scholarly journals Computational model-based assessment of baroreflex function from response to Valsalva maneuver

2018 ◽  
Vol 125 (6) ◽  
pp. 1944-1967 ◽  
Author(s):  
Samuel A. Kosinski ◽  
Brian E. Carlson ◽  
Scott L. Hummel ◽  
Robert D. Brook ◽  
Daniel A. Beard
Keyword(s):  
Heart Rate ◽  
Response Time ◽  
Baroreflex Sensitivity ◽  
Valsalva Maneuver ◽  
Human Subjects ◽  
Systolic Pressure ◽  
Linear Filter ◽  
Baroreflex Function ◽  
Physiologically Based ◽  
Physiologically Based Model

Functional metrics of autonomic control of heart rate, including baroreflex sensitivity, have been shown to be strongly associated with cardiovascular risk. A decrease in baroreflex sensitivity with aging is hypothesized to represent a contributing causal factor in the etiology of primary hypertension. To assess baroreflex function in human subjects, two complementary methods to simulate the response in heart rate elicited by the Valsalva maneuver were developed and applied to data obtained from a cohort of healthy normal volunteers. The first method is based on representing the baroreflex arc as a simple linear filter, transforming changes in arterial pressure to changes in R-R interval. The second method invokes a physiologically based model for arterial mechanics, afferent baroreceptor strain-dependent firing, and control of heart rate via central autonomic response to changes in afferent inputs from aortic and carotid sensors. Analysis based on the linear filter model reveals that the effective response time of the baroreflex arc tends to increase with age in healthy subjects and that the response time/response rate is a predictor of resting systolic pressure. Similar trends were obtained based on the physiologically based model. Analysis of the Valsalva response using the physiologically based model further reveals that different afferent inputs from the carotid sinus and the aortic arch baroreceptors govern different parts of the heart rate response. The observed relationship between baroreflex sensitivity and systolic pressure is surprising because hypertensive subjects were excluded from the study, and there was no observed relationship between arterial pressure and age. NEW & NOTEWORTHY We introduce two methods to assess baroreflex function from data recorded from human subjects performing the Valsalva maneuver. Results demonstrate that the baroreflex response time tends to increase with age in healthy subjects, that response time represents a predictor of resting systolic pressure, and that the Valsalva response reveals different effects mediated by baroreceptors in the carotid sinus compared with those in the aortic arch.

Heart rate variability and baroreflex sensitivity are reduced in chronically undernourished, but otherwise healthy, human subjects

2003 ◽  
Vol 104 (3) ◽  
pp. 295-302 ◽  
Author(s):  
Mario VAZ ◽  
A.V. BHARATHI ◽  
S. SUCHARITA ◽  
D. NAZARETH
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
High Frequency ◽  
Baroreflex Sensitivity ◽  
Human Subjects ◽  
Normal Weight ◽  
Autonomic Nerve ◽  
Total Power ◽  
Healthy Human ◽  
Frequency Power

Alterations in autonomic nerve activity in subjects in a chronically undernourished state have been proposed, but have been inadequately documented. The present study evaluated heart rate and systolic blood pressure variability in the frequency domain in two underweight groups, one of which was undernourished and recruited from the lower socio-economic strata [underweight, undernourished (UW/UN); n = 15], while the other was from a high class of socio-economic background [underweight, well nourished (UW/WN); n = 17], as well as in normal-weight controls [normal weight, well nourished (NW/WN); n = 27]. Baroreflex sensitivity, which is a determinant of heart rate variability, was also assessed. The data indicate that total power (0–0.4Hz), low-frequency power (0.04–0.15Hz) and high-frequency power (0.15–0.4Hz) of RR interval variability were significantly lower in the UW/UN subjects (P<0.05) than in the NW/WN controls when expressed in absolute units, but not when the low- and high-frequency components were normalized for total power. Baroreflex sensitivity was similarly lower in the UW/UN group (P<0.05). Heart rate variability parameters in the UW/WN group were generally between those of the UW/UN and NW/WN groups, but were not statistically different from either. The mechanisms that contribute to the observed differences between undernourished and normal-weight groups, and the implications of these differences, remain to be elucidated.

Estrogen enhances baroreflex control of heart rate in conscious ovariectomized rats

1998 ◽  
Vol 76 (4) ◽  
pp. 381-386 ◽  
Author(s):  
Mahmoud M El-Mas ◽  
Abdel A Abdel-Rahman
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Baroreflex Sensitivity ◽  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
Baroreflex Function ◽  
Vehicle Treatment

In previous studies, we have shown that the baroreflex control of heart rate is significantly attenuated in females compared with age-matched males. This study investigated the role of estrogen in the modulation of baroreflex function in conscious unrestrained rats. Baroreflex-mediated decreases in heart rate in response to increments in blood pressure evoked by phenylephrine were evaluated in conscious freely moving male and female Sprague-Dawley rats as well as in ovariectomized rats. The effect of a 2-day 17 beta -estradiol (50 µg ·kg-1 ·day-1, s.c.) or vehicle treatment on baroreflex sensitivity was investigated in ovariectomized rats. Intravenous bolus doses of phenylephrine (1-16 µg/kg) elicited dose-dependent pressor and bradycardic responses in all groups of rats. Regression analysis of the baroreflex curves relating increments in blood pressure to the associated heart rate responses revealed a significantly (p < 0.05) smaller baroreflex sensitivity in female compared with male rats (-1.22 ± 0.07 and -1.85 ± 0.15 beats ·min-1 ·mmHg-1, respectively), suggesting an attenuated baroreflex function in females. In age-matched ovariectomized rats, baroreflex sensitivity showed further reduction (-0.93 ± 0.02 beats ·min-1 ·mmHg-1). Treatment of ovariectomized rats with 17 beta -estradiol significantly (p < 0.05) enhanced the baroreflex sensitivity (-1.41 ± 0.16 beats ·min-1 ·mmHg-1) to a level that was slightly higher than that of sham-operated female rats. Furthermore, baroreflex sensitivity of ovariectomized estradiol-treated rats was not significantly different from that of age-matched male rats. The vehicle, on the other hand, had no effect on baroreflex sensitivity of ovariectomized rats. These data support our earlier findings that sexual dimorphism exists in baroreflex control of heart rate. More importantly, the present study provides experimental evidence that suggests a facilitatory role for estrogen in the modulation of baroreflex function.Key words: rat, gender, baroreflex sensitivity, 17 beta -estradiol, ovariectomy.

Muscle metaboreflex attenuates spontaneous heart rate baroreflex sensitivity during dynamic exercise

2007 ◽  
Vol 292 (6) ◽  
pp. H2867-H2873 ◽  
Author(s):  
Javier A. Sala-Mercado ◽  
Masashi Ichinose ◽  
Robert L. Hammond ◽  
Tomoko Ichinose ◽  
Marco Pallante ◽  
...  
Keyword(s):  
Heart Rate ◽  
Exercise Intensity ◽  
Baroreflex Sensitivity ◽  
Pressor Response ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Dynamic Exercise ◽  
Moderate Exercise ◽  
Ventricular Systolic Pressure ◽  
Muscle Metaboreflex

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Dynamic exercise attenuates spontaneous baroreflex sensitivity (SBRS) in the control of heart rate (HR) during rapid, spontaneous changes in blood pressure (BP). Our objective was to determine whether muscle metaboreflex activation (MRA) further diminishes SBRS. Conscious dogs were chronically instrumented for measurement of HR, cardiac output, mean arterial pressure, and left ventricular systolic pressure (LVSP) at rest and during mild (3.2 km/h) or moderate (6.4 km/h at 10% grade) dynamic exercise before and after MRA (via partial reduction of hindlimb blood flow). SBRS was evaluated as the slopes of the linear relations (LRs) between HR and LVSP during spontaneous sequences of at least three consecutive beats when HR changed inversely vs. pressure (expressed as beats·min−1·mmHg−1). During mild exercise, these LRs shifted upward, with a significant decrease in SBRS (−3.0 ± 0.4 vs. −5.2 ± 0.4, P < 0.05 vs. rest). MRA shifted LRs upward and rightward and decreased SBRS (−2.1 ± 0.1, P < 0.05 vs. mild exercise). Moderate exercise shifted LRs upward and rightward and significantly decreased SBRS (−1.2 ± 0.1, P < 0.05 vs. rest). MRA elicited further upward and rightward shifts of the LRs and reductions in SBRS (−0.9 ± 0.1, P < 0.05 vs. moderate exercise). We conclude that dynamic exercise resets the arterial baroreflex to higher BP and HR as exercise intensity increases. In addition, increases in exercise intensity, as well as MRA, attenuate SBRS.

scholarly journals Endogenous leptin contributes to baroreflex suppression within the solitary tract nucleus of aged rats

2014 ◽  
Vol 307 (11) ◽  
pp. H1539-H1546 ◽  
Author(s):  
Amy C. Arnold ◽  
Debra I. Diz
Keyword(s):  
Heart Rate ◽  
Receptor Antagonist ◽  
Baroreflex Sensitivity ◽  
Leptin Receptor ◽  
Solitary Tract Nucleus ◽  
Aged Rats ◽  
Solitary Tract ◽  
Sprague Dawley ◽  
Baroreflex Function ◽  
Sprague Dawley Rats

The decline in cardiovagal baroreflex function that occurs with aging is accompanied by an increase in circulating leptin levels. Our previous studies showed that exogenous leptin impairs the baroreflex sensitivity for control of heart rate in younger rats, but the contribution of this hormone to baroreflex dysfunction during aging is unknown. Thus we assessed the effect of bilateral leptin microinjection (500 fmol/60 nl) within the solitary tract nucleus (NTS) on the baroreflex sensitivity in older (66 ± 2 wk of age) urethane/chloralose anesthetized Sprague-Dawley rats with elevated circulating leptin levels. In contrast to the 63% reduction observed in younger rats, leptin did not alter the baroreflex sensitivity for bradycardia evoked by phenylephrine in older rats (0.76 ± 0.19 baseline vs. 0.71 ± 0.15 ms/mmHg after leptin; P = 0.806). We hypothesized that this loss of sensitivity reflected endogenous suppression of the baroreflex by elevated leptin, rather than cardiovascular resistance to the peptide. Indeed, NTS administration of a leptin receptor antagonist (75 pmol/120 nl) improved the baroreflex sensitivity for bradycardia in older rats (0.73 ± 0.13 baseline vs. 1.19 ± 0.26 at 10 min vs. 1.87 ± 0.32 at 60 min vs. 1.22 ± 0.54 ms/mmHg at 120 min; P = 0.002), with no effect in younger rats. There was no effect of the leptin antagonist on the baroreflex sensitivity for tachycardia, responses to cardiac vagal chemosensitive fiber activation, or resting hemodynamics in older rats. These findings suggest that the actions of endogenous leptin within the NTS, either produced locally or derived from the circulation, contribute to baroreflex suppression during aging.

Cardiovagal Reflexes

2009 ◽  
pp. 661-676
Author(s):  
William P. Cheshire
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Phase Ii ◽  
Heart Rate Response ◽  
Valsalva Maneuver ◽  
Human Subjects ◽  
Simultaneous Recording ◽  
Deep Breathing ◽  
Noninvasive Technique ◽  
Phase Iv

Noninvasive cardiovascular tests are reliable and reproducible and are widely used to evaluate autonomic function in human subjects. The heart rate response to deep breathing is probably the most reliable test for assessing the integrity of the vagal afferent and efferent pathways to the heart. This is because respiratory sinus arrhythmia is a relatively pure test of cardiovagal function, whereas many other conditions, such as plasma volume, antecedent rest, and cardiac and peripheral sympathetic functions, factor into the Valsalva response. Heart rate variability to deep breathing is usually tested at a breathing frequency of 5 or 6 respirations per minute and decreases linearly with age. The Valsalva maneuver consists of a forced expiratory effort against resistance and produces mechanical (phases I and III) and reflex (phases II and IV) changes in arterial pressure and heart rate. When performed under continuous arterial pressure monitoring with a noninvasive technique, the Valsalva maneuver provides valuable information about the integrity of the cardiac parasympathetic, cardiac sympathetic, and sympathetic vasomotor outputs. The responses to the Valsalva maneuver are affected by the position of the subject and the magnitude and duration of the expiratory effort. In general, it is performed at an expiratory pressure of 40 mm Hg sustained for 15 seconds. The Valsalva ratio, the relationship between the maximal heart rate response during phase II (straining) and phase IV (after release of straining), has been considered a test of cardiac parasympathetic function. However, without simultaneous recording of arterial pressure, this may be misleading. An exaggerated decrease in arterial pressure during phase II suggests sympathetic vasomotor failure, whereas an absence of overshoot during phase IV indicates the inability to increase cardiac output and cardiac adrenergic failure.

Acute manipulations of plasma volume alter arterial pressure responses during Valsalva maneuvers

1999 ◽  
Vol 86 (6) ◽  
pp. 1852-1857 ◽  
Author(s):  
Janice M. Fritsch-Yelle ◽  
Victor A. Convertino ◽  
Todd T. Schlegel
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Phase Ii ◽  
Plasma Volume ◽  
Diastolic Pressure ◽  
Valsalva Maneuver ◽  
Isotonic Saline ◽  
Systolic Pressure ◽  
Cardiovascular Responses ◽  
Phase Iii

The effects of changes in blood volume on arterial pressure patterns during the Valsalva maneuver are incompletely understood. In the present study we measured beat-to-beat arterial pressure and heart rate responses to supine Valsalva maneuvers during normovolemia, hypovolemia induced with intravenous furosemide, and hypervolemia induced with ingestion of isotonic saline. Valsalva responses were analyzed according to the four phases as previously described (W. F. Hamilton, R. A. Woodbury, and H. T. Harper, Jr. JAMA 107: 853–856, 1936; W. F. Hamilton, R. A. Woodbury, and H. T. Harper, Jr. Am. J. Physiol. 141: 42–50, 1944). Phase I is the initial onset of straining, which elicits a rise in arterial pressure; phase II is the period of straining, during which venous return is impeded and pressure falls (early) and then partially recovers (late); phase III is the initial release of straining; and phase IV consists of a rapid “overshoot” of arterial pressure after the release. During hypervolemia, early phase II arterial pressure decreases were significantly less than those during hypovolemia, thus making the response more “square.” Systolic pressure hypervolemic vs. hypovolemic falls were −7.4 ± 2.1 vs. −30.7 ± 7 mmHg ( P = 0.005). Diastolic pressure hypervolemic vs. hypovolemic falls were −2.4 ± 1.6 vs. −15.2 ± 2.6 mmHg ( P = 0.05). A significant direct correlation was found between plasma volume and phase II systolic pressure falls, and a significant inverse correlation was found between plasma volume and phase III-IV systolic pressure overshoots. Heart rate responses to systolic pressure falls during phase II were significantly less during hypovolemia than during hypervolemia (0.7 ± 0.2 vs. 2.82 ± 0.2 beats ⋅ min−1 ⋅ mmHg−1; P = 0.05) but were not different during phase III-IV overshoots. We conclude that acute changes in intravascular volume from hypovolemia to hypervolemia affect cardiovascular responses, particularly arterial pressure changes, to the Valsalva maneuver and should be considered in both clinical and research applications of this maneuver.

Alterations of postural and Valsalva responses in coronary heart disease

1977 ◽  
Vol 233 (6) ◽  
pp. H694-H699 ◽  
Author(s):  
F. E. Tristani ◽  
D. G. Kamper ◽  
D. J. McDermott ◽  
B. J. Peters ◽  
J. J. Smith
Keyword(s):  
Heart Rate ◽  
Coronary Heart Disease ◽  
Heart Disease ◽  
Diastolic Pressure ◽  
Valsalva Maneuver ◽  
Systolic Pressure ◽  
Impedance Method ◽  
Normal Male ◽  
Control Subjects ◽  
Coronary Patients

Patients in congestive heart failure are known to have altered autonomic responses to circulatory stress. In this study, two different age groups of male coronary heart disease (CHD) patients, not in failure, as well as normal male subjects, underwent standard 20-min 70 degrees head-up tilt and Valsalva tests. Responses were monitored by noninvasive methods and cardiac output was estamated with a transthoracic impedance method. During tilt, the CHD patients and control subjects had similar heart rate and diastolic pressure responses. However, the CHD patients had a greater decline in pulse pressure during tilt, mainly due to a decrease in systolic pressure. CHD patients had lesser declines in stroke volume and cardiac index and lesser increases in total vascular resistance than did control subjects. In the Valsalva, the heart rate phase increments (and decrements) from control and rate increments (and decrements) between successive phases were less in the coronary patients. The results indicate that coronary patients, not in failure, have diminished circulatory responses to the tilt and Valsalva maneuver and suggest that these tests may be useful functional indices of cardiovascular capability in coronary disease.

scholarly journals Assessment of Baroreflex Sensitivity Using Time-Frequency Analysis during Postural Change and Hypercapnia

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Agnieszka Kazimierska ◽  
Michał M. Placek ◽  
Agnieszka Uryga ◽  
Paweł Wachel ◽  
Małgorzata Burzyńska ◽  
...  
Keyword(s):  
Heart Rate ◽  
Neural Control ◽  
Baroreflex Sensitivity ◽  
Systolic Pressure ◽  
Pulse Interval ◽  
Postural Change ◽  
Short Term ◽  
Time Frequency ◽  
Arterial Blood ◽  
The Relationship

Baroreflex is a mechanism of short-term neural control responsible for maintaining stable levels of arterial blood pressure (ABP) in an ABP-heart rate negative feedback loop. Its function is assessed by baroreflex sensitivity (BRS)—a parameter which quantifies the relationship between changes in ABP and corresponding changes in heart rate (HR). The effect of postural change as well as the effect of changes in blood O2 and CO2 have been the focus of multiple previous studies on BRS. However, little is known about the influence of the combination of these two factors on dynamic baroreflex response. Furthermore, classical methods used for BRS assessment are based on the assumption of stationarity that may lead to unreliable results in the case of mostly nonstationary cardiovascular signals. Therefore, we aimed to investigate BRS during repeated transitions between squatting and standing in normal end-tidal CO2 (EtCO2) conditions (normocapnia) and conditions of progressively increasing EtCO2 with a decreasing level of O2 (hypercapnia with hypoxia) using joint time and frequency domain (TF) approach to BRS estimation that overcomes the limitation of classical methods. Noninvasive continuous measurements of ABP and EtCO2 were conducted in a group of 40 healthy young volunteers. The time course of BRS was estimated from TF representations of pulse interval variability and systolic pressure variability, their coherence, and phase spectra. The relationship between time-variant BRS and indices of ABP and HR was analyzed during postural change in normocapnia and hypercapnia with hypoxia. In normocapnia, observed trends in all measures were in accordance with previous studies, supporting the validity of presented TF method. Similar but slightly attenuated response to postural change was observed in hypercapnia with hypoxia. Our results show the merits of the nonstationary methods as a tool to study the cardiovascular system during short-term hemodynamic changes.

Arterial baroreflex control of heart rate during exercise in postural tachycardia syndrome

2007 ◽  
Vol 103 (4) ◽  
pp. 1136-1142 ◽  
Author(s):  
Shizue Masuki ◽  
John H. Eisenach ◽  
William G. Schrage ◽  
Niki M. Dietz ◽  
Christopher P. Johnson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Baroreflex Sensitivity ◽  
Systolic Pressure ◽  
Upright Position ◽  
Postural Tachycardia Syndrome ◽  
Healthy Controls ◽  
Arterial Baroreflex ◽  
Cycle Exercise ◽  
Baroreflex Control ◽  
Postural Tachycardia

Patients with postural tachycardia syndrome (POTS) have excessive tachycardia without hypotension during orthostasis as well as exercise. We tested the hypothesis that excessive tachycardia during exercise in POTS is not related to abnormal baroreflex control of heart rate (HR). Patients ( n = 13) and healthy controls ( n = 10) performed graded cycle exercise at 25, 50, and 75 W in both supine and upright positions while arterial pressure (arterial catheter) and HR (ECG) were measured. Baroreflex sensitivity of HR was assessed by bolus intravenous infusion of phenylephrine at each workload. In both positions, HR was higher in the patients than the controls during exercise. Supine baroreflex sensitivity (HR/systolic pressure) in POTS patients was −1.3 ± 0.1 beats·min−1·mmHg−1 at rest and decreased to −0.6 ± 0.1 beats·min−1·mmHg−1 during 75-W exercise, neither significantly different from the controls ( P > 0.6). In the upright position, baroreflex sensitivity in POTS patients at rest (−1.4 ± 0.1 beats·min−1·mmHg−1) was higher than the controls (−1.0 ± 0.1 beats·min−1·mmHg−1) ( P < 0.05), and it decreased to −0.1 ± 0.04 beats·min−1·mmHg−1 during 75-W exercise, lower than the controls (−0.3 ± 0.09 beats·min−1·mmHg−1) ( P < 0.05). The reduced arterial baroreflex sensitivity of HR during upright exercise was accompanied by greater fluctuations in systolic and pulse pressure in the patients than in the controls with 56 and 90% higher coefficient of variations, respectively ( P < 0.01). However, when baroreflex control of HR was corrected for differences in HR, it was similar between the patients and controls during upright exercise. These results suggest that the tachycardia during exercise in POTS was not due to abnormal baroreflex control of HR.

Influence of menstrual cycle on baroreflex control of heart rate: comparison with male volunteers

2003 ◽  
Vol 285 (5) ◽  
pp. R1091-R1097 ◽  
Author(s):  
Makoto Tanaka ◽  
Masayoshi Sato ◽  
Shino Umehara ◽  
Toshiaki Nishikawa
Keyword(s):  
Heart Rate ◽  
Menstrual Cycle ◽  
Baroreflex Sensitivity ◽  
Valsalva Maneuver ◽  
Baroreflex Control ◽  
Linear Portion ◽  
Healthy Women ◽  
Male Volunteers ◽  
Plasma Estradiol ◽  
Spontaneous Fluctuations

This study was designed to determine baroreflex control of heart rate (HR) to hypotensive and hypertensive stimuli during the early follicular (EF), preovulation (PreOV), and midluteal (ML) phases of the menstrual cycle and to test the hypothesis that cardiovagal reflex responses to hypertensive stimuli would be altered depending on the plasma estradiol levels in healthy women. In addition, these results were compared with those of male volunteers. Fifteen healthy women with regular menstrual cycles and thirteen male volunteers were recruited. Cardiovagal baroreflex sensitivity was defined as the slope of the linear portion relating R-R interval and systolic blood pressure triggered by bolus injections of nitroprusside and phenylephrine, from the overshoot phase of the Valsalva maneuver, and during spontaneous fluctuations. Three measurements were averaged in each test as a representative at each phase, and the order of phases was counterbalanced. Baroreflex sensitivities by the phenylephrine pressor test and Valsalva maneuver during the PreOV phase were significantly greater than those during the EF and ML phases but were similar to those of men. Depressor test sensitivities by nitroprusside and down-sequence spontaneous cardiac baroreflex sensitivity during the EF phase were significantly greater than those of the ML phase and of men. Significant correlations were observed between plasma estradiol concentrations and baroreflex sensitivities assessed by phenylephrine and the Valsalva maneuver. Our results indicate that baroreflex control of HR is altered during the regular menstrual cycle, and estradiol appears to exert cardiovagal modulation in healthy women.

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