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Version 1. F1000Res. 2017; 6: 1549.
Published online 2017 August 23. doi:  10.12688/f1000research.11860.1
PMCID: PMC5580406

A primer on infrarenal abdominal aortic aneurysms

Norman R Hertzer, Conceptualization, Writing – Original Draft Preparation, Writing – Review & Editinga,1

Abstract

Ruptured abdominal aortic aneurysms have an alarmingly high mortality rate that often exceeds 50%, even when patients survive long enough to be transported to hospitals. Historical data have shown that ruptures are especially likely to occur with aneurysms measuring ≥6 cm in diameter, but there are so many exceptions to this that several randomized clinical trials have been done in an attempt to determine whether smaller aneurysms should be repaired electively as soon as they are discovered. More recently, further trials have been conducted in order to compare the relative benefits and disadvantages of modern endovascular aneurysm repair to those of traditional open surgery. This review summarizes current evidence from randomized trials and large population-based datasets regarding two questions that are uppermost in the mind of virtually every patient who is found to have an abdominal aortic aneurysm. Should it be fixed? What are the risks?

Keywords: abdominal aortic aneurysm, endovascular repair, rupture, open repair

Introduction

Non-septic abdominal aortic aneurysms (AAAs) are caused by weakening and fragmentation of the internal elastic membrane and loss of smooth muscle cells in the medial layer of the aortic wall, accompanied by inflammatory processes in the medial and adventitial layers, leading to enlargement that may worsen over time. The majority of AAAs involve the nearly branchless infrarenal segment of the aorta below the level of the renal arteries ( Figure 1a) and represent the focus of virtually all of the data reported in this review. The most life-threatening yet insidious complication of an AAA is acute rupture, which may be preceded by local tenderness or pain in the back, the flank, or the abdomen but not uncommonly occurs without any warning symptoms whatsoever.

Figure 1.

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Object name is f1000research-6-12816-g0000.jpg
Images of infrarenal abdominal aortic aneurysms.

( a) Autopsy specimen showing the relationship of an intact infrarenal aneurysm to the renal arteries. ( b) Operative photograph during transabdominal open repair with a knitted bifurcation graft. ( c) Three-dimensional computed tomogram after transfemoral endovascular repair in another patient.

Spontaneous rupture of an AAA is a catastrophic medical emergency, typically accompanied by massive blood loss and hemodynamic instability. From 2005–2012, 51,475 deaths in the United States and another 39,740 in the United Kingdom were caused by AAAs 1. During the same study period, however, only 35,922 patients in the U.S. and 17,253 in the UK were formally admitted to hospitals with a diagnosis of ruptured AAAs. This implies that about one-third of patients with ruptured AAAs in the U.S. and over half of those in the UK died either without reaching an emergency room or soon after their arrival.

Even when patients are able to undergo urgent intervention for ruptured AAAs, their chances of surviving the event are not good. Although it appears to have improved during each of the past five decades, the pooled operative mortality rate for ruptured AAA repair in 21,523 patients was 48% (95% confidence interval [CI] 46 to 50%) in a meta-analysis of 171 articles published on this topic from 1955–1998 2. Furthermore, the risk still exceeded 50% in a population-based study of 35,637 patients who received either open or endovascular repair for ruptured AAAs in the U.S. and the UK from 2005–2010 3. Women, who generally are older and tend to present with larger AAAs relative to their normal aortic diameter than men, are more likely to rupture at a slightly smaller AAA size and have a higher operative mortality rate than men when they do rupture 4.

Prevalence

According to a community-based study using ultrasound scanning below the level of the superior mesenteric artery in a total of 15,792 participants with a median follow-up period of 22.5 years, it has been estimated that the lifetime risk of developing an AAA measuring ≥3.0 cm in diameter is 5.6% (95% CI 4.8 to 6.1%) at the age of 45 5. The prevalence was higher at ages 55 to 64 than at ages 45 to 54 (6% versus 3.2%), in men than in women (8.2% versus 3.2%), and in current smokers (10%) than in either former smokers (6.3%) or non-smokers (2.0%). However, the incidence of rupture or elective intervention was only 1.6%, suggesting that many of the smaller AAAs never enlarged to a size considered dangerous from a clinical standpoint. Ultrasound screening studies primarily targeting men aged 65 to 75 in the U.S. and the UK have found that only 13 to 17% of detected AAAs were 4.5 to 5.4 cm in diameter and just 4.1 to 12% were ≥5.5 cm 6, 7.

Treatment options

Dubost performed the first open repair of an AAA in 1951 8 using a thoracoabdominal incision and an aortic homograft. The development of synthetic replacement grafts ( Figure 1b) allowed open repair to be widely adopted, with a steady reduction in the mortality rate for elective AAA repair at referral centers from about 7% in 1963–1980 to 4% in 1981–1990 and to 2% in 1991–2000 9. Population-based studies have shown that operative mortality tends to be inversely related to the annual volume of open AAA repairs performed by individual surgeons. In the state of New York, for example, surgeons doing the highest volume had better mortality rates than those with the lowest volume in 1985–1987 (5.6% versus 11%) 10 and in 2000–2011 (3.6% versus 6.4%) 11. Another study of 5,972 open repairs in the U.S. Nationwide Inpatient Sample from 2003–2007 also found that high-volume surgeons had better mortality rates than either medium-volume or low-volume surgeons (3.0% versus 4.3% versus 7.5%, respectively, p<0.0001) irrespective of hospital volumes 12.

Parodi and associates first reported (in English) a transfemoral technique for endovascular aneurysm repair (EVAR) in 1991 13. Working independently, Volodos first published an article (in Russian) describing transfemoral repair of a thoracic aortic aneurysm using a similar handmade endograft in 1988 14. Conceived as an option for patients at severe risk for open repair, the wide availability of commercial endografts and surgeons trained to use them has now made EVAR ( Figure 1c) an appealing alternative for average-risk patients. The current preference for EVAR is reflected by two large studies that comprised nearly 200,000 patients and found that EVAR was performed for 74% of all non-ruptured AAA repairs in the U.S. in 2010 15 and for 61% of those in Australia, Iceland, New Zealand, and eight European countries in 2009 16. In fact, the proportion of U.S. hospitals where at least 25% of elective AAA repairs involved open surgery declined from 41% in 2007 to only 18% in 2011 ( p<0.001) 17.

Aneurysm size

Szilagyi demonstrated 50 years ago that patients whose AAAs measured >6 cm in diameter by physical examination had a much higher 5-year survival rate after open repair than when placed under observation alone (49% versus 17%) 18 and that AAA ruptures caused a larger proportion of deaths than myocardial infarctions (42% versus 31%) in patients who were deemed to be medically unfit for open repair 19. In a recent meta-analysis of 1,514 unfit patients reported in 11 previous articles, the pooled annual rupture rate was estimated to be 3.5% for AAAs that were 5.5 to 6.0 cm in diameter, 4.1% for those that were 6.1 to 7.0 cm, and 6.3% for those that were >7.0 cm 20. Urgent repair was offered to only 54 (32%) of the 171 patients whose AAAs ruptured, and their operative mortality rate was 58%.

Given the longstanding consensus that large AAAs should be repaired electively in appropriate candidates, four randomized trials have been done to establish whether early intervention might be beneficial in patients with smaller AAAs. Ultrasound surveillance to detect AAA expansion was compared to open repair in the UK Small Aneurysm Trial (UKSAT) 2123 and the Aneurysm Detection and Management trial (ADAM) 24 and later was compared to EVAR in the Comparison of surveillance versus Aortic Endografting for Small Aneurysm Repair trial (CAESAR) 25 and the Positive Impact of endoVascular Options for Treating Aneurysms earLy trial (PIVOTAL) 26. The demographics, 30-day mortality rates, and late results of the trials are summarized in Table 1. Women collectively represented only 10% of the participants in these trials, with especially few women in the Veterans Affairs ADAM trial. The 30-day mortality rates with early intervention ranged from 0.6% in the two trials using EVAR to 2.1% for open repair in ADAM and 5.8% in UKSAT. Except for a marginally significant survival benefit for early open repair at a mean of 8 years of follow-up in UKSAT, the all-cause mortality rates for early intervention or surveillance were comparable in each of the trials. All of them concluded that close observation with periodic ultrasound scanning was as safe as either open repair or EVAR as long as the AAA was <5.5 cm in diameter (<5.0 cm in PIVOTAL).

Table 1.

Intention-to-treat analysis of early intervention versus ultrasound surveillance for small abdominal aortic aneurysms in the randomized UKSAT 2123, ADAM 24, CAESAR 25, and PIVOTAL 26 trials.
Treatment strategyOpen repair versus surveillanceEndovascular repair versus
surveillance
TrialUKSATADAMCAESARPIVOTAL
Randomized
patients
1,0901,136360728
Men9021,127345631
Women188 (17%)9 (0.8%)15 (4.2%)97 (13%)
Mean age (years)69 ± 468 ± 668.9 ± 6.870.5 ± 7.8
Aneurysm diameter
Protocol diameter4.0–5.5 cm4.0–5.5 cm4.1–5.4 cm4.0–5.0 cm
Actual mean
diameter
4.6 ± 0.4 cm4.7 ± 0.4 cm4.7 ± 0.3 cm4.5 ± 0.3 cm
Early intervention563
(517 *)
569
(380 *)
182
(175 *)
366
(326 *)
Surveillance527
(489 *)
567
(516 *)
178
(172 *)
362
(350 *)
30-day mortality
rate for early
intervention
5.8%2.1%
(2.7% in-hospital)
0.6%0.6%
Follow-up periodRange 3–7
years
Mean 4.6 years
Range 6–10
years
Mean 8 years
12 yearsRange 3.5–8
years
Mean 4.9 years
Median 32.4
months (early
intervention)
Median
30.9 months
(surveillance)
Range 0–41
months
Mean 20 ± 12
months
Survival rate
Early intervention64%53%36%75%86%96%
Surveillance64%45%
p=0.03
33%78%90%96%
Rupture rate while
under surveillance
1.0% annually3.2% annually4.4% crude0.6% annually1.1% crude0.6% crude
MenNROdds ratio, 1.0
(reference set)
NRNRNRNR
WomenNROdds ratio, 4.0
(2.0–7.9)
p<0.001
NRNRNRNR
Eventual repair
Intervention cohort520
(92%)
520
(92%)
528
(94%)
527
(93%)
175
(96%)
315
(86%)
Surveillance cohort321
(61%)
327
(62%)
401
(76%)
349
(62%)
85
(48%)
112
(31%)
Surveillance
outcome by
aneurysm diameter
Survival rate4.0–4.4 cm: 75%
4.5–4.8 cm: 73%
4.9–5.5 cm: 64%
4.0–4.4 cm: 56%
4.5–4.8 cm: 54%
4.9–5.5 cm: 43%
4.0–4.4 cm: 38%
4.5–4.8 cm: 35%
4.9–5.5 cm: 26%
4.0–4.4 cm: 84%
4.5–4.9 cm: 82%
5.0–5.4 cm: 69%
NRNR

*Patients who actually received early treatment or surveillance

ADAM, Aneurysm Detection and Management trial; CAESAR, Comparison of Surveillance versus Aortic Endografting for Small Aneurysm Repair trial; NR, not reported; PIVOTAL, Positive Impact of endoVascular Options for Treating Aneurysms earLy trial; UKSAT, United Kingdom Small Aneurysm Trial.

Two additional findings from these trials are worth mentioning. First, there was a greater risk for rupture in the 93 women than in the 434 men in the surveillance cohort of UKSAT, the only trial having a representative number of women. By a mean of 8 years, fatal ruptures caused 12 (14%) of the 85 deaths in women versus 19 (4.6%, p<0.001) of the 411 deaths in men. The incidence of either fatal or non-fatal ruptures also was higher among women (hazard ratio 4.0, 95% CI 2.0 to 7.9, p<0.001). Second, a substantial number of patients in the surveillance cohorts of all four trials eventually underwent open repair or EVAR ( Figure 2). In addition to rupture, the reasons included the onset of back pain or abdominal tenderness, patient preference, and, probably most commonly, either rapid expansion on consecutive ultrasound scans or enlargement to a size that exceeded the maximum permitted by the trial protocol. Late intervention rates correlated directly with baseline AAA diameters in ADAM, CAESAR, and PIVOTAL.

Figure 2.

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Eventual repair rates for abdominal aortic aneurysms in the surveillance cohorts of the UKSAT 23, ADAM 24, CAESAR 25, and PIVOTAL 26 trials.

The reasons for the eventual repairs included rupture, the onset of back pain or local tenderness, rapid growth on consecutive ultrasound scans or enlargement to a size exceeding the trial protocol, and patient preference. ADAM, Aneurysm Detection and Management trial; CAESAR, Comparison of surveillance versus Aortic Endografting for Small Aneurysm Repair trial; PIVOTAL, Positive Impact of endoVascular Options for Treating Aneurysms earLy trial; UKSAT, United Kingdom Small Aneurysm Trial.

Elective EVAR versus open repair

The advantages and liabilities of open repair and EVAR were reasonably well recognized, even before the results of most randomized trials were reported 8. Open repair had a higher procedural mortality rate but few late graft-related complications and a negligible risk for late AAA rupture. Conversely, EVAR had a low early mortality rate but a higher incidence of secondary endograft-related interventions, the majority being done to treat endoleaks that had continued to pressurize the aneurysm sac at endograft fixation points (type I), from retrograde flow in lumbar arteries or the inferior mesenteric artery (type II), or through endograft modular separations or fabric tears (type III). Since each might potentially cause sac expansion and eventual rupture, manufacturers have routinely recommended annual computed tomography (CT) scans to detect such problems. In an attempt to avoid the expense and radiation exposure of repeated CT scanning, however, a growing consensus among surgeons now appears to favor long-term ultrasound surveillance for patients whose initial post-EVAR CT scans show no evidence of endograft complications 27.

According to manufacturers’ Instructions for Use (IFU), the anatomic criteria for conventional transfemoral EVAR generally include 1) a “neck” of non-aneurysmal aorta distal to the renal arteries measuring ≥15 mm in length and <28 mm in diameter, 2) neck angulation of <60° from the center line between the lowest renal artery and the aortic bifurcation, and 3) an iliac artery diameter ranging from 8–20 mm 28. In 2011, an analysis of 1,063 pre-EVAR CT scans found that women were less likely than men to satisfy IFU with respect to neck length (37% versus 53%), neck angulation (74% versus 88%), and iliac diameter (42% versus 64%), with only 12% of women and 32% of men meeting all three criteria 29. This does not mean that EVAR cannot be adapted to many of the remaining patients, but the incidence of subsequent AAA sac expansion is higher when IFU are not followed 28. Anatomic EVAR limitations are particularly relevant in women, who have a greater overall risk for procedural iliac artery injuries 30 and late endograft limb occlusions 31.

Against this background, four major, non-industry sponsored randomized trials were conducted from 1999–2009 to compare the results of elective open repair and EVAR in patients who were medically and anatomically suitable for either procedure, including the EVAR-1 trial 3234, the Dutch Randomized Endovascular Aneurysm Management trial (DREAM) 3538, the Open Versus Endovascular Repair trial (OVER) 3943, and the Anevrysme de l’aorte abdominale: Chirurgie versus Endoprothese trial (ACE) 44. Two demographic features of these trials were different from the earlier small aneurysm trials: only 5.6% of the patients were women and the AAAs were larger, with mean diameters ranging from 5.5 cm in ACE to as much as 6.5 cm in EVAR-1. Additional demographics, the procedural risks, and long-term outcomes in the EVAR trials are presented in Table 2.

Table 2.

Intention-to-treat analysis of open versus endovascular repair for non-ruptured abdominal aortic aneurysms in the randomized EVAR-1 3234, DREAM 3537, OVER 3940, and ACE 44 trials.
TrialEVAR-1DREAMOVERACE
OpenEVAROpenEVAROpenEVAROpenEVAR
Patients
randomized
1,252351881299
Treatment
allocated
626
(602 *)
626
(614 *)
178
(169 *)
173
(170 *)
437
(416 *)
444
(427 *)
149
(135 *)
150
(163 *)
Men570565161161435441146150
Women566117122630
Mean age74.0 ± 6.174.0 ± 6.169.6 ± 6.870.7 ± 6.670.5 ± 7.869.6 ± 7.870 ± 7.170 ± 7.7
Aneurysm
diameter
Protocol
diameter
≥5.5 cm≥5.0 cm≥5.0 cm>5.0 cm in men
>4.5 cm in women
Actual mean
diameter
6.5 ± 1.0 cm6.4 ± 0.9 cm6.0 ± 0.8 cm6.1 ± 0.9 cm5.7 ± 1.0 cm5.7 ± 0.8 cm5.6 ± 0.7 cm5.5 ± 0.8 cm
Early
outcome
30-day
mortality
rate
4.3%1.8%
OR 0.39
(0.18–0.87)
p=0.02
4.6% * 1.2% *
p=0.10
2.3%0.2%
p=0.006
0.6%1.3%
In-hospital
mortality rate
6.0%2.3%
OR 0.39
(0.20–0.76)
p=0.006
NRNR3.0%0.5%
p=0.004
NRNR
Median
hospital
length of stay
12 days7 days
p<0.0001
NRNR7 days3 days
p<0.001
10 days6 days
p<0.0001
Follow-up
period
Mean 12.7 ± 1.5 yearsMedian 6.4 yearsMean 5.2 yearsMean 2.5 ± 1.2 years
Median 3 years
All-cause
mortality rate
42%
(8 years)
71%
(15 years)
42%
(8 years)
74%
(15 years)
10%
(2 years)
34%
(6 years)
10%
(2 years)
34%
(6 years)
9.8%
(2 years)
33%
(8 years)
7.0%
(2 years)
33%
(8 years)
3.5%
(1 year)
13%
(3 years)
4.8%
(1 year)
14%
(3 years)
Aneurysm-
related
mortality
6.4%
(8 years)
7.2%
(15 years)
5.8%
(8 years)
8.9%
(15 years)
5.7%
(2 years)
2.1%
(2 years)
3.0%
(2 years)
3.7%
(8 years)
1.4%
(2 years)
2.3%
(8 years)
0.6%
(3 years)
4.0%
(3 years)
Other events
Aneurysm
rupture
0.5%
(8 years)
0.8%
(15 years)
2.9%
(8 years)
5.0%
(15 years)
0
(2 years)
0
(6 years)
0
(2 years)
0.6%
(6 years)
0
(2 years)
0
(8 years)
0.9%
(2 years)
1.4%
(8 years)
0
(3 years)
2.0%
(3 years)
Secondary
intervention
1.7%
(8 years)
12%
(15 years)
5.1%
(8 years)
26%
(15 years)
HR 2.42
(1.82-3.21)
p<0.0001
18%
(6 years)
30%
(6 years)
p=0.03
13%
(2 years)
18%
(8 years)
14%
(2 years)
22%
(8 years)
2.7%
(3 years)
16%
(3 years)
p<0.0001

*Patients who actually received open or endovascular repair.

ACE, Anevrysme de l’aorte abdominale: Chirurgie versus Endoprothese trial; DREAM, Dutch Randomized Endovascular Aneurysm Management trial; EVAR, endovascular aneurysm repair; HR, hazard ratio; NR, not reported; OR, odds ratio; OVER, Veterans Affairs Open versus Endovascular Repair trial.

The two largest trials found that EVAR had a significant advantage over open repair with respect to the 30-day (1.8% versus 4.3% in EVAR-1, p=0.02; 0.2% versus 2.3% in OVER, p=0.006) and the in-hospital (2.3% versus 6.0% in EVAR-1, p=0.006; 0.5% versus 3.0% in OVER, p=0.004) mortality rates. EVAR also was associated with significantly shorter median lengths of stay in the hospital than open repair in EVAR-1 (7 versus 12 days, p<0.0001), in OVER (3 versus 7 days, p<0.001), and in ACE (6 versus 10 days, p<0.0001). The influence of the early survival benefit for EVAR on all-cause mortality rates usually lasted for about 3 years, after which other common causes of death again took precedence. Aneurysm-related mortality, which included the initial procedural deaths as well as the subsequent fatal ruptures, did not shift in favor of open repair until late in follow-up. However, the secondary intervention rates were substantially higher after EVAR than after open repair at all periods of observation in most of the trials.

A meta-analysis of pooled individual patient data adds further perspective regarding the timing of certain outcomes of interest at a median follow-up of 5.5 years for 2,783 patients in EVAR-1, DREAM, OVER, and ACE 45. As shown in Figure 3, the hazard ratios (HRs) for all-cause and aneurysm-related mortality were significantly lower among patients allocated to EVAR during the first 6 months following their randomization. There then was a gradual reversal in the HRs, which was inconsequential for all-cause mortality but eventually revealed a significantly higher aneurysm-related mortality in EVAR patients at longer than 4 years of follow-up (HR 5.30, 95% CI 1.52 to 18.46, p<0.05). Meanwhile, the HRs for secondary intervention were higher among EVAR patients even within the first month, attained statistical significance at 30 days to 3 years ( p<0.05), and peaked at longer than 3 years (HR 2.80, 95% CI 1.85 to 4.24).

Figure 3.

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Object name is f1000research-6-12816-g0002.jpg
Hazard ratios for endovascular aortic aneurysm repair versus open repair in a meta-analysis of pooled individual patient data from the EVAR-1, DREAM, OVER, and ACE trials 45.

EVAR had a survival advantage at 6 months because of a lower 30-day mortality rate, followed by a gradually higher incidence of aneurysm-related deaths or re-interventions. ACE, Anevrysme de l’aorte abdominale: Chirurgie versus Endoprothese trial; DREAM, Dutch Randomized Endovascular Aneurysm Management trial; EVAR, endovascular aneurysm repair; OVER, Open Versus Endovascular Repair trial.

The OVER trialists have reported a detailed analysis of endoleaks, 32% of which were treated by re-interventions 41. During a mean follow-up of approximately 6 years, endoleaks were identified in 30% of patients after successful EVAR, 76% of the endoleaks being classified as type II. Type II endoleaks were likely to be associated with AAA expansion when discovered later than 1 year after EVAR ( p<0.0001), though 84% of all type II endoleaks were detected earlier and 60% of them resolved spontaneously. Despite the expense of CT scan surveillance and re-interventions, OVER still found that EVAR was cost effective compared to open repair 42, 43. This was not the case in EVAR-1 33, in DREAM 38, or in Markov models derived from all four trials 46.

Finally, it must be mentioned for completeness that a second randomized trial, the EVAR-2 trial, also was conducted in the UK in order to compare EVAR to observation alone in 404 patients who had AAAs measuring ≥5.5 cm in diameter (mean 6.8 cm) but were medically unfit for open repair and thus could not be enrolled in EVAR-1 47, 48. The 30-day mortality rate for EVAR was 7.3%, and fatal ruptures occurred in 31% of the patients in the observation cohort during a median follow-up of 3.1 years. The aneurysm-related mortality was lower with EVAR (HR 0.53, 95% CI 0.32 to 0.89, p=0.02), but this was not associated with a significant benefit for EVAR in terms of all-cause mortality (HR 0.99, 95% CI 0.78 to 1.27, p=0.97). Endograft-related complications occurred in 48% of EVAR patients, 27% of whom were treated with secondary interventions during the first 6 years of surveillance. This trial concluded that EVAR did not improve long-term survival in patients having serious medical comorbidities and, of course, that it was more costly than observation.

Ruptured aneurysm repair

Few randomized trials have been done to compare open repair to EVAR in patients with ruptured AAAs, largely because it is so critically important not to delay definitive treatment. There simply might not be enough time to perform the imaging studies that are necessary to determine whether many hemodynamically unstable patients are anatomically eligible for EVAR as well as for open repair. Conceding the potential for bias in this regard, a meta-analysis of the individual data for a total of 836 patients in three randomized trials has reported pooled 30-day mortality rates of 31% in patients allocated to EVAR versus 34% in those receiving open repair 49. Early mortality rates also were closely comparable at 90 days (34% and 38%, respectively), with a modest advantage for EVAR only among the 160 women in the three trials.

Using a risk stratification system based on age >76 years, preoperative cardiac arrest or loss of consciousness, and the necessity for suprarenal aortic clamping during open procedures, a study from a large registry maintained by the Society for Vascular Surgery has attempted to clarify the relative benefits of open repair and EVAR in 1,165 patients who underwent ruptured AAA repair from 2003–2013 50. Open repair was done in 514 of these patients and EVAR in 651, with EVAR having a lower in-hospital mortality rate (25% versus 33%, p=0.001). The mortality advantage for EVAR was most evident in medium-risk patients (37% versus 48%, p=0.02) and trended towards significance in low-risk patients (10% versus 15%, p=0.07). However, EVAR was not associated with any mortality benefit in high-risk patients (95% versus 79%, p=0.17). Unfortunately, a truly all-inclusive randomized trial to resolve these issues may never be feasible.

Medicare correlations

Population-based data help to translate the findings of randomized trials into a real-world setting. Information for a total of 128,598 Medicare patients across the U.S. confirms that the proportion of elective AAA repairs performed using EVAR instead of open procedures increased from 36% in 2001 51 to 82% in 2008 52. During that time, death occurred within 30 days or during the index hospital admission in 1.6% of propensity-matched patients who had EVAR versus 5.2% of those who had open repair (relative risk for open repair 3.22, 95% CI 2.95 to 3.51, p<0.001). EVAR patients also sustained fewer medical complications and had shorter median lengths of stay (2 versus 7 days, p<0.001). Similar trends have been reported among 23,670 patients of all ages who had EVAR or open repair for non-ruptured AAAs in the state of California from 2001–2009 53.

The procedural mortality benefit with EVAR lasted for 3 years in propensity-matched cohorts, after which all-cause mortality rates for EVAR and open repair converged both at 5 years (each 34%) and at 8 years (each 55%). The rupture rate was higher at 8 years after EVAR (5.4% versus 1.4%, p<0.001), and EVAR patients also had a higher incidence of device-related re-interventions (19% versus 3.7%, p<0.001). Re-interventions for abdominal wall hernias or the lysis of intra-abdominal adhesions were more common after open repair (18% versus 8.2%, p<0.001) and so were hospital admissions for the conservative management of intestinal obstruction (22% versus 17%, p<0.001). Nevertheless, some of these were not necessarily related specifically to the previous AAA repair.

Conclusions

Readers should also be made aware that great progress is taking place at dedicated aortic centers with the use of fenestrated and branched endografts to repair aortic aneurysms extending above the renal arteries 54, 55, but EVAR already has become a valuable and widely available option for appropriate infrarenal AAAs. Size is the primary factor determining whether any intervention is necessary. Provided there are no compelling medical contraindications, early elective treatment is preferred for AAAs that are ≥5.5 cm in diameter and may deserve consideration for slightly smaller AAAs in young, otherwise-healthy patients, particularly in women. EVAR has distinct short-term advantages in eligible candidates, but it requires lifelong surveillance, has a higher aneurysm-related re-intervention rate, and is associated with a low but measurable risk for late rupture.

Abbreviations

AAA, abdominal aortic aneurysm; ACE, Anevrysme de l’aorte abdominale: Chirurgie versus Endoprothese trial; ADAM, Aneurysm Detection and Management trial; CAESAR, Comparison of surveillance versus Aortic Endografting for Small Aneurysm Repair trial; CI, confidence interval; CT, computed tomography; DREAM, Dutch Randomized Endovascular Aneurysm Management trial; EVAR, endovascular aneurysm repair; HR, hazard ratio; IFU, Instructions for Use; OVER, Open Versus Endovascular Repair trial; PIVOTAL, Positive Impact of endoVascular Options for Treating Aneurysms earLy trial; UKSAT, United Kingdom Small Aneurysm Trial.

Notes

[version 1; referees: 2 approved]

Funding Statement

The author(s) declared that no grants were involved in supporting this work.

Notes

Editorial Note on the Review Process

F1000 Faculty Reviews are commissioned from members of the prestigious F1000 Faculty and are edited as a service to readers. In order to make these reviews as comprehensive and accessible as possible, the referees provide input before publication and only the final, revised version is published. The referees who approved the final version are listed with their names and affiliations but without their reports on earlier versions (any comments will already have been addressed in the published version).

The referees who approved this article are:

  • Marc Schermerhorn, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
    No competing interests were disclosed.
  • Janet Powell, Imperial College London, London, UK
    No competing interests were disclosed.

References

1. Karthikesalingam A, Vidal-Diez A, Holt PJ, et al. : Thresholds for Abdominal Aortic Aneurysm Repair in England and the United States. N Engl J Med. 2016;375(21):2051–9. 10.1056/NEJMoa1600931 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
2. Bown MJ, Sutton AJ, Bell PR, et al. : A meta-analysis of 50 years of ruptured abdominal aortic aneurysm repair. Br J Surg. 2002;89(6):714–30. 10.1046/j.1365-2168.2002.02122.x [PubMed] [Cross Ref]
3. Karthikesalingam A, Holt PJ, Vidal-Diez A, et al. : Mortality from ruptured abdominal aortic aneurysms: clinical lessons from a comparison of outcomes in England and the USA. Lancet. 2014;383(9921):963–9. 10.1016/S0140-6736(14)60109-4 [PubMed] [Cross Ref] F1000 Recommendation
4. Lo RC, Schermerhorn ML.: Abdominal aortic aneurysms in women. J Vasc Surg. 2016;63(3):839–44. 10.1016/j.jvs.2015.10.087 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
5. Tang W, Yao L, Roetker NS, et al. : Lifetime Risk and Risk Factors for Abdominal Aortic Aneurysm in a 24-Year Prospective Study: The ARIC Study (Atherosclerosis Risk in Communities). Arterioscler Thromb Vasc Biol. 2016;36(12):2468–77. 10.1161/ATVBAHA.116.308147 [PubMed] [Cross Ref] F1000 Recommendation
6. Lee ES, Pickett E, Hedayati N, et al. : Implementation of an aortic screening program in clinical practice: implications for the Screen For Abdominal Aortic Aneurysms Very Efficiently (SAAAVE) Act. J Vasc Surg. 2009;49(5):1107–11. 10.1016/j.jvs.2008.12.008 [PubMed] [Cross Ref]
7. Ashton HA, Buxton MJ, Day NE, et al. : The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet. 2002;360(9345):1531–9. 10.1016/S0140-6736(02)11522-4 [PubMed] [Cross Ref]
8. Dubost C, Allary M, Oeconomos N.: Resection of an aneurysm of the abdominal aorta: reestablishment of the continuity by a preserved human arterial graft, with result after five months. AMA Arch Surg. 1952;64(3):405–8. 10.1001/archsurg.1952.01260010419018 [PubMed] [Cross Ref]
9. Hertzer NR.: Current status of endovascular repair of infrarenal abdominal aortic aneurysms in the context of 50 years of conventional repair. Ann N Y Acad Sci. 2006;1085:175–86. 10.1196/annals.1383.015 [PubMed] [Cross Ref]
10. Hannan EL, Kilburn H, Jr, O'Donnell JF, et al. : A longitudinal analysis of the relationship between in-hospital mortality in New York State and the volume of abdominal aortic aneurysm surgeries performed. Health Serv Res. 1992;27(4):517–42. [PMC free article] [PubMed]
11. Meltzer AJ, Connolly PH, Schneider DB, et al. : Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State. J Vasc Surg. 2017; pii: S0741-5214(17)30106-4. 10.1016/j.jvs.2016.12.115 [PubMed] [Cross Ref] F1000 Recommendation
12. McPhee JT, Robinson WP, 3rd, Eslami MH, et al. : Surgeon case volume, not institution case volume, is the primary determinant of in-hospital mortality after elective open abdominal aortic aneurysm repair. J Vasc Surg. 2011;53(3):591–599.e2. 10.1016/j.jvs.2010.09.063 [PubMed] [Cross Ref] F1000 Recommendation
13. Parodi JC, Palmaz JC, Barone HD.: Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg. 1991;5(6):491–9. 10.1007/BF02015271 [PubMed] [Cross Ref]
14. Volodos NL.: Historical perspective: The first steps in endovascular aortic repair: how it all began. J Endovasc Ther. 2013;20(Suppl 1):I3–23. 10.1583/1545-1550-20.sp1.I-3 [PubMed] [Cross Ref]
15. Dua A, Kuy S, Lee CJ, et al. : Epidemiology of aortic aneurysm repair in the United States from 2000 to 2010. J Vasc Surg. 2014;59(6):1512–7. 10.1016/j.jvs.2014.01.007 [PubMed] [Cross Ref] F1000 Recommendation
16. Budtz-Lilly J, Venermo M, Debus S, et al. : Editor's Choice - Assessment of International Outcomes of Intact Abdominal Aortic Aneurysm Repair over 9 Years. Eur J Vasc Endovasc Surg. 2017;54(1):13–20. 10.1016/j.ejvs.2017.03.003 [PubMed] [Cross Ref] F1000 Recommendation
17. Hicks CW, Canner JK, Arhuidese I, et al. : Comprehensive Assessment of Factors Associated With In-Hospital Mortality After Elective Abdominal Aortic Aneurysm Repair. JAMA Surg. 2016;151(9):838–45. 10.1001/jamasurg.2016.0782 [PubMed] [Cross Ref] F1000 Recommendation
18. Szilagyi DE, Smith RF, DeRusso FJ, et al. : Contribution of abdominal aortic aneurysmectomy to prolongation of life. Ann Surg. 1966;164(4):678–99. 10.1097/00000658-196610000-00014 [PubMed] [Cross Ref]
19. Szilagyi DE, Elliott JP, Smith RF.: Clinical fate of the patient with asymptomatic abdominal aortic aneurysm and unfit for surgical treatment. Arch Surg. 1972;104(4):600–6. 10.1001/archsurg.1972.04180040214036 [PubMed] [Cross Ref]
20. Parkinson F, Ferguson S, Lewis P, et al. : Rupture rates of untreated large abdominal aortic aneurysms in patients unfit for elective repair. J Vasc Surg. 2015;61(6):1606–12. 10.1016/j.jvs.2014.10.023 [PubMed] [Cross Ref] F1000 Recommendation
21. Mortality results for randomised controlled trial of early elective surgery or ultrasonographic surveillance for small abdominal aortic aneurysms. The UK Small Aneurysm Trial Participants. Lancet. 1998;352(9141):1649–55. 10.1016/S0140-6736(98)10137-X [PubMed] [Cross Ref]
22. United Kingdom Small Aneurysm Trial Participants, . Powell JT, Brady AR, et al. : Long-term outcomes of immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med. 2002;346(19):1445–52. 10.1056/NEJMoa013527 [PubMed] [Cross Ref]
23. Powell JT, Brown LC, Forbes JF, et al. : Final 12-year follow-up of surgery versus surveillance in the UK Small Aneurysm Trial. Br J Surg. 2007;94(6):702–8. 10.1002/bjs.5778 [PubMed] [Cross Ref] F1000 Recommendation
24. Lederle FA, Wilson SE, Johnson GR, et al. : Immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med. 2002;346(19):1437–44. 10.1056/NEJMoa012573 [PubMed] [Cross Ref]
25. Cao P, De Rango P, Verzini F, et al. : Comparison of surveillance versus aortic endografting for small aneurysm repair (CAESAR): results from a randomised trial. Eur J Vasc Endovasc Surg. 2011;41(1):13–25. 10.1016/j.ejvs.2010.08.026 [PubMed] [Cross Ref] F1000 Recommendation
26. Ouriel K, Clair DG, Kent KC, et al. : Endovascular repair compared with surveillance for patients with small abdominal aortic aneurysms. J Vasc Surg. 2010;51(5):1081–7. 10.1016/j.jvs.2009.10.113 [PubMed] [Cross Ref] F1000 Recommendation
27. Laturnus J, Oliveira N, Basto Gonçalves F, et al. : Towards individualized follow-up protocols after endovascular aortic aneurysm repair. J Cardiovasc Surg (Torino). 2016;57(2):242–7. [PubMed]
28. Schanzer A, Greenberg RK, Hevelone N, et al. : Predictors of abdominal aortic aneurysm sac enlargement after endovascular repair. Circulation. 2011;123(24):2848–55. 10.1161/CIRCULATIONAHA.110.014902 [PubMed] [Cross Ref] F1000 Recommendation
29. Sweet MP, Fillinger MF, Morrison TM, et al. : The influence of gender and aortic aneurysm size on eligibility for endovascular abdominal aortic aneurysm repair. J Vasc Surg. 2011;54(4):931–7. 10.1016/j.jvs.2011.02.054 [PubMed] [Cross Ref] F1000 Recommendation
30. Lo RC, Bensley RP, Hamdan AD, et al. : Gender differences in abdominal aortic aneurysm presentation, repair, and mortality in the Vascular Study Group of New England. J Vasc Surg. 2013;57(5):1261–8, 1268.e1–5. 10.1016/j.jvs.2012.11.039 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
31. Ouriel K, Greenberg RK, Clair DG, et al. : Endovascular aneurysm repair: gender-specific results. J Vasc Surg. 2003;38(1):93–8. 10.1016/S0741-5214(03)00127-7 [PubMed] [Cross Ref]
32. Greenhalgh RM, Brown LC, Kwong GP, et al. : Comparison of endovascular aneurysm repair with open repair in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day operative mortality results: randomised controlled trial. Lancet. 2004;364(9437):843–8. 10.1016/S0140-6736(04)16979-1 [PubMed] [Cross Ref]
33. United Kingdom EVAR Trial Investigators, . Greenhalgh RM, Brown LC, et al. : Endovascular versus open repair of abdominal aortic aneurysm. N Engl J Med. 2010;362(20):1863–71. 10.1056/NEJMoa0909305 [PubMed] [Cross Ref]
34. Patel R, Sweeting MJ, Powell JT, et al. : Endovascular versus open repair of abdominal aortic aneurysm in 15-years' follow-up of the UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial. Lancet. 2016;388(10058):2366–74. 10.1016/S0140-6736(16)31135-7 [PubMed] [Cross Ref] F1000 Recommendation
35. Prinssen M, Verhoeven EL, Buth J, et al. : A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms. N Engl J Med. 2004;351(16):1607–18. 10.1056/NEJMoa042002 [PubMed] [Cross Ref]
36. Blankensteijn JD, de Jong SE, Prinssen M, et al. : Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms. N Engl J Med. 2005;352(23):2398–405. 10.1056/NEJMoa051255 [PubMed] [Cross Ref]
37. De Bruin JL, Baas AF, Buth J, et al. : Long-term outcome of open or endovascular repair of abdominal aortic aneurysm. N Engl J Med. 2010;362(20):1881–9. 10.1056/NEJMoa0909499 [PubMed] [Cross Ref] F1000 Recommendation
38. Prinssen M, Buskens E, de Jong SE, et al. : Cost-effectiveness of conventional and endovascular repair of abdominal aortic aneurysms: results of a randomized trial. J Vasc Surg. 2007;46(5):883–90. 10.1016/j.jvs.2007.07.033 [PubMed] [Cross Ref]
39. Lederle FA, Freischlag JA, Kyriakides TC, et al. : Outcomes following endovascular vs open repair of abdominal aortic aneurysm: a randomized trial. JAMA. 2009;302(14):1535–42. 10.1001/jama.2009.1426 [PubMed] [Cross Ref] F1000 Recommendation
40. Lederle FA, Freischlag JA, Kyriakides TC, et al. : Long-term comparison of endovascular and open repair of abdominal aortic aneurysm. N Engl J Med. 2012;367(21):1988–97. 10.1056/NEJMoa1207481 [PubMed] [Cross Ref] F1000 Recommendation
41. Lal BK, Zhou W, Li Z, et al. : Predictors and outcomes of endoleaks in the Veterans Affairs Open Versus Endovascular Repair (OVER) Trial of Abdominal Aortic Aneurysms. J Vasc Surg. 2015;62(6):1394–404. 10.1016/j.jvs.2015.02.003 [PubMed] [Cross Ref] F1000 Recommendation
42. Lederle FA, Stroupe KT, Open Versus Endovascular Repair (OVER) Veterans Affairs Cooperative Study Group: Cost-effectiveness at two years in the VA Open Versus Endovascular Repair Trial. Eur J Vasc Endovasc Surg. 2012;44(6):543–8. 10.1016/j.ejvs.2012.10.002 [PubMed] [Cross Ref] F1000 Recommendation
43. Lederle FA, Stroupe KT, Kyriakides TC, et al. : Long-term Cost-effectiveness in the Veterans Affairs Open vs Endovascular Repair Study of Aortic Abdominal Aneurysm: A Randomized Clinical Trial. JAMA Surg. 2016;151(12):1139–44. 10.1001/jamasurg.2016.2783 [PubMed] [Cross Ref]
44. Becquemin J, Pillet JC, Lescalie F, et al. : A randomized controlled trial of endovascular aneurysm repair versus open surgery for abdominal aortic aneurysms in low- to moderate-risk patients. J Vasc Surg. 2011;53(5):1167–1173.e1. 10.1016/j.jvs.2010.10.124 [PubMed] [Cross Ref] F1000 Recommendation
45. Powell JT, Sweeting MJ, Ulug P, et al. : Meta-analysis of individual-patient data from EVAR-1, DREAM, OVER and ACE trials comparing outcomes of endovascular or open repair for abdominal aortic aneurysm over 5 years. Br J Surg. 2017;104(3):166–78. 10.1002/bjs.10430 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
46. Epstein D, Sculpher MJ, Powell JT, et al. : Long-term cost-effectiveness analysis of endovascular versus open repair for abdominal aortic aneurysm based on four randomized clinical trials. Br J Surg. 2014;101(6):623–31. 10.1002/bjs.9464 [PubMed] [Cross Ref] F1000 Recommendation
47. EVAR trial participants: Endovascular aneurysm repair and outcome in patients unfit for open repair of abdominal aortic aneurysm (EVAR trial 2): randomised controlled trial. Lancet. 2005;365(9478):2187–92. 10.1016/S0140-6736(05)66628-7 [PubMed] [Cross Ref]
48. United Kingdom EVAR Trial Investigators, . Greenhalgh RM, Brown LC, et al. : Endovascular repair of aortic aneurysm in patients physically ineligible for open repair. N Engl J Med. 2010;362(20):1872–80. 10.1056/NEJMoa0911056 [PubMed] [Cross Ref] F1000 Recommendation
49. Sweeting MJ, Balm R, Desgranges P, et al. : Individual-patient meta-analysis of three randomized trials comparing endovascular versus open repair for ruptured abdominal aortic aneurysm. Br J Surg. 2015;102(10):1229–39. 10.1002/bjs.9852 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
50. Ali MM, Flahive J, Schanzer A, et al. : In patients stratified by preoperative risk, endovascular repair of ruptured abdominal aortic aneurysms has a lower in-hospital mortality and morbidity than open repair. J Vasc Surg. 2015;61(6):1399–407. 10.1016/j.jvs.2015.01.042 [PubMed] [Cross Ref] F1000 Recommendation
51. Schermerhorn ML, O'Malley AJ, Jhaveri A, et al. : Endovascular vs. open repair of abdominal aortic aneurysms in the Medicare population. N Engl J Med. 2008;358(5):464–74. 10.1056/NEJMoa0707348 [PubMed] [Cross Ref] F1000 Recommendation
52. Schermerhorn ML, Buck DB, O'Malley AJ, et al. : Long-Term Outcomes of Abdominal Aortic Aneurysm in the Medicare Population. N Engl J Med. 2015;373(4):328–38. 10.1056/NEJMoa1405778 [PMC free article] [PubMed] [Cross Ref] F1000 Recommendation
53. Chang DC, Parina RP, Wilson SE.: Survival After Endovascular vs Open Aortic Aneurysm Repairs. JAMA Surg. 2015;150(12):1160–6. 10.1001/jamasurg.2015.2644 [PubMed] [Cross Ref] F1000 Recommendation
54. Mastracci TM, Eagleton MJ, Kuramochi Y, et al. : Twelve-year results of fenestrated endografts for juxtarenal and group IV thoracoabdominal aneurysms. J Vasc Surg. 2015;61(2):355–64. 10.1016/j.jvs.2014.09.068 [PubMed] [Cross Ref] F1000 Recommendation
55. Eagleton MJ, Follansbee M, Wolski K, et al. : Fenestrated and branched endovascular aneurysm repair outcomes for type II and III thoracoabdominal aortic aneurysms. J Vasc Surg. 2016;63(4):930–42. 10.1016/j.jvs.2015.10.095 [PubMed] [Cross Ref] F1000 Recommendation

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