1. Introduction

Abdominal aortic aneurysm is a chronic and potentially lethal pathology with enlargements of the abdominal aorta beyond its standard size and commonly more than 1.5 times its normal diameter. The condition is likely to lead to rupture, and this is a hazardous complication that leads to high morbidity and mortality. In patients with AAAs, the aneurysm is usually undiagnosed and discovered accidentally during imaging for other unrelated pathologies. The mild symptoms typically involve a pulsating tummy mass, abdominal pain, or back pain. Abdominal aortic aneurysm is strongly associated with age, smoking, male gender, hypertension, family history, and other hereditary factors. In clinical practice, AAA focuses on monitoring for small aneurysms with a surgical intervention for those AAA that have grown in size or are referred to as significant or have symptoms that warrant it to avoid rupture [1].

Two primary surgical approaches are employed for abdominal aortic aneurysm repair: it is subdivided into endovascular aneurysm repair (EVAR) and open repair (OR) [2]. EVAR is a minimally invasive form of aneurysm repair involving stent graft placement via a percutaneous route, usually from femoral arteries. This method does not require a giant abdominal incision and has become preferred due to its minimally invasive nature, short period of hospital stay, and practically no perioperative complications. On the other hand, OR includes the use of an open surgical procedure that involves incision of the abdominal wall so that a synthetic graft replaces the sick part of the aorta. OR has been the procedure of Choice for the last 30 years, but it entails higher perioperative risks, more extended hospital stays, and a more protracted recovery period than EVAR [2].

However, controversy persists concerning what questionnaire suggests the application of EVAR as a better and more secure than OR. In many trials comparing EVAR with conventional open surgical repair, it has exhibited lower perioperative mortality and faster rehabilitation. However complications like endoleak, device migration, and routine life-long monitoring and re-intervention are distinctive. However, paper II indicated that OR has better durability, providing lower reintervention rates. Still, its perioperative mortality rate is high, especially among patients with comorbid diseases and higher perioperative morbidity (3). The variation in the results of the various studies has continued to spur the research in a bid to determine the most appropriate situation for the dispensation of each treatment.

Discrepancy regarding the mortality and morbidity between EVT and OR is perhaps most noticeable in the existing literature (4). Overall and more importantly, perioperative mortality is lower when EVAR is used, particularly among patients with high-risk factors. However, there is evidence that with long-term follow-up, it is nearly equivalent, and some data shows increased aneurysm-related mortality/ reintervention in the EVAR group. Morbidity outcomes offer a similar picture of a broad range of services with high rates of low and high-severity procedures. One significant advantage of EVAR is that it minimises the number of operative complications during the per-operative period, such as pulmonary and cardiovascular complications. However, technical factors unique to EVAR, such as endoleaks and access-related complications, add a twist to its long-term picture. Conversely, OR is inherently more complex and ties patients to substantial perioperative risks while, for lack of a better phrase, getting more bang for the buck regarding aneurysm exclusion and surveillance (5).

Thus, the need to integrate existing findings on this topic cannot be overemphasised. Decisions relating to AAA repair have significant consequences for the patient, process efficiency, and system costs. Clinicians should evaluate each approach's short- and long-term implications in the oncology patient population, considering patient characteristics, anatomic features of the aneurysm, and life expectancy (6). Besides, most surgical procedures and related devices are still developing, requiring periodic evidence assessment to ensure that practice matches research. A realistic comparison of the EVAR and OR procedures results will serve as a valuable tool in the therapeutic strategy's decision-making, developing guidelines, and counseling with patients (6).

Therefore, this study aims to give a comparative analysis of mortality and morbidity in patients with EVAR and OR techniques for repairing abdominal aortic aneurysm. As such, it examines different categories of AKI, including perioperative, short-term, and long-term, to identify each category's strengths and weaknesses. Through reviewing these consequences, the study aims to present a review of previous research, define the conditions that make it possible to apply one of the approaches or another, and provide recommendations for clinicians. Third, it underlines the importance of applying personalised treatment approaches based on the patient factors and the characteristics of surgeons and hospitals (7).

The principal or immediate risks reside in the AAA management in the perioperative period, which is considered the most vulnerable in complicated evolution. Indeed, Choong et al. clarified EVAR's role in this regard and noted significantly lower perioperative mortality and morbidity compared to OR. This is especially so given the reduced safety margins in elderly and other high-risk patients who are likely to experience significant physiological insults in the course of open surgery (8). Nevertheless, EVAR's early and late results are still matters of research interest. Overall, EVAR patients have lesser length of stay, fewer hospital days, and similarly shorter time to resume their normal activities; however, the cost-effective outcome in terms of long-term management of the aneurysm is conditioned on the durability of the endograft, shrinkage of the aneurysm sac; and the occurrence of secondary complications (9).

On the other hand, OR is considered the gold standard in AAA management because of its durability and competence in managing aneurysmic conditions. Endoleaks and migration, commonly associated with the device, have not been observed in terms of long-term benefits. However, the related high perioperative risk factors of OR, such as respiratory failure, cardiac events, renal problems, and wound infection, persist, especially among the elderly or patients with complicated diseases. These risks emphasise the need for pre-operative risk assessment to improve outcomes (10).

2. Methods

2.1 Study Design and Protocol Registration

This meta-analysis was conducted under the guidelines of the preferred reporting items for systematic reviews and meta-analysis (PRISMA). The current study was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO) to minimise the risk of bias. The idea was to compare the effectiveness of endovascular aneurysm repair (EVAR) with open surgical repair (OR) for abdominal aortic aneurysms (AAA) and to address significant concerns, including the impact of selection bias and confounding factors.

Surgical suitability bias was another factor of concern as baseline eligibility for surgery involved factors such as age, co-morbidities, and aneurysm morphology, which could skew the parison between EVAR and OR. In selecting the studies, an effort was made to choose those that provided comprehensive details of baseline characteristics and risks. These included pre-operative health status, smoking history, and Charlson co-morbidity index scores, and all were considered to minimise confounding when synthesising the data.

Subgroup analysis was built into the study design to examine how simple patient characteristics might affect surgery results. In addressing methodological aspects and systematically controlling for the potential sources of interference, the study maintained the applicability of the comparison outcomes of two techniques of EVAR and OR within the sphere of the patient's characteristics and surgical accessibility.

2.2 Eligibility Criteria

2.2.1 Inclusion Criteria:

• • The electronic databases searched were Pubmed, Embase, Cochrane Library and Scopus up to July 2015 to identify systematic reviews and primary studies comparing the outcomes of endovascular aneurysm repair (EVAR) and open repair (OR) for abdominal aortic aneurysms (AAA).
• • Studies evaluating at least one of the following outcomes: mortality (perioperative, 30-day, 90-day, or long-term) or morbidity (e.g., cardiac, pulmonary, renal, or access-related complications).
• • Randomised controlled trials, cohort studies and case-control studies published in scientifically indexed peer-reviewed journals where full texts are available.
• • Studies define and describe study participants in terms of demographic and clinical variables, smoking status and ASA scores, and the presence of comorbid conditions.
• • English-language publications are available online.

2.2.2 Exclusion Criteria:

• • Studies reporting outcomes of only EVAR or OR without comparative analysis.
• • Studies that did not present the patients' characteristics at the beginning of the research or the studies that did not report the surgical fitness indicators.
• • Investigations dealing with children or subjects other than people of a certain age.
• • Letters to the editor, commentaries, brief reports, case reports and conference proceedings where no data was collected.

This strategy focused on identifying studies that used adjustments for differences in results because of surgical fitness levels; these adjusted for confounders.

2.3 Search Strategy

An extensive literature-searching methodology was designed to identify studies pertaining to the comparison of EVAR with OR for the management of AAA. The search was performed in PubMed, Embase, and the Cochrane Library, and there were no restrictions on the publication type or year up to January 2025. The keywords used were endovascular aneurysm repair, open surgical repair, abdominal aortic aneurysm, mortality, and morbidity. With these terms, Boolean operators AND and OR and medical subject headings (MeSH) were also incorporated into the searches to increase the precision and recall of the searches. To achieve specific study objectives, filters were used to limit articles to human participants, using the English language and involving only adults.

In addition, reference lists of articles included in the studies and other systematic reviews were searched by hand to identify any other relevant studies. Deduplicate records were performed using reference management software. Titles and abstracts were screened and selected by two of the authors according to the applicable criteria, and the cases of divergence were discussed with the third author.

To reduce the results' publication bias, the analysis included both RCTs and high-quality observational studies. In addition, works were selected if they contained the data concerning initial patients' characteristics, inclusion criteria for surgical treatment, and outcomes, which allowed for the consideration of disturbing factors such as the recipients' fit for surgery.

2.4 Study Selection Process

To enable the comparison of EVAR and OR for abdominal aortic aneurysms, the present study systematically selected quality studies for use in the analysis. Firstly, relevant references were identified, and then the cross-checked and duplicated were excluded by using reference management software. The titles and abstracts of all the articles that were located were reviewed for relevance by two independent reviewers. Any disagreement among the reviewers was settled through a discussion or by consultation with another reviewer with a view to reaching a consensus.

Articles of possibly relevant papers were then identified and screened against specific inclusion and exclusion criteria. To reduce the special type of selection bias, preference was given to those studies that described patients' characteristics in terms of demography, co-morbidity, and fitness for surgery. Particular emphasis was placed on trials that stated and/or demonstrated comparability of the EVAR and OR groups at baseline or controlled for potential confounders in the statistical models. This would ensure that if differences existed in the outcomes, then they could be attributed to the surgical intervention and not other patient attributes.

Only those observational studies, where sufficient details of the selection of participants and statistical control measures were available, were included in the analysis. Those studies that were poorly described in terms of methodology, patient randomisation, treatment, or results were also excluded. After removing or excluding any survey, the list of final studies to be included was finalised for meta-analysis in tabular form. This process of PICO made it possible to have the best evidence that served the analysis well during the research process.

2.5 Data extraction

Information from the selected resources was extracted systematically using a structured format to enhance inter-observer reliability. The following details were extracted from each included study:

1. Patient demographics:

• • Age, sex, and smoking history.
• • Co-morbidities such as hypertension, diabetes, and cardiac disease.
• • Surgical risk, namely the ASA scores, frailty status and CCI.

2. Aneurysm characteristics:

• • Diameter, rupture status (intact or ruptured), and other characteristics referring to the size and position of the aneurysm (e.g., the length of the neck, the angle at which it is located).

3. Outcomes:

• • They class of events included 30-day mortality, myocardial infarction, acute renal failure, as well as other significant adverse events.
• • Late results include overall survival and re-operations rate.
• • Generated measures of postoperative recovery such as time spent in the hospital and quality of life.

4. Procedure-specific complications:

• • For EVAR: Endoleaks, graft migration, and aneurysm sac expansion.
• • For OR: Wound infections, pulmonary complications, and extended ventilation requirements.

5. Data collection process:

• • Further, two reviewers performed data extraction to avoid inter-observer variation.
• • Inter-observer discrepancies were discussed and decided either by mutual consensus or consultation with another reviewer.
• • All authors of studies where data was missing were followed up for the missing information.

Such a broad and exclusive data extraction process was followed to ensure that high-quality and reliable data were used in conducting the meta-analysis.

2.6 Risk of Bias Assessment

To help minimise bias, two authors conducted the risk of bias assessment individually following the standard instruments. In the case of RCTs, the Cochrane Risk of Bias Tool was used to assess selection, performance, detection, attrition, and reporting bias against seven criteria. In observational studies, the Robins/I method of risk of bias tools was used, focusing on bias resulting from the confounding factor, participant selection, measurement of the intervention carried out and the reporting of results.

In order to minimise the bias due to the selection of patients, the effort was made to focus only on those studies which mentioned the criteria used for allocation, including surgical resectability, co-morbidities and anatomical suitability for EVAR or open surgical repair. The control variables included in MASG were ASA scores, frailty indices, presence or absence of co-morbidities, and effect on surgery outcomes.

The inter-observer variability in bias assessment was addressed by consensus or referral to a third reviewer. To aid in presenting the bias ratings and confounding assessments, tables and graphs were developed to make the paper more comprehensive and methods sound.

2.7 Statistical analysis

Depending on this, various statistical analyses were employed; however, conventional meta-analysis analysis techniques were employed for this meta-analysis. A random effect or fixed effect model was used based on the results of heterogeneity tests. In order to compare the results, the random-effects model was used since there is much heterogeneity. In contrast, the fixed-effects model was used since there is less heterogeneity between the studies.

Outcome measures included:

Odds Ratios (ORs): For binary data, it is definable in terms of success, for example, postoperative mortality and complication rates.

Hazard Ratios (HRs): Sought for observations relating to long-term mortality.

Mean Differences (MDs): They are used for metric scaled measurements; for instance, they are used in the observation of the duration of hospital stay or length of stay and other postoperative periods.

Consistency between studies was assessed using the Cochrane Q test and the between-study or Standardized Mean Difference (I²) to determine the amount of variance that may be attributed to between-study differences instead of chance. Any value of I² >50% was considered acceptable to indicate heterogeneity.

In order to reduce patient selection bias for secondary analysis, patient factors that may affect surgery outcomes, including ASA scores, frailty indices, and co-morbidities, were considered. Overall, trials with ineffective blinding of the participants or care providers, as well as no proper account for other important confounding factors, were considered excluded in further sensitivity analyses to increase the validity of the study.

All statistical analysis was performed using specific software with an alpha level of 0.05 throughout the study. To display the pooled estimates, the forest plots were made and outcomes of the EVAR and OR were compared based on the impact of the patient's fitness on surgery.

3. Results

3.1 Study Selection

The criteria for study selection for this meta-analysis were developed with specific and sensitive features in mind to yield a pool of high-quality comparative studies that focused on the outcomes of EVAR in comparison to OR of abdominal aortic aneurysms. This was done in line with the defined study inclusion criteria to limit the research to only worthy and relevant studies, hence providing a synthesis of the included articles on mortality morbidity and other clinically related events.

The following online databases were searched: PubMed, Embase, the Cochrane Library, and other databases of completed clinical trials. The search was conducted for the articles from the beginning of their appearance until the present, and the sources in English only. The medical subject headings used in the search thesaurus and keywords included Endovascular repair, Open repair, Abdominal aortic aneurysm, Mortality, and Morbidity. Boolean operators and filters, which help to narrow search results, were chosen to increase the relevance of results.

The primary search produced 2,456 articles, then exported to a reference manager to organise and filter out duplicates. After deduplication, the dataset contained 1,862 patients' records. Two authors reviewed the titles and abstracts of cultured papers independently according to the previously formulated inclusion-exclusion criteria. Only trials that compared exclusively EVAR and OR for AAA and provided at least one of the outcomes of interest, including mortality rates (perioperative, short-term, or long-term) or morbidity rates in the form of cardiovascular, pulmonary or renal complications, were also included. At this stage, non-comparative studies, literature reviews, conference proceedings, editorials, and any analysis that did not have an outcome related to the two comparisons were eliminated.

In the identified sample of 1,862 records, 247 articles were deemed potentially relevant and proceeded to full-text analysis. This was done meticulously, ensuring that the studies came out clearly from the review and that their eligibility was confirmed to be part of the phase in consideration. Meta-analyses of studies that examined populations not representative of AAA patients, with poorly reported outcomes and/or from the same research groups as other excluded studies, were also discarded. The most prominent or current research was used for original or overlapping measures.

After a full-text review of the identified 48 citations, 35 papers were considered for inclusion in the meta-analysis. These included studies with randomised controlled trials (RCTs) and observational studies; this helped include all forms of high-quality evidence. The studies offered information about 15,000 patients, demographic characteristics of the patients, features of their aneurysms, surgical procedures, and results. The three kinds of studies differed in the size of the samples, the methods used, and the length of follow-up, indicating the need to apply random instead of fixed effects models.

To reduce subjectivity and inter-observer variability, the study selection process was performed by two authors independently, with the help of a third author in case of any discrepancy. This text presents a flow diagram demonstrating the selection process of the studies by showing the number of records identified, initially and finally excluded, and those found eligible for analysis.

By conducting such a selective approach to study inclusion, the subsequent meta-analysis was founded on a broad, solid data foundation that allowed for more effective comparisons between EVAR and OR courses and for developing essential conclusions concerning AAA management.

3.2 Baseline Characteristics of Included Studies

The selected papers reported demographic data of the patients, their aneurysms, and the methods used in the treatment of abdominal aortic aneurysms (AAA) through endovascular aneurysm repair (EVAR) and open surgical repair (OR) for the patients. These included patients of different ages, genders, and ethnicities, aneurysm size and location, and surgical techniques and approaches, which provided a solid meta-analysis base.

Patient Demographics

The studies included 15,000 patients, with a median age of 72 years (range: 60–85 years). Out of the pooled patients, the majority were male, around 82 %, considering that AAA is commonly observed in men. Hypertension was reported in 65%, with coronary artery disease in 30%, 18% had diabetes mellitus. The relevant risk factors of AAA are smoking history, of which 75% of patients had, and 40% of the patients had smoking at the time of the intervention.

Aneurysm Characteristics

The study meant that aneurysm diameters were 55-70 mm; even when distal coil embolisation appeared feasible, patients with larger aneurysms were more likely to undergo OR because of anatomic constraints. It dawned on us that among the surgically treated aneurysms, 10% were ruptured, and the other 90% were intact. Specific anatomy factors, including short neck length less than 15mm or NEVR and severe angulation more than 60 degrees, were present more commonly in the EVAR patients, indicating its use in anatomically tricky cases.

Surgical Techniques

EVAR: Each study described the implantation of modular stent grafts delivered through femoral arterial access. Most patients received EVAR with bifurcated stent grafts; the procedure took between 90 and 150 minutes. Local or regional anesthesia was utilised in 60% of patients because it helped to minimise specific short-term complications.

OR: The most used prosthesis was synthetic, but instead of PTFE, ePTFE was common, and Dacron was applied most). The mean operating room time per operation varied between 180 and 240 minutes. All studies described the use of general anesthesia and consistently indicated that intraoperative blood loss in the OR group was significantly higher than in the EVAR group.

Table 1: The differences between the patients' selection, aneurysm, and EVAR and OR procedural features

Here, we begin by describing these baseline differences to specify how patient and aneurysm characteristics affect the surgical approach and support the analysis of findings in this meta-analysis.

3.3 Primary Outcomes

Pooled prognosis of Mortality in EVAR and OR for the treatment of abdominal aortic aneurysm (AAA) was the subject of this meta-analysis. Mortality was analysed across two key timeframes: In-hospital 30-day perioperative Mortality and intermediate-term and late Mortality. These outcomes are essential for evaluating the efficacy and Safety profile of each operative modality and the transient and persistent advantages of EVAR and OR.

30-Day mortality

The 30-day mortality rate is perioperative mortality and can be considered the direct measure of the risks of surgical procedures. A consistent finding observed in the omitted studies was that 30-day mortality rates for EVAR remained lower than those of OR. Crossing through 35 studies, the computed mean 30-day mortality for both groups, with group 1 for EVAR and 2 for OR, was 1.2% and 4.8%, respectively. We attribute these differences to the less invasiveness of the EVAR procedure, less physiological stress, blood loss, and postoperative recovery. Congruent with these studies, EVAR patients frequently received shorter procedural duration and, often, local or regional anesthesia, decreasing overall surgical risk. However, OR, due to the need for GA and more sophisticated surgical approaches, was associated with increased perioperative risk, particularly in elderly patients and those with significant comorbid illness.

Treating subgroup analysis identified severe cardiopulmonary disease patients as benefiting from EVAR most in the way of perioperative mortality. In contrast, the 30-day mortality rates for OR were significantly higher among the elderly and patients with ruptured aneurysms, underlining the factor of selection sensitivity of the surgical results.

Long-Term Mortality Rates

Overall survival was also discussed to determine the longevity of EVAR and OR and whether or not the benefits are long-term. Performing an analysis of mortality based on the EVAR technique application revealed a clear benefit 30 days after the intervention, while further outcomes were less distinct. Pooled long-term mortality of patients in EVAR and OR groups were similar within the follow-up period of 3 to 10 years: 18.2% in the EVAR group and 17.6% in the OR group.

The reasons for such parallelism in long-term mortality rates are explained as follows. For EVAR, the durability of the stent graft becomes an issue with patients experiencing endoleaks, device migration, and aneurysm sac growth requiring secondary intervention. These complications, if left uncontrolled, may result in aneurysm complications that may cause death. Favourably, OR has a more excellent long-term mechanical stability and fewer RIs attributable to the prohibitive exclusion of the aneurysm sac. Nevertheless, the elevations of perioperative mortality may offset long-term advantages in some patients with OR.

Similar to the other outcomes, subgroup analyses were applied, and differences were revealed between the aneurysm characteristics and patients' Ages. Those anatomic subsets, wherein endovascular repair has traditionally been thought to offer a significant advantage over open surgery with regards to stroke risk—specifically patients with short necks or severe angulation—had slightly higher long-term mortality after EVAR because of a higher complication profile. On the other hand, the OR was more advantageous to the youthful and low-risk, complicated aneurysm patients who are less prone to perioperative risks but more likely to benefit from the durable OR.

Table 2: Outcome and findings of Mortality Rates.

3.4 Secondary Outcomes

This meta-analysis compared several secondary morbidity endpoints to give a detailed view of the EVAR and OR in treating AAAs. The above outcomes include perioperative complications, reintervention, length of hospital stay, and quality of life (QoL). It is central to identify these factors as they help to put into perspective the tradeoff between the two procedures beyond mortality.

The type of complications observed in the perioperative period differed between EVAR and OR. Drawing again from table 2, we were able to determine that EVAR was linked with a reduced risk of significant complications, including death, MI, and acute renal Failure. In all the included studies, the overall rate of MI was 1.3% in the EVAR group as opposed to 3.5% in the OR group, while renal failure complicated 2.1% of patients in EVAR and 5.8% in OR patients. The advantage of this type of repair in EVAR is less operative time, minimal blood loss, and hence lesser perioperative morbidity. OR, due to its invasiveness, OR was associated with increased risks of pulmonary complications, infection, and ventilation over 48 hours.

The overall reintervention rate in the EVAR group was also compared with that in the OR group, the difference being statistically significant at long-term follow-up. The reintervention rate for EVAR was 15-20%, primarily because of endoleaks, graft migration, and aneurysm sac enlargement. OR, in contrast, had a reintervention rate of about 5%, meaning that those undergoing open repair had long-lasting repairs. Nevertheless, the reinterventions after EVAR were less extensive; many of these interventions were endovascular instead of another open surgical procedure.

One of the significant benefits of EVAR was reducing the days patients stayed in the hospital. The length of stay of the EVAR patients was 2-4 days, while that of OR patients was 7-10 days. Thus, these data once again confirm the effectiveness of the method used in the surgery and enable early mobilisation and discharge of patients without great demand for medical resources. The patients receiving OR treatment, because of an invasive nature and complicated post-surgical intervention, needed more extended hospital stays and had a slow recovery in general.

Overall, quality of life measurements, using tools like the EuroQol-5D (EQ-5D) and/or Short Form Health Survey (SF-36), were in most cases in favor of the EVAR during the early follow-up period. Short-term benefits of fewer postoperative pain, shorter time to resume daily activities, and enhanced patient satisfaction were seen in EVAR patients within the first 6–12 months of the surgical procedure. However, long-term QoL was similar between the two groups since there was a group of values to report for OR patients after recovery from the initial pre-operative stress.

Table 3: Secondary Outcomes.

3.5 Subgroup and Sensitivity Analyses

In addition to the primary meta-analysis, the analysis included the subsequent subgroup and sensitivity analysis to compare the results of EVAR and OR, considering specific characteristics of the patients, operators, and the treatment. These analyses were meant to improve knowledge of which subpopulations of patients stand to gain the most from each procedure and to determine the reproducibility of the aggregated conclusions.

3.5.1 Subgroup Analyses

Elective vs. Emergent Repairs: In the elective repairs, the 30-day mortality was also lower in the EVAR group than in the OR group (0.9% vs. 2.5%), which supports the idea of doing business with a planned and less invasive procedure. In emergent cases, including ruptured aneurysms, the mortality rate using EVAR was lower, 8.5%, compared with the open surgical repair 20% mortality in the emergent setting indicated it was adequate in high-risk and emergent settings. However, mortality at the latest follow-up in this emergent cohort was higher for EVAR because of adverse events such as endoleak.

Age Groups:  Compared to OR, perioperative mortality decreased by 60% in patients aged 75 and above after receiving EVAR, which remains the preferred solution for elderly, at-risk patients. In patients under 65, OR resulted in similar short-term early outcomes but better long-term effectiveness than the control group for fewer reinterventions.

Aneurysm Size: Although OR seemed to provide a slightly better long-term result (15 vs. 18 % mortality at 5 years), this was because fewer patients died from reinterventions rather than from a better outcome for the aneurysm. In small AA cases (<65 mm), the early outcome of the EVAR looks better, while no big difference has been noted in the midterm results.

3.5.2 Sensitivity Analyses

To assess the robustness of the findings, sensitivity analyses were conducted by:

• Excluding Studies with High Risk of Bias: When we omitted the six sensitive studies due to the high risk of bias, the observations of this meta-analysis were similar. EVAR maintained the benefits of offering significantly lower perioperative mortality and mean hospital days, while OR retained the benefit of fewer reinterventions.
• Restricting to Randomized Controlled Trials (RCTs): Striking the analysis to RCTs (n = 12) made a confident perimeter slightly narrower for mortality outcomes but strengthened the message of the superiority of EVAR in terms of perioperative mortality and the durability of OR.
• Adjusting for Follow-Up Duration: To eliminate biases associated with short-term results, follow-ups of less than 3 years were excluded from the studies. This change also emphasised the equalisation of mortality rates between EVAR and OR in the long term to underline the performance stability of OR.
• Geographic Variation: Similar tendencies were observed in the separate analyses by the North American, European, and Asian series, although the early postoperative benefits of EVAR appeared to be more apparent in the later areas with a higher level of healthcare development.

Table 4: The Subgroup and Sensitivity Analyses.

3.6 Heterogeneity and Publication Bias

Two main limitations, heterogeneity and publication bias, should be examined when conducting a meta-analysis to determine the quality of the pooled analysis. These factors were thus systematically assessed in this meta-analysis of endovascular aneurysm repair (EVAR) and open surgical repair (OR) for abdominal aortic aneurysm (AAA) to establish variability across the studies as well as possible bias.

3.6.1 Sources of Heterogeneity

The variation that is observed in study effects and that cannot be explained by random factors. This work considered sources of heterogeneity across the compared studies affecting the pooled estimates of mortality, morbidity, and similar outcomes.

Study Design:

Variability was associated with such factors as differences between RCTs and observational studies. Concerning workload, RCTs presented fewer complications due to the rigid setting, whereas observational studies represented actual clinic practice and showed a more significant variability of results.

Patient Characteristics:

These findings demonstrate that subgroups based on patient characteristics in terms of age, sex, and co-morbidities grossly contributed to heterogeneity. For example, observation of a population aged 60 years and older or displaying a higher CCI in the cohorts was associated with worse perioperative outcomes.

Aneurysm Characteristics:

Outcomes were influenced by aneurysm size, rupture status, and anatomical characteristics (AC). Several works specialised in emergent repairs (ruptured AAA)… those compared with controls exhibited more significant mortality and morbidity profiles, especially OR.

Follow-Up Duration:

Mortality and reintervention rates were significantly affected by short- and long-term follow-up. Several trials with extended follow-up indicated that EVAR had higher reintervention rates and OR offered superior midterm outcomes.

Geographic and Institutional Factors:

Surgical competency, healthcare systems, and resource issues account for heterogeneity. Female patients in the present work were also analysed individually to evaluate the impact of the hospital's healthcare infrastructure on EVAR.

Assessment of Heterogeneity

The heterogeneity of the findings was assessed by calculating the I² statistic, which compares the proportion of variation triggered by heterogeneity and by chance.

3.6.2 Publication Bias

It is the tendency to syndicate studies that generate only positive or significant results, thus distorting the results of meta-analysis. As for evaluating publication bias, the present meta-analysis applied funnel plots and Egger's test.

• Funnel Plots: Tests for asymmetry indicated by funnel plots of 30-day mortality and reintervention rates were significant. Furthermore, there was a considerably weak representation of the small caliber studies with non-significant findings, suggesting that there may be some bias in favor of publishing the papers on EVAR.
• Egger's Test: Based on Egger's test, a standard statistical tool to identify publication bias visually, p < 0.05 was obtained for both long-term mortality and reintervention rates, which means that publication bias existed in the present study.

4. Discussion

4.1 Summary of Main Findings

This meta-analysis compared endovascular aneurysm repair (EVAR) and open surgical repair (OR) for abdominal aortic aneurysms (AAA) in terms of mortality and morbidity early and late and in different settings. These results facilitate understanding of the advantages and disadvantages of each approach, as well as informing the decision-making process based on the specific patient's management of AAA (11).

EVAR also was associated with fewer deaths in the first 30 postoperative days (1.2% for EVAR and 4.8% for OR). This advantage arises from EVAR being less invasive than open surgical repair in terms of physiological insult and surgical time lost to surgical bleeding. In addition, patients who are at high risk for any surgical procedure, such as patients with increased age and those with some co-morbidities, are recommended to choose this procedure since they are more prone to develop side effects of open surgeries. As a result of the need for a time-conscious intervention in emergent cases, mortality rates in the ruptured AAA patients revealed EVAR to be relatively better, at 8.5% compared to OR's 20%. Annual mortality in the early phase was, however, higher in patients undergoing OR compared to EVAR, with a pooled estimate of 9.4% for EVAR and 12.2% for OR, while long-term mortality was similar with pooled forecasts of 18.2% for EVAR and 17.6% for OR followed up to 3 to 10 years. These findings indicate that although EVAR has symbolised several perioperative advantages, long-term outcomes concerning durability are somewhat affected by various complications related to the device, such as endoleaks, graft migration, and aneurysm sac growth. However, what is suggested to translate into lower long-term complication rates in OR is compensated for by significantly higher perioperative mortality related to the open surgery approach (12).

There was further perioperative morbidity that was significantly different for the two techniques. EVAR also had a lower perioperative complication rate: myocardial infarction (EVAR 1.3%, OR 3.5%) and acute renal Failure (EVAR 2.1%, OR 5.8%). The decreased complication rates in patients assigned to EVAR indicate the less invasive character of the procedure, less overall medication usage, and often the use of local or regional anesthesia, which has less impact on the overall systemic stress. OR was associated with a higher incidence of pulmonary complications, infections, and days on mechanical ventilation than open surgery (13), especially for older or comorbid patients because of the more extensive dissection required with this approach.

Recipient operative morbidity considering reintervention rates accepted OR due to its longevity. Patients treated by EVAR presented significantly higher overall reintervention rates, which vary between 15% and 20% compared with 5% of OR patients. These reinterventions were mainly attributed to endoleaks, graft migration, and secondary sac expansion, for which continued monitoring and imaging follow-up were necessary.

However, reinterventions following EVAR were predominantly less invasive, tentatively secondary endovascular interventions, while reinterventions following OR, though less frequent, mainly were secondary open surgeries (14). EVAR patients also had a significantly shorter hospitalisation: 2–4 days against 7–10 days for OR patients. This follows the EVAR, which is minimally invasive with benefits of early mobilisation, lower hospital resource consumption, and better early postoperative QoL. Overall QoL, as determined immediately after the operation, was better for the EVAR group, and even though patients in both groups reported similar pain and morbidity levels at six to twelve months, all the SVR indices and satisfaction scores were higher in the same group. However, regarding the QoL, no significant difference has been recorded between the two groups because the functional and mental health of the OR patients increases similarly with the recovery from the initial surgical stress (15).

They buttress the argument that the approach to managing AAA should be patient-specific. In elderly patients, especially those classified as high-risk, this procedure is preferred due to the perioperative advantage and low immediate risks accompanying EVAR compared to surgical repair (16). On the other hand, OR is preferred in relatively young and healthy patients, as well as those with large and/or complicated aneurysms, for which long-term patency is critical. Higher reintervention rates of EVAR have been demonstrated, continual postoperative surveillance is necessary, and developments in device technologies are needed to increase durability. On the other hand, in OR presentations, recent studies depict higher perioperative danger, and therefore, additional methods regarding pre-operative assessment of danger and risk reduction are required. These findings can be considered meta-synthesis in considering mortality and morbidity outcomes based on the incorporation data from different populations and clinical settings (17).

4.2 Interpretation in Context of Existing Literature

The present work confirms and enriches the currently available systematic reviews and clinical trials comparing EVAR and OR for patients with AAA. These findings supplement a broader range of data from more heterogeneous studies and patients, reflecting overall mortality and morbidity while reconciling with antecedent studies' conclusions.

The previous systematic meta-analysis and earlier well-established pivotal studies, the EVAR-1 and DREAM trials, have also established that EVAR has lower perioperative Mortality than OR (18). The EVAR-1 trial revealed the benefit of EVAR on 30-day mortality, which is 1.7% compared to 4.7% in OR; the result of the present meta-analysis is 1.2% in favor of EVAR and 4.8% for OR. This was well illustrated in this study by the consistent outcome in-hospital mortality, surgical morbidity, and patients' survival, thus strengthening the notion that EVAR is a less invasive option for elective AAA repair in such patients. Likewise, while using the DREAM trial earlier, we found a considerable reduction of perioperative complications associated with EVAR, which is also substantiated in this meta-analysis where myocardial infarction, renal failure, and pulmonary complications found to be significantly low in the EVAR group compared to the OR group. These findings also agree with the systematic reviews of Paravastu et al. and Becquemin et al. regarding the initial advantages of EVAR in reducing perioperative risks (19).

Long-term results, on the other hand, show a more favorable picture of EVAR and OR if compared. Though this meta-analysis indicated similar mid-term mortality (18.2% for EVAR, 17.6% for OR), as with earlier meta-analyses and RCTs, the latter pointed to the sustainability gain of OR. The EVAR-1 trial showed outcomes for aneurysm-related mortality and secondary interventions with prolonged follow-up greater than in the present analysis, which showed reintervention rates of EVAR of 15–20% as against ~5% for OR. This difference is due to device-associated issues, including endoleaks, graft migration, and enlargement of the sac, which may require further endoleak evaluation and follow-up interventions. On the other hand, OR has a long-term advantage over other repair techniques because it excludes sac aneurysms entirely, minimising recurrence and all associated complications (20). These outcomes are consistent with the findings of systematic reviews, including those formulated by Antoniou et al., who noted that EVAR had perioperative advantages over OR, which offered durability.

In emergent settings, such as ruptured AAA, the results of this meta-analysis support the growing literature that EVAR is preferred (21). The IMPROVE trial proved that a lower perioperative mortality rate was associated with EVAR than OR in patients with ruptured AAA; the authors recorded 8.5% for EVAR instead of 20% for OR. The technique of EVAR is less invasive and can be utilised more quickly in emergent cases than open surgical repair. However, issues regarding longer-term stability have been raised, as seen in previous reviews and trials; such patients' follow-ups must be done cautiously (22).

Quality of life (QoL) outcome provides additional., Understanding the findings in the context of current knowledge. This meta-analysis also found a significant early enhancement of QoL after EVAR similar to what was seen in the DREAM trial and reviews done by Patel and his team, where they noted that patients who underwent EVAR had less pain, quicker at regaining their everyday activities, faster than those who underwent open repair. In the long run, there is a relative overlap and even direction of the results of the QoL since OR patients compare favorably with patients after EVAR initially. However, the recovery is after the surgical stress. These observations support the view that short and long-term priorities in the care of patients are significant when making a plan (23).

However, some deviations should be discussed in light of the existing literature with which these hypotheses are consistent. For example, several previous systematic meta-analysis studies that have been conducted pointed to less heterogeneity in concerns to long-term mortality data (24). Incorporating data from observational studies with RCTs in this meta-analysis presented higher variability in long-term results; patient factors, aneurysmal character, and geographical conditions play a role (25). Further, although prior recommendations have limited their evaluation to particular subgroups, this approach diversifies them by including subgroup analyses of elective/emergent repairs, age, and aneurysm size that provide a reinforcement of the more personalised information obtained.

4.3 Strengths and Limitations

This meta-analysis compares endovascular aneurysm repair (EVAR) with open surgical repair (OR) for abdominal aortic aneurysms (AAA) and discusses strengths and limitations affecting the analysis of the results.

4.3.1 Strengths

The first advantage of this meta-analysis is that literature reviews covered numerous studies. This includes heterogeneous patient populations, various clinical contexts, and outcomes. It comprehensively assesses EVAR and OR performance based on up to 56 RCTs and over 66 observational studies. The addition of subgroup and sensitivity analysis adds more depth to the results, offering conclusions targeted to select demography, including a comparison between elective and emergent repair, elderly patients, and patients with complicated aneurysm morphology (26).

The strong statistical analysis method which has been applied also enhances the credibility of the outcomes. This approach was used to obtain pooled estimates of the intervention effect that incorporated the observed heterogeneity across studies where applicable by applying both random effects and fixed effect models (27). For this purpose, two refined risk of bias assessment instruments, the Cochrane Risk of Bias Tool and ROBINS-I, were used to quantify the quality of studies and reduce the impact of bias on the outcomes. Also, applying the publication bias evaluated by the funnel plot and Egger's test makes the authors more convincing.

Another source of strength is that some outcome measures across different categories have been evaluated. This way, the Mortality and morbidity results, including 30-day and long-term mortality, perioperative complications, ReDO rate, length of stay, and QoL, provide an apparent 'costs-benefit' consideration between EVAR and OR. These observations are essential for clinicians deciding on the approach to AAA treatment for a specific patient.

4.3.2 Limitations

Nevertheless, this meta-analysis has certain limitations that should be considered in connection with the results attained. Overall, it can also be noted that the evidence under consideration comprises one of the main methodological limitations obtained from the meta-analysis of various studies due to the heterogeneity of some of the included studies. Variations in the study type (RCTs Vs. observational studies), patients, aneurism, surgical intervention, and follow-up time also influenced variability in the pooled estimate (28). However, another limitation was that there was variation in the interventions, which can be due to varying patient characteristics; subgroup and sensitivity analyses helped reduce this but may still have affected generalisability.

Another issue is the quality of the studies included in the research agenda, as not all the relevant papers are of high quality. However, despite the attempt to consider only the best quality evidence, observational studies are inherently at higher risk of bias than RCTs. In addition, the wide variation in QoL instruments used, and the relatively low number of studies reporting on perioperative complications made it difficult to make definitive conclusions in some areas (29).

Another limitation of the current study is the lack of patient information needed to calculate IQR or a variety of co-morbidities. The lack of IOT, including mortality, detailed co-morbidities, frailty indices, or specific anatomic factors, limits the analysis to general data, which are essential for clinical decisions but may hide finer points. For instance, it was impossible to closely analyse the effects of specific devices, notably those used in EVAR or changes in techniques used in OR.

Lastly, publication bias is always a concern, even though The Cochrane search techniques were used and unpublished data were to be included wherever possible (30). These observations pointed towards possible asymmetry in the funnel plots and significant results of Egger's test. This may indicate that the studies that did not yield substantial results for the given comparisons, especially the long-term follow-up comparisons, may be underreported. This bias could lead to an overestimation of the benefits of the EVAR in some of the results.

4.4 Clinical Implications

The conclusions of this meta-analysis provide notable clinical implications for healthcare practitioners involving decision-making in managing abdominal aortic aneurysms (AAA) (31). This comparison of mortality and morbidity outcomes between endovascular aneurysm repair (EVAR) and open surgical repair (OR) helps clinicians arrive at a more informed treatment decision to match patient characteristics and clinical scenarios.

Therefore, the main message for clinicians is that EVAR has been shown to confer benefits in perioperative morbidities. EVAR thus comes out as having a better 30-day mortality rate and fewer perioperative complications compared to OR with the elderly and other high-risk patient populations considered. A benefit of EVAR over open surgery is that the ramp load factor decreased, there was less postoperative physiological disturbance and rapid mobilisation, hospital stay was reduced, and QoL was early ameliorated. These advantages make EVAR more appropriate for elective AAA repair interventions, thus for patients who may not withstand the invasiveness of OR. Furthermore, EVAR is a valuable choice in eventual situations such as ruptured AAA, where mortality and time to intervention count (18).

Nonetheless, long-term reintervention rates are higher in patients undergoing EVAR than those for surgical repair, and thus, patient selection is crucial, as is ensuring extensive follow-up. Selected patients with EVAR should undergo serial postoperative imaging to check for endoleaks, graft migration, or sac enlargement. To this end, the long-term outcomes for EVAR have been influenced by healthcare infrastructure and patient compliance.

For such patients, there are no contraindications to operation, and OR is still more potent and safer due to the higher rates of reintervention in comparison with it (32). OR ensures total aneurysm repair, decreasing the chances of aneurysm regrowth and additional surgeries. As discussed above, this durability can benefit large aneurysms >65mm or any aneurysm with anatomical features that may jeopardise the EVAR program. As mentioned above, risks during the early postoperative period are frequently linked to OR, but the long-term advantages may outcompensate early risks in patients able to handle the initial surgical load.

Patient selection should also concern anatomicals. EVAR is applicable where there is a better anatomy of the aneurysm, such as an acceptable neck length and minimal angulation to minimise technical complications. On the other hand, complex structures may mandate precise and long-wearing OR even at the expense of improved perioperative Mortality (33).

Guidelines regarding managing an AAA were also made to reflect the need to develop specific treatment plans depending on the patient profile, size and shape of the aneurysm, and clinical goals (34). EVAR is particularly advantageous in elderly patients, patients with numerous co-morbidities, and patients who have high surgical risk profiles from the standpoint of lower perioperative mortality, lower compounding rate of complications, and immediate rehabilitation period. It is also the option of Choice when dealing with emergent pathologies, with the characteristic of being minimally invasive and able to offer rapid intervention when needed, for instance, in the case of ruptured AAA. However, sustained durability of EVAR is contingent on follow-up and imaging scans to diagnose endoleaks graft migration or other complications, thus emphasising health care systems and patient compliance (35).

However, OR seems better applied to younger patients with longer life expectancies, who will benefit most from the reduced durability of the prosthesis and lower rate of reinterventions. OR is also advised for patients with large or anatomically complex aneurysms in which EVAR might be less practical or technically feasible. Even though OR is associated with increased perioperative risk, judicious pre-operative preparation can reduce adverse effects of this kind (36). In conclusion, treatment with EVAR and OR should be decided together, considering scientific knowledge, the patient's wishes, and the surgeon's recommendations, to achieve the highest results.

4.5 Future Research Directions

It is apparent from the studies reported to date that more research is needed to evaluate the long-term results of the two primary therapeutic approaches to AAA: EVAR and OR. Despite this meta-analysis's informative findings, there remains a strong demand for long-term follow-up investigations. Outcome evaluation, sustainable effectiveness of EVAR, endoleak progression, graft migration, and the life probabilities and risks on survivors of the EVAR and OR difference. Longitudinal follow-up assessment should also focus on the effect of reintervention rates in patients and HDC, health recession, and sustenance in the long run.

However, future studies should focus on patient-oriented measures of success such as QoL, functional outcome, and patient satisfaction. These areas are especially relevant for informing decision-making on which treatment options are to be pursued and the design of care that will fit a patient's needs and preferences. Because QoL and functional outcomes are essential to patients, these measures should be included as endpoints and clinical outcomes. They should use standardised methods to compare current clinical trials and future observational studies easily.

Another important research topic is the assessment of costs. However, EVAR presents certain perioperative benefits, and despite the lower initial cost, more excellent reintervention rates and life-long follow-up may nullify the benefits of this approach. Further, cost comparison analysis should consider expenses incurred during these processes, such as differential healthcare systems, patient adherence costs, and technological differences in differing systems.

To sum up, adequately powered follow-up studies, emphasis on patient-oriented results, and comprehensive CE analyses are needed to improve clinical algorithms and AAA intervention approaches. Future studies should also evaluate new technologies incorporated into the EVAR devices and methods to increase their durability and/or decrease the occurrence of complications to maintain the long-term effectiveness of EVAR in the population of patients with aneurysmal diseases.

5. Conclusion

Endovascular aneurysm repair (EVAR) and open surgical repair (OR) remain two crucial options for the management of abdominal aortic aneurysms (AAA), and this meta-analysis provides a review of the two techniques. Precisely recognising the concerns arising from this work across various populations and clinic types, this study is significant in showcasing how the overall management and executing process is generalisable and acknowledging each identified approach's uniqueness in strengths and weaknesses.

EVAR shows various perioperative benefits; the 30-day surgical mortality has been reduced, and the complications have been fewer than those in the OR. These benefits are better observed in those patients who are at a higher risk of developing postoperative complications, such as elderly patients, as well as those with comorbid diseases and in emergent circumstances, like ruptured AAA. EVAR means less invasiveness and entails shorter hospital stays, shorter time to full recovery, and better early quality of life (QoL). However, long-term results of EVAR are affected by devices-related complications such as endoleak and graft migration and, therefore, higher re-intervention rates (15-20% of EVAR individuals compared with about 5% of OR individuals). These observations emphasise the need for the continued monitoring of the EVAR results and the development of new technicalities that can improve the longevity of the intervention.

However, OR is more advantageous because it provides better durability with fewer reinterventions. For patients with a longer lifespan, this is good enough to recommend OR for young, healthy people and large or complex aneurysm patients. Perioperatively, OR is associated with higher risk, morbidity, and increased recovery time; however, OR is associated with exclusion of the aneurysm and higher durability as a treatment option. Disparities of clinical QoL outcomes between fully endovascular abdominal aortic aneurysm repair (EVAR) and open repair (OR) are primarily due to the initial post-surgical stress and eventually even out as OR patients are less stressed.

This meta-analysis is also not without limitations, including the high level of study heterogeneity, lack of patient-level data, and the possibility of publication bias (37). These point to the need for more studies regarding long-term outcomes, patient-reported outcomes, and cost-effectiveness. Innovations in EVAR devices are paramount in enhancing their results and compulsorily dealing with their drawbacks.

Altogether, EVAR and OR have their benefits and should be used in a unique cohort of patients. Management strategies should incorporate patient factors, aneurysmal characteristics, and clinical relevance to afford the highest chances of favorably affecting the outcome of patients and further improving the level of AAA treatment.

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