同种主动脉瓣作为人工心瓣流体动力学特性测试标准参比瓣的研究——原位移植式安装、脉动流测试结果

本研究采用类似于临床原位移植方法,将同种动脉瓣固定在PS—1型装置的主动脉瓣位上。脉动流测试结果表明:此无结构和材料缺陷心瓣表现出理想心瓣特性:小而相对固定的瓣膜关闭容积、无舒张期泄漏、瓣环可扩张,在相对于正常成人的模拟心率和心输出量时,有效开口面积不小于其对应的肺动脉瓣环径解剖值。这是用此装置测试人工心瓣血流动力学性能的绝对标准。与在体正常值比较,测试高估收缩期跨瓣压差,瞬时最大跨瓣压差这一参数的意义值得怀疑。测试结果缺乏规律,模拟左室压力波形与病理波形一致,表明采用同种主动脉瓣作为人工心瓣脉动流测试的标准参比尚需进一步研究。     

同种主动脉瓣作为人工心瓣流体动力学特性测试标准参比…

本研究采用类似于临床原位移植方法，将同种动脉瓣固定在ＰＳ－１型装置的主动脉瓣位上。脉动流测试结果表明：此无结构和材料缺陷心瓣表现出理想心瓣特性：小而相对固定的瓣膜关闭容积，无舒张期泄漏，瓣环可扩张，在相对于正常成人的模拟心率和心输出量时，有效开口面积不小于其对应的肺动脉瓣环径解剖值。这是用此装置测试人工心瓣血流动力学性能的绝对标准。与在体正常值比较，测试高估收缩期跨瓣压差，瞬时最大跨瓣压差这一参数     

新鲜主动脉瓣与肺动脉瓣的解剖学观测及其临床意义

目的：从解剖学方面为自体肺动脉瓣替换主动脉瓣手术提供理论依据。方法：对１１例正常国人新鲜心脏标本的主、肺动脉瓣进行解剖学测量,并对结果进行对比研究。结果：①肺动脉瓣所能承受的压力虽小于主动脉瓣所能承受的压力,但其最小值（２８ｋＰａ）高于正常人体动脉压;②肺动脉瓣及肺动脉窦的各项测量数值均略大于主动脉瓣及主动脉窦,但无统计学意义（Ｐ＞０．０５）。结论：①肺动脉瓣能承受主动脉瓣位置的压力;②主、肺动脉瓣叶及主、肺动脉窦在形态、大小上是匹配的。     

二维超声非侵入性估测跨室间隔压力比(英文)

本文报告一个二维超声心动图测定的左室收缩期循环指数(LVSCI)用以估测跨室间隔压力比的新方法。LVSCI(或LVDCI)=4π(LV面积)×100/(LV周长)~ 2。选择30例无心肺血管疾病的儿童作为正常对照组。患病组为44例先心病儿童(年龄6—19岁,平均12.5岁),全部均经导管或手术中测压,并将其分为4个临床组:1组跨室间隔压力比(RVP/LVP)≥0.4、2组:RVP/LVP(右室压/左室压)为0.41～0.70。3组:RVP/LVP(0.71～1.2),4组RVP/LVP>1.2。选用左室短轴乳头肌及二尖瓣水平切面,结果示:正常组LVSC值均大于93％,平均96％。患病组RVP/LVP同LVSCI呈显著负相关直线关系;回归方程为:RVP/LVP=2.65-0.03LVSCI,r=-0.88,SEE=0.42,P<0.001。如果将RVP/LVP>1.2者除外(该组临床中少见)则RVP/LVP=2.36-0.224 LVSCI、r=-0.87 SEE=0.14,P<0.001,总之LVSCI能区分正常人和先心病者RVP/LVP的轻、中、重度升高,且不受年龄和身体大小等因素的影响。     

卡托普利对压力负荷增加大鼠左室心肌局部血管紧张素Ⅱ水平的影响

目的:观察卡托普利对压力负荷增加大鼠左室心肌局部血管紧张素Ⅱ(AngⅡ)水平的影响,探讨卡托普利逆转左室重构的可能机制。方法:采用[左室重量(mg)/体重(g)]计算左室重量指数,用光镜观察HE染色左室心肌病理形态,电镜观察左室心肌细胞超微结构,并采用放射免疫分析法测定左室心肌局部AngⅡ水平。结果:模型组LVMI、左室心肌组织AngⅡ水平较假手术组显著升高,卡托普利组明显低于模型组(P<0.01);光镜下左室心肌病理形态HE染色假手术组心肌纤维排列整齐,心肌细胞大小正常。模型组心肌纤维排列紊乱,细胞横径稍大,卡托普利组的改变接近假手术组。电镜下左室心肌细胞超微结构假手术组基本正常,模型组线粒体变性,表现为线粒体脊减少、断裂,基质密度变浅;肌浆网扩张;肌原纤维变性,表现为肌原纤维断裂及排列紊乱;细胞核边缘不规则,染色质边移。卡托普利组心肌细胞超微结构基本接近正常。结论:卡托普利可能通过降低压力负荷增加大鼠左室心肌局部AngⅡ水平,逆转左室重构。     

自体心包补片修补主动脉瓣环辅助主动脉瓣置换

背景：在主动脉置换过程中常遇到瓣环钙化、瓣周囊肿等特殊情况,这时一般应用特殊技术辅助主动脉瓣置换。 目的：观察自体心包补片修补主动脉瓣环辅助主动脉瓣置换治疗钙化性主动脉瓣狭窄并瓣环钙化的临床可行性。 方法：回顾性分析2009年1月至 2012年1月郑州大学第一附属医院42例钙化性主动脉瓣狭窄并瓣环钙化患者的临床资料,并通过统计学软件处理自体心包补片修补主动脉瓣环技术辅助主动脉瓣置换前后的主动脉瓣有效瓣口面积指数、最大跨瓣压差、血流峰值速度、左室射血分数等数据,分析自体心包补片修补主动脉瓣环技术辅助主动脉瓣置换的应用效果。 结果与结论：无置换中死亡病例,置换中主动脉阻断时间为52-88(63.0±18.1) min,体外循环时间为78-122(102.6±25.1) min,置换后1例患者出现急性肾功能衰竭,经床旁血透治疗后治愈。余患者无严重置换并发症。置换后住院天数为7-20(13.6±5.5) d。置换后多普勒超声心动图示：瓣膜功能良好,均未发现主动脉瓣周漏。置换后6个月的主动脉瓣有效瓣口面积指数、最大跨瓣压差、血流峰值速度、左室射血分数均有显著改善,与置换前比较差异均有显著性意义(P < 0.05)。证实对置换适应证合适的特殊换瓣患者,自体心包补片修补主动脉瓣环辅助主动脉瓣置换可取得满意的外科治疗效果,且操作安全简单,是一项可行的技术。     

David手术在主动脉根部瘤合并主动脉瓣二叶畸形治疗中的应用

目的 探讨David手术在治疗主动脉根部瘤合并主动脉瓣二叶畸形中应用的临床效果。方法 回顾性研究。纳入南京大学医学院附属鼓楼医院心胸外科2016年1月—2019年1月行David手术治疗主动脉根部瘤合并主动脉瓣二叶畸形的11例患者临床资料。其中男8例、女3例,年龄18～60(35±13)岁;主动脉瓣轻度反流7例、轻中度反流4例,心功能Ⅱ级5例、Ⅲ级5例、Ⅳ级1例。观察患者围术期指标;术后定期复查心脏超声,观察人工血管通畅情况及主动脉瓣反流情况,包括左室射血分数、主动脉瓣反流程度、平均跨瓣压差、峰值跨瓣压差及最大血流速度。结果 11例患者均成功实施手术。围术期观察指标:体外循环时间(246.1±27.2)min,主动脉阻断时间(207.5±21.5)min,术后机械通气时间4.5(3.25,9.25)h,重症监护时间(2.8±1.5)d,术后24 h引流量(418.2±299.0)mL。所有患者术后随访18~30个月,平均22.5个月,未见死亡及二次手术病例。随访期间心脏超声显示患者人工血管血流均通畅,主动脉瓣轻微反流8例、轻度反流3例,平均跨瓣压差均＜10 mmHg(1 mmHg=0.133 kPa),末次随访时,患者心功能Ⅰ级8例、Ⅱ级3例,较术前明显改善。结论 采用David手术结合主动脉瓣修复技术治疗主动脉根部瘤合并中度以下反流的主动脉瓣二叶畸形,其临床疗效满意。     

平板运动试验评价国产C-L Ⅲ型短柱瓣术后远期的跨瓣压差

目的采用平板运动试验评价国产C-LⅢ型短柱瓣术后远期的跨瓣压差。方法随机选择10例单纯主动脉瓣置换术后10年以上的患者,型号均为21mm,分为2组,其中5例置换C-LⅢ型短柱瓣,5例置换进口Medtronic-Hall侧倾碟瓣,采用彩色多普勒超声心动图记录患者平板运动试验前、后的跨瓣压差,比较两组静息和运动状态下的心率、血压及跨瓣压差。结果在静息状态下,C-LⅢ型短柱瓣组和Medtronic-Hall侧倾碟瓣组的最大跨瓣压差分别为(1.57±0.46)kPa[(11.77±3.45)mmHg]和(1.33±0.47)kPa[(9.88±3.56)mmHg],平均跨瓣压差分别为(0.88±0.32)kPa[(6.64±2.44)mmHg]和(0.73±0.35)kPa[(5.45±2.64)mmHg];运动第Ⅳ阶段后C-LⅢ型短柱瓣组和Medtronic-Hall侧倾碟瓣组的最大跨瓣压差分别为(2.99±0.86)kPa[(22.48±6.45)mmHg]和(2.57±0.65)kPa[(19.32±4.88)mmHg],平均跨瓣压差分别为(2.09±0.56)kPa[(15.66±4.23)mmHg]和(1.79±0.70)kPa[(13.43±5.23)mmHg]。统计学检验结果显示:运动第Ⅳ阶段后国产C-LⅢ型短柱瓣组的跨瓣压差明显升高,与安静状态相比有统计学意义(P<0.05);但与运动第Ⅳ阶段后Medtronic-Hall侧倾碟瓣组的跨瓣压差相比无统计学意义(P>0.05)。结论中度体力活动会引起国产C-LⅢ型短柱瓣主动脉瓣置换术后远期跨瓣压差升高,但仍在可接受的范围内,且与Medtronic-Hall侧倾碟瓣有类似的血液动力学表现,所以仍是瓣膜置换时的一个可靠选择。     

小主动脉瓣环188例患者人工机械瓣换瓣术后疗效观察

目的回顾性分析188例成年人小主动脉瓣环(瓣环直径≤21 mm)人工机械瓣膜置换术后患者的疗效及心功能的变化,探讨3种机械瓣替换术后是否存在植入瓣膜与患者不匹配(PPM)现象。方法选择南京中医药大学附属医院心胸外科188例植入小主动脉瓣环(直径16~21 mm)成年患者(占所有主动脉瓣置换患者的45.83%),其中男性96例,女性92例;年龄17~72岁,平均年龄51.12岁。主动脉瓣二叶畸形10例,单纯主动脉瓣狭窄27例,单纯主动脉瓣关闭不全46例,二尖瓣联合主动脉瓣病变96例,感染性心内膜炎9例;其中20例置换17 mm SJ Regent机械瓣,45例置换19 mm SJ Regent机械瓣,30例置换21 mm SJ Regent机械瓣,31例置换Carbio-S 19 mm机械瓣,20例置换Carbio-S21 mm机械瓣,10例置换16 mm over-line Sorin机械瓣,16例置换18 mm over-line Sorin机械瓣,16例置换20 mm overline Sorin机械瓣。采用彩色多普勒超声心动图分别于术前、术后1周、术后3个月和1年,检测患者的左心室舒张末期内径、收缩末期内径、室间隔及左心室后壁厚度、左心室射血分数(LVEF)、左心室短轴缩短率(LVFS)和主动脉瓣跨瓣压差的变化,观察左心室质量指数变化情况,并进行各组比较分析。结果全组患者无手术死亡,围术期死亡2例,术后1年内不明原因猝死3例,其余183例患者均随访1年以上。参考各瓣膜厂家提供的有效瓣口面积指数(EOAI),该研究组无重度PPM,所有患者EOAI均大于0.65 cm~2/m~2,EOAI在0.65~0.85 cm~2/m~2(中度PPM)患者占35.14%,EOAI0.85 cm~2/m~2占64.86%,EOAI与主动脉瓣跨瓣压差之间无明显相关性;术后所有患者心功能均较术前提高2~3级。术后3个月至1年内平均LVEF和LVFS均在正常范围。术后各组患者3个月至1年左心室平均内径均恢复至正常范围。术后1周平均左心室质量指数为90.35 g/m~2,较术前(101.48 g/m~2)下降显著(P0.05),随访3个月到1年无显著变化;所有患者术后1周~1年内主动脉瓣跨瓣平均压差2.92 k Pa(21.92 mm Hg),各组患者术后1周随访至术后1年,主动脉瓣跨瓣压差均无显著变化。5组患者(16 mm over-line Sorin机械瓣组、20 mm over-line Sorin机械瓣组、17 mm SJ Regent机械瓣组、Carbio-S 19 mm机械瓣组、Carbio-S 21 mm机械瓣组)术后1年内主动脉瓣跨瓣压差与其他3组相比明显增大,组间差异有统计学意义(P0.05);其中16 mm over-line Sorin机械瓣组跨瓣压差最大。所有患者均未发现有PPM现象发生。结论采用中国市场上来自不同厂家的各种直径的主动脉瓣机械瓣膜置换术后未见明显PPM现象,左心室质量指数及主动脉跨瓣压差术后均在比较理想的范围;不同厂家的各种型号的人工主动脉机械瓣可以满足绝大多数成年小主动脉瓣环患者主动脉瓣置换的需求,大部分患者无须行主动脉瓣环扩大术或采用其他术式。     

个体化治疗预防小主动脉瓣环瓣膜置换后瓣膜与患者的不匹配

背景：小主动脉瓣环主动脉瓣置换是心外科手术的难点,治疗不当可能出现瓣膜与患者不匹配现象,使左室流出道狭窄、跨瓣压差增大,引起左室后负荷增加致心肌肥厚甚至充血性心力衰竭。 目的：总结预防小主动脉瓣环瓣膜置换后发生人工心脏瓣膜与患者不匹配的治疗策略。 方法：小主动脉瓣环均主动脉瓣置换患者85例。瓣口直径>17 mm,≤19 mm的患者,选19 mm SJM Regent 瓣;对瓣口直径≤17 mm的患者,用牛心包补片加宽瓣环,再选19 mm SJM Regent 瓣行瓣膜置换;对于瓣口直径>19 mm,≤21 mm,选21 mm Hancock II ultra生物瓣置换。治疗后应用超声心动图测量有效瓣口面积指数、左心室重量指数、室间隔厚度、左心室后壁厚度、跨瓣峰速、跨瓣压差和跨瓣平均压。出院后通过门诊对患者进行随访,定期复查超声心动图。 结果与结论：治疗后早期无死亡病例,均治愈出院。随访时间为6个月-3年。主要并发症为低心排综合征2例、二次开胸止血1例、呼吸机依赖2例。所以患者均未出现脑栓塞或脑出血等脑部并发症。无瓣膜功能失调或卡瓣。未发现牛心包补片撕裂、瘤样膨出、钙化、血栓形成、免疫反应和感染等情况。81例获随访,随访率为 95%(81/85)。NYHA心功能分级Ⅰ级65例,Ⅱ级16例。各不同瓣环直径患者治疗后跨主动脉瓣峰速和平均压差均明显降低,有效瓣口面积指数明显增加,左心室重量指数、室间隔厚度和左心室后壁厚度均明显降低,均未出现人工心脏瓣膜与患者不匹配。置换21 mm Hancock II ultra 生物瓣和21 mm SJM Regent 瓣组间的比较,前者获得了更好的跨瓣峰速和平均压差,以及更好的左心室重塑指标。19 mm Regent 瓣患者治疗后体质量和体表面积较治疗前明显增加。结果提示对于小主动脉瓣环的患者应采取个体化的治疗策略预防主动脉瓣置换后瓣膜与患者不匹配的发生。 中国组织工程研究杂志出版内容重点：肾移植;肝移植;移植;心脏移植;组织移植;皮肤移植;皮瓣移植;血管移植;器官移植;组织工程全文链接：     

左心循环系统的建模与仿真

将左心模型与四元件的动脉系统Windkessel模型耦合,构成左心-动脉系统交互的左心循环系统模型.模型包括左心房、左心室、二尖瓣、动脉辩和动脉系统,实现了对左心循环系统的血流动力学模拟.应用状态空间法和SIMULINK框图模型法两种技术和MATLAB工具,进行了数学建模和数值计算,具有模型直观、容易实现、方便调节参数等优点.应用这一仿真模型,可以对左心室容积、血压及主动脉血压和血流等进行动态模拟.仿真结果与生理实际情况相符.     

应用于零维左心血液循环的二尖瓣模型的研究

提出一个可以准确合理地模拟二尖瓣动力学特性的瓣叶运动流阻模型。考虑影响二尖瓣瓣叶运动的跨瓣压差和血流推力,建立二尖瓣运动的控制方程,提出依赖于瓣叶打开角度θ的瓣叶运动流阻模型,把该模型应用于零维左心血液循环系统,得到血液动力学特性。在保持心输出量和反流分数一致的条件下,比较该模型、瞬态关闭的阶梯流阻模型和经验指定的时变流阻模型。结果发现,瓣叶运动流阻模型能反映瓣膜关闭过程中的血液动力学,如压差和流量的滞后性以及关闭流量,同时该模型可以通过调整单位转动惯量跨瓣压差影响系数K_p和血流影响系数K_b的大小,改变瓣膜打开过程和关闭过程所需时间,瓣膜打开和关闭时间分别为50.0和40.2 ms。该模型可弥补阶梯流阻模型中忽略瓣膜运动过程的瞬态关闭的缺点,同时也能避免时变流阻模型中关闭起始时间的不合理性。此模型较为合理准确地模拟二尖瓣关闭过程的动力学特性,且简单易控制。     

Left ventricular outflow tract obstruction associated with chronic ventricular assist device support

Favorable long-term patient outcome after insertion of a left ventricular assist device (LVAD) as a bridge to recovery or destination therapy for the treatment of end-stage cardiomyopathy is adversely affected by pathophysiologic changes affecting the heart. Alterations in the native aortic valve apparatus, specifically aortic valve cusp fusion, is an example of such a phenomenon and may especially affect patients in cases of bridge to recovery, a rare but reported event. A retrospective review of the last 33 LVAD placements at our institution was conducted, including reviews of operative reports and pathologic examinations of the native hearts. Seven hearts were found to have varying degrees of aortic valve cusp fusion after chronic LVAD support (63-1, 339 days). Five of these patients had native aortic valves, and two had bioprosthetic valves. The left ventricular outflow tracts in two patients were surgically occluded at the time of LVAD insertion. Aortic valve cusp fusion occurs in roughly 25% of patients on chronic LVAD support. This phenomenon may prove to be clinically significant by creating a potential source of emboli and infection. In addition, in the case of myocardial recovery, left ventricular outflow tract obstruction could limit parallel flow and produce suprasystemic ventricular pressures that in turn would elevate left ventricular end diastolic pressures. The latter may contribute to further myocardial injury, ultimately limiting the ability of an otherwise recovered heart to be weaned from LVAD support.     

射血分数-压差比值评价伴左心功能不全的主动脉瓣狭窄程度

目的初步探讨射血分数-压差比值评价伴左心功能不全的主动脉瓣狭窄程度可行性。方法80例左心室收缩功能不全的主动脉瓣狭窄患者，其中男32例，女性48例，年龄38～85岁，平均年龄42岁。用彩色多普勒超声测量主动脉瓣口面积（AVA）、左心室射血分数（EF），Bernoulli方程计算主动脉瓣口跨瓣压差（△P），Simpson容积描记法计算射血分数压差比值即EFPR（EFPR=EF／△P），分析AVA与△P、EFPR之间的相关性；用ROC曲线比较△P、EFPR两参数评价主动脉瓣狭窄程度的敏感度和特异度。结果对主动脉瓣狭窄伴左心室收缩功能不全患者，用Simpson容积描记法计算ERPR估测AVA较Bemoulli方程计算的△P法更准确（r=0.9172对r=-0.6796，P〈0.001）；将EFPR小于1.0、△P大于10.7kda（80mmHg）来估测重度主动脉瓣狭窄伴左心功能不全时，EFPR和△uP的敏感度和特异度分别为87.5％、68.6％（P〈0.05）和98.3％、37.2％（P〈0.01），表明EFPR估测重度主动脉瓣狭窄伴左心功能不全患者的特异度及敏感度较高。结论EFPR能准确估测主动脉瓣狭窄患者主动脉瓣狭窄程度，特别对伴左心功能不全的重度主动脉瓣狭窄患者瓣膜狭窄程度的评价。EFPR较传统参数有更高敏感性和特异性。     

Fluid Mechanics of Fetal Left Ventricle During Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

In cases of fetal aortic stenosis and evolving Hypoplastic Left Heart Syndrome (feHLHS), aortic stenosis is associated with specific abnormalities such as retrograde or bidirectional systolic transverse arch flow. Many cases progressed to hypoplastic left heart syndrome (HLHS) malformation at birth, but fetal aortic valvuloplasty can prevent the progression in many cases. Since both disease and intervention involve drastic changes to the biomechanical environment, in-vivo biomechanics likely play a role in inducing and preventing disease progression. However, the fluid mechanics of feHLHS is not well-characterized. Here, we conduct patient-specific echocardiography-based flow simulations of normal and feHLHS left ventricles (LV), to understand the essential fluid dynamics distinction between the two cohorts. We found high variability across feHLHS cases, but also the following unifying features. Firstly, feHLHS diastole mitral inflow was in the form of a narrowed and fast jet that impinged onto the apical region, rather than a wide and gentle inflow in normal LVs. This was likely due to a malformed mitral valve with impaired opening dynamics. This altered inflow caused elevated vorticity dynamics and wall shear stresses (WSS) and reduced oscillatory shear index at the apical zone rather than mid-ventricle. Secondly, feHLHS LV also featured elevated systolic and diastolic energy losses, intraventricular pressure gradients, and vortex formation numbers, suggesting energy inefficiency of flow and additional burden on the LV. Thirdly, feHLHS LV had poor blood turnover, suggesting a hypoxic environment, which could be associated with endocardial fibroelastosis that is often observed in these patients.

     

Surgical repair of congenital supravalvular aortic stenosis in adult

Supravalvular aortic stenosis is a rare congenital cardiac anomaly occurring mainly as a part of Williams-Beuren syndrome. Aortic narrowing above the level of the aortic valve causes obstruction of the left ventricular outflow tract, and a pressure gradient between the left ventricle and the aorta causes left ventricle hypertrophy. We report here a case of a 22-year-old man who underwent extended patch aortoplasty because of supravalvular aortic stenosis accompanying Williams-Beuren syndrome. He was in New York Heart Association functional class III with localized hourglass type supravalvular aortic stenosis. Related to arterial hypertension he was in a cardiac decompensation. Mean pressure gradient was 73 mm Hg and maximum gradient 104 mm Hg. Electrocardiography indicated left ventricle hypertrophy, which was also seen in x-ray, as heart enlargement. We successfully treated this patient with extended patch aortoplasty and immediate postoperative echocardiography showed reduction of gradient. Good surgical outcome of congenital supravalvular aortic stenosis in adults can be achieved with this treatment. This technique provides symmetric reconstruction of the aorta with good postoperative results and no gradient across aortic valve and aortic valve insufficiency remains, providing excellent long-term relief of localized supravalvular gradients and preservation of aortic valve competence.     

Left ventricular function in aortic valve endocarditis. Echocardiographic evaluation and comparison with findings in chronic aortic regurgitation

The value of M-mode echocardiography in assessment of left ventricular (LV) function in patients with aortic regurgitation due to aortic valve endocarditis (AVE) was studied in 12 consecutive patients and compared with the findings in 30 patients with chronic aortic regurgitation (CAR). Patients with AVE had markedly increased LV end-diastolic and end-systolic diameters, whereas fractional shortening was normal. A linear correlation was found between the LV ejection fractions calculated by echocardiography and angiography, but echocardiography markedly overestimated the ejection fractions. There was a close linear correlation between the prematurity of mitral valve closure (MVC) and LV end-diastolic pressure. Patients with CAR had lower end-diastolic pressure, similarly increased LV internal diameters and none had premature MVC. Thus, M-mode echocardiography can identify patients with premature MVC and high LV filling pressure. However, echocardiographic LV function indices based on measurement of internal dimensions overestimate the LV function and these data should be interpreted with caution.     

Vortices Formed on the Mitral Valve Tips Aid Normal Left Ventricular Filling

For the left ventricle (LV) to function as an effective pump it must be able to fill from a low left atrial pressure. However, this ability is lost in patients with heart failure. We investigated LV filling by measuring the cardiac blood flow using 2D phase contrast magnetic resonance imaging and quantified the intraventricular pressure gradients and the strength and location of vortices. In normal subjects, blood flows towards the apex prior to the mitral valve opening, and the mitral annulus moves rapidly away after the valve opens, with both effects enhancing the vortex ring at the mitral valve tips. Instead of being a passive by-product of the process as was previously believed, this ring facilitates filling by reducing convective losses and enhancing the function of the LV as a suction pump. The virtual channel thus created by the vortices may help insure efficient mass transfer for the left atrium to the LV apex. Impairment of this mechanism contributes to diastolic dysfunction, with LV filling becoming dependent on left atrial pressure, which can lead to eventual heart failure. Better understanding of the mechanics of this progression may lead to more accurate diagnosis and treatment of this disease.     

主动脉瓣狭窄对左心室血流特性的影响

基于CT断层扫描数据,对心脏左心室进行三维重构和模型优化。结合心肌壁面的运动特性,建立左心室几何模型过流边界运动的数学模型。通过水力半径表征主动脉瓣的狭窄程度,采用动网格技术研究主动脉瓣狭窄对左心室血液流动的影响。研究发现不同程度主动脉瓣狭窄时,水力半径与主动脉瓣狭窄程度负相关,出口面积减小,收缩期出口处速度与压力升高,剪切应力增加。舒张期,速度与压力出现先增大后减小的规律。当水力半径较小时,左心室瓣膜处剪切应力较大,收缩初期剪切应力最大为0.81 Pa。通过动态模拟对心脏的仿真研究,为后续心脏的研究提供重要的参考价值。     

左心室辅助装置与主动脉吻合角度对主动脉瓣膜影响的血流动力学研究

目的 探究左心室辅助装置(left ventricular assist device, LVAD)与主动脉吻合角度对主动脉瓣膜的血流动力学影响。方法 分别构建LVAD与主动脉吻合角度为45°、60°、90°的3个主动脉模型和主动脉瓣膜模型,搭建体外搏动台用于体外实验。运用粒子图像测速(particle image velocimetry, PIV)系统,选取心动周期中的3个时刻(T₁收缩峰值期,T₂瓣膜快速闭合时期和T₃舒张峰值期)探究主动脉瓣膜处血流动力学状态。结果 采用速度矢量、涡量、黏性剪切力指标评价LVAD吻合角度对主动脉瓣膜血流动力学的影响。瓣膜快速闭合时期,吻合角度增大时,瓣膜近壁面血流速度、平均涡量和最大黏性剪切力均增大。结论 吻合角度较低时,血流对主动脉瓣膜的冲击速度较小,瓣膜受到较小的剪切力,使瓣膜处于较好的血流动力学环境。研究结果为临床手术中吻合角度的选择提供参考。