Abstract
Introduction
As endovascular techniques (EVAR) continue to advance, eligibility of patients with anatomically complex abdominal aortic aneurysms (AAA) for EVAR is increasing. However, it remains largely unclear whether complex EVAR is associated with favorable outcome over conventional open repair and how outcomes compare to infrarenal EVAR. The purpose of this study was to examine perioperative outcomes of patients undergoing complex EVAR, focusing on differences with complex open repair and standard infrarenal EVAR.
Methods
We identified all patients undergoing non-ruptured complex EVAR, complex open repair, and infrarenal EVAR in the Targeted Vascular Module from the American College of Surgeons National Surgical Quality Improvement Program. Aneurysms were considered complex if the proximal extent was juxta- or suprarenal, and/or when the Cook Zenith Fenestrated endograft was used. Independent risks were established using multivariable logistic regression analysis.
Results
A total of 4584 patients were included, with 411 (9.0%) undergoing complex EVAR, 395 (8.6%) complex open repair, and 3778 (82.4%) infrarenal EVAR. Perioperative mortality following complex EVAR was 3.4% vs. 6.6% after open repair (P=.038), and 1.5% after infrarenal EVAR (P=.005). Postoperative acute kidney injuries occurred in 2.3% of complex EVAR patients vs. 9.5% of those undergoing complex open repair (P<.001), and 0.9% of infrarenal EVAR patients (P=.007). Compared to complex EVAR, complex open repair was an independent predictor of 30-day mortality (OR: 2.2, 95% CI:1.1–4.4), renal function deterioration (4.8, 2.2–10.5), and any complication (3.7, 2.5–5.5). When comparing complex to infrarenal EVAR, infrarenal EVAR was associated with favorable 30-day mortality (0.5, 0.2–0.9), and renal outcome (0.4, 0.2–0.9).
Conclusions
In this study assessing the perioperative outcomes of patients undergoing repair for anatomically complex AAAs, complex EVAR had fewer complications compared to complex open repair, but –in turn– did carry a higher risk of adverse outcomes than infrarenal EVAR. Further research is warranted to determine whether the benefits of EVAR compared to open repair for complex AAA treatment are maintained during long-term follow-up.
Introduction
Endovascular repair (EVAR) of an abdominal aortic aneurysm (AAA) is associated with lower perioperative mortality, as well as lower rates of complications, need for transfusions, and length of stay compared to open repair.1–4 Because of these benefits, the utilization of EVAR has rapidly increased since its introduction in 1996,5 with over 80% of infrarenal AAA repairs now being performed using endovascular treatment.6–8 Due to inadequate proximal seal zone, standard endovascular repair cannot be used for juxta- and suprarenal aneurysms (complex AAA), which has been reported to make up as much as 20% of all AAAs.9–11
Through advancements in endovascular treatment techniques, including chimney, fenestrated and branched stent grafts, EVAR can now be offered to patients with complex proximal neck anatomy.12 A large national series from the United Kingdom demonstrated that fenestrated endovascular repair can be performed with a high degree of technical and clinical success.13 However, most feasibility studies are institutional based and therefore often limited to small numbers of patients.14–18 Moreover, they usually did not compare outcome of complex EVAR to that of conventional open repair. Efforts that did compare complex EVAR to open repair yielded conflicting results. While one study demonstrated favorable perioperative outcomes after open repair,19 two other studies showed reduced 30-day morbidity and mortality associated with EVAR.20, 21 Adding to the confusion, two systematic reviews found perioperative benefits favoring EVAR,22, 23 while another review demonstrated a pooled perioperative mortality of 4.1% after both EVAR and open repair, with no difference in the complication rate.24
In addition, it has been suggested that complex EVAR is associated with increased risk of postoperative renal failure compared to uncomplicated infrarenal EVAR.25, 26 However, limited comparative data exist for infrarenal versus complex EVAR, and the presumed differences in renal complications could previously not be confirmed.27
The purpose of this study was to assess the perioperative outcome following EVAR for complex aneurysms, focusing on differences with complex open repair, the alternative treatment option, and standard infrarenal EVAR using the newly available Targeted Vascular data set of the National Surgical Quality Improvement Program.
Methods
For this study, we used the Targeted Vascular data set from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database. The ACS NSQIP is a multi-institutional collaboration with 102 participating hospitals in the United States that prospectively collect clinical data of patients undergoing major surgery. The NSQIP database includes demographics, comorbidities, intraoperative characteristics, and 30-day postoperative outcomes. The Targeted Vascular data set is a recently added module, which includes additional disease and procedure specific characteristics, and procedure-related outcomes chosen by vascular surgeons. All data collection is performed by trained clinical nurse reviewers and data abstractors. The validity of the ACS NSQIP has been confirmed in previous reports.28–30 The database contains de-identified data only without any protected health information. Therefore, Institutional Review Board approval and patient consent were waived. Additional information on the ACS NSQIP and the Targeted Vascular data set are available on www.acsnsqip.org.
From the Targeted Vascular data set for years 2011 to 2013, we identified all elective open and endovascular abdominal aortic aneurysm repairs, by the treatment indication variable. Thoracoabdominal aneurysms, procedures coded as repair of a ruptured AAA (CPT: 38082, 35092, 35103), and cases with a postoperative diagnosis code for a ruptured AAA (ICD-9: 441.3) were excluded from this study. Additionally, late conversions were excluded from analysis of complex open repairs (CPT: 34830, 34831, 34832). Results on this group have been reported previously.31 Early conversions were considered an outcome for EVAR patients and are therefore included in all analyses as EVAR patients. The remaining cohort was subsequently divided in three groups in accordance with both treatment modality and proximal aneurysm extent: complex EVAR, complex open repair, and infrarenal EVAR. A complex aneurysm was defined as an aneurysm with either a juxtarenal or suprarenal proximal extent. Aneurysms coded as pararenal, which is separately defined as an AAA involving the origin of the renal arteries according to the NSQIP, were also considered complex. Data on proximal extent of the aneurysm were obtained directly from operative reports by trained clinical reviewers. All aneurysms treated with the Cook Zenith Fenestrated endograft, which is currently the only fenestrated graft approved by the Food and Drug Administration, were also considered complex. Complex open repair patients with infrarenal aortic clamping were excluded. For patients undergoing open repair, a visceral vessel reconstruction was defined as mentioning of a CPT code for visceral vessel reconstruction (CPT: 35361), or mentioning of a visceral vessel reconstruction in the Targeted module.
Groups were compared on baseline and operative characteristics, as well as postoperative outcomes. Postoperative outcomes included 30-day mortality, and in-hospital adverse outcomes such renal function deterioration, ischemic colitis, leg ischemia, wound complications, shock, sepsis, and length of ICU and hospital stay. Renal function deterioration was defined as a rise in creatinine of >2 mg/dl from preoperative value, and/or requirement of hemodialysis, peritoneal dialysis, hemofiltration, hemodiafiltration, or ultrafiltration within 30 days of the operation. Patients on dialysis preoperatively were excluded for analysis of renal outcomes. Ischemic colitis was defined as having symptoms of ischemic colitis and/or confirmation of the diagnosis on diagnostic sigmoidoscopy or colonoscopy. Patients with SIRS, sepsis, or septic shock prior to surgery were not included for postoperative sepsis and shock analysis. Wound complications included superficial, deep, and organ space infections. In order to identify differences in postoperative morbidity aside from death, 30-day mortality was not included in the any complication variable.
Statistical analyses
Categorical variables are presented as counts and percentages, and continuous variables as mean ± standard deviation. Differences between treatment groups were assessed using χ2 and Fisher’s exact tests for categorical variables and Student’s t-test for continuous variables, where appropriate. To assess independent risks associated with treatment approaches, we used multivariable logistic regression analysis. Baseline characteristics were univariately tested, and predictors with a P-value <.1 were added to the multivariable model. Age was included in all models, regardless of the univariable association. Risk-adjusted comparisons of complex EVAR to complex open repair and infrarenal EVAR were performed separately, and different models were constructed for each analysis. All tests were two-sided and significance was considered when P-value < .05. Statistical analysis was performed using the IBM SPSS Statistics 21 (IBM Inc., Chicago, IL).
Results
A total of 4584 patients were included, with 411 (9.0%) undergoing complex EVAR, 395 (8.6%) complex open repair, and 3778 (82.4%) underwent EVAR for an infrarenal (noncomplex) AAA.
Baseline characteristics
Baseline characteristics are detailed in Table I. The complex EVAR group was older than the complex open repair group (74.9 vs. 72.2 years, P<.001), consisted of fewer females (22.4% vs. 33.2%, P=.001), and more non-white patients (11.1% vs. 5.4%, P=.005). In terms of comorbidities, we found that complex EVAR patients more often had insulin-dependent diabetes (3.9% vs. 1.3% P=.019), had a higher preoperative creatinine (1.22 vs. 1.09 mg/dl, P=.006), and were more commonly on dialysis (2.9% vs. 0.8%, P=.034). Conversely, complex EVAR patients were less often current smokers (29.2% vs. 45.6%, P<.001).
Table I.
Baseline characteristics
| EVAR complex | OR complex | EVAR infra | p-value | ||
|---|---|---|---|---|---|
|
| |||||
| N=411 | N=395 | N=3778 | Complex EVAR vs. OR | Infra vs. complex EVAR | |
| Age – years (sd) | 74.9 (8.1) | 72.2 (8.3) | 74.2 (8.6) | <.001 | .160 |
| Categories – N (%) | <.001 | .788 | |||
| <59 years | 17 (4.1) | 24 (6.1) | 191 (5.1) | <.001 | .788 |
| 60–69 | 90 (21.9) | 125 (31.6) | 898 (23.8) | ||
| 70–79 | 181 (44.0) | 165 (41.8) | 1573 (41.6) | ||
| 80–89 | 112 (27.3) | 80 (20.3) | 1015 (26.9) | ||
| 90+ | 11 (2.7) | 1 (0.3) | 101 (2.7) | ||
| Female gender – N (%) | 92 (22.4) | 131 (33.2) | 699 (18.5) | .001 | .056 |
| Race | .007 | .006 | |||
| American Indian/Alaska Native | 1 (0.2) | 2 (0.5) | 3 (0.1) | ||
| Asian | 15 (3.6) | 4 (1.0) | 85 (2.2) | ||
| Black or African American | 26 (6.3) | 14 (3.5) | 185 (4.9) | ||
| Native Hawaiian or Pacific Islander | 2 (0.5) | 0 (0) | 2 (0.1) | ||
| White | 352 (85.6) | 347 (87.8) | 3255 (86.2) | ||
| Unknown | 15 (3.6) | 28 (7.1) | 248 (6.6) | ||
|
| |||||
| Comorbidities | |||||
|
| |||||
| Hypertension – N (%) | 343 (83.5) | 336 (85.1) | 3046 (80.6) | .531 | .166 |
| Diabetes – N (%) | 63 (15.3) | 44 (11.1) | 618 (16.4) | .080 | .591 |
| Insulin-dependent diabetes – N (%) | 16 (3.9) | 5 (1.3) | 105 (2.8) | .019 | 0.20 |
| COPD – N (%) | 80 (19.5) | 93 (23.5) | 674 (17.8) | .158 | .416 |
| Heart failure – N (%) | 17 (4.1) | 8 (2.0) | 62 (1.6) | .084 | <.001 |
| Renal insufficiency – N (%) | 79 (19.7) | 59 (15.1) | 622 (16.9) | .087 | .167 |
| Preoperative creatinine – N (%) | 1.22 (.85) | 1.09 (.43) | 1.14 (.57) | .006 | .055 |
| Dialysis– N (%) | 12 (2.9) | 3 (0.8) | 34 (0.9) | .034 | <.001 |
| BMI >30 – N (%) | 110 (26.8) | 99 (25.1) | 1198 (31.7) | .582 | .040 |
| Current smoking – N (%) | 120 (29.2) | 180 (45.6) | 1137 (30.1) | <.001 | .706 |
OR: open repair; COPD: chronic obstructive pulmonary disease; BMI: Body Mass Index
Comparing the complex EVAR patients to the infrarenal EVAR patients, those undergoing repair for a complex AAA were more commonly dialysis dependent (2.9% vs. 0.9%, P<.001), more often had heart failure (4.1% vs. 1.6%, P<.001), and tended towards a higher preoperative creatinine (1.22 vs. 1.14 mg/dl, P=.055). In addition, obesity, defined as a BMI higher than 30 kg/m2, was less common among complex EVAR patients compared to infrarenal EVAR patients (26.8% vs. 31.7%, P=.040).
Operative and anatomical characteristics
Complex EVAR was associated with shorter operative time compared to complex open repair (184 vs. 269 min., P<.001), while taking significantly longer than infrarenal EVAR (146 min, P<.001, Table IIA). Complex EVAR patients had a smaller aneurysm diameter compared to complex open repair patients (5.9 vs. 6.2 cm, P=.015), but not significantly different from those undergoing infrarenal EVAR (5.7 cm, P=.058). In addition, the aneurysm of complex EVAR patients more often extended into the iliac arteries compared to open complex repair (69.7% vs. 43.2%, P<.001), and infrarenal EVAR (52.9%, P<.001). The complex EVAR group included 22 (5.4%) patients with an aneurysm labeled as infrarenal who were treated with the Cook Zenith Fenestrated graft. Among complex AAA patients undergoing open repair, 18.8% had a clamp location above the celiac artery, 45.4% between the superior mesenteric artery and the renal arteries, and 35.9% above one renal artery. A visceral vessel reconstruction during open repair was performed in 27.1% of patients.
Table IIA.
Anatomical and intraoperative characteristics for all study groups
| EVAR complex | OR complex | EVAR infra | p-value | ||
|---|---|---|---|---|---|
|
| |||||
| N=411 | N=395 | N=3778 | Complex EVAR vs. OR | Infra vs. complex EVAR | |
| Operative time – min (sd) | 184 (100) | 269 (108) | 146 (70) | <.001 | <.001 |
| Diameter – cm (sd) | 5.9 (2.6) | 6.2 (1.4) | 5.7 (1.6) | .015 | .058 |
| Indication – N (%) | .074 | .108 | |||
| Diameter | 348 (88.1) | 328 (83.9) | 3304 (88.6) | ||
| Dissection | 2 (0.5) | 1 (0.3) | 28 (0.8) | ||
| Embolization | 2 (0.5) | 1 (0.3) | 20 (0.5) | ||
| Symptomatic | 23 (5.8) | 47 (12.0) | 281 (7.5) | ||
| Thrombosis | 10 (2.5) | 9 (2.3) | 43 (1.2) | ||
| Prior unsatisf. EVAR | 7 (1.8) | 0 (0) | 40 (1.1) | ||
| Prior unsatisf. OR | 3 (0.8) | 5 (1.3) | 12 (0.3) | ||
| Distal extent – N (%) | <.001 | <.001 | |||
| Aortic | 112 (30.3) | 204 (56.8) | 1539 (47.1) | ||
| Common iliac | 171 (46.2) | 137 (38.2) | 1304 (39.9) | ||
| External iliac | 38 (10.3) | 9 (2.5) | 181 (5.5) | ||
| Internal iliac | 49 (13.2) | 9 (2.5) | 242 (7.4) | ||
Not surprisingly, complex EVAR patients more often received renal revascularization than those undergoing EVAR for an infrarenal AAA (30.4% vs. 4.1%, P<.001, Table IIB). No difference existed in main body device used between complex and infrarenal EVAR patients (P=.121).
Table IIB.
EVAR specific intraoperative characteristics
| EVAR complex | OR complex | EVAR infra | p-value | |
|---|---|---|---|---|
|
| ||||
| N=411 | N=395 | N=3778 | Infra vs. complex EVAR | |
| Acute conversion – N (%) | 3 (0.7) | - | 21 (0.6) | .506 |
| Access – N (%) | .100 | |||
| Attempted percutaneous | 5 (1.2) | - | 33 (0.9) | |
| Bilateral cutdown | 277 (67.4) | - | 2441 (64.7) | |
| One groin cutdown | 23 (5.6) | - | 348 (9.2) | |
| Percutaneous bilateral | 106 (25.8) | - | 950 (25.2) | |
| Renal revascularization – N (%) | 125 (30.4) | - | 156 (4.1) | <.001 |
| Lower extrem revasc – N (%) | 19 (5.5) | - | 138 (4.2) | .247 |
| Access vessel repair – N (%) | 42 (10.2) | - | 284 (7.5) | .052 |
| Hypogastric embolization – N (%) | 27 (6.6) | - | 248 (6.6) | .997 |
| Main body device – N (%) | .121α | |||
| Cook Zenith | 72 (17.5) | - | 795 (21.0) | |
| Cook Zenith Fenestrated | 84 (20.4) | - | 0 (0) | |
| Cook Zenith Renu | 3 (0.7) | - | 39 (1.0) | |
| Endologix Powerlink | 26 (6.3) | - | 292 (7.7) | |
| Gore Excluder | 95 (23.1) | - | 1281 (33.9) | |
| Lombard Aorfix | 0 (0) | - | 2 (0.1) | |
| Medtronic AneuRx | 1 (0.3) | - | 7 (0.2) | |
| Medtronic Endurant | 95 (23.1) | - | 1130 (29.9) | |
| Medtronic TALENT | 1 (0.2) | - | 18 (0.5) | |
| TriVascular Ovation | 4 (1.0) | - | 36 (1.0) | |
| other | 26 (6.3) | - | 149 (3.9) | |
| not documented | 4 (1.0) | - | 29 (0.8) | |
analysis did not include patients receiving a Cook Zenith Fenestrated endograft.
Postoperative outcomes
Postoperative outcomes are detailed in Table IIIA. Mortality within 30-days was significantly lower after complex EVAR compared to complex open repair (3.4% vs. 6.6%, P=.038). Similarly, deterioration of renal function (2.3% vs. 9.5%, P<.001) and new dialysis requirement (1.3% vs. 6.1%, P<.001) occurred less frequently after complex EVAR than complex open repair. In addition, complex EVAR was associated with lower rates of ischemic colitis (1.0% vs. 4.6%, P=.002), myocardial infarction (0.7% vs. 4.3%, P=.001), pneumonia (1.2 vs. 7.6%, P<.001), prolonged ventilator dependence (1.9% vs. 14.4%, P<.001), reintubation (2.2% vs. 9.4%, P<.001), wound dehiscence (0.2% vs. 3.0%, P=.001), shock (0.7% vs. 2.8%, P=.031, respectively), return to the operating room (5.4% vs. 13.9%, P<.001), and postoperative blood transfusions (16.3% vs. 78.7%, P<.001). Also, length of ICU stay and hospital stay were significantly shorter for those undergoing complex EVAR compared to complex open repair (1.0 vs. 4.7, P<.001; 4.1 days vs. 11.3 days, P<.001, respectively).
Table IIIA.
Postoperative outcomes for all study groups
| EVAR complex | OR complex | EVAR infra | p-value | ||
|---|---|---|---|---|---|
|
| |||||
| N=411 | N=395 | N=3778 | Complex EVAR vs. OR | Infra vs. complex EVAR | |
| 30-day mortality | 14 (3.4) | 26 (6.6) | 57 (1.5) | 0.038 | .005 |
|
| |||||
| Creat rise >2 mg/dl – N (%) | 9 (2.3) | 37 (9.5) | 32 (0.9) | <.001 | .007 |
| Requiring dialysis – N (%) | 5 (1.3) | 24 (6.1) | 21 (0.6) | <.001 | .096 |
| Ischemic colitis – N (%) | 4 (1.0) | 18 (4.6) | 19 (0.5) | .002 | .276 |
| Leg ischemia – N (%) | 6 (1.5) | 7 (1.8) | 49 (1.3) | .725 | .783 |
| Pneumonia – N (%) | 5 (1.2) | 30 (7.6) | 32 (0.8) | <.001 | .447 |
| >48 hour on ventilator | 8 (1.9) | 57 (14.4) | 33 (0.9) | <.001 | .036 |
| Reintubation – N (%) | 9 (2.2) | 37 (9.4) | 51 (1.3) | <.001 | .174 |
| Myocardial infarction – N (%) | 3 (0.7) | 17 (4.3) | 52 (1.4) | .001 | .364 |
| CPR – N (%) | 2 (0.5) | 10 (2.5) | 22 (0.6) | .019 | 1.000 |
| Wound infection – N (%) | 6 (1.5) | 11 (2.8) | 60 (1.6) | .191 | .860 |
| Wound dehiscence – N (%) | 1 (0.2) | 12 (3.0) | 8 (0.2) | .001 | .606 |
| Return to OR – N (%) | 22 (5.4) | 55 (13.9) | 148 (3.9) | <.001 | .161 |
| Pulmonary embolism | 1 (0.2) | 2 (0.5) | 8 (0.2) | .617 | .606 |
| Stroke – N (%) | 3 (0.7) | 3 (0.8) | 9 (0.2) | 1.000 | .106 |
| Sepsis – N (%) | 3 (0.7) | 10 (2.5) | 22 (0.6) | .051 | .731 |
| Shock – N (%) | 3 (0.7) | 11 (2.8) | 14 (0.4) | .031 | .229 |
| Rupture 30-day – N (%) | 0 (0) | 1 (0.3) | 2 (0.1) | .490 | 1.000 |
| Early conversion – N (%) | 3 (0.7) | - | 21 (0.6) | - | 0.655 |
| ≥1 postoperative transfusion | 67 (16.3) | 311 (78.7) | 385 (10.2) | <.001 | <.001 |
|
| |||||
| Any complication – N (%) | 49 (12.0) | 133 (33.7) | 348 (9.2) | <.001 | .077 |
| Any complication – N (%)α | 99 (24.1) | 328 (83.0) | 623 (16.5) | <.001 | <.001 |
|
| |||||
| Hospital length of stay – days (sd) | 4.1 (6.8) | 11.3 (10.0) | 2.9 (5.1) | <.001 | .001 |
| ICU length of stay – days (sd) | 1.0 (2.4) | 4.7 (4.9) | 0.6 (1.7) | <.001 | .003 |
incidence of any complication when postoperative blood transfusions are included
In comparison to infrarenal EVAR, 30-day mortality was significantly higher after complex EVAR (3.4% vs. 1.5%, P=.005). Similarly, complex EVAR was associated with a higher rate of renal function deterioration (2.3 % vs. 0.9%, P=.007), postoperative blood transfusion (16.3%, vs. 10.2%, P<.001), and prolonged ventilator dependence (1.9% vs. 0.9%, P=.036). In addition, ICU length of stay (1.0 vs. 0.6, P=.003), and hospital length of stay (4.1 days vs. 2.9 days, P=.001) were both significantly longer after complex EVAR compared to infrarenal EVAR.
Outcomes of patients receiving the Cook Zenith Fenestrated endograft are shown in Table IIIB. Although not significant, this subanalysis demonstrated that patients undergoing placement of a Cook Zenith fenestrated graft had a similar, if not lower, 30-day mortality rate compared to all other complex EVAR patients (1.2% vs. 4.0%, P=.318). However, patients treated with the Cook Zenith Fenestrated endograft more frequently received blood transfusions postoperatively (25.0% vs. 14.1%, P=.016). Similar to the other complex EVAR patients, low occurrence rates were found for various adverse outcomes, such as renal function deterioration (2.4% vs. 2.2%, P=1.000), ischemic colitis (1.2% vs. 0.9%, P=1.000), leg ischemia (0% vs. 1.8%, P=.354), and pneumonia (1.2% vs. 1.2%, P=1.000). Hospital and ICU length of stay were also comparable to the other complex EVAR patients (4.6 vs. 4.0 days, P=.488; 1.4 vs. 0.9 days, P=.208, respectively).
Table IIIB.
Postoperative outcomes for complex EVAR patients treated with the Cook Zenith Fenestrated graft and those treated otherwise
| Cook Zenith Fenestrated | Other Complex EVAR | P-value | |
|---|---|---|---|
|
| |||
| N=84 | N=327 | ||
| 30-day mortality | 1 (1.2) | 13 (4.0) | .318 |
|
| |||
| Creat rise >2 mg/dl – N (%) | 2 (2.4) | 7 (2.2) | 1.000 |
| Requiring dialysis – N (%) | 2 (2.4) | 3 (1.0) | .284 |
| Ischemic colitis – N (%) | 1 (1.2) | 3 (0.9) | 1.000 |
| Leg ischemia – N (%) | 0 (0) | 6 (1.8) | .354 |
| Pneumonia – N (%) | 1 (1.2) | 4 (1.2) | 1.000 |
| >48 hour on ventilator | 2 (2.4) | 6 (1.8) | .669 |
| Reintubation – N (%) | 3 (3.6) | 6 (1.8) | .397 |
| Myocardial infarction – N (%) | 1 (1.2) | 2 (0.6) | .497 |
| CPR – N (%) | 0 (0) | 2 (0.6) | 1.000 |
| Wound infection – N (%) | 1 (1.2) | 6 (1.8) | 1.000 |
| Wound dehiscence – N (%) | 0 (0) | 1 (0.3) | 1.000 |
| Return to OR – N (%) | 5 (6.0) | 17 (5.2) | .784 |
| Pulmonary embolism | 0 (0) | 1 (0.3) | 1.000 |
| Stroke – N (%) | 1 (1.2) | 2 (0.6) | .497 |
| Sepsis – N (%) | 2 (2.4) | 1 (0.3) | .108 |
| Shock – N (%) | 1 (1.2) | 2 (0.6) | .497 |
| Rupture 30-day – N (%) | 0 (0) | 0 (0) | 1.000 |
| Early conversion – N (%) | 1 (1.2%) | 2 (0.6%) | .499 |
| ≥1 postoperative transfusion | 21 (25.0) | 46 (14.1) | .016 |
|
| |||
| Any complication – N (%) | 10 (11.9) | 37 (11.3) | .880 |
| Any complication – N (%)α | 25 (29.8) | 72 (22.0) | .136 |
|
| |||
| Hospital length of stay – days (sd) | 4.6 (6.5) | 4.0 (6.9) | .488 |
| ICU length of stay – days (sd) | 1.4 (3.5) | 0.9 (2.1) | .208 |
incidence of any complication when postoperative blood transfusions are included
Multivariable analyses
In multivariable analysis (Table IV), open repair for complex AAA was found to be an independent predictor of 30-day mortality (OR: 2.2, 95% CI: 1.1 – 4.4), renal function deterioration (OR: 4.8, 95% CI: 2.2 – 10.5), and any complication (OR: 3.7, 95% CI: 2.5 – 5.5) compared to complex EVAR. When comparing complex to infrarenal EVAR, infrarenal EVAR was associated with favorable 30-day mortality (OR: 0.5, 95% CI: 0.2 – 0.9), and renal outcome (OR: 0.4, 95% CI: 0.2 – 0.9), while no difference was found in the occurrence of any complication (OR: 0.8, 95% CI: 0.6 – 1.2). Given the invasive nature of open AAA repair and the routine need for postoperative blood transfusions, a postoperative transfusion was not included as a complication in this analysis. However, when a blood transfusion is considered a complication, complex EVAR is associated with an increased risk of any complication compared to infrarenal EVAR as well (OR: 0.7, 95% CI: 0.5 – 0.9). Within the complex EVAR group, no differences were found between patients treated with the Cook Zenith Fenestrated endograft and those treated using other grafts in multivariable analysis.
Table IV.
Adjusted associations between treatment groups and outcomes
| 30-day mortalityα | OR | 95% CI | p-value |
|---|---|---|---|
| EVAR complex | Reference | - | - |
| Open complexα | 2.2 | 1.1 – 4.4 | 0.025 |
| EVAR infrarenalβ | 0.5 | 0.2 – 0.9 | 0.014 |
|
| |||
| Renal complicationβ | OR | 95% CI | p-value |
|
| |||
| EVAR complex | Reference | - | - |
| Open complexγ | 4.8 | 2.2 – 10.5 | <.001 |
| EVAR infrarenalδ | 0.4 | 0.2 – 0.9 | .017 |
|
| |||
| Any complicationγ | OR | 95% CI | p-value |
|
| |||
| EVAR complex | Reference | - | - |
| Open complexε | 3.7 | 2.5 – 5.5 | <.001 |
| EVAR infrarenalζ | 0.8 | 0.6 – 1.2 | .304 |
adjusted for: age, gender, obstructive pulmonary disease
adjusted for: age, gender, hypertension, insulin-dependent diabetes, preoperative renal insufficiency, preoperative dialysis, heart failure, obstructive pulmonary disease, obesity, current smoking, symptom status
adjusted for: age, preoperative renal insufficiency, obstructive pulmonary disease, obesity, symptom status
adjusted for: age, gender, insulin-dependent diabetes, preoperative renal insufficiency, obstructive pulmonary disease, obesity
adjusted for: age, gender, hypertension, preoperative renal insufficiency, obstructive pulmonary disease
adjusted for: age, gender, nonwhite race, hypertension, insulin-dependent diabetes, preoperative renal insufficiency, preoperative dialysis, heart failure, obstructive pulmonary disease, obesity, symptom status
Discussion
This study demonstrates that endovascular repair provides a good alternative to open repair for the treatment of complex AAA. In addition to lower 30-day mortality, we found that EVAR was associated with a lower incidence of various adverse outcomes, including acute renal failure, ischemic colitis, return to the operating room, and length of stay. In comparison to infrarenal EVAR, complex EVAR was associated with a significantly increased perioperative mortality risk, as well as a higher frequency of several other adverse outcomes, most importantly an increased incidence of postoperative renal dysfunction.
At 3.4%, the mortality following complex EVAR is comparable to previous reports.22, 32–34 Despite the fact that complex EVAR patients were older and in more frail health than those undergoing open repair, mortality was almost half of that following open repair (3.4% vs. 6.6%). After adjustment for the various health disparities, treatment of a complex AAA through open repair proved to be associated with two-and-half times higher mortality risk compared to EVAR. This is in line with the results of previously conducted studies by Canavati et al. and Tsilimparis et al., which found a similar mortality benefit for fenestrated EVAR.20, 35 In contrast to what has been shown for open repair,36 endovascular complex AAA repair was associated with increased mortality risks over infrarenal EVAR. A difference in operative stress between EVAR for infrarenal and complex AAA, as indicated by the longer operative time, may have contributed to the observed difference in occurrence of adverse outcomes in the perioperative period.
Our results indicated that complex EVAR was associated with lower rates of complications compared to complex open repair. Despite worse preoperative renal function, the avoidance of suprarenal clamping and the resulting renal ischemia led to fewer kidney injuries and fewer patients requiring new dialysis with complex EVAR. This favorable renal outcome of EVAR for complex AAA is in line with previous studies.22, 23 A recent case-controlled study, however, demonstrated a higher frequency of acute kidney injury after complex endovascular repair with similar 1-year results as open repair.37 When comparing absolute rates of postoperative renal dysfunction to prior reports, the occurrence of kidney injuries in this study is relatively low.22, 23, 38, 39 The present results most likely underestimate the actual incidence in our cohort, which is the result of the relative strict definition for postoperative renal dysfunction employed by the NSQIP. In regards to mid-term and late renal outcomes, previous studies have reported good patency results of renal stents and chimneys.13, 25, 26, 38, 40 Although close monitoring of the renal function is required, this further highlights the benefit of EVAR over open repair, particularly for patients with renal impairment.41
Similar to established short-term perioperative benefits of EVAR for infrarenal AAA, the incidence of adverse events such as respiratory and wound complications, ischemic colitis, leg ischemia, myocardial infarction, and return to the operating room were lower for complex EVAR versus open repair. Due to the less complicated postoperative period and invasiveness of procedure, length of stay following complex EVAR was almost one-third of that following open repair. It should be noted that as a result of the exclusion of conversions to open repair, the incidence of adverse outcomes may be relatively low. However, as demonstrated by previous studies, conversion surgery is rare and most conversions are not performed in an acute setting.31, 42 As previously suggested,25, 26 complex EVAR was associated with a higher frequency of postoperative renal dysfunction compared to infrarenal EVAR, although this did not translate into a higher need for dialysis in the postoperative period. This is in contrast to the study by Glebova et al., which showed no difference in renal complications between infrarenal EVAR and fenestrated EVAR using the non-Targeted NSQIP dataset.27 This difference may be related to the fact that the definition for complex EVAR in the present study is based on the specific Targeted NSQIP variable for proximal aneurysm extent, while the definition in the Glebova study was established from billing coding prior to the commercial availability of fenestrated endografts.
Several studies have reported on differences in outcome between chimney and fenestrated grafts. These studies determined that no difference exists in mortality or in renal endpoints between chimneys and fenestrated endografts.33, 43 Unfortunately, we were unable to identify the exact technical approach that was used beyond the type of main body device. Selective analysis of patients receiving the Cook Zenith Fenestrated graft revealed that these patients had a similar, if not lower, mortality rate compared to the other complex EVAR patients. However, this may simply reflect that those treated otherwise have more complex anatomy, and were therefore ineligible for the Cook Zenith Fenestrated graft, which led to a trend towards worse outcomes. Unfortunately we did not have this level of anatomic detail. For other perioperative complications, we found that the Cook Zenith Fenestrated patients had comparable occurrence rates to other complex EVAR patients, including adverse renal outcomes, despite an increased transfusion requirement. This is in line with results from a pooled data analysis on fenestrated stent grafts.33
This study has several limitations. First, since the Targeted Vascular dataset of the NSQIP is gathered through a registry, underreporting of events is possible. Second, we were unable to fully distinguish between treatment approaches in patients undergoing complex EVAR. However, as previously addressed, reports have shown no differences in perioperative outcomes between fenestrated endografts and chimney grafts.33, 43 Third, as evidenced by the lower than expected proportion of complex EVARs undergoing concurrent renal stenting, the capture of this data point was thought to be unreliable and therefore limited our ability to identify snorkel repairs. We believe this is the result of variable reporting of renal stenting based on interpretation of its definition, since NSQIP clinical reviewers are instructed to capture renal stenting for renal artery stenosis. Due to a lack of detail in CPT codes for endovascular procedures, CPT coding could unfortunately not be used for the documentation of visceral vessel reconstruction in EVAR patients. For complex open repair, we found that 27% of patients underwent visceral artery reconstruction, which is similar to previous reports.44 Unfortunately, the exact number of visceral artery reconstructions is not documented in this data set. Fourth, the NSQIP database lacks data on perioperative endoleaks and long-term outcomes, which precluded us from assessing differences in the occurrence of endoleaks and late reinterventions, as well as long-term renal function. This highlights the need for future studies investigating the long-term outcome of EVAR for complex AAA. Also, since we did not have access to postoperative serum creatinine values, we were unable to redefine renal dysfunction or use standardized formulas consistent with previous studies. In addition, due to the novelty of this recently added vascular module, validation studies have yet to be conducted for it. However, the ability of these same nurse reviewers to accurately abstract data from the medical record for the NSQIP in general has been confirmed previously.28–30 Finally, it should be noted that patients were not randomized to undergo open repair or EVAR. Nevertheless, this study provides valuable new data on the operative outcome of complex AAA repair in both the open and endovascular setting, which may add to prospectively conducted research efforts.
In conclusion, this study demonstrates that as a result of advancements in endovascular treatment techniques, EVAR has become a good alternative to conventional open repair for treatment of anatomically complex aneurysms. Complex EVAR has fewer perioperative complications compared to complex open repair, but –in turn– is associated with increased perioperative risks compared to infrarenal EVAR. Further research is warranted to determine whether the favorable outcome of EVAR for complex AAA is maintained during long-term follow-up.
Acknowledgments
Supported by the NIH T32 Harvard-Longwood Research Training in Vascular Surgery grant HL007734.
Footnotes
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