Valve hemodynamic performance and myocardial strain after implantation of a third-generation, balloon-expandable, transcatheter aortic valve

Background: Left ventricular (LV) mechanics are impaired in patients with severe aortic stenosis (AS); however, transcatheter aortic valve implantation (TAVI) may positively affect LV mechanics. Assessed herein is the performance of the SAPIEN 3 transcatheter heart valve (THV) and the effect of TAVI on LV function recovery, as assessed by global longitudinal strain (GLS). Methods: A subset of patients from the SOURCE 3 registry (n = 276) from 16 European centers received SAPIEN 3 balloon-expandable THV. Echocardiography was performed at baseline, postprocedure, and at 1 year, including assessment of GLS using standard two-dimensional images, and was analyzed in a core laboratory. Paired analyses between baseline and discharge, baseline and at 1 year were conducted. Results: Hemodynamic parameters were improved after TAVI and sustained to 1 year. At 1 year, the rate of moderate to severe paravalvular leaks (PVL), and moderate to severe mitral and tricuspid regurgitations were 1.8%, 1.7%, and 8.0%, respectively. The discharge GLS (–15.6 ± 5.1; p = 0.004; n = 149) improved significantly from baseline (–15.1 ± 4.8) following TAVI. This improvement was sustained at 1 year compared with baseline (–17.0 ± 4.6, p < 0.001; n = 100). Conversely, LV ejection fraction (LVEF) did not significantly change following TAVI (p = 0.47). Conclusions: Following TAVI with a third-generation THV, valve performances were good at 1 year with low PVL rate. The LV mechanics improved immediately after the procedure and were maintained at 1 year. These findings demonstrate the benefit of TAVI on LV mechanics, and suggests that GLS may be superior to LVEF in assessing this benefit. Clinicaltrial.gov number: NCT0269895

Thermodynamic aspects of nanoscale friction

Developing the nonequilibrium thermodynamics of friction is required for systematic design of low-friction surfaces for a broad range of technological applications. Intuitively, the thermodynamic work done by a material sliding along a surface is expected to be partially dissipated as heat and partially transformed into the change of the internal energy of the system. However, general nonequilibrium thermodynamic principles governing this separation are presently unknown. We develop a theoretical framework based on the transition state theory combined with the conventional Prandtl-Tomlinson model, allowing to set explicit expressions for evaluating the heat dissipation and internal energy change produced during the frictional stick-slip motion of a tip of a typical friction force microscope. We use the formalism to quantify the heat dissipation for a range of parameters relevant to materials in practical applications of nanoscale friction

Stochastic thermodynamics of nanoscale friction

Developing the thermodynamics of nanoscale friction is needed in a wide range of tribological applications, where the key objective is to optimally control the energy dissipation. Here we show that modern stochastic thermodynamics allows us to interpret the measurements obtained by friction force microscopy, which is the standard tool for investigating the frictional properties of materials, in terms of basic thermodynamics concepts such as fluctuating work and entropy. We show that this allows the identification of the heat produced during the friction process as an unambiguous measure of thermodynamic irreversibility. We have applied this procedure to quantify the heat produced during the frictional sliding in a broad velocity range, and we observe velocity- dependent scaling behavior, which is useful for interpreting the experimental outcomes

Multi-scale model predicting friction of crystalline materials

A multi-scale computational framework suitable for designing solid lubricant interfaces fully in silico is presented. The approach is based on stochastic thermodynamics founded on the classical thermally activated 2D Prandtl–Tomlinson model, linked with first principles methods to accurately capture the properties of real materials. It allows investigating the energy dissipation due to friction in materials as it arises directly from their electronic structure, and naturally accessing the time-scale range of a typical friction force microscopy. This opens new possibilities for designing a broad class of material surfaces with atomically tailored properties. The multi-scale framework is applied to a class of 2D layered materials and reveals a delicate interplay between the topology of the energy landscape and dissipation that known static approaches based solely on the energy barriers fail to capture.</p

Coronary Access and Percutaneous Coronary Intervention Up to 3 Years After Transcatheter Aortic Valve Implantation With a Balloon-Expandable Valve

Background: Coronary artery disease and aortic stenosis often coexist. Transcatheter aortic valve implantation (TAVI) has emerged as a valid therapeutic option for younger, lower-risk patients who may eventually require coronary artery disease treatment. Thus, post-TAVI coronary access (CA) and percutaneous coronary intervention are expected to increase. The purpose of this study was to retrospectively evaluate patients who were enrolled in the SOURCE 3 (SAPIEN 3 Aortic Bioprosthesis European Outcome) European registry for treatment with the balloon-expandable SAPIEN 3 transcatheter heart valve and underwent CA with or without percutaneous coronary intervention after TAVI. Methods: Baseline characteristics and clinical outcomes of patients with or without CA up to 3 years after TAVI were compared. A Kaplan-Meier estimate with a univariate model determined the impact of CA on cardiac mortality. Results: Of 1936 TAVI patients (mean age 81.6 years, 52% male), 68 (3.5%) had CA within 3 years (mean 441±332 days) after TAVI. At baseline, the logistic EuroSCORE was similar (20.2% versus 18.3%, P=0.2, CA and non-CA groups, respectively). Higher rates of coronary artery disease (76.5% versus 50.6%, P<0.001), myocardial infarction (20.6% versus 11.5%, P=0.03) and previous coronary artery bypass graft (22.1% versus 11.0%, P=0.01) were present in the CA group. In 100% of patients, CA was successfully achieved. The clinical success of percutaneous coronary intervention was 97.9%. Cardiovascular mortality was numerically higher in patients with CA than in those without CA. Conclusions: In the large SOURCE 3 European registry, CA was needed at 3-year follow-up after TAVI with a balloon-expandable valve in 3.5% of patients and was successful in all patients. The clinical success of percutaneous coronary intervention was 97.9%. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02698956