The evaluation of morbidity and mortality in abdominal aortic aneurysm repair patients as related to body mass index

New Measures, Old Conclusions: Obesity Does Not Worsen Outcomes after Elective Abdominal Aortic Aneurysm Repair

Background  The “obesity paradox,” whereby the body mass index (BMI) mortality curve is “U-shaped,” is a well-studied phenomenon in vascular surgery. However, there has been an overreliance on BMI as the measure of obesity, which has shown to poorly correlate with clinical outcomes. Robust measures such as waist-hip ratio (WHR) have been suggested as a more accurate marker reflecting central obesity.

Objectives  The objectives of this study were to evaluate the correlation between BMI and WHR on postoperative morbidity and mortality after elective abdominal aortic aneurysm (AAA) repair.

Methods  Data were collected from the Leeds Vascular Institute between January 2006 and December 2016. The primary outcome was mortality and secondary outcomes included length of stay (LOS) and all-cause readmission. Binary logistic regression, linear regression, and correlation analysis were used to identify associations between BMI and WHR in relation to outcome measures.

Results  After exclusions, 432 elective AAA repairs (281 open surgical repair [OSR] and 151 endovascular aneurysm repairs [EVARs]) were identified to be eligible for the study. The combined 30-day and 4-year mortality was 1.2 and 20.1%, respectively. The 30-day readmission rate was 3.9% and the average LOS was 7.33 (standard deviation 18.5) days. BMI data was recorded for 275 patients (63.7%) and WHR for 355 patients (82.2%). Logistic regression analysis highlighted no association between BMI and WHR with mortality, readmission, or LOS following OSR or EVAR.

Conclusion  The results of this study suggest patients should not be denied treatment for AAA based on obesity alone.

Association Between Body Mass Index and Perioperative Mortality After Repair of Ruptured Abdominal Aortic Aneurysms

OBJECTIVE

The attempt to repair a ruptured abdominal aortic aneurysm carries a significant risk of perioperative mortality. The relationship between body mass index (BMI) and outcomes after repair of ruptured abdominal aortic aneurysms (AAAs) has not been well defined. We report the association of BMI with outcomes after ruptured AAA repair.

METHODS

Patients undergoing ruptured AAA repairs between 2008 and 2017 at 2 tertiary academic centers were included in this retrospective study. Demographics (including BMI), type of repair, length of stay, and admission mortality risk scores were gathered and analyzed using bivariate and multivariate logistic regressions. Adjusted odds ratio (AOR) was reported with 95% CIs and P values from the multivariate analysis. The primary outcome was 30-day mortality. Akaike information criterion (AIC) and c-statistics were used to assess the predictive power of models including physiologic score with or without BMI.

RESULTS

A total of 202 patients underwent repair of ruptured AAA. In bivariate relationship, increased BMI was significantly associated with 30-day mortality. With multivariate analysis, adjusting for demographics, type of procedure, and physiologic score, for each kg/m² increase in BMI, an 8% increase in the likelihood of perioperative mortality (AOR = 1.08, 95% CI: 1.01-1.17; P = .04) was observed.

CONCLUSION

When adjusted for admission risk score, type of procedure, and demographics, obesity was associated with increased 30-day mortality. With BMI as an additional data point, the c-statistics and AIC comparisons indicated that we would have a greater ability to preoperatively estimate mortality after ruptured AAA repair. Consideration could be made to include BMI in future mortality risk scoring systems for ruptured AAA.

The Obesity-associated Risk in Open and Endovascular Repair of Abdominal Aortic Aneurysm

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The rising pandemic of obesity in modern society should direct attention to a more comprehensive approach to abdominal aortic aneurysm (AAA) treatment in the affected population. Although overweight patients are considered prone to increased surgical risk, studies on the subject did not confirm or specify the risks well enough.

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Associated comorbidities inevitably lead to a selection bias leaning towards endovascular abdominal aortic repair (EVAR), as a less invasive treatment option, which makes it hard to single out obesity as an independent risk factor. The increased technical difficulty often results in prolonged procedure times and increased blood loss. Several smaller studies and two analyses of national registries, including 7935 patients, highlighted the advantages of EVAR over open repair (OR) of abdominal aortic aneurysm, especially in morbidly obese population (relative risk reduction up to 47%). On the other hand, two other studies with 1374 patients combined, concluded that EVAR might not have an advantage over OR in obese patients (P = 0.52). Obesity is an established risk factor for wound infection after both EVAR and OR, which is associated with longer length of stay, subsequent major operations, and a higher rate of graft failure. Percutaneous EVAR technique could present a promising solution to reducing this complication.

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EVAR seems like a more feasible treatment option than OR for obese patients with AAA, due to lower overall morbidity and mortality rates, as well as reduced wound-related complication rates. However, there is a clear lack of high-quality evidence on the subject, thus future prospective trials are needed to confirm this advantage.

Obesity is not an Independent Risk Factor for Adverse Perioperative and Long-Term Clinical Outcomes Following Open AAA Repair or EVAR

Objectives: Moderate (body mass index [BMI] ≥30) and morbid obesity (BMI ≥35) is increasing at an alarming rate in vascular surgery patients. The objective of this study was to determine the impact of obesity on perioperative and long-term clinical outcomes following open abdominal aortic aneurysm (AAA) repair or endovascular aneurysm repair (EVAR). Methods: This review includes patients that underwent open AAA repair (n = 403) or EVAR (n = 223) from 1999 to 2009. Specific patient characteristics such as comorbid diseases, medications, and body mass index (BMI) were assessed. Specific perioperative outcomes such as length of stay, myocardial infarctions, and mortality were reviewed. In addition, long-term outcomes such as rates of reintervention, permanent renal dysfunction, and mortality beyond 30 days were also assessed. Results: The incidence of obesity in open AAA patients was 25.3% (documented incidence 1.5%) and for EVAR was 24.6% (documented incidence 4%). Moderate and morbid obesity was associated with longer intensive care unit (ICU) admissions for both open AAA or EVAR patients ( P < .05). However, no significant differences in perioperative outcomes in terms of overall length of stay, myocardial infarction, acute renal failure, wound infections, or mortality were noted between obese and nonobese patients underoing open AAA repair or EVAR ( P > .05). Similarly, moderate and morbid obesity was not associated with significant differences in rates of reintervention, permanent renal dysfunction, and mortality beyond 30 days for patients undergoing open AAA repair or EVAR ( P > .05). Conclusions: The results of this study indicate that moderate and morbid obesity are not independently associated with adverse perioperative and long-term clinical outcomes for patients undergoing open AAA repair or EVAR. Therefore, either open AAA repair or EVAR can be accomplished safely in moderately obese and morbidly obese patients.

Pathophysiology and epidemiology of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are found in up to 8% of men aged >65 years, yet usually remain asymptomatic until they rupture. Rupture of an AAA and its associated catastrophic physiological insult carries overall mortality in excess of 80%, and 2% of all deaths are AAA-related. Pathologically, AAAs are associated with inflammation, smooth muscle cell apoptosis, and matrix degradation. Once thought to be a consequence of advanced atherosclerosis, accruing evidence indicates that AAAs are a focal representation of a systemic disease of the vasculature. Risk factors for AAAs include increasing age, male sex, smoking, and low HDL-cholesterol levels. Familial associations exist and although susceptibility genes have been described on the basis of candidate-gene studies, robust genetic studies have failed to discover causative gene mutations. The surgical management of AAAs has been revolutionized by minimally invasive endovascular repair. Ongoing randomized trials will establish whether endovascular repair confers a survival advantage over open surgery for patients with a ruptured AAA. In many countries, centralization of vascular surgical services has largely been driven by the improved outcomes of elective aneurysm surgery in specialized centers, the widespread adoption of endovascular techniques, and the introduction of screening programs.