What is the clinical utility of a 6-month computed tomography in the follow-up of endovascular aneurysm repair patients?

CIRSE Standards of Practice on Management of Endoleaks Following Endovascular Aneurysm Repair

BACKGROUND

Endoleaks represent the most common complication after EVAR. Some types are associated with ongoing risk of aneurysm rupture and necessitate long-term surveillance and secondary interventions.

PURPOSE

This document, as with all CIRSE Standards of Practice documents, will recommend a reasonable approach to best practices of managing endoleaks. This will include imaging diagnosis, surveillance, indications for intervention, endovascular treatments and their outcomes. Our purpose is to provide recommendations based on up-to-date evidence, updating the guidelines previously published on this topic in 2013.

METHODS

The writing group was established by the CIRSE Standards of Practice Committee and consisted of clinicians with internationally recognised expertise in endoleak management. The writing group reviewed the existing literature performing a pragmatic evidence search using PubMed to select publications in English and relating to human subjects up to 2023. The final recommendations were formulated through consensus.

RESULTS

Endoleaks may compromise durability of the aortic repair, and long-term imaging surveillance is necessary for early detection and correct classification to guide potential re-intervention. The majority of endoleaks that require treatment can be managed using endovascular techniques. This Standards of Practice document provides up-to-date recommendations for the safe management of endoleaks.

2022 ACC/AHA guideline for the diagnosis and management of aortic disease: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Brazilian Society for Angiology and Vascular Surgery guidelines on abdominal aortic aneurysm

The Brazilian Society of Angiology and Vascular Surgery, through the Guidelines Project, presents new Abdominal Aortic Aneurysm Guidelines, on the subject of care for abdominal aortic aneurysm patients. Its development prioritized descriptive guidelines, using the EMBASE, LILACS, and PubMed databases. References include randomized controlled trials, systematic reviews, meta-analyses, and cohort studies. Quality of evidence was evaluated by a pair of coordinators, aided by the RoB 2 Cochrane tool and the Newcastle Ottawa Scale forms. The subjects include juxtarenal aneurysms, infected aneurysms, and new therapeutic techniques, especially endovascular procedures. The current version of the guidelines include important recommendations for the primary topics involving diagnosis, treatment, and follow-up for abdominal aortic aneurysm patients, providing an objective guide for medical practice, based on scientific evidence and widely available throughout Brazil.

Infrarenal Abdominal Aortic Aneurysm

Abdominal aortic aneurysms are found in up to 6% of men and 1.7% of women over the age of 65 years and are usually asymptomatic. The natural history of aortic aneurysms is continued dilation leading to rupture, which is associated with an overall 80% mortality. Of the patients with ruptured aneurysms that undergo intervention, half will not survive their hospitalization. Reduction in aneurysm mortality is therefore achieved by prophylactic repair during the asymptomatic period. On a population-based level, this is supported by abdominal aortic aneurysm screening programs. Approximately 60% of abdominal aortic aneurysms are confined to the infrarenal portion of the aorta and are amenable to repair with off-the-shelf endovascular devices. Endovascular techniques have now replaced open surgery as the primary modality for aneurysm repair.

Change in Abdominal Aortic Aneurysm Sac Diameter After Endovascular Repair: A Single-Center Experience From Taiwan

PURPOSE

The purpose of this study was to investigate the change in the diameter of infrarenal abdominal aortic aneurysm (AAA) sacs after endovascular aortic repair (EVAR) in Taiwanese patients and to depict its association with clinical outcomes.

MATERIALS AND METHODS

This retrospective cohort study was conducted on patients who underwent EVAR for infrarenal AAA between January 2011 and December 2016. All preoperative and follow-up computed tomography (CT) images were reviewed. Postoperative CT angiography was arranged after 1 month and annually thereafter. The maximal diameter on the axial plane and the maximal diameter perpendicular to the centerline on the coronal and sagittal planes were measured. The study examined post-EVAR sac diameter change over time and compared the differences in adverse events (AEs) among groups.

RESULTS

The survey included a total of 191 patients with a median follow-up duration of 2.5 (interquartile range: 1.1-2.9) years. Overall survival rates at 1, 2, and 5 years were 92%, 81%, and 76%, respectively. According to their last CT scans, the patients were categorized into 3 groups as follows: shrinkage, stationary, and enlargement, which comprised 58 (30.4%), 118 (61.8%), and 15 (7.9%) patients, respectively. Pre-EVAR characteristics and sac diameters were similar among the groups. Sac shrinkage was exclusively observed in the first 2 years, whereas sac enlargement developed at all follow-up periods. Patients with sac enlargement had higher incidence rates of endoleaks, complications, and reintervention than the other groups.

CONCLUSION

Based on our observations, post-EVAR sac shrinkage only occurs in the first 2 years; however, post-EVAR sacs may enlarge at any point and even after 5 years. In our study, patients with sac enlargement had higher rates of adverse events and reintervention.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate. Structure: Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Longer follow-up intervals following EVAR are safe and appropriate after marked aneurysm sac regression

BACKGROUND

Abdominal aortic aneurysm (AAA) shrinkage after endovascular aortic aneurysm repair (EVAR) is a surrogate marker for successful exclusion. Our study characterized aneurysm sac remodeling after EVAR to identify a pattern that may be associated with benign AAA behavior and would safely allow a less rigorous follow-up regimen after EVAR.

METHODS

Elective infrarenal EVARs performed between 2008 and 2011 at our institution were retrospectively reviewed. AAA sac diameters using the minor axis measurement from ultrasound imaging or computer tomography angiogram imaging were compared with the baseline diameter from the 1-month postoperative computer tomography angiogram. The primary outcome was a composite of freedom from postoperative reintervention or rupture. We compared those with AAA sacs who regressed to predefined minimum diameter thresholds with those who did not. Outcomes were plotted with Kaplan-Meier curves and compared using log-rank testing and Fine-Gray regression using death as a competing risk, clustered on graft type. For patients whose AAA reached the minimum sac diameter, landmark analysis evaluated ongoing size changes including further regression and sac re-expansion.

RESULTS

A total of 540 patients (aged 75.1 ± 8.2 years; 82.0% male) underwent EVAR with an average preoperative AAA size of 55.2 ± 11.5 mm. The median postoperative follow-up was 5.3 years (interquartile range, 1.4-8.7 years) during which 64 patients underwent reintervention and 4 ruptured. AAA sac regression to ≤40 mm in diameter was associated with improved freedom from reintervention or rupture overall (log-rank, P < .01), which was maintained after controlling for the competing risk of death (P < .01). In 376 patients (70%) whose aneurysm sac remained >40 mm, 99 reinterventions were performed on 63 patients. Of 166 (31%) patients whose sac regressed to ≤40 mm, only 1 patient required a reintervention, and no one ruptured. The mean time to a diameter of ≤40 mm was 2.3 ± 1.9 years. Only eight patients (5%) developed sac re-expansion to >45 mm; all but two occurred at least 3 years after initially regressing to ≤40 mm.

CONCLUSIONS

In long-term follow-up, patients whose minimum AAA sac diameter regressed ≤40 mm after EVAR experienced a very low rate of reintervention, rupture, or sac re-expansion. Most sac re-expansion occurred at least 3 years after reaching this threshold and did not result in clinical events. Increasing follow-up frequency up to 3-year intervals once the AAA sac regresses to 40 mm would carry minimal risk of aneurysm-related morbidity.

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.

Diseases of the Aorta and Kidney Disease: Conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Chronic kidney disease (CKD) is an independent risk factor for the development of abdominal aortic aneurysm (AAA), as well as for cardiovascular and renal events and all-cause mortality following surgery for AAA or thoracic aortic dissection. In addition, the incidence of acute kidney injury (AKI) after any aortic surgery is particularly high, and this AKI per se is independently associated with future cardiovascular events and mortality. On the other hand, both development of AKI after surgery and the long-term evolution of kidney function differ significantly depending on the type of AAA intervention (open surgery vs. the various subtypes of endovascular repair). Current knowledge regarding AAA in the general population may not be always applicable to CKD patients, as they have a high prevalence of co-morbid conditions and an elevated risk for periprocedural complications. This summary of a Kidney Disease: Improving Global Outcomes Controversies Conference group discussion reviews the epidemiology, pathophysiology, diagnosis, and treatment of Diseases of the Aorta in CKD and identifies knowledge gaps, areas of controversy, and priorities for future research.

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.

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.

The Society for Vascular Surgery practice guidelines on follow-up after vascular surgery arterial procedures

Although follow-up after open surgical and endovascular procedures is generally regarded as an important part of the care provided by vascular surgeons, there are no detailed or comprehensive guidelines that specify the optimal approaches with regard to testing methods, indications for reintervention, and follow-up intervals. To provide guidance to the vascular surgeon, the Clinical Practice Council of the Society for Vascular Surgery appointed an expert panel and a methodologist to review the current clinical evidence and to develop recommendations for follow-up after vascular surgery procedures. For those procedures for which high-quality evidence was not available, recommendations were based on observational studies, committee consensus, and indirect evidence. Recognizing that there are numerous published reports on the role of duplex ultrasound for surveillance of infrainguinal vein bypass grafts, the Society commissioned a systematic review and meta-analysis on this topic. The panel classified the strength of each recommendation and the corresponding quality of evidence on the basis of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: recommendations were graded either strong or weak, and the quality of evidence was graded high, moderate, or low. The resulting recommendations represent a wide variety of open surgical and endovascular procedures involving the extracranial carotid artery, thoracic and abdominal aorta, mesenteric and renal arteries, and lower extremity arterial revascularization. The panel also identified many areas in which there was a lack of high-quality evidence to support their recommendations. This suggests that there are opportunities for further clinical research on testing methods, threshold criteria, and the role of surveillance as well as on the modes of failure and indications for reintervention after vascular surgery procedures.

Surgical Versus Endovascular Aortic Aneurysm Repair: Evidence to Guide the Optimal Approach for the Individual Patient

The choice between an open surgical and an endovascular approach for abdominal aortic aneurysm (AAA) repair remains an individualized clinical decision. As the technology and applications of endovascular aortic aneurysm repair (EVAR) continue to evolve, so does the literature investigating its outcomes. Multiple high-quality, randomized controlled trials comparing EVAR to open surgical repair (OSR) have now been published with long-term follow-up. Experience with ruptured aneurysms and the use of complex endografts is growing as well. This review is an up-to-date compilation of pertinent clinical trials for practitioners placed in the context of individual patient considerations to guide the choice of an optimal approach to the management of AAAs.

A new approach for the pre-clinical optimization of a spatial configuration of bifurcated endovascular prosthesis placed in abdominal aortic aneurysms

Complexity of the spatial configuration of an aortic implant with bifurcation in the distal part is related to changes in blood hemodynamic in the area of bifurcation which may disturb blood flow and lead to thrombus formation. This study was designed to characterize parameters which define spatial configuration of an aortic implant for which the risk of thrombus formation is the smallest. We used AngioCT data from 74 patients, aged 55 ±10 years, after endovascular procedure to prepare 3D geometries of stent-grafts. Computational Fluid Dynamics (CFD) simulations were used to reconstruct blood hemodynamic and simulate thrombus formation. Next, geometric parameters of stent-grafts included the ratio of volume of upper part to the bifurcations, the relation of inlet and outlet diameters of a stent-graft and deformations in the iliac part of the stent-graft were analyzed. We also analyzed tortuosities (spiral twisting of the flow around the flow direction) and bends (the largest angulation in distal part of a stent-graft). The CFD results were confronted with AngioCT data to verify if computer generated thrombus appeared in particular patient. Additionally, geometric parameters of analyzed stent-grafts were used to propose a mathematical tool for prediction of thrombus appearance. The results showed that tortuosities and bends of a stent-graft had the highest impact on thrombus formation. Formation of thrombi was observed in 22% to 31% of cases (at blood hematocrit Hct = 40%) even for small values of tortuosities and bends indicating that these parameters are dominant in determining blood clotting. Our calculated results overlapped with clinical data in 80% to 91%. Therefore, we conclude that tortuosities and bends have high impact on thrombus formation and should be under special attention during stent-graft recommendation and patients’ follow-ups.

Could Preoperative Neck Anatomy Influence Follow-up of EVAR?

BACKGROUND

The aim of the study was to assess the clinical utility of strict CT scan surveillance after endovascular abdominal aneurysm repair (EVAR) and evaluate whether the anatomy of abdominal aortic aneurysm (AAA) neck (favorable/hostile) influences regular imaging control.

METHODS

A retrospective study of AAA patients who underwent EVAR with aortobi-iliac endoprostheses during 2006-2013 was conducted. Exclusion criteria included other types of devices. Variables analyzed were technical and clinical success, morbimortality, complications (such as endoleaks, sac enlargement), reinterventions, reintervention-free survival, and survival rate. Preoperative CT scans were performed and repeated at 1, 6 (in selective cases), 12, and 24 months postoperatively. Patients were divided into two groups according to preoperative anatomic characteristics: group I (favorable neck) and group II (hostile neck: angle > 60°, length < 15 mm, diameter > 28 mm, and calcification or circumference thrombus ≥50%).

RESULTS

A total of 127 patients with AAA (96.8% male) were included in the study. The mean age of the patients was 75.9 years (range: 51-90 years). The mean AAA diameter was 62.1 mm. Hostile neck was found in 52 patients (40.9%). The technical and clinical success rate was 100% and 30-day mortality was 0.8%. The reintervention-free survival rate was 97.6%, 96.1%, and 93.7% and the survival rate was 97.6%, 96.9%, and 91.3%, during follow-up at 6, 12, and 24 months, respectively. Accumulated complications in proximal sealing occurred in 0%, 0%, and 1.6% in group I and 1.9%, 6.1%, and 7.7% in group II at 1, 12, and 24 months, respectively. Type II endoleaks occurred in 24.3%, 14.3%, and 11.4% in group I and 9.8%, 6.3%, and 6.8% in group II at 1, 12, and 24 months, respectively. No increased diameter was detected at 6 and 12 months. No differences were observed in reinterventions and mortality rate depending on anatomy.

CONCLUSIONS

CT scans performed at 6 and 12 months postoperatively did not detect complications or need for reintervention in patients with favorable necks, even in the presence of endoleaks type II, and could therefore be omitted. Hostile necks may compromise proximal sealing and require regular imaging follow-ups.

An anatomic risk model to screen post endovascular aneurysm repair patients for aneurysm sac enlargement

BACKGROUND

Follow-up computed tomography angiography (CTA) scans add considerable postimplantation costs to endovascular aneurysm repairs (EVARs) of abdominal aortic aneurysms (AAAs). By building a risk model, we hope to identify patients at low risk for aneurysm sac enlargement to minimize unnecessary CTAs.

METHODS

895 consecutive patients who underwent EVAR for AAA were reviewed, of which 556 met inclusion criteria. A Probit model was created for aneurysm sac enlargement, with preoperative aneurysm morphology, patient demographics, and operative details as variables.

RESULTS

Our final model included 287 patients and had a sensitivity of 100%, a specificity of 68.9%, and an accuracy of 70.4%. Ninety-nine (35%) of patients were assigned to the high-risk group, whereas 188 (65%) of patients were assigned to the low-risk group. Notably, regarding anatomic variables, our model reported that age, pulmonary comorbidities, aortic neck diameter, iliac artery length, and aneurysms were independent predictors of post-EVAR sac enlargement. With the exception of age, all statistically significant variables were qualitatively supported by prior literature. With regards to secondary outcomes, the high-risk group had significantly higher proportions of AAA-related deaths (5.1% versus 1.1%, P = 0.037) and Type 1 endoleaks (9.1% versus 3.2%, P = 0.033).

CONCLUSIONS

Our model is a decent predictor of patients at low risk for post AAA EVAR aneurysm sac enlargement and associated complications. With additional validation and refinement, it could be applied to practices to cut down on the overall need for postimplantation CTA.

A multi-institutional survey of interventional radiology for type II endoleaks after endovascular aortic repair: questionnaire results from the Japanese Society of Endoluminal Metallic Stents and Grafts in Japan

PURPOSE

To investigate the current status of interventional radiology (IR) procedures for a type II endoleak (T2EL) in Japan, and to identify the technical aspects that affect treatment results.

MATERIALS AND METHODS

A retrospective survey was conducted by distributing questionnaires to 25 institutions. The eligibility criteria were endovascular aortic repair (EVAR) performed using commercial stent grafts and IR performed for T2EL between January 2007 and December 2013. Technical success was defined as disappearance of the EL on digital subtraction angiography immediately after embolization, and imaging success was defined as no EL on contrast-enhanced computed tomography within 6 months. Statistical comparisons of the number of involved branches, embolization level, embolic material, and changes in aneurysm size were made between the imaging success and imaging failure groups. The technical and imaging success rates were also compared between the initial therapy and repeat groups.

RESULTS

A total of 166 cases were investigated. Initial therapy was performed in 147 cases (88.6 %), with repeat therapy in 19 cases (11.4 %). Transcatheter arterial embolization (TAE) was used most frequently, in 161 cases (97 %), with direct puncture (DP) used in 5 cases (3 %). Both coil embolization for the branches and NBCA embolization for the sac were frequently chosen. The technical success rate was 83.2 % (TAE group), and the imaging success rate was 46.5 % (TAE + DP groups). Branch + sac embolization was performed more frequently in the imaging success group. There was no significant difference in the number of involved branches or embolic material between the imaging success and imaging failure groups. Enlargement of the aneurysm was more frequently seen in the imaging failure group. There were no significant differences in the technical success and imaging success rates between the initial therapy and repeat groups.

CONCLUSION

This is the first report of a multi-institutional questionnaire survey of IR procedures for T2EL after EVAR in Japan that was conducted to determine the current status. Enlargement of aneurysm size after embolization was more frequently seen in the imaging failure group. It is important to embolize both branch and sac to achieve imaging success, regardless of embolic material. Long-term outcomes need to be investigated.

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.

A 3D model of thrombus formation in a stent-graft after implantation in the abdominal aorta

Here we present a 3D kinetic model of thrombus formation in an endovascular prosthesis after implantation in an abdominal aorta with an aneurysm. The computational fluid dynamic technique (CFD) was used to determine the process of thrombus formation and growth in the stent-graft on the basis of the medical data from computed tomography angiography and Doppler ultrasound examination of 10 patients. The Quemada model was used to describe rheological properties of blood. Results of the CFD simulations were validated based on actual data from patients with diagnosed thrombi in aortic implants. The results show that the elaborated CFD model correctly predicted thrombus formation, shape and deposition site in an endovascular prosthesis. The developed CFD model of thrombus growth can be applied to predict the risk of thrombus formation in stent-grafts and assist in selection of geometry of the endovascular prosthesis to reduce possible complications after stent-graft implantation using only basic medical data.

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.

Clinical implications of non-contrast-enhanced computed tomography for follow-up after endovascular abdominal aortic aneurysm repair

BACKGROUND

There is growing concern over the long-term radiation exposure from serial computed tomographic (CT) scan follow-up after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs). Screening for endoleaks with non-contrast-enhanced volumetric CT has been shown to significantly reduce radiation doses. We evaluated the use of NCT as the primary method of follow-up after EVAR of AAAs.

METHODS

Our institutional post-EVAR CT protocol consisted of contrast-enhanced CT angiography (CTA) 1 month after repair, followed by NCT at 3 or 6 and 12 months, and annually thereafter. At each follow-up scan, immediate 3-dimensional volume analysis was performed. If the volume change was <2%, NCT follow-up was continued. If the volume increased by ≥2% on nonenhanced images, contrast-enhanced CT was performed immediately to identify potential endoleaks. All images were reviewed by an experienced cardiovascular radiologist. End points included identification of endoleak, reintervention, and rupture.

RESULTS

Over a 7-year period, 126 patients were followed. Serial CTA was performed in 59 patients, while 67 patients were followed with the NCT protocol. The mean follow-up was 2.07 years. There were no differences in age, sex, or initial aneurysm volume or size. There were 35 total endoleaks identified. Twenty of these were early endoleaks (<30 days post-EVAR). The remaining 15 leaks were late in nature (10 in the contrast group and 5 in the noncontrast group; P=0.17). NCT aneurysm sac volume changes prompted contrasted studies in all 5 late leaks. The mean volume change was 11.2 cm3, an average change of 5.88%. These findings were not significantly different than the late leaks found by routine contrast studies (8.9 cm3; 4.98% [P=0.58]). There were no delayed ruptures or emergent reinterventions in the NCT group.

CONCLUSIONS

Serial NCT appears to be safe and effective as the sole means of follow-up after EVAR for AAAs. AAA volume increases of ≥2% should prompt further contrast-enhanced CT imaging. Changes of <2% can be safely followed with serial NCT. This protocol requires dedicated cardiovascular radiologist involvement, and patients should be retained in the radiology suite until real-time image evaluation can be completed.

The impact of radiation dose exposure during endovascular aneurysm repair on patient safety

OBJECTIVE

Endovascular aneurysm repair (EVAR) exposes patients to radiation during the procedure and in subsequent follow-up. The study goal was to calculate the radiation dose in our unit and compare it against other published data and national guidelines.

METHODS

All EVAR procedures were identified from a prospectively maintained database. Radiation dose, screening time, and volume of intravenous contrast during the procedure were reviewed. Radiation exposure from subsequent computed tomography (CT) imaging was included in the overall exposure. Results are expressed as mean +/- standard deviation.

RESULTS

From October 1998 to October 2008, 320 elective patients underwent EVAR. Mean screening time was 29.4 +/- 23.3 minutes, and the radiation dose was 11.7 +/- 7.1 mSv. The EVAR was an emergency in 64 patients. The mean screening time was 22.9 +/- 18.2 minutes, and the radiation dose was 13.4 +/- 8.6 mSv. During the first postoperative year, follow-up CT scans exposed the patients to 24.0 mSv, with 8.0 mSv in subsequent years. Abdominal radiographs added an additional 1.8 mSv each year.

CONCLUSION

EVAR and the follow-up investigations involve substantial amounts of radiation, with well-recognized carcinogenic risks. Because patient safety is paramount, radiation exposure should be minimized. This may be possible by standardizing radiation exposure throughout the United Kingdom by implementing national guidelines and considering other imaging modalities for follow-up.

The value of the initial post-EVAR computed tomography angiography scan in predicting future secondary procedures using the Powerlink stent graft

OBJECTIVE

Current long-term surveillance after endovascular abdominal aortic aneurysm repair (EVAR) is based on high-resolution contrast-enhanced computed tomography (CT) scans at scheduled, lifelong intervals. The cancer and nephrotoxicity risks of interval CT scanning and prolonged radiation exposure are concerning. We sought to determine if surveillance CT angiography (CTA) can be safely reduced.

METHODS

From July 2000 to November 2007, 345 patients were enrolled in U.S. Food and Drug Administration trials of the Powerlink System (Endologix, Irvine, Calif). An independent core laboratory analyzed 1519 post-EVAR CT scans (N=1519) to 5 years to evaluate aneurysm size, migration, presence of endoleak, and evidence of graft obstruction. Analyses were conducted to determine the value of the initial CTA scan in predicting future secondary procedures in enrolled patients.

RESULTS

At any time during follow-up, CTA identified endoleak in 123 patients (36%), with 95% of endoleaks being type II. In addition, 49 patients underwent 72 secondary procedures at a mean of 22±21 months (range, 2-2007 days) after initial EVAR. These were based on clinical identification of limb ischemia in 13 interventions (18%) or core laboratory identification of abnormal CT finding in 58 interventions (81%). Of the 58 core laboratory identified findings, the inciting abnormality was present on the initial postoperative scan in 49 (84%). Of the remaining nine CT-driven procedures, three (5.2%) were due to late sac expansion attributed to type II endoleak (n=2) or endotension (n=1); two (3.4%) were for prophylactic reasons in the absence of endoleak; and four (6.8%) were in patients with type II endoleak not observed by the core laboratory and without sac expansion. The negative predictive value of the initial postoperative CTA for the need for a secondary procedure is therefore 96.4%, which can be improved to 97.6% with duplex ultrasound surveillance to detect sac expansion. Thus, a negative initial postoperative CTA is highly predictive of long-term freedom from secondary intervention.

CONCLUSIONS

Among enrolled patients with suitable anatomy for EVAR, most abnormalities that result in a secondary procedure are detected on the initial postoperative CTA or present with clinical symptoms. Long-term surveillance CTA may therefore be replaced by duplex ultrasound imaging if the initial postoperative CTA shows no abnormalities.

Durability of endovascular infrarenal aneurysm repair: when does late failure occur and why?

The first commercially available stent grafts were unable to withstand the hemodynamic forces of the vascular environment. The past 15 years have seen a gradual improvement in long-term stent graft performance as designs evolved through the elimination of features associated with late failure and the replication of features associated with durable success. Clinical experience provides the following principles on which to base device design and implantation techniques. Few patients have an adequate length of non-dilated aorta distal to the aneurysm to allow implantation of an aorto-aortic stent graft; bifurcated stent grafts are usually required for AAA repair. Friction, column strength and tissue ingrowth do not prevent migration of the stent graft from its attachment within the neck into the aneurysm; some form of active fixation is required, usually in the form of barbs. Any movement between the apex of a stent and the overlying graft material will erode the fabric; stents and grafts need to move as a single unit. Nitinol is versatile, but fragile; Nitinol components must be polished to eliminate all surface irregularities and they cannot be subjected to compression loading, or excessive pulsatile movement. The neck of an aneurysm is unstable; it will dilate unless protected by a securely fixed, non-compliant stent graft. The aneurysm does not heal; freedom from risk of rupture depends on durable depressurization of the sac. The sole objective of image-based follow-up is the early detection, and catheter-based correction, of device failure. Once any given design has been in use long enough to identify its failure modes, the frequency of follow-up studies can be adjusted accordingly. However, it takes a long time to identify all the potential forms of late failure, and pre-clinical testing remains an imprecise science. New, or recently modified, devices cannot necessarily be assumed to be as durable as their predecessors.

Imaging in endovascular therapy: our future

The endovascular therapist now has many modern imaging techniques available to plan and execute treatment, whereas in the past vascular surgeons relied mostly on clinical examination and arteriography. Advances in computer technology have enabled fast acquisition and processing of the large amounts of digital data essential to capture the dynamic information from fast-flowing blood at high resolution. Functional imaging has begun to play a role in predicting stability of progressive vascular disease and the need for and risks of intervention. Computing power now affords the interventionist the ability to handle imaging data in powerful 3-dimensional programs and electronically "in-lay" a variety of devices to plan complex endovascular procedures from the familiar platform of a laptop. In four major clinical areas, carotid intervention, peripheral intervention, endoluminal grafting, and cardiac imaging, we review the latest advances and changes with an eye toward how we should best be using imaging in our patients undergoing endovascular treatment...now and into the future.

Late Type III endoleak and graft failure of an Ancure stent-graft

The authors report a case of a delayed type IIIb endoleak with sac expansion 6 years after an endovascular repair of an abdominal aortic aneurysm with an Ancure bifurcated stent-graft. The presumed etiology of the leak was secondary to erosion of the main body graft material by metal stents placed within the graft to correct kinking of the iliac limbs at the index operation. The endoleak was successfully treated by endovascular means with an aortouni-iliac device, contralateral iliac plug followed by a femoral-to-femoral bypass graft.