Narrow Bifurcation Research Articles

Nano-crush technique in narrow-angle (

Bifurcation stenting techniques are still refining and under testing. Nano-crush is a novel technique which allow minimum protrusion of side branch struts at the ostium. To demonstrate the efficacy of Nano-crush technique in narrow-angle bifurcation (<70°) using bench test model, 3D reconstruction of the stent structure, computational fluid dynamics study and a clinical follow-up. This was a retrospective observational single-center study which included 40 patients who underwent angioplasty using Nano-crush technique for de-novo complex coronary bifurcation lesions with narrow bifurcation angle (<70°) between April-2016 to March-2019. The in-vitro bench test and computational fluid dynamics analysis were performed using a bifurcation model designed. The clinical primary endpoint was major adverse cardiac events (MACE), defined as a composite of cardiac death, myocardial infarction, and target lesion revascularization (TLR) at one-year angiographic follow-up. The reconstructed results of in-vitro bench test showed minimum length of stent struts moving away from the rounded side branch ostium. The mean age of patients was 62.8±7.98 years (32 male) and presented 100% procedural success. The mean bifurcation angle was 47.3±9.2°. The MACE was reported in four (10%) patients which included one (2.5%) death and three (7.5%) TLR at the mean follow-up of 35.54±12.31 months. No significant correlation between occurrence of MACE and gender, age, comorbidities and bifurcation angle was reported. The Nano-crush technique demonstrated least metal load around carina and abnormal flow dynamics in narrow angle (<70°) bifurcation lesions and also reported favorable long-term clinical outcomes.

Hemodynamic Comparision Between a Classic Bifurcated Endograft and a Customized Model With “Dog-bone”-shaped Limbs

Introduction - The “customized” endovascular concept for treatment of aneurysms with challenging anatomies focuses on the construction of individualized endograft designs to adapt to patient-specific needs. Among these patterns, the endograft design with “dog-bone”-shaped limbs (DB) presents large diameter at the proximal and distal end of the iliac limbs with significant narrowing at the middle segment, offering a solution for aneurysms with extremely narrow bifurcation. Aim of this computational simulation study was to compare the displacement forces between the classic-bifurcated endograft model and a DB model of equal total length. Methods - A 3D model was constructed using appropriate commercially available validated software (ANSYS ICEM, Ansys Inc., Canonsburg, PA, USA). Inlet and outlet diameters were 28mm and 14mm, respectively. The total length of both models was kept constant to 180cm but with shorter main body by 20cm in the DB model. Accordingly, the iliac limbs of the DB model presented a 9mm stenosis over a 30mm-segmental length in the mid-portion of the limbs. The displacement forces were estimated during a cardiac cycle at three segments (main-body, bifurcation and iliac limbs) of both models with Computational Fluid Dynamics analysis. Results - The DB accommodation was associated with higher forces at the main-body (range 3.15-4.9Ν) compared to the classic configuration (1.56-2.34N). On the contrary, the forces at the bifurcation (3.81-5.98N vs. 3.76-5.54N) as well as at the iliac limbs (0.34-0.85N vs. 0.49-0.74N) were comparable for both models (Figure 1). Conclusion - The DB accommodation seems to correlate with higher displacement forces at the main-body of aortic endografts compared to the classic bifurcated design. Consequently, regular imaging follow-up of the DB design deems necessary to delineate its mid- and long-term hemodynamic and clinical performance.

Can vessel diameters, diameter ratios, and vessel angles predict the development of anterior communicating artery aneurysms: A morphological analysis

The anterior communicating artery (AcomA) junction is the most common location for cerebral aneurysms. This might because of increased vascular wall stress due to the complex structure of the junction. The aim of this study investigate the effect of morphological parameters in the development of AcomA aneurysms.This retrospective study was approved by the institutional ethics committee. A retrospective analysis of our hospital database was performed to identify patients with AcomA aneurysms. Patients with normal computed tomography angiography (CTA) examinations were enrolled in the study as the control group. The control group was similar to the patient group in gender and age. Morphological parameters (vessel diameters, vessel diameter ratios, and vessel angles) on the same side (ipsilateral) and on the opposite side (contralateral) of the patients with aneurysm, and morphological parameters of the control group were compared. A total of 171 subjects were involved in the study (86 patients with aneurysms and 85 patients in the control group). Multivariate regression analysis revealed that the ipsilateral A1–A2 angle (OR: 0.932; 95% CI: 0.903–0.961; p < 0.001), the ipsilateral A1/A2 vessel diameter ratio (OR: 27.725; 95% CI: 1.715–448.139; p = 0.019), and the contralateral internal carotid artery (ICA)/A1 ratio (OR: 11.817; 95% CI: 2.617–53.355; p = 0.001) were significant morphological predictors for developing an aneurysm.An increased contralateral ICA/A1 ratio, an increased ipsilateral A1/A2 vessel diameter ratio, and a narrow bifurcation angle are significant predictors for developing an aneurysm. Therefore, in patients with clinical risk factors these parameters may be interpreted as additional morphological risk factors for developing an aneurysm.

Computational Comparison Between a Classic Bifurcated Endograft and a Customized Model With “Dog Bone”–Shaped Limbs

Purpose: To use computational simulations to compare the hemodynamic characteristics of a classic bifurcated stent-graft to an equally long endograft design with “dog bone”–shaped limbs (DB), which have large diameter proximal and distal ends and significant narrowing at the midsection to accommodate aneurysms with an extremely narrow bifurcation. Materials and Methods: A 3-dimensional model was constructed using commercially available validated software. Inlet and outlet diameters were 28 and 14 mm, respectively. The total length of both models was kept constant to 180 mm, but the main body of the DB model was 20 mm shorter than the bifurcated endograft. The iliac limbs of the DB model had a 9-mm stenosis over a 30-mm segmental length in the midsection. Flow was quantified by time-averaged wall shear stress, oscillatory shear index (OSI), and relative residence time (RRT). The displacement forces in newtons (N) and maximum wall shear stress (WSS) in pascals (Pa) were compared during a cardiac cycle at 3 segments (main body, bifurcation, and iliac limbs) of both models with computational fluid dynamics analysis. Results: The DB accommodation was associated with higher forces at the main body (range 3.15–4.9 Ν) compared with the classic configuration (1.56–2.34 N). On the contrary, the forces at the bifurcation (3.81–5.98 vs 3.76–5.54 N) and at the iliac limbs (0.34–0.85 vs 0.49–0.74 N) were comparable for both models. Accordingly, maximum WSS was detected at the iliac sites for both models throughout the cardiac cycle. The highest values were detected at peak systole and equaled 26.6 and 12 Pa for the DB and bifurcated configurations, respectively. The narrow segments in the DB model displayed high stress values but low OSI and very low RRT. Conclusion: The DB accommodation seems to correlate with higher displacement forces at the main body and higher stresses at the iliac limbs. Consequently, regular imaging follow-up of the DB design deems necessary to delineate its mid- and long-term clinical performance.

Endovascular treatment of abdominal aortic aneurysms with narrow aortic bifurcation using Excluder bifurcated stent grafts

ObjectiveThis study investigated the influence of the aortic bifurcation anatomy on the endovascular treatment of abdominal aortic aneurysms using Excluder (W. L. Gore & Associates, Flagstaff, Ariz) bifurcated stent grafts. MethodsThis was a retrospective single-center study of patients treated with the Excluder stent graft. Analysis included anatomical factors of the aortic bifurcation (aortic bifurcation diameter [ABD], calcification, thrombus), characteristics of the stent graft limbs (sum of stent graft limbs diameters [SLD]), and the SLD/ABD ratio. Narrow bifurcation was defined as ABD <20 mm. Primary outcomes were intraoperative stenosis, need for additional intraoperative measures, limb stenosis, and occlusion during follow-up. ResultsThe study included 232 patients. Mean ABD was 24.6 ± 6 mm, with 53 patients (23%) presenting with narrow bifurcation (range, 12.5-19.5 mm). Median SLD in these patients was 28 mm, and the SLD/ABD ratio was 1.64. Calcification involving >50% of the bifurcation circumference was present in 32% of the patients, with 17% presenting thrombus in this area. Of 53 patients with narrow bifurcation, intraoperative stenosis >50% occurred in three (5.7%), which required adjunctive treatment. Computed tomography at 1 month showed limb stenosis >50% in nine patients (17%). No limb occlusions were recorded with a median follow-up of 34 months. Multivariate analysis of the overall series showed a higher risk of limb stenosis on the computed tomography at 1 month in patients with peripheral artery disease (hazard ratio [HR], 5.3; 95% confidence interval [CI], 1.2-24.4; P = .032), narrow bifurcation (HR, 5.7; 95% CI, 2-15.8; P = .001), higher SLD/ABD ratio (HR, 29.3; 95% CI, 4-215.2; P = .001), and calcium >50% (HR, 3; 95% CI, 1.1-8; P = .03), and lower in bifurcations with thrombus (HR, 0.3; 95% CI, 0.1-0.8; P = .017). ConclusionsAbdominal aortic aneurysms with narrow bifurcation can be treated with the bifurcated Excluder device without additional adjunctive measures. The presence of limb stenosis during follow-up is not associated with occlusion. Long-term follow-up studies are needed to confirm these results.

Experimental investigation on blockage boundary for pneumatic conveying of powders in narrow bifurcation slits

ABSTRACTTo investigate the blockage characteristics for dense-phase pneumatic conveying in narrow bifurcation slits, a study on the blockage boundary conditions of powders was undertaken. The results show that the solid mass flow rate for blockage increases with superficial air velocity, and the variation trend can be divided into three typical stages. Besides the relationship between the solid loading ratio and superficial air velocity for blockage in the bifurcation slit displays a “S” shape with the increase of air velocity, the solid loading ratio increases, then decreases, finally increases, and in each stage above, the relationship between the two approximately meets power function, respectively. According to the “S” shape relationship, the formula used for blockage boundary [Setia, Mallick, Wypych, and Pan (2013). Validated scale-up procedure to predict blockage condition for fluidized dense-phase pneumatic conveying systems, Particuology, 11, 657–663] was modified into piecewise function for bifurcation slits. In addition, with the increase of the bifurcation angle and conveying pressure, the superficial air velocity decreases, while the solid mass flow rate and the critical solid loading ratio increase. The research work could help understand the blockage theory of the dense-phase pneumatic conveying.

Food intake and the kidney: The right amounts at the right times

Food intake and the kidney: The right amounts at the right times