Ruptured AAA: Bridging the Gap Between International Guidelines and Local Clinical Realities

doi:10.21203/rs.3.rs-4705623/v1

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Ruptured AAA: Bridging the Gap Between International Guidelines and Local Clinical Realities

https://doi.org/10.21203/rs.3.rs-4705623/v1

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published 20 Aug, 2024

Read the published version in Langenbeck's Archives of Surgery →

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Background: Treatment of asymptomatic Abdominal Aortic Aneurysms (AAA) presents a clinical challenge, balancing rupture risk, patient comorbidities, and intervention-related complications. International guidelines recommend intervention for specific AAA size thresholds, but these are based on historical trials with limited female representation. We aimed to analyse disease characteristics, AAA size at rupture, and intervention outcomes in patients with ruptured AAA from 2009 to 2023 to bridge the gap between guidelines and local realities. Methods: This single-centre retrospective cohort study analysed electronic health records of patients diagnosed with ruptured AAA, assessing demographics, risk factors, comorbidities, clinical presentation, radiological characteristics, and outcomes. Results: Of 164 patients (41 females, 123 males, median age 73.5), 93.3% presented with abdominal or back pain. The median AAA size at rupture was 8.0 cm in males and 7.6 cm in females. No significant correlations were found between demographic characteristics, risk factors, AAA size, repair modality, and outcomes. Trends show a decline in AAA prevalence and rupture rates, aligning with global health initiatives. Post-intervention survival rates at 30 days were 70.7%, and at 2 years, 65.9%. Conclusion: Evolving AAA trends and improved post-intervention survival rates suggest a critical reassessment of existing intervention recommendations. Adjusting intervention thresholds to larger sizes may be warranted to optimize the risk-benefit ratio.

Abdominal Aortic Aneurysm

Ruptured AAA

AAA Size at Rupture

Mortality Outcomes

AAA Rupture Risk

Treatment of asymptomatic Abdominal Aortic Aneurysms (AAA) often poses a complex clinical dilemma, necessitating a nuanced balance between the risk of rupture, patients' underlying comorbidities, and the potential intervention complications. The decision to electively intervene on AAA becomes more intricate in light of evidence asserting that survival rates, even after treatment, remain lower in patients with AAA compared to their matched populations (1–3). The European Society for Vascular Surgery (ESVS) and the American Society for Vascular Surgery (SVS) recommend elective intervention when AAA reaches a threshold of 5.5 cm in men and 5.0 cm in women (4,5). Four randomised clinical trials were the cornerstone evidence for the development of these guidelines: two large multicentred randomised controlled trials of early open elective surgery versus surveillance, the UK Small Aneurysm Trial (UKSAT) and the American Aneurysm Detection And Management study (ADAM), and two smaller trials of endovascular repair versus surveillance; the Comparison of surveillance vs. Aortic Endografting for Small Aneurysm Repair (CAESAR) Trial, and the Positive Impact of endoVascular Options for Treating Aneurysm early (PIVOTAL) study (6–9). It is pertinent to acknowledge that the inclusion of a limited number of females in these trials has led to a reliance on comparatively weaker evidence for recommendations regarding female patients. The UKSAT reported an aneurysmal rupture rate of 1% per year in the surveillance group, contrasting with a perioperative mortality of 5.6% in the immediate open repair cohort. Similarly, the ADAM study revealed a perioperative mortality of 2.7% in the open repair cohort compared to the rupture rate of 0.6% per year in the surveillance group for small AAAs (4.0 cm to 5.5 cm). These results affirm that immediate repair confers no advantage for small AAAs, irrespective of the chosen modality.

The current indication for intervention in AAAs larger than 5.5 cm is based on historical findings of high rupture risk for large AAA and alarming mortality rates associated with rupture —up to 80% in women and 70% in men (10). ESVS 2011 guidelines indicated the yearly rupture risk escalating from 1% in AAA < 5.0 cm to 33% in aneurysms > 7.0 cm (11). A recent meta-analysis scrutinising rupture rates based on size across 1514 patients from 11 studies indicates a significant departure from previous reports. Parkinson et al. found yearly rupture rates to be 3.5% in AAAs 5.5 to 6.0 cm, 4.1% in AAAs 6.1 to 7.0 cm, and 6.3% in AAAs > 7.0 cm (12). Interestingly, the recently released ESVS 2024 guidelines acknowledge that adjusting this threshold to 6.0 cm may prove safe in the future as more evidence emerges. Their committee has therefore issued a strong negative recommendation for intervening electively on AAA < 5.5 cm and downgraded the recommendations on intervention at the 5.5cm threshold to be a consideration of repair in men (from Class I to Class IIa) as the randomised clinical trials underlying this recommendation only showed that operating on AAA < 5.5 cm is of no added benefit (13).

The lower rupture rates may be attributed to advancements in mitigating risk factors known to precipitate AAA rupture, including the decline in smoking prevalence and improved recognition and management of cardiovascular diseases (14,15). Considering these evolving trends, our retrospective single-centre cohort study aims to investigate the disease characteristics and AAA size at rupture for patients presenting to our regional vascular service at Auckland City Hospital from 2009 to 2023. The study further seeks to correlate these characteristics with patient outcomes, contributing valuable insights to the ongoing discourse on AAA management.

Study Design

This retrospective cohort study investigates the demographic and disease characteristics of patients presenting with ruptured AAA between 2009 and 2023 at Auckland City Hospital. Patients were included from 2009 onwards to improve the accuracy of AAA measurements, as radiological modalities were better utilised during this period. Additionally, the study seeks to correlate these characteristics with patient outcomes. The study utilised electronic health records of patients diagnosed with ruptured AAA during this timeframe.

Study Setting

The study was conducted at Auckland City Hospital, a single-centre tertiary care facility serving as a regional vascular surgery referral centre, and equipped with advanced diagnostic and therapeutic facilities, including a hybrid theatre, for comprehensive management of vascular emergencies.

Data Collection

Patients included in the study are 18 years or older, diagnosed with ruptured AAA between 2009 and 2023, and have complete records. Patients were excluded from the study if they had definite evidence of mycotic rupture of AAA or non-ruptured AAA or if they presented with other aortic pathologies. The following variables were collected: Demographics, including ethnicity, risk factors and comorbidities, clinical presentation, and radiological characteristics of AAA. AAA size at rupture as measured by ultrasound, CTA, or intra-operatively. Interventional data and peri-interventional complications. Mortality at 30 days, 90 days, and two years. Intensive care and inpatient hospital stay duration, and postoperative complications.

Limitations

Limitations of the study include the retrospective design, reliance on electronic health records, and the single-centre nature, which may impact the generalizability of findings. In addition, the size of AAA at rupture was obtained through variable modalities.

Statistical Analysis:

Descriptive Statistics

These provided a comprehensive overview of the demographic and clinical characteristics of patients presenting with ruptured AAA from 2009 to 2023. This included measures of central tendency and dispersion for continuous variables and frequency distributions for categorical variables. Results were expressed as a median ± standard deviation (SD).

Correlation Analysis

Statistical correlations were explored between patients' sex and the size of AAA at rupture. Additionally, the relationship between sex and mortality outcomes was investigated. Similar correlation analyses were conducted with ethnicity as a variable to understand potential disparities in AAA size at rupture and outcomes among different ethnic groups.

Grouping Analysis

Patients were grouped based on AAA size at rupture (< 5.5cm, 5.6-6cm, 6.1-7.0cm, > 7.0cm), and analysis to assess each group's distribution and percentage representation. This grouping allowed for exploration of the impact of AAA size on patient outcomes. In addition, maximum AAA diameter density plots were constructed to visually depict the distribution of AAA sizes at rupture within the cohort. Age density plots were generated to illustrate the age distribution of the patients. Furthermore, Kaplan-Meier estimates of survival were calculated to compare the survival rates of patients with ruptured AAA who survived at 30 days post AAA repair to those of a matched sex, and year of birth in New Zealand. This analysis enabled the assessment of long-term survival trends following intervention.

Descriptive Statistics

In this study, 164 patients (41 females [25.0%] and 123 males [74.0%]) were enrolled, with a median age of 73.5 ± 16.53 (shown in Fig. 1). The ethnic distribution included 122 (74.4%) of European descent, 28 (17.1%) Māori, 11 (6.7%) Pacifica, and 3 (1.8%) of Asian ethnicity. Assessment of risk factors and comorbidities revealed that 53.0% have a history of regular smoking, 67.1% were hypertensive, 12.8% were diabetics, and 49.4% had a cardiac comorbidity. Unsurprisingly, most patients presented with abdominal or back pain (93.3%), 63.4% were hemodynamically unstable, and 5.5% suffered from end-organ dysfunction at presentation. The median size of AAA at rupture was 8.0 ± 1.87 cm in males and 7.6 ± 1.77 in females. Density plot for AAA maximum size at rupture is shown in shown in Fig. 2.

Patients were grouped based on the maximum diameter size at rupture: 3 patients (1.82%) had AAA < 5.5 cm, 17 patients (10.36%) had AAA sized 5.6-6.0 cm, 26 patients (15.85%) had AAA sized 6.1-7.0 cm, 103 (62.80%) had AAA of > 7.0 cm, and 15 (9.14%) had missing AAA size data on electronic records. CTA measured AAA sizes in 64.0% of patients, USS in 28.7%, and intra-operatively in 5.5% of patients. Notably, 18 patients (10.97%) experienced an interval rupture during surveillance, with 5 awaiting custom EVAR, 5 lost to follow-up, 3 declined elective intervention, 3 fell below the threshold for intervention, and 2 deemed unfit for intervention.

Open surgical repair (OSR) was utilised in 136 (82.9%) patients, compared to 17 (10.4%) urgent Endovascular Aortic Repair (EVAR). Intra-operative complications occurred in 45 (27.4%) patients, manifesting as intra-operative cardiac arrest (8.5%), organ laceration (7.9%), torrential bleeding as described by the operator (7.3%), and intra-operative death (3.7%). In included patients, 44 (26.8%) returned to theatre for abdominal closure in 6.7%, to control bleeding in 4.9% of patients and bowel resection for bowel ischemia in 7.9%. Postoperative complications and return to theatre data is shown in Fig. 3.

Overall, the 30 days survival was 70.7%. In the OSR group 75.0% and in the EVAR group 88.2% survived 30 days. No change in survival was observed at 90 days. The 2-year survival rate was 65.85% (n: 108), with 2.43% lost to follow-up. Kaplan Meier survival estimates comparing patients who survived more than 30 days after intervention (n = 116) to the matched New Zealand population (shown in Fig. 4) showed a median survival post AAA rupture of 8.9 years compared to predicted NZ mean survival of 15.7 years (p < 0.001; Hazard ratio 4.38 +/- 0.23).

The median duration of intensive care stay was 3.0 ± 7.12 days, and the median inpatient duration was 11.5 ± 14.16 days. Discharge destinations included home (40.9%), transfer to another hospital (20.1%), a rehab facility (6.7%), and rest home discharge (1.8%).

Correlations Among Variables of Interest

No statistically significant correlations were identified between patients' sex or ethnicity and AAA size at rupture or mortality outcomes. Furthermore, no correlations were observed between risk factors such as smoking and hypertension and size at rupture or patient outcomes. In our patient population, neither the size of AAA at presentation nor the modality of repair yielded a statistically significant correlation with outcomes.

Trends in AAA Prevalence and Rupture Rates:

The observed decline in AAA prevalence aligns with global efforts to improve health literacy and address key risk factors, particularly smoking (16). Historical rates exceeding 5% are now substantially reduced to 1–2% and 1% in smoking females > 70 years old. This trend indicates the success of public health campaigns to mitigate risk factors associated with AAA (17–19). As prevalence rates decline, a consequential decrease in rupture rates results in a significant shift from previous data. In the 1970s, rupture rates were reported to be 40% for AAAs > 6.0cm, which decreased to 9.4% in the 1990s for AAAs 6.0 to 6.9 cm, and a further reduction to 4.1% in AAAs 6.1 to 7.0 cm in recent studies (12,20,21).

Survival Rates post rupture repair:

Interventions for ruptured AAA have shown a gradual yet positive trend, with a noteworthy decrease in mortality rates observed over time. In our study, the 30-day survival rates were 75.0% in OSR and 88.2% in the EVAR group, while the overall 2-year survival rates were 65.9%. These outcomes align with recent studies reporting a 5-year survival of 68.8–71.0% in patients undergoing EVAR for ruptured AAA (22,23). In a recent review including data from IMPROVE and AJAX trials, 30-day survival rates were 64.6% for EVAR and 62.6% for OSR in IMPROVE. At one year, EVAR had a survival rate of 58.9%, while OSR was 54.9%. For AJAX, 30-day survival rates were 79% for EVAR and 75% for OSR. However, at six months, survival rates dropped to 72% for EVAR and 69.5% for OSR (24). These results resonate with our study findings, indicating a modest yet notable improvement in survival outcomes compared to a previous literature review from 1991 to 2006, which reported 51% perioperative survival (25,26). The improved mortality rates and the recognised positive outcomes in high-volume centres indicate that ongoing regionalisation efforts in vascular surgery may lead to even better outcomes for these patients.

Considerations for Intervention Thresholds:

The ongoing success in reducing AAA-related mortality prompts a critical re-evaluation of current international guidelines recommending intervention at a 5.5 cm or lower threshold. The latest ESVS guidelines recognise the changes in AAA trends and intervention outcomes, resulting in amending the wording from "recommending" elective intervention on AAA of 5.5cm to "considering" intervention on AAA at this threshold (13). Our data, reflecting a median size at rupture of 8cm, suggests that the current guidelines may lead to an over-treatment of AAA. This is particularly relevant when considering the competing mortality risks of about 5% in elective repairs (27,28). Furthermore, this study highlights several factors that underscore the need for revisiting intervention thresholds. Firstly, despite international recommendations advising consideration of elective intervention at AAA thresholds of 5.5 cm, only 1.82% of our study population had a ruptured AAA at this size with underlying aortic infection being a possible precipitating factor in 2 of the 3 patients. Secondly, patient factors, including functional status and comorbidities, must be meticulously considered in determining the appropriateness of elective intervention. It is essential to recognise that patients with small AAAs may undergo a significant physiological insult during repair, potentially outweighing the benefits of intervening. Finally, our findings align with existing evidence indicating lower survival rates for patients with AAA, even after repair, compared to matched populations. This underscores the complexity of guiding AAA treatment solely based on aneurysm size and emphasises the importance of considering broader patient factors in decision-making. The observed trends in AAA prevalence, rupture rates, and post-intervention mortality outcomes suggest a potential need for revising current guidelines, prompting consideration for adjusting the elective intervention threshold to a larger size (29–30).

In conclusion, the dynamic nature of AAA trends and improved survival rates post-intervention challenges existing paradigms. A careful reassessment of intervention thresholds is warranted.

Statements

Acknowledgement (optional): No acknowledgement to make.

Statement of Ethics

This study qualifies as an audit-related activity and was approved by the Vascular Surgery Department at Auckland City Hospital, with approval reference number. Patient confidentiality and data security were strictly maintained throughout the study. Written informed consent from participants was not required as this study was granted an exemption by the Vascular Surgery Department at Auckland City Hospital

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

SH: Conceptualization, Data Collection, Writing - Original Draft. TF: Data Analysis, Writing - Review & Editing. RB: Supervision, Writing - Review & Editing.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author, SH, upon request.

References in the text should be identified sequentially using Arabic numerals [in square brackets].

The reference list should include only those publications which are cited in the text, arranged numerically in the order in which they are cited. More information and examples can be found on the Author Guidelines of the respective journal.

No competing interests reported.

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Journal Publication

published 20 Aug, 2024

Read the published version in Langenbeck's Archives of Surgery →

Editorial decision: Revision requested
28 Jul, 2024
Reviews received at journal
25 Jul, 2024
Reviews received at journal
22 Jul, 2024
Reviewers agreed at journal
15 Jul, 2024
Reviewers agreed at journal
15 Jul, 2024
Reviewers invited by journal
13 Jul, 2024
Editor assigned by journal
10 Jul, 2024
Submission checks completed at journal
10 Jul, 2024
First submitted to journal
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You are reading this latest preprint version

Ruptured AAA: Bridging the Gap Between International Guidelines and Local Clinical Realities

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Methods

Study Design

Study Setting

Data Collection

Limitations

Statistical Analysis:

Descriptive Statistics

Correlation Analysis

Grouping Analysis

Results

Descriptive Statistics

Correlations Among Variables of Interest

Discussion

Trends in AAA Prevalence and Rupture Rates:

Survival Rates post rupture repair:

Considerations for Intervention Thresholds:

Statements

Declarations

References

Additional Declarations

Status:

Journal Publication

Version 1