Long-term outcomes of mitral valve annuloplasty versus subvalvular sparing replacement for severe ischemic mitral regurgitation

Background: Although practice guidelines recommend surgery for patients with severe chronic ischemic mitral regurgitation (CIMR), they do not specify whether to repair or replace the mitral valve. The purpose of this study was to evaluate the long-term outcomes in patients with severe CIMR undergoing mitral valve annuloplasty (MVA) versus subvalvular sparing mitral valve replacement (MVR).  Methods: 392 consecutive patients who underwent MVA or subvalvular sparing MVR for treatment of severe CIMR were retrospectively reviewed. Results: After adjustment for baseline differences with multivariable regression analysis at 53 months follow-up (interquartile range, 34–81 months), there was no significant difference between the two groups for risk of major adverse cardiac or cerebrovascular events (MACCE), cardiac death, or all-cause death. Propensity score matching extracted 77 pairs. During the follow-up, compared with the MVR group, both the left atrium and left ventricle end-diastolic diameter were markedly larger (p = 0.013 and p = 0.033, respectively), and the incidence of mitral regurgitation recurrence was significantly higher in the MVA group (p < 0.001). No significant difference was observed between the two propensity score-matched groups in composite in-hospital outcomes, overall survival, freedom from cardiac death or MACCE, except subvalvular sparing MVR was associated with a lower incidence of hospitalization for heart failure than MVA (p = 0.015). Conclusions: Subvalvular sparing MVR is a suitable management of patients with severe CIMR, it is more favorable to ventricular remodeling and is associated with a lower incidence of hospitalization for heart failure than MVA

Predicting functional mitral stenosis after restrictive annuloplasty for ischemic mitral regurgitation

Background: Although it has been realized that restrictive mitral valve annuloplasty (MVA) may re­sult in clinically significant functional mitral stenosis (MS), it still cannot be predicted. The purpose of this study was to identify risk factors for clinically significant functional MS following restrictive MVA surgery for chronic ischemic mitral regurgitation (CIMR). Methods: One hundred and fourteen patients who underwent restrictive MVA with coronary artery bypass grafting (CABG) for treatment of CIMR were retrospectively reviewed. Clinically significant functional MS was defined as resting transmitral peak pressure gradient (PPG) ≥ 13 mmHg. Results: During the follow-up period (range 6–12 months), 28 (24.56%) patients developed clinically significant functional MS. The PPG at follow-up was significantly higher than that measured in the early postoperative stage (3–5 days after surgery). Moreover, there was a linear correlation between the two measurements (r = 0.398, p < 0.001). Annuloplasty size ≤ 27 mm and early postoperative PPG ≥ 7.4 mmHg could predict clinically significant functional MS at 6–12 months postoperatively. Conclusions: Chronic ischemic mitral regurgitation patients treated with restrictive MVA and CABG have significant increases in PPG postoperatively. Annuloplasty size ≤ 27 mm and early postopera­tive PPG ≥ 7.4 mmHg can predict clinically significant functional MS at 6–12 months after surgery

Data-Driven Distributed Optical Vibration Sensors: A Review

Distributed optical vibration sensors (DOVS) have attracted much attention recently since it can be used to monitor mechanical vibrations or acoustic waves with long reach and high sensitivity. Phase-sensitive optical time domain reflectometry (Φ-OTDR) is one of the most commonly used DOVS schemes. For Φ-OTDR, the whole length of fiber under test (FUT) works as the sensing instrument and continuously generates sensing data during measurement. Researchers have made great efforts to try to extract external intrusions from the redundant data. High signal-to-noise ratio (SNR) is necessary in order to accurately locate and identify external intrusions in Φ-OTDR systems. Improvement in SNR is normally limited by the properties of light source, photodetector and FUT. But this limitation can also be overcome by post-processing of the received optical signals. In this context, detailed methodologies of SNR enhancement post-processing algorithms in Φ-OTDR systems have been described in this paper. Furthermore, after successfully locating the external vibrations, it is also important to identify the types of source of the vibrations. Pattern classification is a powerful tool in recognizing the intrusion types from the vibration signals in practical applications. Recent reports of Φ-OTDR systems employed with pattern classification algorithms are subsequently reviewed and discussed. This thorough review will provide a design pathway for improving the performance of Φ-OTDR while maintaining the cost of the system as no additional hardware is required

Mechanism and experimental validation of innovative self-centering conical friction damper

Past earthquakes have shown that traditional structural design relies on the component ductility to dissipate the earthquake energy. This has led to significant damage for the structure. Innovative energy dissipation devices have been developed in the past to dissipate the earthquake energy. However, the big disadvantage of energy dissipation devices is the lack of self-centering feature. Significant residual deformation can have effects on the building resilience. Failing to eliminate the residual deformation can lead to prolong downtime and significant financial losses. In this thesis, a novel damper named self-centering conical friction damper (SCFD) is proposed. SCFD utilizes conical, flat surfaces and post-tensioning tendons to resist the earthquake loads in all directions. The conical surfaces force the SCFD to self-center, making the SCFD highly desired for earthquake applications. In this thesis, detailed mechanical behavior for the SCFD was derived using theoretical equations in this thesis. The hysteresis behavior was verified through the experimental tests. The behavior observed from the test matches well with the theoretical solution Using the derived equations, detailed parameter study including the influences of pretension forces, effective stiffness of post tension tendons, slope angle and friction coefficients have been investigated. Results show the hysteresis behavior can be achieved using different combinations of the slope angle, PT tendons and friction coefficients. Overall, high slope and friction coefficients will lead to highly efficient SCFD with lower demands on the PT tendons. Detailed design approaches have been presented which allows the engineers to design SCDF for different applications. Overall, this thesis shows the SCFD can be used efficiently for application in earthquake engineering with stable energy dissipation and self-centering capabilities.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Effect of preoperatively continued aspirin use on early and mid-term outcomes in off-pump coronary bypass surgery: a propensity score-matched study of 1418 patients.

To date, effect of preoperatively continued aspirin administration in off-pump coronary artery bypass grafting (CABG) is less known. We aimed to assess the effect of preoperatively continued aspirin use on early and mid-term outcomes in patients receiving off-pump CABG.From October 2009 to September 2013 at the Fuwai Hospital, 709 preoperative aspirin users were matched with unique 709 nonaspirin users using propensity score matching to obtain risk-adjusted outcome comparisons between the two groups. Early outcomes were in-hospital death, stroke, intra- and post-operative blood loss, reoperation for bleeding and blood product transfusion. Major adverse cardiac events (death, myocardial infarction or repeat revascularization), angina recurrence and cardiogenic readmission were considered as mid-term endpoints.There were no significant differences among the groups in baseline characteristics after propensity score matching. The median intraoperative blood loss (600 ml versus 450 ml, P = 0.56), median postoperative blood loss (800 ml versus 790 ml, P = 0.60), blood transfusion requirements (25.1% versus 24.4%, P = 0.76) and composite outcome of in-hospital death, stroke and reoperation for bleeding (2.8% versus 1.6%, P = 0.10) were similar in aspirin and nonaspirin use group. At about 4 years follow-up, no significant difference was observed among the aspirin and nonaspirin use group in major adverse cardiac events free survival estimates (95.7% versus 91.5%, P = 0.23) and freedom from cardiogenic readmission (88.5% versus 85.3%, P = 0.77) whereas the angina recurrence free survival rates was 83.7% and 73.9% in the aspirin and nonaspirin use group respectively (P = 0.02), with odd ratio for preoperative aspirin estimated at 0.71 (95% confidence interval, 0.49-1.04, P = 0.08).Preoperatively continued aspirin use was not associated with increased risk of intra- and post-operative blood loss, blood transfusion requirements and composite outcome of in-hospital death, stroke and reoperation for bleeding in off-pump CABG. Preoperative aspirin use tended to decrease the hazard of mid-term angina recurrence

Friction and wear mechanism analysis of the electro brush plating Ni-Mo alloy

The Ni-Mo coating as a replacement for hard chrome plating has gained popularity due to its low environmental pollution. This thesis aims to investigate the characteristics of a Ni-Mo alloy brush coating on a 45# steel base material using the brush plating process. The composition of the plating solution was varied to analyze the effects on the surface morphology, microstructure, hardness, and wear resistance of the Ni-Mo coating. The experimental results demonstrate that the surface morphology of the brush coating is significantly influenced by the composition of the plating solution. As the concentration of nickel sulfate and sodium molybdate varies, the coating exhibits a clear preferential growth tendency. Higher nickel sulfate concentration leads to the growth of coating grain along the (111) crystal plane, while higher sodium molybdate concentration encourages the growth of coating grain along the (220) crystal plane. Increased nickel sulfate concentration results in refined coating grains, while increased sodium molybdate concentration causes more distortion and dislocation of the coating layer. It was observed that the brush plating coating of Ni-Mo alloy, with a nickel sulfate concentration of 400–500 g/L and a sodium molybdate concentration of 25–30 g/L, exhibits not only good surface morphology but also higher micro-hardness and wear resistance. Overall, the analysis of the effects of plating composition on the characteristics of Ni-Mo coating is crucial in developing a high-quality and effective coating for industrial applications

Phosphorus Species in Deep-Sea Carbonate Deposits: Implications for Phosphorus Cycling in Cold Seep Environments

Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P in seep carbonates were examined at three deep-sea cold seeps in the South China Sea and East China Sea. The Ca-P accounts for the largest proportion of P—followed by detrital-P, Fe-P, organic-P, and exchangeable-P. The distribution patterns of Ca-P, detrital-P, and organic-P in the seep carbonates differ from one another, as shown by elemental mapping with NanoSIMS and scanning electron microscopy. The covariation of P with Ca and C reveals that Ca-P co-precipitates with Ca-carbonate, which is linked to the process of sulfate-driven anaerobic oxidation of methane. Organic-P is also observed within biofilm-like organic carbon aggregates, revealing the microbial enrichment of P by fluids in the process of anaerobic oxidation of methane. P with a granulated morphology was identified as detrital-P derived from deep sediments. Most importantly, it is evident that Ca-P is positively correlated to the Fe content in all the seep carbonates. This indicates the likelihood that the dissolved P in cold-seep fluids is released primarily from Fe oxides through Fe-driven anaerobic oxidation of methane in deep sediments. These processes associated with different species of P may have significant implications for P geochemical cycling and anaerobic oxidation of methane impelled by Fe and sulfate reduction in cold seep environments

Event-Free Kaplan-Meier Estimates for Preoperative Aspirin and Nonaspirin Use Group.

<p>Shown are percent survival free from Mace (A), survival free of Angina recurrence (B) and survival free from rehospitalization due to cardiac reasons(C). MACE: major adverse cardiac event.</p

Mid-term outcomes of propensity-matched patients based on preoperative aspirin use.

<p>MACE indicates major adverse cardiac events, including death, repeat revascularization and myocardial infarction.</p><p>Mid-term outcomes of propensity-matched patients based on preoperative aspirin use.</p

In-hospital outcomes of propensity-matched patients based on preoperative aspirin use.

<p>SD indicates standard deviation; composite in-hospital outcome includes in-hospital mortality, stroke and reoperation for bleeding. Blood loss is shown as median with 25th and 75th centiles.</p><p>In-hospital outcomes of propensity-matched patients based on preoperative aspirin use.</p