scholarly journals Dynamic control of maximal ventricular elastance via the baroreflex and force-frequency relation in awake dogs before and after pacing-induced heart failure

2010 ◽  
Vol 299 (1) ◽  
pp. H62-H69 ◽  
Author(s):  
Xiaoxiao Chen ◽  
Javier A. Sala-Mercado ◽  
Robert L. Hammond ◽  
Masashi Ichinose ◽  
Soroor Soltani ◽  
...  
Keyword(s):  
Heart Failure ◽  
Transfer Function ◽  
Transfer Functions ◽  
Dynamic Properties ◽  
System Response ◽  
Force Frequency ◽  
Arterial Baroreflex ◽  
Ventricular Elastance ◽  
Arterial Blood ◽  
Frequency Relation

We investigated to what extent maximal ventricular elastance ( Emax) is dynamically controlled by the arterial baroreflex and force-frequency relation in conscious dogs and to what extent these mechanisms are attenuated after the induction of heart failure (HF). We mathematically analyzed spontaneous beat-to-beat hemodynamic variability. First, we estimated Emax for each beat during a baseline period using the ventricular unstressed volume determined with the traditional multiple beat method during vena cava occlusion. We then jointly identified the transfer functions (system gain value and time delay per frequency) relating beat-to-beat fluctuations in arterial blood pressure (ABP) to Emax (ABP→ Emax) and beat-to-beat fluctuations in heart rate (HR) to Emax (HR→ Emax) to characterize the dynamic properties of the arterial baroreflex and force-frequency relation, respectively. During the control condition, the ABP→ Emax transfer function revealed that ABP perturbations caused opposite direction Emax changes with a gain value of −0.023 ± 0.012 ml−1, whereas the HR→ Emax transfer function indicated that HR alterations caused same direction Emax changes with a gain value of 0.013 ± 0.005 mmHg·ml−1·(beats/min)−1. Both transfer functions behaved as low-pass filters. However, the ABP→ Emax transfer function was more sluggish than the HR→ Emax transfer function with overall time constants (indicator of full system response time to a sudden input change) of 11.2 ± 2.8 and 1.7 ± 0.5 s ( P < 0.05), respectively. During the HF condition, the ABP→ Emax and HR→ Emax transfer functions were markedly depressed with gain values reduced to −0.0002 ± 0.007 ml−1 and −0.001 ± 0.004 mmHg·ml−1·(beats/min)−1 ( P < 0.1). Emax is rapidly and significantly controlled at rest, but this modulation is virtually abolished in HF.

scholarly journals Force-frequency relation in human heart failure.

Circulation ◽  
1992 ◽  
Vol 86 (6) ◽  
pp. 2017-2018 ◽  
Author(s):  
R H Schwinger ◽  
M Böhm ◽  
A Koch ◽  
E Erdmann
Keyword(s):  
Heart Failure ◽  
Human Heart ◽  
Force Frequency ◽  
Human Heart Failure ◽  
Frequency Relation

Transfer Function Modeling of Distributed Piezoelectric Vibration Energy Harvesters

2009 ◽  
Author(s):  
Chin An Tan ◽  
Heather L. Lai
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Vibration Energy ◽  
System Response ◽  
Distributed Parameter ◽  
Domain Modeling ◽  
Vibration Energy Harvesting ◽  
Energy Harvesters ◽  
Adjoint Systems ◽  
The Stability

Extensive research has been conducted on vibration energy harvesting utilizing a distributed piezoelectric beam structure. A fundamental issue in the design of these harvesters is the understanding of the response of the beam to arbitrary external excitations (boundary excitations in most models). The modal analysis method has been the primary tool for evaluating the system response. However, a change in the model boundary conditions requires a reevaluation of the eigenfunctions in the series and information of higher-order dynamics may be lost in the truncation. In this paper, a frequency domain modeling approach based in the system transfer functions is proposed. The transfer function of a distributed parameter system contains all of the information required to predict the system spectrum, the system response under any initial and external disturbances, and the stability of the system response. The methodology proposed in this paper is valid for both self-adjoint and non-self-adjoint systems, and is useful for numerical computer coding and energy harvester design investigations. Examples will be discussed to demonstrate the effectiveness of this approach for designs of vibration energy harvesters.

Attenuated arterial baroreflex buffering of muscle metaboreflex in heart failure

2005 ◽  
Vol 289 (6) ◽  
pp. H2416-H2423 ◽  
Author(s):  
Jong-Kyung Kim ◽  
Javier A. Sala-Mercado ◽  
Robert L. Hammond ◽  
Jaime Rodriguez ◽  
Tadeusz J. Scislo ◽  
...  
Keyword(s):  
Heart Failure ◽  
Pressor Response ◽  
Dynamic Exercise ◽  
Arterial Baroreflex ◽  
Muscle Metaboreflex ◽  
Peripheral Vasoconstriction ◽  
Arterial Blood ◽  
Pressor Responses ◽  
Before And After ◽  
Chronically Instrumented Dogs

Previous studies have shown that heart failure (HF) or sinoaortic denervation (SAD) alters the strength and mechanisms of the muscle metaboreflex during dynamic exercise. However, it is still unknown to what extent SAD may modify the muscle metaboreflex in HF. Therefore, we quantified the contribution of cardiac output (CO) and peripheral vasoconstriction to metaboreflex-mediated increases in mean arterial blood pressure (MAP) in conscious, chronically instrumented dogs before and after induction of HF in both barointact and SAD conditions during mild and moderate exercise. The muscle metaboreflex was activated via partial reductions in hindlimb blood flow. After SAD, the metaboreflex pressor responses were significantly higher with respect to the barointact condition despite lower CO responses. The pressor response was significantly lower in HF after SAD but still higher than that of HF in the barointact condition. During control experiments in the barointact condition, total vascular conductance summed from all beds except the hindlimbs did not change with muscle metaboreflex activation, whereas in the SAD condition both before and after induction of HF significant vasoconstriction occurred. We conclude that SAD substantially increased the contribution of peripheral vasoconstriction to metaboreflex-induced increases in MAP, whereas in HF SAD did not markedly alter the patterns of the reflex responses, likely reflecting that in HF the ability of the arterial baroreflex to buffer metaboreflex responses is impaired.

A Transfer-Function Formulation For Nonuniformly Distributed Parameter Systems

1994 ◽  
Vol 116 (4) ◽  
pp. 426-432 ◽  
Author(s):  
B. Yang ◽  
H. Fang
Keyword(s):  
Transfer Function ◽  
State Space ◽  
Fundamental Matrix ◽  
Transfer Functions ◽  
Function Analysis ◽  
System Response ◽  
Approximate Methods ◽  
Arbitrary Boundary ◽  
Transfer Function Analysis ◽  
Function Formulation

This paper studies a transfer-function formulation for general one-dimensional, nonuniformly distributed systems, subject to arbitrary boundary conditions and external disturbances. In the development, the governing equations of the nonuniform system are cast into a state-space form in the Laplace transform domain. The system response and distributed transfer functions are derived in term of the fundamental matrix of the state-space equation. Two approximate methods, the step-function approximation and truncated Taylor series, are proposed to evaluate the fundamental matrix. With the transfer-function formulation, various dynamics and control problems for the nonuniformly distributed system can be conveniently addressed. The transfer-function analysis also is applied to constrained/combined nonuniformly distibuted systems. The method developed is illustrated on two nonuniform beams.

Transfer Functions of One-Dimensional Distributed Parameter Systems

1992 ◽  
Vol 59 (4) ◽  
pp. 1009-1014 ◽  
Author(s):  
B. Yang ◽  
C. A. Tan
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Distributed Parameter Systems ◽  
Axially Moving Beam ◽  
System Response ◽  
Distributed Parameter ◽  
One Dimensional ◽  
Adjoint Systems ◽  
The Laplace Transform ◽  
Axially Moving

Distributed parameter systems describe many important physical processes. The transfer function of a distributed parameter system contains all information required to predict the system spectrum, the system response under any initial and external disturbances, and the stability of the system response. This paper presents a new method for evaluating transfer functions for a class of one-dimensional distributed parameter systems. The system equations are cast into a matrix form in the Laplace transform domain. Through determination of a fundamental matrix, the system transfer function is precisely evaluated in closed form. The method proposed is valid for both self-adjoint and non-self-adjoint systems, and is extremely convenient in computer coding. The method is applied to a damped, axially moving beam with different boundary conditions.

Dynamic arterial baroreflex in rabbits with heart failure induced by rapid pacing

1994 ◽  
Vol 267 (1) ◽  
pp. H92-H99 ◽  
Author(s):  
H. Masaki ◽  
T. Imaizumi ◽  
Y. Harasawa ◽  
A. Takeshita
Keyword(s):  
Heart Failure ◽  
Transfer Function ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Aortic Pressure ◽  
Arterial Baroreflex ◽  
Nerve Activity ◽  
Renal Nerve ◽  
Renal Nerve Activity ◽  
Rapid Pacing

Excessive sympathetic nerve activity in heart failure could be attributable to impaired arterial baroreflex function. Employing transfer function analysis, we evaluated the arterial baroreflex in control rabbits (n = 8) and in rabbits with rapid pacing-induced heart failure (n = 10) in a dynamic manner. Rabbits in the heart-failure group showed elevated filling pressures, depressed first derivative of left ventricular pressure, pulmonary congestion, and an increased level of plasma norepinephrine. Varying aortic pressure pseudorandomly and recording responses in renal nerve activity, we calculated the transfer function from aortic pressure to renal nerve activity. The gain of the transfer function was similar between control and heart-failure rabbits over 0.04–0.4 Hz as well as the phase and the coherence, indicating that the dynamic arterial baroreflex was preserved in our rabbit heart-failure model. Vagotomy increased the gain of the arterial baroreflex over 0.04–0.4 Hz in control (P < 0.05) but not in heart-failure rabbits, indicating that vagal afferents, which normally inhibit the dynamic arterial baroreflex, no more did so in heart failure. We conclude that excessive sympathetic nerve activity in heart failure may not be due to impaired dynamic arterial baroreflex, but that this apparently preserved arterial baroreflex in heart failure may be due to impaired cardiopulmonary baroreflex.

scholarly journals Selective quantification of the cardiac sympathetic and parasympathetic nervous systems by multisignal analysis of cardiorespiratory variability

2008 ◽  
Vol 294 (1) ◽  
pp. H362-H371 ◽  
Author(s):  
Xiaoxiao Chen ◽  
Ramakrishna Mukkamala
Keyword(s):  
Nervous System ◽  
Transfer Function ◽  
Parasympathetic Nervous System ◽  
Transfer Functions ◽  
Low Frequency ◽  
Sympathetic Blockade ◽  
Nervous Systems ◽  
Autonomic Nervous ◽  
Arterial Blood ◽  
The Time Domain

Heart rate (HR) power spectral indexes are limited as measures of the cardiac autonomic nervous systems (CANS) in that they neither offer an effective marker of the β-sympathetic nervous system (SNS) due to its overlap with the parasympathetic nervous system (PNS) in the low-frequency (LF) band nor afford specific measures of the CANS due to input contributions to HR [e.g., arterial blood pressure (ABP) and instantaneous lung volume (ILV)]. We derived new PNS and SNS indexes by multisignal analysis of cardiorespiratory variability. The basic idea was to identify the autonomically mediated transfer functions relating fluctuations in ILV to HR (ILV→HR) and fluctuations in ABP to HR (ABP→HR) so as to eliminate the input contributions to HR and then separate each estimated transfer function in the time domain into PNS and SNS indexes using physiological knowledge. We evaluated these indexes with respect to selective pharmacological autonomic nervous blockade in 14 humans. Our results showed that the PNS index derived from the ABP→HR transfer function was correctly decreased after vagal and double (vagal + β-sympathetic) blockade ( P < 0.01) and did not change after β-sympathetic blockade, whereas the SNS index derived from the same transfer function was correctly reduced after β-sympathetic blockade in the standing posture and double blockade ( P < 0.05) and remained the same after vagal blockade. However, this SNS index did not significantly decrease after β-sympathetic blockade in the supine posture. Overall, these predictions were better than those provided by the traditional high-frequency (HF) power, LF-to-HF ratio, and normalized LF power of HR variability.

scholarly journals Levosimendan restores the positive force-frequency relation in heart failure

2011 ◽  
Vol 301 (2) ◽  
pp. H488-H496 ◽  
Author(s):  
Satoshi Masutani ◽  
Heng-Jie Cheng ◽  
Hideo Tachibana ◽  
William C. Little ◽  
Che-Ping Cheng
Keyword(s):  
Heart Failure ◽  
Contractile Function ◽  
Mechanical Efficiency ◽  
Left Ventricular ◽  
Force Frequency ◽  
Stroke Work ◽  
Arterial Elastance ◽  
Major Mechanism ◽  
Frequency Relation ◽  
Positive Force

Frequency potentiation of contractile function is a major mechanism of the increase in myocardial performance during exercise. In heart failure (HF), this positive force-frequency relation is impaired, and the abnormal left ventricular (LV)-arterial coupling is exacerbated by tachycardia. A myofilament Ca2+ sensitizer, levosimendan, has been shown to improve exercise tolerance in HF. This may be due to its beneficial actions on the force-frequency relation and LV-arterial coupling (end-systolic elastance/arterial elastance, EES/ EA). We assessed the effects of therapeutic doses of levosimendan on the force-frequency relation and EES/ EA in nine conscious dogs after pacing-induced HF using pressure-volume analysis. Before HF, pacing tachycardia increased EES, shortened τ, and did not impair EES/ EA and mechanical efficiency (stroke work/pressure-volume area, SW/PVA). In contrast, after HF, pacing at 140, 160, 180, and 200 beat/min (bpm) produced smaller a increase of EES or less shortening of τ, whereas EES/ EA (from 0.56 at baseline to 0.42 at 200 bpm) and SW/PVA (from 0.52 at baseline to 0.43 at 200 bpm) progressively decreased. With levosimendan, basal EES increased 27% (6.2 mmHg/ml), τ decreased 11% (40.8 ms), EES/ EA increased 34% (0.75), and SW/PVA improved by 15% (0.60). During tachycardia, EES further increased by 23%, 37%, 68%, and 89%; τ decreased by 9%, 12%, 15%, and 17%; and EES/ EA was augmented by 11%, 16%, 31%, and 33%, incrementally, with pacing rate. SW/PVA was improved (0.61 to 0.64). In conclusion, in HF, treatment with levosimendan restores the normal positive LV systolic and diastolic force-frequency relation and prevents tachycardia-induced adverse effect on LV-arterial coupling and mechanical efficiency.

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