a higher rate of secondary reinterventions. Parallel grafts have been used in combination with endovascular aneurysm repair to elongate the sealing zone into the paravisceral segment of the aorta. This technique is associated with a risk of proximal Type I endoleak due to "guttering." This risk may be decreased when parallel grafts are used in combination with endovascular aneurysm sealing and, as such, this technique may represent an alternative to current techniques for the treatment of juxtarenal abdominal aortic aneurysm, such as the use of conventional bifurcated grafts (with or without parallel grafts) and fenestrated endovascular stent grafts.

Endovascular Aneurysm Sealing: Early and Midterm Results From the EVAS FORWARD Global Registry

PURPOSE

To report the early and 12-month results of a global registry of patients treated with endovascular aneurysm sealing (EVAS) for abdominal aortic aneurysms (AAAs).

METHODS

The EVAS FORWARD Global Registry was a postmarket, multicenter, open-label, single-arm registry that enrolled 277 patients (mean age 75 years; 228 men) treated with the Nellix EVAS system for nonruptured AAAs at 18 sites over a 1-year period. The cohort had challenging aortic anatomy, with 17% having a proximal aortic neck length <10 mm, 8% a neck angulation >60°, and 20% an iliac diameter >25 mm. Baseline and follow-up computed tomography images were assessed by an independent core laboratory, and major adverse events were reviewed by an independent safety committee.

RESULTS

Three patients died within 30 days of the procedure (none device-related). There were 13 endoleaks recorded in this time frame: 8 type Ia, 1 type Ib, and 5 type II. Root cause analysis demonstrated that the majority of type Ia endoleaks were due to technical error (low device placement and underfilling of the endobags). Between 30 days and 1 year, there were 4 new type Ia endoleaks; all were treated. There was also 1 type III endoleak between a Nellix device and a distal extension limb. At 1 year, the persistent endoleak rate was 0.7% (1 type Ia and 1 type II). The Kaplan-Meier estimates of freedom from types I and II endoleak at 12-month follow-up were 96% and 98%, respectively. The estimate of freedom from open conversion (n=7) was 98% at 12 months and the rate of freedom from any reintervention was 92%. The need for secondary intervention was associated with aortic morphology; for patients meeting the requirements of the instructions for use (IFU), the freedom from reintervention at 12 months was 98% compared with 86% when the implant was outside the IFU (p=0.009). At 1 year, the estimates of freedom from aortic-related and all-cause mortality were 98% and 95%, respectively.

CONCLUSION

The EVAS FORWARD Global Registry documents the 12-month outcome of EVAS in an unselected group of patients with challenging aortic morphology. The results at present appear acceptable with regard to perioperative outcomes and complications. The type II endoleak rate is low. The place of EVAS in the armamentarium of techniques to treat AAAs will be defined by durability data in the longer term.

Comparison of outcomes after endovascular and open repair of abdominal aortic aneurysms in low-risk patients

Background

In randomized trials endovascular aortic aneurysm repair (EVAR) has been shown to have superior perioperative outcomes compared with open aneurysm repair (OAR). However, outcomes in patients at low risk of complications are unclear and many surgeons still prefer OAR in this cohort. The objective was to analyse perioperative and longer-term outcomes of OAR and EVAR in this low-risk group of patients.

Methods

All elective infrarenal EVARs and OARs in the Vascular Study Group of New England database were reviewed from 2003 to 2014. The Medicare scoring system was used to identity patients at low risk of perioperative complications and death. Perioperative and longer-term outcomes were analysed in this cohort. A Kaplan–Meier plot was constructed for evaluation of longer-term survival. Further propensity matching and multivariable analysis were performed to analyse additional differences between the two groups.

Results

Some 1070 patients who underwent EVAR and 476 who had OAR were identified. Mean(s.d.) age was 67·3(5·7) and 65·1(6·3) years respectively (P &lt; 0·001). EVAR was associated with a lower overall perioperative complication rate (4·2 versus 26·5 per cent; P &lt; 0·001). There was no difference in 30-day mortality (0·4 versus 0·6 per cent; P = 0·446). Overall survival at 3 years was similar after EVAR and OAR (92·5 versus 92·1 per cent respectively; P = 0·592). In multivariable analyses there was no difference in freedom from reintervention (odds ratio 1·69, 95 per cent c.i. 0·73 to 3·90; P = 0·220) or survival (hazard ratio 0·85, 0·61 to 1·20; P = 0·353).

Conclusion

In patients predicted to be at low risk of perioperative death following aneurysm repair, EVAR resulted in fewer perioperative complications than OAR. However, perioperative mortality, reinterventions and survival rates in the longer term appeared similar between endovascular and open repair.

Total Occlusion of Abdominal Aortic Endograft Successfully Treated with Axillobifemoral Bypass

We report a case of total occlusion of a Zenith bifurcated stent graft 16 months after implantation. A 72-year-old man was admitted to our hospital complaining of bilateral lower extremity numbness, followed by severe rest pain 4 h after sudden onset of symptoms. Computed tomography showed total occlusion of the endograft at the mid-portion of the main body. He underwent left axillobifemoral bypass using a reinforced polytetrafluoroethylene T-shaped graft, leading to resolution of symptoms 7 h after onset. Axillobifemoral bypass successfully relieved acute lower extremity ischemia caused by total occlusion of the abdominal aortic endograft.

Postoperative CT Evaluation After EVAR

Purpose: To compare the postoperative computed tomography angiography (CTA) assessment made by vascular surgeons and interventional radiologists after endovascular aneurysm repair (EVAR) at a tertiary vascular clinic to an outside core review facility. Methods: One hundred patients (mean age 78.7 years, range 88–55; 84 men) with consecutive, elective, routine CTA controls after EVAR were retrospectively studied. Consultant vascular surgeons or radiologists had evaluated all original scans and written the original report. All scans were then reevaluated by an independent core clinic. Findings were classified as vascular or extravascular and stratified as clinically significant or clinically nonsignificant by an independent external reviewer. Results: The number of vascular findings detected by the vascular clinic was 72 vs 69 by the core clinic. The vascular clinic reported more clinically significant findings (primarily stent compression or kinks) as well as endoleaks and their origin. The core clinic reported more pseudoaneurysms (24 vs 12). None of the patients with puncture complications needed reintervention. Interrater analysis of all findings between the 2 clinics showed good agreement when comparing endoleaks overall (without subclassification) and moderate agreement when assessing aneurysm growth. The core clinic reported extravascular findings in 58 patients; 37 of these were classified as clinically significant. The vascular clinic reported extravascular findings in 23 patients; 7 of these were clinically significant. The core clinic also reported 2 cases of suspected malignancies, which had not been reported by the vascular clinic. Conclusion: During routine CTA follow-up after EVAR, a significant number of vascular and nonvascular findings are detected. Whereas a highly dedicated vascular clinic identifies most vascular findings regardless of the specialty of the reader, some extravascular findings are missed. However, the frequency of clinically significant findings or findings that might warrant reintervention was low in this study.

Aneurysm Sac Enlargement after Endovascular Abdominal Aortic Aneurysm Repair

The aim of this study is to give an overview of current knowledge regarding abdominal aortic aneurysm (AAA) growth after endovascular aortic aneurysm repair (EVAR) that could potentially lead to aortic rupture. A search on Pubmed was performed. A total of 705 articles were found after initial search, of which 49 were included in the final selection. Reports on the incidence of aneurysm enlargement after EVAR vary between 0.2% and 41%. Continuous growth could lead to rupture of the aneurysm sac. There are several supposed risk factors for growth after EVAR. Endoleaks remain a hot topic as these could lead to persistent pressurization of the aneurysm sac causing growth. Various types of endoleak exist, of which each kind requires an individual treatment approach, other risk factors for aneurysm growth include endotension and the use of EVAR outside instructions for use (IFU). Reinterventions after EVAR are common; however, it is unclear how frequently these are required because of aneurysm enlargement. Aneurysm enlargement after EVAR remains a subject of debate, as this could lead to aortic rupture. This emphasizes the need for life-long radiologic surveillance during follow-up. Aortic growth after EVAR is often a result of endoleak; however, in some cases, no endoleak is detectable. Endoleak in combination with aortic growth >5 mm generally requires reintervention. A cause of concern is the liberal use of endovascular devices outside the IFU that may result in increased risk of AAA growth after EVAR.