Combined Low-dose Aspirin and Warfarin Anticoagulant Therapy of Postoperative Atrial Fibrillation Following Mechanical Heart Valve Replacement

The safety and efficacy of combined low dose aspirin and warfarin therapy in patients with atrial fibrillation after mechanical heart valve replacement were evaluated. A total of 1016 patients （620 females, mean age of 36.8-4-7.7 years） admitted for cardiac valve replacement and complicated with atrial fibrillation after surgery were randomly divided into study （warfarin plus 75-100 mg aspirin） or control （warfarin only） groups. International normalized ratio （INR） and prothrombin time were main- tained at 1.8-2.5 and 1.5-2.0 times the normal values, respectively. Thromboembolic events and major bleedings were registered during the follow-up period. Patients were followed up for 24±9 months. The average dose of warfarin in the study and control groups was 2.91±0.83 mg and 2.88±0.76 mg, respec- tively （P〉0.05）. The incidence of overall thromboembolic events in study group was lower than that in control group （2.16% vs. 4.35%, P=0.049）. No statistically significant differences were found in hem- orrhage events （3.53% vs. 3.95%, P=-0.722） or mortality （0.20% vs. 0.40%, P=0.559） between the two groups. Combined low dose aspirin and warfarin therapy in the patients with atrial fibrillation following mechanical heart valve replacement significantly decreased thromboembolic events as compared with warfarin therapy alone. This combined treatment was not associated with an increase in the risk of major bleeding or mortality.

Univariate Risk Factors for Prolonged Mechanical Ventilation in Patients Undergoing Prosthetic Heart Valves Replacement Surgery

Data from 736 patients undergoing prosthetic heart valve replacement surgery and concomitant surgery （combined surgery） from January 1998 to January 2004 at Union Hospital were retrospectively reviewed. Univariate logistic regression analyses were conducted to identity risk factors for prolonged mechanical ventilation. The results showed that prolonged cardiopulmonary bypass duration, prolonged aortic cross clamp time and low ejection fraction less than 50 percent （50 %） were found to be independent predictors for prolonged mechanical ventilation. Meanwhile age, weight, and preoperative hospital stay （days） were not found to be associated with prolonged mechanical ventilation. It was concluded that. for age and weight, this might be due to the lower number of old age patients （70 years and above） included in our study and genetic body structure of majority Chinese population that favor them to be in normal weight, respectively.

Anticoagulation early after mechanical heart valve replacement

Objective： To explore the changes of coagulation activity and the characters of anticoagulation early after mechanical heart valve replacement. Methods： All patients only took warfarin orally for anticoagulation. The predicted international normalized ratio （INR） was 1.5 to 2.0. Several coagulation markers were monitored early after valve replacement. Complications associated with anticoagulation were recorded and analyzed. The patients were divided into three groups based on the number and position of mechanical valve prothesis, including group M （mitral valve replacement）, group A （aortic valve replacement） and group D （mitral and aortic valve replacement）.Comparison was made between the three groups. Results： Three events of mild cerebral embolism and five events of mild bleeding occurred during the early postoperative period. One patient suffered from mild cerebral embolism on the 4th day after operation, accompanied by large volume of pericardial drainage. Two patients with bleeding had lower INRs than predicted range. However, INR in one patient with mild cerebral embolism was in the predicted range. There was no significant difference in thrombo time （TT）, activated partial thromboplastin time （APTT） and 1NR on the 3rd day after operation compared to those before operation; meanwhile, plasma fibrinogen （FIB） concentration was higher than that before operation （P〈0.05）. 1NR had no significant changes on the 2nd day after the beginning of anticoagulation compared to that before operation; however, 1NR was significantly elevated on the 4th day （P〈0.05）. Warfarin doses and INRs were similar among the three groups, but FIB concentrations in plasma were higher in groups M and D than in group A （P〈0.01）. Conclusion： Hypercoagulabale state exists early after mechanical heart valve replacement. When anticoagulation begins is determined by the change of coagulation markers, not by the volume of chest or pericardial drainage. INR can not accurately reflect the coagulation state sometimes, especially during the first 3 days after anticoagulation. The number and position of mechanical valve prothesis could affect coagulation state. Therefore, anticoagulation therapy should be regulated accordingly.

Early Postoperative Anticoagulation by Enoxaparin after Mechanical Aortic Valve Replacement

Background: The use of low molecular weight heparin for early anticoagulation after mechanical aortic valve replacement is still a matter of debate even more that the early postoperative phase is associated with maximum of thrombo-embolic and bleeding risks. The objective of this study is to verify the efficacy and the safety of low molecular weight heparin for the early anticoagulation after mechanical aortic valve replacement. Methods and Results: It is a prospective study conducted over 6 months and interested 40 consecutive patients (32 male and 8 female) with a mean age 53.83 ± 16.93 years (19-75 years) who underwent a mechanical aortic valve replacement and received enoxaparin as bridging therapy between continuous unfractionated heparin and fully effective vitamin K antagonist therapy. There was no in-hospital death and no in-hospital thromboembolic events. We report 2 major bleeding events (5%). Conclusion: The use of low molecular weight heparin should be an alternative to explore for early anticoagulation after valve heart surgery and the results of our study must be verified by large randomized studies before drawing any hasty conclusions.

Role of thrombus precursor protein in assessment of anticoagulation in patients with atrial fibrillation after mechanical heart valve replacement

Objective: To explore the role of thrombus precursor protein (TpP) in assessment of anticoagulation and predict the risk of thromboembolism in the patients with atrial fibrillation (AF) after mechanical heart valve replacement. Methods: TpP plasma concentration and international normalization ratio (INR) were measured in 45 patients with atrial fibrillation and 45 patients with sinus rhythm both after mechanical heart valve replacement. Twenty patients with non valvular heart diseases were selected as the control. Furthermore, the patients with AF were divided into groups based on different TpP plasma concentration and TpP plasma concentration and INR were analyzed. Results: After mechanical heart valve replacement, those with AF had higher TpP plasma concentration than those with sinus rhythm. It was found that discordancy existed between INR and TpP plasma concentration in the patients with AF. There were 28 AF patients with TpP plasma concentration lower than 6 μg/ml and without bleeding, who might be at the optimal anticoagulant state. The 95% confidence of the mean INR value was 1.90-2.30 in these patients and TpP plasma concentration was between 2.84-5.74 μg/ml. Conclusion: Patients with AF might face higher risk of thromboembolism after mechanical valve replacement; INR between 1.90-2.30 and TpP plasma concentration between 2.84-6 μg/ml might be the optimal anticoagulant range for patients with AF after mechanical valve replacement.

Compliant to Warfarin Therapy after Mechanical Heart Valve Replacement

Introduction: Effective anticoagulation depends on demographic factors, patient education, drug knowledge and compliance. The aim of our study is to determine the factors that influence compliance to warfarin in the mechanical valve patient population and its relationship with thrombo-embolic and bleeding events. Patients and Methods: 113 patients underwent mechanical valve replacement (Aortic, mitral or both) at King Abdul-Aziz University Hospital, from 2006 to 2012, patients divided into two groups according to warfarin compliant. Results: 113 patients reviewed in our study, 69 (61.1%) patients found compliant, 36 (31.9%) patients found non compliant, and 8 (7.1%) patients missed. The mean age for all patients was 39.25 y: 76 (67.3%) ware male, 37 (32.7%) were female. Mean age for compliant patients was 40.19 y versus 33.3 y for noncompliant patients with p value 0.017. Male patient less complaint than female with significant 0.01, the mean frequency of follow up was less (32.32 days) in compliant vs. (67.73 days) in non complaint patient. Conclusion: younger age, female gender, Arabic race, assistance at home, education, and single drug use are factors associated with patient compliant, non compliance are associated with higher mortality and valve related complication.

The effects of total ankle replacement on ankle joint mechanics during walking

Background:End-stage ankle arthritis impairs joint function and patients' mobility.Total ankle replacement is a surgical procedure to treat severe ankle arthritis.Salto Talaris Anatomic Ankle^(TM)(STAA) was designed to mimic the normal ankle anatomy and flexion/extension of the ankle movement.The purpose of this study was to examine the effect of an STAA ankle replacement on ankle joint function and mechanics during gait.Methods:Five patients with end-stage unilateral ankle arthritis were recruited.Patients performed level walking in a laboratory setting on 2occasions,prior to and 3 months after the STAA ankle surgeries.American Orthopedic Foot and Ankle Society(AOFAS) hindfoot score was obtained.A 12-camera motion capture system was used to perform walking analysis.Gait temporo-spatial parameters and ankle joint mechanics were evaluated.Paired Student's t tests and non-parametric Wilcoxon matched tests were performed to examine the differences in biomechanical variables between the pre-and post-surgery walking conditions.Results:Compared to the pre-surgical condition,at 3 months of post-STAA surgery,patients experienced greater improvement in AOFAS hindfoot score(p = 0.0001);the STAA ankle demonstrated a 31% increase in ankle joint excursion(p = 0.045),a 22% increase in ankle plantarflexor moment(p = 0.075),a 60% increase in ankle power absorption(p = 0.023),and a 68% increase in ankle power production(p = 0.039).Patients also demonstrated a 26% increase in walking speed(p = 0.005),a 20% increase in stride length(p = 0.013),a 15% decrease in double support time(p = 0.043),and a 5% decrease in total stance time(p = 0.055).Conclusion:Three months after surgeries,the STAA patients experienced improvements in ankle function and gait parameters.The STAA ankle demonstrated improved ankle mechanics during daily activities such as walking.

ANINVESTIGATION ON THE REPLACEMENT OF SPHERICAL PAIR BY CROSS-HEAD PAIR IN SPATIAL MECHANISMS

The spatial RSSR crank rocker mechanism is widely used in industry, but, the manufac-turing, mounting and lubrication of S pair are more complicate than R or C pair. This paperdeals with the replacement of S pair by cress-head pair and investigates the equivalence of thetwo mechanisms with output angular displacement and oscillating angle ψ, as the object func-tion. The synthesis in terms of velocity ratio K and ψ and the influence of the cross-headstructure on the replacement have also been discussed.

Mechanical and Frost-resistance Properties of Rural Area Building Waste Hollow Bricks

Serving as recycled coarse aggregate,the pretreated rural building waste was added into the concrete hollow bricks in the varying replacement of 0,20%,40%,60%,80% and 100%.By testing its compressive strength,flexural strength,mass and strength loss after freeze-thaw cycles,the impact of the different replacement on mechanical and frost-resistance properties of concrete hollow bricks was presented through SEM analysis.The experimental results show that,with the increase in recycled coarse aggregate replacement rate,the mechanical and frost-resistance properties show a downward trend;when the replacement rate is 40%,28 d compressive strength and flexural strength of concrete hollow brick demonstrate the good peak value which meet the requirement of the national standard for ordinary small concrete hollow bricks;the interfacial structures of the pretreated recycled concrete is more complicated than those of concrete made of natural aggregate,but the former enjoys better interface bonding and tight structure.

Basic Mechanical Properties and Microstructural Analysis of Recycled Concrete

The regeneration aggregate, natural aggregate, POO42.5 R Portland cement, coal fly ash, and slag powders S95 graining blast furnace, homemade P（AA-co-MA）/PEG carboxylic acid water reducing agent, were used together with recycled concrete aggregate in different regeneration rates to prepare recycled concrete （RC）. The influences of different renewable aggregate ratios on the basic RC replacement mechanical properties, uniaxial compression stress and strain curve, and the elastic modulus and rebound value were investigated.The results show that RC mechanical properties decreases with renewable aggregate replacement rate increasing. The prolongation can reduce the reduced span.

Effect of Waste Marble Powder on Physical and Mechanical Properties of Concrete

The emission of greenhouse gases from cement production is an obstacle for sustainable development of construction industry.The use of waste materials in constructions instead of cement could be a feasible solution to green construction.Waste marble powder with good cementing property can be used in concrete partially replace cement.In this research,the effects of using waste marble powder on the physical and mechanical properties of concrete have been studied.Three groups of particle size and five levels of replacement ratio(5%,10%,15%,20%,25%)for each group have been designed.During the different stage of hydration process,the microstructure,phase composition and thermal properties of marble-cement paste have been investigated,the influence of particle size of marble powder on these properties has been discussed.The compressive strength and stressstrain relation were tested for different series prepared by partially replacing cement at proportions of 5%–25%separately.From the data analysis,it was observed that the using of waste marble powder would affect the hydration products and further affect the mechanical properties of concrete,the addition of marble powder that partially replace the cement at particular proportions in concrete is feasible.

Thrombus precursor protein for monitoring anticoagulation in patients with mechanical valve prosthesis

Objective: To evaluate the plasma concentration of thrombus precursor protein (TPP) in patients after mechanical heart valve replacement, and to explore whether it can be used as a marker for monitoring anticoagulation. Methods: Totally 60 patients who took warfarin after mitral valve replacement and 20 control patients with non-valvular heart diseases were subjected in this study. Their plasma TPP concentration and international normalized ratio (INR) were determined, and compared not only between the anticoagulant patients and the control patients, but also between the patients with atrial fibrillaiton (AF, n=37) and the patients with sinus rhythm (SR, n=23) after mechanical valve replacement. The relationship between plasma TPP concentration and INR in the 60 anticoagulant patients was analyzed with linear regression. Results: It was found that the anticoagulant therapy effectively decreased plasma TPP concentration and elevated INR. In the anticoagulant group, the patients with AF had higher plasma TPP concentration than the others with sinus rhythm (P<0.05), although there was no significant difference in INR level between these 2 groups of patients (P>0.05). No significant correlation was found between plasma TPP concentration and INR in the anticoagulant patients (P>0.05). INR did not accord with plasma TPP concentration in several patients. Conclusion: INR can’t reflect the coagulation status and guide the anticoagulation correctly sometimes; TPP may be a valuable assistant marker for monitoring anticoagulation in patients with mechanical heart valve prothesis; Patients with AF may require higher density of anticoagulation and TPP is strongly suggested to be monitored in these patients.

An Experimental Study on the Flexibility of Prevention against Thrombosis Following Mechanical Valve Replacement by tPA Gene Transduction

Objectives Use a gene suture immersed recombinant tissue-type plasminogen activator （r-tPA）expression plasmid to transduce myocardia to prevent the thrombosis after mechanical tricuspid valve replacement in pigs. Methods A r-tPA gene plasmid was constructed and conjugated to a novel cationic phosphonolipid and a r-tPA gene suture was made. Eighteen pigs were selected and divided into two groups at randomization. There were 9 pigs in the experimental group and 9 in the control group, all the 18 pigs＇ tricuspids were replaced with mechanical valves. The gene threads were sutured into the right ventricular walls near mechanical valves and an ultrasound was used on the surfaces of the right ventricular walls for the gene transfer in the experimental group. Coagulative function, D-dimer level of the blood and the thrombosis on the surfaces of the valves were observed. Results r-tPA gene plasmid was successfully constructed and r-tPA protein was expressed in the ventricular cells around the gene sutures. D-dimer reached its peak level （ 1.67 ±0. 79） μg · mL^-1 in 1 week after operation in two groups, but it decreased to preoperation level thereafter in control group and kept on the high level and reincreased to a new high level （ 1.89 ± 0.79 ） μg · mL^-1 until the end of the experiment in experimental group. The thromboses around the valves were found in all the control group （100%） but only 1 （ 11.11% ） case in experimental group. There were no changes in prothrombin time pre and post operation in two groups. Conclusions Using gene suture immersed r-tPA expression plasmid to transduce myocardia might be a best substitution for life long anti-coagulation therapy for the patients, who underwent operation.

采用T型钢连接的可拆换钢梁抗震性能试验与数值研究

提出了一种采用T型钢连接的可拆换钢梁,在地震作用下T型钢集中耗散地震能量,并在震后通过更换T型钢实现使用功能的恢复。通过合理设计T型钢连接、钢梁中间段和悬臂段的抗弯承载力关系,定义设计承载力削弱系数的取值范围,从而实现T型钢集中损伤耗能,钢梁中间段和悬臂段保持弹性的屈服机制。为了使T型钢连接件实现预期的损伤和最优的耗能效果,设计了4个腹板采用不同截面和材料的T型钢连接件,并对T型钢连接的可拆换钢梁试件进行了低周往复加载试验和有限元分析。结果表明:T型钢连接的可拆换钢梁可以实现预期的屈服机制,达到T型连接件集中耗能的目的;T型钢腹板的残余变形和螺栓应力可以满足拆换条件,拆换后结构功能不变,实现了较为理想的可更换机制。狗骨式腹板截面的T型钢连接件塑性变形更均匀,耗能区域更大,耗能效率提高约30%,拆换时间和残余变形与普通截面相差不大,建议腹板采用狗骨式截面;采用低屈服点钢材可以提高T型钢的耗能效率约40%,在设计承载力系数取值合理的情况下,T型钢腹板可以选择低屈服点钢材。最后,基于试验和有限元结果,考虑到T型钢连接件的可拆换性和钢梁材料利用率,建议设计承载力削弱系数取值为0.65~0.85。

二尖瓣人工机械瓣膜置换术后孕妇临床特征及妊娠结局分析

目的分析二尖瓣人工机械瓣膜置换术后孕妇的临床特征及妊娠结局,为该类人群安全诊疗提供依据。方法收集2013年1月至2023年1月首都医科大学附属北京安贞医院收治的49例二尖瓣人工机械瓣膜置换术后妊娠孕妇的临床资料进行回顾性分析。回顾性分析孕妇年龄、孕周、瓣膜置换时间、新生儿体重、国际标准化比值、分娩方式以及超声心动图的差异,总结患者的临床资料特点及妊娠结局。结果49例孕妇年龄(31±4)岁,孕周(26±14)周,妊娠距瓣膜置换时间(8±5)年,血红蛋白(115±10)g/L,谷氨酸转氨酶(13±8)U/L,血肌酐(45±7)μmol/L,国际标准化比值1.8±0.6,二尖瓣机械瓣膜瓣口面积为(2.4±0.6)cm^(2),二尖瓣机械瓣膜瓣口流速(197±49)cm/s,左心室舒张末期内径(47±5)mm,左心室射血分数(61±6)%。其中发现5例存在瓣膜功能障碍,这中间有3例孕产妇在孕中期(分别为例1孕28周、例2孕30周和例5孕19周)出现机械瓣膜卡瓣,例1孕妇28周胎儿胎死宫内,重新瓣膜置换;例2为保守双联抗血小板治疗,孕34周剖宫产,胎儿出生正常;例5在保护胎儿的情况下重新瓣膜置换,孕37周剖宫产,胎儿出生正常。结论对于接受人工机械瓣膜置换术后的孕产妇,应制定合理的抗凝策略。由于妊娠期间生理状况的变化,抗凝方案需要不断调整。在整个妊娠过程中,应密切监测血压、心率及各项抗凝指标,并定期进行超声心动图检查。同时,应采取多学科联动的综合评估方法,确保妊娠过程中的安全性,为孕产妇提供可靠的诊疗依据,以保证母婴的安全。

单点锁紧装置后基座模块化更换虚拟建造分析

针对FPSO单点系泊系统锁紧装置插板和局部结构因反复焊修导致的焊接裂纹问题,提出一种模块化更换方案,以提高焊接质量、结构可靠性和现场施工效率。采用模块化更换方法,通过热弹塑性数值模拟评估单点锁紧装置后基座更换过程中的焊接变形,优化焊接顺序和坡口设计,以控制焊接过程中的变形和残余应力。同时,考虑模块边界设计和不同模块类型的特殊需求,以适应FPSO单点舱复杂结构的多样性。模拟结果显示,优化后的模块化更换方案实现了焊接变形的最小化,有效控制了焊接变形,保证了后基座模块化更换的装配精度,确保了与安装平面误差在可控范围内。模块化更换方案是一种有效的解决FPSO单点锁紧装置插板和局部结构焊接裂纹问题的方法,为后续相关在线维修或坞修提供参考。

提升RC框架结构抗震韧性的冗余柱性能分析

本文提出了一种通过设置可更换冗余柱以增强钢筋混凝土框架结构抗震韧性的方法。通过冗余柱纵筋在钢筋机械套筒里的锚固长度以控制冗余柱与框架连接节点处的钢筋失效,节点的刚性连接转变为铰链连接。以钢筋直径和锚固长度为变量,对钢筋机械连接套筒试件进行了13组拉伸试验和6组高应力拉压试验,每组包含3个试件,一个试件包含两段钢筋和一个机械套筒。试验结果表明,适当设计机械连接套筒锚固长度,可实现可控成铰性能。将实测数据应用于冗余柱的截面和构件仿真分析中,证明可通过改变钢筋于套筒锚固长度控制当冗余柱极限变形达到设计值时柱端自动成铰,使冗余柱损坏后仍为关键结构柱提供竖向承载能力,同时保护关键柱在遭遇强震时不易发生严重破坏。

微信随访对心脏机械瓣膜置换术后患者抗凝效果及用药依从性的影响

目的探讨微信随访对心脏机械瓣膜置换术后农村患者的华法林抗凝效果及用药依从性的影响。方法选取2022年7月—2023年1月在福建医科大学附属协和医院进行心脏手术治疗的120例农村患者,并且进行为期6个月的随访。排除脱落患者,最终微信组纳入59例,电话组纳入54例。微信组创立了微信群,通过微信平台对患者推送相关信息;电话组通过专病随访平台定期向患者推送短信,并进行电话随访。通过用药依从性量表-8(Morisky medication adherence scale,MMAS-8)和华法林达标天数进行抗凝效果及用药依从性评估,同时观察2组不良事件。结果微信组华法林达标天数百分比为(77.3±8.1)%,高于电话组的(73.3±9.1)%,差异有统计学意义(P<0.05)。2组均未发生严重的出血和血栓事件。随访3个月时,电话组高依从性有5例,中依从性有18例,低依从性有31例;而微信组高依从性有7例,中依从性有32例,低依从性有20例,差异有统计学意义(P<0.05);在随访6个月时,电话组高依从性有7例,中依从性有22例,低依从性有25例;而微信组高依从性有11例,中依从性有34例,低依从性有14例,差异有统计学意义(P<0.05)。结论微信随访相较于电话随访可以更有效地提高华法林抗凝效果,且拥有良好的用药依从性。

基于产物形貌的超声波辅助置换除铜的机理研究

本文开展了超声波辅助硫酸锌溶液净化除铜实验,分析了超声波对于锌置换净化溶液除铜强化机理。研究采用金相显微镜、扫描电子显微镜、X射线衍射仪、ImageJ等技术对置换产物层微观形貌和分布进行表征,并用等离子体发射光谱仪对不同净化阶段的溶液进行铜离子浓度分析。结果表明,超声波对于置换法溶液净化除铜的强化作用受其强度的影响。低强度超声波(500W)对界面产物的影响较小;而高强度超声波(2000W)能够显著影响固体产物层微观形貌和分布,强化固体产物层中的扩散过程,产生的热效应还有利于提高置换反应效率。高功率超声波导致类球形小颗粒在锌表面不连续分布,增大了两相接触面积;同时在固体产物层中形成贯通孔,减少溶液在固体产物层中扩散的结构阻力。

废弃PP纤维再生混凝土基本力学性能试验

目的 针对纤维体积掺量、长径比、再生骨料取代率等因素,探究废弃PP纤维对再生混凝土力学性能的影响,提高废弃纤维利用率。方法 以废弃PP打包带制成不同长径比的纤维作为筋材,以不同体积掺量与不同再生骨料取代率的再生混凝土混合制成11组废弃PP纤维再生混凝土试块,对其进行抗压和抗拉试验。结果 立方体抗压、抗拉强度最佳时的废弃PP纤维体积掺量为1.5%,长径比为47.85;废弃PP纤维再生混凝土的立方体抗压、抗拉强度与再生骨料取代率有关,其强度与再生骨料取代率近似呈线性关系。结论 废弃PP纤维的掺入可以提高再生混凝土的立方体抗压强度和抗拉强度。