Implantation Depth Research Articles

Correlation of prosthesis position on mid-term pacing burden in patients with new permanent pacemaker after TAVI

Abstract Background Prior studies suggest a strong correlation of the final prosthesis position on the occurrence of new conduction disturbances resulting in permanent pacemaker (PPM) implantation after transcatheter aortic valve implantation (TAVI). A high burden right ventricular pacing (PPM stimulation rate of > 20 %) is associated with poor long-term outcomes. So far, data about predictors influencing the PPM stimulation rate after TAVI are scarce. Purpose Thus, the purpose of this study was to evaluate the influence of the three-dimensional transcatheter heart valve (THV) position, as well as device landing zone characteristics or peri-/post-procedural factors on the stimulation rate in patients with new implanted PPM as TAVI complication. Materials: We evaluated the final THV position of 387 patients (106 with self-expanding Evolut R THV, 281 with balloon-expandable Sapien 3 THV) using fusion imaging of pre- and post-TAVI computed tomography angiography (CTA) to obtain a three-dimensional reconstruction of the THV within the native annulus region. The length of the THV above and below the native annulus was measured within the fused images to assess the implantation depth. PPM stimulation rates were examined pre-discharge and after 3 months. Patient’s clinical long-term outcome was evaluated over 5 years via standardized questionnaire as well as contacting general practitioners. Results Out of the 387 patients 112 (29%) received a new PPM pre-discharge after TAVI between 2014 and 2022. They were grouped into patients with stimulations rate below and above 20%. A stimulation rate > 20% in the PPM control before discharge and after three months was detected in 69 % and 67 % of them, respectively. Using uni- and multivariate logistic regression analysis, only new occurred third degree atrioventricular blocks (p=0.007) was identified as predictor for high burden right ventricular pacing after PPM-implantation as well as after 3 months. The implantation depth of the THV showed no influence on the PPM stimulation rate – neither the mean value nor the exact implantation depth adjacent the left, right and non-coronary cusp (P=0.455, P=0.108 and P=0.932, respectively). There were no significant differences regarding MACE between both groups during long-term follow-up; only the degree of dyspnea 5 years after TAVI was significantly higher in patients with a stimulation rate > 20% (p=0.01). Conclusion We detected no correlation of the exact three-dimensional THV position on mid-term pacing burden in 112 patients implanted with a new PPM after TAVI using CTA fusion imaging. Only a new occurred third degree atrioventricular block was a predictor for a high burden right ventricular pacing (stimulation rate >20%). These results provide important insights into which patients actually require PPM implantation after TAVI.

Contemporary implantation protocols enable markedly lower pacemaker rate for selfexpandable TAVR

Abstract Background Even in a low-risk cohort, the Evolut low-risk trial has reported a still rather high pacemaker implantation rate over 20%. In the recent years, contemporary implantation protocols have been introduced aiming on a higher implantation position. Purpose Data on a reduction of pacemaker rate in contemporary implantation practice is still limited. Methods We retrospectively analyzed baseline-characteristics and pacemaker-implantation rates after TAVR in patients being treated with a Medtronic Evolut Prosthesis for aortic valve stenosis in our center in the years 2018 (conventional implantation in 3-cusp view) vs. 2023 (contemporary implantation in cusp overlap technique). Results 160 Patients were retrospectively included. We found out, that contemporary implantation lead to a marked reduction of pacemaker rate (8.7 vs. 20.9%, p=0.047; HR 0.36[IQR 0.14-0.96; p=0.041]). While most baseline-parameters including age (83.5 (79.2/87.3) vs. 82.8 (79.4/86.2), p=0.654), LVEF (55.0 (54.3/57.8) vs. 55.0 (51.0/59.0), p=0.992) and overall risk score (Euroscore II 3.5 (2.5/4.7) vs. 3.6 (2.3/5.7), p= 0.726) had no relevant impact on pacemaker rate, female patients were less prone to receive a pacemaker (8.6% vs. 21.3%, p=0.030). Of all conduction disturbances before procedure, a pre-existing RBBB was strongly associated with a relevantly higher pacemaker rate (50.0% vs. 11.3% (p<0.001), HR 7.88 (IQR 2.73/22.74; p<0.001)). Furthermore, more severe leaflet calcification (p=0.049), a deeper implantation depth (6.0 (5.0/6.5) vs. 5.0 (4.0/60.), p=0.042), larger annular dimensions (perimeter 79.7 (75.2/87.7) 76.8 (71.9/80.7), vs. p=0.047) and prostheses sizes (Evolut 34 vs. smaller sizes 28.1 vs. 12.5%, p=0.053), higher BNP (547 (314/1488) vs. 396 (208/856)), p=0.039 and body weight (78.0 (71.3/90.0) vs. 73.0 (63.5/84.5), p=0.030) were attributed to a higher pacemaker rate. Conclusions In our retrospective database we demonstrated that a contemporary implantation protocol enabling higher implantation position leads to a significant reduction in pacemaker rate, even in the high-risk collective of patients with pre-existing RBBB (58.3 vs. 15.2%, p=0.002 compared to 33.3 vs. 6.3%, p=0.081).

Native Sinus Hemodynamics and Thrombosis in Transcatheter Heart Valve: Effect of Implant Depth and Coronary Flow.

This study aimed to investigate the hemodynamic and anatomic factors associated with sinus thrombosis following transcatheter aortic valve replacement (TAVR), integrating invivo patient data analysis and invitro experiments. Postprocedural, 4-dimensional, multiphase computed tomography data from 211 patients enrolled in the ADAPT-TAVR (Anticoagulation Versus Dual Antiplatelet Therapy for Prevention of Leaflet Thrombosis and Cerebral Embolization After Transcatheter Aortic Valve Replacement) study were analyzed. The prevalence of native sinus thrombosis was examined in relation to valve type, implant depth, and anatomic features. Invitro experiments used particle image velocimetry to observe changes in sinus flow based on the transcatheter heart valves (23-mm SAPIEN3, Edwards Lifesciences; and 29-mm CoreValve, Medtronic) height and coronary artery flow. Native sinus thrombosis was more common in self-expanding valves (39.1% versus 14.9%, P=0.004). In per-cusp analysis of invivo patient data, adjusted transcatheter heart valve implant depth (odds ratio, 1.2 [95% CI, 1.1-1.3]; P<0.001), noncoronary sinus of Valsalva (odds ratio, 4.0 [95% CI, 2.0-7.8]; P<0.001), sinus inflow diameter (odds ratio, 0.8 [95% CI, 0.6-0.9]; P=0.008), and implanted valve size (odds ratio, 0.8 [95% CI, 0.7-1.0]; P=0.025) were significant factors associated with native sinus thrombosis. In the invitro experiments, CoreValve showed noticeable flow stasis compared with SAPIEN3. High-positioned SAPIEN3 was linked to reduced velocity within the native sinus of Valsalva. Coronary artery flow led to higher sinus velocity and improved particle washout, reducing sinus thrombosis risk. This study provides insights into the relationship between transcatheter heart valve deployment and native sinus thrombosis, emphasizing the role of anatomic factors in relation to the risk of sinus thrombosis.

Comparative study of total hip arthroplasty with and without femoral osteotomy in Crowe Ⅳ developmental dysplasia of the hip

To compare the clinical effects of total hip arthroplasty(THA) with and without femoral osteotomy in Crowe Ⅳ developmental hip dislocation(DDH). The data on 46 patients who underwent THA for unilateral Crowe Ⅳ DDH between 2012 and 2017 were analyzed retrospectively. They were divided into two groups according to the different surgical methods. There were 24 patients in the osteotomy group, 3 males and 21 females, with an average age of (47.3±9.0) years old ranged from 34 to 57 years old;and 22 patients in the non-osteotomy group, 2 males and 20 females, with an average age of (51.6±8.3) years old ranged from 40 to 61 years old. The operative time, bleed loss, postoperative drainage volume, postoperative complications, ROM of hip, Harris hip score, limb length discrepancy(LLD), and radiological data were recorded. The femoral dislocation height and the implantation depth of sleeve were measured. All patients were followed up. The mean follow-up time was (3.8±1.2) years ranged from 2 to 6 years in the osteotomy group and (3.2±0.9) years ranged from 1 to 5 years in the non-osteotomy group. The operative time(136.8±18.9) min, bleed loss (709.8±89.4) ml, postoperative drainage volume(308.8±98.2) ml of osteotomy group were all significantly greater than those of non-osteotomy group(100.7±15.8)min, (516.5±103.3) ml, (245.3±79.3) ml (P<0.05). The Harris score at the latest follow up was significantly increased compared with preoperative score in two groups (P<0.05), but there was no significant difference between two groups (P>0.05). The LLD at last follow up was significantly increased compared with preoperative LLD in two groups, the LLD in non-osteotomy group(0.7±0.2) cm showed signifcant smaller than the two osteotomy group(1.2±0.4) cm. Between osteotomy and non-osteotomy groups, the preoperative range of motion of hip joint [(89.5±19.7) °vs (102.5±16.8) °], the preoperative height of dislocation of femoral head [(4.56±0.61) cm vs (3.10±0.73) cm], the proximal implant depth of S-ROM [(0.93±0.36) cm vs (1.67±0.28) cm] was significantly different (P<0.05). Eleven patients in the osteotomy group still had claudication, and 4 patients in the non-osteotomy group had mild claudication (P<0.05). In non-osteotomy group, 3 patients developed nerve injury (1 patient of sciatic nerve, 2 patients of femoral nerve) and 1 case developed periprosthetic fracture. In osteotomy group, 2 case of dislocation and 2 cases of periprosthetic fractures. Whether osteotomy or not can achieve satisfactory results for treating Crowe type Ⅳ DDH and significantly improve LLD. However, osteotomy is more complex and time-consuming, limb length difference is greater, and the incidence of claudication is higher. Furthermore, patients with smaller preoperative hip mobility, higher femoral dislocation, limb lengthening≥4 cm and severely narrow femoral proximal canals are prone to be peformed with subtrochanteric osteotomy.

Exploratory study on a novel minimally invasive tunnel like flap approach for orthodontic movement of dental implants.

To propose a new flap design that utilize a minimally invasive approach to move implants. We also propose a 3D method to track changes in implant position without the need for CBCT. Implants were inserted in two mongrel dogs then a minimally invasive tunnel like flap was made. Bone cutting around implants was done using piezotome device and orthodontic force was applied on the implants. For tracking positional changes of implants, an impression was taken then scanned with an identical implant copy inside. The pre- and post-treatment 3D images were then superimposed over each other to detect changes in implant position. Healing of the flap was rapid with minimal swelling and edema. The position of the interdental papilla was preserved maintaining optimal esthetic outcome. Implant pocket depth was maintained. Our 3D imaging method was able to accurately detect the movement that occurred in the dental implants after their movement with significantly higher resolution than CBCT (6μm for this method versus 76-300μm for the CBCT). This flap can preserve the esthetic soft tissue contour of implants during orthodontic movement allowing rapid healing with minimum swelling and edema. Moreover, our proposed 3D method has many advantages over CBCT in tracking the movement of implants by being non harmful and cheap thus allowing several follow up points. Orthodontic movement of implants can be required in cases of improperly placed implants or to intentionally place the implant in a certain position then altering it to avoid the need for bone grafting.

Assessing post-TAVR cardiac conduction abnormalities risk using an electromechanically coupled beating heart.

Transcatheter aortic valve replacement (TAVR) has rapidly displaced surgical aortic valve replacement (SAVR). However, certain post-TAVR complications persist, with cardiac conduction abnormalities (CCA) being one of the major ones. The elevated pressure exerted by the TAVR stent onto the conduction fibers situated between the aortic annulus and the His bundle, in proximity to the atrioventricular (AV) node, may disrupt the cardiac conduction leading to the emergence of CCA. In this study, an in silico framework was developed to assess the CCA risk, incorporating the effect of a dynamic beating heart and preprocedural parameters such as implantation depth and preexisting cardiac asynchrony in the new onset of post-TAVR CCA. A self-expandable TAVR device deployment was simulated inside an electromechanically coupled beating heart model in five patient scenarios, including three implantation depths and two preexisting cardiac asynchronies: (i) a right bundle branch block (RBBB) and (ii) a left bundle branch block (LBBB). Subsequently, several biomechanical parameters were analyzed to assess the post-TAVR CCA risk. The results manifested a lower cumulative contact pressure on the conduction fibers following TAVR for aortic deployment (0.018MPa) compared to nominal condition (0.29MPa) and ventricular deployment (0.52MPa). Notably, the preexisting RBBB demonstrated a higher cumulative contact pressure (0.34MPa) compared to the nominal condition and preexisting LBBB (0.25MPa). Deeper implantation and preexisting RBBB cause higher stresses and contact pressure on the conduction fibers leading to an increased risk of post-TAVR CCA. Conversely, implantation above the MS landmark and preexisting LBBB reduces the risk.

TCT-912 Impact of Implant Depth in Valve Hemodynamics of Balloon- and Self-Expanding Transcatheter Aortic Valves for Failed Small Surgical Aortic Bioprostheses: A Substudy of the LYTEN Trial

TCT-912 Impact of Implant Depth in Valve Hemodynamics of Balloon- and Self-Expanding Transcatheter Aortic Valves for Failed Small Surgical Aortic Bioprostheses: A Substudy of the LYTEN Trial

Clinical effects of percutaneous elastic intramedullary nail assisted by arthrography for the treatment of radial neck fractures in children

To explore clinical effect of closed reduction percutaneous elastic intramedullary nail assisted by arthrography in the treatment of radial neck fracture in children. A retrospective analysis was performed on 23 children with radial neck fracture treated with arthrography assisted closed reduction and percutaneous elastic intramedullary nail internal fixation (arthrography with elastic nail group) from January 2019 to December 2022, including 12 males and 11 females, aged from 2 to 12 years old with an average of (7.36±1.89) years old;According to Judet fracture types, 14 children were type Ⅲ and 9 children were type Ⅳ. In addition, 23 children with radial neck fracture were selected from January 2015 to December 2018 who were treated with closed reduction and percutaneous elastic intramedullary nail fixation (elastic nail group), including 11 males and 12 females, aged from 2 to 14 years old with an average of (7.50±1.91) years old;Judet classification included 15 children were type Ⅲ and 8 children were type Ⅳ. Operative time and intraoperative fluoroscopy times were compared between two groups. Metaizeau evaluation criteria was used to evaluate fracture reduction, and Tibone-Stoltz evaluation criteria was used to evaluate functional recovery of elbow between two groups. Both groups were followed up for 12 to 24 months with an average of (16.56±6.34) months. Operative time and intraoperative fluoroscopy times of elastic nail group were (56.64±19.27) min and (21.13±7.87) times, while those of joint angiography with elastic nail group were (40.33±11.50) min and (12.10±3.52) times;there were difference between two groups (P<0.05). According to Metaizeau evaluation, 11 patients got excellent result, 9 good and 3 fair in joint angiography with elastic nail group, while in elastic nail group, 5 excellent, 13 good, 4 acceptable, and 1 poor;the difference between two groups was statistically significant (P<0.05). According to Tibone-Stoltz criteria, 14 patients got excellent result, 8 good, and 1 fair in joint arthrography with elastic nail group;while in elastic nail group, 12 patients got excellent result, 9 good, 1 fair and 1 poor;there was no significant difference between two groups (P>0.05). Compared to percutaneous elastic intramedullary nail fixation, closed reduction assisted by arthrography has advantages of reduced operation time, decreased intraoperative fluoroscopy frequency, and improved fracture reduction. Arthrography enables clear visualization of the anatomical structures of radius, head, neck, bone, and cartilage in children, facilitating comprehensive display of fracture reduction and brachioradial joint alignment. This technique more precisely guides the depth of elastic intramedullary nail implantation in radius neck, thereby enhancing surgical efficiency and success rate.

Effects of Carbon Deposition on Deuterium Plasma-Driven Permeation Through Tungsten-Coated RAFM Steel

In steady-state operation of fusion reactors, eroded materials and contaminations, especially carbon (C), may deposit on the surface of plasma-facing components. In this work, the effects of C deposition on hydrogen isotope permeation behavior through tungsten (W)–coated reduced activation ferritic/martensitic (RAFM) steel were systematically investigated by plasma-driven permeation (PDP) measurements in the temperature range of 633 to 893 K. A C deposition layer with thickness of ~200 nm was prepared by magnetron sputtering to simulate the formation of C impurities in the first-wall area of tokamaks. The implantation depth of incident deuterium (D) ions was estimated to be <10 nm at incident energy of 114 eV. Deuterium effective diffusion coefficients (Deff’s) for W-coated RAFM steel with/without a C layer were obtained. It was found that the C layer tended to increase Deff in the low-temperature region of ~675 to 820 K. At high temperature, however, Deff was measured be lower than that without a C layer. Nevertheless, the addition of a C layer had no significant effect on Deff compared to the W coating alone with respect to bare RAFM steels. For steady-state D-PDP flux, it was found that the C layer significantly decreased D permeation flux at low temperature. But, the permeation flux difference between the samples with/without a C layer became smaller with increasing temperature, indicating that the influence of C deposition on D permeation was negligible at high temperature. Similar D-PDP behavior was detected as increasing the incident ion flux by means of increasing plasma discharge power. Surface reemission of absorbed D as well as the D concentration gradient throughout the sample was found to be influenced by C deposition; therefore, D permeation flux changed correspondingly.

Evaluation Effectiveness of Pre-Treatment Combined with Ultrasound-Guided Suction Curettage in Cesarean Scar Pregnancy: A Retrospective Cohort Study

Background: The objective of this study is to assess the effectiveness of ultrasound-guided suction curettage (UGSC) in conjunction with or without high-intensity focused ultrasound (HIFU) or uterine artery embolization (UAE) for the treatment of three distinct types of cesarean scar pregnancy (CSP). Methods: This was a retrospective study that included subjects diagnosed with CSP in a single tertiary referral centre from January 2015 to December 2020. UGSC associated with/without pretreatment was offered to CSP patients according to the location of pregnancy sac, the depth of implantation and the surrounding blood flowing. The data about baseline characteristics and outcome parameters were analyzed across the three groups. Results: The present study included 434 patients diagnosed with CSP. The majority were cured without severe complication except one case accepted blood transfusion. The baseline data from the three groups did not differ statistically. The UGSC group had the same successful rate of treating type I CSP with a shorter hospital stay (χ2 = 51.771, p = 0.000) compared to the HIFU or UAE groups. Type II CSP presented marked less blood loss (Z = –2.464, p = 0.014) and higher decline ration of beta-human chorionic gonadotropin (β-HCG) (Z = –4.728, p = 0.000) in HIFU group. Treatment success was high in patients with type III CSP in both the HIFU and UAE groups, but the rate of β-HCG decline was higher in the HIFU group (Z = –2.255, p = 0.024). Conclusions: This study suggests that UGSC is an effective and safe option for patients with low-risk CSP. HIFU or UAE combined with UGSC has higher efficacy in high-risk CSP. And HIFU may be superior in reducing bleeding and increasing the rate of β-HCG decline.

Effect of Proton Irradiation on Thin-Film YBa2Cu3O7-δ Superconductor.

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa2Cu3O7-δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6×1016 p/cm2. Upon irradiation, Tc was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above Tc. This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between Tc and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov-Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress Tc.

Impact of Accidental High or Low Implantation Depth on Peri-Procedural Outcomes after Implantation with the Self-Expanding ACURATE neo2.

Background: Precise implantation could play a crucial role in the technical success of transcatheter aortic valve replacement (TAVR) for some prostheses. The impact of an accidental implantation depth (ID) outside the recommended range has not been assessed for the ACURATE neo2 (NEO2). Methods: Data from 1839 patients with severe native aortic stenosis treated with the NEO2 prosthesis were evaluated. We compared the results of prostheses implanted in an ID both inside and outside the recommendations. The outcome assessment followed the Valve Academic Research Consortium-3 criteria. Results: Patients were retrospectively divided into high (<3 mm; n = 412), optimal (3-7 mm; n = 1236), and low (>7 mm; n = 169) implantations. Technical success (94.7% vs. 94.7% vs. 91.7%, p = 0.296) and device success were high (90.1% vs. 89.3% vs. 84.6%, p = 0.112) without differences between groups. Rates of relevant paravalvular regurgitation (PVL; >mild or VinV due to PVL) were comparable (1.2% vs. 1.8% vs. 1.2%, p = 0.759). Even when hemodynamics were superior in the high-implantation group, with greater iEOA (1.01 cm2/m2 vs. 0.95 cm2/m2 vs. 0.92 cm2/m2, p < 0.001), spontaneous embolization or after post-dilatation was more common. Low implantation was associated with a higher rate of associated pacemaker implantation (PPI) (6.1% vs. 8.8% vs. 14.8%, p = 0.001). Conclusions: Implantation with the ACURATE neo2 showed excellent hemodynamic results, including low gradients and a small number of relevant PVL, in line with a high technical success rate that was irrespective of the ID. A favorable outcome can also be achieved in accidental low or high positions. Low implantation was associated with a higher rate of associated pacemaker implantation. Deliberately high implantation should be avoided due to the risk of embolization.

The Effect of Increasing Thread Depth on the Initial Stability of Dental Implants: An In Vitro Study

Background: The long-term success of dental implants largely depends on achieving primary stability, previously described as crucial to obtaining osseointegration and immediate loading protocol requirements. Implant thread depths seem to be one of the key factors influencing primary stability, particularly in low-density bone. Insertion torque (IT) and resonance frequency analysis (RFA) are considered the most reliable tests to assess primary stability. The aim of this work was to evaluate how different thread depths of commercially available dental implants affect primary stability in low-density D3 bone. Materials and Methods: An in vitro study was carried out between February 2024 and March 2024. Twenty-four dental implants were divided into four groups (six implants each) according to their thread depths (Group A: 4 mm, Group B: 4.5 mm, Group C: 5 mm, Group D: 5.5 mm) and were inserted in D3-type artificial bone blocks. The main outcome variables were the IT and the Implant Stability Quotient (ISQ) measured in four different areas of the implant (buccal, lingual, mesial, and distal) with an Osstel® ISQ reader. Descriptive and inferential analyses of the data were performed, and the significance value was set at 5%. Results: A total of 24 implants were analyzed. The highest IT values were obtained in Group D, with a mean of 54.03 Ncm (standard deviation (SD) = 8.99), while the lowest measurements were observed in Group A (mean = 25.12; SD: 2.96 N.cm). The mean ISQ values were consistently higher in Group D for each analyzed area, with a mean of 70.13 N.cm (SD = 1.12). Conclusions: Taking into consideration the limitations of this in vitro study, greater thread depths seem to increase the primary stability of dental implants placed in soft bone. Furthermore, a positive correlation was observed between all IT and ISQ values, regardless of the thread depth.

Mid-infrared Measurements of Ion-irradiated Carbonaceous Meteorites: How to Better Detect Space Weathering Effects

Remote sensing study of asteroids will soon enter a new era with an increasing amount of data available thanks to the JWST, especially in the mid-infrared (MIR) range that allows identification of mineral species. It will then be possible to establish a taxonomy, as is currently available in the visible–near-infrared range, based on MIR spectral parameters. It had been previously shown that the MIR range is very sensitive to space weathering (SpWe) effects. Thus, it is crucial to determine which spectral changes are involved to disentangle initial composition from surface aging and provide tools to interpret future remote sensing data of asteroids. We present here MIR measurements of a wide variety of ion-irradiated carbonaceous chondrites as a simulation of the solar wind SpWe component. We evaluate several parameters (the Christiansen feature and Reststrahlen band positions, the width of the main Si–O band) and test different measurement conditions (ion energy and geometry of observation). We highlight a dependency of the spectral changes with the initial composition, as hydrated samples are more affected than anhydrous ones. We confirm the role of the geometry in the detection of SpWe effects as already shown in the near-infrared, with a competition effect between the depth probed by photons and the implantation depth of ions (function of the energy used). We will discuss the results in the framework of future observations and Ryugu’s and Bennu’s samples studied in the laboratory.

Exploring the suppression methods of helium-induced damage in tungsten by investigating the interaction between beryllium and helium

Abstract Helium (He)-induced damage is a sensitive concern for the performance of tungsten plasma facing materials (W-PFMs). Recent experiments have revealed that trace impurities in He plasma can effectively prevent the formation of He bubbles and fuzz on W surfaces. To explore its plausibility and underlying mechanism, we performed a multiscale computational study that combines density functional theory calculations and object kinetic Monte Carlo simulations to investigate the effects of a small quantity of beryllium (Be) on the evolution of He bubbles. It is found that there is a strong attractive interaction between He and Be, which can be attributed to the decrease in electron density and the lattice distortion induced by embedded Be atoms. Therefore, the co-implantation of Be continuously introduces trapping centers for He. Due to the low implantation depth and high migration energy of Be, the Be atoms are located close to the surface, leading to the trapping of the majority of He within the near-surface region and the development of a shielding layer for He permeation. The presence of Be facilitates the dispersion of the trapped He, skewing the He clusters into smaller sizes. More importantly, the Be trapping centers bring the He clusters closer to the surface, significantly increasing the probability of bubble bursting and the release of He back to the vacuum. This ultimately leads to a lower retention of He in the case of He + Be co-irradiation, compared with the case of He-only irradiation. Consequently, our findings elucidate the suppressive effect of a low flux of Be atoms on the growth of He bubbles, highlighting the need to focus on synergetic effects between plasma species.

Predictors and clinical outcomes of permanent pacemaker implantation after transcatheter aortic valve implantation

ObjectiveThis study aimed to identify the incidence, risk factors, and outcomes of permanent pacemaker (PPM) implantation after transcatheter aortic valve implantation (TAVI) procedures.MethodsA retrospective analysis was conducted on 70 patients who underwent TAVI at the Department of Cardiology, Fujian Provincial Hospital, from January 2018 to March 2022. Based on whether a new PPM was implanted after TAVI, all patients were divided into two groups: NEW PPM and NO PPM. Baseline characteristics and clinical data were compared between the two groups. Univariate analysis was used to analyze different variables between the two groups. A binary logistic regression analysis was used to evaluate independent correlates for PPM implantation after TAVI.ResultsThe mean age of the 70 patients was 73.1 ± 8.8 years. The incidence of PPM implantation was 17.1%. Patients with diabetes and chronic kidney disease were more likely to require PPM (50% vs. 20.7%, p = 0.042, 25% vs. 5.2%, p = 0.042). Our study did not identify any significant differences in the incidence of electrocardiographic conduction disturbances except for the previous right bundle branch block (RBBB) (NO PPM 6.9% vs. NEW PPM 33.3%, p < 0.05). We found that prosthesis size, implantation depth, procedural duration, and length of hospital and intensive care unit (ICU) stays were comparable between the two groups. The leading independent predictors of PPM implantation were previous RBBB (odds ratio 10.129, p = 0.034).ConclusionThe previous RBBB was the leading independent predictor of PPM implantation. New PPM was not associated with significantly new-onset left BBB, extended post-procedure hospitalization, ICU stay, or procedural duration.Graphical

Predictors of permanent pacemaker implantation for transcatheter self-expandable aortic valve implant in the cusp overlap era.

Predictors of permanent pacemaker implantation (PPMI) after self-expanding transcatheter aortic valve implant (TAVI) were described. Is unknown if PPMI predictors remain in the era of high implants using the cusp overlap (COP). Single-center, prospective, consecutive case series of patients undergoing self-expanding TAVI with the COP approach. The status of PPMI and other clinical events were ascertained at 30 days. A total of 261 patients were included (84% with Evolut, n = 219). Implant depth >4 mm was infrequent (13.8%). TAVI depth (OR 1.259; p = 0.005), first or second-degree auriculo-ventricular block (OR 3.406; p = 0.033), right-bundle (OR 15.477; p < 0.0001), and incomplete left-bundle branch block (OR 7.964; p = 0.036) were found to be independent predictors of PPMI. The risk of PPMI with deep implant and no electrical disturbances was 3%, and 0% with high implant and no prior electrical disturbances. Those who received PPMI had no statistically significant increased risk of death, myocardial infarction, stroke, bleeding events, or vascular complications at 30 days, but longer hospital stay (mean difference 1.43 days more, p = 0.003). Implant depth and prior conduction abnormalities remain the main predictors of PPMI using self-expanding TAVI in the COP era. Patients with high implants and no prior conduction abnormalities may be candidates for early discharge after uneventful self-expanding TAVI, while the rest may need inpatient monitoring regardless of achieving a high implant. The need for PPMI was associated with longer hospital stays.

Magnetic skin effect in Pb(Fe _{1/2}$ Nb _{1/2}$ )O3

Relaxor-ferroelectrics display exceptional dielectric properties resulting from the underlying random dipolar fields induced by strong chemical inhomogeneity. An unusual structural aspect of relaxors is a skin-effect where the near-surface region in single crystals exhibit structures and critical phenomena that differ from the bulk. Relaxors are unique in that this skin effect extends over a macroscopic lengthscale of ∼100 μm whereas usual surface layers only extend over a few unit cells (or ∼nm). We present a muon spectroscopy study of Pb(Fe _{1/2} Nb _{1/2} )O3 (PFN) which displays ferroelectric order, including many relaxor-like dielectric properties such as a frequency broadened dielectric response, and antiferromagnetism with spatially short-range polar correlations and hence can be termed a multiferroic. In terms of the magnetic behavior determined by the Fe3+ ( S=5/2 , L ≈ 0) ions, PFN has been characterized as a unique example of a ‘cluster spin-glass’. We use variable momentum muon spectroscopy to study the depth dependence of the slow magnetic relaxations in a large 1 cm3 crystal of PFN. Zero-field positive muon spin relaxation is parameterized using a stretched exponential, indicative of a distribution of relaxation rates of the Fe3+ spins. This bandwidth of frequencies changes as a function of muon momentum, indicative of a change in the Fe3+ relaxation rates as a function of muon implantation depth in our single crystal. Using negative muon elemental analysis, we find small-to-no measurable change in the Fe3+/Nb5+ concentration with depth implying that chemical concentration alone cannot account for the change in the relaxational dynamics. PFN displays an analogous magnetic skin effect reported to exist in the structural properties of relaxor-ferroelectrics.

Redo-TAVR Feasibility After Sapien-3 Stratified by Implant Depth and Commissural Alignment: A CT Simulation Study

Redo-TAVR Feasibility After Sapien-3 Stratified by Implant Depth and Commissural Alignment: A CT Simulation Study

Influence of Xe+ and Ga+ milling species on the cathodoluminescence of wurtzite and zincblende GaN

III-nitride materials, such as GaN and its alloys, are essential for modern microelectronics and optoelectronics due to their unique properties. Focused ion beam (FIB) techniques play a crucial role in their prototyping and characterization at the micro- and nanoscale. However, conventional FIB milling with Ga ions presents challenges, including surface amorphization and point defect introduction, prompting the exploration of alternative ion sources. Xenon-based inductively coupled plasma or plasma FIB has emerged as a promising alternative, offering reduced damage and better sample property preservation. Despite extensive research on FIB-induced damage in GaN, systematic comparisons between Ga and Xe ion milling on the luminescence characteristics of GaN remain limited. This study aims to fill this gap by evaluating and comparing the extent of FIB-induced damage caused by Ga and Xe ions in wurtzite and zincblende GaN through cathodoluminescence measurements. Our findings indicate that Xe ion milling yields higher integrated intensities compared to Ga ion milling, attributed to shallower implantation depths and reduced lattice disorder. We also observe a decrease in integrated intensity with increasing ion beam acceleration voltage for both wurtzite and zincblende GaN layers. This study provides valuable insights into optimizing FIB-based sample preparation techniques for III-nitride materials, with implications for enhancing device performance and reliability.