体液[Ca++]o变化诱发的心脏起搏细胞兴奋节律的分叉与混沌(Chay模型)

目的探讨航天中体液电解质中[Ca++]o变化对心跳节律的影响.方法应用可兴奋性细胞离子通道最小模型-柴(Chay)模型,以心脏细胞动作电位峰-峰间期(ISI)为研究对象,调节方程中的参数Vc,(与[Ca++]o有关), 观察ISI的变化. 结果 ISI出现周期运动、混沌运动及加周期、倍周期分叉等现象,表明航天中[Ca++]o变化可能会引起心脏起搏细胞兴奋节律的变化,并进而使心跳节律发生相应变化. 结论除心脏活动的神经、体液调节因素作用以外,航天中体液[Ca++]o的变化是引起心脏起搏细胞兴奋节律改变及其心律失常的不可忽视的因素.     

高压氧直接暴露下细胞内Ca2+的变化及其检测

目的 探讨直接暴露高压氧下细胞内Ｃａ＾２＋的变化规律及其相应的检测方法。方法 采用自行研制的微型细胞氧舱,结合显微荧光方法,测定共培养的内皮细胞（ＥＣ）和平滑肌细胞（ＳＭＣ）内钙浓度变化。结果 （１）细胞氧舱密闭性好,体积小,能耐受０．６ＭＰａ的压力,可在高压氧暴露下直接观测细胞钙变化。透光强度,图像不失真。（２）０．２和０．３ＭＰａ高压氧暴露下初始阶段５ｍｉｎ以内ＥＣ［Ｃａ＾２＋］ｉ和ＳＭＣ［Ｃ     

脑缺血再灌流时［~3H］－三磷酸肌醇放射活性及突触体游离Ca~（2＋）的变化

研究大鼠脑缺血再灌流时［３Ｈ］－ＩＰ３放射活性及突触体（Ｃａ２＋）ｉ的变化，结果示缺血１ｍｉｎ就启动了肌醇脂质信使系统，引起［３Ｈ］－ＩＰ３显著增高，缺血２０ｍｉｎ突触体（Ｃａ２＋）ｉ增高，且持续至再灌流７ｄ，磷脂酶Ｃ抑制剂ＰＭＳＦ治疗能显著地抑制突触体（Ｃａ２＋）ｉ的升高，减轻海马ＣＡ１区缺血性神经元损伤。     

模拟失重大鼠心肌肌浆网Ca^2＋摄取功能的变化

为研究模拟失重对大鼠心肌肌浆网Ｃａ＾２＋摄取功能的影响，采用差速离心法制备心肌肌浆网（ＣＳＲ）精制膜，测定ＣＳＲ囊泡膜各种ＡＴＰ酶活性，并用Ｍｉｌｌｉｐｏｒｅ滤过技术测定ＣＳＲ囊泡的Ｃａ＾２＋摄取功能。结果表明，４周模拟失重大鼠心肌肌浆网膜Ｃａ＾２＋，Ｍｇ＾２＋－ＡＴＰ酶活性不变，Ｃａ＾２＋－激活ＡＴＰ酶活性却较对照组降低６．８％（Ｐ＜０．０５）。模拟失重组心肌肌浆网囊泡ＡＴＰ依赖性Ｃdisplay stat     

尼莫地平对脑损伤后神经细胞钙通道和超微结构的改变

采用细胞内Ｃａ２＋荧光探针Ｆｕｒａ－２／ＡＭ检测大鼠脑损伤后神经元突触体胞浆中游离Ｃａ２＋浓度（［Ｃａ２＋］ｉ），以研究神经细胞钙通道变化，并选用Ｃａ２＋通道阻断剂尼莫地平治疗，观察神经细胞Ｃａ２＋通道变化和超微结构的改变。结果表明，脑损伤后神经细胞钙通道开放，突触体胞浆中游离［Ｃａ２＋］ｉ在伤后０．５小时即已升高为１．０９±０．０８×１０－６Ｍ／Ｌ水平（Ｐ＜０．００１），伤后６、２４、４８和７２小时，［Ｃａ２＋］ｉ持续处于１０－６Ｍ／Ｌ水平以上。同时发现神经细胞Ｃａ２＋超载时，其超微结构损害。应用尼莫地平治疗后，神经细胞胞浆游离［Ｃａ２＋］ｉ明显下降，超微结构损害显著减轻。     

中长期模拟失重大鼠骨骼肌线粒体钙含量和肌浆网Ca^2＋—A…

为探讨失重对肌肉功能的影响，观察了中长期模拟失重时大鼠骨骼肌细胞内Ｃａｗ＾２＋转运功能变化，测定了比目鱼肌，腓肠肌线粒体钙含量和肌浆网（ＳＲ）Ｃａ＾２＋－ＡＴＰａｓｅ活性。结果是悬吊１５、３０ｄ大鼠比目鱼肌和腓肠肌线粒体Ｃａ＾＋２含量增加，肌浆网Ｃａ＾２＋－ＡＴＰ酶活性降低，说明中长期模拟失重肌细胞内Ｃａ＾２＋转运功能发生了改变，这可能是影响肌肉收缩特性的因素之一。     

人参茎叶皂甙提高创伤小鼠T细胞功能的分子机制研究

目的研究人参茎叶皂甙（ＧＳＬ）提高创伤小鼠Ｔ细胞功能的分子机制。方法利用闭合性创伤小鼠模型，观察ＧＳＬ在体内外对创伤小鼠活化的Ｔ细胞白细胞介素２（ＩＬ－２）、ＩＬ－２受体α链（ＩＬ－２Ｒα）基因转录水平，ｃＡＭＰ、ｃＧＭＰ含量以及磷脂酰肌醇代谢的调节作用。结果ＧＳＬ体内应用（５０ｍｇ·ｋｇ－１·ｄ－１×４ｄ）可明显逆转创伤小鼠活化的Ｔ细胞ＩＬ－２ｍＲＮＡ、ＩＬ－２ＲαｍＲＮＡ、ＩＬ－２及ＩＬ－２Ｒα的受抑状态，降低细胞内ｃＡＭＰ含量，增加ｃＧＭＰ与三磷酸肌醇（ＩＰ３）含量，升高激离钙［Ｃａ２＋］ｉ）浓度、钙调素（ＣａＭ）、ＣａＭ依赖的蛋白激酶（ＣａＭ－ＰＫ）及蛋白激酶Ｃ（ＰＫＣ）的活性。０．１～１００μｇ／ｍｌ的ＧＳＬ在体外可升高创伤小鼠活化的Ｔ细胞ＩＬ－２ｍＲＮＡ及ＩＬ－２ＲαｍＲＮＡ水平，降低ｃＡＭＰ含量，升高ｃＧＭＰ含量、［Ｃａ２＋］ｉ浓度及ＰＫＣ活性。结论ＧＳＬ可通过调节Ｔ细胞内环核苷酸含量及促进磷脂酰肌醇代谢，进而增强创伤后活化的Ｔ细胞内ＩＬ－２及ＩＬ－２Ｒα的基因转录表达     

大鼠脑微血管内皮细胞缺氧与复给氧损伤后Ca2+和MAP2含量变化

血管内皮细胞内Ｃａ２＋升高,细胞骨架结构改变是内皮细胞通透性增加的主要原因［１］。脑微血管内皮细胞是血脑屏障的主要结构,其通透性变化代表血脑屏障通透性改变。缺氧与复给氧损伤后,脑微血管内皮细胞内Ｃａ２＋和微管连接蛋白（ｍｉｃｒｏｔｕｂｕｌｅａｓｓｏｃｉａｔｅｄｐｒｏｔｅｉｎｓ,ＭＡＰ２）变化及其在损伤过程中的作用,有待深入研究。笔者采用共聚焦激光显微镜（ＡＣＡＳ－５７０,Ｍｅｒｉｄｉａｎ公司,美国）,检测培养的脑微血管内皮细胞在缺氧与复给氧损伤后细胞内Ｃａ２＋和ＭＡＰ２含量变化,探讨Ｃａ２＋和Ｍ…     

热应激对大鼠丘脑、纹状体[Ca~(2 )]i的影响及机制

国内外的一些研究证明,运动训练后的骨骼肌细胞、缺氧后的脑细胞及高血压等疾病患者的心肌肌膜,红细胞和血管平滑肌细胞均存在细胞水平的Ｃａ２＋稳态改变。在热损伤方面,Ｍｉｋｋｅｌｓｅｎ和Ａｖｉｔｉｓｏｖａ等曾经分别报道热暴露后的人类ＨＴ－２９克隆癌细胞及骨骼肌细胞存在细胞水平的［Ｃａ２＋］ｉ及Ｃａ２＋－ＡＴＰａｓｅ的变化。用培养的心肌细胞进行热暴露实验,发现在３９～４３℃时随温度的升高,心肌［Ｃａ２＋］ｉ显著增加［１］。丘脑中下丘脑是体温调节中枢,纹状体是体温调节重要神经递质去甲肾上腺素、多巴胺的聚集…     

冷冻伤性脑水肿的发生机制及尼莫地平治疗作用的实验研究

目的研究大鼠冷冻伤性脑水肿不同时间脑组织伊文思兰（ＥＢ）、突触体内［Ｃａ２＋］ｉ及Ｃａ２＋－ＡＴＰ酶活性变化与脑含水量变化之间的规律，以探讨冷冻伤性脑水肿的发生机制和类型。方法干湿法测定脑组织水分含量，甲酰胺法测定ＥＢ含量，Ｆｕｒａ－２／ＡＭ荧光标记法测定突触体内［Ｃａ２＋］ｉ，微量定磷法测定线粒体Ｃａ２＋－ＡＴＰ酶活性。采用尼莫地平进行治疗，研究其对ＥＢ含量、［Ｃａ２＋］ｉ、Ｃａ２＋－ＡＴＰ酶活性和脑水肿的影响。结果冷冻伤后３０分钟即已发生Ｃａ２＋超载，伴随Ｃａ２＋－ＡＴＰ酶活性下降及脑组织水分含量及ＥＢ含量增加。尼莫地平治疗后ＥＢ含量和［Ｃａ２＋］ｉ明显下降，而Ｃａ２＋－ＡＴＰ酶活性明显恢复，脑水肿明显减轻。结论ＢＢＢ的通透性增加和细胞内钙通道开放，钙离子浓度超载在脑水肿的发生与发展过程中起了重要作用。冷冻伤性脑水肿在早期既有细胞毒性脑水肿，又有血管源性脑水肿，即混合性脑水肿。     

心脏临时起搏器在颅外颈动脉支架置入术中的应用观察

目的 观察心脏临时起搏器在颅外颈动脉支架围手术期防治血流动力学紊乱的有效性、安全性.方法 41例行颅外颈动脉支架术高危患者,共置入颈动脉支架47枚,术前经左侧股静脉安置心脏临时起搏器,起搏心率设定为60次/min,术中术后监测患者症状、血压心率变化、起搏器工作情况.结果 进行了球囊预扩张的25处颈动脉病变起搏器全部启动,25例患者出现一过性起搏器工作,持续工作最长时间1 d,1例伴发症状性低血压,低血压最长持续4 d.全部患者未出现相关并发症.结论 血流动力学紊乱是颅外颈动脉支架置入术围手术期常见的并发症,术前安置心脏临时起搏器可以快速、有效地纠正血流动力学紊乱,防止出现脑卒中等围手术期并发症,对于存在高危因素的患者,是值得推荐的方法.     

门控心肌显像对心脏起搏器植入早期左心室功能和结构的研究

目的 应用门控心肌显像观察心脏起搏器植入后早期患者左心室收缩功能与结构的变化.方法 患者27例,男9例,女18例,年龄(65.1±9.5)岁.其中起搏心室感知心室R波抑制型(VVI)起搏器组15例,起搏双腔感知双腔P波或R波抑制型(DDD)起搏器组12例.采用门控心肌显像方法测定患者起搏器植入前及植入后早期[随访(4.6±1.5)个月]自身心律或起搏器工作状态下左心室功能参数值:左心室射血分数(LVEF),左心室舒张末容积(EDV),左心室收缩末容积(ESV)及左心室收缩时间.按左心室室壁活动靶心图将室壁活动度分为缺损、稀疏及正常3级.植入前后相比,有下列一项即为左心室功能重构:LVEF增加或降低10%及以上,室壁活动度改变1级及以上,左心室收缩时间延长或缩短1个时间段及以上;结构重构:EDV增加或降低10%以上.结果 (1)左心室功能重构:27例患者中,26例(96.3%;VVI组15例,DDD组11例)出现功能重构.26例中6例(23.1%;VVI组4例,DDD组2例)LVEF升高,8例(30.8%;VVI组4例,DDD组4例)LVEF降低,12例(46.2%;VVI组7例,DDD组5例)LVEF无变化.(2)结构重构:27例中13例(48.1%;VVI组10例,DDD组3例)出现结构重构.13例中4例(VVI组3例,DDD组1例)LVEF升高,3例(均为VVI组患者)LVEF降低,6例(VVI组4例,DDD组2例)LVEF无变化.结论 心脏起搏器植入后早期即可发生左心室功能重构,约半数患者出现左心室结构重构.心脏永久起搏器植入在患者心脏获得电生理学益处时,可能对左心室的功能和结构带来不利影响.     

Correlations of left ventricular diastolic parameters and heart rate: assessment through right ventricular pacing

This study evaluated the correlations between left ventricular (LV) diastolic parameters assessed by equilibrium radionuclide angiography (ERNA) and heart rate (HR) through right ventricular pacing. Twelve patients with a permanent right ventricular apex pacemaker were included. Serial ERNA studies were performed under 6 sets of pacing cycle length (heart rate=52, 62, 72, 82, 92, 104 beats/min) for each patient. The left ventricular ejection fraction was 49.9%±3.1 under pacing HR of 52 bpm and 43.8 %±3.1 % under pacing HR of 104 bpm. The peak filling rate (PFR) increased very significantly with HR (r=0.98, P < 0.001). When the relative changes of end-diastolic volume were taken into account, the correlation between PFR and HR remained significant (r=0.94, P <0.001). The absolute time to PFR (TPFR) did not significantly change with HR, but the ratio of TPFR to cycle length strongly correlated with HR. Our study clearly demonstrates that the PFR assessed by ERNA increases and the TPFR occupies an increasing proportion of the cycle length as HR increases. Therefore, LV diastolic parameters should be normalized for HR in clinical applications. In particular, HR changes should be considered when LV diastolic parameters are used for the assessment of therapeutic interventions. Offprint requests to: Z.-X. He     

The effect of single engine fixed wing air transport on rate-responsive pacemakers.

BACKGROUND: Insufficient information exists about the safety of patients with accelerometer-based rate-responsive pacemakers in air transport by general aviation aircraft. METHODS: The response in pacing rate of two types of accelerometer-based rate-responsive pacemakers with data logging capabilities was studied during test flights with single engine fixed wing aircraft. Results were compared with the rate-response of these pacemakers during transportation by car and were also interpreted in respect to physiological heart rate response of aircrew during flights in single engine fixed wing aircraft. In addition, a continuous accelerometer readout was recorded during a turbulent phase of flight. This recording was used for a pacemaker-simulator experiment with maximal sensitive motion-sensor settings. RESULTS: Only a minor increase in pacing rate due to aircraft motion could be demonstrated during all phases of flight at all altitudes with the pacemakers programmed in the normal mode. This increase was of the same magnitude as induced during transport by car and would be of negligible influence on the performance of the individual pacemaker patient equipped with such a pacemaker. Moreover, simultaneous Holter monitoring of the pilots during these flights showed a similar rate-response in natural heart rate compared with the increase in pacing rate induced by aircraft motion in accelerometer-based rate-responsive pacemakers. No sensor-mediated pacemaker tachycardia was seen during any of these recordings. However, a 15% increase in pacing rate was induced by severe air turbulence. Programming the maximal sensitivity of the motion sensor into the pacemaker could, on the other hand, induce a significant increase in pacing rate as was demonstrated by the simulation experiments. CONCLUSION: These results seem to rule out potentially dangerous or adverse effects from motional or vibrational influences during transport in single engine fixed wing aircraft on accelerometer-based rate-responsive pacemakers with normal activity sensor settings.     

慢心室率心房颤动伴心力衰竭患者的起搏治疗

目的探讨提高心脏起搏频率在慢心室率心房颤动伴心力衰竭患者中的治疗价值。方法比较28例标准药物治疗的慢心室率心房颤动伴心力衰竭患者,起搏频率由60次/min提高至70次/min后临床症状、体征、心功能及心脏超声资料。结果植入VVI心脏起搏器后患者地高辛、β受体阻滞剂的服用率分别由17.9%和14.3%上升至100%和85.7%(P<0.05);提高起搏频率后所有患者临床症状、体征、心功能均有明显改善,有效率为75%;超声指标LVEF、SV、LVEDD并无明显改善(P>0.05),但CO较调整前明显增加(P<0.05)。结论70次/min心脏起搏在慢心室率心房颤动伴心力衰竭患者具有较好的治疗价值。     

Cardiac motion analysis to improve pacing site selection in CRT

RATIONALE AND OBJECTIVES: The aim of the study is to build cardiac wall motion models to characterize mechanical dyssynchrony and predict pacing sites for the left ventricle of the heart in cardiac resynchronization therapy (CRT). MATERIALS AND METHODS: Cardiac magnetic resonance imaging data from 20 patients are used, in which half have heart failure problems. We propose two spatio-temporal ventricular motion models to analyze the mechanical dyssynchrony of heart: radial motion series and wall motion series (a time series of radial length or wall thickness change). The hierarchical agglomerative clustering technique is applied to the motion series to find candidate pacing sites. All experiments are performed separately on each ventricular motion model to facilitate performance comparison among models. RESULTS: The experimental results demonstrate that the proposed methods perform as well as we expect. Our techniques not only effectively generate the candidate pacing sites list that can help guide CRT, but also derive clustering results that can distinguish the heart conditions between patients and normals perfectly to help medical diagnosis and prognosis. After comparing the results between two different ventricular motion models, the wall motion series model shows a better performance. CONCLUSION: In a traditional CRT device deployment, pacing sites are selected without efficient prediction, which runs the risk of suboptimal benefits. Our techniques can extract useful wall motion information from ventricular mechanical dyssynchrony and identify the candidate pacing sites with maximum contraction delay to assist pacemaker implantation in CRT.     

Assessment of myocardial fatty acid metabolism in atrioventricular synchronous pacing: Analysis of iodine 123-labeled beta-methyl iodophenyl pentadecanoic acid SPECT

Background  We used beta-methyl iodophenyl pentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT) to evaluate fatty acid metabolism in patients who were candidates for permanent pacemaker implantation and in patients with atrioventricular (AV) synchronous pacing. Methods and Results  We performed BMIPP SPECT studies in 66 patients with bradyarrhythmia, of whom 11 patients were candidates for permanent pacemaker implantation, 27 patients had atrial pacing (atrial sensing, inhibited mode, simple programmable [AAI]), and 28 patients had atrial synchronous ventricular inhibited pacing (ventricular pacing, 2-chamber sensing, atrial-triggered and ventricular-inhibited, multiprogrammable [VDD]) or atrial and ventricular pacing in sequence (atrial and ventricular sensing, atrial-inhibited and atrial-triggered, ventricular-inhibited, multiprogrammable [DDD]). A qualitative assessment revealed that the BMIPP uptake at the septal, inferior, and apical regions was significantly decreased in the patients with VDD/DDD compared with both the candidates for permanent pacemaker implantation and the patients with AAI. The total extent score (ES) and severity score (SS) were significantly higher in the patients with VDD/DDD than in the other 2 groups. Significant regional differences of both ES and SS values were observed at the septal and inferior regions in the patients with VDD/DDD compared with the other groups. No differences were found between the qualitative and quantitative measures of BMIPP uptake in the candidates for permanent pacemaker implantation and those in the patients with AAI. Conclusion  Our study suggests that AV synchronous right ventricular pacing resulting in the delayed conduction and depolarization of myocardial cells may directly interfere with regional cellular free fatty acid uptake and metabolism.     

Dynamic breast magnetic resonance imaging without complications in a patient with dual-chamber demand pacemaker

Mammography and ultrasound indicated a cancer of the right breast in a 77-year-old woman with a dual-chamber demand pacemaker. The patient was not pacemaker-dependent. She underwent breast 1.5T magnetic resonance imaging (MRI) (dynamic gradient echo sequence with Gd-DOTA 0.1 mmol/kg). Before the patient entered the MR room, the configuration of the device was changed (the response to magnet was switched from asynchronous to off and the rate-responsive algorithm was disabled). No relevant modifications of heart rhythm or rate were observed during the MR examination. No symptom was reported. Immediately after the examination, the pacemaker interrogation showed neither program changes nor alert warnings. MRI detected a bifocal cancer in the right breast which allowed tailored breast-conserving treatment to be initiated. Histopathology confirmed a bifocal invasive ductal carcinoma.     

Improved visualization of cardiac pacemaker lead on chest radiographs

Chest radiographs provide significant information about the pacing lead for the management and follow-up of post-cardiac pacing patients. However, the pacing lead is not always clearly visible because of cardiac insertion via the mediastinum and low contrast on the chest radiograph. We developed an image-processing technique that improves visualization of the cardiac pacing lead on chest radiographs to facilitate management after pacemaker implantation. In this study, 117 chest radiographs obtained during pacemaker follow-up were analyzed. These chest images were smoothed using a median filter, sharpened by unsharp masking, then binarized by thresholding using the moving average method. To evaluate the usefulness of these processed images, four cardiologists compared the original and processed images using the two-sample preference test. As a result, visualization of the pacing lead was significantly improved on all processed images compared with that on the original images. We conclude that this image processing technique can facilitate pacemaker management.     

Right atrial appendage pacing: radiographic considerations

Transvenous pacing accomplished from the right atrial appendage, either alone or in combination with right ventricular pacing, is becoming increasingly popular for selected patients in whom the contribution of atrial systole is advantageous. On the frontal chest radiograph, the pacemaker is seen to terminate over the right upper heart border, often seeming to turn abruptly cephalad. On the lateral radiograph, the lead follows a smooth, smooth, anterior curve in the midportion of the heart with its tip angled cephalad into the right atrial appendage. Complications associated with the use of this form of transvenous pacing are similar to those seen with other transvenous pacemakers; in addition, the catheter may be positioned inadvertently in the body of the right atrium, resulting in less effective atrial pacing.