SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Leaflet

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Objective: To use performance-based user-testing to evaluate the effectiveness of balance appointment patient information leaflets (PILs) in conveying important information. Design: The study used a sequential groups design. Twenty participants were asked to find and demonstrate understanding of 11 key points of information contained within two NHS leaflets, A and B (10 participants each), through individual structured-interviews. Participants' views of the leaflets were explored through a short semi-structured interview. Following analysis, a revised leaflet was developed and tested on a further 20 participants. Study sample: 40 participants (25F/15M, aged 46-72) with no experience of balance problems or balance assessment appointments. Results: Participants exhibited difficulties with finding and/or understanding 5/11 and 6/11 points of information within leaflets A and B, respectively. Five out of eleven points of the revised leaflet also posed problems. Ten out of eleven points were understood by > 90% of participants testing the revised leaflet compared with 6/11 points for leaflets A and B. Conclusions: Some balance appointment PILs contain information which is difficult to find and/or understand for some readers. PILs should be evaluated prior to use using performance-based methods, since poor information provision may lead to increased patient anxiety and appointment non-attendance, cancellation, or postponement.

Concepts: Anxiety, Understanding, Perception, Knowledge, Leaflet

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Aims: To demonstrate the feasibility of the Leaflex™ Catheter System, a novel percutaneous device for fracturing valve calcification using mechanical impact in order to regain leaflet mobility. Methods and results: Radiographic analysis of calcium patterns in 90 ex vivo human aortic valve leaflets demonstrated that 82% of leaflets had a typical “bridge” or “half-bridge” pattern, which formed the basis for the catheter design. The therapeutic effect was quantified in 13 leaflets showing a reduction of 49±16% in leaflet resistance to folding after treatment. A pulsatile flow simulator was then used with 11 ex vivo valves demonstrating an increase in aortic valve area of 35±12%. Using gross pathology and histology on fresh calcified leaflets, we then verified that mechanical impacts do not entail excessive risk of embolisation. In vivo safety and usability were then confirmed in the ovine model. Conclusions: We demonstrated preclinically that it is feasible to improve valve function using the Leaflex™ technology. Once demonstrated clinically, such an approach may have an important role as preparation for or bridging to TAVI, as destination treatment for patients where TAVI is clinically or economically questionable and, in the future, maybe even as a means to slow disease progression in asymptomatic patients.

Concepts: In vivo, Demonstration, Aortic valve, Valvular heart disease, Calcification, Aortic valve stenosis, Leaflet, Gross examination

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A 63-year-old man with a bileaflet mechanical aortic-valve replacement presented with a 3-week history of no audible leaflet clicks. Since he had undergone valve placement 6 years earlier, the clicks had always been clearly audible.

Concepts: Leaflet

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A key problem in biology is whether the same processes underlie morphological variation between and within species. Here, by using plant leaves as an example, we show that the causes of diversity at these two evolutionary scales can be divergent. Some species like the model plant Arabidopsis thaliana have simple leaves, whereas others like the A. thaliana relative Cardamine hirsuta bear complex leaves comprising leaflets. Previous work has shown that these interspecific differences result mostly from variation in local tissue growth and patterning. Now, by cloning and characterizing a quantitative trait locus (QTL) for C. hirsuta leaf shape, we find that a different process, age-dependent progression of leaf form, underlies variation in this trait within species. This QTL effect is caused by cis-regulatory variation in the floral repressor ChFLC, such that genotypes with low-expressing ChFLC alleles show both early flowering and accelerated age-dependent changes in leaf form, including faster leaflet production. We provide evidence that this mechanism coordinates leaf development with reproductive timing and may help to optimize resource allocation to the next generation.

Concepts: Photosynthesis, Genetics, Evolution, Model organism, Fern, Leaf, Plant morphology, Leaflet

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Transvenous pacemaker lead occasionally impairs tricuspid valve coaptation because of the direct injury like a perforation, the direct interference with the valve, or the adhesion between the pacemaker leads and the valve leaflets, resulting in severe tricuspid regurgitation. In these situation, tricuspid valve replacement (TVR) is selected after the exchange from transvenous lead to epicardial lead. However this procedure has some problems such as poor threshold of the endcardial lead, the injury and the difficulty in transvenous lead removal. We performed successful TVR without removing transvenous pacemaker lead after the fixation to the annulus of posterior leaflet in tricuspid valve. This technique is useful in a patient with tricuspid regurgitation due to the influence of the pacemaker lead.

Concepts: Natural selection, Tricuspid valve, Tricuspid insufficiency, Regurgitation, Valvular heart disease, Artificial pacemaker, Exchange, Leaflet

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We sought to examine whether elongation of the mitral valve leaflets in patients with hypertrophic cardiomyopathy (HCM) is synergistic to septal wall thickness (SWT) in the development of left ventricular outflow tract obstruction (LVOTO). HCM is a common genetic cardiac disease characterized by asymmetric septal hypertrophy and predisposition towards LVOTO. It has been reported that elongation of the mitral valve leaflets may be a primary phenotypic feature and contribute to LVOTO. However, the relative contribution of this finding versus SWT has not been studied. 152 patients (76 with HCM and 76 non-diseased age, race and BSA-matched controls) and 18 young, healthy volunteers were studied. SWT and the anterior mitral valve leaflet length (AMVLL) were measured using cine MRI. The combined contribution of these variables (SWT × AMVLL) was described as the Septal Anterior Leaflet Product (SALP). Peak LVOT pressure gradient was determined by Doppler interrogation and defined as “obstructive” if ≥ 30 mmHg. Patients with HCM were confirmed to have increased AMVLL compared with controls and volunteers (p < 0.01). Among HCM patients, both SWT and SALP were significantly higher in patients with LVOTO (N = 17) versus without. SALP showed modest improvement in predictive accuracy for LVOTO (AUC = 0.81) among the HCM population versus SWT alone (AUC = 0.77). However, in isolated patients this variable identified patients with LVOTO despite modest SWT. Elongation of the AMVLL is a primary phenotypic feature of HCM. While incremental contributions to LVOTO appear modest at a population level, specific patients may have dominant contribution to LVOTO. The combined marker of SALP allows for maintained identification of such patients despite modest increases in SWT.

Concepts: Heart, Heart disease, Hypertrophic cardiomyopathy, Mitral valve, Left ventricle, Mitral valve prolapse, Hypertrophy, Leaflet

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Extracellular and cytosolic leaflets in cellular membranes are distinctly different in lipid composition, yet they contribute together to signaling across the membranes. Here we consider a mechanism based on long-chain gangliosides for coupling the extracellular and cytosolic membrane leaflets together. Based on atomistic molecular dynamics simulations, we find that long-chain GM1 in the extracellular leaflet exhibits a strong tendency to protrude into the opposing bilayer leaflet. This interdigitation modulates the order in the cytosolic monolayer and thereby strengthens the interaction and coupling across a membrane. Coarse-grained simulations probing longer time scales in large membrane systems indicate that GM1 in the extracellular leaflet modulates the phase behavior in the cytosolic monolayer. While short-chain GM1 maintains phase-symmetric bilayers with a strong membrane registration effect, the situation is altered with long-chain GM1. Here, the significant interdigitation induced by long-chain GM1 modulates the behavior in the cytosolic GM1-free leaflet, weakening and slowing down the membrane registration process. The observed physical interaction mechanism provides a possible means to mediate or foster transmembrane communication associated with signal transduction.

Concepts: Protein, Cell membrane, Molecular dynamics, Interaction, Signal, Communication, Membrane, Leaflet

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Mitral valve repair has been one of the widely used applications of robotic surgery. Patients with rheumatic mitral disease usually present at an early age with thickening, retraction, or fusion of the leaflets and subvalvular apparatus. Robotic mitral repair can be feasible among this group of patients, rather than replacement. Herein, we describe a young woman who presented with rheumatic mitral valve insufficiency. A complex mitral repair with posterior leaflet extension with an autologous pericardial patch was successfully conducted using robot assistance.

Concepts: Medicine, Rheumatic fever, Mitral valve, Mitral regurgitation, Mitral valve prolapse, Mitral stenosis, Mitral valve repair, Leaflet

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Golden trumpet, Tabebuia chrysotricha, is a native tree from the Brazilian Atlantic rain forest, with a broad latitudinal distribution. In this study, we investigated the potential effects of short-term changes in micro-weather conditions on structural features, and total protein and carbohydrate content of golden trumpet leaves, using structural and histochemical approaches. Leaves were harvested in four different micro-weather conditions: 1. Afternoon, after a hot, sunny day; 2. at dawn, after a previously hot, sunny day; 3. at noon, of a hot, sunny day; and 4. at noon, of a cold, cloudy day. Leaflets exposed to low light irradiance showed flattened chloroplasts, uniformly distributed within the cells, throughout the palisade parenchyma. Conversely, leaflets exposed to high light irradiance presented flattened and rounded chloroplasts, in the upper and lower palisade parenchyma cells, respectively. The strongest protein staining was found for leaves harvested at the coldest period, whereas the weakest protein staining was found for leaves harvested after a hot, sunny day. The largest and most numerous starch grains were found for leaves harvested in the afternoon, after a hot, sunny day. Conversely, the smallest and less numerous starch grains were found for leaves harvested at dawn. Analysis of the data reported herein suggests that the leaflet responses to transient changes in micro-weather conditions are likely to contribute to the golden trumpet successful establishment in the broad latitudinal distribution in which the species is found.

Concepts: DNA, Photosynthesis, Glucose, Starch, Forest, Leaf, Leaflet, Tabebuia chrysotricha

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Transcatheter aortic valve (TAV) implantation within a failed bioprosthetic valve is a growing trend for high-risk patients. The non-compliant stent of the previous prosthesis may prevent full expansion of the TAV, which has been shown to distort the leaflet configuration, and has been hypothesized to adversely affect durability. In this study, TAV leaflet fatigue damage under cyclic pressurization in the setting of stent underexpansion by 0 (fully expanded), 1, 2 and 3 mm was simulated using finite element analysis to test this hypothesis. In the 2 and 3 mm underexpanded devices, the TAV leaflets exhibited severe pin-wheeling during valve closure, which increased leaflet stresses dramatically, and resulted in accelerated fatigue damage of the leaflets. The leaflet fatigue damage in the 1 mm underexpanded case was similar to that in the fully expanded case. Clinically a range of 10-15% underexpansion is generally considered acceptable; however, it was observed in this study that ≥2 mm (≥9.1%) underexpansion, will significantly impact device durability. Further study is necessary to determine the impact of various deployment conditions, i.e. non-uniform and non-circular deployments and different implantation heights, on differing TAV devices, but it is clear that the normal TAV leaflet configuration must be preserved in order to preserve durability.

Concepts: Scientific method, Observation, Device, Finite element method, Hypothesis, The Normal, Partial differential equation, Leaflet