Possible Subclinical Leaflet Thrombosis in Bioprosthetic Aortic Valves

To the Editor: Makkar et al. (Nov. 19 issue)(1) report possible subclinical leaflet thrombosis in up to 40% of patients involved in a clinical trial of transcatheter aortic-valve replacement (TAVR). In contrast, we found a relatively low incidence (7%) of possible subclinical valve leaflet thrombosis among patients in our series in which 255 patients underwent TAVR with the use of a CoreValve prosthesis. A retrospective review of our series (unpublished data) showed that in 104 patients, cardiac computed tomography (CT) at a median of 7 days after implantation (range, 3 to 87) (in 51 patients), transesophageal echocardiography at a median . . 

Byrne v. Maryland Reality Co. and the Elimination of Aesthetic Zoning in Maryland

Today\u27s familiar cry of Not in my backyard! is not new to property owners. In 1915 the familiar cry was raised by a number of homeowners and building associations as they fought to prevent a developer from constructing rowhomes in northwest Baltimore. On May 12, 1915, an opportunity for building developers arose to challenge the limits of acceptable building restrictions in Baltimore with the filing of a permit to build in a restricted area. In a time when cottage style homes were in vogue and suburbanization was the high style, the residents of Forest Park, Baltimore saw the filing of this permit to build a group of rowhomes in their neighborhood as an invasion, an eyesore, and the antithesis of everything they had striven for as a community. For these residents, the sanctity of their quiet suburban cottage community was about to be destroyed solely to meet a growing need for housing. The residents feared the urbanization of their quiet community. The residents of Forest Park were able to breathe a temporary sigh of relief when on May 14, 1915, Mr. Clarence Stubbs, Inspector of Buildings, rejected the application for the permit to build. However, this was only a stay of execution for their cottage community. In less than one year, the idea that a community could shape itself through building type restrictions would disappear. The rationale behind the disagreement between the city with the residents of Forest Park and the Maryland Realty Co. may have been simply due to an overwhelming interest in preserving the continuity of the community and retaining the suburban quality of the area. However, a discriminatory intention may have underpinned the arguments of the residents and the city in favor of preserving the ordinance barring rowhomes in Forest Park. Byrne was not a case about discrimination, but rather, a case of perceived societal improvement through the restriction of the use of land using aesthetics as the key limiting factor. Byrne was about the tension between the owner\u27s property rights and the power of the city to control development. At its most basic, Byrne was a case of dollars and cents, the value of the property to the residents of the quiet suburban community weighed against that individual right of the developer to do whatever he wished with his property

Using Content Provider Signals to Select Individual Content Items for a Content Item Campaign

This document describes a system and method in which signals from a third-party content provider are used to help select content items in the content item campaign of the third-party content provider. The selected content items are then presented to a resource. The signals may be used to help select between content items for which there are known metrics and content items for which there are no metrics. The signals indicate trends or preferences that may indicate that one content item or type of content item is a better choice compared to other content items

Tunable Automatic Placement Finder for Third Party Content

This document describes a technique for performing tuning in automatic content slot placement process. A data processing system can send a script to a client device for automatic content slot placement. The script can be executed by the client device to obtain a chunk size report and to transmit the chunk size report to the data processing system. The data processing system can analyze data in the chunk size report and perform tuning based on the analysis. Parameters for how long to hold the main execution thread at the client device can be modified. The data processing system can also perform tuning based on device characteristics and network characteristics associated with the client device

In silico study of the ageing effect upon aortic valves

A fluid–structure interaction (FSI) numerical model of the aortic valve was used to simulate and compare young and physiological aged operating conditions. The effect of normal ageing was considered by introducing alterations typically associated with senility: namely mild stiffening of the tissues and progressive dilation of the aortic chamber. The aim of this study is to provide a haemodynamic baseline which allows to assess the typical physiological variations associated with advancing age. Results were analysed in terms of leaflets kinematics, flow dynamics, pressure and valve performance parameters. The study indicates that the normal changes occurring with ageing, such as stiffening and progressive aortic root dilation, can result in substantial alterations in the haemodynamics and mechanical efficiency of the aortic valve. In particular, mild tissue stiffening and aortic root dilation reduce the valve efficiency over the cardiac cycle. The concomitant presence of both phenomena can lead to some mitigation of the impairment. The observed changes, which can be associated with normal and healthy ageing, need to be taken into consideration when evaluating the real pathological contribution of aortic valve diseases occurring in aged patients

Possible Subclinical Leaflet Thrombosis in Bioprosthetic Aortic Valves

To the Editor: Makkar et al. (Nov. 19 issue)(1) report possible subclinical leaflet thrombosis in up to 40% of patients involved in a clinical trial of transcatheter aortic-valve replacement (TAVR). In contrast, we found a relatively low incidence (7%) of possible subclinical valve leaflet thrombosis among patients in our series in which 255 patients underwent TAVR with the use of a CoreValve prosthesis. A retrospective review of our series (unpublished data) showed that in 104 patients, cardiac computed tomography (CT) at a median of 7 days after implantation (range, 3 to 87) (in 51 patients), transesophageal echocardiography at a median . . 

Computational Fluid Dynamic Analysis of the Left Atrial Appendage to Predict Thrombosis Risk

During Atrial Fibrillation (AF) more than 90% of the left atrial thrombi responsible for thromboembolic events originate in the left atrial appendage (LAA), a complex small sac protruding from the left atrium (LA). Current available treatments to prevent thromboembolic events are oral anticoagulation, surgical LAA exclusion, or percutaneous LAA occlusion. However, the mechanism behind thrombus formation in the LAA is poorly understood. The aim of this work is to analyse the hemodynamic behaviour in four typical LAA morphologies - “Chicken wing”, “Cactus”, “Windsock” and “Cauliflower” - to identify potential relationships between the different shapes and the risk of thrombotic events. Computerised tomography (CT) images from four patients with no LA pathology were segmented to derive the 3D anatomical shape of LAA and LA. Computational Fluid Dynamic (CFD) analyses based on the patient-specific anatomies were carried out imposing both healthy and AF flow conditions. Velocity and shear strain rate (SSR) were analysed for all cases. Residence time in the different LAA regions was estimated with a virtual contrast agent washing out. CFD results indicate that both velocity and SSR decrease along the LAA, from the ostium to the tip, at each instant in the cardiac cycle, thus making the LAA tip more prone to fluid stagnation, and therefore to thrombus formation. Velocity and SSR also decrease from normal to AF conditions. After four cardiac cycles, the lowest washout of contrast agent was observed for the Cauliflower morphology (3.27% of residual contrast in AF), and the highest for the Windsock (0.56% of residual contrast in AF). This suggests that the former is expected to be associated with a higher risk of thrombosis, in agreement with clinical reports in the literature. The presented computational models highlight the major role played by the LAA morphology on the hemodynamics, both in normal and AF conditions, revealing the potential support that numerical analyses can provide in the stratification of patients under risk of thrombus formation, towards personalised patient care

DETECTION OF POSITION FIXED CONTENT ITEM SLOTS AND CONTROL OF CONTENT DISPLAYED THEREIN

Implementations described herein relate to detection of fixed position content item slots and control of interactions based on determining a content item slot is a fixed position content item slot, such as click protections, policy enforcement mechanism, and/or auction corrections

Elastic properties of 2D auxetic honeycomb structures- a review

The research field of auxetics, materials or structures exhibiting a negative Poisson's ratio, has received attention because of the unusually advantageous material properties that can be achieved with it, such as high indentation resistance and high shear resistance. In the past decades, the theoretical understanding of different factors that can lead to an auxetic behaviour has advanced greatly, resulting in a rapid increase in the number and type of the structures designed to exhibit this behaviour. These now exploit a number of different mechanisms, providing a large selection of properties which can be tailored for the specific needs. This review aims to describes the auxetic structures that have currently been identified and designed, describing the different approaches utilised to define their mechanical behaviour and analysing their structural properties, limitations, and potential field of application. In particular, the focus lies on the major works within the field, discussing their limitations and addressing works done to complement them

Standard mechanical testing is inadequate for the mechanical characterisation of shape-memory alloys: Source of errors and a new corrective approach

Thanks to its unique behaviour characterised by a superelastic response, Nitinol has now become the material of preference in a number of critical applications, especially in the area of medical implants. However, the reversible phase transformation producing its exceptional comportment is also responsible for a number of phenomena that make its mechanical characterisation particularly complex, by hindering the assumptions at the very basis of common uniaxial tensile testing. This necessarily reduces the level of safety and design optimization of current applications, which rely on incorrect mechanical parameters. In this study, the spurious effects introduced by the unconventional material behaviour during uniaxial tensile testing are analysed by means of digital image correlation (DIC), identifying the onset of undesirable material inhomogeneities and bending moments that are dependent on the test setup and strongly limit the reliability of standard characterisation. Hence, a more accurate and systematic testing approach, exploiting the ability of DIC to analyse the local mechanical response at specific regions of the test specimen, is presented and discussed