Early and Mid-Term Results of Endovascular Aortic Repair Using a Crossed-Limb Technique for Patients with Severely Splayed Iliac Angulation

Impact of Cross-Limb Stent-Graft Configuration on Hemodynamics in Abdominal Aortic Aneurysm Interventional Therapy

PURPOSE

The cross-limb (CL) technique is a commonly used endovascular treatment for addressing unfavorable anatomical features in patients with abdominal aortic aneurysm (AAA). The configuration of CL stent-graft plays a critical role in determining the postoperative hemodynamic properties and physiological behaviors, which ultimately impact the efficacy and safety of endovascular AAA treatment. This study aims to investigate the relationship between hemodynamics and CL stent-graft configuration from a hemodynamic perspective.

METHODS

Five distinct geometric models of cross-limb (CL) stent-graft configurations were constructed by optimizing the real clinical computed tomography angiography (CTA) data. These models varied in main body lengths and cross angles and were used to perform numerical simulations to analyze various hemodynamic parameters. Flow pattern, distribution of wall shear stress (WSS)-related parameters, localized normalized helicity (LNH), pressure drop, and the displacement force of all models were examined in this paper.

RESULTS

In patient-specific cases, helical flow and WSS increase with the main body. However, it also generated secondary flow in localized areas, leading to increased oscillation in the WSS direction. Notably, increasing the stent graft's main body length or decreasing the cross angle reduced the displacement force exerted on the stent-graft. Reducing the cross angle did not significantly alter the hemodynamic characteristics.

CONCLUSION

In the clinical practice of CL deployment, it is crucial to carefully consider the stent-graft configuration and the patient specific to achieve optimal postoperative outcomes. This study provides valuable insights for guiding stent selection and treatment planning in patients with abdominal aortic aneurysm undergoing CL techniques, from a hemodynamic perspective.

Outcome Analysis of Speed Gate Cannulation during Standard Infrarenal Endovascular Aneurysm Repair

BACKGROUND

Endovascular aortic repair (EVAR) is generally performed with bi/trimodular stent-grafts requiring retrograde contralateral gate cannulation (CGC). In the case of tricky CGC, an increased EVAR procedural time and radiation exposure have been reported. Herein, we compare the outcomes of conventional CGC and CGC using the speed gate cannulation (SGC) technique in standard EVAR for a propensity-matched cohort.

METHODS

A total of 371 patients were retrospectively analyzed. Inclusion criteria were fulfilled in 172 patients who underwent propensity score matching. Primary outcomes included operative time, CGC time, mean contrast medium, fluoroscopy time, and CGC fluoroscopy time.

RESULTS

After matching, 78 patients were included in each group (SGC vs. standard). Primary outcomes registered a significant reduction in CGC time (4 [1-6] vs. 8 [6-14] min; p = 0.001) and fluoroscopy time (12 [9-16] vs. 17 [12-25] min).

CONCLUSIONS

In this preliminary experiment, the use of SGC was feasible with no significant registered postoperative complications. A significant reduction in contrast medium usage, radiation exposure, and CGC time was observed with the use of SGC. SGC is a simple adjunctive technique, and its use should be considered in standard EVAR, especially in emergency scenarios, where time is of the essence.

A Comparative Study on the Hemodynamic Performance Within Cross and Non-cross Stent-Grafts for Abdominal Aortic Aneurysms With an Angulated Neck

Objectives: Cross-limb stent grafts for endovascular aneurysm repair (EVAR) are often employed for abdominal aortic aneurysms (AAAs) with significant aortic neck angulation. Neck angulation may be coronal or sagittal; however, previous hemodynamic studies of cross-limb EVAR stent grafts (SGs) primarily utilized simplified planar neck geometries. This study examined the differences in flow patterns and hemodynamic parameters between crossed and non-crossed limb SGs at different spatial neck angulations.

Methods: Ideal models consisting of 13 cross and 13 non-cross limbs were established, with coronal and sagittal angles ranging from 0 to 90°. Computational fluid dynamics (CFD) was used to capture the hemodynamic information, and the differences were compared.

Results: With regards to the pressure drop index, the maximum difference caused by the configuration and angular direction was 4.6 and 8.0%, respectively, but the difference resulting from the change in aneurysm neck angle can reach 27.1%. With regards to the SAR-TAWSS index, the maximum difference caused by the configuration and angular direction was 7.8 and 9.8%, respectively, but the difference resulting from the change in aneurysm neck angle can reach 26.7%. In addition, when the aneurysm neck angle is lower than 45°, the configuration and angular direction significantly influence the OSI and helical flow intensity index. However, when the aneurysm neck angle is greater than 45°, the hemodynamic differences of each model at the same aneurysm neck angle are reduced.

Conclusion: The main factor affecting the hemodynamic index was the angle of the aneurysm neck, while the configuration and angular direction had little effect on the hemodynamics. Furthermore, when the aneurysm neck was greatly angulated, the cross-limb technique did not increase the risk of thrombosis.

Meta-Analysis of the Crossed Versus Standard Limb Configuration in Endovascular Aneurysm Repair

OBJECTIVE

To investigate whether the crossed-limb technique confers better or worse clinical outcomes compared to the standard straight limb configuration in standard endovascular aneurysm repair (EVAR).

METHODS

We conducted a systematic review to identify studies comparing outcomes of EVAR with the crossed versus standard limb configuration. MEDLINE, EMBASE, CINAHL, and CENTRAL were searched in March 2021 using the Healthcare Databases Advanced Search interface developed by the National Institute for Heath and Care Excellence. The risk of bias was assessed with the Newcastle-Ottawa scale (NOS) and the Risk Of Bias In Non-randomized Studies - of Interventions (ROBINS-I) tool. Summary estimates were calculated using the odds ratio (OR), risk difference (RD), or mean difference (MD) and 95% confidence interval (CI), applying the Mantel-Haenszel or inverse variance statistical method. Random-effects models were employed.

RESULTS

Four observational studies qualified for inclusion, reporting a total of 1132 patients. All presented contemporary experiences. Baseline clinical characteristics were largely similar between patients with and without the crossed-limb configuration, but the anatomy tended to be less favourable in patients treated with the crossed-limb technique. No statistically significant difference was found in the primary outcomes: limb occlusion (OR 1.44, 95% CI 0.65 - 3.19), type Ib endoleak (RD 0.01, 95% CI -0.03 - 0.04), type III endoleak (RD 0.01, 95% CI -0.01 - 0.03); or secondary outcomes: perioperative mortality (RD 0.00, 95% CI -0.03 - 0.03), type Ia endoleak (RD 0.00, 95% CI -0.03 - 0.02), type II endoleak (OR 1.38, 95% CI 0.51 - 3.74), procedure duration (MD 18.07 min, 95% CI -1.14-37.29). Inconsistency across studies was low for all outcomes. The studies were judged to be of high quality on the NOS. The main bias identified using the ROBINS-I tool was due to confounding.

CONCLUSIONS

The crossed-limb technique was not found to confer inferior clinical outcomes in the medium term compared to the standard limb configuration in patients who undergo standard EVAR.

Comparative evaluation of ballet-type and conventional stent graft configurations for endovascular aneurysm repair: A CFD analysis

PURPOSE:

Cross limb stent graft (SG) configuration technique for endovascular aneurysm repair (EVAR) is employed for splayed aortic bifurcations to avoid device kinking and smoothen cannulation. The present study investigates three types of stent graft (SG) configurations for endovascular aneurysm repair (EVAR) in abdominal aortic aneurysm. A computational fluid dynamic analysis was performed on the pulsatile non-Newtonian flow characteristics in three ideally modeled geometries of abdominal aortic (AA) SG configurations.

METHODS:

The three planar and crosslimb SG configurations were ideally modeled, namely, top-down nonballet-type, top-down ballet-type, and bottom-up nonballet-type configurations. In top-down SG configuration, most of the device is deployed in the main body in the vicinity of renal artery and the limbs are extended to the iliac artery. While in the bottom-up configuration, some of the SG device is deployed in the main body, the limbs are deployed in aortic bifurcation, and the extra stent graft of the main body is extended to the proximal aorta until the below of the renal artery. The effects of non-Newtonian pulsatile flow on the wall stresses and flow patterns of the three models were investigated and compared. Moreover, the average wall shear stress (AWSS), oscillatory shear stress index (OSI), absolute helicity, pressure distribution, graft displacement and flow visualization plots were analyzed.

RESULTS:

The top-down ballet-type showed less branch blockage effect than the top-down nonballet-type models. Furthermore, the top-down ballet-type configuration showed an increased tendency to sustain high WSS and higher helicity characteristics than that of the bottom-up and top-down non-ballet type configurations. However, displacement forces of the top-down ballet-type configuration were 40% and 9.6% higher than those of the bottom-up and top-down nonballet-type configurations, respectively.

CONCLUSIONS:

Some complications such as graft tearing, thrombus formation, limb disconnection during long term follow up periods might be relevant to hemodynamic characteristics according to the configurations of EVAR. Hence, the reported data required to be validated with the clinical results.

Editor's Choice - Mid Term Outcomes of Crossed Limb vs. Standard Limb Configuration in Endovascular Abdominal Aortic Aneurysm Repair: A Propensity Score Analysis

OBJECTIVE

The aim was to compare mid term outcomes between crossed limb (CL) and standard limb (SL) configuration in patients who underwent endovascular aortic aneurysm repair (EVAR).

METHODS

This was a comparative cohort study. Eligible patients who underwent EVAR between September 2011 and March 2019 in a tertiary academic centre were included. Inverse probability of treatment weighting (IPTW) was used to balance the demographic, anatomical and operative baseline characteristics between the two groups. The primary outcome was adverse limb events including type IB endoleak (T1BEL), type III endoleak, and limb occlusion. Cox proportional hazards regression and marginal structural model were performed to compare time to event outcomes.

RESULTS

The study included 729 patients (194 CL and 535 SL) with a median follow up of 34 months (interquartile range 16 - 62 months). The weighted analyses revealed no significant difference between CL and SL EVAR in terms of adverse limb events, type IA endoleak (T1AEL), type II endoleak (T2EL), re-intervention, and overall survival. In the subgroup analysis of large aneurysm sac, the CL configuration was associated with a significantly decreased risk of T1BEL (hazard ratio [HR] 0.31, 95% confidence interval [CI] 0.12 - 0.78, p = .014). Similar results were also observed in the subgroup of tortuous iliac arteries (HR 0.30, 95% CI 0.11 - 0.81, p = .017). After stratification by severe neck angulation, no significant difference was found between CL and SL EVAR for T1AEL, but the CL configuration was associated with a significantly increased risk of re-intervention (HR 2.69, 95% CI 1.31 - 5.51, p = .007). In addition, a trend towards a higher risk of adverse limb events in the CL group with severely angulated proximal neck was observed.

CONCLUSION

CL configuration in EVAR is safe and may be associated with a lower risk of T1BEL in patients with a large aneurysm sac or tortuous iliac arteries. However, it should be applied cautiously to aneurysms with a severely angulated neck due to the potentially higher risk of re-intervention.

Improved technique for sheath supported contralateral limb gate cannulation in endovascular abdominal aortic aneurysm repair

Background: To present a technique of sheath supported contralateral limb gate (CLG) cannulation of modular bifurcated stent-graft in endovascular abdominal aortic repair. Materials and methods: After totally percutaneous bilateral femoral access, the 9F introducer sheath is exchanged to a 30 cm 12 fr introducer sheath over a stiff wire contralateral to the intended main stent-graft insertion side and advanced into the aorta below the lowest renal artery. Parallel to the stiff wire within the sheath an additional standard J-tip guidewire with a 5 fr Pigtail angiographic catheter is advanced to the level of the renal arteries. After main body deployment, the 12 fr introducer sheath and J-tip wire with pigtail catheter are retracted until the CLG opening level, maintaining the stiff "buddy" wire in position to support the 12 fr sheath, maintaining its distal opening close to the contralateral gate opening to achieve easy cannulation. Results: Retrospective analysis of video archive from July 2016 to February 2018 evidenced 55 recorded EVAR cases. All CLG cannulations were obtained with Standard J-tip or Terumo Glidewire wires and with Pig-Tail or Berenstein catheters. Technical success was 100 %. Mean fluoroscopy time to accomplish CLG cannulation was 37.6 33 (range 1-105) seconds. The aortic carrefour angulation on coronal axis strongly correlates with cannulation time p = <.001, with longer cannulation time for higher carrefour angulations on coronal axis (Pearson correlation coefficient 0.47). Conclusions: The use of 12 fr sheath with parallel wire introduction technique, appears to be a safe and reliable tool to facilitate CLG cannulation during EVAR procedures.