非创伤性预处理在离体心脏抗再灌注损伤中作用机制的探讨

目的:观察非创伤性肢体缺血预处理对大鼠离体再灌注心肌是否有保护作用。方法:实验采用体重(250±30)gSD雄性大鼠25只随机分成3组,在Langendorff装置上对大鼠离体心脏进行灌流。对照组(C,n=8):在灌注全程均用富氧K-H液(充以95%O₂+5%CO₂),在恒压(8.33kPa)、恒温(37℃)条件下灌注;缺氧/复氧组(A,n=8):预灌15min后,灌注心脏先全心缺血缺氧15min,随后15min复氧再灌注(37℃);非创伤性肢体缺血预处理组(N-WIP,n=9):先将大鼠双后肢捆绑5min,松开5min,反复4次后,随后的方法同R组。在相应时点分别测定冠脉流出液和心肌匀浆中超氧化物歧化酶(SOD)活性,Ca²⁺-Mg²⁺-ATP酶活性和丙二醛(MDA)含量,同时记录心肌细胞的单相动作电位(MAP)和心肌收缩张力曲线。结果:非创伤性肢体缺血预处理能使再灌注心律失常发生率显著低于A组;心肌组织中MDA含量显著低于A组,心肌组织中SOD活性显著高于A组,心肌细胞的膜电位、Ca²⁺-Mg²⁺-ATP酶活性及肌张力较稳定。结论:非创伤性肢体缺血预处理对大鼠离体再灌注心肌有明显的保护作用,可能是通过增强心肌的抗氧化能力、稳定心肌Ca²⁺-Mg²⁺-ATP酶活性和膜相结构等途径,提高心肌细胞对再灌注损伤的抵抗力。     

一枝黄花对心血管系统部分指标的影响

目的研究一枝黄花对动物心脏、血压的药理作用。方法麻醉兔试验其血压;离体蟾蜍心脏试验其心肌收缩幅度、心率、心输出量。结果一枝黄花煎剂能显著降低麻醉兔血压,抑制蟾蜍心肌收缩力,降低蟾蜍心率和心输出量。结论一枝黄花可望开发成为一种有效的降压药。     

参麦注射液对大鼠急性心肌缺血再灌注损伤的影响

目的:观察参麦注射液对大鼠急性心肌缺血再灌注损伤的影响,并探讨其作用机制。方法:结扎冠状动脉左前降支10min再灌15min复制大鼠急性心肌缺血再灌注损伤模型,描记标准肢体Ⅱ导联心电图,测定心肌组织匀浆中超氧化物歧化酶(SOD)、Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶活性及丙二醛(MDA)含量,电镜观察心肌线粒体改变。结果:参麦注射液使再灌注性心律失常的发生率低于模型组、持续时间较短,心肌组织匀浆中SOD、Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶的活性高于模型组,MDA的含量低于模型组,心肌线粒体损伤轻于模型组。结论:参麦注射液对大鼠急性心肌缺血再灌注损伤有明显的防治作用,其机制与减轻氧自由基及钙超载损伤有关。     

丹冰通颗粒对心肌缺血的保护作用

目的探讨丹冰通颗粒治疗心肌缺血的保护作用。方法采用异丙肾上腺素致大鼠心肌缺血实验模型,检测心电图ST段、心肌丙二醛(MDA)、超氧化物歧化酶(SOD)和乳酸脱氢酶(LDH)的含量;采用垂体后叶素致大鼠心肌缺血实验模型,检测对T波的影响,并检测离体大鼠心脏冠脉流量。结果丹冰通颗粒能明显抑制异丙肾上腺素所致的心肌缺血大鼠心电图ST段偏移,使血清LDH活性和MDA含量降低,SOD活性增高(P0.05)。丹冰通颗粒能明显抑制垂体后叶素所致的心肌缺血大鼠心电图T波高度的变化,可明显增加离体大鼠心脏冠脉流量。结论丹冰通颗粒对心肌缺血具有保护作用。     

法半夏对离体蟾蜍心功能的研究

目的:观察法半夏悬浊液对离体蟾蜍心脏的心率和心肌收缩力的影响。方法:根据斯氏蛙心插管的方法,用0.033g·ml~(-1)、0.067g·ml~(-1)、0.133g·ml~(-1)和0.267g·ml~(-1)的法半夏悬浊液对离体蟾蜍心脏灌流,采用BL-420生物实验系统记录心率和心肌收缩力的变化。结果:灌注0.033g·ml~(-1)的法半夏悬浊液对离体蟾蜍心的收缩力和心率影响不大;分别灌注0.067g·ml~(-1)、0.133g·ml~(-1)和0.267g·ml~(-1)的法半夏悬浊液,离体蟾蜍心收缩力明显增强,心率减慢(P0.05)。结论:法半夏可以增强离体蟾蜍心的收缩力,对其心率影响不大。     

纳洛酮对急性冠脉闭塞后家兔心功能的影响及其机制的研究

本实验观察了阿片受体拮抗剂纳洛酮对急性冠脉闭塞家免心肌舒缩性能的影响以及这种影响和肾上腺素能β受体的关系。结果表明:在家兔急性冠脉闭塞早期,纳洛酮可显著增强心肌舒缩性能,改善心功能;β受体阻滞剂心得安可取消纳洛酮的这种作用。说明纳洛酮增强急性冠脉闭塞家兔心肌舒缩性能的作用与肾上腺表能神经活动密切相关。     

慢性高输出量型心功能不全发展过程中心室舒、缩功能和顺应性的变化及其与心泵功能的关系

本文研究了大鼠慢性高输出量型心功能不全发展过程中心室舒,缩功能和顺应性的变化规律及其与心泵功能的关系。疾病模型采用动静脉造瘘(ACF)加单侧肾动脉缩窄(RAS)的方法建立。本实验中,全部ACF+RAS大鼠均呈现出慢性高输出量型心功能不全的特征,在静息状态下心脏指数(CI)显著升高,而心泵贮备功能(CORF)却不同程度地降低。结果表明:随心泵功能的恶化,心室的舒、缩功能进行性降低,心室的舒张顺应性显著升高,心室的舒,缩性能和顺应性在心功能不全发展的不同阶段对心泵功能所起的作用不同。     

QT 间期对RR 间期变化的响应及HRV 与QTV 的关联性分析

体表心电图作为无创和连续的监测手段,在心脏安全评测方面具有重要而不可替代的位置。心电图中的间期时间序列包含着重要信息,其中以反映心动周期的RR间期序列,以及以QT间期为代表的反映心室复极化时程的间期序列,在临床上最为基础,相关的研究具有更为重要的意义。文中从应用基础研究的角度,就QT间期对于RR间期变化的响应,以及心率变异性（HRV）和QT间期变异性（QTV）关联性分析,分别介绍了其分析方法和研究进展,并且展望了可能的应用前景。     

五淋丸对大鼠异丙肾上腺素性缺血心肌的保护作用及其机制探讨

目的：观察五淋丸对异丙肾上腺素（Iso）诱发的大鼠心肌缺血的保护作用。方法：采用腹腔注射诱导大鼠致急性心肌缺血的动物模型。实验大鼠随机分为Iso模型组，阳性对照组和五淋丸大、中、小剂量组，观察各组大鼠心电图ST-iunction（J点）的位移、血清酶及血流动力学变化。结果：五淋丸大、中、小剂量组大鼠心电图J点的位移明显低于模型组（P〈O．05或P〈0．01）；血清肌酸激酶（（K）及乳酸脱氢酶（LDH）活性低于模型组（P〈O．01）；血流动力学指标：左心室收缩压（LVSP）、左心室舒张末压（LVEDP）、左心室等容期压力最大变化速率（土dp／dtmax）显著高于模型组（P〈O．05或P〈0．01）。结论：五淋丸对异丙肾上腺素所致大鼠缺血心肌具有保护作用，其机制可能与其改善心肌缺血大鼠心脏的舒缩功能有关。     

氟烷和七氟醚对缺血心肌功能和代谢及Ca2+-ATP酶活性的影响

目的: 研究氟烷、七氟醚(1.5MAC)对缺血心肌的影响。方法: 应用离体大鼠心脏Langendorff逆行灌注模型研究氟烷、七氟醚对心肌缺血前心率(HR)、左室舒张末期压力(LVEDP)、左室发展压(LVDP)、左室压力升高速率(+dp/dt)、左室压力下降速率(-dp/dt)和冠脉流量(CF)的影响,测定缺血前、缺血10min、缺血25min3个不同时间的心肌ATP含量、Ca²⁺-ATP酶活性,同时记录缺血间期左室内压的变化情况。结果: 七氟醚显著增加正常离体心脏的CF,氟烷、七氟醚均不同程度地抑制心肌收缩功能和Ca²⁺-ATP酶活性,能够增加正常心肌的能量贮备。缺血10min时,二药能够减缓心肌ATP含量及Ca²⁺-ATP酶活性的下降,氟烷的作用比较明显。缺血间期,氟烷明显推迟缺血性挛缩的起始时间,降低挛缩幅度。结论: 氟烷的抗缺血损伤作用优于七氟醚,延缓缺血期心肌ATP含量及Ca²⁺-ATP酶活性的下降可能是氟烷抗缺血损伤作用的重要机制之一。     

Arousal in obstructive sleep apnoea patients is associated with ECG RR and QT interval shortening and PR interval lengthening

Sudden cardiac death appears to be more prevalent during the normal sleeping hours in obstructive sleep apnoea (OSA) patients compared with the general population as well as to cardiovascular disease patients. The reasons for this remain unclear, but there are three likely main contributors to nocturnal death in OSA patients; cardiac arrhythmias, stroke/ruptured cerebral aneurism and myocardial infarction. Particularly marked cardiovascular system activation with arousal may play a role in initiating sudden adverse cardiovascular events in OSA. The purpose of this study was to investigate cardiac RR, QT and PR interval changes in the electrocardiogram (ECG) associated with spontaneous and respiratory-related arousals in OSA patients. A detailed observational study of ECG records obtained during conventional diagnostic sleep study with no further interventions was carried out in 20 patients (12 males, age 42.8 ± 2.1 years, body mass index 35.1 ± 1.9 kg m⁻², and respiratory disturbance index 51.8 ± 6.4 events/hour). RR and QT intervals showed significant shortening during arousals. RR interval shortening was found to be greater during respiratory arousals when compared to spontaneous arousals. PR interval showed a trend toward a greater prolongation during respiratory arousal. QT interval shortening was weakly correlated with arterial oxygen saturation levels preceding arousal. In conclusion, these data suggest that despite greater cardiac acceleration following respiratory versus spontaneous arousals from sleep, QT shortening and PR prolongation responses are similar independent of arousal type. These data support that arousals produce quite marked and differential cardiac conduction system activation in OSA and that the degree and pattern of activation may be partly influenced by the presence and severity of preceding respiratory events.     

Temporal relationship of contractility and myocardial potassium balance following beta-adrenergic stimulation of the in situ pig heart

Lower intracellular Na+ during beta-adrenergic stimulation provides an increased driving force for Na-Ca exchange, which might attenuate the inotropic response. Since (1) Na+ reduction is coupled to K+ uptake, and (2) K+ uptake lags behind the positive inotropic response to isoproterenol, we could examine the effect of Na-Ca exchange by comparing cardiac contractility and K+ balance following intracoronary isoproterenol infusion (0.6-0.8 microgram min-1). In 8 open-chest pigs, potassium concentrations were continuously measured by PVC-valinomycin mini-electrodes in arterial blood (a), and in myocardial venous blood in a shunt from the coronary sinus (cs) to the right atrium. Shunt flow, aortic flow, a left ventricular segment length and left ventricular pressure (LVP) were also continuously recorded. 64 (41-85)% (median and 95% confidence interval) of the LV dP/dt increase occurred within 1 min; thereafter contractility rose slowly. During the first minute of isoproterenol infusion, there was a small net myocardial K+ release, which then reversed to K+ accumulation. A maximum a-cs K+ concentration difference of 0.20 (0.09-0.39) mM occurred at 3.0 (2.0-4.25) min, falling to 0.05 (0.01-0.10) mM after 6.5 (3.75-8.75) min, at which point accumulated myocardial K+ uptake was 135 (27-219) mumol 100 g-1. Heart rate remained unchanged and intramural ECG indicated no sign of ischemia during the first 1.5 min of isoproterenol infusion. At 6.25 (5.0-8.0) min after stop of isoproterenol, LV dP/dt was 12 (9-24)% lower than before infusion (P less than 0.02) whereas myocardial K+ content remained higher than control. Thus, the monovalent cation shift succeeding the positive inotropic response was not associated with reduced contractility, but could explain the undershoot of LV dP/dt after stopping isoproterenol.     

Electrocardiographic response to enzyme replacement therapy for Pompe disease.

PURPOSE: Electrocardiogram (ECG) abnormalities are universal in infantile Pompe disease or glycogen storage disease type II, a fatal genetic muscle disorder caused by deficiency of acid alpha-glucosidase (GAA). Hallmarks of this disease include a shortened PR interval, an increased QT dispersion (QTd), and large left ventricular (LV) voltages. We evaluated the effect of recombinant human GAA (rhGAA) enzyme replacement therapy (ERT) on these ECG parameters in patients with infantile-onset Pompe disease. METHODS: A total of 134 ECGs were evaluated from 19 patients (5 females and 14 males) with a median age of 5.5 months at the time of enrollment in open-label clinical trials exploring the safety and efficacy of ERT at a single center from 1999 to 2004. rhGAA was purified from genetically engineered Chinese hamster ovary cells overproducing GAA and infused intravenously at doses ranging from 10 mg/kg per week to 20 to 40 mg/kg every 2 weeks in patients with infantile-onset Pompe disease. The PR interval, QTd (longest to shortest QT), and LV voltage (SV1 + RV6) were blindly determined by two independent observers. RESULTS: The median follow-up period was 6 months (range 2-30 months). The PR interval lengthened from 83 (42-110) ms to 107 (95-130) ms (P < .001), and the QTd decreased from 83 (40-125) ms to 53 (20-80) ms (P = .003). There were significant decreases in LV voltage (67 [17-83] mV vs. 48 [18-77] mV, P = .03), which correlated with decrease in LV mass on two-dimensional echocardiogram. There was no evident change in the QTc interval (429 [390-480] ms vs. 413 [370-450] ms, P = not significant). CONCLUSION: rhGAA ERT for infantile Pompe disease results in an increase in PR interval and a decrease in both the QTd and the LV voltage. These results suggest that these ECG parameters may be useful markers of the severity of cardiac disease and the response to ERT treatment in patients with infantile Pompe disease.     

The effects of L-thyroxine treatment on QT dispersion in primary hypothyroidism

Hypothyroidism has various cardiovascular manifestation and exhibits electrocardiographic change. The QT dispersion on surface ECG reflects regional variations in myocardial repolarization. The effect of L-thyroxine treatment on ECG parameters, such as QT dispersion, in patients with primary hypothyroidism were investigated. This study involved 18 patients (3 men, 15 women, ages: 48+/-18 yr) with primary hypothyroidism. All patients were checked with a standard 12-lead ECG before and after L-thyroxine treatment. Various ECG parameters were then measured twice. The mean L-thyroxine treatment duration was 22+/-2.7 months. The mean thyroid-stimulating hormone levels of patients before and after therapy were 40.2+/-29.8 microU/mL, 3.6+/-4.6 microU/mL (p<0.001) and free-T4 levels were 0.44+/-0.38 ng/dL, 1.51+/-0.39 ng/dL (p<0.001). After L-thyroxine treatment, QT interval (395+/-42 vs. 380+/-24 msec, p<0.05), QTc interval (434+/-32 vs. 417+/-23 msec, p<0.05), QT dispersion (45+/-23 vs. 30+/-13 msec, p=0.008), QTc dispersion (49+/-23 vs. 32+/-14 msec, p=0.005) significantly decreased. There were no significant changes in the PR and RR intervals, as well as the QRS duration. Our findings suggest that the thyroid hormone affects ventricular inhomogenicity, and that L-thyroxine replacement therapy may reduce malignant ventricular arrhythmia and sudden cardiac death in primary hypothyroidism.     

Serial changes in QT interval during the course of acute ischemic episode: with special reference to intracoronary electrograms

The change in electrocardiogram (ECG) during percutaneous transluminal coronary angioplasty (PTCA) was investigated by recording both standard 12 lead ECG (surface ECG) and intracoronary electrogram (ic-ECG) before, during and after PTCA with right atrium pacing (80/min). During the ischemia induced by PTCA, the amplitude of QRS complex revealed an initial decrease in amplitude and later increase in ic-ECG, however, it only showed an initial decrease in surface ECG up to 5 minutes, while the QRS interval showed a significant decrease in only in ic-ECG (77 +/- 14 vs 75 +/- 13 msec). The QT interval became shorter with the increase in the duration of ischemia, the difference being statistically significant even for the initial 20 seconds of ischemia in both ic-ECG (398 +/- 27 vs 370 +/- 22) and surface ECG. In the case of acute myocardial infarction, the direction of T wave and QT interval seemed to depend on the degree of reperfusion. Hence, in patients who underwent successful reperfusion therapy the QT interval was lengthened initially and later shortened, cardiac function preserved and T wave normalized in anteroseptal myocardial infarction, while in those who had unsuccessful reperfusion the QT interval was progressively lengthened, cardiac function was not preserved well and T wave was not normalized. Therefore, in patients with a positive T wave the QT interval was shorter (382.4 +/- 42.6 vs 448.7 +/- 29.7 msec), with better fractional shortening (4.24 +/- 2.2 vs 1.95 +/- 1.2) and better left ventricular ejection fraction (68.1 +/- 6.1 vs 52.9 +/- 14.7%) than in the patients with negative T wave in lead V2 in the chronic stage.(ABSTRACT TRUNCATED AT 250 WORDS)     

QT dispersion in patients with social phobia

BACKGROUND: QT dispersion (QTd) is the maximal interlead difference in QT interval on the surface 12-lead electrocardiogram (ECG). An increase in QTd is found in various cardiac diseases and reflects cardiac autonomic imbalance. It has recently been associated with increased anxiety levels, thereby predisposing affected individuals to fatal heart disease. This is the first study to assess QTd in social phobia, as a marker of anxiety-induced cardiac dysregulation. METHODS: QTd and rate-corrected QTd were measured in 16 physically healthy and non-depressed outpatients with long-term (mean 28+/-12.2 years; age 37.9+/-9.6 years) social phobia (SP) and in 15 physically and mentally healthy age- and gender-matched controls. The Liebowitz Social Anxiety Scale (LSAS) was scored concomitantly. The intra- and inter-observer reproducibilities of QTd were highly correlated (r=0.96, P<0.001; r=0.74, P=0.002, respectively). RESULTS: QTd and rate-corrected QTd were significantly higher in the patients with SP compared to the controls (70+/-21 versus 43+/-10 ms, P<0.001 and 75+/-23 versus 46+/-10 ms, P<0.001, respectively), and highly correlated with the two LSAS subscores. CONCLUSIONS: Prolonged SP is associated with an increase in QTd. This association may result from prolonged anxiety and, in turn, a decrease in vagal modulation and/or increase in sympathetic modulation. Further large-scale epidemiological studies are needed to determine if increased QTd can serve as a trait/state marker, and if it is a risk factor for sudden cardiac death in patients with SP.     

QT interval and QT dispersion in eating disorders

BACKGROUND: Eating disorders are thought to be risk factors for cardiac sudden death secondary to arrhythmia. Results in previous studies on QT interval and QT dispersion, markers of fatal arrhythmia, have been inconsistent. METHODS: We prospectively examined 179 female eating disorder patients, being over 18 years old and diagnosed according to the DSM-IV criteria between January 1995 and December 2002, and 52 healthy women. Patients with abnormal plasma electrolytes or taking medications that might influence the electrocardiogram (ECG) were excluded from the study. QT intervals were corrected for heart rate using Bazett's formula and the nomogram method, which is more reliable at extremely low heart rates than Bazett's formula. QT dispersion was measured as the difference between the longest and shortest QT intervals. QT intervals and QT dispersion in each patient group were compared with those in the control group. RESULTS: The 164 eligible patients consisted of 43 patients with anorexia nervosa restricting type, 35 with anorexia nervosa binge eating/purging type, 63 with bulimia nervosa purging type, and 23 with bulimia nervosa non-purging type. There was no significant difference in age between eating disorder patients and controls. QT interval and QT dispersion were significantly longer in all eating disorder subtypes than in the control group. QT interval and QT dispersion were significantly correlated with the rate of body weight loss in bulimia nervosa. CONCLUSIONS: QT interval and QT dispersion were prolonged in both anorexia nervosa and bulimia nervosa. Examination of ECG in eating disorder patients without extremely low body weight also appears to be clinically important.     

New epicardial mapping electrode with warming/cooling function for experimental electrophysiology studies

Cardiac electrical activity is influenced by temperature. In experimental models, the induction of hypothermia and/or hyperthermia has been used for the study of mechanisms of cardiac arrhythmia. A system that allows for localized, controlled induction, besides simultaneously recording electrical activity in the same induced area, needs to be developed ad hoc. This article describes the construction and application of a new system capable of locally modifying the epicardial temperature of isolated hearts and of carrying out cardiac mapping with sufficient spatial resolution. The system is based on a thermoelectric refrigerator and an array of 128 stainless steel unipolar electrodes in encapsulated epoxy of good thermal conductivity. The surface of the electrode is shaped to match the ventricular curvature. The electrode-device was tested on 7 isolated perfused rabbit hearts following the Langendorff technique. Quality recordings were obtained for the left ventricle at temperatures of 37° C, 22° C and 42° C. The effects of temperature were explored in relation to two electrophysiological parameters: the QT interval during sinus rhythm and the VV interval during ventricular fibrillation. The results indicate that this is a suitable method for creating and analyzing electrophysiological heterogeneities induced by temperature in the experimental model.     

Quantification of the fetal electrocardiogram using averaging technique

A signal analysis procedure is described for obtaining time intervals parameters of the fetal electrocardiogram as recorded from the maternal abdomen. Applying averaging to the fetal electrocardiogram quantification of the PR interval, QRS duration and QT interval were measured. This technique which includes the subtraction of an averaged maternal ECG waveform using cross-correlation function and fast Fourier transform algorithm, enables the detection of all the fetal QRS complexes in spite of their coincidence with the maternal ECGs. Results that were obtained from 21 pregnant women at the gestational age of 32-41 weeks and an example of a recording with fetal premature ventricular contractions are presented. This method shows an important improvement with respect to detection of fetal heart rate and detection of arrhythmia disturbances in the fetal ECG. The averaging procedure can be used to evaluate long-lived alterations in the fetal ECG.     

Beat-to-beat QT interval variability before and after cardiac surgery

Non-uniform recovery of excitability may be essential in triggering malignant ventricular tachycardia after cardiac surgery. Thirty-five channels ECG was recorded for 6 min in 27 patients before and after heart surgery and in 20 control subjects. Off-line analysis was performed. RR interval duration, RR SD, QT SD and power spectra of RR variability were computed from 256 s stable RR and QT interval series. When compared to controls, patients had decreased RR SD and increased QT SD before surgery (p<0.002 and p<0.0005, respectively); RR SD further decreased and QT SD increased after the surgery (p<0.0001 and p<0.0002, respectively). Increase of QT variability and decrease of RR variability after cardiac surgery may reflect disrupted electrophysiological stability of the myocardium and thus electrophysiological substrate for triggering malignant arrhythmia.