Impact of gender and body surface area on outcome after abdominal aortic aneurysm repair

Association of women-specific size threshold and mortality in elective abdominal aortic aneurysm repair

BACKGROUND

It is unclear whether women derive mortality benefit from early repair of abdominal aortic aneurysms (AAA). The aim of this study was to compare short- and mid-term mortality for women treated at small versus large diameters.

METHOD

Women receiving elective repair of AAA at small (49-54 mm) and large (≥55 mm) diameters from 2008 to 2022 were extracted from the Swedish National Registry for Vascular Surgery (n = 1642 women). The effect of diameter on 90-day, 1- and 3-year mortality was studied in logistic regression and propensity score models. Age, co-morbidities, smoking and repair modality were considered as confounders. Men (n = 9047) were analysed in parallel.

RESULTS

Some 1642 women were analysed, of whom 34% underwent repair at small diameters (versus 52% of men). Women with small (versus large) AAAs were younger (73 versus 75 years, P < 0.001), and 63% of women in both size groups had endovascular repairs (P = 0.120). Mortality was 3.5% (90 days), 7.1% (1 year) and 15.8% (3 years), with no differences between the size strata. There was no consistent association between AAA size and mortality in multivariable models. Sex differences in mortality were almost entirely due to mortality in younger-than-average women versus men (3-year mortality: small AAAs 11.1% versus 7.3%, P < 0.030, or large 14.4% versus 10.7%, P < 0.038).

CONCLUSION

Mortality in women is high and unaffected by AAA size at repair. The optimal threshold for women remains undefined. The higher rupture risk in women should not automatically translate into a lower, women-specific threshold.

Women with large intact abdominal aortic aneurysms remain untreated

OBJECTIVE

A lower elective repair rate among women with abdominal aortic aneurysms (AAAs) has been a consistent finding. Reasons behind this gender gap have not been thoroughly outlined.

METHODS

This was a retrospective multicenter cohort study (ClinicalTrials.gov: NCT05346289) at three European vascular centers in Sweden, Austria and Norway. Patients in surveillance with AAAs were consecutively identified starting from January 1, 2014, until reaching a total sample size of 200 women and 200 men. All individuals were followed for 7 years through medical records. Final treatment distributions and the proportion of "truly untreated" (surgically untreated despite reaching guideline-directed thresholds: 50 mm for women and 55 mm for men) were determined. In a complementary analysis, a universal 55-mm threshold was used. Gender-specific primary reasons behind untreated statuses were clarified. Eligibility for endovascular repair among the truly untreated was assessed in a structured computed tomography analysis.

RESULTS

Women and men had similar median diameters at inclusion (46 mm; P = .54) and at treatment decisions (55 mm; P = .36). After 7 years, the repair rate was lower among women (47% vs 57%). More women were truly untreated (26% vs 8%; P < .001) despite similar mean ages as for male counterparts (79.3 years; P = .16). With the 55-mm threshold, 16% women still classified as truly untreated. Similar reasons for nonintervention were captured for women and men (50% due to comorbidities alone, 36% morphology and comorbidity). The endovascular repair imaging analysis revealed no gender differences. Among truly untreated women, ruptures were common (18%), and mortality was high (86%).

CONCLUSIONS

Surgical AAA management differed between women and men. Women could be underserved in terms of elective repairs: one in every four women was untreated with over-the-threshold AAAs. The lack of obvious gender differences in eligibility analyses could imply unmeasured discrepancies (eg, in disease extent or patient frailty).

The Association Between Body Mass Index and Death Following Elective Endovascular and Open Repair of Abdominal Aortic Aneurysms in the Vascular Quality Initiative

OBJECTIVE

The effect of body mass index (BMI) on post-operative outcomes after abdominal aortic aneurysm (AAA) repair remains poorly defined. The association between BMI and death following elective endovascular aneurysm repair (EVAR) and open aneurysm repair (OAR) of AAA in a large national quality registry is investigated.

METHODS

All elective AAA repairs within the Society for Vascular Surgery Vascular Quality Initiative (VQI; 2010 to September 2021) were reviewed (EVAR, n = 53 426; OAR, n = 9 479). All analyses were conducted separately for EVAR and OAR patients. The primary end points were 30 day mortality and five year survival rates. Study cohorts were divided into World Health Organisation BMI categories (C1 < 18.5, C2 18.5 ≤ BMI < 25, C3 25 ≤ BMI < 30, C4, 30 ≤ BMI < 35, C5 35 ≤ BMI < 40, C6 ≥ 40). BMI was examined as both a categorical and continuous variable. Logistic and Cox proportional hazards regression were used for risk adjustment.

RESULTS

Among EVAR patients, BMI distribution was C1, 1 216 (2%); C2, 14 687 (28%); C3, 20 516 (38%); C4, 11 352 (21%); C5, 3 947 (7%); C6, 1 708 (3%). Class 1, 2, and 6 BMI patients experienced an increased 30 day mortality rate (C1 2.6%; C2 1.3%; C6 1.4% vs. C3 - 5 0.7%; p < .001) and C1 and C2 had correspondingly inferior long term survival (five years: C1 69 ± 3%; C2 79 ± 1% vs. C3 - 6 86 - 88 ± 2%; log rank p < .001). These survival disparities persisted after risk adjustment for multiple confounders. In the OAR cohort, BMI distribution was C1, 280 (3%); C2, 2 862 (30%); C3, 3 587 (38%); C4, 1 940 (21%); C5, 581 (6%); C6, 229 (2%). Crude 30 day mortality rates were increased for both the lowest and highest BMI patients (C1 12%, C6 7% vs. C2 - 5 3 - 4%; p < .001); these differences also persisted in long term survival (five years: C1 71 ± 6%, C6 82 ± 6% vs. C2 - 6 85 - 88 ± 3%; log rank p < .001). In risk adjusted analysis, both low and high BMI OAR patients had an increased 30 day and long term mortality rate.

CONCLUSION

Within the VQI, both the extreme low (< 18.5) and high (≥ 40) BMI groups experienced an increased 30 day mortality rate after both elective EVAR and OAR. By comparison, while the lowest BMI cohort was significantly associated with decreased long term survival after both procedures, the highest BMI group only experienced reduced long term survival after OAR. Based upon this large real world registry analysis of elective AAA repairs, differential metabolic signatures exist within extreme BMI categories, which may inform peri-operative risk stratification and clinical decision making.

Sex-specific criteria for repair should be utilized in patients undergoing aortic aneurysm repair

OBJECTIVE

Female patients are more likely to undergo repair of intact and ruptured abdominal aortic aneurysm (AAA) at smaller aortic diameter compared with male patients. By adjusting for inherent anatomic differences between sexes, aortic size index (ASI) and aortic height index (AHI) may provide an additional method for guiding treatment. We therefore analyzed sex-specific criteria for AAA repair using aortic diameter, ASI, and AHI.

METHODS

We identified all patients who underwent AAA repair between 2003 and 2019 in the Vascular Quality Initiative database. The Dubois and Dubois formula was used to calculate body surface area; aortic diameter was divided by body surface area to calculate ASI. Aortic diameter was divided by height to calculate AHI. Cumulative distribution curves were used to plot the proportion of patients who underwent repair of ruptured aneurysm according to aortic diameter, ASI, and AHI. Multivariable logistic regression modeling was used to identify the association of female sex with perioperative mortality and any major postoperative complication.

RESULTS

We identified 55,647 patients, of whom 12,664 were female (20%). For both intact and rupture repair, female patients were older, less likely to undergo endovascular aneurysm repair, and more likely to have comorbid conditions. Female patients underwent repair at smaller median aortic diameter compared with male patients for intact (5.4 vs 5.5 cm; P < .001) and rupture repair (6.7 vs 7.7 cm; P < .001). However, ASI was higher in female patients for both intact (3.1 vs 2.7 cm/m²; P < .001) and rupture repair (3.8 vs 3.7 cm/m²; P < .001), whereas AHI was higher in female patients for intact repair (3.3 vs 3.1 cm/m; P < .001) but lower for rupture repair (4.1 vs 4.3 cm/m; P < .001). When analyzing the cumulative distribution of rupture repair in male patients, 12% of rupture repairs were performed at an aortic diameter below 5.5 cm. To achieve the same proportion of rupture repair in female patients, the repair diameter was only 4.9 cm. However, when ASI and AHI were used, female and male patients both reached 12% of rupture repair at an ASI of 2.7 cm/m² and an AHI of 3.0 cm/m.

CONCLUSION

Our study provides data to strongly support the sex-specific 5.0-cm aortic diameter threshold suggested for repair in female patients by the Society for Vascular Surgery. The high percentage of patients undergoing rupture repair below 5.5 cm in male patients and 5.0 cm in female patients highlights the need to better identify patients at risk of rupture at smaller aortic diameters.

The long-term implications of access complications during endovascular aneurysm repair

BACKGROUND

Access issues are one of the most common complications of endovascular aneurysm repair (EVAR). However, contemporary rates as well as risk factors for complications and the subsequent impact of access complications on mortality are poorly described.

METHODS

We studied all EVAR for intact abdominal aortic aneurysms without prior aortic surgery in the Vascular Quality Initiative between 2011 and 2018. We studied factors associated with access complications (thrombosis, embolus, wound infection, hematoma, and conversion to cutdown), as well as the interaction with female sex and the impact on survival using multilevel logistic regression and propensity weighting. Multiple imputation was used for missing data.

RESULTS

There were 33,951 EVAR during the study period (91% elective, 9% symptomatic); most cases (70%) involved an attempt at percutaneous access on at least one side, with 30% bilateral cutdowns and 0.1% iliac conduits. There were 1553 patients (4.6%) who experienced at least one access complication. Access complications were almost twice as common in female patients (7.5% vs 3.9%; P < .001). The factors associated with access complications included female sex (odds ratio [OR], 2.7; 95% confidence interval [CI], 2.0-3.6; P < .001), age (OR, 1.05 per 5 years; 95% CI, 1.02-1.1; P < .01), aortouni-iliac device (OR, 1.6; 95% CI, 1.1-2.3; P < .01), smoking (OR, 1.4; 95% CI, 1.1-1.7; P < .01), body mass index of less than 16 (OR, 1.8; 95% CI, 1.3-2.5; P = .001), dual antiplatelet therapy (1.3; 95% CI, 1.02-1.6 P = .03), prior infrainguinal bypass (OR, 1.8; 95% CI, 1.3-2.7; P < .01), and beta blocker use (OR, 1.2; 95% CI, 1.03-1.4; P = .02). Conversion from percutaneous access to open cutdown was associated with higher rates of complications than planned open cutdown (8.6% vs 2.9%; P < .001). In propensity-weighted analysis, percutaneous access was associated with significantly lower odds of access complications in women (OR, 0.6; 95% CI, 0.4-0.96; P = .03). Patients who experienced an access complication had more than four times the odds of perioperative death (OR, 4.2; 95% CI, 2.5-7.1; P < .001), and a 60% higher risk of long-term mortality (hazard ratio, 1.6; 95% CI, 1.2-2.1; P = .001). In addition to death, patients with access site complications had higher rates of other major complications, including reoperation during the index hospitalization (19% vs 1.2%; P < .001), myocardial infarction (3.5% vs 0.7%; P < .001), stroke (0.8% vs 0.2%; P < .001), acute kidney injury (12% vs 3%; P < .001), and reintubation (5.7% vs 0.8%).

CONCLUSIONS

Although access complications are infrequent in the current era, they are associated with both perioperative and long-term morbidity and mortality. Female patients in particular are at high risk of access complications, but may benefit from percutaneous access.

Long-Term Follow-Up of Men Invited to Participate in a Population-Based Abdominal Aortic Aneurysm Screening Program

A screening program for abdominal aortic aneurysm (AAA), inviting 65-year-old men, was started in Stockholm in 2010 (2.3 million inhabitants). The aim was to present a long-term follow-up of men participating in screening, as well as AAA repair and ruptures among nonparticipants. Demographics were collected for men with screening detected with AAA 2010 to 2016 (n = 672) and a control group with normal aortas at screening (controls, n = 237). Medical charts and regional Swedvasc (Swedish Vascular registry) data were analyzed for aortic repair for men born 1945 to 1951. Ultrasound maximum aortic diameter (AD) as well as Aortic Size Index (ASI) was recorded. Participation was 78% and prevalence of AAA was 1.2% (n = 672). Aortic repair rates correlated with high ASI and AD. During the study period, 22% of the AAA patients were treated with the elective repair; 35 men in surveillance died (5.2%), non-AAA-related causes (82.9%) dominated, followed by unknown causes among 4 (11.4%), and 2 (5.7%) possibly AAA-related deaths. Abdominal aortic aneurysm rupture rate was higher among nonparticipants (0.096% vs 0.0036%, P < .001). The low dropout rate confirms acceptability of follow-up after screening. The efficacy is shown by the much higher rupture rate among the nonparticipating men.

Female sex is associated with comparable 5-year outcomes after contemporary endovascular aneurysm repair despite more challenging anatomy

BACKGROUND

Women with abdominal aortic aneurysms less often meet anatomic criteria for endovascular repair and experience worse perioperative and long-term survival.

METHODS

We compared long-term survival, aneurysm-related mortality, and rates of endoleaks and reinterventions between male and female patients in the Endurant Stent Graft Natural Selection Global Postmarket Registry (ENGAGE) using 2:1 propensity score matching.

RESULTS

There were 1130 male patients and 133 female patients, yielding 399 patients after matching (266 male patients, 133 female patients). Female patients were older, with smaller aneurysms, smaller iliac arteries, and shorter, more angulated necks, and they were more often treated outside the device instructions for use (all P < .001). Through 5 years, female patients experienced overall mortality comparable to that of well-matched male patients (34% vs 38%, respectively; hazard ratio, 0.89 [0.61-1.29]; P = .54) and lower aneurysm-related mortality (0% vs 3%; P = .047). Female patients experienced higher rates of any postoperative type IA endoleak through 5 years (10% vs 1%; P < .001) but comparable rates of secondary endovascular procedures (14% vs 16%; P = .40). Female sex was independently associated with significantly higher risk of long-term type IA endoleaks (hazard ratio, 4.8 [1.2-20.8]; P = .04), even after accounting for anatomic factors. No female patient experienced aneurysm rupture during follow-up, and only one female patient underwent conversion to open repair.

CONCLUSIONS

Despite more challenging anatomy, female patients in the ENGAGE registry had long-term outcomes comparable to those of male patients. However, female patients experienced higher rates of type IA endoleaks. Although standard endovascular aneurysm repair remains a viable solution for most women, whether high-risk patients may be better served with open surgery, custom-made devices, EndoAnchors (Aptus Endosystems, Sunnyvale, Calif), or chimneys is worthy of further study.

A Methodology to Quantify the Geometrical Complexity of the Abdominal Aortic Aneurysm

The abdominal aortic aneurysm (AAA) anatomy influences the technical success of the endovascular aneurysm repair (EVAR), yet very few data regarding the aortic tree angles exist in the literature. This poses great limitations in the numerical analyses of endografts, constraining their design improvement as well as the identification of their operational limitations. In this study, a matrix Φ of 10 angles was constructed for the description of the pathological region and was implemented on a large dataset of anatomies. More specifically, computed tomography angiographies from 258 patients were analysed and 10 aortic angles were calculated per case, able to adequately describe the overall AAA shape. 9 dimensional variables (i.e. diameters and lengths) were also recorded. The median and extreme values of these variables were computed providing a detailed quantification of the geometrical landscape of the AAA. Moreover, statistical analysis showed that the identified angles presented no strong correlation with each other while no lateral or anterior/posterior symmetry of the AAA was identified. These findings suggest that endograft designers are free to construct any extreme case-studies with the values provided in a mix-and-match manner. This strategy can have a powerful effect in EVAR stent graft designing, as well as EVAR planning.

Abdominal aortic aneurysms

An abdominal aortic aneurysm (AAA) is a localized dilatation of the infrarenal aorta. AAA is a multifactorial disease, and genetic and environmental factors play a part; smoking, male sex and a positive family history are the most important risk factors, and AAA is most common in men >65 years of age. AAA results from changes in the aortic wall structure, including thinning of the media and adventitia due to the loss of vascular smooth muscle cells and degradation of the extracellular matrix. If the mechanical stress of the blood pressure acting on the wall exceeds the wall strength, the AAA ruptures, causing life-threatening intra-abdominal haemorrhage - the mortality for patients with ruptured AAA is 65-85%. Although AAAs of any size can rupture, the risk of rupture increases with diameter. Intact AAAs are typically asymptomatic, and in settings where screening programmes with ultrasonography are not implemented, most cases are diagnosed incidentally. Modern functional imaging techniques (PET, CT and MRI) may help to assess rupture risk. Elective repair of AAA with open surgery or endovascular aortic repair (EVAR) should be considered to prevent AAA rupture, although the morbidity and mortality associated with both techniques remain non-negligible.

Should Abdominal Aortic Aneurysms in Women be Repaired at a Lower Diameter Threshold?

Abdominal aortic aneurysm (AAA) primarily affects male patients; however, female patients with AAA have a faster rate of aneurysm growth, have higher risk of rupture even at smaller diameters, and have worse outcomes following repair of ruptured and intact aneurysms. Furthermore, early natural history studies and randomized controlled trials evaluating surveillance versus repair in small aneurysms were conducted primarily in male patients. Therefore, there are limited data regarding the ideal threshold for elective repair of AAA in women, either by aortic diameter or by alternative measures. We review the existing literature regarding AAA in women and consider the most appropriate threshold for repair.

Abdominal aortic aneurysm: Sex differences

OBJECTIVE

Abdominal aortic aneurysm (AAA) predominantly affects an elderly male population. Even so, AAA appears more detrimental in women, who experience a higher risk of aneurysm rupture and a worse outcome after surgery than men. Why women are privileged from yet are worse off once affected has been attributed to an effect of sex hormones. This review summarizes the knowledge of sex differences in AAA and addresses the changes in the aneurysm wall from a gender perspective.

METHOD

Standard reporting guidelines set by the PRISMA Group were followed to identify studies examining AAA from a gender perspective. Relevant reports were identified using two electronic databases: PubMed and Web of Science. The systematic search was performed in two stages: firstly, using the terms AAA and gender/sex/women; and secondly, adding the terms "elastin", "collagen" and "vascular smooth muscle cells", in order to filter the search for studies relevant to our focus on the aneurysm wall.

CONCLUSION

Current studies support the theory that sex has an effect on aneurysm formation, yet are inconclusive about whether or not aneurysm formation is dependent on female/male sex hormones or a lack thereof. The studies in women are scarce and out of those most reports primarily address other end-points, which limit their ability to illuminate an effect of sex on aneurysm formation. The complexity of the human menstrual cycle and menopausal transition are difficult to mimic in animal models, which limit their applicability to AAA formation in humans.

Multifactorial risk index for prediction of intraoperative blood transfusion in endovascular aneurysm repair

BACKGROUND

In some institutions, the current blood ordering practice does not discriminate minimally invasive endovascular aneurysm repair (EVAR) from open procedures, with consequent increasing costs and likelihood of blood product wastage for EVARs. This limitation in practice can possibly be addressed with the development of a reliable prediction model for transfusion risk in EVAR patients. We used the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database to create a model for prediction of intraoperative blood transfusion occurrence in patients undergoing EVAR. Afterward, we tested our predictive model on the Vascular Study Group of New England (VSGNE) database.

METHODS

We used the ACS NSQIP database for patients who underwent EVAR from 2011 to 2013 (N = 4709) as our derivation set for identifying a risk index for predicting intraoperative blood transfusion. We then developed a clinical risk score and validated this model using patients who underwent EVAR from 2003 to 2014 in the VSGNE database (N = 4478).

RESULTS

The transfusion rates were 8.4% and 6.1% for the ACS NSQIP (derivation set) and VSGNE (validation) databases, respectively. Hemoglobin concentration, American Society of Anesthesiologists class, age, and aneurysm diameter predicted blood transfusion in the derivation set. When it was applied on the validation set, our risk index demonstrated good discrimination in both the derivation and validation set (C statistic = 0.73 and 0.70, respectively) and calibration using the Hosmer-Lemeshow test (P = .27 and 0.31) for both data sets.

CONCLUSIONS

We developed and validated a risk index for predicting the likelihood of intraoperative blood transfusion in EVAR patients. Implementation of this index may facilitate the blood management strategies specific for EVAR.

A registry-based rationale for discrete intervention thresholds for open and endovascular elective abdominal aortic aneurysm repair in female patients

OBJECTIVE

An evidence-based consensus for a female-specific intervention threshold for abdominal aortic aneurysms (AAAs) is missing. This study aims to analyze sex-related differences in the epidemiology of ruptured AAA to establish an intervention threshold for women.

METHODS

The Dutch Surgical Aneurysm Audit (DSAA) is a compulsory, nation-wide registry of AAA repairs in The Netherlands. All patients with emergency or elective AAA repair between January 1, 2013, and December 31, 2015, were included in the analysis. The main outcomes were age, sex, AAA diameter at time of rupture, and 30-day postoperative mortality.

RESULTS

A total of 1561 ruptured AAA repairs (14.7% women) and 7063 cases of elective AAA repair (13.7% women) were included in the analysis. Women had significantly smaller mean ± standard deviation AAA diameter at time of rupture than men; 70.5 ± 14.4 mm and 78.6 ± 17.5 mm, respectively. In male patients, 8% of ruptures occurred at diameters below the 55 mm intervention threshold. The female equivalent of this eighth percentile is 52 mm. Female patients had significantly higher 30-day mortality after emergency repair, namely, 33% for women versus 24.2% for men, but were also significantly older, mean ± standard deviation age 76.7 ± 7.1 years and 73.9 ± 8.3 years for women and men, respectively. Correcting for age reduced the 30-day mortality risk for women after ruptured AAA repair from 1.53 (95% confidence interval, 1.14-2.04) to 1.27 (95% confidence interval, 0.92-1.73). Outcome after open elective repair was significantly worse for women compared with men, with a 30-day mortality of 7.97% 30 for women and 4.27% for men (P < .01).

CONCLUSIONS

The equivalent of the 55-mm intervention threshold for elective endovascular AAA repair in men is 52 mm in women. The almost doubled mortality risk for elective open repair in women implies that the optimal point for open repair is at higher diameters, very possibly at least 55 mm.