Geometric Alteration of Renal Arteries After Fenestrated Grafting and the Impact on Renal Function

Experimental Study of Collateral Patency following Overlapped Multilayer Flow Modulators Deployment

Decades after its introduction, endovascular aneurysm repair remains a challenging procedure with risks of collateral patency failure. Here, we investigate the ability of a porous stent, the Multilayer Flow Modulator (MFM), to maintain renal perfusion after a single or overlapping case. Silicone models representing an ideal infrarenal AAA geometry were used to analyze and compare three cases (control, single MFM and two overlapped MFMs). Micro-computed tomography was used to image the deployed MFM devices geometry and evaluate pore size and density along with porosity in both two (planimetric) and three dimensions (gravimetric). Laser particle image velocimetry (PIV) experiments were performed to image velocity and vorticity fields at the aorta-renal bifurcation. Flow experiments revealed renal arteries perfusion preservation in both single and overlapped cases. Microstructure analysis revealed an uneven distribution of wires in the MFM devices leading to local change in planimetric porosity and pore size. Overlap of a second MFM device led to a significant decrease in those 2D metrics but did not affect the gravimetric porosity and the branch perfusion. This first microstructure evaluation of MFM device combined with flow experiments revealed the ability of the device to preserve collateral flow thanks to a highly porous microstructure.

Site of Origin of the Ophthalmic Artery Influences the Risk for Retinal Versus Cerebral Embolic Events

BACKGROUND

Embolic events leading to retinal ischemia or cerebral ischemia share common risk factors; however, it has been well documented that the rate of concurrent cerebral infarction is higher in patients with a history of transient ischemic attack (TIA) than in those with monocular vision loss (MVL) due to retinal ischemia. Despite the fact that emboli to the ophthalmic artery (OA) and middle cerebral artery share the internal carotid artery (ICA) as a common origin or transit for emboli, the asymmetry in their final destination has not been fully explained. We hypothesize that the anatomic location of the OA takeoff from the ICA may contribute to the differential flow of small emboli to the retinal circulation vs the cerebral circulation.

METHODS

We report a retrospective, comparative, case-control study on 28 patients with retinal ischemia and 26 patients with TIA or cerebral infarction caused by embolic events. All subjects underwent either computed tomography angiography or MRA. The location of the ipsilateral OA origin off the ICA was then graded in a blinded fashion and compared between cohorts. Vascular risk factors were collected for all patients, including age, sex, hypertension, hyperlipidemia, arrhythmia, diabetes, coronary artery disease, and smoking.

RESULTS

We find that in patients with retinal ischemia of embolic etiology, the ipsilateral OA takeoff from the ICA is more proximal than in patients with cerebral infarcts or TIA (P = 0.0002). We found no statistically significant differences in demographic, vascular, or systemic risk factors.

CONCLUSIONS

We find that the mean anatomical location of the OA takeoff from the ICA is significantly more proximal in patients with MVL due to retinal ischemia compared with patients with TIA or cerebral ischemia. This finding contributes significantly to our understanding of a long observed but poorly understood phenomenon that patients with MVL are less likely to have concurrent cerebral ischemia than are patients with TIA.

Morphologic Features of Symptomatic and Ruptured Abdominal Aortic Aneurysm in Asian Patients

BACKGROUND

To evaluate morphologic features of symptomatic and ruptured abdominal aortic aneurysms in Asian patients.

METHODS

Two hundred sixty four continuous candidates with an abdominal aortic aneurysm (AAA) were retrospectively identified from a tertiary hospital database between January 2017 and May 2019. The patients meeting inclusion criteria were divided into symptomatic or ruptured AAA (srAAA) and asymptomatic AAA (asAAA) groups. Their computed tomography angiographies were reconstructed using centerline technique and the geometric features of AAAs between the 2 groups were compared.

RESULTS

One hundred two patients fulfilled selection criteria (mean age 71 years, 80 men), comprising 35 srAAAs and 67 asAAAs. There was no essential association between gender, smoking or hypertension, and AAA-associated symptoms or rupture. The maximum diameter (5.8 ± 1.4 cm vs. 5.0 ± 0.9 cm; P = 0.001), length (8.8 ± 0.6 cm vs. 7.0 ± 0.3 cm; P = 0.002), and intraluminal thrombus (ILT) thickness (1.7 ± 0.2 cm vs. 1.3 ± 0.1 cm; P = 0.039) of AAAs were independent risk factors for AAA-associated symptoms or rupture (binary logistic regression, P < 0.05), but AAA length and ILT were strongly correlated with the AAA diameter (Pearson correlation coefficient value of 0.591 and 0.444) whereas other factors such as aneurysmal tortuosity, aneurysmal neck anatomy, or common iliac artery geometry were nonsignificant.

CONCLUSIONS

AAA diameter, length, and intraluminal thrombus thickness were identified as risk factors for AAA-associated symptoms in Asian patients. While the diameter is regarded as the most important predictor for symptoms and rupture, AAA length and ILT thickness should also be taken into consideration when contemplating intervention, particularly for borderline and smaller aneurysms.

Changes in Target Vessel Anatomy Following Fenestrated Endovascular Aneurysm Repair: Midterm Results

Purpose: To analyze the changes in target vessel (TV) anatomy after fenestrated endovascular aneurysm repair (fEVAR) during midterm follow-up. Materials and Methods: A retrospective single-center study analyzed 56 patients (mean age 71±7 years; 49 men) who underwent fEVAR using custom-made stent-grafts (22 Zenith and 34 Anaconda) between June 2010 and July 2016. Advanta V12 (V12; 74, 53%) and BeGraft (BeG; 66, 47%) stent-grafts were used to bridge to the 140 TVs. Measurements of the TV deviation at the aortic origin, the vessel shift distal to the bridging stent-graft (BSG), and the outer and inner BSG curve lengths were performed after 3-dimensional reconstruction of the serial computed tomography angiography scans. The results of the measurements for the main devices, the TVs, and the bridging stent-grafts were compared using univariable and multivariable analysis. Results: Of the 140 BSGs examined (74 V12s and 66 BeGs), 393 measurements (38 celiac trunks, 102 superior mesenteric arteries, 121 left renal arteries, and 132 right renal arteries) were analyzed. The outer/inner BSG curve length ratio was larger after implantation of Zenith devices compared with Anaconda (p<0.001). The vessel shift distal to the BSG was significantly associated with the interaction of the TV and type of BSG only in the univariable analysis (p=0.001). There were no significant changes of the TV deviation at the aortic origin. Only the outer BSG curve length was significantly associated with TV complications (p=0.033). Median follow-up was 24 months (range 2-61). The BSG curve length ratio showed a significant increase over time (p<0.001) but did not differ between the BeG and V12 (p=0.381). Conclusion: No difference was found between the V12 and the BeG stent-grafts regarding anatomical TV changes during midterm follow-up after fEVAR. Both stent-grafts adapt to the TV anatomy over time, and moderate anatomical changes seem to be tolerated without increasing the risk for TV complications. The type of main device also influences the TV anatomy.

Accuracy of implementing principles of fusion imaging in the follow up and surveillance of complex aneurysm repair

Fusion imaging is standard for the endovascular treatment of complex aortic aneurysms, but its role in follow up has not been explored. A critical issue is renal function deterioration over time. Renal volume has been used as a marker of renal impairment; however, it is not reproducible and remains a complex and resource-intensive procedure. The aim of this study is to determine the accuracy of a fusion-based software to automatically calculate the renal volume changes during follow up. In this study, computerized tomography (CT) scans of 16 patients who underwent complex aortic endovascular repair were analysed. Preoperative, 1-month and 1-year follow-up CT scans have been analysed using a conventional approach of semi-automatic segmentation, and a second approach with automatic segmentation. For each kidney and at each time point the percentage of change in renal volume was calculated using both techniques. After review, volume assessment was feasible for all CT scans. For the left kidney, the intraclass correlation coefficient (ICC) was 0.794 and 0.877 at 1 month and 1 year, respectively. For the right side, the ICC was 0.817 at 1 month and 0.966 at 1 year. The automated technique reliably detected a decrease in renal volume for the eight patients with occluded renal arteries during follow up. This is the first report of a fusion-based algorithm to detect changes in renal volume during postoperative surveillance using an automated process. Using this technique, the standardized assessment of renal volume could be implemented with greater ease and reproducibility and serve as a warning of potential renal impairment.