Journal Article•
How to measure baroreflex sensitivity
TL;DR: The use of vasoactive drugs and the analysis of spontaneously occurring changes in blood pressure and heart rate are described.
Abstract: In 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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Dissertation•
01 Jan 2018
TL;DR: Thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy in Human Movement Science (Kinderkinetics) in the Faculty of Science and Agriculture at the University of Zululand, 2018.
Abstract: Thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy in Human Movement Science (Kinderkinetics)in the Faculty of Science and Agriculture at the University of Zululand, 2018.
4 citations
Cites background from "How to measure baroreflex sensitivi..."
...Atherosclerosis, 191(2), 447-453. https://doi.org/10.1016/j.atherosclerosis.2006.04.019. Kelly, G. A., Kelley, K. S., & Tran, Z. V. (2003). The effects of exercise on resting blood pressure in children and adolescents: A meta-analysis of randomized controlled trials....
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TL;DR: The effect of mechanoreflex activation overrides that of the cardiopulmonary baroreceptors loading resulting in decreased cardiac vagal outflow and reduced BRS during supine passive exercise.
Abstract: The effects of cardiopulmonary baroreceptors and muscle mechanoreceptors stimulation on cardiac baroreflex sensitivity (BRS), and heart rate variability (HRV) were evaluated by measuring continuously and non-invasively systolic blood pressure (SBP) and pulse interval (PI) during upright and supine passive cycling. BRS and HRV were evaluated with the cross-correlation method (xBRS) and in the frequency domain, respectively. At rest, the shift from upright to supine posture enhanced xBRS from 16.4+/-12.1 to 23.4+/-12.9 ms/mmHg, and the high frequency (HF, 0.15-0.4 Hz) power of HRV from 48.9+/-18.6 to 55.1+/-14.7 normalized units (NU), while it attenuated the low-frequency (LF, 0.04-0.15 Hz) power from 51.1+/-18.6 to 44.9+/-14.7 NU (P<0.05), respectively. During both upright and supine passive exercise, xBRS and the HF power were attenuated (10.0+/-8.0 and 12.5+/-9.0 ms/mmHg; 41.1+/-21.2 and 41.5+/-12.7 NU, respectively; P<0.05) and the LF power increased (58.8+/-21.2 and 58.5+/-12.7 NU, P<0.05), compared with rest. The effect of mechanoreflex activation overrides that of the cardiopulmonary baroreceptors loading resulting in decreased cardiac vagal outflow and reduced BRS during supine passive exercise.
3 citations
TL;DR: Cluster analysis of the BRS calculated for the spontaneous baroreflex at rest was used to distinguish three clusters of subjects (with high, medium, and low BRSs), which differed in the variability of the basic parameter and size and showed sex-related differences.
Abstract: The efficiency of baroreflex control depends on the baroreflex sensitivity (BRS), which is defined as the ratio of the change in the heart rate (HR) to the change in the blood pressure (BP). The BRS value may be used for assessing the autonomic control of the cardiovascular system and the degree of autonomic dysfunction. Until recently, the baroreflex had not been assessed in a large population of healthy subjects. In this study, the BRS was estimated by the ratio of the low-frequency component of the HR spectrum and the low-frequency component of the rhythm of the systolic BP. For assessing the arterial baroreflex in children, the BRSs for spontaneous and induced baroreflexes were compared. Sex-and age-related differences in BRS were found in 8-to-11-year-old children, and correlations between BRS and some spectral components of HR variability (HRV) and BP rhythm variability were determined. Cluster analysis of the BRS calculated for the spontaneous baroreflex at rest was used to distinguish three clusters of subjects (with high, medium, and low BRSs). These clusters differed in the variability of the basic parameter and size and showed sex-related differences.
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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.
43,884 citations
TL;DR: The ATRAMI study as discussed by the authors provides clinical evidence that after myocardial infarction the analysis of vagal reflexes has significant prognostic value independently of LVEF and ventricular arrhythmias and that it significantly adds to the prognosis value of heartrate variability.
2,950 citations
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...
1,297 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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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...
963 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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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)
945 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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