The phase state of NiTi implant material affects osteoclastic attachment

In the present work, the responses of mature osteoclasts cultured on austenite and martensite phases of NiTi shape memory implant material were studied. We used the sensitivity of osteoclasts to the underlying substrate and actin ring formation as an indicator of the adequacy of the implant surface. The results showed osteoclasts with actin ring on both NiTi phases. However, significantly more osteoclasts were present on the austenitic NiTi than on the martensitic NiTi. We also analyzed the surface free energy of the samples but found no significant difference between austenite and martensite phases. The results revealed that osteoclasts tolerated well the austenite phase of NiTi. The chemically identical martensitic NiTi was not as well tolerated by osteoclasts (e.g., indicated by diminished actin ring formation). This leads to the conclusion that certain physical properties specific to the martensitic NiTi have an adverse effect to the surviving of osteoclasts on this NiTi phase. These results confirm that mature, authentic osteoclasts can act as cell probes in experiments concerning aspects of biocompatibility of bone implant materials.     

Development of 3D Printed Mitral Valve Constructs for Transcatheter Device Modeling of Tissue and Device Deformation

Annals of Biomedical Engineering - Transcatheter mitral valve repair (TMVR) therapies offer a minimally invasive alternative to surgical mitral valve (MV) repair for patients with prohibitive...     

Characterization of a CMOS sensing core for ultra-miniature wireless implantable temperature sensors with application to cryomedicine

In effort to improve thermal control in minimally invasive cryosurgery, the concept of a miniature, wireless, implantable sensing unit has been developed recently. The sensing unit integrates a wireless power delivery mechanism, wireless communication means, and a sensing core—the subject matter of the current study. The current study presents a CMOS ultra-miniature PTAT temperature sensing core and focuses on design principles, fabrication of a proof-of-concept, and characterization in a cryogenic environment. For this purpose, a 100 μm × 400 μm sensing core prototype has been fabricated using a 130 nm CMOS process. The senor has shown to operate between −180 °C and room temperature, to consume power of less than 1 μW, and to have an uncertainty range of 1.4 °C and non-linearity of 1.1%. Results of this study suggest that the sensing core is ready to be integrated in the sensing unit, where system integration is the subject matter of a parallel effort.     

Design,Analysis and Testing of a Novel Mitral Valve for Transcatheter Implantation

Mitral regurgitation is a common mitral valve dysfunction which may lead to heart failure. Because of the rapid aging of the population, conventional surgical repair and replacement of the pathological valve are often unsuitable for about half of symptomatic patients, who are judged high-risk. Transcatheter valve implantation could represent an effective solution. However, currently available aortic valve devices are inapt for the mitral position. This paper presents the design, development and hydrodynamic assessment of a novel bi-leaflet mitral valve suitable for transcatheter implantation. The device consists of two leaflets and a sealing component made from bovine pericardium, supported by a self-expanding wireframe made from superelastic NiTi alloy. A parametric design procedure based on numerical simulations was implemented to identify design parameters providing acceptable stress levels and maximum coaptation area for the leaflets. The wireframe was designed to host the leaflets and was optimised numerically to minimise the stresses for crimping in an 8 mm sheath for percutaneous delivery. Prototypes were built and their hydrodynamic performances were tested on a cardiac pulse duplicator, in compliance with the ISO5840-3:2013 standard. The numerical results and hydrodynamic tests show the feasibility of the device to be adopted as a transcatheter valve implant for treating mitral regurgitation.     

Percutaneous and off-pump treatments for functional mitral regurgitation

A new era in the treatment of functional mitral regurgitation is emerging with new devices that can be placed percutaneously or minimally invasively without cardiopulmonary bypass. These devices are categorized into three groups: annuloplasty, edge-to-edge repair, and ventricular reshaping. Percutaneous annuloplasty devices, implanted via the coronary sinus, mimic surgical annuloplasty by reducing the mitral annular anterior-posterior (or septal-lateral) dimension. Several devices, such as the PTMA, CARILLON, Monarch, and PS3 systems, are in clinical trials. Percutaneous edge-to-edge repair devices mimic the surgical Alfieri edge-to-edge repair technique, creating a double-orifice mitral valve; of these, MitraClip is in clinical trials. Ventricular reshaping devices treat both mitral annular dilatation and papillary muscle displacement (and thus leaflet tethering). The surgical Coapsys device is currently in clinical trials, and its percutaneous “interventional” version, iCoapsys, is being prepared for a clinical trial. Numerous issues need to be addressed before these devices can become standard therapies for functional mitral regurgitation. Device safety and efficacy must be demonstrated in carefully designed clinical trials with the goal of achieving outcomes equal to or better than those of surgical repair.     

右胸骨旁微创小切口体外循环停跳下二尖瓣置换术20例

目的 探讨右胸骨旁微创小切口体外循环停跳下二尖瓣置换术治疗二尖瓣病变的可行性,评价其临床应用价值。方法 回顾性分析2016年9月—2017年5月蚌埠医学院第一附属医院心脏外科采用右胸骨旁微创小切口体外循环停跳下行二尖瓣置换术20例患者的临床资料,其中男6例、女14例,年龄39~72(55±3.8)岁。均通过右胸骨旁第四肋间6~10 cm横切口进胸,股动脉插管、右房房腔管引流建立体外循环,经胸直视下阻断升主动脉,心脏停跳后经左房入路行二尖瓣置换。结果 无围术期死亡,体外循环时间118～205(150.3±37.2)min,主动脉阻断时间98～189(133.5±27.4)min,术后机械通气时间(11.1±10.4)h,ICU停留时间(1.3±0.5)d,住院时间(7.3±1.7)d。患者术后平均随访(2.1±1.7)月,瓣膜位置均良好、启闭功能正常,无瓣周漏发生及严重心脑血管并发症出现。结论 作为向全胸腔镜下二尖瓣置换过渡的一种微创术式,右胸骨旁微创小切口体外循环停跳下二尖瓣置换术安全、可靠,早期临床效果确切。     

Impact of thermomechanical texture on the superelastic response of Nitinol implants

The phenomenon of superelasticity in near-equiatomic NiTi, which originates from a first-order martensitic phase transition, is exploited in an increasing number of biomedical devices, most importantly endovascular stents. These stents are often manufactured from microtubing, which is shown to be highly textured crystallographically. Synchrotron X-ray microdiffraction provided microstructural, phase, and strain analysis from Nitinol tube sections that were deformed in situ along longitudinal, circumferential, and transverse orientations. We show that the large variation in the superelastic response of NiTi in these three tube directions is strongly influenced by the path that the martensitic transformation follows through the microstructure. Specifically, in severely worked NiTi, bands of 〈100〉 grains occur whose orientation deviates markedly from the surrounding matrix; these bands have an unusually large impact on the initiation and the propagation of martensite, and hence on the mechanical response. Understanding the impact of these local microstructural effects on global mechanical response, as shown here, leads to a much fuller understanding of the causes of deviation of the mechanical response from predictions and unforeseen fracture in NiTi biomedical devices.     

Combining micro computed tomography and three-dimensional registration to evaluate local strains in shape memory scaffolds

Appropriate mechanical stimulation of bony tissue enhances osseointegration of load-bearing implants. Uniaxial compression of porous implants locally results in tensile and compressive strains. Their experimental determination is the objective of this study. Selective laser melting is applied to produce open-porous NiTi scaffolds of cubic units. To measure displacement and strain fields within the compressed scaffold, the authors took advantage of synchrotron radiation-based micro computed tomography during temperature increase and non-rigid three-dimensional data registration. Uniaxial scaffold compression of 6% led to local compressive and tensile strains of up to 15%. The experiments validate modeling by means of the finite element method. Increasing the temperature during the tomography experiment from 15 to 37 °C at a rate of 4 K h⁻¹, one can locally identify the phase transition from martensite to austenite. It starts at ∼24 °C on the scaffolds bottom, proceeds up towards the top and terminates at ∼34 °C on the periphery of the scaffold. The results allow not only design optimization of the scaffold architecture, but also estimation of maximal displacements before cracks are initiated and of optimized mechanical stimuli around porous metallic load-bearing implants within the physiological temperature range.     

Development of injectable, resorbable drug-releasing copolymer scaffolds for minimally invasive sustained ophthalmic therapeutics

Copolymers based on N-isopropylacrylamide (NIPAAm), acrylic acid N-hydroxysuccinimide (NAS) and varying concentrations of acrylic acid (AA) and acryloyloxy dimethyl-γ-butyrolactone (DBA) were synthesized to create thermoresponsive, resorbable copolymers for minimally invasive drug and/or cell delivery to the posterior segment of the eye to combat retinal degenerative diseases. Increasing DBA content was found to decrease both copolymer water content and lower critical solution temperature. The incorporation of NAS provided an amine-reactive site, which can be exploited for facile conjugation of bioactive agents. Proton nuclear magnetic resonance analysis revealed the onset of hydrolysis-dependent opening of the DBA lactone ring, which successfully eradicated copolymer phase transition properties and should allow the gelled polymer to re-hydrate, enter systemic circulation and be cleared from the body without the production of degradation byproducts. Hydrolytic ring opening occurs slowly, with over 85% copolymer mass remaining after 130 days of incubation in 37°C phosphate buffered saline. These slow-degrading copolymers are hypothesized to be ideal delivery vehicles to provide minimally invasive, sustained, localized release of pharmaceuticals within the posterior segment of the eye to combat retinal degenerative diseases.     

Clinical results of minimally invasive open-heart surgery in patients with mitral valve disease: comparison of parasternal and low-sternal approach

Clinical results of minimally invasive mitral valve surgery were retrospectively reviewed, and two different surgical approaches were compared in this study. Between 1997 and 2004, a total of 86 patients with mitral valve disease underwent minimally invasive surgery at the Yonsei University Cardiovascular Center. Age of patients averaged 41.6 +/- 14.0 years and 69 patients were female. Surgical approach included low- sternal incisions with mini-sternotomy, and right parasternal or thoracotomy approach. Either direct aortic or femoral arterial and bicaval cannulations were used in all patients. Patients were divided into two groups according to the method of surgical approach (parasternal (P) vs low-sternal (L)), and the results were compared. Postoperative NYHA functional class improved to 1.1 +/- 0.4 in all patients (no significant statistical difference between two groups). Mean wound length (P: 9.21 +/- 1.10 vs L: 11.24 +/- 0.82 cm, p < 0.05), and mechanical ventilation time (P: 10.42 +/- 4.36 vs L: 12.90 +/- 5.00 min, p=0.04) was significantly shorter in parasternal group, and mean operation time(P:294.74 +/- 59.41 vs. L:259.31 +/- 54.36 min, p=0.03) was significantly shorter in low-sternal group. Mean cardiopulmonary bypass time, and aortic cross clamp time was also shorter in low-sternal group without statistical difference. There were 2 minor wound complications in all patients (p=NS), and no hospital death. Comparing the two different surgical approach of minimally invasive mitral valve surgery, parasternal approach is thought to be more beneficial in reducing postoperative scar, and intubation time.     

Chronic lymphocytic leukemia/small lymphocytic lymphoma involving the aortic valve

Chronic lymphocytic leukemia/small lymphocytic lymphoma is a neoplasm composed of monomorphic small B lymphocytes in the peripheral blood, bone marrow, spleen, and lymph nodes, forming proliferation centers in tissue infiltrates (Muller-Hermelink HK, Montserrat E, Catovsky D, et al. Chronic lymphocytic leukaemia/small lymphocytic lymphoma, in Swerdlow SH (ed). WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France, International Agency for Research on Cancer, 2008, pp. 180-182). We report a case of a 77-year-old man with a medical history of chronic lymphocytic leukemia who presented with worsening chest pain over 8 weeks. Imaging studies revealed severe aortic stenosis and moderate mitral regurgitation. He subsequently underwent minimally invasive aortic valve replacement and mitral repair at our institution. Grossly, the specimen consisted of a trileaflet valve with multiple yellow-white focally hemorrhagic and calcified nodules over its surface. Histologically, a lymphocytic infiltrate composed of monotonous small cells with scant cytoplasm was seen as well as calcification and fibrosis. Immunohistochemical stains were positive for CD20, PAX5, CD5, and CD23. To our knowledge, this is the first reported case of an immunohistochemically documented chronic lymphocytic leukemia/small lymphocytic lymphoma to involve a cardiac valve.     

Transcatheter Mitral Valve Repair Therapies: Evolution,Status and Challenges

Mitral regurgitation is a common cardiac valve lesion, developing from primary lesions of the mitral valve or secondary to cardiomyopathies. Moderate or higher severity of mitral regurgitation imposes significant volume overload on the left ventricle, causing permanent structural and functional deterioration of the myocardium and heart failure. Timely correction of regurgitation is essential to preserve cardiac function, but surgical mitral valve repair is often delayed due to the risks of open heart surgery. Since correction of mitral regurgitation can provide symptomatic relief and halt progressive cardiac dysfunction, transcatheter mitral valve repair technologies are emerging as alternative therapies. In this approach, the mitral valve is repaired either with sutures or implants that are delivered to the native valve on catheters introduced into the cardiovascular system under image guidance, through small vascular or ventricular ports. Several transcatheter mitral valve technologies are in development, but limited clinical success has been achieved. In this review, we present a historical perspective of mitral valve repair, review the transcatheter technologies emerging from surgical concepts, the challenges they face in achieving successful clinical application, and the increasing rigor of safety and durability standards for new transcatheter valve technologies.     

Deep flexion helps to avoid popliteal artery injury during all-inside lateral meniscal repair: A cadaveric study

BackgroundArthroscopic meniscus repair rarely leads to major complications such as popliteal artery injury. The distance between the suturing device and the popliteal artery, and the risk of popliteal artery injury at different knee flexion angles during all-inside lateral meniscal repair remain unclear.MethodsAll-inside devices were inserted into 10 human cadaveric knees at the posterior horn of the lateral meniscus through the anterolateral portal at 60°, 90°, and 120° knee flexion; posterior segment of the lateral meniscus through the anterolateral portal at 60°, 90°, and 120°; and anteromedial portal at 90°. Distance and positional relationship between the device and popliteal artery were measured radiographically.ResultsIn posterior horn repair through the anterolateral portal, the median distance increased from 5.7 mm at 60° to 9.1 mm at 90° (P = 0.63) and 18.0 mm at 120° (P = 0.02). The device pushed the wire at 60° in three cases, 90° in one case, and 120° in 0 cases. In posterior segment repair through the anterolateral portal, the median distance was 12.6 mm at 60°, 10.4 mm at 90°, and 18.3 mm at 120° (P = 0.08). The median distance at 90° was 18.1 mm through the anteromedial portal, the same as that at 120° through the anterolateral portal (P = 0.43), but greater than that at 90° through the anterolateral portal (P = 0.04). The wire was not pushed in any case.ConclusionAlthough all-inside repair of the posterior part of the lateral meniscus through the anterolateral portal is risky, deeper knee flexion reduces the risk of popliteal artery injury.     

Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment

A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.     

两种人工瓣环置入修复单纯二尖瓣环扩张引起的二尖瓣关闭不全的比较

背景：退行性二尖瓣关闭不全的病例有逐渐增加的趋势,而单纯二尖瓣环扩张引起的二尖瓣关闭不全是退行性二尖瓣关闭不全的一种类型,国内尚无关于此类二尖瓣关闭不全的外科治疗的临床研究报告。 目的：观察单纯瓣环置入修复单纯二尖瓣环扩张引起的二尖瓣关闭不全早中期生物相容性的反应。 方法：单纯二尖瓣瓣环扩张致二尖瓣关闭不全患者48例,均行二尖瓣人工瓣环置入修复,其中使用Carpentier-Edwards生理环23例、SJMTM刚性鞍形成形环25例。出院后随访,采用超声心动图观察心功能和二尖瓣反流程度等变化,并比较两种瓣环与宿主生物相容性有无差别。 结果与结论：围术期无死亡,均治愈出院。48例均获随访,随访率100%,随访时间3个月至4年,无死亡病例。NYHA心功能分级Ⅰ级32例,Ⅱ级16例。与术前比较,随访期超声心动图显示左心房内径、左心室舒张末期内径、左心室收缩末期内径、肺动脉收缩压和反流速面积/左房面积均明显减少(P < 0.01),左室射血分数明显增加(P < 0.01)。跨瓣压差均< 3 mm Hg。二尖瓣无明显返流36例,微量返流10例,轻度反流2例。未出现成形环断裂、成形环撕脱及溶血现象。Carpentier-Edwards生理环组和SJMTM刚性鞍形成形环组比较,上述各指标差异无显著性意义(P > 0.05)。结果提示对于因单纯二尖瓣环扩张引起的退行性二尖瓣关闭不全,通过正确的置入技巧、选择合适的人工瓣环,应用人工瓣环置入有与宿主生物较好的生物相容性反应,置入后的瓣膜替代功能良好。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

Computerized acoustic cardiography correlates with echocardiography and invasive haemodynamics after percutaneous transvenous mitral commissurotomy

Background:?Rheumatic mitral stenosis severity has been assessed by the systolic time interval between the QRS onset and the first heart sound (QS1) by phonocardiography. We hypothesized that non-invasive computerized acoustic cardiography could evaluate mitral stenosis severity compared with echocardiography and invasive haemodynamics in patients undergoing percutaneous transvenous mitral commissurotomy (PTMC).

Methods:?27 patients underwent computerized acoustic cardiography, echocardiography, and invasive haemodynamic measurements prior to and after PTMC.

Results:?The mean age was 31?±?10 years, and 21 (78%) were female. By echocardiography, mitral valve area increased from 0.82?±?0.14 to 1.50?±?0.24 cm² (p?<?0.0001). The QS1 interval decreased from 101.7?±?12.9 to 93.2?±?9.2?ms (p?<?0.0001). The change in the QS1 interval correlated with the change in mitral valve area by echocardiography (p?=?0.037), right ventricular systolic pressure (p?<?0.0001), and the invasive mitral valve gradient (p?=?0.076).

Conclusions:?Acoustic cardiography may be used as an adjunctive non-invasive diagnostic tool to assess mitral stenosis severity.     

Comparison of clinical and echocardiographic outcomes after valve repair: degenerative versus rheumatic mitral regurgitation

We compared clinical (30+/-24 months) and echocardiographic follow-up (22 +/- 20 months) data of 184 consecutive patients with myxomatous degenerative mitral regurgitation (Group A) and 85 consecutive patients with rheumatic mitral regurgitation (Group B) after repair. Selection criteria for rheumatic etiology was predominant mitral regurgitation with valve area >or= 2.0 cm(2) and with no significant calcification in valvular apparatus. Repair was successful in 93% of group A and in 92% of group B (p>0.05). There was no difference of operative mortality (1% vs 0%) and of the incidence of the second-pump valve replacement (4% vs 5%). The 4-yr survival, 4-yr event-free survival, and 4-yr mitral regurgitation-free survival rates in group A were 96 +/- 2%, 89 +/- 4%, and 76 +/- 5%, respectively, which were not different from those in group B (97 +/-2 %, 93 +/- 4%, and 68 +/-7 %, p >0.05). Independent determinants of development of at least moderate regurgitation in group A were no use of ring annuloplasty (hazards ratio 6.6, 95% CI 2.0 to 21.5) and new chordae formation (hazards ratio 3.5, 95% CI 1.4 to 8.7). In group B, no use of ring annuloplasty (hazards ratio 15.3, 95% CI 3.5 to 66.7) also was independent predictor. Valve repair is highly feasible in selected patients with rheumatic mitral regurgitation, and clinical course is not significantly different from that of patients with degenerative mitral regurgitation.     

Determination of the pressure required to cause mitral valve failure

A method has been developed for applying water pressure to a closed mitral valve on the side corresponding to the heart's left ventricle. The pressure is increased until fluid flows through the valve, i.e. until it fails. A specific dissection technique has been developed to produce a specimen with two annular rings, mitral annulus and papillary muscle annulus. Since the valve is maintained intact, with its leaflets attached to papillary muscles by the chordae tendineae, this method allows the effects of ruptured chordae and their surgical repair or replacement to be assessed in vitro. The chamber that holds the valve supports both the mitral annulus and papillary muscle annulus of the specimen. The mitral annulus is sutured onto rubber sheeting held in the chamber. The papillary muscle annulus is held in place by a Perspex support. The main part of the apparatus consists of a water pump connected through flexible tubing to the chamber that holds the valve in place. The pressure at failure is measured using a pressure transducer. Preliminary experiments demonstrate that anterior leaflet marginal chordae, but not strut chordae, are vital to valve function. Posterior leaflet chordae have been found to be important for valve competence.     

“缘对缘”二尖瓣成形术治疗交界区脱垂在老年患者中的近中期效果

目的：评价在老年患者中“缘对缘”二尖瓣成形术治疗单纯交界区脱垂的近中期效果。方法：2012年4月至2015年4月,本中心对连续的32例单纯性二尖瓣交界区脱垂的老年患者(≥65岁)施行了二尖瓣成形术,并排除了冠心病、风湿性心脏病、感染性心内膜炎、原发性心肌病等导致的二尖瓣反流患者。其中男性20例,女性12例;年龄65~76岁,平均(68.4±2.8)岁。其中NYHA心功能Ⅱ级18例,Ⅲ级12例,Ⅳ级2例。本组患者手术均采用5-0 prolene缝线行二尖瓣交界区“缘对缘”缝合,闭合交界脱垂区域,且均植入二尖瓣成形环。结果：本组患者全部存活,随访12~48个月。患者术后心功能均明显改善(NYHA心功能Ⅰ级24例,Ⅱ级7例,Ⅲ级1例)。21例患者二尖瓣无或仅有微量反流,11例患者有轻度二尖瓣反流,无中度及以上二尖瓣反流,无SAM征。左心室舒张末期容积(left ventricular end diastolic volume,LVEDV)：术前为(158.2±28.6) mL,术后为(123.2±18.3) mL,术前与术后相比差异有统计学意义(P<0.001)。结论：在老年患者中采用“缘对缘”二尖瓣成形术治疗单纯交界区脱垂,具有简单、有效、易操作的特点,缩短手术时间,且可获得良好和稳定的近中期效果。     

Mitral annulus after mitral repair: geometry and dynamics

The study of systolic changes in both the inflow and outflow of the left ventricle after mitral repair elucidates the geometric characteristics after surgery. The study included eight normal subjects and six patients after mitral repair without a prosthesis. The left ventricular (LV) base, consisting of both mitral valve annulus (MVA) and left ventricular outflow tract (LVOT) orifice, was reconstructed from magnetic resonance images. The angle between the planes of the MVA and LV base (MB angle), and the proportionate share of the LVOT at the LV base were calculated. After mitral repair, both the MVA and LV base became almost normal in size, showing flexible change (i.e., contraction and dorsiflexion) in the MVA and contraction of the LV base in systole. Compared with the normal heart at 100 ms delay from the electrocardiogram R wave, the hearts of the patients at the same phase had a mean 1.05 cm2 larger LVOT orifice, resulting in a mean 8.0 degree larger MB angle. Furthermore, the LVOT orifice occupied a mean of 49.5% of the LV base (41.9% in normal subjects). We hypothesize that the higher MB angle at early systole may weaken the tension of the chordae of the anterior mitral leaflet.