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. Author manuscript; available in PMC: 2023 Aug 1.
Published in final edited form as: J Vasc Surg. 2022 Jan 29;76(2):454–460. doi: 10.1016/j.jvs.2022.01.079

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

EA Andraska 1, AR Phillips 1, KM Reitz 2, S Asaadi 1, Y Dai 3, E Tzeng 1, MS Makaroun 1, NL Liang 1
PMCID: PMC9329192  NIHMSID: NIHMS1775860  PMID: 35093463

Abstract

Background:

Abdominal aortic aneurysm (AAA) shrinkage after endovascular repair (EVAR) is a surrogate marker for successful exclusion. Our study characterized aneurysm sac remodeling following 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 or computer tomographic angiogram (CTA) imaging were compared to the baseline diameter from the one-month postoperative CTA. The primary outcome was a composite of freedom from post-operative reintervention or rupture. We compared those with AAA sacs that regressed to pre-defined minimum diameter thresholds to those who did not. Outcomes were plotted with Kaplan-Meier curves and compared using log rank testing and Fine-Gray regression utilizing 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:

540 patients (age 75.1±8.2yrs, 82.0% male) underwent EVAR with an average preoperative AAA size of 55.2±11.5mm. Median postoperative follow-up was 5.3 years (IQR 1.4, 8.7 years) during which 64 patients underwent reintervention and 4 ruptured. AAA sac regression to ≤40mm in diameter was associated with improved freedom from reintervention or rupture overall (log rank p<0.01) which was maintained after controlling for the competing risk of death (p<0.01). In 376 patients (70%) whose aneurysm sac remained > 40mm, 99 reinterventions were performed on 63 patients. Of 166 (31%) patients whose sac regressed to ≤40mm, only one patient required a reintervention, and no one ruptured. The mean time to a diameter of ≤40mm was 2.3±1.9 years. Only eight patients (5%) developed sac re-expansion to >45mm; all but two occurred at least three years after initially regressing to ≤40mm.

Conclusions:

In long-term follow-up, patients whose minimum AAA sac diameter regressed ≤40mm following EVAR experienced a very low rate of reintervention, rupture, or sac re-expansion. Most sac re-expansion occurred at least three 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 40mm would carry minimal risk of aneurysm-related morbidity.

Keywords: Abdominal aortic aneurysm, endovascular aneurysm repair, follow-up surveillance, reintervention, rupture

Table of Contents Summary:

This retrospective study of 540 patients captured all post-operative surveillance imaging and outcomes after elective EVAR. Aneurysm sac regression to at least 40mm during the follow-up period was associated with a significantly reduced rate of reintervention or rupture. In patients whose aneurysm sac reach this threshold during follow-up, surveillance intervals can be safely increased.

Introduction

Current practice guidelines recommend lifelong surveillance after infrarenal endovascular aortic aneurysm repair (EVAR) because of the ongoing risk of developing post-operative endoleaks, endograft material fatigue, or late rupture.1,2 In the most recent Society of Vascular Surgery (SVS) guidelines, annual imaging is recommended after EVAR regardless of the presence of endoleak or sac expansion.1 However, the burden of frequent follow-up can be prohibitive and includes surveillance costs, risk of kidney injury, radiation induced malignancy and increased nonadherence to follow-up over time.3

The intensive surveillance regimen following EVAR was initially guided by regulatory requirements during the early development of endografts and persisted with the recognition of frequent failures of first-generation and subsequent endografts. Ongoing AAA degeneration and endograft complications in the early EVAR experience was noted to require reinterventions in up to 19% of patients with a 5% risk of late rupture.8 This initiated a culture of frequent surveillance with high cost imaging techniques. Computed tomography angiogram (CTA) imaging was the mainstay of endograft surveillance and was recommended as often as three times during the first year and yearly thereafter. However, these early CTAs have not been shown to provide any additional clinical utility if the one month post-operative scan does not show evidence of endoleak.4 More recently, duplex ultrasonography has gained acceptance as a safe method for surveillance, potentially leading to significant cost savings without the risks associated with radiation and intravenous contrast.5–7 Follow-up schedules should preferentially identify high risk patients while reducing the burden for the majority who remain stable over time.

In recent European guidelines, less frequent surveillance is suggested for low risk patients, however neither specific time intervals nor risk factors were included.2 There is a paucity of knowledge to inform these decisions and to identify these specific low risk patients who may be safely followed with extended intervals between imaging. In this study, we examined long-term AAA sac behavior following EVAR to address this knowledge gap. We hypothesize that we can identify a subset of patients who could safely qualify for lower frequency follow-up.

Methods

Patient Population

All patients who underwent elective EVAR at the University of Pittsburgh Medical Center, a multi-hospital healthcare system, from 2008 to 2011 were included. These years were included in order to optimize follow-up and capture up to 10 years of follow-up imaging and appointments for each patient in the study. Patient electronic medical records (EMR) were reviewed to capture patient factors including age, gender, smoking status, statin use, and graft type. This study was approved by the University of Pittsburgh’s Human Research Protection Office (STUDY20080199).

Follow-up Imaging Studies

All follow-up CTA and ultrasound studies were reviewed for each patient. Major and minor axis measurements were recorded for each CTA. Measurements were determined by choosing the CTA axial slice with the largest aortic sac diameter and measuring axial diameters. Axis measurements were from the outer edges of the sac. Axial imaging was chosen as not all scans were able to be reconstructed via multiplanar reformatting methods. The authors used a standard institutional method of measurement for axial slices, measuring the minor axis perpendicular to the estimated line of flow to account for the orthogonal measurements as best as possible. This approximates the measurement which would be obtained by an oblique multiplanar reformat when reconstruction is not technically possible. Diameter measurements from ultrasound imaging performed by a registered vascular technologist were abstracted from the EMR. The institutional vascular laboratory protocol utilizes the maximum anterior-posterior measurement perpendicular to the line of flow in the infrarenal aorta as the primary measurement. Follow-up sac measurements of the minor axis were compared to baseline measurements obtained from the one-month post-operative CTA. A patient was defined as having primarily ultrasound surveillance if ultrasound studies contributed to >50% of all imaging studies obtained. Primarily CT surveillance was defined as CT studies contributing to >50% of all imaging studies obtained. All studies that were completed and able to be read were captured and recorded as follow-up imaging, with none excluded. If the aneurysm could not be adequately visualized in either study due to patient movement or artifact, the surveillance study was not included.

Patients were grouped by the minimum sac diameter that was reached during the follow-up period. The groups were broken down by 5 mm size increments: a minimum diameter of ≤40mm, 41-45mm, 46-50mm, 51-55mm, >55mm. The patient stayed in the coded group regardless of sac changes after the minimum diameter was reached.

Outcomes

The primary outcome of interest was a composite of freedom from reintervention or rupture. The group with aneurysm sac size associated with the lowest rate of the composite outcome was chosen for further analysis. Comparisons were made between those who regressed to this sac diameter threshold and those who did not. This group was compared against all other groups for further evaluation of the primary composite outcome. To evaluate changes after reaching the minimum threshold, a landmark analysis was performed. In this analysis, the time the patient reached the minimum sac diameter was redesignated as time zero. Further sac changes, including sac re-expansion, as well as reinterventions were then evaluated.

Statistical analysis

Data were analyzed with STATA version 16 (StataCorp LP, College Station, Texas). Continuous variables are reported as mean ± standard deviation or median (interquartile range) and were compared using Student’s T-tests for parametric variables and Mann-Whitney U tests for non-parametric variables. Categorical variables are presented as frequency (%). Chi-squared testing was used unless frequency (expected <5) required Fisher’s exact testing.

Outcomes were plotted with Kaplan-Meier (KM) curves comparing reintervention or rupture using log rank testing. Fine-Gray regression was used to control for the competing risk of mortality.

Sensitivity analyses

Several sensitivity analyses were performed on this patient population. First, to capture repairs indicated only for sac size, patients with a baseline sac diameter of <50mm were excluded from analysis. Second, alterative definitions of aortic sac size measurements and sac regression categorization were evaluated including the proportional and absolute change in sac diameters. Proportional changes were categorized into ¼ or ½ of the baseline diameter and an absolute regression of 10, 20, and 30mm. Rate of regression at six months and one year were also analyzed for sac shrinkage of 10, 20, and 30mm. KM analysis was performed for all sensitivity analyses in a similar fashion to the primary analysis.

Results

Five-hundred and forty patients underwent EVAR between 2008 and 2011. The average age at the time of operation was 75.1±8.2 years. Most patients were male (82.0%) and had a history of smoking (86.1%) (Table I). The endografts used in this patient population reflected our typical usage during that period and are detailed in Table I. Most patients had a Gore Excluder (344 patients, 63.7%), while 10.7% had the Medtronic Endurant (58 patients) and the Cook Zenith (58 patients). The average baseline minor axis measurement was 55.2±11.5mm. Median follow-up was 5.3 years (IQR 1.4, 8.7 years). Five patients in the cohort were not seen in follow-up. The one-year follow-up rate was 83.3% and the five-year follow-up rate was 52.2%.

Table I.

Patient demographics and operative details for total patient population.

Sac diameter ≤40mm 166 patients N (%) Sac diameter >40mm 374 patients N (%) All Patients 540 patients N (%) p-value
Age, years (SD)a) 76.4 (8.1) 72.4 (7.9) 75.1 (8.2) <0.01
Male 136 (81.9) 307 (82.1) 443 (82.0) 0.85
History of smoking 142 (85.5) 323 (86.4) 465 (86.1) 0.80
Current statin use 112 (67.5) 206 (55.1) 318 (58.9) 0.07
Graft used 0.75
Gore Excluder 103 (62.1) 241 (64.4) 344 (63.7)
Medtronic Endurant 18 (10.8) 40 (10.7) 58 (10.7)
Cook Zenith 20 (12.1) 38 (10.2) 58 (10.7)
Endologix AFX 2 (1.2) 10 (2.7) 12 (2.2)
Other 23 (13.9) 45 (12.03) 68 (12.6)
Baseline average sac diameter (SD, mm) 54.7 (12.3) 57.6 (13.9) 55.2 (11.5) 0.10
Median follow-up (IQRb, years) 4.8 (1.1, 8.0) 6.1 (1.7, 9.3) 5.3 (1.4, 8.7) 0.01
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a

(SD) indicates continuous variables with summary measure of mean (standard deviation) and P value from Student t-test. Categorical variables are summarized by N (%), and P values are calculated from the X2 test.

b

(IQR) indicates continuous variables with summary measure of median (interquartile range) and P value from Student t-test. mm, millimeter.

A size threshold of 40mm was chosen as the best size measurement for analysis and the best surrogate for stable exclusion of the AAA for analysis. This size threshold was chosen from multiple sensitivity analyses evaluating other size thresholds, which are described later.

Approximately one third of patients reached a minimum post-operative sac diameter of ≤40mm (166 patients, 30.7%) during follow-up. Another third did not shrink below 55 mm (163 patients, 30.2%). The remaining patients reached minimum sac diameters as follows: 41-45mm (67 patients, 12.4%), 46-50mm (64 patients, 11.9%), 51-55mm (80 patients, 14.8%; Figure 1). The rate of endoleak present on initial scan in patients with sac regression to at least 40mm was 10.2%. The rate of endoleak on initial scan in patients without sac regression to 40mm was 23.8%. In 34.7% of patients who did not have an initial endoleak experienced sac regression to ≤40mm, whereas only 13.6% of patients who did have an endoleak on initial scan experienced sac regression to ≤40mm. Controlling for age, gender, and type of graft, patients that had an absence of endoleak on initial scan had a higher odds of sac regression to ≤40mm (OR 3.4, 95% CI 1.9-6.2, p = 0.01).

Figure 1.

Figure 1.

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Diagram demonstrating the patient population. The first comparisons were made with sample populations divided by minimum aneurysm diameter during follow-up. Final comparisons were made between patients who reached at least 40mm minimum diameter during follow-up and those who did not.

mm, millimeter.

Most patients in both groups had primarily ultrasound surveillance. 12.1% of patients in the ≤40mm group had more CT surveillance than ultrasound surveillance whereas 21.4% of patients in the >40mm group had more CT surveillance than ultrasound.

In total, 100 reinterventions including diagnostic angiograms were performed on 64 (11.9%) patients during the period of follow-up: 39 procedures involved coil embolization and 37 a proximal or distal graft extension. There were four ruptures (0.7%), 3 of whom were lost to follow-up and ruptured at least five years post-operatively. One of these patients had a rapidly expanding Type 1b endoleak one-year post-EVAR. Twenty-two patients required an open abdominal intervention (18 elective open conversion and 4 ruptures). Of note, there was no significant difference in reintervention or rupture rate across graft type (p = 0.24). Additionally, the distribution of graft type was similar between those that regressed to ≤40mm and those that did not. These details are displayed in Table I.

KM curves plotting the freedom from reintervention or rupture by minimum sac diameter reached during follow-up is displayed in Figure 2. There was a single reintervention and no ruptures in the 166 patients who reached a minimum sac diameter of ≤40mm (0.6%). This singular reintervention was a distal extension of the right limb in a patient with an expanding iliac aneurysm eight years post-EVAR. While the iliac artery degenerated, this patient did not have evidence of a Type Ib endoleak and the aortic sac diameter remained less than 40mm from the one-year to the most recent nine-year post-EVAR follow-up. Reintervention or rupture was noted in 11 of 67 patients (16.4%) who reached 41-45mm diameter, 15 of 64 (23.4%) who reached 46-50mm, 14 of 80 (17.5%) who reached 51-55mm and 25 of 163 (15.3%) who remained >55mm. All ruptures occurred in patients with minimum sac diameter >40mm, and two were in patients with a minimum sac diameter >55mm.

Figure 2.

Figure 2.

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Kaplan Meier curves displaying freedom from reintervention or rupture in entire population.

mm, millimeter.

Compared to patients who did not reach a size of 40mm or less, those who did had significantly improved freedom from reintervention or rupture overall (log rank p < 0.01; Figure 3) and after controlling for the competing risk of death, clustered by graft type (p < 0.01). The mean time to reaching 40mm was 2.3±1.9 years. After reaching 40mm, aneurysm sacs either continued to regress (<35mm, 48%) or remained stable (35-45mm, 47%; Figure 4). Only eight patients (5%) re-expanded to >45mm. Six of these eight occurred at least three years after reaching a size ≤40mm. None of these eight patients required a reintervention and none have re-expanded beyond 55mm on latest follow-up. Most of these patients (5/8) had stable, asymptomatic Type II endoleaks identified on follow-up imaging that were left untreated. The remaining three patients did not have an identifiable endoleak on follow-up imaging.

Figure 3.

Figure 3.

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Freedom from reintervention or rupture in patients reaching 40mm during follow-up.

mm, millimeter.

Figure 4.

Figure 4.

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Landmark analysis of patients who reached 40mm during follow-up.

Data points represent average aneurysm sac size at each time point measured from the associated post-operative follow-up. Bars represent the range of aneurysm sac sizes measured at the post-operative follow-up. mm, millimeter.

Sensitivity analyses

A sensitivity analysis was performed which excluded patients whose aneurysm sac was less than 50mm on the minor axis at baseline (124 patients, 23%). In this new cohort, 95 (23%) patients reached a diameter of ≤40mm and none of the patients in this group required reintervention or ruptured in the follow-up period. In fact, a follow-up diameter of ≤40mm remained a significant predictor of improved freedom from reintervention or rupture (p < 0.01).

A second sensitivity analysis evaluated other aneurysm measurements and sac regression categorization. Instead of a strict size threshold, proportional sac regression was investigated. Patients whose aneurysm sacs regressed by half of their baseline measurements did have significant freedom from reintervention or rupture (p<0.01). However, only 11 patients experienced this pronounced sac shrinkage and thus the generalizability of this association is limited. There were 143 (26%) patients whose aneurysm sacs regressed by 25%; however, there were 6 reinterventions in this group with most reinterventions for expanding aneurysm sacs due to Type II endoleaks.

Absolute decrease in sac size by 10, 20, and 30mm were investigated. Two hundred forty-three (45%) patients had a decrease in sac diameter of at least 10mm during their follow-up. However, this amount of reduction was not associated with improved freedom from reintervention or rupture (p = 0.37). Rate of 10mm sac regression of less than six months or one year also did not change rate of freedom from reintervention or rupture (six months p = 0.59, one year p = 0.56). An absolute sac shrinkage of 20mm was not associated with freedom from reintervention or rupture (131 patients, p = 0.20) however, a rapid decrease of 20mm within six months post-EVAR was associated with a lower rate of reintervention or rupture (p = 0.03). Only thirty patients out of the 540-patient cohort reached this rapid shrinkage threshold, making a subgroup analysis and generalizability difficult. The effect on outcome was no longer significant if the rate of 20mm shrinkage was extended to one-year post-EVAR (p = 0.07). An absolute decrease in sac size by 30mm was investigated and did not result in a decrease in reintervention or rupture (76 patients, p = 0.18). However, a rate of sac shrinkage of 30mm at both six months and one year were associated with improved freedom from reintervention (six months p < 0.01, one year p = 0.02). However, similar to the 20mm group, there were only 24 and 28 patients in these cohorts, making subgroup analysis and generalizability difficult. Given these findings, an absolute threshold of aneurysm sac shrinkage to a size ≤40mm was most predictive of successful AAA exclusion and stable sac behavior over time.

Discussion

We report long term surveillance data on a large cohort of patients who underwent EVAR at a multi-hospital, single institution. Significant sac shrinkage to ≤40mm diameter during follow-up occurred in over 30% of the patients. This group demonstrated very stable aneurysm exclusion for long periods with only a single patient requiring a reintervention and no patients ruptured. This single reintervention was to treat a degenerating iliac artery while the aneurysm sac continued to regress. Of the eight patients whose sac re-expanded, none grew past 55mm or required reintervention. Most of these re-expansions occurred at least three years after reaching 40mm. These findings suggest that, in patients whose aneurysm sacs regress to at least 40mm during follow-up, it is safe to increase the follow-up interval up to three years instead of the annual surveillance recommended by current guidelines. In patients whose aneurysms do not shrink to at least 40mm, continued annual surveillance is still recommended.

Our data showed an overall reintervention rate of 12% with a post-operative rupture rate of <1% after EVAR, similar to findings from other single and multi-institution reports.9–11 In a retrospective review of EVAR surveillance comparing octogenarians to younger patients, Visser et al show that octogenarians with lower rates of reinterventions (8.2% vs. 19.8%) and question the need for frequent surveillance on older patients.12 Others have been advocating for the adjustment of post-EVAR surveillance protocols. In a review of 32 papers evaluating EVAR surveillance, Nordon et al reported that >90% of EVAR cases received no clinical benefit from surveillance imaging. They concluded that surveillance imaging should be targeted at high risk stent-grafts and populations.13 Similar studies question the utility of frequent post-operative surveillance due to high resource utilization with low clinical utility.14,15 The rationale for such follow up is the fear of device failure and rupture.

Certain characteristics may assist the clinician in identifying high risk populations for frequent surveillance imaging. Rajendran et al reported that aneurysms that ruptured following EVAR had a larger initial diameter (average 7.4cm) and suggested more strict surveillance for larger aneurysms.10 Similarly, in a recent study by Mohapatra et al evaluating open conversions of prior EVARs at a single institution found that open conversions for endoleak occurred after the sac reached on average 7.4cm.16 Late ruptures after EVAR were noted to occur patients with a mean aortic diameter of 6.1cm prior to EVAR,17 suggesting that patients with larger AAAs represent a higher risk population. Tailoring surveillance to the individual’s risk characteristics seems most advantageous for both the healthcare system and the patients, however data is still lacking regarding specific surveillance parameters that confer reduced risk.

Aneurysm shrinkage has consistently been a predictor of improved outcomes in EVAR. In a review of eight studies, Antoniou et al describe improved rates of post-operative death, secondary interventions, late complications, and rupture in patients who demonstrated sac shrinkage after EVAR.18 Similarly, our group has described a low risk of adverse outcomes in patients with stable or shrinking aneurysm sacs.5 It is therefore not surprising that our cohort of patients with smaller aneurysms sacs on follow-up had lower rates of reintervention or rupture. As there is evidence of better outcomes with significant aneurysm shrinkage, longer follow-up intervals in this subset of patients are a safe and acceptable alternative to the current practice of annual surveillance.

An annual surveillance program risks loss of compliance and undue risk to the patient. In a systematic review of 11 cohort studies involving 21,838 patients, de Mik et al found that compliant patients underwent more reinterventions, but mortality was not affected by compliance with surveillance. They concluded that yearly imaging surveillance may not benefit all EVAR patients.19 In a prospectively collected single center database, AbuRahma et al found that only 43% of EVAR patients were compliant with follow-up surveillance but there was no difference in endoleak detection or reintervention rates between compliant and noncompliant groups.20 Likewise, a single institution review of post-EVAR surveillance by Wu et al revealed that compliance with surveillance did not translate to improved survival.21 In a review by Spanos et al, compliance was reported to be about 50% with no evidence to suggest that poor compliance results in worse outcomes.22 In a retrospective study evaluating Medicare claims, nonadherence to the Society for Vascular Surgery guidelines for post-EVAR imaging was not associated with poor outcomes and suggested that less frequent surveillance is not necessarily associated with worse outcomes.23 These data highlight that surveillance schedules are not optimized and are potentially unduly burdensome to the patient.

Unnecessary follow-up can result in excessive risk to the patient. Repeated CTAs expose patients to many risks including the carcinogenic risk associated with exposure to ionizing radiation and renal injury from iodinated contrast.24 Long term post-operative surveillance has also been reported to increase the cost of EVAR by 50%.25 This, along with the logistics of physically travelling to appointments in a typically elderly population, sometimes with limited support mechanisms and dependent on family support, accumulates a significant burden to the patient and family over time. Increased use of ultrasound surveillance and virtual follow-up appointments can reduce the burden follow-up imposes on patients. These follow-up techniques should be optimized in low-risk patients, such as those who experience sac regression to at least 40mm.

In our analysis, once the aneurysm sac regressed to at least 40mm, aneurysm sacs remained stable over a long period of time. In a secondary analysis of the Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA3CT) trial, Olson et al showed that even small untreated aneurysms (<4.25cm) showed linear growth with no patients reaching repair thresholds at 2 years and suggested that increasing surveillance intervals in this patient population to every 2 years would be safe.26 It is thus very plausible that aneurysm sacs with significant regression following EVAR would be suitable for an even longer follow-up interval.

This study was retrospective which limits which data could be collected. We are unable to capture specifics of physician decision making regarding aneurysm sac changes and imaging reports. However, the retrospective nature of this study allows us to objectively comment on trends with aneurysm sac changes. A prospective study capturing the natural history of sac changes after EVAR would further elucidate these trends. To address this, we included a sensitivity analysis which shows that even after excluding patients with a baseline minor axis of <50mm, aneurysm sac regression to 40mm remained an important predictor of stable aneurysm behavior over time. Additionally, we are limited in external validity. Although this study includes multiple hospitals, patients were treated within a single institution which may limit the generalizability of our findings. While we identified and included over 500 patients in our study, only 166 sacs regressed to 40mm with only one re-intervention. Larger sample sizes may be helpful in identifying other anatomic features that may require frequent surveillance. The median follow-up in this study was 5.3 years. While study inclusion dates included EVARs performed between 2008-2011 to optimize follow-up, many patients were still lost to follow-up. This represents a limitation in capturing outcomes and interventions.

Finally, our recommendations may be limited by patient factors. Indeed, it may be difficult to extend follow-up intervals to every three years instead of annually simply for patient adherence concerns. However, depending on the institution, EMR systems allow for follow-ups to be booked far in advance or for patients to be placed on a recall list for follow-up appointments. Cohen et al outlined a surveillance program that centers on a protocolized system of contacting patients via mail or telephone for follow-up reminders.27 Protocols such as these are already in existence for patients with open repair who require a follow-up imaging every five years and can be adapted to EVAR follow-up. Regardless, extending follow-up intervals for low-risk patients would certainly reduce unnecessary health care resource utilization. In the present study’s cohort of 540 patients, changing surveillance follow-up post-EVAR from annually to every three years in patients who reached an aneurysm sac diameter of 40mm would have saved 664 office visits, 498 ultrasound studies, and 166 CTAs without missing any ruptures or sac expansion that would require a reintervention.

Conclusions

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

Article Highlights:

Type of Research:

Multihospital single institution retrospective cohort study

Key Findings:

After EVAR, 31% of patients experienced sac regression to ≤40mm during follow-up surveillance. This threshold was associated with a significantly reduced risk of reintervention or rupture (p<0.01) and 95% of aneurysm sacs continued to regress further or remained stable.

Take Home Message:

Aneurysms that shrink to at least 40mm are at low risk for reintervention or rupture. EVAR surveillance guidelines can be safely adjusted to allow longer follow-up intervals for these low-risk patients.

Funding sources:

This research was supported in part by grant 5T32HL0098036 form the National Heart, Lung, and Blood Institute (Andraska, Phillips, Reitz) and L30 AG064730 from the National Institute on Aging (Reitz). The University of Pittsburgh holds a Physician-Scientist Institutional Award from the Burroughs Wellcome Fund (Andraska).

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This work was presented as a plenary presentation at the 2021 SVS Vascular Annual Meeting in San Diego, CA, August 19, 2021

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