Predictive Factors for Mortality following Open Repair of Paravisceral Abdominal Aortic Aneurysm

Abstract

Objective

The use of fenestrated and branched stent graft technology for paravisceral abdominal aortic aneurysms (PAAA) is on the rise; however, its application is limited in the United States to only a few selected centers. The majority of the PAAAs are currently repaired using an open approach. The objective of this study was to determine which patients are at highest risk with open PAAA repair and might benefit most from endovascular repair using fenestrated or branched stent grafts.

Design of the study

Retrospective cohort study.

Setting

American College of Surgeons National Surgical Quality Improvement Program (NSQIP) hospitals.

Subjects

Patients who underwent elective open PAAA repair (n=598) were identified from the 2007–09 NSQIP - a prospective database maintained at multiple centers (>250).

Main outcome measure

Thirty-day postoperative mortality.

Results

The median age was 73 years and 27.6% were females. Thirty-day major morbidity and mortality rates were 30.1% and 4.5%, respectively. Major complications included reintubation (10.0%), sepsis (10.7%), return to operating room (9.2%), new dialysis requirement (5.9%), cardiac arrest/myocardial infarction (4.5%), and stroke (1.2%). On multivariate analyses, 4 predictors of postoperative mortality after open PAAA repair were identified: peripheral arterial disease requiring revascularization or amputation (PAD), chronic obstructive pulmonary disease (COPD), anesthesia time, and female gender. PAD and COPD were present in only 5.2% and 20.4% patients, but were associated with 16.1% and 9.0% mortality rate, respectively. Mortality rate in females was 7.3% in contrast to 3.5% for males (P= .045).

Conclusions

PAD, COPD, and female gender are major risk factors for postoperative mortality following open PAAA repair. Fenestrated or branched stent graft repair may be a more valuable alternative to open repair for patients with one or more of these characteristics who have suitable access vessels.

INTRODUCTION

The majority of infrarenal abdominal aortic aneurysms (AAA) in the U.S. are now treated using an endovascular approach resulting in a significant decrease in postoperative morbidity and mortality over the last decade.¹ The minimally invasive nature of endovascular aneurysm repair allows treatment of a larger population of patients, and results in shorter hospital stays and greater patient satisfaction when compared with open surgery.² Unfortunately, anatomic exclusions remain problematic and current commercially available stent grafts provide no means of maintaining perfusion to critical renal and mesenteric arteries if they are involved in the aneurysmal process, as is seen in approximately 15% of all AAAs.³ Distinct from infrarenal AAAs, these paravisceral AAAs carry greater morbidity and mortality rates and are usually treated with open surgery throughout the country.^{4, 5} In a few specialized centers with access to advanced technology, selected patients with paravisceral AAAs are offered endovascular surgery using fenestrated and branched stent grafts. These custom designed and manufactured prostheses employ side holes or branches to maintain visceral blood flow while excluding the adjacent aneurysm from the circulation.

Though long-term outcomes of fenestrated and branched endovascular aneurysm repair are still uncertain, an increasing experience demonstrates good patient and device-related short-term results.^3–9 With limited availability of this advanced technology and expertise, clinicians now face a predicament of properly selecting patients for fenestrated and branched endovascular aneurysm repair in lieu of open repair. To our knowledge, there are no evidence-based criteria or guidelines to help a clinician decide when to refer patients with paravisceral AAAs to specialty centers for fenestrated or branched stent graft consideration. A reasonable initial approach to this problem is to reserve the fenestrated and branched stent graft treatment for patients that are at high risk for open repair. Single-center studies to date have not elicited preoperative risk factors associated with increased postoperative mortality after open repair of paravisceral AAA due to small sample size.^{4, 5, 10–13} Hence, we used the multi-center, ‘clinical’, prospective National Surgical Quality Improvement Program (NSQIP) datasets to assess the preoperative risk factors for 30-day mortality after elective open paravisceral AAA repair.

METHODS

Dataset

Data were extracted from the 2007, 2008, and 2009 NSQIP Participant Use Data Files (PUF).¹⁴ These are multicenter, prospective databases with 183 (year 2007), 211 (year 2008), and 237 (year 2009) participating academic and community US hospitals, with data being collected on 136 perioperative variables. In NSQIP, a participant hospital’s surgical clinical nurse reviewer (SCNR) captures data using a variety of methods, one of which is medical chart abstraction. The data are collected based on strict criteria formulated by a committee. To ensure the data collected are of a high quality, the NSQIP has developed different training mechanisms for the SCNR and conducts an inter-rater reliability audit of participating sites.¹⁴ The processes of SCNR training, inter-rater reliability auditing, data collection, and sampling methodology have been previously described in detail.¹⁴

Patients

Patients undergoing elective open operation for unruptured paravisceral AAA (abdominal aortic aneurysm involving visceral vessels – mesenteric, celiac, renal) were identified from the NSQIP datasets using the American Medical Association’s Current Procedural Terminology (CPT) code for the procedure – 35091 and International Classification of Diseases (ICD)-9 code 441.4. Type IV thoracoabdominal aneurysms (ICD code 441.7) were not included in our analysis. Preoperative data obtained included demographic, lifestyle, comorbidity, and other variables. Demographic variables analyzed included age, gender, and race. Lifestyle variables studied included a history of smoking (within one year of surgery) and alcohol use (more than two drinks a day in the two weeks prior to surgery). Comorbidities studied included presence or absence of renal disease (dialysis dependence), coronary artery disease [angina within 30 days of surgery, myocardial infarction (MI) within six months of surgery, prior percutaneous coronary intervention (PCI), and prior cardiac surgery], congestive heart failure (CHF), hypertension, peripheral arterial disease (PAD) requiring previous revascularization/amputation, rest pain in lower extremity, history of chronic obstructive pulmonary disease (COPD), neurologic event or disease [stroke with or without residual deficit, transient ischemic attack (TIA), and hemiplegia], diabetes mellitus, chronic corticosteroid use, weight loss (more than 10% in the 6 months prior to surgery), bleeding disorders, and open wound. Other factors considered were American Society of Anesthesiologists’ (ASA) class¹⁵, admission status (from home versus facility), preoperative functional status - ability to perform activities of daily living in the 30 days prior to surgery (independent, partially dependent, totally dependent), dyspnea (none, moderate exertion, at rest), prior surgery within 30 days, do not resuscitate (DNR) status prior to operation, disseminated cancer, and body mass index (BMI). Complete definitions for all the above listed variables have been previously published elsewhere.¹⁴

Preoperative laboratory variables analyzed included blood urea nitrogen (BUN), creatinine, albumin, bilirubin, hematocrit, platelet count, serum glutamic oxaloacetic transaminase (SGOT), white blood cell count (WBC), partial thromboplastin time (PTT), and prothrombin time (PT). NSQIP definitions of normal and abnormal were used to categorize laboratory values as normal and abnormal: missing data constituted a third categorical level, an indicator variable.¹⁶

Intraoperative data analyzed included wound classification (clean, clean contaminated, contaminated, dirty), intraoperative transfusion, operative time, time under anesthesia, visceral revascularization (bypass or replantation of the visceral artery from/to the aorta), and intraoperative complications.

Outcome

The primary outcome of interest was perioperative mortality. Other outcomes analyzed included hospital length of stay, minor morbidity (urinary tract infection or superficial wound infection), and major morbidity. The latter included deep wound infection, organ space infection, wound dehiscence, pneumonia, re-intubation, on ventilator > 48 hours, pulmonary embolus, deep venous thrombosis, renal insufficiency, acute renal failure, stroke, coma, peripheral nerve deficiency, graft/prosthesis failure, cardiac arrest, myocardial infarction, transfusion > 4 units packed red blood cells (PRBC) within 72 hours, sepsis, septic shock or return to the operating room. The NSQIP database captures outcomes through 30 days following surgery, except for hospital length of stay, which is recorded till the patient is discharged.

Statistical analysis

Univariate exploratory analysis was performed using Pearson chi-square test or Fisher's exact test for categorical variables and T or F test for continuous variables. Multiple logistic regression modeling was performed to assess risk factors for perioperative morbidity and mortality. The model selection was based on a stepwise procedure, which alternates between dropping the least significant variable from the model and then re-considering all potential variables for re-introduction into the model until no more variables can be added. A variable that is individually predictive of adverse events may not be selected by the stepwise procedure when adding the variable does not significantly improve the predictive power of the existing model. Both the C statistic and the p-value for the Hosmer-Lemeshow test were obtained to determine if there was a satisfactory fit of the model. All statistical analyses were performed using SAS (Version 9.2; SAS Institute, Cary, North Carolina). P-value<0.05 was considered as significant.

RESULTS

Demographics, comorbidities, and therapy characteristics

In the 2007–09 NSQIP dataset, 598 patients (4.6% of total AAAs in the dataset) underwent elective open operation for unruptured paravisceral AAA. The median age (lower quartile-upper quartile) was 73 years (66–78 years). There were 433 (72.4%) males and 165 (27.6%) females in this dataset.

Thirty-day perioperative mortality rate was 4.5% (n=27). Minor complication rate was 5.5% (n=33) and major morbidity rate was 30.1% (n=180). Fifty-five patients (9.2%) had to be taken back to the operating room within 30 days. Median length of hospital stay (lower quartile-upper quartile) was 7 days (6–10 days).

The demographic characteristics, preoperative risk factors, and laboratory values are listed in Table 1. Post-operative complications are listed in Table 2.

TABLE 1.

PREOPERATIVE AND INTRAOPERATIVE CHARACTERISTICS

Category	Preoperative/Intraoperative variable		N (%)
			598 (100)
Cardiac	Angina within 1 month	Yes	10 (1.7)
	Cardiac Surgery prior	Yes	144 (24.1)
	Congestive heart failure	Yes	4 (0.7)
	Myocardial infarction (within 6 months)	Yes	8 (1.3)
	Percutaneous Coronary Intervention prior	Yes	117 (19.6)
Circulatory	Bleeding disorder	Yes	45 (7.5)
	PAD	Yes	31 (5.2)
	Rest pain in lower extremity	Yes	7 (1.2)
	Wound (Open)	Yes	12 (2.0)
General	Age in years (Median)		73
	ASA Class	1	8 (1.3)
		2	170 (28.4)
		3	311 (52.0)
		4	108 (18.1)
		5	1 (0.2)
	BMI in kg/m2 (Median)		27.7
	Corticosteroid use (chronic)	Yes	14 (2.3)
	Diabetes mellitus	On insulin	42 (7.0)
		On medication	24 (4.0)
	Disseminated cancer	Yes	5 (0.8)
	Do not resuscitate (preoperative)	Yes	3 (0.5)
	Functional status	Partially dependent	10 (1.7)
		Totally dependent	0 (0)
	Hypertension	Yes	514 (86.0)
	Prior operation within 30 days	Yes	5 (0.8)
	Race	American Indian	2 (0.3)
		Asian/Pacific Islander	3 (0.5)
		Black	19 (3.1)
		Hispanic	9 (1.5)
		Unknown	28 (4.7)
		White	537 (89.8)
	Sex	Male	433 (72.4)
		Female	165 (27.6)
	Transition (admitted from:)	Home	583 (97.5)
		Acute care	10 (1.7)
		Chronic care	3 (0.5)
		Others	2 (0.3)
	Weight loss > 10% within 6 months	Yes	11 (1.8)
Laboratory	Albumin	Abnormal	62 (10.4)
		Normal	218 (36.5)
		Unknown	318 (53.2)
	Alkaline Phosphatase	Abnormal	21 (3.5)
		Normal	251 (42.0)
		Unknown	326 (54.5)
	Bilirubin	Abnormal	14 (2.3)
		Normal	251 (42.0)
		Unknown	333 (55.7)
	Blood Urea Nitrogen	Abnormal	231 (38.6)
		Normal	330 (55.2)
		Unknown	37 (6.2)
	Creatinine	Abnormal	101 (16.9)
		Normal	487 (81.4)
		Unknown	10 (1.7)
	Hematocrit	Abnormal	108 (18.1)
		Normal	478 (79.9)
		Unknown	12 (2.0)
	Platelets	Abnormal	108 (18.1)
		Normal	471 (78.8)
		Unknown	19 (3.2)
	Prothrombin time	Abnormal	131 (21.9)
		Normal	298 (49.8)
		Unknown	169 (28.3)
	Partial thromboplastin time	Abnormal	48 (8.0)
		Normal	398 (66.6)
		Unknown	152 (25.4)
	SGOT	Abnormal	27 (4.5)
		Normal	260 (43.5)
		Unknown	311 (52.0)
	Sodium	Abnormal	66 (11.0)
		Normal	518 (86.6)
		Unknown	14 (2.3)
	White blood cell count	Abnormal	50 (8.4)
		Normal	529 (88.5)
		Unknown	19 (3.2)
Neurologic	Hemiplegia	Yes	10 (1.7)
	Stroke with neurologic deficit	Yes	31 (5.2)
	Stroke without neurologic deficit	Yes	24 (4.0)
	Transient ischemic attack	Yes	57 (9.5)
Renal	on Dialysis preoperatively	Yes	1 (0.2)
Respiratory	Chronic obstructive pulmonary disease	Yes	122 (20.4)
	Dyspnea	At rest	4 (0.7)
		On moderate exertion	138 (23.1)
Social	Alcohol intake within last 2 weeks	Yes	35 (5.9)
	Smoking within past year	Yes	253 (42.3)
Intraoperative	Revascularization	Yes	60 (10.0)
	Wound classification	1	554 (92.6)
		2	29 (4.9)
		3	12 (2.0)
		4	3 (0.5)
	Intraoperative PRBC transfusion in units (median)		2
	Anesthesia time in minutes (median)		354
	Operative time in minutes (median)		237

ASA - American Society of Anesthesiologists; BMI - Body mass index; SGOT - Serum glutamic oxaloacetic transaminase; PAD - Peripheral arterial disease with history of previous amputation/revascularization; PRBC - Packed red blood cells

TABLE 2.

POSTOPERATIVE CHARACTERISTICS

Postoperative variables		N (%)
		598 (100)
MAJOR COMPLICATIONS	-
Cardiac	Cardiac Arrest	18 (3.0)
	Myocardial infarction	9 (1.5)
Circulatory	Postoperative PRBC transfusion > 4 Units	20 (3.3)
Graft	Graft/prosthesis failure	8 (1.3)
Infection	Organ space infection	5 (0.8)
	Sepsis	27 (4.5)
	Septic Shock	37 (6.2)
Neurologic	Coma	1 (0.2)
	Nerve deficit	0 (0)
	Stroke	7 (1.2)
Renal	Acute renal failure	35 (5.9)
	Renal insufficiency	27 (4.5)
Respiratory	Pneumonia	51 (8.5)
	Reintubation	60 (10.0)
	Ventilator > 48 hours	83 (13.9)
Return to operating room	Return to operating room	55 (9.2)
Venous thromboembolism	Deep venous thrombosis	11 (1.8)
	Pulmonary embolism	2 (0.3)
Wound	Deep Wound Infection	3 (0.5)
	Wound dehiscence	9 (1.5)
Any major morbidity		180 (30.1)
MINOR COMPLICATIONS	-
	Superficial wound infection	11 (1.8)
	Urinary tract infection	23 (3.9)
OTHER POSTOPERATIVE PARAMETERS	-
Number of days from operation to death, median (lower quartile-upper quartile)	-	5 (2–13)
Length of stay in days, median (lower quartile-upper quartile)		7 (6–10)
Mortality		27 (4.5)

PRBC - packed red blood cells

Multivariate logistic regression analysis

Preoperative variables significantly associated with postoperative mortality included peripheral arterial disease with history of revascularization or amputation (PAD), chronic obstructive pulmonary disease (COPD), anesthesia time, and female gender (Table 3). The c-statistic for the postoperative mortality model was 0.79, indicating excellent discrimination. The Hosmer-Lemeshow goodness-of-fit test produced a chi square value of 6.28 (P= .6), indicating an excellent calibration.

TABLE 3.

VARIABLES ASSOCIATED WITH POSTOPERATIVE MORTALITY IN THE STEPWISE LOGISTIC REGRESSION ANALYSIS

PARAMETER	ADJUSTED ODDS RATIO	95% WALD CONFIDENCE INTERVAL
Peripheral arterial disease with history of revascularization or amputation	6.58	2.12 – 20.41
Chronic obstructive pulmonary disease	3.17	1.39 – 7.25
Female gender	2.40	1.02 – 5.66
Time under anesthesia in minutes	1.004	1.001 – 1.007

Preoperative variables significantly associated with postoperative morbidity included anesthesia time and intraoperative transfusion (Table 4). The c-statistic for the postoperative morbidity model was 0.66, indicating a modest discrimination. The Hosmer-Lemeshow goodness-of-fit test produced a chi square value of 9.44 (P= .3), indicating an excellent calibration.

TABLE 4.

VARIABLES ASSOCIATED WITH POSTOPERATIVE MORBIDITY IN THE STEPWISE LOGISTIC REGRESSION ANALYSIS

PARAMETER	ADJUSTED ODDS RATIO	95% WALD CONFIDENCE INTERVAL
Intraoperative packed red blood cell transfusion in units	1.10	1.03 – 1.17
Time under anesthesia in minutes	1.003	1.002 – 1.005

Analysis of risk factors

Of the 598 patients in the dataset, 31 patients (5.2%) had PAD while 567 patients (94.8%) did not have PAD. Five of the 31 patients (16.1%) with PAD died after surgery in contrast to 22 deaths among the 567 patients (3.9%) without PAD (P= .001). A major complication after surgery was seen in 48.4% (n=15/31) patients with PAD compared to a rate of 29.1% (n=165/567) in patients without PAD (P= .02).

COPD is defined by NSQIP as emphysema and/or chronic bronchitis resulting in any one or more of the following: (1) Functional disability from COPD (e.g., dyspnea, inability to perform activities of daily living) (2) Hospitalization in the past for treatment of COPD and requiring chronic bronchodilator therapy with oral or inhaled agents. (3) An FEV1 of <75% of predicted on pulmonary function testing. Patients whose only pulmonary disease is asthma, diffuse interstitial fibrosis or sarcoidosis are not included.

In the dataset, 122 patients (20.4%) had COPD while 476 patients (79.6%) did not have COPD. Eleven of the 122 patients (9.0%) with COPD died after surgery in contrast to 16 deaths among the 476 patients (3.4%) without COPD (P= .007). Forty-eight patients (39.3%) with COPD developed a major complication after surgery in contrast to 132 patients (27.7%) without COPD (P= .01).

There were 433 (72.4%) males and 165 (27.6%) females in this dataset. Females had a mortality rate of 7.3% in contrast to 3.5% for males (P= .045). The morbidity rate was, however, not significantly different - 28.5% for females vs 30.7% for males (P= .6).

For survivors, the median (lower quartile – upper quartile) time under anesthesia was 352 minutes (270 –424), while it was 417 minutes (313 – 554) for those who died after surgery (P= .003). Among patients who developed a major morbidity after surgery, the median (lower quartile – upper quartile) time under anesthesia was 406 minutes (311 –480), while it was 340 minutes (262 – 405) for those who did not develop any major postoperative morbidity (P< .001).

Median (lower quartile – upper quartile) intraoperative RBC transfusion was 3 units (1–6) and 2 units (1–3) for those who developed and did not develop a major postoperative morbidity, respectively (P< .001).

DISCUSSION

The minimally invasive surgical revolution came to aortic surgery with Parodi’s landmark report in 1991, triggering a paradigm shift in AAA repair.¹⁷ The obvious benefits of prosthesis delivery through easily exposed remote-access arteries, and the elimination of aortic cross clamping, gave rise to a widespread increase in the use of stent grafts in the years to follow. By 2005, EVAR accounted for 56% of infrarenal AAA operations but only 27% of the perioperative deaths.¹ Overall mortality for elective AAA repair (open and endovascular combined) decreased significantly from 4% to 3.1%, with the 30-day mortality after open repair (4.8%) being markedly higher than EVAR (1.6%).^{1, 18} While mortality associated with infrarenal AAA has decreased over the last decade, mortality after elective paravisceral AAA repair continues to remain high. In the two largest single-center series published to date, perioperative mortality was 2.5% (6/247)⁵ and 5.8% (15/257).⁴ In other single-center reports, perioperative mortality has varied from 0.8% to 6.0%.^{3, 11–13} In our NSQIP analysis presented here, the 30-day mortality was 4.5%, similar to these previous single-center reports. The high death and complication rates associated with paravisceral AAA repair likely are due to the requirement for invasive surgical exposure and the need for extensive arterial clamping. The increased difficulty of paravisceral AAA repair is well known and often reflected as longer operations with more blood loss. Indeed, in our analysis, we found a positive association between increasing operative times and transfusion requirements with the development of major postoperative morbidity.

Clearly, outcomes after open elective paravisceral AAA repair have not improved appreciably over the last decade. Furthermore, as experience with open repair of AAAs declines, outcomes after open paravisceral AAA repair may actually get worse. These realizations have led to a number of creative approaches incorporating endovascular techniques to repair these aneurysms.

Hybrid repairs involve debranching the abdominal aorta using open surgical bypasses to preserve visceral flow and allow for conventional stent graft placement in the paravisceral aorta.²⁰ Morbidity and mortality rates after debranching procedures are not significantly different than those after open surgery, with recent results from North American Complex Abdominal Aortic Debranching (NACAAD) registry demonstrating 10% perioperative mortality.²¹

The chimney, or snorkel technique, is another alternative to open surgery using off-the-shelf commercially available stents and stent grafts.²² With this method, adjunctive stenting creates a channel alongside the main body stent graft to maintain perfusion of vital aortic branches when deployment of the main aortic endograft intentionally covers the ostia of the vital branches.²³ Use of this technique has shown a reduction in perioperative morbidity, however, a significant reduction in mortality has not been shown.²² Some consider this technique primarily a bailout procedure, as the long-term durability of these repairs is unknown.

A more refined approach to paravisceral AAA repair utilizes fenestrated or branched stent grafts.²⁴ Fenestrated grafts have reinforced apertures in the stent graft fabric that are aligned intra-operatively and adjoined to the respective visceral artery orifice with balloon-expandable stent grafts.²⁵ Branched grafts have cuffs that secure the main body stent graft to the bridging stent graft that is separately placed into the visceral artery.²⁶ Both fenestrated and branched endografts are still not approved in the USA outside of specialized research protocols, but results appear promising with perioperative mortality rates close to 1%.^{7–9, 27}

As only few centers across the world are performing paravisceral AAA repair using fenestrated or branched endografts and that too, for a limited number of patients, it becomes imperative that these patients are carefully selected. Patients who are at a relatively higher risk for postoperative adverse events after open paravisceral AAA repair may benefit more from endovascular repair using fenestrated or branched endografts than patients who are at low risk for open repair. With this in mind, we analyzed the NSQIP dataset to assess preoperative factors which are associated with postoperative mortality after open paravisceral AAA repair.

PAD, COPD, female gender, and time under anesthesia were each associated with higher postoperative 30-day mortality after open paravisceral AAA repair. None of the previous single-center studies had found any preoperative factor that was associated with increased risk for postoperative mortality after open paravisceral AAA repair; probably due to relatively less number of patients compared to the current study.^{4, 5, 10–13}

PAD encompasses such disease contributors as tobacco use, diabetes, previous MI, heart failure, hypertension and obesity, and as such, it is not surprising that such patients would be at an increased perioperative risk.²⁸ However, it was still surprising to note the significantly higher perioperative morbidity (48.4%) and mortality (16.1%) after open paravisceral AAA repair amongst patients with PAD compared to those without (29.1% and 3.9%, respectively) PAD. Previous studies on coronary revascularization have shown PAD to be independently associated with adverse postoperative outcomes.²⁹ The worse outcomes of patients with symptomatic PAD may be partly explained by the comorbidities along with less favorable lesion morphologies and anatomic limitations in the access and target vessels. Furthermore, the recently described and still incompletely understood association of PAD with a systemic inflammatory state may further worsen the outcomes of any paravisceral AAA operation.³⁰ Patients with PAD might seem poor candidates for use of fenestrated or branched endografts due to access issues. However, in the Zenith Fenestrated AAA Endovascular Graft multicenter trial, 23% of the total patients had PAD with no reported postoperative mortality or renal failure.⁸ Similarly, the French Multicenter data on fenestrated aortic endografts demonstrated a mortality of 2.0%, with 20% of the patients having PAD.³¹ These data suggest that the difficulties presented by PAD are less of a factor when an endovascular approach is used for the care of these patients. This comparison may be somewhat limited by unavailability of the exact definition used for PAD in the fenestrated trials. Furthermore, it is possible that the PAD patients that underwent fenestrated grafting were selected to ensure adequate access and target vessels. Despite these limitations the difference in mortality rates between open (16.1%) and fenestrated (1–2%) repair is striking and merits further investigation as patients with PAD who have suitable access vessels may benefit from referral to the select centers where endovascular repair for paravisceral AAA is performed using fenestrated or branched endografts.

Around the globe, COPD prevalence and mortality are continuing to rise due to increase in smoking, particularly by women and adolescents.³² Furthermore, its prevalence is higher in surgical patients when compared to age-matched population groups, which is reflected by the fact that one-fifth of the patients in this study had COPD.³³ COPD is a known risk factor for adverse surgical outcomes in general and respiratory complications in particular as it leads to the impairment of mucociliary clearance, increased propensity for arrhythmias, and left ventricular dysfunction.³⁴ In the current study, patients with COPD had significantly higher postoperative morbidity (39.3%) and mortality (9.0%) after open paravisceral AAA repair than patients without COPD (27.7% and 3.4%). These outcomes fare poorly when compared to outcomes after endovascular repair using fenestrated or branched grafts. Specifically, thirty percent of the patients in the Zenith Fenestrated AAA Endovascular Graft multicenter trial,⁸ 40% of the patients in the published French multicenter fenestrated endograft data,⁶ 26% of the patients in the Netherlands fenestrated data⁹ and 62% of the patients in the Cleveland Clinic data³⁵ had COPD with a one to two percent 30-day mortality rate. Thus, given the high risk, patients with COPD and suitable access vessels may benefit from endovascular repair using fenestrated or branched endografts.

The majority of the patients undergoing open paravisceral AAA repair were males, a finding seen in previous studies.³⁶ However, there was a significantly higher association of the female gender with postoperative mortality, but not morbidity, after open paravisceral AAA repair. Historically, the natural history, as well as the management of AAA in women has been associated with worse overall outcomes.^{36, 37} This is likely related to the fact that significant anatomic and biologic differences exist between men and women.^{37, 38} Women with AAA tend to be older than men by about 5 years, have more comorbidities (heart failure, pulmonary disease, hypertension and peripheral arterial disease) and less preoperative optimization.^{38, 39} Women tend to have smaller bodies and arteries and higher incidence of cerebrovascular and iliac occlusive disease.³⁸ Such anatomic differences may lead to increased technical limitations in the performance of both open and endovascular operations and may lead to compromised results. However, outcomes after use of fenestrated or branched endografts may be relatively superior to open repair as demonstrated in the Zenith Fenestrated AAA Endovascular Graft multicenter trial, as well as data from the Cleveland Clinic and Netherlands where 20%, 18%, and 13% of the patients, respectively, were females with 1% or less mortality.^{8, 9, 35} Thus, females with adequate access vessels may benefit from repair using fenestrated or branched endografts.

Our finding linking time under anesthesia with elevated postoperative 30-day mortality cannot be easily translated to a preoperative recommendation for the choice of an open versus endovascular approach. Longer anesthesia times probably reflect difficult patient anatomy, the added complexity of redo operations and the occurrence of intraoperative complications; however, time under anesthesia may also be influenced by the severity of the patient’s comorbidities and corresponding need for additional monitoring, or simply each individual operating team’s pace of work. Thus, it is likely that anesthesia time is a consequence of the overall challenge each individual patient presents to the operating team and further interpretation is difficult based on the data available from the database.

In spite of its many strengths, this study has some limitations. Variables analyzed were limited to those recorded by NSQIP. Despite the dataset being fairly comprehensive with more than 50 preoperative variables analyzed, information on preoperative stress test, echocardiography, arrhythmia, electrocardiogram, and glomerular filtration rate was not available. Anatomic data such as aneurysm diameter and rate of growth, presence of symptoms due to the aneurysm, presence of left ventricular dysfunction, and duration or level of clamp placement were also unavailable. Furthermore, the reason for return to the operating room, the incidence of postoperative mesenteric and spinal cord ischemia, reason for return to the operating room, and data on hospital and surgeon volume were also not available from the NSQIP database. While the generalizability of these findings may be restricted to hospitals participating in NSQIP, more than 25% of hospitals across the U.S. where AAA repairs are performed are enrolled in NSQIP.⁴⁰ Lastly, NSQIP does not record outcomes beyond 30 days and so evaluation of long-term outcomes using these data is not feasible.

To conclude, PAD, COPD, and female gender are significant risk factors for increased postoperative mortality following open paravisceral AAA repair. Fenestrated or branched stent graft repair may be a valuable alternative to open repair for patients with one or more of these characteristics.