1
|
Cauwenberghs N, Tabassian M, Thijs L, Yang WY, Wei FF, Claus P, D'hooge J, Staessen JA, Kuznetsova T. Area of the pressure-strain loop during ejection as non-invasive index of left ventricular performance: a population study. Cardiovasc Ultrasound 2019; 17:15. [PMID: 31382957 PMCID: PMC6683340 DOI: 10.1186/s12947-019-0166-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 07/29/2019] [Indexed: 01/08/2023] Open
Abstract
Background Previous studies highlighted the usefulness of integrating left ventricular (LV) deformation (strain) and hemodynamic parameters to quantify LV performance. In a population sample, we investigated the anthropometric and clinical determinants of a novel non-invasive index of LV systolic performance derived from simultaneous registration of LV strain and brachial pressure waveforms. Methods Three hundred fifty-six randomly recruited subjects (44.7% women; mean age, 53.9 years; 47.5% hypertensive) underwent echocardiographic and arterial data acquisition. We constructed pressure-strain loops from simultaneously recorded two-dimensional LV strain curves and brachial pressure waveforms obtained by finger applanation tonometry. We defined the area of this pressure-strain loop during ejection as LV ejection work density (EWD). We reported effect sizes as EWD changes associated with a 1-SD increase in covariables. Results In multivariable-adjusted analyses, higher EWD was associated with age, female sex and presence of hypertension (P ≤ 0.0084). In both men and women, EWD increased independently with augmentation pressure (effect size: + 59.1 Pa), central pulse pressure (+ 65.7 Pa) and pulse wave velocity (+ 44.8 Pa; P ≤ 0.0006). In men, EWD decreased with relative wall thickness (− 29.9 Pa) and increased with LV ejection fraction (+ 23.9 Pa; P ≤ 0.040). In women, EWD increased with left atrial (+ 76.2 Pa) and LV end-diastolic (+ 43.8 Pa) volume indexes and with E/e’ ratio (+ 51.1 Pa; P ≤ 0.026). Conclusion Older age, female sex and hypertension were associated with higher EWD. Integration of the LV pressure-strain loop during ejection might be a useful tool to non-invasively evaluate sex-specific and interdependent effects of preload and afterload on LV myocardial performance. Electronic supplementary material The online version of this article (10.1186/s12947-019-0166-y) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Nicholas Cauwenberghs
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Mahdi Tabassian
- Division of Cardiovascular Imaging and Dynamics, Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Lutgarde Thijs
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Wen-Yi Yang
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Fang-Fei Wei
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Piet Claus
- Division of Cardiovascular Imaging and Dynamics, Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Jan D'hooge
- Division of Cardiovascular Imaging and Dynamics, Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Jan A Staessen
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Tatiana Kuznetsova
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium.
| |
Collapse
|
2
|
Chang YT, Chang WN, Tsai NW, Huang CC, Wang HC, Kung CT, Su YJ, Lin WC, Chang HW, Cheng BC, Su CM, Chiang YF, Lu CH. Link between cerebral blood flow and autonomic function in survivors of internal carotid artery occlusion. J Neurol Sci 2015; 353:143-8. [PMID: 25956232 DOI: 10.1016/j.jns.2015.04.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/25/2015] [Accepted: 04/23/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE Symptomatic internal carotid artery occlusion (ICAO) is an important cause of cerebral ischemia with poor long-term outcome. Reductions in baroreflex function is reported in carotid atherosclerosis and implicated in increased risk of recurrent cardiovascular events. A distributed network of forebrain regions can exert modulatory influences over the cardio-vagal and baroreflex functions. The successful clinical translation of these approaches offers insights into underlying modulatory mechanisms and to possible therapeutic strategy. METHODS This study enrolled 20 symptomatic ICAO survivors, 20 patients with small vessel disease (SVD) as risk control, and 20 healthy controls. All underwent a standardized evaluation of cardiovascular autonomic function testing that included baroreflex sensitivity (BRS), Valsalva ratio (VR), and heart rate response to deep breathing (HR_DB). The regional cerebral blood flow (rCBF) of the central autonomic network (CAN) was obtained from arterial spin-labeling magnetic resonance imaging. Parameters of autonomic function between symptomatic ICAO survivors with and those without recurrent cardiovascular events were compared. RESULTS Valsalva ratio and HR_DB levels were significantly higher in the control group, followed by the SVD and ICAO groups (p=0.009 and p=0.007, respectively). Spontaneous BRS and BRS during the early phase II of Valsalva maneuver levels were both significantly higher in the control group, followed by the SVD and ICAO groups (p<0.001 and p=0.042, respectively). The rCBF of CAN inversely correlated with spontaneous BRS. CONCLUSION Autonomic dysregulation, including reduced BRS and impaired cardio-vagal function in the convalescent stage ICAO, can persist for a long time. Reduced BRS is inversely correlated with CAN activity.
Collapse
Affiliation(s)
- Ya-Ting Chang
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Wen-Neng Chang
- Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Nai-Wen Tsai
- Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Chih-Cheng Huang
- Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Hung-Chen Wang
- Department of Neurosurgery, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Chia-Te Kung
- Department of Emergency Medicine, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Yu-Jih Su
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Department of Medicine, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Wei-Che Lin
- Department of Radiology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Hsueh-Wen Chang
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan
| | - Ben-Chung Cheng
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Department of Medicine, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Chih-Min Su
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Department of Emergency Medicine, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Yi-Fang Chiang
- Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Cheng-Hsien Lu
- Department of Biological Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan; Department of Neurology, Xiamen Chang Gung Memorial Hospital, Xiamen, Fujian, China.
| |
Collapse
|
3
|
Evaluation of a model-based hemodynamic monitoring method in a porcine study of septic shock. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2013; 2013:505417. [PMID: 23585774 PMCID: PMC3621159 DOI: 10.1155/2013/505417] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/22/2013] [Accepted: 02/06/2013] [Indexed: 01/20/2023]
Abstract
INTRODUCTION The accuracy and clinical applicability of an improved model-based system for tracking hemodynamic changes is assessed in an animal study on septic shock. METHODS This study used cardiovascular measurements recorded during a porcine trial studying the efficacy of large-pore hemofiltration for treating septic shock. Four Pietrain pigs were instrumented and induced with septic shock. A subset of the measured data, representing clinically available measurements, was used to identify subject-specific cardiovascular models. These models were then validated against the remaining measurements. RESULTS The system accurately matched independent measures of left and right ventricle end diastolic volumes and maximum left and right ventricular pressures to percentage errors less than 20% (except for the 95th percentile error in maximum right ventricular pressure) and all R(2) > 0.76. An average decrease of 42% in systemic resistance, a main cardiovascular consequence of septic shock, was observed 120 minutes after the infusion of the endotoxin, consistent with experimentally measured trends. Moreover, modelled temporal trends in right ventricular end systolic elastance and afterload tracked changes in corresponding experimentally derived metrics. CONCLUSIONS These results demonstrate that this model-based method can monitor disease-dependent changes in preload, afterload, and contractility in porcine study of septic shock.
Collapse
|
4
|
Narayan J, Amatoury J, Verma M, Kairaitis K, Wheatley JR, Amis TC. Resetting the baroreflex during snoring: role of resistive loading and intra-thoracic pressure. Respir Physiol Neurobiol 2013; 185:489-96. [PMID: 23219813 DOI: 10.1016/j.resp.2012.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 11/15/2012] [Accepted: 11/19/2012] [Indexed: 12/20/2022]
Abstract
Baroreflex sensitivity (BRS) is reduced during snoring in humans and animal models. We utilised our rabbit model to examine the contribution of increased upper airway resistance to baroreflex resetting during snoring, by comparing BRS and baroreflex operating point (OP) values during IS to those obtained during tracheostomised breathing through an external resistive load (RL) titrated to match IS levels of peak inspiratory pleural pressure (Ppl). During both IS and RL, BRS decreased by 45% and 49%. There was a linear relationship between the change in Ppl and the decrease in BRS, which was similar for IS and RL. During both RL and IS, there was a shift in OP driven by ~16% increase in HR and no change in arterial pressure. Snoring related depression of BRS is likely mediated via a HR driven change in OP, which itself may be the outcome of negative intra-thoracic pressure mediated effects on right atrial wall stretch reflex control of heart rate.
Collapse
Affiliation(s)
- Jyotishna Narayan
- Ludwig Engel Centre for Respiratory Research, Department of Respiratory and Sleep Medicine, Sydney, NSW, Australia.
| | | | | | | | | | | |
Collapse
|
5
|
Abstract
This study was conducted to explore the vascular reactivity of angiotensin II and noradrenaline and their relationship with endothelial function in rabbits fed a high-fat diet (HFD). The animals were fed either an HFD or regular chow [control diet (CD)]. After 12 weeks, the rabbits fed the HFD showed higher blood pressure, body weight, and insulin levels. Glucose tolerance was impaired and positively related to blood pressure. An endothelium-independent decrease of the sensitivity to angiotensin II [pD2 endothelium-intact aortic rings (E+) in CD: 8.02 ± 0.07 vs. HFD: 7.60 ± 0.01; pD2 endothelium-removed aortic rings (E-) in CD: 8.16 ± 0.11 vs. HFD: 7.83 ± 0.16] and noradrenaline (pD2 E+ in CD: 6.36 ± 0.06 vs. HFD: 5.29 ± 0.06; pD2 E- in CD: 6.11 ± 0.08 vs. HFD: 5.80 ± 0.08) was found. Noradrenaline desensitized the angiotensin II response (pD2 with noradrenaline pretreatment in E+: 7.03 ± 0.16; in E-: 7.10 ± 0.02), but angiotensin II did not change the noradrenaline response. Acetylcholine maximal relaxation and basal nitric oxide (NO) release were comparable in both diet groups. The efficacy of angiotensin II (Rmax CD: 4604 ± 574 mg vs. HFD: 3251 ± 533 mg) and noradrenaline (Rmax CD: 11,675 ± 804 mg vs. HFD: 7975 ± 960 mg) was reduced in E+. L-N-nitroarginine methyl ester (L-NAME) recovered the efficacy of noradrenaline (Rmax L-NAME: 12,015 ± 317 mg). In contrast, L-NAME had no effect on the angiotensin II response. Noradrenaline enhanced NO levels, but angiotensin II did not. Therefore, NO was associated with hyporeactivity to noradrenaline. The resting potential was more negative in E+, and the endothelium diminished the angiotensin II-induced depolarization. These findings demonstrated that the crosstalk and the endothelium may induce hyporeactivity to angiotensin II and noradrenaline as a mechanism to compensate the increase in the blood pressure in HFD-induced obesity.
Collapse
|
6
|
Kuznetsova T, D'hooge J, Kloch-Badelek M, Sakiewicz W, Thijs L, Staessen JA. Impact of hypertension on ventricular-arterial coupling and regional myocardial work at rest and during isometric exercise. J Am Soc Echocardiogr 2012; 25:882-90. [PMID: 22622108 DOI: 10.1016/j.echo.2012.04.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Indexed: 12/31/2022]
Abstract
BACKGROUND To understand better the mechanism of left ventricular (LV) remodeling related to hypertension, it is important to evaluate LV function in relation to the changes in loading conditions. The aim of this study was to investigate changes in conventional ventricular-arterial coupling indexes, LV strain, and a new index reflecting regional myocardial work assessed noninvasively at rest and during isometric exercise in a random sample including participants with normal blood pressure and those with hypertension. METHODS A total of 148 participants (53.4% women; mean age, 52.0 years; 39.2% with hypertension) underwent simultaneous echocardiographic and arterial data acquisition at rest and during increased afterload (handgrip exercise). End-systolic pressure was determined from the carotid pulse wave. Arterial elastance (Ea) and LV elastance (Ees) were calculated as end-systolic pressure/stroke volume and end-systolic pressure/end-systolic volume. Doppler tissue imaging and two-dimensional speckle tracking were used to derive LV longitudinal strain. Regional myocardial work (ejection work density [EWD]) was the area of the pressure-strain loop during ejection. RESULTS At rest, with adjustments applied, Ees (3.06 vs 3.71 mm Hg/mL, P = .0003), Ea/Ees (0.54 vs 0.47, P = .002) and EWD (670 vs 802 Pa/m(2), P = .0001) differed significantly between participants with normal blood pressure and those with hypertension. During handgrip exercise, Ea and Ea/Ees significantly increased (P < .0001) in both groups. Doppler tissue imaging and two-dimensional LV strain decreased in participants with hypertension (P ≤ .008). Only in subjects with normal blood pressure EWD significantly increased (+14.7%, P = .0009). CONCLUSIONS Although patients with hypertension compared with those with normal blood pressure have increased LV systolic stiffness and regional myocardial work to match arterial load at rest, they might have diminished cardiac reserve to increase myocardial performance, as estimated by EWD during isometric exercise.
Collapse
Affiliation(s)
- Tatiana Kuznetsova
- The Studies Coordinating Centre, Division of Hypertension and Cardiovascular Rehabilitation, University of Leuven, Leuven, Belgium.
| | | | | | | | | | | |
Collapse
|
7
|
Narayan J, Amatoury J, Cho JG, Verma M, Kairaitis K, Wheatley J, Amis T. Snoring effects on the baroreflex: an animal model. Respir Physiol Neurobiol 2012; 180:342-51. [PMID: 22244879 DOI: 10.1016/j.resp.2011.12.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 10/14/2022]
Abstract
Baroreflex sensitivity (BRS) is reduced in humans during snoring, however the mechanisms are unknown. We used an anaesthetised rabbit induced snoring (IS) model, to test: (1) whether IS was associated with reduced BRS; and (2) if snoring related vibration transmission to peri-carotid tissues influenced BRS levels. BRS was quantified using the spontaneous sequence technique. During IS, BRS fell by 40%, without any associated change in blood pressure (BP) but accompanied by an increase in heart rate (HR). Direct application of a snore frequency and intensity matched vibratory stimulus to the peri-carotid tissues of non-snoring tracheostomised rabbits had no effect on BRS, HR or BP. In conclusion, IS induced depression of BRS is likely mediated via a HR driven change in BRS operating point that is unrelated to snoring-related vibration transmission to carotid baroreceptors. The anaesthetised IS rabbit provides a model in which mechanistic interactions between snoring and BRS can be further explored.
Collapse
Affiliation(s)
- Jyotishna Narayan
- Ludwig Engel Centre for Respiratory Research, Sydney, NSW, Australia.
| | | | | | | | | | | | | |
Collapse
|
8
|
Nalivaiko E, Antunes VR, Paton JFR. Control of cardiac contractility in the rat working heart-brainstem preparation. Exp Physiol 2010; 95:107-19. [PMID: 19717490 DOI: 10.1113/expphysiol.2009.048710] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A great deal of knowledge exists regarding neural control of myocardial function in the rat. Most of the studies addressing this issue were conducted either under general anaesthesia or in isolated hearts in vitro. Our principal aim was to provide a detailed quantitative description of mechanisms controlling cardiac contractility in the rat, in an anaesthetic-free preparation with a preserved functional brainstem. Furthermore, while vagally mediated negative inotropy is a well-known phenomenon, at present there is no direct evidence for its presence in the rat; we searched for such evidence. To this end, in the arterially perfused working heart-brainstem preparation of the rat, we measured left ventricular pressure (LVP) and computed its first derivative (LVdP/dt). We made the following new observations. (i) Zatebradine (cardiac sodium pacemaker current blocker) caused a bradycardia associated with increases in LVP and LVdP/dt; the latter effect was via a frequency-dependent mechanism. (ii) We confirmed that in the rat, the force-frequency relationship (dependence of contractility on heart rate) is positive over a low range of heart rates, and negative and linear at physiological levels of heart rate, and provided its quantitative description. (iii) The increase in systemic pressure caused a rise in contractility, and vagal blockade or destruction of the central nervous system did not alter this inotropic effect, suggesting that it was mediated by intrinsic cardiac mechanisms. (iv) Vagal stimulation caused complex polyphasic changes in LVdP/dt and LVP in unpaced preparations; during pacing, it caused slowly developing falls in LVdP/dt that could be prevented by atropine. We conclude that control of ventricular contractility in the rat heart differs from that in other mammals not only by its negative frequency dependence, but also in the potent influence of aortic pressure on LVdP/dt. At the level of autonomic neural control, our newly found, vagally mediated negative inotropic effect adds to the accumulating body of data regarding both the presence and the functional importance of parasympathetic innervation of the ventricular myocardium.
Collapse
Affiliation(s)
- Eugene Nalivaiko
- School of Biomedical Sciences, University of Newcastle, Newcastle, NSW 2308, Australia.
| | | | | |
Collapse
|
9
|
Karlocai K, Jokkel G, Kollai M. Changes in left ventricular contractility with the phase of respiration. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1998; 73:86-92. [PMID: 9862382 DOI: 10.1016/s0165-1838(98)00116-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The end-systolic wall stress (sigma(es))-velocity of circumferential fiber shortening (V(cfsc)) relation was defined during the respiratory cycle, in order to obtain a totally noninvasive measure of left ventricular contractility. Eight young, healthy subjects were studied with echocardiography and calibrated carotid pulse tracings, while performing slow paced breathing. Left ventricular sigma(es) vs. V(efsc) relation was determined by fitting linear regression line to data points obtained at different times during the respiratory cycle. Data are given as mean+/-1SD. Left ventricular sigma(es) and V(efsc) exhibited small but significant changes during the respiratory cycle: sigma(es) was highest in late inspiration (56.9+/-4.8 g/cm2) and lowest in late expiration (49.2+/-3.7 g/cm2); inversely, V(cfsc) was lowest during late inspiration (1.18+/-0.17 circ/s) and highest during late expiration (1.34+/-0.20 circ/s). The relation was significant in each subject (r = -0.64+/-0.13) and remained inverse and significant, when it was determined separately for inspiration and expiration (r = -0.61+/-0.17 and -0.68+/-0.12, respectively). At identical end-systolic wall stress, the velocity of shortening was greater during inspiration then expiration, suggesting that contractility was reduced during the expiratory phase. The reduced expiratory contractility might reflect increased vagal influence on the ventricular myocardium.
Collapse
Affiliation(s)
- K Karlocai
- Department of Cardiology, National Koranyi Institute, Semmelweis Medical University, Budapest, Hungary
| | | | | |
Collapse
|
10
|
Drolet G, Chalmers J, Blessing W. Vasodepressor neurons in medulla alter cardiac contractility and cardiac output. Hypertension 1993; 21:210-5. [PMID: 8094070 DOI: 10.1161/01.hyp.21.2.210] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We injected neuroexcitatory and neuroinhibitory agents into the depressor region of the caudal ventrolateral medulla of anesthetized rabbits and determined the effect on arterial pressure, myocardial contractility, cardiac output, and plasma catecholamines and neuropeptide Y. Brief excitation of the sympathoinhibitory neurons with medullary injection of L-glutamate reduced arterial pressure, peripheral vascular resistance, and myocardial contractility. Cardiac output was unaffected. Prolonged inhibition of the sympathoinhibitory neurons with medullary injection of muscimol increased arterial pressure, peripheral vascular resistance, and myocardial contractility. There was a progressive fall in cardiac output. These changes were accompanied by an increase in plasma neuropeptide Y and plasma norepinephrine, but no change in plasma epinephrine. Our findings indicate that the sympathoinhibitory vasomotor neurons in the caudal ventrolateral medulla tonically suppress the activity of sympathetic preganglionic neurons controlling myocardial contractility as well as peripheral vasomotor tone. Dysfunction of these medullary neurons could underly some forms of experimental hypertension.
Collapse
Affiliation(s)
- G Drolet
- Department of Medicine, Flinders University of South Australia, Bedford Park
| | | | | |
Collapse
|
11
|
Du ZY, Dusting GJ, Woodman OL. Baroreceptor reflexes and vascular reactivity during inhibition of nitric oxide synthesis in conscious rabbits. Eur J Pharmacol 1992; 214:21-6. [PMID: 1374717 DOI: 10.1016/0014-2999(92)90090-q] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effect of the nitric oxide (NO) synthase inhibitor N-nitro-L-arginine (NOLA) on vascular reactivity and the baroreceptor heart rate reflex was examined in chronically instrumented conscious rabbits. NOLA (15 mg/kg i.v.) significantly increased mean arterial pressure and hindlimb vascular resistance and decreased heart rate. Increases and decreases in arterial pressure were produced by the intravenous injection of phenylephrine and sodium nitroprusside respectively and the values obtained relating mean arterial blood pressure to heart rate were fitted to a sigmoid curve. NOLA significantly reduced the lower plateau of the arterial pressure--heart rate curve but did not significantly affect baroreceptor sensitivity. Depressor and hindlimb vasodilator responses to acetylcholine were significantly impaired by NOLA whereas responses to sodium nitroprusside were significantly enhanced. The pressor and hindlimb vasoconstrictor responses to phenylephrine were significantly enhanced in the presence of NOLA. We conclude that the bradycardia produced by NOLA does not result from a change in baroreceptor sensitivity. The continuous generation of NO appears to be important in regulating basal vascular resistance and in modulating vascular reactivity to both vasodilator and vasoconstrictor agents.
Collapse
Affiliation(s)
- Z Y Du
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia
| | | | | |
Collapse
|
12
|
Casadei B, Meyer TE, Coats AJ, Conway J, Sleight P. Baroreflex control of stroke volume in man: an effect mediated by the vagus. J Physiol 1992; 448:539-50. [PMID: 1593476 PMCID: PMC1176214 DOI: 10.1113/jphysiol.1992.sp019056] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
1. Beat-by-beat changes in cardiac performance in response to arterial baroreceptor stimulation induced by phenylephrine were evaluated by pulsed-wave aortic Doppler ultrasound in eighteen subjects. Stroke distance was used as an index of stroke volume and minute distance as an index of cardiac output; peak velocity was also measured. 2. The sensitivity of the baroreceptor-cardiac reflex was assessed by calculating the slope of the regression lines relating the changes in heart period (R-R interval), peak velocity and stroke distance in response to the rise in systolic blood pressure (SBP) induced by phenylephrine. In ten subjects the experiment was repeated after vagal blockade by atropine. Since the tachycardia induced by vagal blockade could alter the sensitivity of the baroreflex, we compared the results obtained after atropine with those obtained during pacing at similar rates in six subjects with cardiac pacemakers. 3. As R-R interval lengthened in response to the rise in SBP, stroke distance and peak velocity fell sharply. The subjects with a highly sensitive baroreceptor-heart rate reflex showed the greatest fall in peak velocity and stroke distance. The slope of the relationship between R-R interval and SBP for each subject correlated closely with that of peak velocity/SBP (correlation coefficient, r = 0.88) and stroke distance/SBP (r = 0.93) relationships. 4. Atropine virtually abolished all the cardiac reflex changes, despite a considerable increase in SBP induced by phenylephrine. At comparable heart rates achieved by pacing the sensitivity of the baroreceptor-cardiac reflex (calculated from the slopes of the regression lines relating changes in stroke distance and in peak velocity to the rise in SBP) was maintained and was significantly greater when compared to that obtained after vagal blockade. 5. These results show that the stimulation of arterial baroreceptors is accompanied by a fall in the Doppler-derived indices of stroke volume and cardiac output. This response is neural and is abolished by atropine, which indicates that it is mediated through the efferent vagus.
Collapse
Affiliation(s)
- B Casadei
- Department of Cardiovascular Medicine, John Radcliffe Hospital, Oxford
| | | | | | | | | |
Collapse
|
13
|
Minson RB, McRitchie RJ, Chalmers JP. Effects of neuropeptide Y on baroreflex control of heart rate and myocardial contractility in conscious rabbits. Clin Exp Pharmacol Physiol 1990; 17:39-49. [PMID: 2350901 DOI: 10.1111/j.1440-1681.1990.tb01263.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1. The effects of intravenous (i.v.) neuropeptide Y (NPY, 10 micrograms/kg bolus) on the stimulus-response curves relating changes in heart period (HP) and in peak left ventricular (LV) dP/dt to acute changes in mean arterial pressure (MAP) were determined in conscious, normotensive rabbits. 2. The relationship between increases and decreases in MAP and the subsequent changes in HP were represented by a sigmoid-shaped curve described by a logistic function. Following NPY administration there was a baroreflex-dependent increase in the maximum slope (sensitivity) at the midpoint of this MAP-HP curve from 7.0 +/- 0.5 to 10.6 +/- 1.3 ms/mmHg (P less than 0.05). NPY caused an upward shift in the whole curve which reflected the NPY-induced bradycardia and was independent of baroreflexes. 3. The relationship between increases in MAP and decreases in peak LV dP/dt was determined during fixed-rate atrial pacing to prevent the effects of the accompanying bradycardia. Increases in MAP and the corresponding reductions in peak LV dP/dt were represented by an exponential function. The slope of the curve, measured at its origin 5-15 min after NPY administration, was reduced from -0.9 +/- 0.2 to -0.4 +/- 0.1 units (P less than 0.05). 4. The effects of NPY are consistent with an action on efferent connections of the arterial baroreceptor reflex, mediated through a reduction in cardiac beta-adrenergic tone. They would also be explained through actions on the afferent or central neural connections of the baroreflex.
Collapse
Affiliation(s)
- R B Minson
- Department of Medicine, Flinders Medical Centre, Bedford Park, South Australia
| | | | | |
Collapse
|
14
|
Minson RB, McRitchie RJ, Morris MJ, Chalmers JP. Effects of neuropeptide Y on cardiac performance and renal blood flow in conscious normotensive and renal hypertensive rabbits. CLINICAL AND EXPERIMENTAL HYPERTENSION. PART A, THEORY AND PRACTICE 1990; 12:267-84. [PMID: 2347098 DOI: 10.3109/10641969009074733] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of neuropeptide Y (NPY, 10 micrograms/kg bolus iv) on cardiac output, renal blood flow and myocardial contractility were determined in intact renal hypertensive and normotensive rabbits instrumented with ultrasonic flow transducers or left ventricular catheters. The basal plasma concentration of NPY-like immunoreactivity in arterial blood was greater in the hypertensive rabbits (4.2 +/- 0.7 micrograms/l) than in normotensive animals (2.2 +/- 0.4 micrograms/l, p less than 0.05). There were similar moderate increases in arterial blood pressure and total peripheral resistance following NPY, but a small NPY-induced reduction in cardiac output in normotensive rabbits was not seen in hypertensive animals. Resting peak left ventricular dP/dt (an index of myocardial contractility) was higher in hypertensive rabbits (7397 +/- 619 vs 5551 +/- 342 mmHg/sec, p less than 0.05), but there was no significant difference between the maximum NPY-induced falls in peak dP/dt. NPY produced significant peak reductions in renal blood flow in both hypertensive (from 2.5 +/- 0.2 to 1.2 +/- 0.2 kHz, p less than 0.05) and in normotensive rabbit groups (from 2.2 +/- 0.1 to 0.3 +/- 0.1 kHz, p less than 0.05), but the fall in renal blood flow and the corresponding rise in renovascular resistance were smaller in the hypertensive animals (p less than 0.05). The cause of this apparent decrease in renovascular reactivity in the renal hypertensive model was not determined.
Collapse
Affiliation(s)
- R B Minson
- Department of Medicine, Flinders Medical Centre, Bedford Park, South Australia
| | | | | | | |
Collapse
|
15
|
Minson RB, McRitchie RJ, Chalmers JP. Effects of neuropeptide Y on left ventricular function in the conscious rabbit. Clin Exp Pharmacol Physiol 1987; 14:263-6. [PMID: 3665194 DOI: 10.1111/j.1440-1681.1987.tb00387.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1. Changes in arterial pressure, heart rate and left ventricular contractility induced by intravenous injections of neuropeptide Y (NPY; 1-30 micrograms/kg) were studied in the conscious rabbit. 2. NPY has a brief pressor effect associated with a bradycardia, an increase in left ventricular end diastolic pressure, and a prolonged fall in peak left ventricular dP/dt (LVdP/dt). 3. The haemodynamic changes increase substantially with increasing doses up to 10 micrograms/kg. Beyond 10 micrograms/kg there are only slight effects on heart rate or peak LV dP/dt.
Collapse
Affiliation(s)
- R B Minson
- Department of Medicine, Flinders Medical Centre, South Australia
| | | | | |
Collapse
|
16
|
Kamitani T, Little MH, Ellis EF. Effect of leukotrienes, 12-HETE, histamine, bradykinin, and 5-hydroxytryptamine on in vivo rabbit cerebral arteriolar diameter. J Cereb Blood Flow Metab 1985; 5:554-9. [PMID: 4055926 DOI: 10.1038/jcbfm.1985.83] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
To determine the possible role that leukotrienes (LTs) may play in the regulation of cerebral blood flow, the responses of cerebral arterioles to LTs and 12-hydroxyeicosatetraenoic acid (12-HETE) were studied in vivo in rabbits equipped with a cranial window for direct observation of the microcirculation. Topical application of LTC4, LTD4, or 12-HETE (1.6 X 10(-9)-3.1 X 10(-6) M) neither constricted nor dilated the pial arteries. LTB4 produced only a 5% vasoconstriction at 3.0 X 10(-6) M. However, bradykinin induced dose-dependent arteriolar vasodilation and histamine and 5-hydroxytryptamine induced dose-dependent arteriolar vasoconstriction. Although some LTs have potent vasoconstrictor activity in peripheral tissues and 5-lipoxygenase products have been hypothesized to be mediators of vasospasm after subarachnoid hemorrhage, LTB4, LTC4, LTD4, and 12-HETE apparently are unable to induce significant constriction of the cerebral arterioles in the anesthetized rabbit.
Collapse
|
17
|
Kamitani T, Little MH, Ellis EF. Evidence for a possible role of the brain kallikrein-kinin system in the modulation of the cerebral circulation. Circ Res 1985; 57:545-52. [PMID: 2412721 DOI: 10.1161/01.res.57.4.545] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Experiments by others have shown that exogenous bradykinin dilates cerebral arterioles and that the brain contains kininogen and kallikrein, the latter being the enzyme which converts kininogen to bradykinin. The objective of these experiments was to determine if bradykinin produced from endogenous brain kininogen can affect the cerebral microcirculation. Rabbit pial arteriolar diameter was measured with a microscope using the closed cranial window technique. Topical application of bradykinin (10(-8)-10(-5) M) induced a dose-dependent vasodilation (8-46%) which was completely inhibited by the cyclooxygenase enzyme inhibitors indomethacin and meclofenamic acid. Topical application of 1 U of tissue kallikrein per milliliter of artificial cerebrospinal fluid induced 43% dilation, which could be prevented by local treatment with indomethacin or the proteinase inhibitor aprotinin. The action of aprotinin and indomethacin was specific, since aprotinin did not affect the dilation produced by bradykinin, and indomethacin did not affect dilation produced by adenosine. A second application of kallikrein had no effect on cerebral diameter, yet the arterioles still responded normally to exogenous bradykinin, indicating that the first application of kallikrein depleted brain kininogen. We suggest that activation of brain kallikrein and subsequent formation of kinin from brain kininogen may be important in modulation of cerebral blood flow or generation of cerebral edema.
Collapse
|
18
|
Yamamoto J, Tsuchiya M, Saito M, Ikeda M. Cardiac contractile and coronary flow reserves in deoxycorticosterone acetate-salt hypertensive rats. Hypertension 1985; 7:569-77. [PMID: 3159665 DOI: 10.1161/01.hyp.7.4.569] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cardiac contractility and coronary flow were compared in conscious rats with established deoxycorticosterone acetate-salt hypertension and in those with sham treatment. The hypertensive rats showed a 32% increase in left ventricular/body weight ratio at 9 weeks of treatment and 42% at 18 weeks of treatment. Resting peak rate of change of pressure (dp/dt) was unchanged at 9 weeks and increased at 18 weeks in hypertensive rats, while isoproterenol-stimulated maximal, propranolol-induced minimal, and Ca2+-stimulated maximal peak dp/dt were greater at 18 weeks. These data indicate the preservation of contractile function. At 18 weeks, the beta-adrenergic receptor-mediated contractile reserve, estimated from isoproterenol-stimulated maximal and resting peak dp/dt, was reduced but the propranolol-induced decrease in peak dp/dt was increased in hypertensive rats compared with sham-treated rats. Thus, at this stage, a greater portion of the total contractile capacity appeared to be mobilized with prolongation of hypertension and progression of left ventricular hypertrophy. No differences were observed in left ventricular and right ventricular coronary flow (microspheres) and left ventricular inner/outer flow ratio at rest and with dipyridamole-induced maximal coronary dilatation, at 9 and 18 weeks. There were no alterations in left or right ventricular coronary flow reserves, as estimated from resting and dipyridamole-induced values. The minimal coronary vascular resistance (normalized for gram of tissue) of both the left and right ventricles was increased at either stage, which suggests the occurrence of structural coronary vascular changes. Thus, basal coronary flow and a coronary flow reserve were uncompromised despite evidence of structural coronary vascular alterations in these hypertensive rats.
Collapse
|
19
|
Aylward PE, McRitchie RJ, West MJ, Chalmers JP. Relative roles of vagal and sympathetic effector mechanisms in the baroreflex control of myocardial contractility in conscious rabbits. Pflugers Arch 1985; 403:21-7. [PMID: 3982955 DOI: 10.1007/bf00583276] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The relative roles of vagal and sympathetic effector mechanisms in the baroreflex control of myocardial contractility have been assessed in the conscious normotensive and hypertensive rabbit. Graded increases in mean arterial pressure (MAP) were produced by inflation of a balloon occluder around the abdominal aorta. Stimulus response curves relating the change in MAP to the induced change in peak rate of change of left ventricular pressure (peak LV dP/dt) were produced when heart rate was allowed to change and when it was held constant by atrial pacing. These curves were repeated after sympathetic blockade with propranolol, vagal blockade with methylscopolamine and combined blockade with the two drugs together. Increase in MAP produced a reflex fall in peak LV dP/dt which was due to two components. There was a reflex negative inotropic effect which was independent of heart rate, occurring in animals in whom heart rate was held constant by atrial pacing, and there was also a reduction in peak LV dP/dt which was caused by the reflex bradycardia when the heart rate was allowed to change. Both sympathetic and vagal efferents contributed to the reflex fall in peak LV dP/dt seen after elevation of MAP, the sympathetic being primarily responsible for the direct negative inotropic effect and the vagus for the bradycardia and hence the secondary effects on peak LV dP/dt. The slope of the stimulus response curves relating the fall in peak LV dP/dt to the increase in MAP was similar in intact normotensive and hypertensive rabbits, both with and without atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
20
|
Blaustein MP, Hamlyn JM. Sodium transport inhibition, cell calcium, and hypertension. The natriuretic hormone/Na+-Ca2+ exchange/hypertension hypothesis. Am J Med 1984; 77:45-59. [PMID: 6091450 DOI: 10.1016/s0002-9343(84)80037-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Sodium plays a critical role in the etiology of essential hypertension, but the mechanism by which excess dietary sodium actually leads to the elevation of blood pressure is not understood. The hypothesis described shows how an excessive sodium load can lead to the development of hypertension. The underlying factor must be a genetic or acquired deficiency or limitation in renal sodium excretion that may be undetectable by standard renal function tests. The resultant tendency towards sodium, water, and extracellular fluid volume expansion is compensated by the secretion of a natriuretic hormone that promotes sodium excretion by inhibiting sodium pumps in the kidney tubule cells. The hormone also inhibits sodium pumps in other cells, including vascular smooth muscle cells, causing intracellular sodium to increase. Then, because the vascular smooth muscle cells contain a Na+-Ca2+ exchange transport system in their plasma membranes, more calcium than normal is delivered to these cells. This causes the increased contractility and reactivity that underlies the increased vascular tone and peripheral vascular resistance that elevates the blood pressure.
Collapse
|