Background: The vast majority of transcatheter valve-in-valve (ViV) mitral procedures have been reported with the SAPIEN family. We aimed to report the preliminary experience with the Myval ...balloon-expandable device in this setting. Methods: Multicenter retrospective study of high-risk surgical patients with mitral bioprosthesis degeneration undergoing transcatheter ViV implantation with Myval device. Results: A total of 11 patients from five institutions were gathered between 2019 and 2022 (age 68 ± 7.8, 63% women). The peak and mean transvalvular gradients were 27 ± 5 mmHg and 14.7 ± 2.3 mmHg, respectively, and the predicted neo-left ventricular outflow tract (neo-LVOT) area was 183.4 ± 56 mm2 (range: 171 to 221 mm2). The procedures were performed via transfemoral access in all cases (through echocardiography-guided transeptal puncture (81.8% transesophageal, 11.2% intracardiac)). Technical success was achieved in all cases, with no significant residual mitral stenosis in any of them (peak 7.2 ± 2.7 and mean gradient 3.4 ± 1.7 mmHg) and no complications during the procedure. There were no data of LVOT obstruction, migration, or paravalvular leak in any case. Mean hospital stay was 3 days, with one major vascular complication and no stroke. At 6-month follow-up, there was one case with suboptimal anticoagulation presenting an increase in the transmitral gradients (mean 15 mmHg) that normalized after optimization of the anticoagulation, but no other relevant events. Conclusions: Transseptal ViV mitral implantation with the balloon-expandable Myval device was feasible and safe avoiding redo surgery in high-risk patients with bioprosthesis degeneration.
Severe plastic deformation (SPD) frequently induces phase transformations like decomposition of supersaturated solid solution, dissolution of precipitates, amorphization, nanocrystallization etc. ...Such diffusive phase transitions are combined with SPD-driven accelerated mass transfer. Displacive (or martensitic) phase transitions can also take place and in combination with diffusive ones have not been investigated in depth in severely deformed materials. The goal of this work is to investigate the combination of displacive (austenite↔martensite) and diffusive (decomposition of supersaturated solid solution) phase transitions in two different Cu–Al–Ni shape memory alloys under the influence of high-pressure torsion (HPT). After homogenization in the one-phase (austenitic) β-area of Cu–Al–Ni phase diagram and quenching, the first alloy was in martensitic state (mainly β′3 martensite with a small amount of γ′3 martensite), and the second one remained austenitic (β3 phase). The HPT of these alloys led to the precipitation of α1-phase in the first case and γ1-phase in the second one (as if they were annealed at an effective temperature Teff = 620 ± 20 °C). As a result of precipitation, the matrix in the first alloy was enriched and in the second one depleted in Al. After HPT, both alloys contained mainly β′3 martensite with a certain amount of γ′3 martensite. Thus, the HPT-driven diffusive transformations (precipitation of α1-and γ1-phase) influence the followed displacive (martensitic) transformation. Simultaneously, a dramatic grain refinement is obtained and the reported results open new possibilities to investigate the superelastic and shape memory effects in nanostructured Cu–Al–Ni alloys.
TEM micrograph of the Cu–14.4 wt% Al–4.3 wt% Ni alloy after HPT. The matrix is partly transformed to martensite with some areas are in austenite state. Display omitted
A thermodynamic study, based on high-sensitivity adiabatic calorimetry, of the martensitic transformation undergone by Cu–Al–Ni shape memory alloys is presented. From the specific heat data, the ...thermodynamic function values, and in particular the crystal free energy, as functions of temperature, have been obtained. These results have permitted a careful estimation of the phase transformation temperatures of each
β
3
′
martensite plate as a function of its stored elastic energy. Within this frame, the distribution density of the elastic energy states in the martensitic phase is directly derived from the specific heat data. It also permits a simple analysis of the nucleation processes and gives a convincing explanation of the temperature memory effects.
Quantitative flow ratio (QFR) virtual angioplasty with pre-PCI residual QFR showed better results compared with an angiographic approach to assess post-PCI functional results. However, correlation ...with pre-PCI residual QFR and post-PCI fractional flow reserve (FFR) is lacking.
A multicenter prospective study including consecutive patients with angiographically 50-90% coronary lesions and positive QFR results. All patients were evaluated with QFR, hyperemic and non-hyperemic pressure ratios (NHPR) before and after the index PCI. Pre-PCI residual QFR (virtual angioplasty) was calculated and compared with post-PCI fractional flow reserve (FFR), QFR and NHPR.
A total of 84 patients with 92 treated coronary lesions were included, with a mean age of 65.5 ± 10.9 years and 59% of single vessel lesions being the left anterior descending artery in 69%. The mean vessel diameter was 2.82 ± 0.41 mm. Procedural success was achieved in all cases, with a mean number of implanted stents of 1.17 ± 0.46. The baseline QFR value was 0.69 ± 0.12 and baseline FFR and NHPR were 0.73 ± 0.08 and 0.82 ± 0.11, respectively. Mean post-PCI FFR increased to 0.87 ± 0.05 whereas residual QFR had been estimated as 0.95 ± 0.05, showing poor correlation with post-PCI FFR (0.163; 95% CI:0.078-0.386) and low diagnostic accuracy (30.9%, 95% CI:20-43%).
In this analysis, the results of QFR-based virtual angioplasty did not seem to accurately correlate with post-PCI FFR.
One of the major constraints facing laser speckle imaging for blood-flow measurement is reliable measurement of the correlation time (τ(C)) of the back-scattered light and, hence, the blood's speed ...in blood vessels. In this Letter, we present a new model expression for integrated speckle contrast, which accounts not only for temporal integration but spatial integration, too, due to the finite size of the pixel of the CCD camera; as a result, we find that a correction factor should be introduced to the measured speckle contrast to properly determine τ(C); otherwise, the measured blood's speed is overestimated. Experimental results support our theoretical model.
•The proposed awK contrast approach improves the visualization of dynamic regions in Laser Speckle Contrast Images by attenuating the noise level through adaptive processing.•The novelty of the ...proposed awK contrast approach consists of the analysis and selection of pixels that best contribute to the contrast computation according to the characteristics of each region, dynamic or static.•The obtained results showed that awK reached higher noise attenuation concerning reference methods despite changes in tissue depth and flow velocity.
Background and Objective: Blood vessel visualization is an essential task to treat and evaluate diseases such as port-wine stain. Laser Speckle Contrast Imaging (LSCI) have applications in the analysis of the microvasculature. However, it is often limited to superficial depths because the tissue among skin and microvasculature introduces noise in the image. To analyze microvasculature, traditional LSCI methods compute a Contrast Image (CI) by using a shifting window of fixed size and shape, which is inadequate in images with structures different types of morphologies in it, as happens in LSCI. This work aims to reduce the noise in the CIs to improve the visualization of blood vessels at high depths (> 300 μ m). Methods: The proposed method processes the CIs with analysis windows that change their size and shape for each pixel to compute the contrast representation with pixels more representatives to the region. Results: We performed experiments varying the depth of the blood vessels, the number of frames required to compute the representation, and the blood flow in the blood vessel. We looked for an improvement in the Contrast to Noise Ratio (CNR) in the periphery of the blood vessels using an analysis of variance. Finding that the adaptive processing of the contrast images allows a significant noise attenuation, translated into a better visualization of blood vessels. An average CNR of 2.62 ± 1 and 5.26 ± 1.7 was reached for in-vitro and in-vivo tests respectively, which is higher in comparison with traditional LSCI approaches. Conclusions: The results, backed by the measured CNR, obtained a noise reduction in the CIs, this means a better temporal and spatial resolution. The proposed awK method can obtain an image with better quality than the state-of-the-art methods using fewer frames.
•Influence of Nb on Ti diffusion observed in TiAl intermetallics for aeronautic applications.•γ-TiAl based alloys exhibit a common atomic relaxation associated with Ti diffusion.•Atomic mechanism of ...Ti diffusion impeded by Nb in γ-TiAl based alloys.•Mechanical Spectroscopy allows measuring diffusion at high temperature.
The development of intermetallic titanium aluminides has been driven by the aeronautic and aerospace industries because of the excellent mechanical properties and low density of γ-TiAl based alloys. Up to now, several generations of γ-TiAl based alloys were developed with increasing complexity of the alloy systems. Nb is one of the most important alloying elements in γ-TiAl alloys and although it is considered as a slow diffuser, its influence has not been fully quantified yet. In this work we demonstrate, through mechanical spectroscopy measurements conducted on several γ-TiAl based alloys with different Nb content, that Nb impedes the diffusion of Ti atoms in the α2-Ti3Al phase. Internal friction measurements show a relaxation peak P(α2), which is associated with short distance diffusion of Ti atoms in the α2 phase, involving stress-induced rotation of dipoles Al-VTi-Al, whose activation energy is dependent on the Nb content. The increase of the activation energy is quantified as ΔEa(Ti)= 0.037 eV × at% Nb, being attributed to the next-neighbor interaction of Nb atoms with the local configuration of Ti-VTi. This mechanism also produces a further broadening of the relaxation peak, which is attributed to the near-next-neighbor interactions for high Nb contents. Finally, an atomic model for the mechanism responsible for this relaxation is proposed allowing to explain the observed experimental behavior.
The martensitic transformation of Ni49.5Ti35.5Hf15 high temperature shape memory alloy is characterized by internal friction measurements. The temperatures for the reversible B2 ↔ B19’ transformation ...appear in the range 410–479 K on cooling and 447–526 K on heating. In addition, a strong anomalous pre-martensitic softening of the dynamic modulus is reported in the high-temperature phase, between 850 K and 550 K, evidencing the thermoelastic character of this family of alloys. Based on the analysis of the internal friction spectra, a theoretical and experimental methodology is proposed to measure the Clausius-Clapeyron coefficient through mechanical spectroscopy. This new non-destructive method could be extremely useful for the development of advanced prototypes of shape memory alloys.
•Internal friction on a Ni–Ti-Hf High-Temperature Shape Memory Alloys.•Martensitic transformation on a Ni–Ti-Hf High-Temperature Shape Memory Alloys.•Anomalous pre-martensitic softening measured on a Ni–Ti-Hf Shape Memory Alloy.•Mechanical Spectroscopy allows measuring the Clausius-Clapeyron coefficient.
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