腔镜筋膜外下肢静脉交通支离断术的临床应用探讨

目的:探讨腔镜筋膜外交通支离断术(epifascial laparoscopic perforator surgery,ELPS)的临床应用价值。方法:回顾性分析我院2005年6月至2007年1月采用腔镜筋膜外交通支离断术治疗慢性下肢静脉功能不全12例共14条肢体的临床资料。采用彩色多普勒超声、彩色多普勒剖面流速图、空气体积描记仪、临床分级和静脉功能评分等方法在手术前后对患肢静脉交通支离断情况、静脉功能和术后并发症等状况进行分析。对所有患者进行随访,分析手术的长期效果。结果:本组共离断小腿交通静脉42支,平均3支/肢体,功能不全的交通支67.4%(29/43)距内踝20cm以内;手术前后静脉功能综合评分均值、手术前后彩超剖面流速图静脉返流量均值和空气体积描记仪3项指标术前、后均值比较均有统计学差异(P<0.01)。术后并发症发生率低。随访3～15个月,随访率100%。全组浅静脉曲张未见复发,6条溃疡肢体中有5条肢体溃疡全部愈合(83.3%)。比较患者术前与术后3个月的CEAP临床评分,除色素沉着无明显改善(P>0.05)外,其他临床表现均有明显改善(P<0.01)。结论:腔镜筋膜外交通静脉离断术治疗下肢慢性静脉功能不全在临床上的结果令人满意,在目前纠正深静脉瓣膜功能方面缺乏确切疗效的治疗方法时,是具有较高临床价值的微创技术手段,值得推广。     

内镜下交通支静脉离断术治疗下肢慢性静脉病

目的　探讨内镜下交通支静脉离断术治疗下肢慢性静脉病的早期临床疗效。　方法　回顾性分析应用内镜下交通支静脉离断术治疗 2 6例 (34条肢体 )下肢慢性静脉病临床资料。　结果　每条肢体离断功能不全交通支静脉 1～ 5支 ,平均 3 5支 ,术后临床评分 (2 4 8± 0 2 5 )分较术前 (6 5 4± 0 93)分明显降低 (t=2 1 4 97,P <0 0 1 )。平均随访 1 2月 ,1 4 / 1 6条肢体(87 5 % )溃疡于术后 2 0天～ 4 5天内愈合 ,愈合后无溃疡复发。　结论　内镜下交通支静脉离断术操作简单、安全、有效 ,尤其适合静脉性溃疡患者     

浅静脉及小腿交通静脉术后深静脉血流动力学变化分析

目的检测浅静脉及交通静脉术后血流动力学变化,以分析浅静脉及交通静脉在下肢慢性静脉功能不全中的作用。方法连续追踪原发性下肢深静脉瓣膜功能不全I°-Ⅱ°患者75例 78条肢体,利用双功能超声、流速剖面图彩超技术和空气体积描记仪分别于术前、术后1、3个月及 1年进行血流动力学指标的检测并进行统计学分析。结果患肢症状完全消失88．5％(69／78)。溃疡愈合率92．8％(13／14)。全组灌注指数指标于术后1、3个月、1年均较术前显著减少(P<0．01); SEPS组,灌注指数及剩余容积分数指标于术后1、3个月、1年较术前均明显改善(P<0．01)。而术后全组静脉返流量、射血分数均值与术前比较差异无统计学意义(P>0．01)。结论浅静脉手术可有效阻断浅静脉逆向灌注;腔镜筋膜下交通静脉手术(SEPS)可显著减轻小腿的静脉性淤血,但两者均未能明显影响深静脉血流动力学状况。     

内镜下大隐静脉交通支离断术在慢性下肢静脉功能不全中的治疗价值

目的探讨内镜下大隐静脉交通支离断术在下肢慢性静脉功能不全(Chronic Venous Insufficiency,CVI)中的临床应用及治疗价值。方法2002年1月～2003年12月我院共收治下肢慢性静脉功能不全病人36例，42条肢体，均行内镜下大隐静脉交通支离断术(subfascial endoscopic perforator surgery，SEPS)，同时行股静脉瓣膜外包袖术6条.38条肢体随访，时间1～12个月，随访率90．4％。结果全组42条肢体中合并有小腿或内踝区溃疡的30条，痊愈28条，时间8～92d，痊愈率93．3％，4条下肢轻度水肿，全组无皮瓣坏死。5条肢体有疼痛：结论对于下肢慢性静脉功能不全C2-6 EpAsdpPr的病人，应用SEPS是一种较好的治疗方法。合并股静脉瓣膜关闭不全严重返流Kistner 3～4级以上的病人应当加用股静脉瓣膜外包袖术治疗。     

深静脉瓣膜修复成形术治疗下肢慢性静脉功能不全的随机对照临床研究

目的探讨深静脉瓣膜修复成形术在下肢慢性静脉功能不全治疗中的作用与疗效。方法30例双下肢慢性静脉功能不全的患者接受静脉系统手术治疗。每例2条肢体各采取不同手术方式并随机分组。1条患肢行股浅静脉外瓣膜复成形术加浅静脉手术(A组);另1条患肢仅行浅静脉手术(B组)。术后1个月和3年,利用彩超、流速剖面图彩超技术、空气体积描记仪(APG)和静脉功能不全评分等方法,比较各例2条肢体的疗效以及2组间疗效。结果全组30例患者60条肢体均为CEAP临床分级(Kistner分级)C2～C4级,经彩超和下肢静脉造影证实深静脉瓣膜功能不全返流均为Ⅲ度。术后1个月和3年随访比较,各例属于A组的患肢在静脉返流度、静脉返流量及各项指标均比属于B组患肢改善明显;A组的静脉返流量、静脉灌注指数均值与B组比较差异有统计学意义(P<0.001)。2组的静脉返流度比较差异有统计学意义(P<0.05)。3年随访时2组的射血分数和剩余容量分数均值比较差异有统计学意义(P<0.05);静脉功能不全评分均值比较差异有统计学意义(P<0.001)。结论深静脉瓣膜修复成形术可使下肢深静脉返流量明显减少,瓣膜功能明显恢复,与下肢浅静脉手术联合治疗下肢慢性静脉功能不全有更好的疗效。     

腔镜深筋膜下交通静脉离断术治疗下肢静脉性溃疡

目的:探讨腔镜深筋膜下交通静脉离断术(SEPS)治疗下肢静脉性溃疡(VLU)的临床效果。方法:回顾性分析3年半内收治的70例(76条患肢)下肢静脉功能不全患者的临床资料。按CEAP临床分类,其中C4级38例(41条患肢),C5级18例(18条患肢),C6级14例(17条患肢)。18例(18条患肢)C4级患者行大隐静脉高位结扎分段剥脱术(传统组),其余患者采用SEPS联合大隐静脉高位结扎分段剥脱术(SEPS组)。分析患肢手术前后的CEAP临床评分及患肢溃疡愈合时间和复发情况。结果:SEPS组患者术后曲张静脉团消失,患肢酸胀及沉重感逐渐减轻,局部瘙痒及创面疼痛缓解;C5级患者溃疡愈合区色素沉着及硬化明显改善,皮炎消失;C6级患者足靴区活动性溃疡在术后10~60 d(平均47.3 d)愈合;术后患肢的CEAP临床评分均低于术前(均P<0.05);平均随访15个月,无复发患者。SEPS组C4级患者与传统组患者术后各项评分均无统计学差异(均P>0.05)。结论:SEPS是治疗重度下肢静脉功能不全合并VLU的有效方法。     

SEPS联合EVLT治疗下肢重度慢性静脉功能不全

回顾性分析笔者1年余采用内镜筋膜下穿通静脉离断术（SEPS）联合静脉腔内激光术（EVLT）治疗20例下肢重度慢性静脉功能不全（CVI）（CEAP分级：C 4～C 6）患者的临床资料。结果示，联合手术成功率100%。手术后2周患者的临床症状明显缓解，患肢症状完全消失者占85.7%;12例足靴区活动性溃疡经换药后均愈合，愈合时间7～45d，平均16d。住院时间7～35d。随访1～15个月，疗效满意。 提示SEPS联合EVLT治疗重度慢性静脉功能不全是一种微创性的、安全有效的方法，能有效避免足靴区手术切口并发症，创伤小，术后恢复快。     

腘静脉外袢成形术治疗下肢静脉倒流性疾病的疗效再评价

目的再评估静脉外袢成形术治疗下肢静脉倒流性疾病的疗效。方法将重度下肢深静脉功能不全 (deepvenousinsufficiency ,DVI)患者分为肌袢组 :行静脉外袢成形术加浅静脉手术 (2 8例 2 9条肢体 ) ,浅静脉组 :仅行浅静脉手术 (46例 5 0条肢体 ) ,比较手术效果。结果肌袢组与浅静脉组在手术前后的下肢胀痛、静脉曲张均由 10 0 0 %降至 9 0 %左右 ;小腿肿胀分别由10 0 0 %和 92 0 %下降为 2 0 7%和 2 2 0 % ;术后难愈合的溃疡分别为 6 9%和 0 0 % ;3年内小腿浅静脉曲张复发率分别为 13 8%与 8 0 %。但 2组之间比较 ,差异无显著意义 (均P >0 0 5 )。结论静脉外袢成形术治疗DVI的疗效尚需进一步评价。     

经内镜结扎交通静脉治疗慢性下肢静脉性溃疡

目的 探讨内镜深筋膜下交通静脉结扎术（SEPS）治疗慢性下肢静脉性溃疡的疗效。方法 SPES治疗11例（11条）慢性下肢静脉性溃疡病人,（CEAP）分型：V型7例,Ⅵ型4例。手术方法用腹腔镜行SEPS、股浅静脉第一瓣膜缩窄术和浅静脉高位结扎术加抽剥术。结果 术后肢体症状和浅静脉曲张消失。11例溃疡均在4－6周内愈合。结论 SEPS是治疗慢性下肢静脉性溃疡的有效方法,损伤小,并发症少,溃疡愈合快,且能改善下肢外观。具有腹腔镜设备的医院都能开展该手术。     

股浅静脉瓣膜外修复成形术后血流动力学动态变化74例分析

目的检测股浅静脉瓣膜外修复成形术后血流动力学动态变化 ,以分析其治疗下肢深静脉瓣膜功能不全的疗效。方法回顾性分析原发性下肢深静脉瓣膜功能不全 74例 ( 96条肢体 )的资料 ,利用流速剖面图彩超和空气体积描记仪分别于术前、术后 1、3个月及 1年进行血流动力学指标检测并进行统计学分析。结果全组术后静脉返流量、灌注指数、静脉功能不全评分指标于术后 1、3个月、1年均较术前显著降低 (P <0 0 1)。而射血分数、剩余容积分数均值于术后 3个月、1年较术前明显改善 (P <0 0 1)。溃疡愈合率达 78 8% ( 2 6 /33) ,术后 93 6 %的肢体各种症状体征消失和明显缓解。结论股浅静脉瓣膜外修复成形术可显著改善血流动力学状况 ,对治疗原发性下肢深静脉瓣膜功能不全及静脉性溃疡有确切疗效     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

A comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

Systemic analgesia adapted to the children's condition

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.     

Intraoperative autotransfusion is associated with modest reduction of allogeneic transfusion in prosthetic hip surgery

Background: The efficacy of intraoperative salvage and washing of wound blood and the predictors of allogeneic red cell transfusions in prosthetic hip surgery are insufficiently known.
Methods: In 96 patients, undergoing primary or revision surgery, salvaged and washed red cells and, if necessary, allogeneic blood were used to keep haematocrit not lower than 33%. The bleeding of red cells during hospital stay was calculated from the red cell balance. The preoperative red cell reserve (millilitres of red cells in excess of a haematocrit of 33%) was estimated and the difference between this volume and the total bleeding of red cells was retrospectively used to classify patients with regard to the need for red cells. Stepwise regression analysis was used to define patient-related variables associated with allogeneic blood transfusion.
Results: Preoperative knowledge of the type of operation (primary, revision), the preoperative red cell reserve, and the body mass could predict roughly half of the need for banked blood (r²=0.45). Only one-third of the total bleeding of red cells was retransfused. For complete avoidance of allogeneic blood, autotransfusion was most effective in patients with a moderate need (0–4 u). However, 32% of such patients required allogeneic blood.
Conclusions: Autotransfusion has a limited efficacy to decrease the need for allogeneic blood, and other blood-saving methods should be added for this purpose. It is difficult to predict the need for allogeneic blood preoperatively.     

缺氧对肾小管上皮细胞分泌外泌体的影响

目的    观察缺氧对肾小管上皮细胞分泌外泌体的影响,探讨外泌体在缺氧致肾脏损伤中的作用及机制。 方法    （1）常氧（21% O₂）及缺氧（1% O₂）分别处理大鼠肾小管上皮细胞（NRK-52E）48 h,收集细胞上清液并使用高速梯度离心法分离外泌体。采用透射电镜、纳米示踪分析、Western印迹、蛋白浓度定量鉴定并比较两组外泌体的基本特性。（2）在共培养实验中,以不同浓度（1、10、50、100、300 mg/L）的常氧外泌体、缺氧外泌体分别干预脂多糖（LPS）诱导的大鼠原代腹腔巨噬细胞,使用实时荧光定量PCR与酶联免疫吸附试验（ELISA）法分别检测巨噬细胞白细胞介素6（IL-6）、肿瘤坏死因子α（TNF-α）、诱导型氮氧化物合酶（iNOS）水平;使用Western印迹法检测巨噬细胞磷酸化（p）STAT/STAT及细胞因子信号传导抑制蛋白1（SOCS1）的蛋白表达;最后,使用实时荧光定量PCR法检测常氧外泌体与缺氧外泌体中炎性反应相关微RNA（microRNA,miR）的表达差异。 结果    （1）离心得到的囊泡具有外泌体典型的结构,粒径小于150 nm,表达外泌体标志蛋白CD63,说明分离得到外泌体。缺氧对肾小管上皮细胞分泌的外泌体形态、粒径分布比例无明显影响,但提高了外泌体的分泌量。（2）缺氧外泌体相比于常氧外泌体促进了LPS诱导的M1型巨噬细胞IL-6、TNF-α、iNOS 的表达和分泌（均P＜0.01）,同时提高STAT的磷酸化水平并减少SOCS1的蛋白表达（均P＜0.01）;对炎性反应相关microRNA检测发现缺氧外泌体中miR-155、miR-27a表达量较常氧外泌体明显升高（P＜0.05）。 结论    缺氧可改变外泌体的生物学功能,表现为协同促进LPS诱导的M1型巨噬细胞的表型转化,这可能是慢性肾脏病微炎性反应状态持续的原因之一。     

In Vitro Function and Durability Assessment of a Novel Polyurethane Heart Valve Prosthesis

Abstract While flexible-leaflet, central-flow prosthetic heart valves promise relief from anticoagulation therapy, they continue to be restricted by inadequate durability. In consequence, a novel trileaflet valve, made entirely from polyurethane, has been developed. A batch of 6 consecutively manufactured polyurethane valves was subjected to hydrodynamic function and accelerated fatigue testing. Computerized data acquisition and control systems have been introduced to improve valve testing methodologies. In terms of hydrodynamic function, the polyurethane valve demonstrates transvalvular pressure gradients similar to those for a bioprosthetic valve (Carpentier-Edwards) and levels of retrograde flow significantly less than those for either the bioprosthetic valve or a bileaflet mechanical valve (St Jude Medical). The equivalent of 10 years of cycling without failure has been exceeded by all 6 polyurethane valves in accelerated fatigue tests with 2 valves remaining intact after 674 million cycles (equivalent to approximately 17 years) in continuing tests. Highspeed photography revealed considerable differences in leaflet motion between valves cycled at accelerated and physiological rates.