Stenotic Plaque Research Articles

WALL SHEAR STRESS AND OSCILLATORY SHEAR INDEX DISTRIBUTION IN CAROTID ARTERY WITH VARYING DEGREE OF STENOSIS: A HEMODYNAMIC STUDY

A significant proportion of cerebral stroke is a consequence of the arterial stenotic plaque rupture causing local thrombosis or distal embolization. The formation and subsequent rupture of the plaque depends on wall shear stress (WSS) and oscillatory shear index (OSI). The purpose of the present study was to understand the effect of hemodynamics on the spatial and temporal variations of WSS and OSI using realistic models with varying degree of carotid artery stenosis (DOS). Multiple CT volumes were obtained from subjects in the carotid bifurcation zone and the 3D models were generated. A finite volume-based computational fluid dynamics (CFD) method was utilized to understand the hemodynamics in pulsatile flow conditions. It was observed that high stenosis models occupied a large value of normalized WSS in the internal carotid artery (ICA) whereas they had smaller values of normalized WSS in the common carotid artery (CCA). For clinical use, the authors recommend using the spatial average value of oscillatory shear rather than the maximum value for an accurate knowledge about the severity of stenosis. The resultant vorticity changes the direction of spin after the bifurcation zone. Additionally, we propose the use of limiting streamlines as a novel and convenient method to identify the disturbed flow regions that are prone to atherogenesis.

Contrast-enhanced ultrasound of the carotid system: a review of the current literature.

Carotid disease is a major current health problem accounting for a significant part of stroke patients. Ultrasound with colour Doppler and spectral analysis is the primary imaging technique used for screening and diagnostic evaluation of the extracranial part of carotid arteries offering identification and grading of carotid disease. However, inherent limitations of this technique include flow-related artefacts like Doppler angle dependence and aliasing artefact which may sometimes hinder complete assessment of a stenotic part of the vessel, potentially failing to address clinically significant differential diagnosis issues. The intravenous use of microbubbles as an US contrast agent has been introduced for the supplementation of conventional technique. The value of contrast-enhanced ultrasound (CEUS) has been investigated in the evaluation of carotid disease leading to promising results. CEUS provides improved flow visualization free of artefacts and detailed plaque surface delineation, thus being able to accurately grade stenosis, identify carotid plaque ulcerations, differentiate occlusion from highly stenotic plaques and identify carotid dissection. Furthermore, microbubbles can be used to identify and grade intraplaque neovascularization, carotid wall inflammation in patients with arteritis, follow-up patients after carotid intervention and assist interventional procedures reducing the need for nephrotoxic contrast agents. The purpose of this review is to present and discuss the current literature regarding the various uses of CEUS in carotid arteries.

A global mathematical model for the simulation of stenoses and bypass placement in the human arterial system

This paper is concerned with a global mathematical model for the human circulation; we describe its construction, its validation and its application to study the haemodynamical effect of stenoses and bypass placement in the arterial system. A geometric multiscale approach is adopted combining one-dimensional (1D) descriptions to represent 55 major arteries and zero-dimensional (0D) compartmental descriptions for the heart, lungs, the venous system and the microcirculation. Modern non-linear numerical methods are implemented for solving the 1D systems of hyperbolic partial differential equations and high-order Runge–Kutta methods are used to solve the systems of Ordinary Differential Equations resulting from the compartmental models. The complete global mathematical model is then validated for healthy and stenotic cases comparing numerical predictions from the model against in-vivo measurements. Results show overall satisfactory agreement. In addition, a sensitivity analysis is conducted in order to assess the influence of the most important parameters on some haemodynamical quantities of interest. We then apply the model to simulate the haemodynamics for healthy controls and subjects with arterial stenosis. We study the haemodynamical effect of bypass placement, considering different locations in the arterial system, different degrees of severity, for both single and multiple arterial stenoses. Haemodynamical quantities of interest in the study are local pressure and flow rate. We observe that large stenotic plaques near the heart cause abnormally strong pressure waves in the circulatory system and two adjacent occlusions worsen the phenomenon. We find that the mathematical model is capable of predicting the most convenient bypass location and graft dimensions, consistent with normal haemodynamics.

P.098 Arterial wall and plaque remodeling after stent deployment in carotid stenosis: ultrasonographic study

Background: We evaluated the effects of stents on carotid plaque and the arterial wall using carotid ultrasound in carotid stenting patients Methods: From a carotid stent database, 30 consecutive patients were selected. All had Doppler ultrasound performed pre and post-stenting. The diameters of the lumen at the level of stenotic plaque pre and post stenting, the dorsal and ventral plaque thickness, and of the outer arterial wall diameter were measured. Plaque thickness was measured at the level of maximal stenosis.Non parametric tests were used to determine whether the stent effect and luminal enlargement were based on wall remodeling or on total arterial expansion. Results: Patient was followed for an average of 22 months. 18 patients were male, average age 70 years. 87% were symptomatic ipsilateral to the side of stenosis. The luminal diameter increased post stenting in the region of severe stenosis. Plaque thickness, both ventrally, as well as dorsally decreased post stenting, with no significant difference between the ventral and dorsal plaque effects. The measured lumen in the stent increased over time post-stenting. Conclusions: Self-expanding nitinol stents alter the baseline ventral and dorsal plaque to a significant degree, and do not significantly affect the native arterial wall and the overall arterial diameter.

Mechanical behavior of peripheral stents and stent-vessel interaction: A computational study

ABSTRACTIn this paper stents employed to treat peripheral artery disease are analyzed through a three-dimensional finite-element approach, based on a large-strain and large-displacement formulation. Aiming to evaluate the influence of some stent design parameters on stent mechanics and on the biomechanical interaction between stent and arterial wall, quasi-static and dynamic numerical analyses are carried out by referring to computational models of commercially and noncommercially available versions of both braided self-expandable stents and balloon-expandable stents. Addressing isolated device models, opening mechanisms and flexibility of both opened and closed stent configurations are numerically experienced. Moreover, stent deployment into a stenotic peripheral artery and possible postdilatation angioplasty (the latter for the self-expandable device only) are simulated by considering different idealized vessel geometries and accounting for the presence of a stenotic plaque. Proposed results highlight important differences in the mechanical response of the two types of stents, as well as a significant influence of the vessel shape on the stress distributions arising upon the artery-plaque system. Finally, computational results are used to assess both the stent mechanical performance and the effectiveness of the stenting treatment, allowing also to identify possible critical conditions affecting the risk of stent fracture, tissue damage, and/or pathological tissue response.

Best-Quality Vessel Identification Using Vessel Quality Measure in Multiple-Phase Coronary CT Angiography

The detection of stenotic plaques strongly depends on the quality of the coronary arterial tree imaged with coronary CT angiography (cCTA). However, it is time consuming for the radiologist to select the best-quality vessels from the multiple-phase cCTA for interpretation in clinical practice. We are developing an automated method for selection of the best-quality vessels from coronary arterial trees in multiple-phase cCTA to facilitate radiologist's reading or computerized analysis. Our automated method consists of vessel segmentation, vessel registration, corresponding vessel branch matching, vessel quality measure (VQM) estimation, and automatic selection of best branches based on VQM. For every branch, the VQM was calculated as the average radial gradient. An observer preference study was conducted to visually compare the quality of the selected vessels. 167 corresponding branch pairs were evaluated by two radiologists. The agreement between the first radiologist and the automated selection was 76% with kappa of 0.49. The agreement between the second radiologist and the automated selection was also 76% with kappa of 0.45. The agreement between the two radiologists was 81% with kappa of 0.57. The observer preference study demonstrated the feasibility of the proposed automated method for the selection of the best-quality vessels from multiple cCTA phases.

Arterial Stiffness Index and Coronary Artery Plaques in Patients with Subclinical Coronary Atherosclerosis.

Arterial stiffness is a physiologic quantitative value used to measure arterial compliance. It is predictive of coronary atherosclerosis in patients with intermediate to high cardiovascular risk. However, a correlation between arterial stiffness and subclinical coronary atherosclerosis has yet to be established. Therefore, the purpose of this study was to evaluate arterial stiffness using an arterial stiffness index (ASI) and investigate its association with coronary artery plaque in patients with subclinical coronary atherosclerosis. Our study enrolled 156 consecutive subjects who underwent health screening using a 64-slice cardiac computed tomography angiography (CCTA). Their arterial stiffness index was assessed noninvasively by CardioVision(®) MS-2000. The atheroma on the coronary vessel walls was analyzed. Of the 156 patients, 53 displayed at least one > 50% stenotic lesion over the coronary arteries in CCTA images. The patients with at least one > 50% coronary stenotic plaque were older and had higher systolic blood pressure and ASI values than patients without > 50% coronary stenotic plaque. After dividing the study population into 2 groups by those patients over and under 50 years of age, the ASI positively correlated with the presentation of at least one > 50% coronary stenotic plaque in patients aged ≥ 50 years (odds ratio = 1.02, 95% confidence interval: 1.00-1.04, p = 0.03). The ASI could play a role in risk stratification systems for coronary artery disease in patients with subclinical coronary atherosclerosis, and is a useful clinical marker for the correlation of early coronary plaque. Arterial stiffness; Arterial stiffness index; Atherosclerosis; Coronary artery plaque.

Use of high-resolution 3.0-T magnetic resonance imaging to characterize atherosclerotic plaques in patients with cerebral infarction.

The present study aimed to evaluate the utility of high-resolution magnetic resonance imaging (MRI) in the characterization of atherosclerotic plaques in patients with acute and non-acute cerebral infarction. High-resolution MRI of unilateral stenotic middle cerebral arteries was performed to evaluate the degree of stenosis, the wall and plaque areas, plaque enhancement patterns and lumen remodeling features in 15 and 17 patients with acute and non-acute cerebral infarction, respectively. No significant difference was identified in the vascular stenosis rate between acute and non-acute patients. Overall, plaque eccentricity was observed in 29 patients, including 13 acute and 16 non-acute cases, with no significant difference identified between these groups. The wall area of stenotic arteries and the number of cases with plaque enhancement were significantly greater in the acute patients, but no significant difference in plaque or lumen area was identified between the 2 patient groups. Lumen remodeling patterns of stenotic arteries significantly differed between the acute and non-acute patients; the former predominantly demonstrated positive remodeling, and the latter group demonstrated evidence of negative remodeling. In conclusion, patients with acute and non-acute cerebral infarction exhibit specific characteristics in stenotic arteries and plaques, which can be effectively evaluated by high-resolution MRI.

Accumulation of Ca+ 2 at arterial segments proximal to myocardial bridging may influence the vascular dynamics of coronary artery

We have read the arguments about the undetermined mechanisms of ischemia induced by myocardial bridge (MB) [ 1 Peters S. Unusual case of myocardial bridging of the circumflex artery and initially intractable chest pain. Int. J. Cardiol. 2015; 179: 25-26 Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar , 2 Duygu H. Myocardial bridging of the left circumflex artery: an extremely rare entity Int. J. Cardiol. 2015; 189: 231 Scopus (3) Google Scholar , 3 Gili S. Taha S. Omede P. Moretti C. A bridge over troubled water: functional assessment of a myocardial bridge. Int. J. Cardiol. 2015; 201: 285-287 Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar ]. Gili et al. claimed that the strategies to evaluate the ischemia induced by MB failed due to complex dynamics of coronary flow [ [3] Gili S. Taha S. Omede P. Moretti C. A bridge over troubled water: functional assessment of a myocardial bridge. Int. J. Cardiol. 2015; 201: 285-287 Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar ]. However this dilemma could have been explained by a recent finding. We read that article in which Tohno et al. reported the elevation of Ca, P, Zn, and Na levels in the arterial segments proximal to MB on the LAD artery [ [4] Tohno Y. Tohno S. Minami T. Pakdeewong-Ongkana N. Suwannahoy P. Quiggins R. Different accumulation of elements in proximal and distal parts of the left anterior descending artery beneath the myocardial bridge. Biol. Trace Elem. Res. 2015; https://doi.org/10.1007/s12011-015-0498-x Crossref PubMed Scopus (3) Google Scholar ]. They also reported that defective areas of endothelial lining were observed in those segments. Those findings may explain how those patients are suffering from recurrent chest pain, MI, and ACS even at relatively young ages despite normal angiogram with mild narrowing due to MB or non-critically stenotic plaque accompanied with MB. In our experience, we observed that those young subjects were generally misdiagnosed as myocarditis although they had presented with ST segment elevation on precordial ECG leads and then we diagnosed them as having long segment MB on LAD artery by multidetector computerized tomography angiography [ [5] Aparci M. Ozturk C. Okutucu S. Balta S. Isilak Z. Kardesoglu E. Bozlar U. Anteroseptal myocardial infarctions due to myocardial bridging are generally misdiagnosed as myocarditis in young patients. Am. J. Cardiol. 2015; (Suppl., PP-031): S110-S111 Abstract Full Text Full Text PDF Google Scholar ]. Additionally, case reports and studies presenting the coronary vasospasm associated with MB have been increasing [ 6 Vales L. Kanie Y. Fox J. Coronary artery occlusion and myocardial infarction caused by vasospasm within a myocardial bridge. J. Invasive Cardiol. 2010; 22: E67-E69 PubMed Google Scholar , 7 Teragawa H. Fukuda Y. Matsuda K. Hirao H. Higashi Y. Yamagata T. Oshima T. Matsuura H. Chayama K. Myocardial bridging increases the risk of coronary spasm. Clin. Cardiol. 2003; 26: 377-383 Crossref PubMed Scopus (58) Google Scholar ]. Moreover those patients with MB and coronary vasospasm had poor prognosis due to recurrent chest pain, MI, and life threatening arrhythmia [ [8] Kim S.S. Jeong M.H. Kim H.K. Kim M.C. Cho K.H. Lee M.G. Ko J.S. Park K.H. Sim D.S. Yoon N.S. Yoon H.J. Park H.W. Kim J.H. Hong Y.J. Ahn Y.K. Cho J.G. Park J.C. Kang J.C. Long-term clinical course of patients with isolated myocardial bridge. Circ. J. 2010; 74: 538-543 Crossref PubMed Scopus (23) Google Scholar ].

Sindromul Kounis – o etiologie alternativă a infarctului miocardic acut

Kounis syndrome is defined as an association between an acute coronary syndrome and acute systemic allergy involving vasoactive mediators released during the activation of the mast cells. A 79 year old woman arrives at the emergency department with syncope; she was stung by a wasp an hour before symptoms’ onset. Clinical examination was normal, excepet her left upper limb which had important edema. The ECG revealed ST-segment elevation in the inferior leads and negative T waves in the anterior leads. Emergency coronary angiography was performed, which revealed a 40% stenotic plaque on the mid LAD. A conservative approach was decided. The patient received standard anti-ischemic treatment and she was safely discharged after 6 days. We considered this case a Kounis syndrome induced by a wasp sting associated with a silent inferior myocardial infarction.

MicroRNA deregulation in symptomatic carotid plaque

Embolization of carotid stenotic plaques is the direct cause of stroke in nearly 20% of cases. Genetic mechanisms and especially the roles played by microRNAs in the regulation of plaque destabilization and rupture are mostly unknown. The aim of this pilot study was to compare the expression of seven microRNAs allegedly involved in plaque growth and instability (miR-100, 125a, 127, 133a, 145, 155, and 221), between symptomatic and asymptomatic human carotid plaques. Thirty patients undergoing carotid endarterectomy in our department were prospectively included. Carotid plaques were subdivided into symptomatic (n= 15) and asymptomatic (n= 15) according to the presence or absence of stroke. After isolation of total RNA from atherosclerotic plaques, microRNAs were quantified by real-time polymerase chain reaction. The two groups of patients were comparable in terms of age, gender, risk factors for cerebral ischemia, medication, and stenosis severity. All seven microRNAs were quantified in extracted carotid plaques. miR-100, miR-125a, miR-127, miR-133a, miR-145, and miR-221 were significantly overexpressed in symptomatic vs asymptomatic plaques. miR-125a expression was significantly inversely correlated with the circulating level of low-density lipoprotein cholesterol in the symptomatic group. This pilot study evaluated the expression of seven selected miRNAs in human carotid plaques from a small group of patients and suggested a potential regulatory role for these miRNAs in evolution of the plaque towards growth, instability and rupture. Studies based on larger sample sizes are required to determine the potential use of miR-100, miR-125a, miR-127, miR-133a, miR-145, and miR-221 as biomarkers or therapeutic targets for stroke.

Do plaques rapidly progress prior to myocardial infarction? The interplay between plaque vulnerability and progression.

There is a common misperception in the cardiology community that most acute coronary events arise from ruptures of mildly stenotic plaques. This notion has emanated from multiple studies that had measured the degree of angiographic luminal narrowing in culprit plaques months to years before myocardial infarction. However, angiographic studies within 3 months before myocardial infarction, immediately after myocardial infarction with thrombus aspiration or fibrinolytic therapy, and postmortem pathological observations have all shown that culprit plaques in acute myocardial infarction are severely stenotic. Serial angiographic studies also have demonstrated a sudden rapid lesion progression before most cases of acute coronary syndromes. The possible mechanisms for such rapid plaque progression and consequent luminal obstruction include recurrent plaque rupture and healing and intraplaque neovascularization and hemorrhage with deposition of erythrocyte-derived free cholesterol. Moreover, recent intravascular and noninvasive imaging studies have demonstrated that plaques which result in coronary events have larger plaque volume and necrotic core size with greater positive vessel remodeling compared with plaques, which remain asymptomatic during several years follow-up, although these large atheromatous vulnerable plaques may angiographically seem mild. As such, it is these vulnerable plaques which are more prone to rapid plaque progression or are those in which plaque progression is more likely to become clinically evident. Therefore, in addition to characterizing plaque morphology, inflammatory activity, and severity, detection of the rate of plaque progression might identify vulnerable plaques with an increased potential for adverse outcomes.

CAROTID DOPPLER PROFILE IN PATIENT WITH HYPERTENSIVE RETINOPATHY

Background: Retinal vasculature is a unique part of the brain that visualized, which can show microvascular abnormality related to atherosclerosis process. Hypertension can caused vascular sclerosis either in large vessels of carotid or retinal microvasculature which showed in fundoscopic examination. Objective: This study aims to obtain the carotid abnormality with Carotid Doppler ultrasonography in hypertensive retinopathy patients and its contributing factors. Methods: This was a cross-sectional retrospective study using consecutive sampling from Neuro-Ophthalmology Division of Neurology Clinic of Cipto Mangunkusumo Hospital in January to December 2014. All patients, aged 40–80 years old with hypertensive retinopathy and had done Carotid Doppler examination. Hypertensive retinopathy graded according to Wong & Mitchell Classification. Statistical analysis was done using SPSS 15.0 for windows. Results: There were 35 subjects, men slightly more than women with both age mean is 60.5 ± 11.8 years old. Hypertension duration known mostly 10 years or bellow in 27 subjects (77.1%) and uncontrolled blood pressure in 28 subjects (80%). There were 25 subjects (71.4%) with carotid abnormality, mostly non stenotic plaque (54,3%). Mild hypertensive retinopathy occured in 32 subjects (81,4%) and the rest of it were moderate (3 subjects, 8.6%). Conclusion: Fundoscopic abnormality assumed may predict large vessels abnormality, hypertensive retinopathy in this study. This study suggested advanced, more-focused study, larger sample, and analytical method to obtain the correlation between retinal microvasculature and large vessels abnormality, especially carotid artery.

A study of balloon type, system constraint and artery constitutive model used in finite element simulation of stent deployment

Abstract Background Finite element is an effective tool to simulate stent expansion inside stenotic arteries, which provides an insightful understanding of the biomechanical behaviour of the whole stent-artery system during the procedure. The choice of balloon type, system constraint and artery constitutive model plays an important role in finite element simulation of stent deployment. Methods Commercial finite element package ABAQUS was used to model the expansion of Xience stent inside a diseased artery with 40% stenosis. The arterial wall, consisting of intima, media and adventitia layers, and the stenotic plaque were described by different hyperelastic models. Both folded and rubber balloons were considered and inflated with a linearly increasing pressure of 1.4 MPa. Simulations were also carried out by considering free, partially and fully constrained arteries. Results Folded balloon produces sustained stent expansion under a lower pressure when compared to rubber balloon, leading to increased stress level and enhanced final expansion for the system. Fully constrained artery reduces the stent expansion when compared to free and partially constrained arteries, due to the increased recoiling effect. Stress in the artery-plaque system has higher magnitude for stent expansion in a free artery due to more severe stretch. Calcified plaque limits stent expansion considerably when compared to hypocellular plaque. The negligence of the second stretch invariant in the strain energy potential leads to the disappearance of saturation behaviour during stent expansion. The use of anisotropic artery model reduces the system expansion at peak pressure when compared to the isotropic model, but with an increased final diameter due to reduced recoiling effect. The stress distribution in the artery-plaque system is also different for different combinations of artery and plaque constitutive models. Conclusions Folded balloon should be used in the simulation of stent deployment, with the artery partially constrained using spring elements with a proper stiffness constant. The blood vessel should be modelled as a three-layer structure using a hyperelastic potential that considers both the first and second stretch invariants as well as the anisotropy. The composition of the plaque also has to be considered due to its major effect on stent deployment.

Impaired gait pattern as a sensitive tool to assess hypoxic brain damage in a novel mouse model of atherosclerotic plaque rupture

Apolipoprotein E deficient (ApoE−/−) mice with a heterozygous mutation in the fibrillin-1 gene (Fbn1C1039G+/−) show spontaneous atherosclerotic plaque ruptures, disturbances in cerebral flow and sudden death when fed a Western-type diet (WD). The present study focused on motor coordination and spatial learning of ApoE−/− Fbn1C1039G+/− mice on WD for 20weeks (n=21). ApoE−/− mice on WD (n=24) and ApoE−/− Fbn1C1039G+/− mice on normal diet (ND, n=21) served as controls. Starting from 10weeks of diet, coordination was assessed every two weeks by the following tests: gait analysis, stationary beam, wire suspension and accelerating rotarod. The Morris water maze test was performed after 13weeks of diet to study spatial learning. At the end of the experiment (20weeks of WD), the mice were sacrificed and the brachiocephalic artery and brain were isolated. From 12weeks onward, gait analysis of ApoE−/− Fbn1C1039G+/− mice on WD revealed a progressive increase in track width as compared to ApoE−/− mice on WD and ApoE−/− Fbn1C1039G+/− mice on ND (at 20weeks: 29.8±0.6mm vs. 25.8±0.4mm and 26.0±0.5mm). Moreover, the stationary beam test showed a decrease in motor coordination of ApoE−/− Fbn1C1039G+/− mice on WD at 18 and 20weeks. The wire suspension test and accelerating rotarod could not detect signs of motor impairment. Spatial learning was also not affected. Histological analysis of the brachiocephalic artery showed larger and more stenotic plaques in ApoE−/− Fbn1C1039G+/− mice on WD. Furthermore, the parietal cortex of ApoE−/− Fbn1C1039G+/− mice on WD showed pyknotic nuclei as a sign of hypoxia and the percentage of pyknosis correlated with track width. In conclusion, gait analysis may be an efficient method for analyzing hypoxic brain damage in the ApoE−/− Fbn1C1039G+/− mouse model. This test could be of value to assess the effect of potential anti-atherosclerotic therapies in mice.

Fatigue Life Assessment of Self-Expandable NiTi Stent

Objectives: This paper presents a numerical fatigue life assessment of a self-expandable Nitinol stent. The analysis was performed using the ANSYS 11 software. Methods: Stent durability is an issue which must be addressed during the design of implants. Given the corrosive properties of blood and the cyclic loads that are applied on the stent (the cyclic variation of blood pressure), the determination of fracture parameters and fatigue characteristics of the implant is highly recommended. Breaking of the stent’s wire is particularly dangerous because it can cause the dislocation of a piece of stenotic plaque, which in turn can block a smaller artery, causing a heart attack. On the other hand, any discontinuity in stent structure acts as an accumulating place for stenosis particles, significantly shortening the life of the implant. The stent consists of a cylindrical tube 22.42 mm long, with a diameter of 8.3 millimeters. The wire section is square, 0.2x0.2 millimeters. The stent is only subjected to the pressure generated by the stenoted arterial wall. This evenly distributed pressure is defined at the outer surface of the stent and has a value of 2.5 MPa, corresponding to a 56% blood vessel stenosis. This way, the most severe loading conditions for the stent could be simulated. The stress distribution was then used to asses the fatigue life of the stent. Results and conclusions: The results showed that, in normal conditions (with the maximal internal pressure of 139 mm Hg = 18533 Pa), no damage appears on the stent after 107 cycles.

Coronary CT angiography (cCTA): automated registration of coronary arterial trees from multiple phases

Coronary computed tomography angiography (cCTA) is a commonly used imaging modality for the evaluation of coronary artery disease. cCTA is generally reconstructed in multiple cardiac phases because different coronary arteries may be better visualized in some phases than in others due to the periodic cardiac motion. We are developing an automated registration method for coronary arterial trees from multiple-phase cCTA that has potential application in building a ‘best-quality’ tree to facilitate image analysis and detection of stenotic plaques. Given the segmented left or right coronary arterial (LCA or RCA) trees from the multiple phases as input, the adjacent phase pairs, where displacements are relatively small, are registered by a specifically designed method based on a cubic B-spline with fast localized optimization (CBSO). For the phase pairs with large displacements, a global registration using an affine transform with quadratic terms and nonlinear simplex optimization (AQSO) is followed by a local registration using CBSO to refine the AQSO registered volumes. 26 LCA and 26 RCA trees with six cCTA phases from 26 patients were used for registration evaluation. The average distances for the tree pairs between the adjacent phases with small displacements before and after CBSO registration were 0.96 ± 0.79 and 0.76 ± 0.61 mm respectively for LCA, and 0.93 ± 0.97 and 0.64 ± 0.43 mm, respectively for RCA. The average distance differences before and after registration were statistically significant (p < 0.001) for both LCA and RCA trees. The average distances for the distant phases with large displacements before registration, after AQSO registration, and finally after the CBSO registration were 2.85 ± 1.46, 1.62 ± 0.76, and 0.97 ± 0.43 mm, respectively for LCA, and 4.03 ± 2.36, 2.18 ± 1.11, and 0.97 ± 0.44 mm, respectively for RCA. The average distance differences between every two consecutive stages of registration were statistically significant. The corresponding phases of LCA and RCA trees were aligned to an average of less than 1 mm, providing a basis for a best-quality tree construction.

In vitro shear stress measurements using particle image velocimetry in a family of carotid artery models: effect of stenosis severity, plaque eccentricity, and ulceration.

Atherosclerotic disease, and the subsequent complications of thrombosis and plaque rupture, has been associated with local shear stress. In the diseased carotid artery, local variations in shear stress are induced by various geometrical features of the stenotic plaque. Greater stenosis severity, plaque eccentricity (symmetry) and plaque ulceration have been associated with increased risk of cerebrovascular events based on clinical trial studies. Using particle image velocimetry, the levels and patterns of shear stress (derived from both laminar and turbulent phases) were studied for a family of eight matched-geometry models incorporating independently varied plaque features – i.e. stenosis severity up to 70%, one of two forms of plaque eccentricity, and the presence of plaque ulceration). The level of laminar (ensemble-averaged) shear stress increased with increasing stenosis severity resulting in 2–16 Pa for free shear stress (FSS) and approximately double (4–36 Pa) for wall shear stress (WSS). Independent of stenosis severity, marked differences were found in the distribution and extent of shear stress between the concentric and eccentric plaque formations. The maximum WSS, found at the apex of the stenosis, decayed significantly steeper along the outer wall of an eccentric model compared to the concentric counterpart, with a 70% eccentric stenosis having 249% steeper decay coinciding with the large outer-wall recirculation zone. The presence of ulceration (in a 50% eccentric plaque) resulted in both elevated FSS and WSS levels that were sustained longer (∼20 ms) through the systolic phase compared to the non-ulcerated counterpart model, among other notable differences. Reynolds (turbulent) shear stress, elevated around the point of distal jet detachment, became prominent during the systolic deceleration phase and was widely distributed over the large recirculation zone in the eccentric stenoses.

Abstract 267: Histomorphometric Evaluation of Estrogen Effects on Coronary Artery Atherosclerosis: Inhibition of Plaque Formation, Reduction in Plaque Size and Promotion of Positive Remodeling Independent of Plaque Complications

Introduction: Whether and to what extent postmenopausal estrogen therapy has beneficial effects on progression of coronary artery atherosclerosis is controversial. In previous studies with monkey models we have shown that the stage of plaque progression modulates estrogen benefits and have led to the “timing hypothesis”. In this study, we used a histomorphometric approach to understand better the effects of estrogen therapy on critical components of atherosclerosis pathogenesis. Our hypothesis was that estrogen therapy would inhibit the initial development of atherosclerotic plaques, result in smaller but not less complicated plaques and among subjects that developed plaques, it would promote positive arterial remodeling. Methods: Forty-eight surgically postmenopausal monkeys (Macaca fascicularis) were fed a moderately atherogenic diet and randomly assigned to receive no treatment (CTL) or a women’s equivalent dose of conjugated equine estrogen (CEE) (0.45 mg/day). The experimental period lasted for 20 months (equivalent to 5 years in humans). At the end of the experiment, prevalence of atherosclerotic plaques was determined. From those monkeys with affected arteries, plaque extent, severity and prevalence of stenosis were determined. Results: Prevalence: The CEE treated group had significantly fewer monkeys with coronary artery atherosclerosis compared to the CTL group (CTL: 57 % vs. CEE: 33 % p=0.005). Extent: Among affected monkeys, the mean plaque size was significantly smaller in the CEE treated group compared to the CTL group (CTL: 0.30 ± 0.048 mm2 vs. CEE: 0.153 ± 0.028 mm2 p=0.015). Remodeling: The proportion of stenotic plaques was lower in the CEE group compared to the CTL group (CTL: 11.14 % vs. CEE: 1.34 % p= 0.008). Severity: CEE treatment did not have a beneficial effect on coronary artery severity (% of complicated [AHA grade≥ III] plaques- CTL: 52.34 % vs. 49.61 %, p=0.397). Conclusions: These histomorphometric findings support previous evidence that beginning of estrogen therapy in the perimenopausal transition prevents plaque initiation. Among affected cases, estrogen treated monkeys had smaller plaques but were equally complicated. Notably, estrogen also promoted positive arterial remodeling among affected arteries.

The Role of CT Angiography of Coronaries in Early Diagnosis of Coronary Artery Plaques in Albanian People with No History of Cardiovascular Disease in Correlation with Traditional Risk Factors

Objective:To evaluate the role of CT angiography of coronaries (CTAC) in the diagnosis of subclinical atherosclerosis by detection of coronary artery plaques (CAP) in a group of consecutive albanian individuals with no history of coronary artery disease (CAD) or acute coronary syndrome and to investigate the relation between the prevalence of CAP, traditional risk factors and the expected 10-year risk of fatal cardiovascular event (CVE) based on our own experience.Method and Technique:This is a prospective study including 456 patients with no history of CAD who underwent CTAC in our hospital from September 2009 to March 2013. Risk estimation of fatal CVE was assessed using Systematic Coronary Risk Evaluation (SCORE) and then CT scan was performed with a 64 detector CT, including Ca Score and angiography of coronaries with iv contrast.Results:From 456 patients 61.4% were low risk and 32.9% were at intermediate risk according to SCORE. The prevalence of CAP diagnosed by CTAC was calculated as 55.7 % overall. Though the presence and severity of CAP increased significantly with the increase of SCORE, it was found to be 44.1% in the low risk patients and 80% in the intermediate risk group, with a presence of 17% and 25% of stenotic plaques (>50%) respectively. Significant correlation was found between all traditional risk factors and CAP.Conclusion:Although a direct relation between the prevalence of CAP, risk factors and the related 10-year risk of fatal CVE was found, there was a significant prevalence of CAP in low –intermediate risk group with a considerable presence of stenotic lesions. Also 8.3% of patients with no risk factors and 18% of the patients with Ca score 0 had CAP in CT angiography, one resulting with severe stenosis. Our results suggest once more that CT angiography is a reliable, very accurate noninvasive technique for the diagnosis of early CAD, especially in the low-intermediate risk patients compared to the traditional evaluation schemes and Ca score, thus should be considered in this group as a diagnostic guide for optimal therapy planning.