Perioperative factors associated with aneurysm sac size changes after endovascular aneurysm repair

Prediction of Aneurysm Sac Shrinkage After Endovascular Aortic Repair Using Machine Learning-Based Decision Tree Analysis

INTRODUCTION

A simple risk stratification model to predict aneurysm sac shrinkagein patients undergoing endovascular aortic repair (EVAR) for abdominal aortic aneurysms (AAA) was developed using machine learning-based decision tree analysis.

METHODS

One hundred nineteen patients with AAA who underwent elective EVAR at Tokyo Medical University Hospital between November 2013 and July 2019 were included in the study. Predictors of aneurysm sac shrinkage identified in univariable analysis (P < 0.05) were entered into the decision tree analysis.

RESULTS

Univariable analysis revealed significant differences between patients with and without aneurysm sac shrinkage in the variables of age (<75 y or ≥75 y), current smoking, operative type II endoleak, and preoperative pulse wave velocity (PWV) (<1800 cm/s or ≥1800 cm/s). The decision tree showed that preoperative PWV was the most relevant predictor, followed by operative type II endoleak and current smoking, and identified 6 terminal nodes with likelihoods of aneurysm sac shrinkage ranging from 5.6% to 63.6%.

CONCLUSIONS

We established a decision tree model with 3 variables (preoperative PWV, operative type II endoleak, and current smoking) to predict aneurysm sac shrinkage in patients undergoing EVAR for AAA. This classification model may help identify patients with a high or low likelihood of aneurysm sac shrinkage.

An Updated Review on Arterial Stiffness Measurement Techniques and Arterial Stiffness Alterations After Aortic Aneurysm Repair

BACKGROUND

Studies over the last years have revealed the possible impact of endovascular repair of abdominal or thoracic aortic aneurysms on the arterial stiffness and secondary on the cardiac function and the central hemodynamics.

METHODS

A literature search was conducted to collect data on current methods of arterial stiffness assessment and the induced changes in arterial stiffness after endovascular or open surgical repair of abdominal or thoracic aortic aneurysms.

RESULTS

Seventeen studies were analyzed. In most of these studies, arterial stiffness, either assessed by pulse wave velocity or augmentation index, was found to be increased after aortic aneurysm repair. Factors that increase arterial stiffness seem to be endovascular repair of the aneurysm and the proximity of the stent graft to the heart. The clinical implications of increased arterial stiffness are left ventricular hypertrophy, coronary arteries malperfusion and potential end-organ damage.

CONCLUSIONS

Both endovascular and open aortic aneurysm repair can alter arterial stiffness, with endovascular repair having a greater effect. Future research is essential, particularly in exploring the impact of aortic aneurysm repair methods on vital organs and cardiac function. Extended follow-up studies are proposed to gain a better understanding of the long-term cardiovascular consequences of both endovascular and open surgical repair outcomes.

Brachial-Ankle Pulse Wave Velocity Reflects Regional Arterial Stiffness and Distensibility in Patients with Abdominal Aortic Aneurysm

Objectives: We investigated the association between brachial-ankle pulse wave velocity (PWV) and arterial stiffness and distensibility in the aneurysmal sac of abdominal aortic aneurysm (AAA). Methods: Data from 49 patients with AAA from June 2020 to November 2022 at Tokyo Medical University Hospital were retrospectively analyzed. Brachial-ankle PWV (cm/s) was obtained via an automated oscillometric method. Regional arterial stiffness and distensibility parameters, such as stiffness parameter (β), pressure-strain elasticity modulus (Ep, kPa), one-point PWV (PWV β, m/s), and arterial compliance (AC, mm2/kPa-1), were assessed using 2-dimensional automated tissue tracking (2DTT) ultrasonography. Patients were divided into two groups: high PWV (≥1800) and low PWV (<1800). Results: Patients with high PWV showed significantly higher β and PWV β (30.6 ± 10.1 vs. 25.2 ± 6.3, p = 0.047; 11.6 ± 2.3 vs. 10.5 ± 1.5, p = 0.048) and significantly lower AC in the aneurysmal sac (10.6 ± 5.3 vs. 14.7 ± 8.1, p = 0.045) than those with low PWV. AC was negatively correlated with PWV (r = -0.361, p = 0.011). Conclusions: Brachial-ankle PWV can reflect arterial stiffness and distensibility, as measured by 2DTT ultrasonography, in the aneurysmal sac of AAA, suggesting its potential as an elasticity index for assessing regional arterial stiffness and distensibility in AAA.

Arterial Stiffness and Aortic Aneurysmal Disease - A Narrative Review

It has been documented that large-artery stiffness is independently associated with increased cardiovascular risk and may potentially lead to heart and kidney failure and cerebrovascular disease. A systematic review of studies investigating changes in arterial stiffness in patients undergoing endovascular repair of aortic disease was conducted. In addition, a review of the available literature was performed, analyzing findings from studies using the cardio-ankle vascular index (CAVI) as a marker of arterial stiffness. Overall, 26 studies were included in the present analysis. Our research revealed a high heterogeneity of included studies regarding the techniques used to assess the aortic stiffness. Aortic stiffness was assessed by pulse wave velocity (PWV), elastic modulus (Ep), and augmentation index (AI). Currently a few studies exist investigating the role of CAVI in patients having an aortic aneurysm or undergoing endovascular aortic repair. The majority of studies showed that the treatment of an abdominal aortic aneurysm (AAA) either with open repair (OR) or endovascular aortic repair (EVAR) reduces aortic compliance significantly. Whether EVAR reconstruction might contribute a higher effect on arterial stiffness compared to OR needs further focused research. An increase of arterial stiffness was uniformly observed in studies investigating patients following thoracic endovascular aortic repair (TEVAR), and the effect was more pronounced in young patients. The effects of increased arterial stiffness after EVAR and TEVAR on the heart and the central hemodynamic, and an eventual effect on cardiac systolic function, need to be further investigated and evaluated in large studies and special groups of patients.

Change in Abdominal Aortic Aneurysm Sac Diameter After Endovascular Repair: A Single-Center Experience From Taiwan

PURPOSE

The purpose of this study was to investigate the change in the diameter of infrarenal abdominal aortic aneurysm (AAA) sacs after endovascular aortic repair (EVAR) in Taiwanese patients and to depict its association with clinical outcomes.

MATERIALS AND METHODS

This retrospective cohort study was conducted on patients who underwent EVAR for infrarenal AAA between January 2011 and December 2016. All preoperative and follow-up computed tomography (CT) images were reviewed. Postoperative CT angiography was arranged after 1 month and annually thereafter. The maximal diameter on the axial plane and the maximal diameter perpendicular to the centerline on the coronal and sagittal planes were measured. The study examined post-EVAR sac diameter change over time and compared the differences in adverse events (AEs) among groups.

RESULTS

The survey included a total of 191 patients with a median follow-up duration of 2.5 (interquartile range: 1.1-2.9) years. Overall survival rates at 1, 2, and 5 years were 92%, 81%, and 76%, respectively. According to their last CT scans, the patients were categorized into 3 groups as follows: shrinkage, stationary, and enlargement, which comprised 58 (30.4%), 118 (61.8%), and 15 (7.9%) patients, respectively. Pre-EVAR characteristics and sac diameters were similar among the groups. Sac shrinkage was exclusively observed in the first 2 years, whereas sac enlargement developed at all follow-up periods. Patients with sac enlargement had higher incidence rates of endoleaks, complications, and reintervention than the other groups.

CONCLUSION

Based on our observations, post-EVAR sac shrinkage only occurs in the first 2 years; however, post-EVAR sacs may enlarge at any point and even after 5 years. In our study, patients with sac enlargement had higher rates of adverse events and reintervention.

A stable aneurysm sac after endovascular aneurysm repair as a predictor for mortality, an in-depth analysis

OBJECTIVES

The aim of this study was to compare the long-term survival in patients with a stable aneurysmal sac and those with aneurysmal sac regression after endovascular aneurysm repair (EVAR) and to identify independent risk factors for aneurysmal sac regression and mortality after EVAR.

METHODS

We reviewed all patients who underwent EVAR between 2005 and 2018 with a computed tomography angiography available at 1-year follow-up. Aneurysm sac regression was defined as a diameter decrease of more than 10%. We used a multivariable regression to identify independent risk factors for sac regression. Kaplan-Meier analysis and Cox regression were done to test differences in 5-year mortality between a stable sac and sac regression.

RESULTS

The inclusion criteria were met by 325 patients, 185 in the sac regression group and 140 in the stable sac group. Multivariable logistic regression analysis showed that treatment for a ruptured aneurysm was an independent risk factor for aneurysmal sac regression (hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.07-0.96). Age (HR, 1.05; 95% CI, 1.01-1.09), ischemic heart disease (HR, 1.94; 95% CI, 1.13-3.31), neck thrombus (HR, 2.72; 95% CI, 1.07-6.95), and a type II endoleak (HR, 19.21; 95% CI, 7.32-50.40) were independent risk factors for a stable aneurysm sac diameter. Multivariable Cox regression showed a significantly increased risk of mortality for patients with a stable aneurysm sac after EVAR (odds ratio, 2.25; 95% CI, 1.36-3.72). There was no significant difference in cause of death between the two groups.

CONCLUSION

A stable aneurysm sac after EVAR is associated with increased mortality. Age, ischemic heart disease, neck thrombus, and a type II endoleak are independent risk factors for a stable sac. However, a well-founded explanation for this finding is still lacking. Future research should be focussed on aggressive treatment of type II endoleaks and inflammatory processes as potential pathophysiological mechanisms.

A systematic review on anatomical predictors of abdominal aortic aneurysm remodeling after endovascular repair

OBJECTIVE

Long-term outcomes after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs) are inferior to open surgical repair with regard to reinterventions and late mortality. AAA sac remodeling after EVAR has been associated with endoleaks, reinterventions, and mortality. Therefore, predictors of AAA sac remodeling could indirectly give insight into long-term EVAR outcomes. This review aims to provide an overview of the evidence on anatomical predictors of positive and negative AAA sac remodeling after EVAR.

METHODS

A systematic literature review and analysis were conducted according to the PRISMA and Cochrane guidelines. PubMed and Scopus databases were searched using terms of AAA sac growth, shrinkage, and remodeling. Eligible articles were identified and only papers that included currently used endografts were included.

RESULTS

Nineteen studies that reported on a total of 27 anatomical parameters of the aortoiliac anatomy were included. Only 4 parameters were investigated by >5 studies, 7 parameters were investigated by 3-5 studies, 6 parameters were investigated by 2 studies, and 10 parameters were investigated by 1 study. For the presence of neck thrombus, 3 out of 4 studies reported similar results indicating that it may predict less AAA sac shrinkage. AAA thrombus, total AAA volume, flow-lumen volume, and the number of hostile neck parameters were only investigated by 2-3 studies, but they seem promising in predicting sac remodeling. For hostile neck anatomy, neck length, infrarenal neck angulation, and patency of the inferior mesenteric artery, no significant association with any category of AAA sac remodeling was found.

CONCLUSIONS

This review presents neck thrombus, AAA thrombus, number of hostile neck parameters, total AAA volume, and AAA flow-lumen volume as important anatomical features that are likely to play a role in AAA remodeling after endovascular repair that should be further explored using advanced imaging techniques. This review also showed that strong consistent evidence on anatomical predictors of AAA sac remodeling after EVAR is lacking. Therefore, further research with large patient groups on a broad range of predictors of AAA sac change after EVAR is needed to complement the current gap in the evidence.

Arterial pulse wave propagation across stenoses and aneurysms: assessment of one-dimensional simulations against three-dimensional simulations and in vitro measurements

One-dimensional (1-D) arterial blood flow modelling was tested in a series of idealized vascular geometries representing the abdominal aorta, common carotid and iliac arteries with different sizes of stenoses and/or aneurysms. Three-dimensional (3-D) modelling and in vitro measurements were used as ground truth to assess the accuracy of 1-D model pressure and flow waves. The 1-D and 3-D formulations shared identical boundary conditions and had equivalent vascular geometries and material properties. The parameters of an experimental set-up of the abdominal aorta for different aneurysm sizes were matched in corresponding 1-D models. Results show the ability of 1-D modelling to capture the main features of pressure and flow waves, pressure drop across the stenoses and energy dissipation across aneurysms observed in the 3-D and experimental models. Under physiological Reynolds numbers (Re), root mean square errors were smaller than 5.4% for pressure and 7.3% for the flow, for stenosis and aneurysm sizes of up to 85% and 400%, respectively. Relative errors increased with the increasing stenosis and aneurysm size, aneurysm length and Re, and decreasing stenosis length. All data generated in this study are freely available and provide a valuable resource for future research.

Changes in Neck Angle, Neck Length, Maximum Diameter, Maximum Area and Thrombus after Endovascular Aneurysm Repair

Purpose

The correlation of initial anatomy of the aneurysm, aneurysmal remodeling and endoleaks is controversial. We performed a retrospective study to measure aneurysmal remodeling with time, and to assess the structural changes in the aneurysm neck after endovascular aneurysm repair (EVAR).

Materials and Methods

From January 2013 to February 2018, 108 patients with abdominal aortic aneurysms (AAA) underwent EVAR. Follow-up computed tomography images were available for 90 patients. Anatomic variables, including the neck angle, neck length, maximal diameter, maximal area, and thrombus volume were measured. Temporal changes were measured preoperatively, immediate postoperatively (within 1 week after EVAR), and at 6 months, 1 year, and 2 years post-EVAR. Correlation between the variables according to the temporal changes and presence of type Ia endoleaks (T1aE) was analyzed.

Results

The mean follow-up period was 10.63±20.34 months. Significant decreases in neck angle and length occurred immediately postoperative (P<0.001 and 0.036). Maximum diameter decreased at 6 months post-EVAR (P=0.003), but no significant changes in the maximal area occurred over time (P=0.142). Thrombus volume in the aneurysm sac increased immediately post-EVAR (P=0.008). There was no significant relationship between T1aE and neck changes in the group and time comparison (P=0.815 and 0.970).

Conclusion

Changes in neck angle, length and thrombus volume occurred immediately after EVAR, whereas a change in the maximum diameter of the AAA was noted 6 months after EVAR. Preoperative anatomic variables related with T1aE were not found.

Effect of endoprostheses on pulse wave velocity and its long-term outcomes after thoracic endovascular aortic repair

BACKGROUND

The purpose of this study was to evaluate the changes in pulse wave velocity and left ventricular dimensions in patients undergoing stent-graft treatment for aortic arch aneurysm.

METHODS

From July 2008 to February 2019, 86 patients underwent thoracic endovascular aortic repair of an aortic arch aneurysm. Changes in pulse wave velocity (PWV), echocardiogram findings, and long-term outcomes were compared between endoskeleton type (n = 60) and exoskeleton type stent-graft (n = 26).

RESULTS

There was no significant difference in patient demographics except for diabetes which was more observed in endoskeleton type (p = 0.017). There was a significant increase in PWV in exoskeleton type after surgery, which further progressed at a median follow-up of 32 months (before: 2047 cm/s vs. after: 2259 cm/s vs. follow-up: 2486 cm/s, p = 0.010, p = 0.017). No significant difference was observed in endoskeleton type (before: 1980 cm/s vs. after: 2058 cm/s, vs. follow-up: 2042 cm/s, p = 0.25, p = 0.34). Echocardiogram performed at a median period of 46.3 months, revealed a significant increase in left ventricular diastolic volume (LVDV) (before: 107.4 ± 20.6 ml vs. follow-up: 127.7 ± 27.5 ml, p = 0.003) and decrease in e' (before: 5.5 ± 1.78 cm/s vs. follow-up: 4.7 ± 1.72 cm/s, p = 0.012) in exoskeleton type, while no significant change was observed in endoskeleton type (LVDV: before: 102.6 ± 32.3 ml vs. follow-up: 96.9 ± 35.4 ml, p = 0.74; e': before: 4.4 ± 1.21 cm/s vs. follow-up: 4.8 ± 1.40 cm/s, p = 0.68). At the median period of 61.3 months, there was no significant difference in long-term mortality (p = 0.89). However, the endoskeleton type was associated with a lower incidence of a cardiac event (p = 0.034) and cerebrovascular event (p = 0.029).

CONCLUSION

Types of endoprosthesis might affect differently on physiological changes and its accommodated risk factors after surgery.