50岁以上正常人左室舒张期彩色多普勒血流频谱参数变化的研究

目的探讨５０岁以上正常人左室舒张期脉冲多普勒频谱的参数变化情况。方法选择一年半时间内受检的所有５０岁以上正常人４７５例，按每１０岁为一组分４组进行分析。受检者取左侧卧位，常规显示心尖四腔心切面，取样容积置于二尖瓣尖，使声束与二尖瓣血流方向夹角＜１５°，以连续三个心动周期的平均值分别测量Ｅ峰、Ａ峰、Ｅ／Ａ及Ｅ峰减速时间并统计。结果发现Ｅ峰高于正常值低限的例数、平均Ｅ峰血流速度以及Ｅ／Ａ均随着年龄的增加而下降，Ｅ峰减速时间则随着增龄而增加。结论左室舒张期血流频谱的所有参数与年龄有显著的相关性，明显随着增龄而变化，并且有其规律性。     

Left ventricle haemodynamics and vaso-active hormones during graded supine exercise in healthy male subjects

Left ventricle systolic and diastolic functional parameters were measured by gated equilibrium radionuclide cardiography in 12 healthy men (age 33–51 years) at rest and during graded supine exercise. The leftventricle end-diastolic volume showed an initial small (11%) increase during low submaximal exercise [from mean 163 (SD 40) at rest to mean 181 (SD 48) ml], while left ventricle end-systolic volume decreased successively [from mean 59 (SD 19) to mean 39 (SD 21) ml] with increasing exercise. Stroke volume was therefore elevated at all exercise levels compared with rest [mean 104 (SD 23) ml], and the peak value [mean 128 (SD 33) ml] was found at the lowest exercise level, contributing 40% to the initial increase in cardiac output. Cardiac output increased from mean 6.2 (SD 1.4) at rest to mean 20.2 (SD 5.0) 1 · min^–1 at maximum. Left ventricle peak ejection and peak filling rates increased from mean 449 (SD 89) and mean 442 (SD 85) ml · s^–1 at rest to mean 996 (SD 227) and mean 1255 (SD 333) ml · s^–1, respectively, at maximum. The myocardium oxygen consumption, assumed to be proportional to the sum of the stroke work and the potential energy, increased fourfold, but absolute values were twice as high as expected, indicating that extrapolation from data obtained in dog hearts (as we have done) cannot be directly applied to humans. Selected vaso-active hormones were measured at all exercise intensities. Noradrenaline (NA), adrenaline (A) and angiotensin II (AII) concentrations showed a very pronounced increase at maximal exercise compared with the preceding lower intensites, while atrial natriuretic factor (ANF) and cyclic guanosinemonophosphate (cGMP) concentrations showed a more continuous increase, and dopamine (DA) remained almost unchanged. This speaks in favour of a crucial role for NA, A and AII in preserving blood pressure at maximum exercise, while DA probably has no importance for the cardiovascular homeostasis during exercise. Increases in concentrations of ANF and cGMP were highly correlated (r = 0.86). Our data supported the opinion that there is a cardiac limitation to maximal performance connected to the cardiac pumping capacity.     

Relations between vasoactive hormones and diastolic function in hypertensive uraemic patients

Background. Arterial hypertension is a significant risk factor for the high rate of cardiovascular disease in chronic uraemic (CU) patients. Any role that hypertension may play in CU patient outcomes assumes added significance. The elevation of some hormonal factors in early clinical stage could represent a valuable marker of cardiac disease in CU. Aim. This study first investigated the role of several hormones on cardiac diastolic properties in CU patients. Moreover, the study investigated the association of hypertension with both diastolic function and release of vasoactive hormones in CU patients. Results. We have reported that the early impairment of diastolic function is correlated with the elevation of both circulating plasma atrial natriuretic factor and endothelin-1 (ET-1) in hypertensive CU patients. Since the effect of ET-1 on diastolic function is still poorly understood, we have investigated also this issue. In eight additional patients with reduced E/A ratio, but without uraemia, hypertension or chronic heart failure, we have showed a high inverse correlation between the values of E/A ratio and ET-1 plasma concentrations. Conclusions. These results strongly suggest that the elevation in ET-1 levels was correlated with diastolic dysfunction in man. This phenomenon may have important pathophysiological implications suggesting the possibility of an early therapeutic approach in these patients.     

Improved diastolic function with the calcium antagonist nisoldipine (coat-core) in patients post myocardial infarction: results of the DEFIANT study

A multicentre, randomized, double-blind, placebo-controlled,parallel-group trial was undertaken in 135 patients to determinewhether 4 weeks of treatment with long-acting nisoldipine coat-core(20 mg once a day) could alter diastolic function in patientswith a recent myocardial infarction and with mild left ventriculardysfunction as indicated by a left ventricular ejection fraction50%. The primary endpoint was the change in diastolic fillingparameters assessed by Doppler and two-dimensional echocardiography. The mean time of admission to the study was 20 days (range 7–35)after myocardial infarction. Mean left ventricular ejectionfraction was 41%. The drug increased early diastolic peak velocityat the tips of the mitral leaflet by 0·06 m . s^–1(95% confidence intervals (CI): 0·01, 0·11). Thetime velocity integral was increased by 1·2 cm (95% CI:0·16, 2·27). These findings are indicative ofincreased early diastolic flow across the mitral valve. An importantdeterminant appeared to be a reduced isovolumic relaxation time(by 14·7 ms, 95% CI: -22·5, -6·9). As therewas no change in heart rate, systolic and diastolic blood pressureor cardiac output, after load reduction appeared unlikely asan explanation. Peak workload on exercise was 12 watts higherin the group on nisoldipine (95% CI: 0·8, 23·3).Thus, nisoldipine was shown to improve indices of diastolicventricular function, as well as exercise capacity, in thisgroup of patients. The observed effects of nisoldipine may reflectan anti-ischaemic effect or be due to improved relaxation ofthe myocardium.     

The radionuclide assessment of left ventricular diastolic filling: methodology and clinical significance

The radionuclide measurement of diastolic performance may provide a rapid noninvasive index available in the clinical setting. These measurements may be used to detect coronary artery disease, manifestations of hypertensive heart disease, isolated diastolic heart failure, and hypertrophic cardiomyopathy. The various radionuclide methods to measure diastolic filling are influenced by technological considerations, as well as applying the results in the appropriate clinical context. The importance of these derived measurements and how they correspond to various pathophysiological presentations will be discussed.     

Haemodynamic Adjustments to Mental Stress in Normotensives and Subjects with Mildly Elevated Blood Pressure

Cardiac output, heart rate, stroke volume, pre-ejection period, total peripheral resistance, systolic and diastolic blood pressure, and oxygen consumption were monitored or derived in young men with mildly elevated casual blood pressures and unambiguously normotensive control subjects before, during, and after exposure to a mental arithmetic stress. Measurements were also taken while subjects underwent graded dynamic exercise. This permitted cardiac output-oxygen consumption regression equations to be calculated and, as a consequence, cardiac output during mental stress to be represented as additional cardiac output. Systolic and diastolic blood pressure were higher during all phases of the study in the mildly elevated blood pressure group. An overall groups effect during the mental stress phase of the experiment was observed for cardiac output and pre-ejection period, and the effect for stroke volume was close to significance. Significant Groups X Periods interactions were found for cardiac output and additional cardiac output, and the heart rate effect was nearly significant. Post-hoc comparisons here indicated that, in the main, group differences in these cardiac variables were more evident during the mental arithmetic stress than during the pre- and post-task baseline periods. Total peripheral resistance did not differ reliably between groups and the cardiac effects were specific to the mental stress phase of the study.     

Significance of right ventricular filling for left ventricular enddiastolic pressure-volume relationship under acute hypoxia in the dog

Summary In 14 closed-chest dogs, the significance of right ventricular filling for left ventricular enddiastolic pressure-volume relationship was investigated under acute hypoxia by means of single plane cineventriculography and simultaneous intraventricular pressure recording.Both after 5 min asphyxia (respirator switched off) (n=5) and after 3 min hypoxia (ventilation with pure N₂) (n=9), there was a significant leftward shift (p<0.005) of the left ventricular enddiastolic pressure-volume curve as compared to the control curves under normoxia. To simulate the elevated filling of the right ventricle under acute hypoxia, rapid intraventricular infusion was applier under normoxic conditions to raise right ventricular enddiastolic pressure to the same values as that measured under hypoxia. The extent of the ensuing leftward shift of the left ventricular enddiastolic pressurevolume curve was on average 60% of the shift under hypoxia in both sets of experiments. Neither the slope of the relationship between volume stiffness and enddiastolic pressure, nor the relationship between tangent elastic modulus and left ventricular wall stress, was affected by hypoxia or asphyxia.Thus, the shift of the left ventricular enddiastolic pressure-volume curve in the early stage of hypoxia is predominantly due to the influence of increased right ventricular filling. Since the increased volume of the atria under acute hypoxia limits left ventricular distensibility additionally, the changes in left ventricular enddiastolic pressure-volume relationships, observed in the early stage of hypoxia are mainly, or even entircly, the result of interaction of the various heart compartments, and not a reflection of alterations in myocardial tissue elasticity.Preliminary results were presented at the symposium on Cardiac adaptation to hemodynamic overload, training and stress in Tübingen (1983)Supported by the Deutsche Forschungsgemeinschaft     

Interactions between the putative calcium entry promotor Bay k 8644 and pressor responses produced by α-1 and α2-adrenocepter agonists in the pithed normotensive rat

Summary Interactions between the putative calcium entry promotor Bay k 8644 and both -₁ and ₁-adrenocepter mediated increases in diastolic pressure were studied in the pithed normotensive rat. The ₁-adrenocepter mediated pressor responses elicited by B-HT920, TL-99, DP-6,7-ADTN and B-HT958 were potentiated by Bay k 8644, reflected by a leftward shift and an increase in the maximum of the log dose-pressor respinse curves. The -₁-adrenocepter effects elicited by cirazoline, methoxamine, (–)-amidephrine, St 587, (–)-phenylephrine and Sgd 101/75 were less enhanced by Bay k 8644. Only a leftward shift of the dose-response curves was observed, which was most pronounced for (–)-phenylephrine and Sgd 101/75. The -₁ and ₂-adrenocepter pressor components of (–)-noradrenaline were similarly distinguished by Bay k 8644 as observed for the selective -₁ or ₂-adrenocepter agonists.Effects of Bay k 8644 on the increase in diastolic pressure mediated by B-HT 920, St 587 and cirazoline were also studied after pretreatment with the calcium entry blocker nifedipine. After additional pretreatment with nifedipine the potentiation by Bay k 8644 observed for B-HT 920 and St 587 was more pronounced. The presence of nifedipine had no effect on the interaction between Bay k 8644 and cirazoline.It is concluded that Bay k 8644 behaves as a mirror image of nifedipine. The observation that Bay k 8644 enhances ₂-adrenocepter mediated pressor effects more effectively than ₁-adrenocepter increases in diastolic pressure is in accordance with the hypothesis of the more pronounced calcium dependency of ₂-adrenocepter mediated pressor responses. The data obtained for ceptor mediated pressor responses. The data obtained for St 587 and (–)-phenylephrine are in apparent contradiction to the finding that the pressor responses to the former drug are more markedly inhibited by calcium entry blockade than those of the latter. It is suggested that St 587 employs calcium channels which are already maximally modulated and that (–)-phenylephrine makes use of calcium channels which are in a rather inactive state. The hypothesis is put forward that the intrinsic activity of ₂-adrenocepter agonists reflects their ability to bring calcium channels in an active state.     

星形胶质细胞-神经元偶联失衡在AD发生进展中的作用及益肾填髓中药的干预机制

星形胶质细胞是中枢神经系统(CNS)重要的神经细胞类型,主要发挥营养与支持作用。星形胶质细胞与神经元之间存在密切的能量与物质偶联关系,能量偶联与物质偶联两者紧密关联、交互为用。近年来大量研究显示,星形胶质细胞-神经元偶联失衡在阿尔茨海默病(AD)的发生与进展中发挥核心作用,星形胶质细胞-神经元偶联网络失衡已成为AD干预的重要靶标并受到日益关注。中医学认为,AD的主要病机是肾虚髓亏,临床常用益肾填髓中药方剂治疗AD取得较好效果。研究发现大量益肾填髓方剂对星形胶质细胞-神经元偶联失衡具有调节和保护作用,中药方剂治疗AD的益肾填髓功效可能与其调节星形胶质细胞-神经元偶联失衡有一定的内在联系。该文就星形胶质细胞-神经元偶联失衡与AD肾虚髓亏病机之间可能内在联系及益肾填精中药干预机制的研究进展做一综述。     

Association between Reduced Serum Zinc and Diastolic Dysfunction in Maintenance Hemodialysis Patients

Diastolic dysfunction is an emerging challenge among hemodialysis (HD) patients, and the associations between serum zinc with echocardiographic parameters and diastolic function remain uncertain. A total of 185 maintenance HD patients were stratified by the tertiles of serum zinc level to compare their clinical characteristics and echocardiography. Correlations of serum zinc levels with echocardiographic parameters were examined using Pearson’s analysis. Univariate and multivariate logistic regression analyses were performed to investigate the determinants of E/e’ ratio >15 and left atrial volume index (LAVI) > 34 mL/m², both indicators of diastolic dysfunction. Patients belonging to the first tertile of serum zinc level had a significantly higher E/e’ ratio and LAVI. Serum zinc levels were negatively correlated with E (r = −0.204, p = 0.005), E/e’ ratio (r = −0.217, p = 0.003), and LAVI (r = −0.197, p = 0.007). In a multivariate analysis, older age, diabetes, coronary artery disease, and lower serum zinc levels (OR = 0.974, 95% CI = 0.950–0.999, p = 0.039) were significantly associated with E/e’ ratio >15. Furthermore, diabetes and lower serum zinc levels (OR = 0.978, 95% CI = 0.958–0.999, p = 0.041) were significantly associated with LAVI >34 mL/m². Reduced serum zinc level was significantly associated with diastolic dysfunction among HD patients. Further prospective studies are warranted to investigate whether zinc supplementation can attenuate cardiac dysfunction in maintenance HD patients.