自发性高血压大鼠压力反射敏感性与血压变异性的关系

目的研究自发性高血压大鼠（ＳＨＲ）动脉血压变异性（ＢＰＶ）和压力反射敏感性（ＢＲＳ）的改变及二者间相关性。方法清醒、自由活动状态下测定ＳＨＲ及对照ＷＫＹ大鼠２４小时收缩压（ＳＢＰ）、舒张压（ＤＢＰ）、心率（ＨＲ）及其各自变异性的改变；单次静脉注射去氧肾上腺素（５μｇ／ｋｇ）以测定压力反射对心率的控制功能（ＢＲＳＨＲ）；化学切除自主神经阻断压力反射传出通路后，比较静注去氧肾上腺素后的升压曲线下面积差异，测定压力反射对血压的控制功能（ＢＲＳＢＰ）。结果ＳＨＲ的血压及血压变异性显著高于ＷＫＹ大鼠，ＢＲＳ明显降低；ＢＲＳ与ＳＨＲ和ＷＫＹ大鼠的ＢＰＶ呈负相关，其中ＢＲＳＢＰ与ＢＰＶ的相关系数高于ＢＲＳＨＲ与ＢＰＶ的相关系数；ＢＲＳＨＲ或ＢＲＳＢＰ与心率及心率变异性间均无相关性。结论压力反射敏感性与血压变异性间呈负相关关系，其中ＢＲＳＢＰ为反映压力反射功能的较敏感指标。     

糖尿病心血管自主神经病变检查方法的研究进展

目前无创检测糖尿病心血管自主神经病变（DCAN）的方法有标准心血管反射试验、心率变异性（HHV）和压力反射敏感性（BRS）分析等，可用于糖尿病患者心血管自主神经功能的评估以及分析DCAN和血糖控制、肥胖、心源性猝死、颈动脉硬化、胰岛素抵抗及运动治疗等的关系。另外，影像学方法如核素显像检测也可应用于DCAN，并可提供糖尿病患者心脏失去自主神经支配的直接证据。     

急性心肌梗塞后心率变异性,压力反射敏感性的变化及其意义

本文阐述心率变异性及压力反射敏感性在预测急性心肌梗塞后心律失常事件发生中的价值，以及急性中心肌梗塞后药物治疗对心率变异性，压力反射敏感性的影响。     

糖尿病心血管自主神经病变检查方法的研究进展

目前无创检测糖尿病心血管自主神经病变(DCAN)的方法有标准心血管反射试验、心率变异性(HRV)和压力反射敏感性(BRS)分析等,可用于糖尿病患者心血管自主神经功能的评估以及分析DCAN和血糖控制、肥胖、心源性猝死、颈动脉硬化、胰岛素抵抗及运动治疗等的关系.另外,影像学方法如核素显像检测也可应用于DCAN,并可提供糖尿病患者心脏失去自主神经支配的直接证据.     

低电流针刺对轻度高血压患者的压力反射敏感性分析

目的探讨高血压患者低电流针剌后的自主神经功能状态。方法15例年龄为38-54岁的原发性高血压患者和30例血压正常对照组,接受无创伤的压力反射敏感性检测分析。结果高血压组的压力反射敏感性（BRS）和心率变异性（HRV）下降。结论高血压患者的自主神经功能明显受损,自主神经功能障碍可能在高血压发病中起重要作用,低电流针刺能改善轻度高血压患者的压力反射敏感性。     

压力感受器敏感性试验(157)

正压力感受器敏感性(baroreceptor sensitivity,BRS)或称压力反射敏感性(baroreflex sensitivity)是指动脉内血压变化反射性引起心动周期变化的敏感程度,在心动周期(RR间期)与收缩压(SBP)构成的回归曲线中,斜率大提示迷走神经反射增强,斜率小提示交感神经反射增强。而BRS试验则是测定压力感受器敏感性的检查方法。一.BRS试验的生理学基础     

外周血管病患者血液透析中的血压变异性和心血管自主神经控制功能

外周血管病(peripheral vascular disease,PVD)患者进行血液透析存在着较高的死亡风险。该研究旨在探索当透析造成血容量不足时所致的PVD与外周血管阻力控制系统改变之间的关系,探索透析诱导的脉压增加与PVD的相关性。方法:透析初始到结束连续记录血压值。患者每次透析前接受全身生物阻抗分光镜检查以评估体内水分过多的情况,然后分析其血压变异性、心率变异性和压力反射敏感性。结果:与无PVD患者相比,PVD患者外周血管局部调节表现为舒张压变异性在极低频段变异值较高,以及心脏压力感受反射减弱。     

压力反射敏感性的检测方法及临床应用

常用于自主神经功能检测指标有心率变异性及压力反射敏感性。本文详述压力反射敏感性检测方法的临床应用及其优越性。     

高血压和非高血压2型糖尿病患者心率变异性、压力反射敏感性和血压变异性频谱分析鉴定心脏自主神经病变

目的采用心率变异性（HRV）、压力反射敏感性（BRS）和血压变异性（BPV）频谱方法了解高血压和非高血压T2DM患者心血管自主神经病变的诊断价值。方法119例T2DM患者和101例非糖尿病对照者分别分为高血压（HT）和非高血压（NHT）亚组,均进行HRV、BRS和BPV检测。结果DM组中HT和NHT亚组的TV.rri、VLF.rri、LF.rri和HF．rri均显著低于对照组。DM-HT组的Total．brs和HF．brs明显下降,BPV无改变;DM-NHT组的TV．bp和VLF．bp显著增加。结论糖尿病患者（无论有无HT）HRV下降,反映基础状态下心血管自主神经功能张力异常可能不受血压影响;DM合并HT患者BRS降低,提示DM合并HT可使心血管反射调节能力减退;无高血压的DM患者BPV增大,提示DM患者血压调定和稳态早期受损。     

老年高血压病人的血流动力学变化

老年高血压的特点是收缩压的不成比例升高,因而脉压的升高超过平均动脉压的升高。在其血流动力学变化中,动脉变化起重要作用。在心功能正常或降低时,收缩压不成比例的升高是由于动脉硬化和波反射增加的结果。前者主要是中心主动脉结构改变;后者是继发于随增龄而发生的动脉系统几何学改变,这种改变造成胸主动脉波反射增加,是脉波速度增加和反射点更靠近心脏的结果。基本概念根据世界卫生组织(WHO)的标准,当收缩压(SBP)大于21.3kPa(160mmHg)伴有或     

The bradycardic agent zatebradine enhances baroreflex sensitivity and heart rate variability in rats early after myocardial infarction

OBJECTIVE: The bradycardic agent zatebradine (UL-FS 49) reduces heart rate without negative inotropic or proarrhythmic effects. The aim was to experimentally characterize the influence of zatebradine on arterial baroreflex sensitivity (BRS) and heart rate variability (HRV) which are generally considered as estimates of vagal activity and have prognostic value in patients after myocardial infarction (MI). METHODS: Conscious rats were studied 3 days after left coronary artery ligation or sham-operation (SH). BRS was determined by linear regression analysis of RR-interval and mean arterial pressure changes evoked by intravenous (i.v.) injections of methoxamine and nitroprusside. HRV at rest was calculated from high-resolution electrocardiogram-recordings. RESULTS: In MI-rats heart rate was similar to SH-rats, mean arterial pressure was lower and both BRS and HRV were markedly reduced. Zatebradine (0.5 mg/kg i.v.) reduced heart rate in MI-rats from 400 +/- 15 to 350 +/- 19 and in SH-rats from 390 +/- 19 to 324 +/- 6 beats/min without changing mean arterial pressure. Both BRS and HRV were restored in MI- and further increased in SH-rats by the drug. Effects of 0.05, 0.5 and 5 mg/kg zatebradine revealed a dose-dependency of heart rate reduction. The lowest dose enhanced reflex bradycardia despite little effect on heart rate and lack of effect on both reflex tachycardia and HRV. CONCLUSIONS: Both BRS and HRV are reduced in rats early after MI, indicating a depressed reflex and tonic vagal activity. Treatment with zatebradine enhances both BRS and HRV. These data suggest that the drug has both peripheral and central effects, leading to an increase of vagal control of heart rate.     

Relation between actual heart rate and autonomic effects of beta blockade in healthy men

This study evaluated the effect of beta blockade on cardiac autonomic control and its dependence on heart rate change. The relations between RR interval duration, heart rate variability (HRV), and baroreflex sensitivity (BRS) were studied in 111 healthy men and in 21 male volunteers before and after a 100-mg oral dose of metoprolol. HRV and BRS correlated significantly with mean RR (r = 0.39, r = 0.57). Metoprolol administration increased both mean RR (from 996 to 1,176 ms, p <0.001), BRS from 24 to 36 ms/mm Hg (p = 0.003), and the SD of RR from 61 to 74 ms (p = 0.05). However, metoprolol-induced changes of HRV and BRS became insignificant (p = 0.69 and 0.48) after they were normalized to the same cycle length, suggesting that the improvement of cardiac autonomic control after beta blockade could be explained by a change of heart rate.     

Impaired baroreflex sensitivity and cardiac autonomic functions are associated with cardiovascular disease risk factors among patients with metabolic syndrome in a tertiary care teaching hospital of South-India

Background & aimBaroreflex sensitivity (BRS) and heart rate variability (HRV) have been proposed to assess early autonomic dysfunction in metabolic syndrome (MetS) patients. Autonomic dysfunction in MetS patients may increase the risk of developing cardiovascular disease (CVD). However, the association of BRS and HRV with CVD risk factors remains elusive in MetS. The primary aim of this study was to assess the BRS and HRV in MetS patients among South-Indian adults and check whether BRS and HRV are associated with CVD risk factors.MethodsWe performed anthropometric indices, body composition, physiological parameters such as BRS, HRV, and other autonomic function tests in 176 subjects divided into MetS patients (n = 88) and healthy controls (n = 88). Fasting blood samples were collected for biochemical profiles and calculated insulin resistance indices, atherogenic index (AI), and rate pressure product (RPP).ResultsWhen compared to controls, we found significantly reduced BRS and an increased ratio of low-frequency (LF) to high-frequency (HF) power of HRV (LF/HF) in the MetS group. We observed significant differences in body composition and biochemical profiles among the MetS group. BRS and LF/HF ratio of HRV have shown a significant association with CVD risk factors in the MetS group.ConclusionsWe observed autonomic dysfunction as low BRS and high LF/HF ratio of HRV in MetS patients. Additionally, the present results emphasize that the association of BRS and LF/HF ratio with anthropometric, glucose, lipid parameters, and other CVD risk factors may increase the susceptibility of MetS patients to higher CVD risk.     

Baroreflex sensitivity, heart rate, and blood pressure variability in hypertensive pregnancy disorders

Hypertensive pregnancy disorders are a leading cause of perinatal and maternal morbidity and mortality. Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) are relevant predictors of cardiovascular risk in humans. The aim of the study was to evaluate whether HRV, BPV, and BRS differ between distinct hypertensive pregnancy disorders. Continuous heart rate and blood pressure recordings were performed in 80 healthy pregnant women as controls (CON), 19 with chronic hypertension (CH), 18 with pregnancy-induced hypertension (PIH), and 44 with pre-eclampsia (PE). The data were assessed by time and frequency domain analysis, nonlinear dynamics, and BRS. BPV is markedly altered in all three groups with hypertensive disorders compared to healthy pregnancies, whereby changes were most pronounced in PE patients. Interestingly, this increase in PE patients did not lead to elevated spontaneous baroreflex events, while BPV changes in both the other hypertensive groups were paralleled by alterations in baroreflex parameters. The HRV is unaltered in CH and PE but significantly impaired in PIH. We conclude that parameters of the HRV, BPV, and BRS differ between various hypertensive pregnancy disorders. Thus, distinct clinical manifestations of hypertension in pregnancy have different pathophysiological, regulatory, and compensatory mechanisms.     

Correlation between cardiac autonomic activity and compromise of left ventricular function in dilated cardiomyopathy

In recent years, evaluation of cardiac autonomic activity by means of heart rate variability (HRV) determination and baroreflex sensitivity (BRS) testing has become readily available. The results of the ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) study showed that both diminished HRV and baro-reflex sensitivity are associated with poor outcome in patients after myocardial infarction. In contrast to patients with coronary disease little information is available concerning cardiac autonomic activity in idiopathic dilated cardiomyopathy (IDC). Therefore, HRV and BRS were assessed in 160 patients with IDC and preserved sinus rhythm in order to investigate the relationship between HRV, BRS, and left ventricular ejection fraction. Time domain indices of HRV were computed from 24-hour digital Holter recordings. BRS testing was performed using the noninvasive phenylephrine method. Mean standard deviation of all normal RR intervals (SDNN) of the whole study population was 112 +/- 46 ms. A well preserved HRV (SDNN > 105 ms) was found in 74 patients (46%), a moderately decreased HRV (SDNN 70-105 ms) in 59 patients (37%), and a severely decreased HRV (SDNN < 70 ms) in 27 patients (17%). Mean BRS was 7.5 +/- 5.0 ms/mm Hg. A well preserved BRS (> 6 ms/mm Hg) was present in 78 patients (57%), a moderately decreased BRS (3-6 ms/mm Hg) was present in 38 patients (28%), and a severely decreased BRS (< 3 ms/mm Hg) in 21 patients (15%). There was only a weak correlation between SDNN and BRS (r = 0.19; p < 0.05). A weak correlation was found for SDNN and left ventricular ejection fraction (r = 0.29; p < 0.05). There was no significant correlation between BRS and left ventricular ejection fraction (r = 0.14). In summary, there was only a weak correlation between the HRV, BRS, and left ventricular ejection fraction in patients with IDC suggesting that these 3 variables may be independent predictors of sudden death in IDC. The relative prognostic value of these variables and other potential risk predictors including the presence of arrhythmias on Holter, microvolt T wave alternans, QTc dispersion, and signal-averaged ECG is currently under investigation in a large prospective observational study (Marburg Cardiomyopathy Study (MACAS)) during 5-year follow-up at our institution.     

心肌梗死后心率变异性,压力反射敏感性与心肌电生理特性？…

目的 探讨心率变异性（ＨＲＶ）、压力反射敏感性（ＢＲＳ）预测心肌梗死（心梗）后心脏性猝死的电生理基础。方法 ４８只心梗兔分别测量ＨＲＶ时域与频域指标,ＢＲＳ、以有效不应期离散性（ＶＥＲＰ＿Ｄ）、室颤阈值（ＶＦＴ）,各指标进行相关性分析。结果根据电刺激能否诱发心室颤动（室颤）分为室颤组（ｎ＝２５）和无室颤组（ｎ＝２３）,室颤组的心率变异系数、极低频、低频、高频、ＲＢＳ和ＶＦＴ明显降低,ＶＥＲＰ－Ｄ     

The importance of high-frequency paced breathing in spectral baroreflex sensitivity assessment

OBJECTIVE: Computation of the low-frequency (LF) blood pressure variability (BPV) to heart rate variability (HRV) transfer-index is a common method to assess baroreflex sensitivity (BRS), tacitly assuming that all LF-HRV is caused by baroreflex feedback of LF-BPV. However, respiration may also cause HRV by mechanisms not involving the baroreflex. Application of narrow-band (controlled) high-frequency breathing would keep such non-baroreflex-mediated HRV best out of the LF band. Spontaneous breathing, because of its broad-band character, might cause extra, non-baroreflex-mediated, HRV in the LF band, while paced LF breathing would even concentrate most non-baroreflex-mediated HRV in the LF band. Our study addresses the likely resulting BRS overestimation. DESIGN: We recorded HRV and BPV in 20 healthy young subjects in the sitting position. We varied the sympathovagal balance by gradual leg-lowering from horizontal till 60 degrees . At each angle the subjects performed controlled 0.10 Hz, spontaneous, and controlled 0.25 Hz respiration. RESULTS: Resting BRS values were 15.5(7.2), 13.1 (3.7), and 11.6(6.2) ms/mmHg, respectively. Both the 15/min and the free breathing values differed significantly, P< 0.01 and P= 0.04, from the 6/min breathing value. With lowered legs, the BRS values were 8.2(3.4), 8.3(2.9), and 8.3(3.4) ms/mmHg, respectively. CONCLUSION: Controlled 6/min breathing caused significant BRS overestimation under resting conditions. For the group, spontaneous respiration yielded acceptable BRS values, but individual BRS values deviated sometimes considerably. Conversely, with gravitational load, the respiratory pattern had only minor impact on BRS. Our results demonstrate that the risk of an overestimated BRS value is realistic as long as respiration is not controlled and of high-frequency.     

Reduced heart rate variability and baroreflex sensitivity in primary biliary cirrhosis.

BACKGROUND: Standardized mortality ratio for primary biliary cirrhosis (PBC) is 2.87. Even after accounting for liver and cancer-related deaths there is an unexplained excess mortality associated with PBC. We have assessed heart rate variability (HRV) and baroreflex sensitivity (BRS) risk factors associated with cardiovascular mortality, in 57 PBC patients and age- and sex-matched normal controls. METHODS: HRV and BRS were measured non-invasively in subjects and controls. Beat to beat RR interval and 'Portapres' blood pressure data were processed using power spectral analysis. Power was calculated in very low frequency (VLF), low-frequency (LF) and high-frequency (HF) bands according to international guidelines. BRS (alpha) was computed using cross-spectrum analysis. Patients also underwent fatigue severity assessment using a measure validated for use in PBC. RESULTS: PBC patients had significantly lower total HRV compared with controls (P=0.02), with the reduction occurring predominantly in the LF domain (P=0.03). BRS was also significantly reduced compared with controls (P=0.02). There were no significant differences in HRV or BRS between cirrhotic and non-cirrhotic patients. Within the PBC patient group HRV was significantly lower in fatigued than in non-fatigued patients (P<0.05). CONCLUSION: Abnormalities of HRV and BRS in PBC are not specific to advanced disease but are associated with fatigue severity. Abnormalities could be associated with increased risk of sudden cardiac death, potentially contributing to the excess mortality seen in PBC.     

Tilt table testing in childhood: improved sensitivity by non-invasive haemodynamic monitoring devices?

OBJECTIVE: Tilt table testing represents a valuable diagnostic method in suspected neurally mediated syncope. As sympathovagal imbalance and impaired baroreceptor sensitivity (BRS) have been observed in these patients, both methods were used in this study to investigate whether a combination of these parameters would improve sensitivity and whether specific patterns of neurally mediated syncopes would correspond to characteristic trends in heart rate variability (HRV) and BRS. METHODS AND RESULTS: Fifty-one pts. (29 female, mean age 14.5 +/- 3.9 y) with unexplained syncope and 15 control subjects (9 female, mean age 14.8 +/- 3.0 y) were tested following a standard tilt table test protocol. Power spectral analysis (PSA) of HRV and BRS calculation were used additionally to beat-to-beat blood pressure and ECG-monitoring. Twenty-three out of 51 pts. (45%) experienced a syncope after 18 +/- 10.2 min of tilting. In 2/23 patients (8.6%) a postural tachycardia syndrome (POTS), in 14/23 (60.8%) a neurally mediated syncope of mixed type, in 2/23 (8.6%) a vasodepressor syncope and in 5/23 (21.7%) a cardioinhibitory syncope with asystole were observed. PSA of HRV and BRS revealed a specificity, sensitivity, and positive and negative predictive values of the cut-off points in combination (LF/HF > or = 2.7 and BRS > or = 8) of 93.3%, 65.2%, 93% and 39%, respectively. CONCLUSION: In this study population, BRS and PSA of HRV were able to improve sensitivity of tilt testing after unexplained syncope. Specific BRS or HRV patterns in different mechanisms of neurally mediated syncope could not be identified possibly due to the small sample size.     

Autonomic nerve function expressed by the baroreflex sensitivity (BRS) in elderly adults

We examined 24 hour heart rate variability (HRV) components and baroreflex sensitivity (BRS) in elderly adults. Forty-eight subjects, aged 65-69 years old (24 men, 24 women) were examined in this study. BRS was measured in the morning (8:00-9:00) using noninvasive cross spectral analysis. There were significant correlations between BRS and low-frequency (LF) power (r = 0.593, p < 0.001) of HRV, and between BRS and high-frequency (HF) power (r = 0.402, p < 0.005). BRS values were lower in women compared with men (p < 0.01), and LF/HF was significantly lower in women than in men (p < 0.05).