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Baroreflex Sensitivity (baroreflex + sensitivity)

Distribution by Scientific Domains

Medical Sciences	81%
Life Sciences	15%

Distribution within Medical Sciences

Cardiovascular Disease	27%
Pharmacology & Pharmaceutical Medicine	18%
Neurology	11%

Kinds of Baroreflex Sensitivity

spontaneous baroreflex sensitivity

Selected Abstracts

Early Detection Of Diminished Baroreflex Sensitivity In Diabetic Patients Without Evidence Of Cardiovascular Autonomic Neuropathy

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 3 2000
D Ziegler
Diabetic cardiovascular autonomic neuropathy (CAN) carries an increased risk of mortality. Decreased baroreflex sensitivity (BRS) has been identified as a predictor of increased mortality following myocardial infarction. We evaluated spontaneous BRS in 39 healthy control subjects (C: age (mean ± SEM): 41.5 ± 1.9 years) and 116 diabetic patients (64% Type 1, 36% Type 2; age: 45.8 ± 1.4 years; diabetes duration: 16.9 ± 1.0 years; HbA1c: 9.2 ± 0.2%) using cross-spectral analysis between systolic blood pressure and heart rate in the low-frequency (LF) and high-frequency (HF) bands as well as time domain (sequence) analysis in the supine and standing positions over 10 min. According to previously suggested definitions based on autonomic function tests (AFTs), 36 patients had definite CAN (CAN+: 3 of 7 indices abnormal), 13 had borderline CAN (CAN[+]: 2 of 7 indices abnormal), and 64 had no evidence of CAN (CAN,: 1 of 7 indices abnormal). Maximum gain in cross-spectral LF band (standing) was significantly reduced in CAN, as compared with C (5.2 ± 0.4 vs. 7.2 ± 0.8 ms/mmHg, p < 0.05). Moreover, maximum gain in cross-spectral HF band was significantly lower in CAN, than in C (supine: 12.0 ± 1.2 vs. 17.9 ± 2.5 ms/mmHg, p < 0.05; standing: 4.9 ± 0.5 vs. 8.7 ± 1.0 ms/mmHg, p < 0.05). The slope of the regression line between defined increases or reductions in systolic blood pressure and R-R intervals was significantly reduced in CAN, compared to C (supine: 10.6 ± 0.7 vs. 14.2 ± 1.6 ms/mmHg, p < 0.05; standing: 5.6 ± 0.4 vs. 8.1 ± 0.7 ms/mmHg, p < 0.05). Similar differences were obtained when comparing the CAN, and CAN[+] groups, the latter showing significantly reduced BRS by both techniques (p < 0.05). In contrast, no such differences were noted when comparing the CAN[+] and CAN+ groups. In conclusion, reduced spontaneous baroreflex sensitivity is an early marker of autonomic dysfunction at a stage when autonomic function tests do not yet indicate the presence of CAN, while cases with borderline CAN show a degree of BRS abnormality that is comparable to the level seen in definite CAN. Prospective studies are needed to evaluate whether reduced BRS is a predictor of mortality in diabetic patients. [source]

Baroreflex Sensitivity: Measurement and Clinical Implications

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008
Maria Teresa La Rovere M.D.
Alterations of the baroreceptor-heart rate reflex (baroreflex sensitivity, BRS) contribute to the reciprocal reduction of parasympathetic activity and increase of sympathetic activity that accompany the development and progression of cardiovascular diseases. Therefore, the measurement of the baroreflex is a source of valuable information in the clinical management of cardiac disease patients, particularly in risk stratification. This article briefly recalls the pathophysiological background of baroreflex control, and reviews the most relevant methods that have been developed so far for the measurement of BRS. They include three "classic" methods: (i) the use of vasoactive drugs, particularly the ,-adrenoreceptor agonist phenylephrine, (ii) the Valsalva maneuver, which produces a natural challenge for the baroreceptors by voluntarily increasing intrathoracic and abdominal pressure through straining, and (iii) the neck chamber technique, which allows a selective activation/deactivation of carotid baroreceptors by application of a negative/positive pressure to the neck region. Two more recent methods based on the analysis of spontaneous oscillations of systolic arterial pressure and RR interval are also reviewed: (i) the sequence method, which analyzes the relationship between increasing/decreasing ramps of blood pressure and related increasing/decreasing changes in RR interval through linear regression, and (ii) spectral methods, which assess the relationship (in terms of gain) between specific oscillatory components of the two signals. The limitations of the coherence criterion for the computation of spectral BRS are discussed, and recent proposals for overcoming them are presented. Most relevant clinical applications of BRS measurement are finally reviewed with particular reference to patients with myocardial infarction and heart failure. [source]

Baroreflex Sensitivity of an Arterial Wall During Rotary Blood Pump Assistance

ARTIFICIAL ORGANS, Issue 9 2009
Tomoyuki Yambe
Abstract It is well known that the baroreflex system is one of the most important indicators of the pathophysiology in hypertensive patients. We can check the sensitivity of the baroreflex by observing heart rate (HR) responses; however, there is no simple diagnostic method to measure the arterial behavior in the baroreflex system. Presently, we report the development of a method and associated hardware that enables the diagnosis of baroreflex sensitivity by measuring the responses of both the heart and the artery. In this system, the measurements are obtained by monitoring an electrocardiogram and a pulse wave recorded from the radial artery or fingertip. The arterial responses were measured in terms of the pulse wave velocity (PWV) calculated from the pulse wave transmission time (PTT) from the heart to the artery. In this system, the HR change corresponding to the blood pressure change in time series sequence was observed. Slope of the changes in blood pressure and HR indicated the sensitivity of the baroreflex system of the heart. This system could also measure the sensitivity of the baroreflex system of an artery. Changes in the PWV in response to the blood pressure changes were observed. Significant correlation was observed in the time sequence between blood pressure change and PWV change after calculating the delay time by cross-correlation. The slope of these parameter changes was easily obtained and it demonstrated the sensitivity of the baroreflex system of an artery. We evaluated this method in animal experiments using rotary blood pump (RBP) with undulation pump ventricular assist device, and PTT elongation was observed in response to increased blood pressure with RBP assistance. Furthermore, when tested clinically, decreased sensitivity of the baroreflex system in hypertensive patients was observed. This system may be useful when we consider the ideal treatment and follow-up of patients with hypertension. [source]

Analysis of Baroreflex Sensitivity During Undulation Pump Ventricular Assist Device Support

ARTIFICIAL ORGANS, Issue 7 2009
Hongjian Liu
Abstract The aim of this study was to examine the baroreflex sensitivity (BRS), which involves the autonomic nervous system, in a goat with a chronically implanted undulation pump ventricular assist device (UPVAD). The UPVAD involved transforming the rotation of a brushless DC motor into an undulating motion by a disc attached via a special linking mechanism, and a jellyfish valve in the outflow cannula to prevent diastolic backflow. The pump was implanted into the thoracic cavity of a goat by a left thoracotomy, and the inflow and outflow cannulae were sutured to the apex of the left ventricle and to the descending aorta, respectively. The driving cable was wired percutaneously to an external controller. Electrocardiogram and hemodynamic waveforms were recorded at a sampling frequency of 1 kHz. BRS was determined when awake by the slope of the linear regression of R-R interval against mean arterial pressure changes, which were induced by the administration of methoxamine hydrochloride, both with continuous driving of the UPVAD as well as without assistance. BRS values during the UPVAD support and without assistance were 1.60 ± 0.30 msec/mm Hg and 0.98 ± 0.22 msec/mm Hg (n = 5, P < 0.05), respectively. BRS was significantly improved during left ventricular assistance. Therefore, UPVAD support might decrease sympathetic nerve activity and increase parasympathetic nerve activity to improve both microcirculation and organ function. [source]

The combination of atenolol and amlodipine is better than their monotherapy for preventing end-organ damage in different types of hypertension in rats

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2009
Ping Han
Abstract Combinations therapy is often used in hypertensive patients whether combination therapy is necessary for preventing end-organ damage is not known. The objective of this study was to determine in four different hypertensive animal models the necessity of adding the calcium channel blocker amlodipine to therapy with the ß-blocker atenolol to modulate end-organ damage. Spontaneously hypertensive rats, DOCA-salt hypertensive rats, two-kidney, one-clip renovascular hypertensive rats and Lyon genetically hypertensive rats were used to study this objective. These animal models have different sensitivities to atenolol and amlodipine. The dosages of therapy employed were 10 mg/kg atenolol alone, 1 mg/kg amlodipine, 10 mg atenolol + 1 mg/kg amlodipine and 5 mg/kg atenolol+0.5 mg/kg amlodipine. BP was continuously recorded in all animals. After determination of baroreflex sensitivity, rats were sacrificed for end-organ damage evaluation. The combination of amlodipine and atenolol had a synergistic inhibitory effect on blood pressure and blood pressure variability, and end-organ damage as compared with monotherapy with atenolol or amlodipine in all animal models. Baroreflex sensitivity also improved with the combination therapy more than with monotherapy. In conclusion, atenolol and amlodipine combination exerts a superior effect on blood pressure, blood pressure variability, baroreflex sensitivity and end-organ damage. The superior effect of the combination was observed in all four models of hypertension. [source]

Relationship Between Myocardial Beta-Adrenergic Sensitivity and Heart Rate Variability

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2000
Philippe Cabrol M.D.
Background: In congestive heart failure, despite activation of the sympathetic nervous system, heart rate variability parameters reflecting sympathetic modulation on sinus node are decreased. Our goal was to assess the role of beta-adrenergic sensitivity in the modulation of heart rate variability (HRV) in patients with valvular heart diseases. Methods and results: Ten patients with aortic stenosis, 10 patients with heart failure, and 12 controls were included. Baroreflex sensitivity was calculated by the sequency method. Noradrenaline plasma levels were assayed by HPLC. HRV was studied using 24-hour Holter monitoring. Cardiac beta-adrenergic receptivity was assessed by the chronotropic response to dobutamine. Right auricular samples were obtained for determination of beta-adrenergic receptor density by binding study with [125I]-iodocynaopindolol, and beta 1 and beta 2 densities, measured by competition between 125ICP binding by isoprenaline. In multivariate analysis, the dose of dobutamine that increases basal heart rate for 25 beats/min (ED25) is correlated with a parameter of global HRV: SDNN (r = 0.6, P < 0.001) and with indexes reflecting rather sympathetic modulation of HRV: SDANN (r = 0.62, P < 0.001) or SD (r = 0.47, P < 0.0001). All these relations were independent from mean NN, spontaneous baroreflex sensitivity, and noradrenaline plasma levels. No significant correlation existed between dobutamine ED25 and HRV indexes reflecting parasympathic tone. No relationship existed between HRV and beta-adrenergic receptor-binding characteristics. Conclusion: Cardiac beta-adrenergic sensitivity explored by dobutamine ED25 is an important determinant of HRV independent from mean NN, spontaneous baroreflex sensitivity, and noradrenaline plasma levels. [source]

Spontaneous baroreflex sensitivity as a dynamic measure of cardiac anticholinergic drug effect

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2001
J. Penttilä
1,In this study, the analysis of spontaneous baroreflex sensitivity (BRS) was applied to the dynamic assessment of cardiac anticholinergic drug effect in healthy male volunteers. 2,The anticholinergic effects of single intravenous (i.v.) injections of atropine (10 ,g kg,1), glycopyrrolate (5 ,g kg,1) and scopolamine (5 ,g kg,1), as well as a 2-h infusion of glycopyrrolate (5 ,g kg,1 h,1) were investigated. Baroreflex sensitivity, a validated measure of cardiac parasympathetic reflex regulation, was repeatedly measured from 5-min recordings of electrocardiogram (ECG) and continuous blood pressure by using the sequence technique, a method based on detection of spontaneous fluctuations in blood pressure and heart rate. 3,Single injections of atropine, glycopyrrolate and scopolamine decreased the mean BRS by 71 ± 32, 68 ± 23 and 27 ± 45%, respectively, whereas the slow glycopyrrolate infusion gradually decreased BRS (up to 83 ± 11% reduction) and increased both systolic (SAP) and diastolic arterial pressures (DAP) (on an average, by 9 mmHg). 4,During the withdrawal of the parasympathetic blockade (indicated by increasing BRS), the proportion of baroreflex sequences in the recordings increased transiently from 10 up to 20,25%, probably reflecting the restoration of the baroreflex integrity and the baroreflex-induced attempt to counteract the blood pressure increase. 5,The sequence method to study BRS seems to be feasible in the assessment of cardiac anticholinergic drug effects, and it also provides good time resolution for the dynamic measurements. [source]

Geomagnetic field effect on cardiovascular regulation

BIOELECTROMAGNETICS, Issue 2 2004
Juraj Gmitrov
Abstract The goal of the present research was try to explain the physiological mechanism for the influence of the geomagnetic field (GMF) disturbance, reflected by the indices of the geomagnetic activity (K, Kp, Ak, and Ap indices), on cardiovascular regulation. One hundred forty three experimental runs (one daily) comprising 50 min hemodynamic monitoring sequences were carried out in rabbits sedated by pentobarbital infusion (5 mg/kg/h). We examined the arterial baroreflex effects on the short term blood pressure and heart rate (HR) variabilities reflected by the standard deviation (SD) of the average values of the mean femoral arterial blood pressure (MAP) and the HR. Baroreflex sensitivity (BRS) was estimated from blood pressure/HR response to intravenous (i.v.) bolus injections of vasoconstrictor (phenylephrine) and vasodilator (nitroprusside) drugs. We found a significant negative correlation of increasing GMF disturbance (Kp) with BRS (P,=,0.008), HR SD (P,=0.022), and MAP SD (P,=,0.002) signifying the involvement of the arterial baroreflex mechanism. The abrupt change in geomagnetic disturbance from low (K,=,0) to high (K,=,4,5) values was associated with a significant increase in MAP (83,±,5 vs. 99,±,5 mm Hg, P,=,0.045) and myocardial oxygen consumption, measured by MAP and HR product (24100,±,1800 vs. 31000,±,2500 mm Hg,·,bpm, P,=,0.034), comprising an additional cardiovascular risk. Most likely, GMF affects brainstem and higher neural cardiovascular regulatory centers modulating blood pressure and HR variabilities associated with the arterial baroreflex. Bioelectromagnetics 25:92,101, 2004. © 2004 Wiley-Liss, Inc. [source]

Cardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertension

ACTA PHYSIOLOGICA, Issue 3 2009
S. R. Collier
Abstract Aim:, Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP). Methods:, Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained. Results:, There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 ± 3.0 pre- to 132 ± 3.4 post-training vs. AE 142 ± 4.0 pre- to 137 ± 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 ± 1.31 pre to 74 ± 1.1 post vs. AE 80 ± 1.7 pre to 77 ± 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 ± 67.28 to 161.26 ± 61.49) and RE increasing this ratio (143.73 ± 65.00 to 227.83 ± 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 ± 0.38 to 5.4 ± 0.35 ms2) following AE and decreased (5.98 ± 0.37 to 5.76 ± 0.42 ms2) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 ± 1.2 to 7.94 ± 1.3 and 10.44 ± 1.2 to 9.1 ± 1.2 ms mmHg,1 respectively, P = 0.021). Conclusions:, Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS. [source]

No effect of venoconstrictive thigh cuffs on orthostatic hypotension induced by head-down bed rest

ACTA PHYSIOLOGICA, Issue 2 2000
M.-A. Custaud
Orthostatic intolerance (OI) is the most serious symptom of cardiovascular deconditioning induced by head-down bed rest or weightlessness. Wearing venoconstrictive thigh cuffs is an empirical countermeasure used by Russian cosmonauts to limit the shift of fluid from the lower part of the body to the cardio-cephalic region. Our aim was to determine whether or not thigh cuffs help to prevent orthostatic hypotension induced by head-down bed rest. We studied the effect of thigh cuffs on eight healthy men. The cuffs were worn during the day for 7 days of head-down bed rest. We measured: orthostatic tolerance (stand tests and lower body negative pressure tests), plasma volume (Evans blue dilution), autonomic influences (plasma noradrenaline) and baroreflex sensitivity (spontaneous baroreflex slope). Thigh cuffs limited the loss of plasma volume (thigh cuffs: ,201 ± 37 mL vs. control: ,345 ± 42 mL, P < 0.05), the degree of tachycardia and reduction in the spontaneous baroreflex sensitivity induced by head-down bed rest. However, the impact of thigh cuffs was not sufficient to prevent OI (thigh cuffs: 7.0 min of standing time vs. control: 7.1 min). Decrease in absolute plasma volume and in baroreflex sensitivity are known to be important factors in the aetiology of OI induced by head-down bed rest. However, dealing with these factors, using thigh cuffs for example, is not sufficient to prevent OI. Other factors such as venous compliance, microcirculatory changes, peripheral arterial vasoconstriction and vestibular afferents must also be considered. [source]

Effects of age on the cardiac and vascular limbs of the arterial baroreflex

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2003
C. M. Brown
Abstract Background Healthy ageing has several effects on the autonomic control of the circulation. Several studies have shown that baroreflex-mediated vagal control of the heart deteriorates with age, but so far there is little information regarding the effect of ageing on sympathetically mediated baroreflex responses. The aim of this study was to assess the effects of ageing on baroreflex control of the heart and blood vessels. Materials and Methods In 40 healthy volunteers, aged 20,87 years, we applied oscillatory neck suction at 0·1 Hz to assess the sympathetic modulation of the heart and blood vessels and at 0·2 Hz to assess the effect of parasympathetic stimulation on the heart. Breathing was maintained at 0·25 Hz. Blood pressure, electrocardiographic RR intervals and respiration were recorded continuously. Spectral analysis was used to evaluate the magnitude of the low-frequency (0·03,0·14 Hz) and high-frequency (0·15,0·50 Hz) oscillations in the RR interval and blood pressure. Responses to neck suction were assessed as the change in power of the RR interval and blood pressure fluctuations at the stimulation frequency from baseline values. Results Resting low- and high-frequency powers of the RR interval decreased significantly with age (P < 0·01). However, the low-frequency power of systolic blood pressure did not correlate with age. Spontaneous baroreflex sensitivity (alpha-index) showed a significant inverse correlation with age (r = ,0·46, P < 0·05). Responses of the RR interval and systolic blood pressure to 0·1 Hz neck suction stimulation were not related to age, however, the RR interval response to 0·2 Hz neck suction declined significantly with age (r = ,0·61, P < 0·01). Conclusions These results confirm an age-related decrease in cardiovagal baroreflex responses. However, sympathetically mediated baroreflex control of the blood vessels is preserved with age. [source]

Cardioventilatory Coupling in Resting Human Subjects

EXPERIMENTAL PHYSIOLOGY, Issue 6 2003
Y. C. Tzeng
In 48 conscious resting subjects we examined the temporal coupling of heart beat timing and the onset of inspiration (cardioventilatory coupling), and the relationship between coupling and spectral indices of autonomic function. Using the proportional Shannon entropy (SH,) of the RI -1 interval (interval between inspiration and the preceding ECG R wave) as a measure of coupling we detected statistically significant coupling in 32 of the 48 subjects. This was confirmed by visual inspection of time series plots of RI intervals, in which coupling was evident as horizontal banding. Coupling resulted in a significant preference for whole number heart rate/respiratory frequency ratios. The strongest coupling was associated with low ventilatory frequency and high heart rate variability in the high (0.15-0.40 Hz) and low (0.04-0.15 Hz) frequency ranges, but was not related to blood pressure variability, or to a spectral measure of baroreflex sensitivity (,-index, low frequency range). There was no difference in coupling strength between males and females. We have previously described cardioventilatory coupling in spontaneously breathing anaesthetised subjects. The current study extends those observations by demonstrating that the qualitative features of coupling seen during anaesthesia are also observed in the conscious state. We conclude that the role of coupling in normal physiological respiratory control needs to be more widely explored. [source]

Cool dialysate reduces asymptomatic intradialytic hypotension and increases baroreflex variability

HEMODIALYSIS INTERNATIONAL, Issue 2 2009
Lindsay J. CHESTERTON
Abstract Intradialytic hypotension (IDH) remains an important cause of morbidity and mortality in chronic hemodialysis (HD) patients and can be ameliorated by cool temperature HD. The baroreflex arc is under autonomic control and is essential in the short-term regulation of blood pressure (BP). This study aimed to investigate if the baroreflex sensitivity (BRS) response to HD differed between standard and cool-temperature dialysate. Ten patients (mean age 67±2 years) prone to IDH were recruited into a randomized, crossover study to compare BRS variation at dialysate temperatures of 37 °C (HD37) and 35 °C (HD35). Each patient underwent continuous beat-to-beat BP monitoring during a dialysis session of HD37 and HD35. During HD37 2 patients developed symptomatic IDH, as opposed to 1 with HD35. However, asymptomatic IDH occurred with a frequency of 0.4 episodes per session with HD35 and 6.2 episodes per session during HD37 (odds ratio15.5; 95%CI 5.6,14.2). Although absolute BRS measurements did not differ between the 2 modalities, BRS variability increased during HD35. Our study has demonstrated that in IDH-prone patients, cool HD resulted in a reduction in heart rate and a greater reduction in cardiac output and stroke volume. Mean arterial pressure was maintained through a significantly greater increase in total peripheral resistance. Furthermore, although absolute BRS values during HD were not significantly altered by a reduction in dialysate temperature, there was a greater percentage increase in BRS values during cool HD. Understanding the varied causes of, and categorizing impaired hemodynamic responses to HD will enable further individualization of HD prescriptions according to patient need. [source]

Relationship Between Heart Rate Turbulence and Heart Rate, Heart Rate Variability, and Number of Ventricular Premature Beats in Coronary Patients

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2004
IWONA CYGANKIEWICZ M.D., Ph.D.
Introduction: Heart rate variability (HRV) illustrates regulation of the heart by the autonomic nervous system whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity. The aim of this study was to determine the association between HRT and HRV parameters and the relationship between HRT parameters and heart rate and number of ventricular premature beats (VPBs) used to calculate HRT parameters. Methods and Results: In 146 patients (117 males and 29 females; mean age 62 years) with coronary artery disease, a 24-hour ECG Holter monitoring was performed to calculate mean heart rate (RR interval), number of VPBs, time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (TO) and turbulence slope (TS). Univariate and multivariate regression analyses were performed to evaluate the association between tested parameters. Significant correlation between TS and mean RR interval was observed (r = 0.42; p < 0.001), while no association for TO vs. RR interval was found. TS values were significantly higher in patients with less than 10 VPBs/24 hours than in patients with more frequent VPBs. Significant associations between HRT and HRV parameters were found with TS showing stronger correlation with HRV parameters than TO (r value ranging from 0.35 to 0.62 for TS vs. ,0.16 to ,0.38 for TO). Conclusion: HRT parameters correlate strongly with HRV parameters indicating that HRT should be considered as a reflection of both baroreceptors response and overall autonomic tone. Heart rate dependence of turbulence slope indicates the need to adjust this parameter for heart rate. (J Cardiovasc Electrophysiol, Vol. 15, pp. 731-737, July 2004) [source]

Heterogeneous Regional Endocardial Repolarization is Associated with Increased Risk for Ischemia-Dependent Ventricular Fibrillation after Myocardial Infarction

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003
Michael H. Swann M.SC.
Introduction: The aim of this study was to investigate whether the characteristics of endocardial ventricular repolarization are associated with differential risk for sudden death. Prolonged surface QT interval is associated with increased arrhythmic risk after myocardial infarction (MI), but the underlying mechanism of QT prolongation and its relation to lethal arrhythmias are unclear. Methods and Results: Ventricular fibrillation (VF) risk was assessed in 12 dogs 1 month after anterior MI during an exercise test coupled with brief circumflex coronary occlusion. Susceptible dogs (n = 5) developed VF during the brief ischemic episode, whereas resistant dogs did not (n = 7). Surface QT interval was measured at rest. Endocardial electroanatomic catheter maps of left ventricular repolarization were obtained in four unique regions identified by echocardiography and compared between groups. Compared to resistant dogs, susceptible dogs were characterized by prolonged surface QT intervals (240 ± 10 msec vs 222 ± 7 msec, P = 0.04). In addition, they had lower baroreflex sensitivity (9.7 ± 1.5 msec/mmHg vs 28 ± 9.8 msec/mmHg, P < 0.01) and a tachycardic response to acute ischemia suggesting higher propensity for stronger sympathetic reflexes. Surface QT interval prolongation in susceptible dogs was due to a marked heterogeneity of endocardial left ventricular repolarization (239 ± 42 msec, basal anterior wall vs 197 ± 35, lateral wall; P < 0.001). Resistant animals had no regional differences in endocardial repolarization. Conclusion: Sympathetic activation following MI not only produces adverse structural remodeling but also contributes to adverse electrophysiologic remodeling resulting in heterogeneous ventricular repolarization and in a myocardial substrate conducive to lethal reentrant arrhythmias. (J Cardiovasc Electrophysiol, Vol. 14, pp. 873-879, August 2003) [source]

The combination of atenolol and amlodipine is better than their monotherapy for preventing end-organ damage in different types of hypertension in rats

Role of Myocardial Contractility and Autonomic Control in the Hypotensive Response to a Limited Access Ethanol Paradigm in SHRs

ALCOHOLISM, Issue 6 2007
Mahmoud M. El-Mas
Background: Previous experimental studies that evaluated the chronic hemodynamic effect of ethanol employed the continuous exposure protocol of ethanol, which does not mimic the pattern of alcohol consumption in humans. This study dealt with the long-term hemodynamic and cardiovascular autonomic effects of ethanol, in a limited-access regimen in telemetered spontaneously hypertensive rats (SHRs). Methods: Changes in blood pressure (BP), heart rate (HR), myocardial contractility (dP/dtmax), and spectral cardiovascular autonomic profiles during the ethanol exposure period (2.5 or 5% w/v, 8 h/d, 8:30 am till 4:30 pm) were followed for 12 weeks. Results: Compared with control pair-fed SHRs, body weight and urine output, osmolality, and potassium levels were decreased in SHRs receiving 5% but not 2.5% ethanol. Blood pressure showed progressive falls during ethanol-feeding periods with a maximum effect observed at week 5. The peak hypotensive effect was maintained thereafter in SHRs receiving 5% ethanol in contrast to steady rises in BP in the 2.5% ethanol group to near-control levels by the conclusion of the study. Heart rate was slightly but significantly increased by ethanol 5% whereas dP/dtmax showed persistent reductions. Power spectral analysis showed that ethanol attenuated the baroreflex gain of HR as suggested by the reductions in index ,, the spectral index of spontaneous baroreflex sensitivity (BRS). Conclusions: It is concluded that limited access ethanol drinking in SHRs elicited hypotension that was concentration dependent and mediated, at least partly, through reductions in myocardial contractility. Baroreflex sensitivity attenuation by ethanol appeared to have limited the tachycardic response to ethanol and perhaps its capacity to offset the evoked hypotension. [source]

Early Detection Of Diminished Baroreflex Sensitivity In Diabetic Patients Without Evidence Of Cardiovascular Autonomic Neuropathy

Baroreceptor sensitivity and baroreceptor effectiveness index in cirrhosis: the relevance of hepatic venous pressure gradient

LIVER INTERNATIONAL, Issue 2 2010
Simonetta Genovesi
Abstract Background: Autonomic dysfunction has been reported as one of the complications of cirrhosis. Aims: The aim of this study was to test autonomic dysfunction in cirrhotic patients by analysing the baroreflex sensitivity and the baroreceptor effectiveness index (BEI), in order to determine its correlation with the severity and the aetiology of liver disease. Moreover, we explored the relationship between baroreceptor function and mortality in our cohort of patients. Methods: Clinical and laboratory evaluation, hepatic venous pressure gradient (HVPG) and haemodynamic setting and baroreceptor function were assessed in 45 cirrhotic patients (median age 55, range 38,72 years) divided in groups according to the severity of their disease (26 patients Child A, 13 patients Child B and six patients Child C). Results: Baroreceptor sensitivity and BEI were impaired in more advanced cirrhotic patients compared with subjects with milder disease (P<0.001). HVPG was significantly, independently and inversely correlated with baroreceptor sensitivity (P=0.003). More severe impairment of baroreceptor function was associated with a higher mortality (P=0.04) and subjects with alcohol-related cirrhosis presented worse baroreceptor function (P=0.032) and poorer survival (P=0.003) compared with subjects with post-viral liver disease. Conclusions: These data support the hypothesis that liver disease severity and particularly portal hypertension have an important role in the derangement of baroreceptor function. The aetiology of cirrhosis seems to be related to baroreceptor impairment as well. Mortality rate is higher in subjects with a more damaged autonomic system, strengthening the idea of a worse prognosis in cirrhotic patients with autonomic neuropathy. [source]

Altered Autonomic Cardiac Control Predicts Restenosis After Percutaneous Coronary Intervention

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2006
MATTHIAS GOERNIG
Background: Early and late restenosis in up to 30% remains a major problem for long-term success after percutaneous coronary intervention (PCI). Compared to bare metal stents, the use of drug-eluting stents reduces restenosis below 10%, but implant coasts have to be considered. In restenosis noninvasive testing lacks diagnostic power. We applied a new approach to identify patients with a high risk for restenosis after PCI by combining heart rate (HR) and blood pressure variability (BPV) analyses. Methods: In 52 patients with clinical suspicion of restenosis and history of PCI, we investigated patterns of cardiovagal autonomic regulation prior to cardiac catheterization. The patients were separated in (i) patients with restenosis (CAD+R) and (ii) patients without restenosis (CAD,R), where restenosis is defined as a stenosis greater than 75% of luminal diameter in at least one main vessel. The following parameters/methods were evaluated: Canadian Cardiovascular Society grade (CCS-grade), vessel disease score (CAD-level), left ventricular ejection fraction (LVEF), heart rate variability (HRV), BPV, baroreflex sensitivity (BRS), as well as HR turbulence and blood pressure (BP) potentiation caused by premature ventricular complexes. Results: Whereas age, LVEF, CAD-level, CCS-grade, and mean BP did not differ between CAD+R and CAD,R, significant differences were found in (i) BPV: diastolic LF/P, systolic, and diastolic UVLF, (ii) in BRS: slope of tachycardic sequences, and (iii) in extrasystolic parameters: heart rate turbulence onset (HRTO) and potentiation of systolic BP (SBPP). Standard HRV parameters did not show significant differences between the groups. Using the two parameters diastolic LF/P (threshold >0.2) and HRTO (threshold >0) restenosis were predicted in 83.4%. Conclusions: These results demonstrate that indicators of sympathetic activation or vagal depression identify restenosis in patients after PCI, thus opening a perspective for a new noninvasive monitoring. [source]

Cardiac modulation of startle eye blink

PSYCHOPHYSIOLOGY, Issue 2 2009
André Schulz
Abstract As an alternative to interoceptive paradigms that depend on the participants' active cooperation, two studies are presented to show that startle methodology may be employed to study visceral afferent processing. The first study of 38 volunteers showed that startle responses were smaller when elicited during cardiac systole as compared to diastole. In the second study, 31 diabetic patients were divided into two groups, having normal or diminished (<6 ms/mmHg) baroreflex sensitivity (BRS). Patients with normal BRS showed the same results found in healthy volunteers. Diabetic patients with diminished BRS did not show this pattern. Because diminished BRS is an indicator of impaired baro-afferent signal transmission, it is concluded that cardiac modulation of startle is associated with intact baro-afferent feedback. Thus, pre-attentive startle methodology is feasible to study visceral afferent processing originating from the cardiovascular system. [source]

Vasomotor sympathetic neural control is maintained during sustained upright posture in humans

THE JOURNAL OF PHYSIOLOGY, Issue 2 2006
Qi Fu
Vasomotor sympathetic activity plays an important role in arterial pressure maintenance via the baroreflex during acute orthostasis in humans. If orthostasis is prolonged, blood pressure may be supported additionally by humoral factors with a possible reduction in sympathetic baroreflex sensitivity. We tested the hypothesis that baroreflex control of muscle sympathetic nerve activity (MSNA) decreases during prolonged upright posture. MSNA and haemodynamics were measured supine and during 45 min 60 deg upright tilt in 13 healthy individuals. Sympathetic baroreflex sensitivity was quantified using the slope of the linear correlation between MSNA and diastolic pressure during spontaneous breathing. It was further assessed as the relationship between MSNA and stroke volume, with stroke volume derived from cardiac output (C2H2 rebreathing) and heart rate. Total peripheral resistance was calculated from mean arterial pressure and cardiac output. We found that MSNA increased from supine to upright (17 ± 8 (s.d.) versus 38 ± 12 bursts min,1; P < 0.01), and continued to increase to a smaller degree during sustained tilt (39 ± 11, 41 ± 12, 43 ± 13 and 46 ± 15 bursts min,1 after 10, 20, 30 and 45 min of tilt; between treatments P < 0.01). Sympathetic baroreflex sensitivity increased from supine to upright (,292 ± 180 versus,718 ± 362 units beat,1 mmHg,1; P < 0.01), but remained unchanged as tilting continued (,611 ± 342 and ,521 ± 221 units beat,1 mmHg,1 after 20 and 45 min of tilt; P= 0.49). For each subject, changes in MSNA were associated with changes in stroke volume (r= 0.88 ± 0.13, P < 0.05), while total peripheral resistance was related to MSNA during 45 min upright tilt (r= 0.82 ± 0.15, P < 0.05). These results suggest that the vasoconstriction initiated by sympathetic adrenergic nerves is maintained by ongoing sympathetic activation during sustained (i.e. 45 min) orthostasis without obvious changes in vasomotor sympathetic neural control. [source]

Denervation of Carotid Baro- and Chemoreceptors in Humans

THE JOURNAL OF PHYSIOLOGY, Issue 1 2003
Henri J. L. M. Timmers
Experimental denervation in animals has shown that carotid baro- and chemoreceptors play an eminent role in maintaining blood pressure and blood gas homeostasis. Denervation of carotid sinus baro- and chemoreceptors in humans may occur as a complication of invasive interventions on the neck or after experimental surgical treatment in asthma. In this topical review, the short- and long-term effects of carotid baro- and chemoreceptor denervation on the control of circulation and ventilation in humans are discussed. Carotid baroreceptor denervation in humans causes a persistent decrease in vagal and sympathetic baroreflex sensitivity and an increase in blood pressure variability; however, carotid denervation does not lead to chronic hypertension. Therefore, although carotid baroreceptors contribute to short-term blood pressure control, other receptors are able to maintain normal chronic blood pressure levels in the absence of carotid baroreceptors. Conversely, carotid chemoreceptor denervation leads to permanent abolition of normocapnic ventilatory responses to hypoxia and reduced ventilatory responses to hypercapnia. [source]

Predictors of Long-Term Risk for Heart Failure Hospitalization after Acute Myocardial Infarction

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2010
Juha S. Perkiömäki M.D.
Background: Data on the value of baseline brain natriuretic peptide (BNP) and autonomic markers in predicting heart failure (HF) hospitalization after an acute myocardial infarction (AMI) are limited. Methods: A consecutive series of patients with AMI without a previous history of HF (n = 569) were followed up for 8 years. At baseline, the patients had a blood sample for determination of BNP, a 24-hour Holter recording for evaluating heart rate variability (HRV) and heart rate turbulence (HRT), and an assessment of baroreflex sensitivity (BRS) using phenylephrine test. Results: During the follow-up, 79 (14%) patients were hospitalized due to HF. Increased baseline BNP, decreased HRV, HRT, and BRS had a significant association with HF hospitalization in univariate comparisons (P < 0.001 for all). After adjusting with all the relevant clinical parameters, BNP, HRV, and HRT still significantly predicted HF hospitalization (P < 0.001 for BNP and for the short-term scaling exponent ,1, P < 0.01 for turbulence slope). In the receiver operator characteristics curve analysis, the area under the curve for BNP was 0.77, for the short-term scaling exponent ,1 0.69, for turbulence slope 0.71, and for BNP/standard deviation of all N-N intervals ratio 0.80. Conclusion: Baseline increased BNP and impaired autonomic function after AMI yield significant information on the long-term risk for HF hospitalization. Ann Noninvasive Electrocardiol 2010;15(3):250,258 [source]

Influence of Age on Linear and Nonlinear Measures of Autonomic Cardiovascular Modulation

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Michael K. Boettger M.D.
Background: Age has been identified as an independent risk factor for cardiovascular diseases. In addition, autonomic imbalance toward sympathetic preponderance has been shown to facilitate the occurrence of heart disease. Here, we aimed to assess autonomic modulation of cardiovascular parameters during normal ageing applying well-established linear and novel nonlinear parameters. Methods: Linear and nonlinear measures of heart rate variability and complexity as well as measures of QT interval variability and baroreflex sensitivity were obtained from a total of 131 healthy, medication-free participants from a continuous age range between 20 and 90 years, who were allocated to three different age groups. Results: Heart rate variability and complexity significantly decreased with age, while regularity of heart rate time series increased. In addition, QT interval variability linearly increased with age, while baroreflex sensitivity showed a pronounced decrease. Overall, concerning effects of ageing, linear and nonlinear parameters showed equal differentiation between groups. Conclusion: These data indicate a shift of autonomic balance toward sympathetic predominance in higher age groups, limiting the reactiveness of the cardiovascular system to adjust to different demands and increasing the risk for developing tachyarrhythmias. Ann Noninvasive Electrocardiol 2010;15(2):165,174 [source]

Baroreflex Sensitivity: Measurement and Clinical Implications

Usefulness of Risk Stratification for Future Cardiac Events in Infarct Survivors with Severely Depressed Versus Near-Normal Left Ventricular Function: Results From a Prospective Long-Term Follow-Up Study

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2003
Thomas Klingenheben
Background: Although primary preventive therapy with implantable cardioverter defibrillators has recently been shown to be effective in patients with coronary artery disease and left ventricular dysfunction, further identification of patients at particularly high risk for arrhythmic death would improve the cost effectiveness of device therapy. The value of risk stratification in postinfarction patients with versus those without left ventricular dysfunction has not been investigated in detail in infarct survivors treated according to contemporary therapeutic guidelines. Methods: Patients with acute myocardial infarction underwent coronary angiography including left ventricular angiography in an attempt to restore antegrade flow of the infarct-related artery. Additionally, patients underwent noninvasive autonomic risk stratification by means of heart rate variability (HRV) and baroreflex sensitivity (BRS) measurements prior to hospital discharge. Results: A total of 411 patients were prospectively included in the study. The primary study endpoint of cardiac death and arrhythmic events was significantly more common in patients with LVEF , 35% as compared to those with preserved LV function (27% vs 4%; P < 0.0001). In patients with LV dysfunction, HRV and BRS were significant risk predictors on univariate (P < 0.01 for BRS; P = 0.04 for HRV) and multivariate (P = 0.028 for BRS; P = 0.053 for HRV) analyses. In contrast, in patients with preserved LV function, only patency of the infarct artery but not autonomic markers was significantly predictive of cardiac death and arrhythmic events. Conclusion: The present study demonstrates that autonomic testing does not yield predictive power in infarct survivors with preserved left ventricular function. Accordingly, cost effectiveness of risk stratification and subsequent preventive therapy may be improved by restricting risk stratification to patients with impaired LV function. [source]