Comparison of EVAR and open repair in patients with small abdominal aortic aneurysms: Can we predict results of the PIVOTAL trial?
Article Outline
Objective
Data from multicenter studies support observation of small abdominal aortic aneurysms (AAAs) over open repair (OR), but the role of endovascular repair (EVAR) is unclear pending outcome of the Positive Impact of EndoVascular Options for Treating Aneurysm earLy (PIVOTAL) trial. Our goal was to predict the outcome of the trial by comparing results of small AAA repair using EVAR vs OR at a tertiary institution.
Methods
Using selection criteria of PIVOTAL trial, we reviewed clinical data of 194 consecutive patients, who underwent EVAR or OR for 4.0-5.0 cm AAAs between 1997 and 2004. All-cause and aneurysm-related deaths, complications, reinterventions, ruptures, and conversions were documented; factors affecting outcome were analyzed using χ2 tests, Wilcoxon rank-sum tests, logistic regression Kaplan-Meier method with log-rank tests, and Cox proportional hazards regression. Median follow-up was 3.9 years (range, 1 month to 9 years).
Results
A total of 194 patients, 162 males, 32 females (mean age: 71 years, range, 46-86) underwent 162 OR and 32 EVAR. EVAR patients were older (mean 74 ± 6 vs 71 ± 7, P = .002), had lower ejection fraction (mean 54 ± 11 vs 61 ± 13, P = .0002), and less likely to have ever smoked (69% vs 85%, P = .03) than OR patients. Thirty-day mortality was 1.3% (2/162) for OR and 0% for EVAR (0/33) (P = not significant [NS]). There were 49 systemic complications (7 EVAR, 42 OR, P = NS) and 10 local complications (3 EVAR, 7 OR, P = NS). During follow-up, there were no conversions and no ruptures. Freedom from reinterventions at 5 years was 83.1% ± 6.9% for EVAR and 95.3% ± 1.8% for OR (P = 0.02). There were 26 deaths (3 EVAR, 23 OR); but no procedure or aneurysm-related death was confirmed after 30 days (cause unknown in 16 deaths, 62%). Survival rates at 1-year were 96.6% ± 3.4% for EVAR and 97.4% ± 1.3% for OR; 5-year rates were 86.9% ± 7.2% ± EVAR and 86.9% ± 3.3% for OR (P = 0.69). Multivariate analysis revealed age (hazard ratio = 1.1 per year, P = .0496) and AAA size (hazard ratio = 13.8 per 1 cm, P = .03) were associated with death but EVAR vs OR was not (P = .23).
Conclusion
For repair of small AAAs, results of EVAR vs OR are not different at 5 years at a tertiary institution. Multicenter studies confirmed OR were not superior to observation in these patients. We predict the PIVOTAL study will conclude EVAR is not superior to observation.
In the United States, each year about 9000 deaths occur from ruptured abdominal aortic aneurysms (AAAs) and rupture is the 13th leading cause of death in the Western hemisphere.1 The risk of rupture is directly related to aneurysm size;2 elective repair is recommended to patients with AAAs of 5.5 cm or greater in diameter. Large multicenter studies such as the UK Small Aneurysm Trial (UKSAT) and the US Veterans Administration Aneurysm Detection and Management (ADAM) trial compared outcome of open surgery to observation in a select population with serial follow-up imaging and concluded that small AAA (<5.5 cms) should be observed.3, 4
The first successful human endovascular repair (EVAR) of AAA was done in 1990 by Dr Juan Parodi.5 Subsequent studies revealed that EVAR is associated with lower mortality and complication rates, less blood transfusions, reduced intensive care unit (ICU) and hospital stay, and improved early outcome compared to open repair (OR).6, 7, 8 When compared to large AAAs (>6 cm), EVAR in patients with small AAAs had more favorable anatomy, lower migration rates, less conversion to OR, and better long term outcome with 99% freedom from AAA death at 5 years.9, 10 These results have lead to an increase in the number of small AAA repairs using EVAR.
Two ongoing randomized controlled trials, one in Europe (CAESAR - Comparison of surveillance vs Aortic Endografting for Small Aneurysm Repair)11 and one in the United States12 (PIVOTAL - Positive Impact of endoVascular Options for Treating Aneurysms early) are currently evaluating EVAR vs surveillance in subjects with small AAAs using the Zenith (Cook Medical Inc, Bloomington, Ind) and AneuRx (Medtronic, Sunnyvale, Calif) devices, respectively. Results of these studies will not be available for several years. Our goal was to predict the outcome of the trials by comparing results of repairs of small (4 to 5 cm) AAAs using EVAR vs OR at a tertiary institution using selection criteria of the PIVOTAL trial. We elected to use criteria of the PIVOTAL trial since European studies often report results that differ from those found in US studies, and device availability in Europe is not the same as in the US. In addition, our follow-up is based on computed tomography (CT) studies and not on color duplex scan which is being used in the CAESAR trial.
Methods
Using criteria of the PIVOTAL trial (Table I), we retrospectively reviewed the clinical and radiological data for all patients with small (4.0-5.0 cm) infrarenal degenerative AAAs that was treated electively between June 1997 and July 2004 at Mayo Clinic, Rochester, Minn. The decision of whether to treat a patient with EVAR or OR was left to the surgeon's discretion and patient's preference with no device bias. Device choice, sizing, suitability, seal zones, landing zones, and technical success were decided by the operating team. Patient's selection for EVAR was according to strict device instructions for use (IFU) criteria. For patients less than 70 years of age, OR was offered preferentially. The access vessels also had to be adequate size with minimal tortuosity to allow delivery of the device. All patients underwent CT preoperatively to define aneurysm anatomy; contrast aortography, and magnetic resonance angiography (MRA) was used selectively. Demographic, clinical, and radiological data were recorded using the joint Society for Vascular Surgery/International Society of Cardiovascular Surgery (SVS/ISCVS) standards. Complications were defined along the standards for the Ad Hoc Committee for Standardized Reporting Practices in Vascular Surgery of the Society for Vascular Surgery/American Association for Vascular Surgery and a grading severity scale was recorded for each complication when appropriate.13 Primary patency, primary assisted patency, and secondary patency were defined using the standardized reporting practices of the SVS/American Association for Vascular Surgery (AAVS).13 All readmissions and reinterventions related to the AAA treatment during the follow-up were recorded. Reinterventions were defined as any therapeutic procedures done after the initial AAA treatment for a complication arising from this treatment. Secondary endpoints were technical success rate, freedom from AAA-related death, AAA rupture, and open conversion following EVAR.
Table I. Our matched PIVOTAL criteria
| INCLUSION |
 Candidates must meet ALL of the following inclusion criteria to be eligible: |
| Patient is 40-90 years of age |
| Patient must be low to moderate risk (0, 1, or 2 except for age) by SVS/ISCVS |
| Baseline serum Cr <2.5 mg/dL |
| Abdominal aortic aneurysm 4.0-5.0 cm is confirmed by computed tomography (CT) scan within 3 months of procedure |
| Life expectancy of at least 3 years |
| If patient is a female of child bearing potential, must have a negative pregnancy test within 7 days of procedure |
| EXCLUSION |
| Candidates who meet ANY of the following exclusion criteria are NOT eligible: |
| Mycotic, symptomatic, ruptured or traumatic aneurysm |
| Myocardial infarction without revascularization <6 months or with revascularization <1 month |
| Cerebrovascular accident (CVA) or transient ischemic attack (TIA) within 30 days |
| Connective tissue disorder eg, Marfan's or Ehlers Danlos Syndrome |
| Peripheral white blood count (WBC) <3,000/ul or Platelet counts <100,000/ul or >1,000,000/ul |
| Diffuse distal embolization |
| Inflammatory aneurysm |
| Known bleeding or hypercoaguable state |
| Major surgical or interventional procedure (vascular or non-vascular) procedure within 30 days of procedure |
| Severe risk (3) by SVS/ISCVS |
| Known thoracic aortic aneurysm >5 cm |
| Iliac artery aneurysm >3 cm |
| Bilateral iliac artery <7 mm |
| Planned conduit for EVAR procedure |
| Life expectancy less than 3 years due to a known co-existing condition |
All patients who underwent EVAR were followed according to our standard protocol that included contrast and non-contrast CT scans at every 6 months. All radiological images were reviewed by an independent radiologist for graft migration, endoleaks, limb complications including kinking and sac shrinkage based on diameter measurements. Migration was defined as >5 mm caudal movement from the first CT scan following EVAR while sac shrinkage was defined as a decrease in aortic diameter >5 mm at a comparable slice on CT scan. Limb kinking was defined as a change in limb angulation on CT scan resulting in a 50% diameter reduction. All patients who underwent ORs were followed with serial clinical examination and imaging with color duplex, CT, or MRA scanning.
Statistical analysis
All data were recorded using Excel software (Microsoft) and JMP format and then transferred to SAS software (SAS, Cary, NC) for statistical analysis. Descriptive statistics, including means, medians, standard deviations, ranges, and proportions were calculated as appropriate. The χ2 or Fisher's exact tests, as appropriate, were used to compare nominal variables between the two groups.
Logistic regression models were used to analyze the association between type of surgical procedure and the 30-day outcomes of complications. Multiple variable logistic regression models were used to adjust for age, and other risk factors including gender. The univariate and multivariate odds ratios (EVAR vs OR) with 95% confidence intervals (CIs) are reported for the surgical repair group variable.
Primary patency, primary assisted patency, secondary patency, reintervention, and freedom from a combined failure endpoint incorporating AAA-related death, AAA rupture, or conversion were estimated with the Kaplan-Meier survival method. Significance tests comparing the two groups were performed with log-rank tests. Multiple-variable Cox proportional hazards models were used to adjust for possible confounding variables in the analysis of the primary patency and reintervention endpoints. The univariate and multivariate hazard ratios (EVAR vs OR) and the associated 95% CIs were reported for the type of surgical repair variable. A P value of < .05 was considered statistically significant for all analyses.
Results
Demographic data
After approval by our institutional IRB Board, the records of 194 patients with small (4.0-5.0 cm) infrarenal AAA meeting the PIVOTAL criteria were evaluated for the period from June 1, 1997 to June 30, 2004. During the study period, a total of 334 EVAR and 1366 OR were performed, our study population (194/1700) represents approximately 11% of this total group. One hundred sixty-two males, 32 females (mean age 71 years, range, 46-86) underwent 162 OR and 32 EVAR (Table II). Median follow-up time was 3.9 years (range, 1 month to 9 years).
Table II. Baseline characteristics
| Variable | Overall (n = 194) | EVAR (n = 32) | OR (n = 162) | P value⁎ |
|---|---|---|---|---|
| Age, mean(SD) | 71.2(6.9) | 74.5(5.7) | 70.6(7.0) | .002 |
| Male gender, n(%) | 162(84) | 26(81) | 136(84) | .71 |
| AAA diameter(cm), mean(SD) | 4.8(0.3) | 4.9(0.1) | 4.8(0.3) | .25 |
| BMI, mean(SD) | 27.6(4.6) | 28.0(4.9) | 27.5(4.6) | .54 |
| n missing | 7 | 0 | 7 | |
| Ever smoked, n(%) | 160(82) | 22(69) | 138(85) | .03 |
| DM, n(%) | 15(8) | 4(13) | 11(7) | .28 |
| Hypertension, n(%) | 145(75) | 23(72) | 122(75) | .68 |
| COPD, n(%) | 24(12) | 5(16) | 19(12) | .56 |
| CAD, n(%) | 105(54) | 18(58) | 87(54) | .66 |
| n missing | 1 | 1 | 0 | |
| Pre-op Cr, mean(SD) | 1.2(0.3) | 1.2(0.2) | 1.3(0.3) | .84 |
| Renal insufficiency, n(%) | 38(20) | 8(25) | 30(19) | .40 |
| Ejection fraction, mean(SD) | 60.0(12.7) | 54.1(11.3) | 61.3(12.7) | .0002 |
| n missing | 51 | 7 | 44 |
⁎P value comparing endovascular aneurysm repair |
All patients were asymptomatic from their AAA and admitted for elective treatment; there were no planned adjunctive procedures at the time of repair. The majority of patients underwent AAA repair for significant anxiety about the diagnosis, some were also from geographically remote areas with difficult access to urgent health care, while some were treated based on rapid growth rate or the presence of a saccular aneurysm. All patients underwent preoperative CT scans to image aneurysm dimensions and suitability for EVAR. All patients had infrarenal AAA. Patients with juxtarenal and suprarenal AAA were excluded and any patient who had an unplanned adjunctive aortic or visceral procedure was also excluded from our data. Table II shows both EVAR and OR patient risk factor distribution. EVAR patients were older (mean 74 ± 6 vs 71 ± 7, P = .002), had lower ejection fraction (mean 54 ± 11 vs 61 ± 13, P = .0002), and less likely to have ever smoked (69% vs 85%, P = .03) than OR.
Intraoperative resultsAll cases were performed under general anesthesia. EVAR was performed in a state of the art endovascular operating suite.
OR groupThe primary procedure consisted of endoaneurysmorrhaphy with aortic tube grafts in 43% (70/162) and bifurcated grafts in 57% (92/162). The transperitoneal approach was used in 96% (154/162) in cases; a retroperitoneal repair was used in 4% (8/162). One patient had a ureteral transection that was repaired primarily and had no subsequent postoperative complications. No unplanned arterial procedures were performed and there was no intraoperative death.
EVAR groupThe devices used to complete EVAR were AneuRx (Medtronic, Sunnyvale, Calif) in 50% (16/32), Ancure/EVT (Guidant Endovascular Technologies, Menlo Park, Calif) in 28% (9/32), Excluder (W. L. Gore & Associates, Flagstaff, Ariz) in 22% (7/32). All EVAR cases were performed through groin incisions and no additional retroperitoneal exposure was required. There were no conversions and no secondary procedures were performed on the iliac vessels at the time of EVAR. Completion angiograms revealed 17 endoleaks in 15 patients, 6 type I endoleaks only, 8 type II endoleaks, 3 had both type I and II endoleaks. All type I endoleaks were successfully treated with repeat angioplasty and/or proximal stenting before the completion of the procedure.
Early results
EVAR and OR mortalityThere was no statistically significant difference in the 30-day mortality between the two groups (P = 1.0), the mortality rate in the OR group was 1.3% (2/162) and 0% (0/32) for the EVAR group. One OR patient died of respiratory failure and 1 died of a myocardial infarction (MI).
EVAR group early morbidityAmong the 32 EVAR patients, 9 patients (28%) had early complications. These included cardiac complications in 3 (1 congestive heart failure, 1 arrhythmia, and 1 non ST elevation MI), neurological complications in 2 (1 stroke and 1 confusion), renal failure in 2 and transfusion reaction, ischemic colitis, and groin lymphocele in 1 patient each.
OR group early morbidityIn the OR group, the early complication rate was 30% (48/162). Seven patients had 9 local complications, the majority of these were wound seromas or lymphoceles, 1 patient had a fascial dehiscence and 1 had a superficial wound infection. Systemic complications occurred in 39 patients accounting for 70 complications, the majority of these were classified as mild; 3 patients had an MI, and 2 patients developed reversible renal insufficiency. Two patients had acute graft limb thrombosis, (2 required graft limb thrombectomy, 1 with revision of the distal anastomosis), 2 patients had hematoma requiring re-exploration.
Late results
EVAR groupThere was a 3% (1/32) late complication rate in the EVAR group; 1 patient had a groin lymphocele which required surgical exploration and repair. Primary patency, primary-assisted patency, and secondary patency rates for the EVAR group were 100%, 100%, and 100%, respectively. Aneurysm sac follow-up was available for 97% (31/32) of patients; sac shrinkage (>5 mm) was documented in 84% (26/31), EVAR patients, no change in 6% (2/31) and sac increase in 10% (3/31) of patients by CT scanning. No patient in the EVAR group had a migration greater than 5 mm on follow-up imaging. There were 3 late deaths in this group but cause of death was not confirmed by autopsy.
OR groupIn this group, the late complication rate was 7% (11/162). There were 5 patients with local complications; 1 lymphocele, 4 incisional hernias (one requiring bowel resection at the time of hernia repair), and 6 patients with systemic complications. Of the late complications, 3 were graft-related; 2 patients presented with limb ischemia, 1 requiring graft thrombectomy alone and the other a femoral to femoral artery bypass; 1 patient needed anastomotic balloon angioplasty and stenting of the distal (iliac) anastomosis for worsening claudication. The primary patency, primary-assisted patency, and secondary patency rates for the OR group was 98.1%, 99.3%, and 100%, respectively. There were 21 late deaths and the cause of death was known in 38% (Table III).
Table III. Outcomes for endovascular aneurysm repair(EVAR) and open repair(OR) groups
| Outcome | Overall | EVAR | OR | P value† |
|---|---|---|---|---|
| Systemic/GI complication | ||||
| Early or Late, n(%) | 48(25%) | 7(22%) | 41(25%) | .68 |
| Early, n(%) | 46(24%) | 7(22%) | 39(24%) | .79 |
| Local complication | ||||
| Early or Late, n(%) | 14(7%) | 2(6%) | 12(7%) | 1.0 |
| Early, n(%) | 8(4%) | 1(3%) | 7(4%) | 1.0 |
| Any complication⁎ | ||||
| Early or Late, n(%) | 61(31%) | 10(31%) | 51(31%) | .98 |
| Early, n(%) | 52(27%) | 9(28%) | 43(27%) | .85 |
| Reintervention, n | 12 | 7 | 5 | |
| Freedom from reintervention | ||||
| 30-day rate(95% CI) | 96.9%(94.5%,99.4%) | 93.8%(85.7%,100%) | 97.5%(95.2%,100%) | .02 |
| 1-year rate(95% CI) | 95.2%(92.2%,98.3%) | 90.5%(80.9%,100%) | 96.2%(93.2%,99.2%) | |
| 5-year rate(95%CI) | 93.2%(89.5%,97.0%) | 83.1%(70.6%,97.9%) | 95.3%(91.9%,98.8%) | |
| Death, n | 26 | 3 | 23 | |
| Survival | ||||
| 30-day rate(95% CI) | 98.9%(97.5%,100%) | 100% | 98.7%(97.0%,100%) | .69 |
| 1-year rate(95% CI) | 97.2%(94.9%,99.7%) | 96.6%(90.1%,100%) | 97.4%(94.9%,100%) | |
| 5-year rate(95% CI) | 86.9%(81.1%,93.0%) | 86.9%(73.9%,100%) | 86.9%(80.6%,93.6%) |
⁎Two additional patients |
†P values were calculated using χ2 or Fisher's exact tests for complications and log-rank tests for reintervention and survival. |
Survival rates at 1-year were 96.6% ± 3.4% for EVAR and 97.4% ± 1.3% for OR; 5-year rates were 86.9% ± 7.2% ± EVAR and 86.9% ± 3.3% for OR (P = .69) (Fig 1). Variables significantly associated with death included age (P = .02) and AAA size (P = .01). In a multivariable model including EVAR vs OR for the outcome of death, age (hazard ratio = 1.1 per year, P = .0496) and AAA size (hazard ratio = 13.8 per 1 cm, P = .03) remain significant, while EVAR vs OR was not (P = .23).
Fig 1.
Freedom from re-intervention curves at 5 years.
Reinterventions
EVAR groupThe reintervention rate was 16% (5/32), and was performed for 3 endoleaks - (1 each for type Ia, type Ib, and type II). All endoleak reinterventions were performed via percutaneous approach through the groin. The type Ia endoleak was treated with a proximal aortic cuff; an iliac limb extension was used to treat the type 1b endoleak. The type II endoleak was treated via the iliolumbar artery with coil embolization of the lumbar vessel. One patient who had diminished ankle-brachial indices (ABIs) had a diagnostic angiogram, emboli in the peroneal artery was identified and successfully treated with aspiration and local thrombolysis with tissue-plasminogen activator (t-PA) and 1 patient had a lymphocele excision.
OR groupReintervention rate was 2% (4/162) for the OR group, they were performed in 3 patients with graft limb complications, 2 presenting with acute limb ischemia, and 1 with worsening claudication (described in late results), 1 patient had a lymphocele excision.
Overall, freedom from reintervention rates at 5 years were 83.1% ± 6.9% for EVAR and 95.3% ± 1.8% for OR (P = .02) (Fig 2).
Fig 2.
Kaplan-Meier curves for the two groups for the survival outcome.
Discussion
The decision to treat any AAA is based on aneurysm diameter, expansion rate and symptoms, patient's risk factors, procedural risk, and the long-term clinical benefit of treatment. The goal of OR and EVAR is to prevent AAA rupture, rupture-related death, or death from treatment of the aneurysm. Two randomized controlled trials, conducted in the US and the UK, respectively, concluded that patients with small AAA (<5.5 cms) can be observed with surveillance imaging (annual risk of rupture being less than 1%), with open surgical repair reserved for growth beyond 5.5 cm or for symptoms.3, 4 Furthermore, the majority of patients in both the UK and the ADAM trial underwent AAA repair by the conclusion of the study.
EVAR was introduced as an alternative to OR for patients with AAA and is associated with lower perioperative mortality and morbidity rates than OR. The outcomes of EVAR following large (>5.5 cm) AAA repair was reported to be inferior to those who had EVAR for small aneurysms, with increased type 1 endoleaks, migration, systemic complications, conversion to OR, and diminished patient survival; these results suggested a reappraisal of the management of small AAA.10, 14 Two ongoing trials are investigating low-risk patients with small AAA, comparing surveillance observation to EVAR and results are forthcoming. However, the current consensus on the management of small AAA with EVAR is not yet answered.
Our patients with small AAA who underwent repair had a 30-day mortality of 0% for EVAR and 1.3% for OR (P = .69). These data are similar to those published by Zarins et al, 30 day perioperative mortality rate was 1.9% for their EVAR matched group (they compared matched patients with the UK small aneurysm study surveillance group).15 Ouriel et al reported on a 30-day perioperative mortality rate of 1.6% following EVAR and results in this study did not differ in patients with small vs large aneurysms.10 A recent metanalysis by De Rango et al analyzed results in 6090 patients who underwent EVAR for small (<5.5 cm) and large (>5.5 cm) AAAs: early mortality was 0%-1.6% in the small AAA group vs 2% to 3.2% in the large AAA, a difference that was statistically significant (odds ratio [OR] 0.68; 95% CI 0.51-0.90; test for heterogeneity P = .30).16 The 1.3% perioperative mortality in our study was lower than both ADAMs 2.7% and the UKSATs 6.3% mortality rate,4, 17 however, this may reflect lower-risk patients, a single institution's vs a multicenter trials' experience and case volumes.
In general, small AAA repairs have had a lower conversion rate after EVAR than large aneurysms. This high degree of freedom from conversion was documented by Zarins et al with 99% freedom from conversion at 5 years for small (<5 cm) AAA compared with 92% for large aneurysms (>6 cms),9 although their patients with small AAA had better aneurysm neck morphology. Ouriel et al also noted a higher conversion rate in patients with large aneurysms because of a higher incidence of graft migration and type I endoleaks.10 Brewster et al reported a conversion rate of 2.6% over a 12 year experience in 424 patients with small AAA undergoing EVAR.18 In the recent metanalysis, De Rango et al failed to show a statistically significant difference in conversion rates between small and large AAAs.16 This may be a reflection of operator experience, adherence to strict IFU guidelines, third generation devices, access vessel size, or aggressive endovascular reintervention. We had 100% technical success in performing EVAR in small AAAs, with no surgical conversion during follow-up at 4 years.
Overall, both early and late complication rates for both EVAR patients and OR patients were similar (30% vs 31% early and 3% vs 7% late), the majority of these were minor medical problems. Currently, there are no randomized studies comparing complications following repair of small AAA using EVAR and OR. In the EVAR 1 trial, the 4-year complication rate following EVAR was 41%, significantly greater than in the OR group (9%).19 The lower complication rate in our study of small AAAs following EVAR is interesting and may be related to operative technique, devices used, and the smaller aneurysm size/morphology.
The reintervention rate was 16% (5/32) for EVAR and 4% (7/162) for OR. This increase in reintervention after EVAR compared with OR has been reported in the treatment of large AAA19 and may be a reflection of EVAR technology. Ouriel et al noted an increase requirement for larger AAA than small AAA at 24 months (P = .069).10 However, De Rango et al showed similar secondary reintervention rates for small (10%-12%) and large AAA (10.5%-14.5%) undergoing EVAR.16 Similar results were shown by Brewster et al with no difference in reintervention between patients with small and large AAA undergoing EVAR at 12 years.18 The majority of our EVAR reinterventions (3/5) were reinterventions early in our experience for endoleaks. Most physicians will now not intervene for type II endoleaks in the absence of sac enlargement or symptoms; however, early in our study, we treated these endoleaks despite no increase in aneurysm size. Despite these good results, the long term durability of EVAR in these patients is still unknown, and reinterventions stress issues of the need for long-term surveillance with its associated cost, patient inconvenience, and compliance. Overall, 90% of aneurysm sac size was smaller or had no change on follow-up imaging, similar to data reported by Zarins et al who reported that in the small AAA group 93% were smaller or had no change.9 These numbers were better than the 60% sac reduction rate at 24 months, reported by Ouriel et al.10 Williams, at the XIX International Congress of Endovascular Intervention, suggested that small AAA (<5 cm) treated with Endologix device (Endologix, Irvine, Calif) had more sac regression.20 Bui et al retrospectively analyzed small AAA treated with EVAR with 5-year follow-up and concluded that EVAR for small AAA does not lead to fewer endoleaks, secondary interventions, or sac regression as compared to larger AAA.21 These differences are interesting and may suggest that the small aneurysm response to EVAR is multifactorial and may also depend on the type of endovascular device.
In our study, primary patency, assisted primary patency, and secondary patency rates were the similar between EVAR and OR groups. There were no iliac limb occlusions in the EVAR group despite the fact that these stent grafts were primarily older generation devices, hence one can speculate that vessel anatomy and run off status may be more important than device type as a risk factor for limb occlusion.
We found that survival rates at 1-year and 5-years were similar for both groups and they were excellent at 97% and 87%, respectively. At the end of the ADAM study, 25% of patients in the OR group and 22% in the surveillance group had died. Zarins et al reported that all-cause mortality rate for their EVAR match group was 18%, which was significantly better than the UKSAT surveillance group with an all-cause mortality rate of 48%. Our better 5-year survival rate probably reflects healthier patients with low SVS/ISCVS scores. There was no known aneurysm-related late mortality in our series, although the cause of death was unknown in 62% of the cases. When Zarins et al compared matched EVAR patients in the UKSAT surveillance group, the EVAR matched group had a fatal rupture rate of 0.6% while the surveillance group had a fatal rupture rate of 4.6%; EVAR had significantly reduced the risk of fatal aneurysm rupture and aneurysm-related death.15 Our result also compares favorably to the UKSAT; by the end of the trial 19 patients (3.6%) had experienced rupture with a rupture rate of 1.6%. Repair of aneurysm by either technique reduces aneurysm-related death in low-risk patients.
The age inclusion criteria for both the ADAM (50-79) and UK small AAA (60-76) studies were lower than our study (40-90 years). By multivariate analysis, aneurysm size, and age but not surgical technique has significant relationship to mortality. It appears that older patients with aneurysms are likely to die from their comorbidities rather than from an aneurysm-related cause. Hence, younger, low-risk patients must be carefully followed if we are to prevent these AAA-related deaths. Valentine et al22 reported noncompliance rates of one third in a veteran patient population and was associated with a higher risk or rupture and thus overall mortality, while Armstrong et al23 reported a compliance rate of 98.5% with only 0.9% lost to follow-up. Their operative rate at 29 months was 67% with cumulative aneurysm mortality of 0.9%. They concluded that implementation of a clinical pathway for surveillance was associated with a high compliance and low mortality.
Limitations to our study include small sample size, median follow-up time of 3.9 years, retrospective data with its potential treatment bias, and with the use of older generation devices for EVAR we could still make some meaningful observations. Also, no evaluation of cost or cost effectiveness of EVAR or OR were performed, nor did we examine quality of life and functional outcome after interventions; these issues may be more important than survival alone in this aging patient population.
When compared to the surveillance arm of ADAM and the UK small AAA trial, our EVAR and OR results seem to be better. However, results of EVAR vs OR in patients with small AAAs were not different at 5 years at our tertiary institution. Since the results of multicenter studies suggests that OR were not superior to observation, and our results suggest that EVAR is not superior to OR for repair of small AAAs, surgeons should continue to maintain a conservative approach in the management of aneurysms <5.5 cm in diameter pending the results of the PIVOTAL and CAESAR trials.
Author contributions
References
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Competition of interest: none.
PII: S0741-5214(08)01291-3
doi:10.1016/j.jvs.2008.07.085
© 2009 The Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
