Bifurcation Angle Research Articles

Impact of left coronary artery bifurcation angle on computed tomography derived fractional flow reserve in normal coronary artery disease

Abstract Funding Acknowledgements Type of funding sources: None. Background Computed-tomography (CT) derived fractional-flow-reserve (FFRCT) decreases from the proximal to the distal part of vessel due to the influence of various factors. The energy loss due to the bifurcation angle may potentially contribute to a progressive FFRCT decline. However, the association of the bifurcation angle with FFRCT is still not entirely understood. Purpose This study aimed to investigate the impact of various bifurcation angles on FFRCT decline below the clinically crucial pathological value of 0.80 in normal coronary arteries. Methods A total of 83 consecutive patients who underwent both CT angiography including FFRCT and invasive coronary angiography, resulting in normal coronary arteries were evaluated. ΔFFRCT was defined as the magnitude of the change in FFRCT from the proximal to the distal vessel in the left anterior descending (LAD) and left circumflex (LCX). Both LAD angle and LCX bifurcation angle were measured as the crossing angle between the centrelines of the left main trunk and each coronary artery (LAD or LCX) on the 3-dimensional volume rendered image of the coronary artery tree (Figure 1). Vessel length, lumen volume, non-calcified plaque volume, and calcified plaque volume were assessed. Results Bifurcation angle was significantly lower in LAD angle (LAD angle, 31.1 ± 6.6°; LCX angle, 42.8 ± 14.9°, p < 0.0001). FFRCT showed a continuous gradual decline from the proximal to the distal in both LAD (from 0.95 ± 0.03 to 0.81 ± 0.06) and LCX (from 0.96 ± 0.03 to 0.88 ± 0.06). ΔFFRCT was significantly greater in LAD angle (LAD angle, 0.13 ± 0.06; LCX angle, 0.08 ± 0.05, p < 0.0001) ΔFFRCT was significantly correlated with each bifurcation angle (LAD angle, r = 0.35, p = 0.001; LCX angle, r = 0.26, p = 0.02) and vessel length (LAD angle, r = 0.30, p = 0.005; LCX angle, r = 0.49, p < 0.0001) (Figure 2A). In LAD, vessel length was the strongest predictor for distal FFRCT of ≤ 0.80 (β-coefficient = 0.56, p = 0.0002), immediately followed by the bifurcation angle (β-coefficient = 0.24, p = 0.02). The bifurcation angle was a good predictor for a distal FFRCT ≤ 0.80 (LAD angle, cut-off 31.0°, AUC 0.70, 95% CI 0.58–0.83, sensitivity 74%, specificity 68%; LCX angle, cut-off 52.6°, AUC 0.86, 95% CI 0.76–0.96, sensitivity 88%, specificity 85%) (Figure 2B). Conclusions The change in FFRCT depended on the bifurcation angle. In normal coronary arteries, vessel length was the most influential factor on FFRCT, immediately followed by the bifurcation angle.

Diverse changes of ramus coronary artery on computed tomography derived fractional flow reserve due to ramus artery in normal coronary artery disease

Abstract Funding Acknowledgements Type of funding sources: None. Background The ramus artery contributes to the development of turbulence, which may influence computed tomography (CT) derived fractional flow reserve (FFRCT) even without coronary artery disease. The relationship between ramus-induced turbulence and FFRCT is unclear. Purpose To investigate the effect of the ramus artery on FFRCT in normal coronary arteries. Methods A total of 120 consecutive patients who underwent both CT angiography including FFRCT and invasive coronary angiography, resulting in < 20% coronary artery stenosis were evaluated. The patients were divided into three groups: absent-ramus (n = 72), small-ramus that could not be analysed by FFRCT (n = 18), and large-ramus that could be analysed by FFRCT (n = 30). FFRCT was measured at the proximal and distal segments of the left anterior descending (LAD), left circumflex (LCX), and ramus artery (in absent-ramus group, FFRCT was measured at just above the bifurcation between LAD and LCX) were measured. The proximal FFRCT segment (proximal LAD, yellow circle; proximal Ramus or just above the bifurcation angle, yellow square; proximal LCX, yellow triangle) was measured at the same level of each vessel and the distal segment (distal LAD, white circle; distal ramus, white square; distal LCX, white triangle) was measured at obtained by the FFRCT analysis (Figure 1). Vessel morphology (vessel length, lumen volume, plaque volume), bifurcation angle, and left ventricular mass were assessed. Results In the absent-ramus group, proximal FFRCT showed no significant difference between three vessels (LAD, 0.96 ± 0.02; MID, 0.97 ± 0.02; LCX, 0.97 ± 0.02). However, in small and large-ramus groups, proximal FFRCT was significantly higher in the ramus artery than LAD and LCX (small-ramus: LAD = 0.95 ± 0.03, Ramus = 0.97 ± 0.02, LCX = 0.95 ± 0.03; large-ramus: LAD = 0.95 ± 0.03, ramus = 0.98 ± 0.01; LCX = 0.96 ± 0.03; p < 0.05) (Figure 2). A large ramus was associated with a higher prevalence of a distal FFRCT ≤0.80 (odds ratio 7.0, 95% CI 1.2–40.1. p = 0.03). A proximal ramus diameter predicted distal FFRCT ≤ 0.80 (cut-off 2.1 mm, AUC 0.76, sensitivity 100%, specificity 52%, 95% CI 0.61–0.90). Conclusions The presence of a large-ramus artery may cause an FFRCT decline in normal coronary arteries.

Carotid geometry is independently associated with complicated carotid artery plaques.

Complicated carotid artery plaques (cCAPs) are associated with an increased risk of rupture and subsequent stroke. The geometry of the carotid bifurcation determines the distribution of local hemodynamics and could thus contribute to the development and composition of these plaques. Therefore, we studied the role of carotid bifurcation geometry in the presence of cCAPs. We investigated the association of individual vessel geometry with carotid artery plaque types in the Carotid Plaque Imaging in Acute Stroke (CAPIAS) study. After excluding arteries without plaque or with insufficient MRI quality, 354 carotid arteries from 182 patients were analyzed. Individual parameters of carotid geometry [i.e., internal carotid artery (ICA)/common carotid artery (CCA) ratio, bifurcation angle, and tortuosity) were derived from time-of-flight MR images. The lesion types of carotid artery plaques were determined according to the American Heart Association classification of lesions by multi-contrast 3T-MRI. The association between carotid geometry and a cCAP was studied using logistic regression after adjusting for age, sex, wall area, and cardiovascular risk factors. Low ICA/CCA ratios (OR per SD increase 0.60 [95%CI: 0.42-0.85]; p = 0.004) and low bifurcation angles (OR 0.61 [95%CI: 0.42-0.90]; p = 0.012) were significantly associated with the presence of cCAPs after adjusting for age, sex, cardiovascular risk factors, and wall area. Tortuosity had no significant association with cCAPs. Only ICA/CCA ratio remained significant in a model containing all three geometric parameters (OR per SD increase 0.65 [95%CI: 0.45-0.94]; p = 0.023). A steep tapering of the ICA relative to the CCA and, to a lesser extent, a low angle of the carotid bifurcation were associated with the presence of cCAPs. Our findings highlight the contribution of bifurcation geometry to plaque vulnerability. Thus, assessment of carotid geometry could be helpful in identifying patients at risk of cCAPs.

Rotational atherectomy to left circumflex ostial lesions: tips and tricks.

Serious complications including vessel perforation may occur during rotational atherectomy (RA) to left circumflex (LCX) ostial lesions. In fact, if perforation occurs around LCX ostium, bailout procedures including deployment of covered stents may cause fatal ischemia in the territory of left anterior descending artery, which results in broad anterior acute myocardial infarction and subsequent death. In this review article, we described tips and tricks for RA to LCX ostial lesions. First, we should cautiously decide the indication for RA to LCX ostial lesions, because there are several reasons to avoid RA to LCX ostial lesions. Before procedures, we should estimate the difficulty of RA to LCX ostial lesions, which is mainly determined by the combination of the bifurcation angle and the severity of stenosis. Thus, the combination of the large bifurcation angle and the tight stenosis makes RA to LCX ostial lesions most difficult. Appropriate position of guide catheter and RotaWire is a key to successful RA to LCX ostial lesions. Differential cutting is an essential concept for RA to LCX ostial lesions. However, since there is no guarantee that differential cutting always works, small burr (≤ 1.5mm) would be a safe choice as initial burr for RA to LCX ostial lesions.

Numerical modeling of varying hemodynamic features with changing internal carotid artery bifurcation angles and degrees of stenosis

Atherosclerosis is a disease clinically categorized as a silent killer as its symptoms only become pronounced after the buildup has extensively progressed. Therefore, early detection, prediction and treatment become of great priority. The focus of this study is to develop a deeper understanding of plaque formation and the role of key structural variations, specifically the bifurcation angle and degree of stenosis, on its progression in a numerical carotid artery model. A two-way coupled Fluid–Solid Interaction (FSI) numerical approach has been implemented, with the consideration of isotropic elasticity for the artery wall. Geometrically induced hemodynamic flow variations were monitored by tracking changes in hemodynamic indicators, such as the wall shear stress (WSS) and vortex structures. The numerical results demonstrate general trends of the bifurcation angle amplifying recirculation zones, reducing WSS at the sinus far walls, and inhibiting wall deformations about the apex. Meanwhile, progressive stenosis is shown to induce new vortices, increase and decrease WSS at the outer walls and the inner walls respectively, and promote larger deformations. These hemodynamic flow and structural variations hint at increased risk of further plaque buildup with the increase of bifurcation angle at lower degrees of stenosis, while an increased risk of plaque rupture was associated with higher degrees of stenosis.

Global Iliac Branch Study: Image-based Detailed Anatomic Assessment and Device Performance

Iliac branch devices are designed to preserve patency of the internal iliac artery for endovascular repair of aortoiliac aneurysms. The Global Iliac Branch Study (NCT05607277) is an international, multicenter, retrospective study of over 300 iliac branch devices with diverse use. The objective of this project was to evaluate potential anatomic determinants of adverse iliac events. Patients were included if they had both pre- and post-treatment computed tomography imaging available after implantation of a bifurcated device. Morphologic measurements included arterial diameters, stenosis, calcification, aortic and iliac bifurcation angles, and tortuosity indices (Fig), performed by a core laboratory with a standardized and validated protocol. Adverse iliac events were defined as type I or III endoleak, occlusion, device constriction (due to either narrow anatomy or another component), or clinical events requiring reintervention of the ipsilateral iliac branch system. This abstract is based on univariate analysis. Paired t test was used to compare tortuosity indices and splay angles pre- and post-treatment. Logistic regression was used to assess associations between anatomic measurements and adverse iliac events. Analysis was performed by iliac system (ie, bilaterally treated patients’ right and left sides were analyzed independently). We analyzed 297 subjects (286 males, 11 females) with 331 iliac branch devices (104 nitinol, 227 stainless steel). Mean clinical follow-up was 3.8 years. Mean baseline total iliac artery index was 1.47 (range, 1.44 to 1.50), mean baseline common iliac artery index was 1.10 (range, 1.09 to 1.12). Changes in iliac artery tortuosity indices and aortic and iliac splay angles are reported in Table. Anatomy is significantly straightened with treatment in all devices. There were 54 adverse iliac events in 44 systems, requiring 35 reinterventions (median time to reintervention, 41 days; range, 0 days to 6.2 years). There were 18 endoleaks (17 type I, 1 type III), 29 occlusions, and five device constrictions. In nitinol devices, diameter of the internal iliac landing zone <10 mm and non-conformability (reduction in total iliac index beyond 15%) were associated with adverse iliac events (odds ratio [OR], 14; P = .016 and OR, 7.8; P = .021, respectively.) In the stainless steel devices, no significant univariate associations were found with anatomic measurements. These results suggest that purpose-built iliac branch devices are highly efficacious in treating tortuous iliac anatomy, with a high patency rate and low reintervention rate. Some anatomic factors are strongly predictive of adverse iliac events in nitinol devices.TableChanges in iliac artery tortuosity indices and splay anglesPre-treatment [95% CI]Post-treatment [95% CI]P-valueAll iliac branch systems (n = 331) Total iliac artery index1.47 [1.44-1.50]1.31 [1.28-1.33]<.0001 Common iliac artery index1.10 [1.09-1.12]1.04 [1.03-1.04]<.0001 Aortic splay angle58.3 [56.2-60.5]41.4 [39.6-43.1]<.0001 Iliac branch splay angle52.3 [49.7-54.8]47.4 [45.3-49.6]<.0001Nitinol iliac branch systems (n = 104) Total iliac artery index1.53 [1.47-1.60]1.44 [1.38-1.50]<.0001 Common iliac artery index1.13 [1.10-1.16]1.06 [1.05-1.08]<.0001 Aortic splay angle56.4 [52.1-60.8]45.3 [42.3-48.3]<.0001 Iliac branch splay angle48.0 [43.5-52.5]44.5 [40.7-48.3].0633Stainless steel iliac branch systems (n = 227) Total iliac artery index1.44 [1.42-1.47]1.25 [1.23-1.26]<.0001 Common iliac artery index1.09 [1.07-1.10]1.03 [1.02-1.03]<.0001 Aortic splay angle59.2 [56.8-61.7]39.6 [37.5-41.7]<.0001 Iliac branch splay angle54.2 [51.1-57.3]48.8 [46.2-51.4]<.0001CI, Confidence interval. Open table in a new tab

Self-ignition and flow characteristics of pressurized hydrogen in Y-shaped tubes

The geometrical diversion of combustible gas molecules notably affects their self-ignition in high-pressure tubes. This study investigates the propagation of shock waves and flame induced by a sudden pressure release of hydrogen in various Y-shaped tubes. The impact of the initial burst pressure, downstream tube length, and bifurcation angle (60°, 120°) were analyzed by recording the pressure signals, photoelectric curves, and jet fire evolution. The results showed that the gas diversion caused by the Y-shaped structure significantly reduces the maximum overpressure of the hydrogen jet, the intensity, and the velocity of the leading shock wave. Also, it was indicated that increasing the Y-shaped tube's length downstream of the bifurcation point could enhance the strength of leading and reflected shock waves after the Y-bifurcation, making self-ignition more likely to happen. Applying a 60°-bifurcation angle could create stronger leading and reflected shock waves during the propagation downstream of the bifurcation point, while a 120°-bifurcation angle could make a more substantial reflected shock wave propagating upstream. It leads to the re-ignition downstream of the bifurcation in the 60°-bifurcation tube after the flame quenching and stronger far-field jet fire outside the tube.

Fabrication Procedure for a 3D Hollow Nanofibrous Bifurcated-Tubular Scaffold by Conformal Electrospinning

Electrospinning has shown great potential for the fabrication of 3D nanofibrous tubular scaffolds for bifurcated vascular grafts. However, fabrication of complex 3D nanofibrous tubular scaffolds with bifurcated or patient-specific shapes remains limited. In this study, a 3D hollow nanofibrous bifurcated-tubular scaffold was fabricated by the uniform and conformal deposition of electrospun nanofibers via conformal electrospinning. By conformal electrospinning, electrospun nanofibers are conformally deposited onto a complex shape, such as the bifurcated region, without large pores or defects. Owing to conformal electrospinning, a corner profile fidelity (FC), a measure of conformal deposition of electrospun nanofibers at the bifurcated region, was increased 4 times at the bifurcation angle (θB) of 60°, and all FC values of the scaffolds reached 100%, regardless of the θB. Furthermore, the thickness of the scaffolds could be controlled by varying the electrospinning time. Leakage-free liquid transfer was successfully achieved owing to the uniform and conformal deposition of electrospun nanofibers. Finally, the cytocompatibility and 3D mesh-based modeling of the scaffolds were demonstrated. Thus, conformal electrospinning can be used to fabricate leakage-free and complex 3D nanofibrous scaffolds for bifurcated vascular grafts.

Internal Acoustic Meatus Localization During Anterior Petrosectomy: A Novel Technique

Anterior petrosectomy demands localization of the internal auditory canal (IAC) for safe bone drilling and maximum exposure. Various techniques have been described in the literature, each with shortcomings. We propose a new technique to localize the internal acoustic meatus (IAM) using more consistent anatomical landmarks. The study was done in three phases. In phase-I (radiological), computed tomography scan heads of fifty patients (100 sides) were analyzed. Arcuate eminence-Greater Superficial Petrosal Nerve bifurcation angle(Garcia-Ibanez technique), Arcuate eminence-IAC angle(Fisch technique) and a new angle formed between foramen ovale (FO) and foramen spinosum (FS) line, and FS and IAM line (FO-FS-IAM angle) was measured. The mean, standard deviation, and variance were calculated. In phase-II (cadaveric), the FO-FS-IAM angle was measured on five (10 sides) dry skulls. In phase-III (clinical), the IAM was localized using the FO-FS-IAM angle in 13 patients. The mean angle between arcuate eminence and Greater Superficial Petrosal Nerve (Garcia-Ibanez technique) was 126.20±11.63°(range 106-156) with a variance of 135.20. The mean bifurcation angle was 63±5.81°(range 53-78). By the Fisch technique, the mean arcuate-IAM angle was 73.5±11.70°(range 51-105) with a variance of 137.18. By our technique, the mean FO-FS-IAM angle was 94.72±5.89°(range 84-108). The variance was 34.73. The mean FO-FS-IAM angle on dry skulls was identical (95±1.97°) to our radiological measurements. This angle was reproduced reliably in clinical cases for localizing the IAM during anterior petrosectomy. The FO-FS-IAM angle variance was much lower than the analogous angles measured by Garcia-Ibanez and Fisch techniques, making it a more reliable and effective tool for localizing the IAM.

Detection of tracheal branching with computerized tomography: The relationship between the angles and age-gender.

The data obtained on the anatomical knowledge of the tracheobronchial system can be used for diagnosis, treatment and interventional interventions in areas such as anesthesia, thoracic surgery, pulmonary physiology. To determine the tracheobronchial branching angles in pediatric and adult populations by using the multislice computed tomography (CT) and minimum intensity projection (MinIP) technique, which is a non-invasive method. Our study was carried out retrospectively. Patients who underwent contrast and non-contrast CT examination, whose anatomically and pathophysiologically good tracheobronchial system and lung parenchyma images were obtained, were included in the study. Measurements were made in the coronal plane of the lung parenchyma. In the coronal plane, right main bronchus-left main bronchus angle, right upper lobe bronchus-intermedius bronchus angle, right middle lobe bronchus-right lower lobe bronchus angle, left upper lobe bronchus-left lower lobe bronchus angle were measured. The study population consisted of 1511 patients, 753 pediatric (mean age: 13.4 ± 4.3; range: 1-18 years) and 758 adults (mean age: 54.3 ± 17.3; range: 19-94 years). In our study, tracheal bifurcation angle was found to be 73.3° ± 13.7° (59.6°-87°) in the whole population. In the pediatric group, the right-left main coronal level was found to be higher in boys compared to girls (74.6° ± 12.9° vs 71.2° ± 13.9°, P = 0.001). In the adult group, the right-left main coronal level was found to be lower in males compared to females (71.9° ± 12.9° vs 75.8° ± 14.7°, P < 0.001). Our study, with the number of 1511 patients, is the first study in the literature with the largest number of patient populations including pediatric and adult demographic data, measuring the angle values of the tracheobronchial system using multislice CT and MinIP technique. Study data will not only be a guide during invasive procedures, but it can also guide studies to be done with imaging methods.

Restenosis Investigation of Two-Stent Placement in the Artery Bifurcation with Different Stenting Techniques Using Computational Fluid Dynamics Analysis

The in-stent restenosis may still occur in patients with a coronary bifurcation stenting. The purpose of this study is to investigate the restenosis effect in the relationships between the bifurcation angles of the coronary artery and three types of stenting techniques (T-stenting, Culotte, and Kissing techniques), for comparing two kinds of arterial shapes using computational fluid dynamics (CFD) analysis. The finite element models of two types of the coronary arteries were reconstructed using stereolithography (STL) data of an artificial artery from reverse engineering laser scanning, and then each artery was further modified to add three kinds of the bifurcation angles, including 80°, 113°, and 142°. The low TAWSS of the two arteries were mainly concentrated at the LCX branch; a more essential discovery was that the low TAWSS area ration was in proportion to the bifurcation angle. The smallest low TAWSS of the T-stenting and Kissing techniques was detected in the arteries A and B, respectively. Both Culotte and Kissing techniques always showed a higher OSI than the T-stenting, and a high OSI was meaningfully located at the LCX branch. The CFD study concluded that the large bifurcation angle of an artery using a long stent at the LCX side branch with the T-stenting technique has a high risk of stenting restenosis.

In silico simulation of hepatic arteries: An open-source algorithm for efficient synthetic data generation.

In silico testing of novel image reconstruction and quantitative algorithms designed for interventional imaging requires realistic high-resolution modeling of arterial trees with contrast dynamics. Furthermore, data synthesis for training of deep learning algorithms requires that an arterial tree generation algorithm be computationally efficient and sufficiently random. The purpose of this paper is to provide a method for anatomically and physiologically motivated, computationally efficient, random hepatic arterial tree generation. The vessel generation algorithm uses a constrained constructive optimization approach with a volume minimization-based cost function. The optimization is constrained by the Couinaud liver classification system to assure a main feeding artery to each Couinaud segment. An intersection check is included to guarantee non-intersecting vasculature and cubic polynomial fits are used to optimize bifurcation angles and to generate smoothly curved segments. Furthermore, an approach to simulate contrast dynamics and respiratory and cardiac motion is also presented. The proposed algorithm can generate a synthetic hepatic arterial tree with 40 000 branches in 11 s. The high-resolution arterial trees have realistic morphological features such as branching angles (MAD with Murray's law ), radii (median Murray deviation ), and smoothly curved, non-intersecting vessels. Furthermore, the algorithm assures a main feeding artery to each Couinaud segment and is random (variability=0.98 ± 0.01). This method facilitates the generation of large datasets of high-resolution, unique hepatic angiograms for the training of deep learning algorithms and initial testing of novel 3D reconstruction and quantitative algorithms designed for interventional imaging.

Dynamic monitoring of morphological and hemodynamic evolution of small cerebral aneurysms

Highlights. Small cerebral aneurysms (&lt;3 mm), which make up the majority of aneurysms, rupture more frequently, although medium (&gt;3 mm) and giant (&gt;15 mm) aneurysms and have a higher risk of rupture. This article proves for the first time that the rupture risk criteria developed for giant cerebral aneurysms do not work for small aneurysms. The development of small aneurysms in patients was analyzed and measured morphological features of aneurysms were compared with their calculated hydrodynamic characteristics.Aim. To study the dynamics of development of small cerebral aneurysms, to assess the applicability of existing methods for calculating the risk of rupture, to formulate new clarifying hypotheses for calculating the risk of rupture of small cerebral aneurysms.Methods. Patient data were provided by the Federal Center for Neurosurgery, Novosibirsk. CT angiography was performed using a Philips Ingenuite CT scanner (Philips Medical Systems, USA, 128 slices). Aneurysm size dynamics was assessed by measuring three main sizes with an accuracy of 0.1 mm using the IntelliSpace Portal Philips software environment. Numerical calculations were carried out using ANSYS CFX 2020R2.Results. Hemodynamic characteristics change according to the changes of the aneurysm dome. In the case when morphological characteristics of the aneurysm have not changed, a change in the geometry of the patient's circle of Willis (coW) is observed: the curvature of the arteries, the angles of bifurcations (the structure of coW remained unchanged). The PHASES score (absolute risks of rupture for aneurysms) was found to be unusable for the considered aneurysms.Conclusion. This work formulates and morphologically and hydrodynamically confirms for the first time in the volunteers that the change in risk estimates for such aneurysms is fundamentally affected, even insignificantly, by the change in the circle of Willis: a change in the curvature of individual segments of the cerebral arteries, as well as the angles of their bifurcations. The results obtained are aimed at modifying the existing risk criteria for rupture of cerebral aneurysms.

Influence of abdominal aortic aneurysm shape on hemodynamics in human aortofemoral arteries: A transient open-loop study

New imaging methods have enabled the detection of unruptured abdominal aortic aneurysms (AAA). It is necessary to develop appropriate mathematical models for rupture prediction to allow a proper patient treatment plan. To provide valid hemodynamic parameters, high-fidelity numerical models with patient-specific boundary conditions are needed. Researchers have pointed out in recent research articles and reviews that those morphological parameters, such as shape, dilation ratio, neck angle, common iliac bifurcation angle, and AAA type, consistently correlate with the rupture mechanism. However, it is unclear how morphological indicators affect hemodynamics-based computational fluid dynamics predictions. The present work investigates the influence of AAA shape on local and global hemodynamics parameters and rupture predictions. Five cases of magnetic resonance imaging scan-based data for patient-specific aortofemoral artery modeling are explored. The inflow conditions are patient-specific, and an open loop system has been considered to model all five cases. Hemodynamics parameters in pulsating conditions, such as wall shear stress (WSS), velocity contour, time average WSS (TAWSS), oscillatory shear index (OSI), vorticity, and streamlines, are computed and investigated. Both maximum dilation diameter and aneurysm neck angle are found to have substantial effects on local hemodynamics parameters. The magnitude of WSS, TAWSS, and OSI increases and decreases non-linearly with a change in maximum diameter during the cardiac process. Also, aneurysms with doubly titled and completely saccular shape show complex streamlines, low WSS, and high residence time in the sac area of the wall.

180-degre carotid bifurcation with an internal carotid artery aneurysm.

Internal carotid artery (ICA) aneurysm is a rare pathology. In the clinical case we present, the patient had an ICA aneurysm as well as a rare anatomical variant of the carotid bifurcation. We present the case of a 45year old man, who had two episodes of TIA revealed by loss of mind. Computed tomography revealed the fusiform aneurysm of a left ICA in the first segment with maximal diameter of 16mm. There were no thrombotic mass in the dilated area. The carotid bifurcation angle was 180 degree. Although the aneurysm did not contain a thrombus mass, it was considered the source of the TIA because of turbulent blood flow. Distal and proximal ligation was performed. A 5-cm long graft from the great saphenous vein was used for ICA revascularization from common carotid artery. In our case, geometry of carotid bifurcation may have contributed to the ICA aneurysm, although there is no evidence for this correlation.

Investigation on the effect of tree-like bifurcation fracture networks properties on the EGS thermal recovery performance

In order to truly describe the fracture network of the enhanced geothermal system (EGS), the tree-like fractal bifurcation theory is used to reflect the heterogeneity of the fracture network. The temperature-seepage coupling model is set up, the influences of bifurcation fracture networks and well layouts on thermal recovery performance are analyzed. The results show that the increase of bifurcation level, angle and length ratio all have positive effect on the thermal recovery performance. A higher bifurcation level produces a greater number of secondary fractures, a higher bifurcation angle and length ratio leads to a relatively spread fracture distribution, thereby improving thermal recovery performance. A higher aperture ratio is prone to premature thermal breakthrough, which limits the thermal recovery process. Under the conditions and scopes of our study, the optimal bifurcation level is 5, angle is 120°, length ratio is 0.55 and aperture ratio 0.4. This study provides some good guidance of efficient fracturing design for better thermal recovery performance.

Influence of Morphological Parameters on the Flow Development within Human Airways

Anatomical airways parameters, such as length, diameter and angles, have a strong effect on the flow dynamics. Aiming to explore the effect of variations of the bifurcation angle (BA) and carina rounding radius (CRR) of lower human airways on respiratory processes, numerical simulations of airflow during inhalation and exhalation were performed using synthetic bifurcation models. Geometries for the airways models were parameterized based on a set of different BA’s and several CRR’s. A range of Reynolds numbers (Re), relevant to the human breathing process, were selected to analyze airflow behavior. The numerical results showed a significant influence of BA and the CRR on the development of the airflow within the airways, and, therefore, affecting the following relevant features of the flow: the deformation of velocity profiles, alterations of pressure drop, flow patterns, and, finally, enhancement or attenuation of wall shear stresses (WSS) appearing during the regular respiratory process. The numerical results showed that increases in the bifurcation angle value were accompanied by pressure increases of about 20%, especially in the regions close to the bifurcation. Similarly, increases in the BA value led to a reduction in peak shear stresses of up to 70%. For the ranges of angles and radii explored, an increase in pressure of about 20% and a reduction in wall shear stress of more than 400% were obtained by increasing the carina rounding radius. Analysis of the coherent structures and secondary flow patterns also revealed a direct relationship between the location of the vortical structures, the local maxima of the velocity profiles and the local vorticity minima. This relationship was observed for all branches analyzed, for both the inhalation and exhalation processes of the respiratory cycle.

Dynamic assessment of the left main-left circumflex bending angle: Implications for ostial left circumflex artery in-stent restenosis after successful two-stent PCI

BackgroundTwo-stent techniques for percutaneous coronary intervention (PCI) on left main (LM) bifurcation (LMB) lesions are associated with an increased risk of in-stent restenosis (ISR) at left circumflex artery (LCx) ostium but the underlying mechanisms are incompletely understood. This study sought to investigate the association between cyclic change of LM-LCx bending angle (BALM-LCx) and the risk of ostial LCx ISR following two-stent techniques. MethodsIn a retrospective cohort of patients undergoing two-stent PCI for LMB lesions, BALM-LCx and distal bifurcation angle (DBA) were computed with 3-dimensional angiographic reconstruction. The analysis was performed both at end-diastole and end-systole, and the angulation change throughout the cardiac cycle was defined as the cardiac motion-induced angulation change (∆CAngle). ResultsA total of 101 patients were included. The mean pre-procedural BALM-LCx was 66.8 ± 16.1° at end-diastole and 54.1 ± 13.3° at end-systole with a range of 13.0 ± 7.7°. Pre-procedural ∆CBALM-LCx > 16.4° was the most relevant predictor of ostial LCx ISR (adjusted OR 11.58, 95% CI 4.04–33.19; p < 0.001). Post-procedural ∆CBALM-LCx > 9.8° and stent-induced diastolic BALM-LCx change > 11.6° were also related with ostial LCx ISR. DBA was positively correlated with BALM-LCx and showed a weaker association of pre-procedural ∆CDBA > 14.5° with ostial LCx ISR (adjusted OR 6.87, 95% CI 2.57–18.37; p < 0.001). ConclusionsThree-dimensional angiographic bending angle is a feasible and reproducible novel method for LMB angulation measurement. A large pre-procedural cyclic change of BALM-LCx was associated with an increased risk of ostial LCx ISR following two-stent techniques.

Relationship between left main trifurcation angulation, calcium score, and the onset of plaque formation.

It has been suggested that a wider left main (LM) bifurcation angle is associated with the development of atherosclerosis. However, the relationship between LM trifurcation angulation and atherosclerosis has not been investigated. We aimed to investigate the relationship between LM trifurcation angulation and the presence of calcifications in the left coronary artery (LCA) using coronary computed tomography angiography (CCTA). Furthermore, we assessed the relationship between LM trifurcation angulation and the age at which calcification originated. The LM trifurcation angle and coronary artery calcium (CAC) score in the LCA were measured. Based on observational studies, we assumed that CAC progression is 25% per year on average. Then, we calculated the age at which LCA CAC scores were lower than 0.1 Agatston units. Of 266 patients, 52 patients (mean age of [standard deviation, SD] 61 [6] years; 28 men) with LM trifurcation were included in the study. Calcified plaques occurred in the LCA in 36 patients (69.2%). The mean LM trifurcation angle in patients with a diseased LCA was wider than that in patients with a normal LCA (108° [33°] vs. 91° [28°]; P = 0.04). Pearson correlation coefficient showed that the wider the LM trifurcation angle was, the earlier the calcification in the LCA may be expected (r = -0.34; P = 0.04 with outliers; r = -0.43; P = 0.009 without outliers). A wider LM trifurcation angle is associated with a higher LCA CAC score. Moreover, the LM trifurcation angle has a significant impact on the earlier onset of atherosclerosis.

Investigation of the Relationship between Right Coronary Artery-Aorta Angle and Coronary Artery Disease and Associated Risk Factors.

At the level of the left coronary artery tree, there is evidence showing an association between bifurcation angle and coronary artery disease (CAD), and this motivated us to explore similar associations at the level of the right coronary artery (RCA). The purpose of this study was to determine whether there is a relationship between RCA-aorta angle and CAD and age, sex, body mass index, smoking status, hypertension, and high blood cholesterol. The coronary computed tomography angiography datasets and CAD risk factor checklists of 250 patients were retrospectively reviewed, with RCA-aorta angles measured via multiplanar reformation images. Independent t-tests were used to compare mean RCA-aorta angle measurements between groups, correlations between continuous variables were assessed using Pearson and Spearman correlations, and a general linear model was used to adjust for potentially confounding variables. Coronary angle measurements were conducted by two independent assessors with very strong intraclass correlation (r=0.999, p<0.001). A significantly smaller mean RCA-aorta angle was observed in the CAD group (79.07 ± 24.88°) compared to the normal group (92.08 ± 19.51°, p=0.001), in smokers (76.63 ± 22.94°) compared to non-smokers (85.25 ± 23.84°, p=0.016), and a narrow RCA-aorta angle was negatively correlated with BMI (r=-0.174, p=0.010). This study suggests a relationship between narrow RCA-aorta angles and CAD, smoking, and increasing BMI.