Arch Wall Research Articles

Magnetic resonance imaging findings in Axenfeld–Rieger syndrome

Axenfeld–Rieger syndrome (ARS) is a genetic disorder representing a disease spectrum resulting from neural crest cell maldevelopment. Glaucoma is a common complication from the incomplete formation of the iridocorneal angle structures. Neural crest cells also form structures of the forebrain and pituitary gland, dental papillae, aortic arch walls, genitalia, and long bones; therefore, patients with ARS manifest a wide range of systemic findings. To our knowledge, detailed magnetic resonance imaging findings have not been previously reported. We report a case of a 19-month-old Indian male diagnosed with ARS with emphasis on magnetic resonance imaging findings of the globes, brain, teeth, and skull base.

Successful Tocilizumab Treatment in a Child With Refractory Takayasu Arteritis

Takayasu arteritis (TA) in the child remains a therapeutic challenge because corticosteroids and conventional immunosuppressive agents are not always safe or efficacious. The complex formed by interleukin-6 (IL-6) and soluble IL-6 receptor appears to play a pivotal role in the pathogenesis of TA. We describe a favorable response to the anti-IL-6 receptor antibody tocilizumab (TCZ) in a child with aggressive and refractory TA including an assessment of the proinflammatory cytokine profile. A 3-year-old girl with TA consisting of thickening of the aortic arch wall, severe obstruction of the supra-aortic branches, and complete occlusion of both common carotid arteries failed to respond to corticosteroids, methotrexate, tumor necrosis factor α blockade, cyclophosphamide, and mycophenolate mofetil, and 3 years later, the disease remained active with severe manifestations (brain ischemia). The patient underwent percutaneous angioplasty, although significant restenosis was soon documented. After a severe relapse, the patient started TCZ infusions (8 mg/kg for 2 weeks), and a rapid clinical remission was observed, associated with a drastic reduction of inflammatory markers and IL-6 levels. Corticosteroids were withdrawn, the patient's weight and height improved, and bone mineral density values returned to normal. Two years later, TCZ infusions were extended, with no significant side effects. Cerebral ischemia resolved, and recanalization of the previously occluded supra-aortic branches was performed.

Contrast enhancement by lipid-based MRI contrast agents in mouse atherosclerotic plaques; a longitudinal study

The use of contrast-enhanced MRI to enable in vivo specific characterization of atherosclerotic plaques is increasing. In this study the intrinsic ability of two differently sized gadolinium-based contrast agents to enhance atherosclerotic plaques in ApoE(-/-) mice was evaluated with MRI. We obtained a kinetic profile for contrast enhancement, as the literature data on optimal imaging time points is scarce, and assessed the longer-term kinetics. Signal enhancement in the wall of the aortic arch, following intravenous injection of paramagnetic micelles and liposomes, was followed for 1 week. In vivo T(1)-weighted MRI plaque enhancement characteristics were complemented by fluorescence microscopy of NIR(664) incorporated in the contrast agents and quantification of tissue and blood Gd-DTPA. Both micelles and liposomes enhanced contrast in T(1)-weighted MR images of plaques in the aortic arch. The average contrast-to-noise ratio increased after liposome or micelle injection to 260 or 280% respectively, at 24 h after injection, compared with a pre-scan. A second wave of maximum contrast enhancement was observed around 60-72 h after injection, which only slowly decreased towards the 1 week end-point. Confocal fluorescence microscopy and whole body fluorescence imaging confirmed MRI-findings of accumulation of micelles and liposomes. Plaque permeation of contrast agents was not strongly dependent on the contrast agent size in this mouse model. Our results show that intraplaque accumulation over time of both contrast agents leads to good plaque visualization for a long period. This inherent intraplaque accumulation might make it difficult to discriminate passive from targeted accumulation. This implies that, in the development of targeted contrast agents on a lipid-based backbone, extensive timing studies are required.

A computational fluid dynamics study on geometrical influence of the aorta on haemodynamics

Cardiovascular diseases, such as atherosclerosis and aneurysm, are closely associated with haemodynamic factors that are governed by luminal geometry. The present work aimed to study the effect of geometrical variation of aging aortas on haemodynamics. Six aged subjects with intricate geometrical features, such as bulging or twisted supra-aortic arteries, sharply curved arch and double-curved descending aorta, were chosen from our medical database. These six geometrically variant aortas were reconstructed and the pulsatile nature of the blood flow of these subject-specific aorta models investigated using computational fluid dynamics simulations. Realistic time-dependent boundary conditions are prescribed for various arteries of the aorta models. This study suggests that haemodynamics in the human aorta is highly dependent on geometrical features. The positioning and contouring of the supra-aortic arteries may be associated with the skewness of velocity profiles. The flow profiles in the aortic arch or bends are generally skewed towards the inner curvature wall and this skewness may give rise to the formation of secondary flow in the inner curvature wall of the distal arch. The degree of vorticity in the distal aortic arch is found to be related to the arch curvature. The helical nature of aortic haemodynamics is predominant in the systole phrase when it begins with a left-handed rotation and then vanishes in the ascending aorta, whereas a right-handed rotation persists in the distal aortic arch. Lower wall shear stress is also found in the ascending regions where secondary flow is present. The aorta with an irregular contour and large degree of curvature at its arch favours the development of the intra-aortic secondary flow that subsequently relates to the pathogenesis of atheroma. The present study identifies the general trend of haemodynamic behaviours associated with various local geometrical features. Combining the knowledge of the correlation between haemodynamics and the underlying risks in the development of cardiovascular diseases, our study hopes to provide a better understanding of the relationship between aortic morphology and developing pathobiology of cardiovascular diseases. As such, early medical planning as well as surgical interventions can be designed to retard or prevent the development of cardiovascular diseases.

Innovative Use of an Amplatzer Septal Occluder for Occlusion of a Large Right Subclavian Artery Aneurysm and Reconstruction of the Posterior Aortic Arch Wall

To highlight the efficacy of the Amplatzer septal occluder in endovascular exclusion of an aberrant right subclavian artery aneurysm and reconstruction of the posterior aortic arch wall for subsequent endovascular placement of a thoracic graft. A 73-year-old lady with prohibitive surgical risk was found to have a 35 × 39 mm aberrant right subclavian artery aneurysm as well as a 7.6 cm wide thoracic aortic aneurysm. Repair of both defects was performed endoluminally with the patient awake. An Amplatzer septal occluder was used for successful exclusion of the subclavian artery. Additionally, the device enabled reconstruction of the posterior aortic arch wall, thereby providing a landing zone for subsequent placement of a custom-made thoracic endograft. The Amplatzer septal occluder provides an innovative endovascular alternative for complex, large subclavian artery aneurysms.

One-Stage Repair for Stanford Type B Aortic Dissection Concomitant with Cardiac Diseases: Open Stented Elephant Trunk Technique Combined with Cardiac Operation

We evaluated an open stented elephant trunk (sET) technique combined with cardiac operations for a one-stage treatment of patients with complicated Stanford type B aortic dissection (AoD) and cardiac diseases. Between April 2007 and March 2010, 16 patients with Stanford B AoD and cardiac diseases (mean age 49.75 ± 13.42 years) underwent sET combined with cardiac operations. Under deep hypothermic cardiac arrest (DHCA), a stented graft was directly delivered via the incision of aortic arch and the proximal graft was sutured on the normal distal aortic arch wall in a continuous circumferential full-thickness fashion. The combined cardiac operations (Bentall procedure, etc.) were performed before sET implantation while cooling. Average time of cardiopulmonary bypass, aortic cross clamping durance, and DHCA was 131.62 ± 23.85, 64.69 ± 9.72, and 21.94 ± 3.60 minutes, respectively. There were no early deaths and no neurological complications. During a follow-up of 18.69 ± 9.94 months, computed tomographic angiography was performed in all patients. Neither endoleak nor stent shifting was observed. Retrograde type A AoD was not found during follow-up. Thrombus was formed in the false lumen from the proximal descending aorta to the diaphragmatic section. The open sET technique combined cardiac procedures can reliably treat Stanford type B AoD concomitant with surgical cardiac disease in a single stage.

Finite Element Modelling of Pulsatile Blood Flow in Idealized Model of Human Aortic Arch: Study of Hypotension and Hypertension

A three-dimensional computer model of human aortic arch with three branches is reproduced to study the pulsatile blood flow with Finite Element Method. In specific, the focus is on variation of wall shear stress, which plays an important role in the localization and development of atherosclerotic plaques. Pulsatile pressure pulse is used as boundary condition to avoid flow entry development, and the aorta walls are considered rigid. The aorta model along with boundary conditions is altered to study the effect of hypotension and hypertension. The results illustrated low and fluctuating shear stress at outer and inner wall of aortic arch, proximal wall of branches, and entry region. Despite the simplification of aorta model, rigid walls and other assumptions results displayed that hypertension causes lowered local wall shear stresses. It is the sign of an increased risk of atherosclerosis. The assessment of hemodynamics shows that under the flow regimes of hypotension and hypertension, the risk of atherosclerosis localization in human aorta may increase.

Letter to the Editor Unexplained thrombosis of the aortic arch with distal embolization in a patient with altered fibrin clot properties

Letter to the Editor Unexplained thrombosis of the aortic arch with distal embolization in a patient with altered fibrin clot properties

3D Numerical Simulation for Reinforcement of Jijiata Tunnel, Liulin County, Shanxi Province

In this paper, the deformations and the stresses of surrounding rock of Jijiata tunnel, Liulin County, Shanxi Province, are all computed before reinforcement and after reinforcement, through the 3D numerical simulation. According to the computing result, before reinforcement, the computing result of the lateral displacements of the surrounding rock is consistent with the field measurement result. The maximum principle stress and the minimum principle stress are all less than the strength of the surrounding rock supporting, and this will not cause material damage so as to structural damage. But, since the tension stress is higher than the strength of the junction of tunnel arch and tunnel upright wall, this leads the larger deformation and the failure of the junction. After reinforcement, through the steel arch and the lock pin bolt’s enhanced role, the lateral displacement of the tunnel can be constrained effectively, the maximum principle stress and the minimum principle stress can be less than the strength of the surrounding rock supporting, and the tension stress can also be less than the strength of the junction. All the structures are all stable after reinforcement. Thus, this method should be selected as the proper method to reinforce the tunnel.

Arched Soil-Cement Walls for Soft Ground Reinforcement of Dike Slope

New structure of long straight walls with arched retaining wall was raised to improve the anti-sliding capacity of embankment soft ground. The arched walls embedded in the soft subsoil will transfer lateral forces in reasonable ways. Detailed research shows that the structure of arched walls can greatly increase slope stability and reliability.

Aortic intramural hematoma with dissection in aortic medial degeneration

A 67-year-old man presented to the hospital after acute onset of chest pain. Echocardiography showed a pericardial effusion and an aortic dissection was suspected. Contrast-enhanced computed tomographic angiography depicted aneurysmal dilation of the ascending aorta measuring 5.5 cm in diameter. Furthermore, it revealed an intimal tear with outflow of contrast medium into the dissected anterior wall of the upper ascending aorta (Panel A1; arrow). This tear extended into an anterior intramural hematoma, reaching from the aortic arch to the aortic root (Panel A2; arrow). Pericardial effusion was also present. The arch vessels were not involved. Catheter angiography ruled out coronary artery disease and confirmed that the coronary arteries were neither dissected nor compressed by the intramural hematoma. The imaging findings were confirmed intraoperatively, including the intimal tear of the aortic dissection. On visual inspection, the aortic valve and orifices of the coronary arteries were normal. The supracoronary ascending aorta and inferior wall of the aortic arch were replaced by a vascular prothesis. Histology of the resected aortic wall revealed a medial Images in vascular medicine

Evaluation of robotic endovascular catheters for arch vessel cannulation

Conventional catheter instability and embolization risk limits the adoption of endovascular therapy in patients with challenging arch anatomy. This study investigated whether arch vessel cannulation can be enhanced by a remotely steerable robotic catheter system. Seventeen clinicians with varying endovascular experience cannulated all arch vessels within two computed tomography-reconstructed pulsatile flow phantoms (bovine type I and type III aortic arches), under fluoroscopic guidance, using conventional and robotic techniques. Quantitative (catheterization times, catheter tip movements, vessel wall hits, catheter deflection) and qualitative metrics (Imperial College Complex Endovascular Cannulation Scoring Tool [IC3ST]) performance scores were compared. Robotic catheterization techniques resulted in a significant reduction in median carotid artery cannulation times and the median number of catheter tip movements for all vessels. Vessel wall contact with the aortic arch wall was reduced to a median of zero with robotic catheters. During stiff guidewire exchanges, robotic catheters maintained stability with zero deflection, independent of the distance the catheter was introduced into the carotid vessels. Overall IC3ST performance scores (interquartile range) were significantly improved using the robotic system: Type I arch score was 26/35 (20-30.8) vs 33/35 (31-34; P = .001), and type III arch score was 20.5/35 (16.5-28.5) vs 26.5/35 (23.5-28.8; P = .001). Low- and medium-volume interventionalists demonstrated an improvement in performance with robotic cannulation techniques. The high-volume intervention group did not show statistically significant improvement, but cannulation times, movements, and vessel wall hits were significantly reduced. Robotic technology has the potential to reduce the time, risk of embolization and catheter dislodgement, radiation exposure, and the manual skill required for carotid and arch vessel cannulation, while improving overall performance scores.

Thoracic aortic calcification measured by X-ray computed tomography vs age and risk factors of arteriosclerosis

The purpose of this study was to examine possible correlations among age, arteriosclerotic risk factors, and specific sites of calcification in the thoracic aorta as detected by X-ray computed tomography (CT). A total of 80 patients (mean age 59±9 years, 50 M/30 Fe) included 34 patients with ischemic heart disease, 32 with chest pain syndrome, 5 with valvular heart disease, and 9 with other diseases. The thoracic aortic calcification score, based on X-ray CT images, is the sum of the length (cm) of calcification detected in 1-cm-interval horizontal cross-sections. Differences in calcification were compared for patients with and without hypertension, diabetes, and hyperlipemia. Calcification occurred more often in the external left arch wall (52 cases), followed by the lower arch wall (50 cases). Calcification in the ascending aorta was detected in only 18 cases. Aortic calcification score ranged from 0 to 103.3 points with a mean of 8.8±14.9 points, showing a significant correlation (r=0.48,p<0.01) with patient age. However, there was no significant difference in ascending and descending aorta between sites of cross-sections. Calcification score was higher in patients with hypertension or diabetes. This difference, though significant, was very small. Moreover, patient age did have some correlation with calcification score, but the presence of ischemic heart disease and gender had no effect.

Pulsatile Flow Patterns and Wall Shear Stresses in Arch of a Turn-Around Tube With/Without Stenosis

ABSTRACTThe temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall shear stress of pulsatile water flows in the arch of 180o turn-around tubes with/without stenosis were experimentally studied by using the particle image velocimetry (PIV). Three transparent tubes made of glass were used: A tube without stenosis in the arch, a tube with a 25% stenosis at the inner wall of arch, and a tube with a 50% stenosis at the inner wall of arch. Here the percentage of stensis denoted the ratio between the stenosis height to inner diameter of arch in the diametral cross section across mid-arch of the central plane. The flow was provided by a pump which approximately simulated the pulsatile pressure waves of human heart beats. The systole to diastole time period ratio is set at 35%:65%. The Womersley parameter, Dean number, and time-averaged Reynolds number were 14, 2348, and 3500, respectively. In the arch of the turn-around tube without stenosis, no boundary layer separation was found during the systolic phase. The reverse flow and recirculation bubble appeared in the arch only during the diastolic phase. The inner wall of the arch experienced lower wall shear stress during the diastolic phase due to the formation of recirculation bubble and secondary flow. In the arch with stenosis, the boundary layer separated from the inner wall and formed a recirculation bubble downstream the stenosis during the systolic phase. Lower stenosis (25%) did not cause drastic variation of the wall shear stresses. At higher stenosis (50%), however, the wall shear stress around the inner wall downstream the stenosis became extraordinarily low, whereas the wall shear stress around the upstream region of the outer wall of the downstream branch of the tube became anomalously large.

Pollen and Seed Morphology of Tribulus Terrestris L. (Zygophyllaceae)

ABSTRACTLight microscope (LM) and Scanning electron microscope (SEM) study of the pollen and seed morphology of Tribulus terrestris (Zygophyllaceae), especially in the native Bulgarian population from Thracian Lowland, was carried out. It was established that the pollen grains are oblate-spheroidal, radially symmetric, pantoporate. Exine ornamentation is reticulate. The seeds of Tribulus terrestris are flat, triangular-ovate. The seed sculpture corresponds to the Tubular-type, which is characterized with polygonal cells and straight arched anticlinal walls, whereas the periclinal ones are wavy with dense cuticular wax folds.

Analysis of early embryonic great-vessel microcirculation in zebrafish using high-speed confocal μPIV

In the developing cardiovascular system, hemodynamic vascular loading is critical for angiogenesis and cardiovascular adaptation. Normal zebrafish embryos with transgenically-labeled endothelial and red blood cells provide an excellent in vivo model for studying the fluid-flow induced vascular loading. To characterize the developmental hemodynamics of early embryonic great-vessel microcirculation in the zebrafish embryo, two complementary studies (experimental and numerical) are presented. Quantitative comparison of the wall shear stress (WSS) at the first aortic arch (AA1) of wild-type zebrafish embryos during two consecutive developmental stages is presented, using time-resolved confocal micro-particle image velocimetry (μPIV). Analysis showed that there was significant WSS difference between 32 and 48 h post-fertilization (hpf) wild-type embryos, which correlates with normal arch morphogenesis. The vascular distensibility of the arch wall at systole and the acceleration/deceleration rates of time-lapse phase-averaged streamwise blood flow curves were also analyzed. To estimate the influence of a novel intermittent red-blood cell (RBC) loading on the endothelium, a numerical two-phase, volume of fluid (VOF) flow model was further developed with realistic in vivo conditions. These studies showed that near-wall effects and cell clustering increased WSS augmentation at a minimum of 15% when the distance of RBC from arch vessel wall was less than 3 μm or when RBC cell-to-cell distance was less than 3 μm. When compared to a smooth wall, the WSS augmentation increased by a factor of ~1.4 due to the roughness of the wall created by the endothelial cell profile. These results quantitatively highlight the contribution of individual RBC flow patterns on endothelial WSS in great-vessel microcirculation and will benefit the quantitative understanding of mechanotransduction in embryonic great vessel biology, including arteriovenous malformations (AVM).

Enhanced inhibition of murine prostatic carcinoma growth by immunization with or administration of viable human umbilical vein endothelial cells and CRM197

Vaccination with xenogeneic and syngeneic endothelial cells is effective for inhibiting tumor growth. Nontoxic diphtheria toxin (CRM197), as an immunogen or as a specific inhibitor of heparin-binding EGF-like growth factor, has shown promising antitumor activity. Therefore, immunization with or administration of viable human umbilical vein endothelial cells (HUVECs) combined with CRM197 could have an enhanced antitumor effect. Six-week-old C57BL/6J male mice were vaccinated with viable HUVECs, 1 x 10(6) viable HUVECs combined with 100 μg CRM197, or 100 μg CRM197 alone by ip injections once a week for 4 consecutive weeks. RM-1 cells (5 x 10(5)) were inoculated by sc injection as a preventive procedure. During the therapeutic procedure, 6-week-old male C57BL/6J mice were challenged with 1 x 10(5) RM-1 cells, then injected sc with 1 x 10(6) viable HUVECs, 1 x 10(6) viable HUVECs + 100 μg CRM197, and 100 μg CRM197 alone twice a week for 4 consecutive weeks. Tumor volume and life span were monitored. We also investigated the effects of immunization with HUVECs on the aortic arch wall and on wound healing. Vaccination with or administration of viable HUVECs+CRM197 enhanced the inhibition of RM-1 prostatic carcinoma by 24 and 29%, respectively, and prolonged the life span for 3 and 4 days, respectively, compared with those of only vaccination or administration with viable HUVECs of tumor-bearing C57BL/6J mice. Furthermore, HUVEC immunization caused some damage to the aortic arch wall but did not have remarkable effects on the rate of wound healing; the wounds healed in approximately 13 days. Treatment with CRM197 in combination with viable HUVECs resulted in a marked enhancement of the antitumor effect in the preventive or therapeutic treatment for prostatic carcinoma in vivo, suggesting a novel combination for anti-cancer therapy.

Response of Arching Unreinforced Concrete Masonry Walls to Blast Loading

New standards for blast protection of buildings are currently being developed in the United States and Canada. In this regard, both standards are considering unreinforced masonry (URM) walls as particularly vulnerable to blast events and may not be used in blast-resisting structural systems. In this paper, the effectiveness of enforcing arching action as a cost-effective hardening technique for vertically spanning one-way URM walls under blast loads is investigated. A total of eight full-scale concrete-block URM walls were subjected to blast loads generated by high explosives. Enforcing URM walls arching between rigid supports significantly enhanced their out-of-plane blast resistance compared to similar nonarching (flexural) URM walls. Moreover, no fragments or debris were observed on the leeward side of the arching walls, indicating the potential of the proposed hardening technique in reducing the hazard level on the occupants of buildings with exterior URM walls. The improved performance is attributed to the formation of hinges at the walls’ supports and midheights. This three-hinged arch mechanism allowed the walls to develop large in-plane compressive forces, which subsequently increased their out-of-plane resistances and prevented flying debris due to increased friction forces between the masonry courses. Comparing the observed strength of the arched walls to their strength predicted by existing models showed a significant underestimation of the actual wall strengths. The results of the study clearly demonstrate that, with minimal structural intervention, URM walls can significantly improve the building envelope performance and contribute to the structural resistance of blast loads.

Otolith and vertebral morphology of marine atherinid species (Atheriniformes, Atherinopsidae) coexisting in the southwestern Atlantic Ocean

Studies on marine ecosystems rely on the identification of fish prey species of piscivores (fish, aquatic mammals, and aquatic birds) based on their bones and otoliths. The stomach contents of piscivores show predation on marine atherinids of commercial value; however, their identification is difficult due to the coexistence of these species. The objective of the present study is to propose the use of hard structures (otolith, caudal vertebrae) as a tool for the identification of marine atherinid fishes occurring in the southwestern Atlantic Ocean. Sagittae (200 pairs) were removed from the otic capsules for further examination and measurement. The vertebral column of individuals from each species was also removed for examination. The morphological pattern of the sagitta otoliths of five marine species belonging to the genus Odontesthes was consistent with that of the subfamily Atherinopsinae, with these patterns being species specific. In Odontesthes argentinensis, O. platensis, and O. smitti, the caudal vertebrae present an expansion of the haemal arch walls forming a haemal funnel with distinctive morphology, while this characteristic is absent in O. incisa and O. nigricans. The hard structures used in this study proved to be a useful tool for the correct identification of the atherinids found in the diet of piscivorous species from the southwestern Atlantic Ocean. A key based on the major morphological features of sagittae and hemal arches is provided.

Carotid Denervation by Adventitial Stripping: A Promising Treatment of Carotid Sinus Syndrome?

The baroreflex is an important component of the physiological short-term control of the blood pressure. Baroreceptors are mainly located in the wall of the aortic arch and of the internal carotid artery (ICA). The carotid sinus nerve (CSN) contains afferent fibres travelling from the carotid sinus’ baroreceptors located in the adventitia of the ICA. It joins the glossopharyngeal (IX) nerve and ends in the nucleus tractus solitarius in the brain stem. The efferent loop is conducted by the vagus (X) nerve to the heart leading to a physiologic bradycardia and inhibited atrioventricular conduction, in response to systemic hypertension. Also, a blocked sympathetic nerve system causes venodilatation, decreasing ventricular preload, and vasodilatation, both leading to decreased blood pressure. Carotid sinus syndrome (CSS) is caused by a pathologic overshoot of this baroreflex and is characterised by exaggerated bradycardia and hypotension in response to carotid sinus stimulation, in situations such as shaving, wearing tight collar or head turning. The triggering events might vary considerably overtime in any individual patient, but the syndrome can be reproduced by carotid sinus massage. CSS prevalence could be as high as 45% in elderly patients. If left untreated, CSS mortality rates could exceed 25% within 5 years.