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Journal Article

How to measure baroreflex sensitivity

01 Jan 2006-Cardiology Journal (Via Medica)-Vol. 13, Iss: 7, pp 630-637

TL;DR: The use of vasoactive drugs and the analysis of spontaneously occurring changes in blood pressure and heart rate are described.

AbstractIn normal subjects arterial baroreflexes play a key role in short-term blood pressure adjustments to a variety of environmental stresses, thereby maintaining circulatory homeostasis. These responses are mediated by the sympathetic and parasympathetic nervous systems through their effects on heart rate, venous return, contractility and peripheral resistance. The evaluation of baroreflex sensitivity (BRS) has recently found unexpected exploitations as alterations in the baroreflex control of heart rate have been associated with an increased propensity for cardiac mortality and sudden cardiac death [1]. Among several quantitative approaches developed for evaluating BRS including the analysis of reflex responses to pharmacological or mechanical manipulations of baroreceptors, this article describes the use of vasoactive drugs and the analysis of spontaneously occurring changes in blood pressure and heart rate.

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Journal ArticleDOI
TL;DR: In CHF patients in sinus rhythm, TF-BRS conveys relevant clinical and prognostic information, but its measurability is markedly affected by ectopic activity, and a new prognostic index can be computed in almost all patients.
Abstract: Objectives We sought to assess applicability, clinical correlates, and prognostic value of the transfer function method for measuring baroreflex sensitivity (TF-BRS). Background Abnormalities in autonomic reflexes play an important role in the development and progression of chronic heart failure (CHF). Simple and non-invasive techniques for clinical measurement of such reflexes are desirable. Methods In 317 stable CHF patients in sinus rhythm (median age [interquartile range]: 54 years [48 to 59 years], New York Heart Association [NYHA] functional class II to III: 88%, left ventricular ejection fraction [LVEF]: 27% [22% to 33%]) we recorded electrocardiograms and non-invasive arterial pressure during paced breathing to measure TF-BRS. Results Owing to a high number of ectopic beats, TF-BRS could be computed in 72% of the patients; TF-BRS was lower in NYHA functional class III to IV and mitral regurgitation 2 to 3 (p Conclusions In CHF patients in sinus rhythm, TF-BRS conveys relevant clinical and prognostic information, but its measurability is markedly affected by ectopic activity. Nevertheless, a TF-BRS–based risk index carrying significant and independent prognostic information can be computed in almost all patients.

74 citations


Journal ArticleDOI
TL;DR: The data indicate that different baroreflex components and mechanisms may be impaired in patients with depression and may contribute to their increased cardiac risk.
Abstract: BACKGROUND: Recent studies have shown that depressive disorder is associated with impaired baroreceptor or baroreflex sensitivity, which is proposed to be a predisposing factor for sudden death in patients with manifest cardiac disease. These studies have not evaluated the afferent and efferent components of the cardiac baroreflex loop or other baroreflex mechanisms that regulate target processes (cardiac metabolism and blood pressure variability) related to the impairment. The objective of this study was to gain more insight into autonomic functioning in depressive disorder to more fully examine the potential basis for increased cardiac mortality. METHODS: The subjects were 28 women and men with unipolar major depression who were taking antidepressant medications and who were in partial remission and free of cardiovascular or other serious disease, and 28 healthy control subjects matched for sex, age, and ethnicity. The two samples were compared for negative affective dispositions (anger expression, hostility, defensiveness, anxiety), spontaneous (closed-loop) baroreflex activity, heart rate, heart rate variability, systolic blood pressure, and heart rate-systolic blood pressure double product under resting conditions. RESULTS: Depressed patients showed a general disposition to anger suppression coupled with higher hostility and anxiety, and lower defensiveness. The patients showed higher general sympathetic activity (high levels of blood pressure, low-frequency heart rate variability) and lower parasympathetic-related activity (high heart rate and reduced high frequency heart rate variability) with affected cardiac metabolism estimated by the double product. Depressed patients had lower baroreflex sensitivity related to a higher gain of the afferent component of the baroreflex without respective gain adjustment of its efferent component (reflex gain 'de-afferentation'). It was coupled with a compensatory higher number of effective baroreflex reactions (reflex gating 're-afferentation'). Antidepressant agents and depressed mood had additional independent effects on baroreflex sensitivity through the efferent component of the cardiac baroreflex loop. CONCLUSIONS: The data indicate that different baroreflex components and mechanisms may be impaired in patients with depression and may contribute to their increased cardiac risk.

64 citations


Journal ArticleDOI
TL;DR: The data show that renal transplantation improves blood pressure and HRV and restores baroreflex function to near normal range on the long-term follow-up and these effects may contribute to the improvement of blood pressure control and survival after successful transplantation.
Abstract: Background. Renal transplantation improves the uraemic autonomic dysfunction and heart rate variability (HRV). The effects of successful transplantation on blood pressure variability (BPV) and baroreflex function are not well defined. Methods. BPV, HRV and baroreceptor indices were determined in (1) 52 non-diabetic chronic haemodialysis patients, (2) 44 transplanted patients, 24 in the first year after renal transplantation (≤I year) and 20 at least 1 year (>1 year) after renal transplantation, and (3) 41 control individuals with normal renal function, age-matched to (1) and (2). Power spectrum analysis of interbeat intervals (IBI) and systolic blood pressure (SBP) was performed in the low-frequency (LF 0.04-0.15 Hz) and the high-frequency (HF 0.15-0.40 Hz) bands. Spontaneous baroreceptor sensitivity (BRS) was determined by the sequence (slope) and spectral (a coefficient) techniques. Results. In haemodialysis patients, BPV was increased, while HRV, BRS slope and LF a and HF a coefficients were markedly decreased as compared to control individuals. Renal transplantation was associated with normalization of BPV at short term (≤1 year) and long term and with improvement of HRV at a long-term (> 1 year) follow-up. In patients with long-standing functioning grafts (>1 year), baroreceptor indices were significantly increased and returned to values similar to those of the control subjects. Conclusions. Our data show that renal transplantation improves blood pressure and HRV and restores baroreflex function to near normal range on the long-term follow-up. These effects may contribute to the improvement of blood pressure control and survival after successful transplantation.

33 citations


Journal ArticleDOI
TL;DR: The authors focus on the mechanisms of resistance to antihypertensive therapy (particularly for monotherapy with either angiotensin-converting enzyme inhibitors or angiotENSin II antagonists) in the treatment of diabetic hypertension.
Abstract: Resistance to antihypertensive drugs is common in hypertensive patients with type 2 diabetes. This is unfortunate because hypertension is one of the most important risk factors for development of cardiovascular events, and the goal blood pressure level is set lower in diabetic subjects than in nondiabetic subjects. Previous outcome trials in diabetic subjects have mainly focused on end points such as microalbuminuria or the incidence of cardiovascular events rather than on reduction of blood pressure; some reports, however, have suggested mechanisms for the drug resistance. These include several clinical conditions known to be associated with difficulty in reducing blood pressure specifically in diabetes mellitus: change in the renin-angiotensin system and chymase, volume overload, central sympathetic hyperactivity, sleep apnea, secondary hypertension, pseudoresistance (white coat hypertension), and poor compliance related to subclinical depression. In this review, the authors focus on the mechanisms of resistance to antihypertensive therapy (particularly for monotherapy with either angiotensin-converting enzyme inhibitors or angiotensin II antagonists) in the treatment of diabetic hypertension.

15 citations


Journal ArticleDOI
TL;DR: Findings indicate the sit-to-stand method is a statistically reliable BRS assessment tool and suitable for the examination of baroreflex hysteresis.
Abstract: Baroreflex assessment has diagnostic and prognostic utility in the clinical and research environments, and there is a need for a reliable, simple, noninvasive method of assessment. The repeated sit...

13 citations


Cites methods from "How to measure baroreflex sensitivi..."

  • ...Directional BRS for all three methods were calculated using the same approach, also described by others (24, 41)....

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References
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Journal ArticleDOI
TL;DR: An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.
Abstract: In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading. An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.

41,576 citations


Journal ArticleDOI
Abstract: Summary Background Experimental evidence suggests that autonomic markers such as heart-rate variability and baroreflex sensitivity (BRS) may contribute to post-infarction risk stratification. There are clinical data to support this concept for heart-rate variability. The main objective of the ATRAMI study was to provide prospective data on the additional and independent prognostic value for cardiac mortality of heart-rate variability and BRS in patients after myocardial infarction in whom left-ventricular ejection fraction (LVEF) and ventricular arrhythmias were known. Methods This multicentre international prospective study enrolled 1284 patients with a recent ( Findings During 21 (SD 8) months of follow-up, the primary endpoint, cardiac mortality, included 44 cardiac deaths and five non-fatal cardiac arrests. Low values of either heart-rate variability (SDNN 105 ms, BRS >6·1 ms per mm Hg). The association of low SDNN or BRS with LVEF below 35% carried a relative risk of 6·7 (3·1–14·6) or 8·7 (4·3–17·6), respectively, compared with patients with LVEF above 35% and less compromised SDNN (≥70 ms) and BRS (≥3 ms per mm Hg). Interpretation ATRAMI provides clinical evidence that after myocardial infarction the analysis of vagal reflexes has significant prognostic value independently of LVEF and of ventricular arrhythmias and that it significantly adds to the prognostic value of heart-rate variability.

2,816 citations


Journal ArticleDOI
TL;DR: It is concluded that the baroreceptor reflex are can be rapidly reset, particularly during sleep, and the lower arterial pressures during sleep may be actively maintained in some subjects by increased baroreflex sensitivity.
Abstract: The control of arterial pressure during sleep was studied in 13 untreated, unsedated subjects aged 20 to 46, including 7 with hypertension. Arterial pressure was measured directly. A transient rise of arterial pressure up to 30 mm Hg was produced by the sudden intravenous injection of 0.25 to 2 µg of angiotensin. Linear plots were obtained in 10 of 13 subjects when the systolic pressures of successive pulses during the pressure rise were plotted against the pulse intervals which began the next beat. The relationship was disturbed by movement or arousal, and was better when pulse intervals falling in inspiration were discarded. The slope of the line (milliseconds of cardiac slowing per millimeter rise in systolic pressure) in the awake subject ranged from 2 to 15.5 msec/mm Hg, and from 4.5 to 28.9 during sleep. Reflex sensitivity was highest in dreaming sleep. In 7 of 10 subjects, baroreflex sensitivity increased significantly during sleep; in 6, the prevailing arterial pressure was inversely correlated wi...

1,275 citations


"How to measure baroreflex sensitivi..." refers background in this paper

  • ...An increase in systemic arterial pressure increases the firing rate of baroreceptors which causes vagal excitation and sympathetic inhibition, thus decreasing heart rate; BRS can be quantified as the measure of the reflex bradycardia which follows the blood pressure rise induced by injection of an alpha-adrenoreceptor stimulant [2]....

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Journal ArticleDOI
TL;DR: Baroreceptor-induced slowing of heart rate in normal subjects was shown to be mediated by the parasympathetic nervous system since it could be abolished with atropine.
Abstract: To define the state of the parasympathetic nervous system in heart failure, parasympathetic blockade with atropine was induced after adrenergic blockade with propranolol in 12 normal subjects and in nine patients with heart disease. Atropine elevated heart rate by 55 ± 9 per cent in normal subjects, but by only 23 ± 8 per cent in patients with heart disease (p less than 0.05). In 23 control subjects and 22 patients, transient elevations in arterial pressure were produced by intravenous injections of phenylephrine, and successive R-R intervals were plotted as a function of systolic pressure. The slowing of heart rate per unit rise in systolic arterial pressure averaged 16.0 ±1.8 msec per millimeter of mercury in normal subjects but only 3.70 ± 0.8 msec per millimeter of mercury in the patients (p less than 0.001). Baroreceptor-induced slowing of heart rate in normal subjects was shown to be mediated by the parasympathetic nervous system since it could be abolished with atropine. These findings poi...

951 citations


"How to measure baroreflex sensitivi..." refers background in this paper

  • ...Cardiovascular disease may alter baroreceptor function, primarily because of a decreased capability to activate vagal reflexes [6]....

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Journal ArticleDOI
TL;DR: Beat-to-beat blood pressure recording via FINAPRES provides an accurate estimate of means and variability of radial blood pressure in groups of subjects and represents in most cases an acceptable alternative to invasive blood pressure monitoring during laboratory studies.
Abstract: The accuracy of blood pressure values obtained by continuous noninvasive finger blood pressure recording via the FINAPRES device was evaluated by comparison with simultaneous intraarterial monitoring both at rest and during performance of tests known to induce fast and often marked changes in blood pressure. The comparison was performed in 24 normotensive or essential hypertensive subjects. The average discrepancy between finger and intra-arterial blood pressure recorded over a 30-minute rest period was 6.5 +/- 2.6 mm Hg and 5.4 +/- 2.9 mm Hg for systolic and diastolic blood pressure, respectively; a close between-method correspondence was also demonstrated by linear regression analysis. The beat-to-beat changes in finger systolic and diastolic blood pressure were on average similar to those measured intra-arterially during tests that induced a pressor or depressor response (hand-grip, cold pressor test, diving test, Valsalva maneuver, intravenous injections of phenylephrine and trinitroglycerine) as well as during tests that caused vasomotor changes without major variations in blood pressure (application of lower body negative pressure, passive leg raising). The average between-method discrepancy in the evaluation of blood pressure changes was never greater than 4.3 and 2.0 mm Hg for systolic and diastolic blood pressure, respectively; the corresponding standard deviations ranged between 4.6 and 1.6 mm Hg. Beat-to-beat computer analysis of blood pressure variability over the 30-minute rest period provided standard deviations almost identical when calculated by separate consideration of intra-arterial and finger blood pressure tracings (3.7 and 3.8 mm Hg, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

934 citations


"How to measure baroreflex sensitivi..." refers methods in this paper

  • ...Estimates of BRS are very similar when SAP is measured directly from the radial or brachial artery or from a noninvasive pressure monitor [3, 4]....

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