Limits...
Calibration of baroreflex equilibrium diagram based on exogenous pressor agents in chronic heart failure rats.

Kawada T, Li M, Sata Y, Zheng C, Turner MJ, Shimizu S, Sugimachi M - Clin Med Insights Cardiol (2015)

Bottom Line: The maximum slope of the dose-effect curve was significantly smaller in the CHF group than in the NC group (57.3 ± 5.2 vs 80.9 ± 6.3 mmHg/decade for phenylephrine, 60.2 ± 7.8 vs 80.4 ± 5.9 mmHg/decade for NE; P < 0.01).The CHF/NC ratio of the maximum slope was used to calibrate SNA.Plasma NE concentration in the CHF group could be disproportionally high relative to SNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan.

ABSTRACT
A baroreflex equilibrium diagram describes the relation between input pressure and sympathetic nerve activity (SNA) and that between SNA and arterial pressure (AP). To calibrate the SNA axis (abscissa) of the baroreflex equilibrium diagram, the AP response to intravenous bolus injections of phenylephrine (0.2-50 μg/kg) or norepinephrine (NE, 0.02-5 μg/kg) was examined in normal control rats (NC, n = 9) and rats with chronic heart failure (CHF, n = 6). The maximum slope of the dose-effect curve was significantly smaller in the CHF group than in the NC group (57.3 ± 5.2 vs 80.9 ± 6.3 mmHg/decade for phenylephrine, 60.2 ± 7.8 vs 80.4 ± 5.9 mmHg/decade for NE; P < 0.01). The CHF/NC ratio of the maximum slope was used to calibrate SNA. While the calibrated baroreflex equilibrium diagram showed increased maximum SNA and operating-point SNA in CHF rats compared with NC rats, the magnitude of increase was smaller than that expected from the excess plasma NE concentration in CHF rats. Plasma NE concentration in the CHF group could be disproportionally high relative to SNA.

No MeSH data available.


Related in: MedlinePlus

(A) Baroreflex equilibrium diagrams of normal control (NC) and chronic heart failure (CHF) constructed using mean parameter values of the neural and peripheral arcs in our previous study.16 In the neural arc of NC, the response range of SNA is 66.2%, the slope coefficient is 0.13 mmHg−1, the midpoint input pressure is 130.8 mmHg, and the lower plateau of SNA is 39.4%. In the peripheral arc of NC, the slope is 1.03 mmHg/% and the intercept is 29.3 mmHg. In the neural arc of CHF, the response range is 33.1%, the slope coefficient is 0.16 mmHg−1, the midpoint input pressure is 118.1 mmHg, and the lower plateau of SNA is 69.2%. In the peripheral arc of CHF, the slope is 0.78 mmHg/% and the intercept is 37.5 mmHg. (B) Baroreflex equilibrium diagrams of NC and CHF when the SNA axis for the CHF group was scaled so that the slope of the peripheral arc in CHF relative to that in NC became 0.6.Notes: Solid arrows indicate the operating point in NC. Dashed arrows indicate the operating point in CHF.Abbreviations: AP, arterial pressure; au, arbitrary units; BRP, baroreceptor pressure; SNA, sympathetic nerve activity.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4319654&req=5

f5-cmc-suppl.1-2015-001: (A) Baroreflex equilibrium diagrams of normal control (NC) and chronic heart failure (CHF) constructed using mean parameter values of the neural and peripheral arcs in our previous study.16 In the neural arc of NC, the response range of SNA is 66.2%, the slope coefficient is 0.13 mmHg−1, the midpoint input pressure is 130.8 mmHg, and the lower plateau of SNA is 39.4%. In the peripheral arc of NC, the slope is 1.03 mmHg/% and the intercept is 29.3 mmHg. In the neural arc of CHF, the response range is 33.1%, the slope coefficient is 0.16 mmHg−1, the midpoint input pressure is 118.1 mmHg, and the lower plateau of SNA is 69.2%. In the peripheral arc of CHF, the slope is 0.78 mmHg/% and the intercept is 37.5 mmHg. (B) Baroreflex equilibrium diagrams of NC and CHF when the SNA axis for the CHF group was scaled so that the slope of the peripheral arc in CHF relative to that in NC became 0.6.Notes: Solid arrows indicate the operating point in NC. Dashed arrows indicate the operating point in CHF.Abbreviations: AP, arterial pressure; au, arbitrary units; BRP, baroreceptor pressure; SNA, sympathetic nerve activity.

Mentions: The ultimate goal of the arterial baroreflex is to maintain perfusion for vital organs via regulation of AP. While the SNA response to pharmacological pressure perturbation is frequently used to evaluate arterial baroreflex function,31,32 it does not allow the direct assessment of arterial baroreflex regulation of AP. The AP response to SNA needs to be combined with the SNA response to pressure perturbation to understand the total picture of arterial baroreflex function. The baroreflex equilibrium diagram is useful for describing changes in the baroreflex control of SNA and AP such as those induced by muscle mechanoreflex,9 electroacupuncture,11 head-up tilt,10,33 vagal nerve stimulation,34,35 and pharmacologic interventions.5,36 However, when we want to compare the baroreflex equilibrium diagram among different groups of subjects, quantification of SNA becomes problematic. In a previous study, open-loop characteristics of the carotid sinus baroreflex were examined in NC rats and rats with CHF eight weeks postmyocardial infarction; the duration after myocardial infarction is the same as that in the present study.16Figure 5A presents the baroreflex equilibrium diagram constructed using mean parameter values of the neural and peripheral arcs obtained from that study.16 The slope of the peripheral arc in the CHF group was reduced to approximately 0.76 times that in the NC group. The operating-point SNA and AP in the NC group were 89.8% and 121.8 mmHg, respectively (solid arrows). The operating-point SNA and AP in CHF rats were 94.2% and 111.0 mmHg, respectively (dashed arrows). Although the SNA level at the operating point was higher in CHF rats than in NC rats, the difference was very small, casting doubt on the utility of the baroreflex equilibrium diagram for describing sympathetic hyperactivity in CHF rats compared with NC rats when SNA is expressed in percentage units.


Calibration of baroreflex equilibrium diagram based on exogenous pressor agents in chronic heart failure rats.

Kawada T, Li M, Sata Y, Zheng C, Turner MJ, Shimizu S, Sugimachi M - Clin Med Insights Cardiol (2015)

(A) Baroreflex equilibrium diagrams of normal control (NC) and chronic heart failure (CHF) constructed using mean parameter values of the neural and peripheral arcs in our previous study.16 In the neural arc of NC, the response range of SNA is 66.2%, the slope coefficient is 0.13 mmHg−1, the midpoint input pressure is 130.8 mmHg, and the lower plateau of SNA is 39.4%. In the peripheral arc of NC, the slope is 1.03 mmHg/% and the intercept is 29.3 mmHg. In the neural arc of CHF, the response range is 33.1%, the slope coefficient is 0.16 mmHg−1, the midpoint input pressure is 118.1 mmHg, and the lower plateau of SNA is 69.2%. In the peripheral arc of CHF, the slope is 0.78 mmHg/% and the intercept is 37.5 mmHg. (B) Baroreflex equilibrium diagrams of NC and CHF when the SNA axis for the CHF group was scaled so that the slope of the peripheral arc in CHF relative to that in NC became 0.6.Notes: Solid arrows indicate the operating point in NC. Dashed arrows indicate the operating point in CHF.Abbreviations: AP, arterial pressure; au, arbitrary units; BRP, baroreceptor pressure; SNA, sympathetic nerve activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4319654&req=5

f5-cmc-suppl.1-2015-001: (A) Baroreflex equilibrium diagrams of normal control (NC) and chronic heart failure (CHF) constructed using mean parameter values of the neural and peripheral arcs in our previous study.16 In the neural arc of NC, the response range of SNA is 66.2%, the slope coefficient is 0.13 mmHg−1, the midpoint input pressure is 130.8 mmHg, and the lower plateau of SNA is 39.4%. In the peripheral arc of NC, the slope is 1.03 mmHg/% and the intercept is 29.3 mmHg. In the neural arc of CHF, the response range is 33.1%, the slope coefficient is 0.16 mmHg−1, the midpoint input pressure is 118.1 mmHg, and the lower plateau of SNA is 69.2%. In the peripheral arc of CHF, the slope is 0.78 mmHg/% and the intercept is 37.5 mmHg. (B) Baroreflex equilibrium diagrams of NC and CHF when the SNA axis for the CHF group was scaled so that the slope of the peripheral arc in CHF relative to that in NC became 0.6.Notes: Solid arrows indicate the operating point in NC. Dashed arrows indicate the operating point in CHF.Abbreviations: AP, arterial pressure; au, arbitrary units; BRP, baroreceptor pressure; SNA, sympathetic nerve activity.
Mentions: The ultimate goal of the arterial baroreflex is to maintain perfusion for vital organs via regulation of AP. While the SNA response to pharmacological pressure perturbation is frequently used to evaluate arterial baroreflex function,31,32 it does not allow the direct assessment of arterial baroreflex regulation of AP. The AP response to SNA needs to be combined with the SNA response to pressure perturbation to understand the total picture of arterial baroreflex function. The baroreflex equilibrium diagram is useful for describing changes in the baroreflex control of SNA and AP such as those induced by muscle mechanoreflex,9 electroacupuncture,11 head-up tilt,10,33 vagal nerve stimulation,34,35 and pharmacologic interventions.5,36 However, when we want to compare the baroreflex equilibrium diagram among different groups of subjects, quantification of SNA becomes problematic. In a previous study, open-loop characteristics of the carotid sinus baroreflex were examined in NC rats and rats with CHF eight weeks postmyocardial infarction; the duration after myocardial infarction is the same as that in the present study.16Figure 5A presents the baroreflex equilibrium diagram constructed using mean parameter values of the neural and peripheral arcs obtained from that study.16 The slope of the peripheral arc in the CHF group was reduced to approximately 0.76 times that in the NC group. The operating-point SNA and AP in the NC group were 89.8% and 121.8 mmHg, respectively (solid arrows). The operating-point SNA and AP in CHF rats were 94.2% and 111.0 mmHg, respectively (dashed arrows). Although the SNA level at the operating point was higher in CHF rats than in NC rats, the difference was very small, casting doubt on the utility of the baroreflex equilibrium diagram for describing sympathetic hyperactivity in CHF rats compared with NC rats when SNA is expressed in percentage units.

Bottom Line: The maximum slope of the dose-effect curve was significantly smaller in the CHF group than in the NC group (57.3 ± 5.2 vs 80.9 ± 6.3 mmHg/decade for phenylephrine, 60.2 ± 7.8 vs 80.4 ± 5.9 mmHg/decade for NE; P < 0.01).The CHF/NC ratio of the maximum slope was used to calibrate SNA.Plasma NE concentration in the CHF group could be disproportionally high relative to SNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan.

ABSTRACT
A baroreflex equilibrium diagram describes the relation between input pressure and sympathetic nerve activity (SNA) and that between SNA and arterial pressure (AP). To calibrate the SNA axis (abscissa) of the baroreflex equilibrium diagram, the AP response to intravenous bolus injections of phenylephrine (0.2-50 μg/kg) or norepinephrine (NE, 0.02-5 μg/kg) was examined in normal control rats (NC, n = 9) and rats with chronic heart failure (CHF, n = 6). The maximum slope of the dose-effect curve was significantly smaller in the CHF group than in the NC group (57.3 ± 5.2 vs 80.9 ± 6.3 mmHg/decade for phenylephrine, 60.2 ± 7.8 vs 80.4 ± 5.9 mmHg/decade for NE; P < 0.01). The CHF/NC ratio of the maximum slope was used to calibrate SNA. While the calibrated baroreflex equilibrium diagram showed increased maximum SNA and operating-point SNA in CHF rats compared with NC rats, the magnitude of increase was smaller than that expected from the excess plasma NE concentration in CHF rats. Plasma NE concentration in the CHF group could be disproportionally high relative to SNA.

No MeSH data available.


Related in: MedlinePlus