Assessment of the time constant of relaxation: insights from simulations and hemodynamic measurements.

@article{deMey2001AssessmentOT,
  title={Assessment of the time constant of relaxation: insights from simulations and hemodynamic measurements.},
  author={Stefaan de Mey and J. D. R. Thomas and N. L. Greenberg and Pieter M. Vandervoort and Pascal R. Verdonck},
  journal={American journal of physiology. Heart and circulatory physiology},
  year={2001},
  volume={280 6},
  pages={
          H2936-43
        }
}
The objective of this study was to use high-fidelity animal data and numerical simulations to gain more insight into the reliability of the estimated relaxation constant derived from left ventricular pressure decays, assuming a monoexponential model with either a fixed zero or free moving pressure asymptote. Comparison of the experimental data with the results of the simulations demonstrated a trade off between the fixed zero and the free moving asymptote approach. The latter method more… 
View on PubMed
ajpheart.physiology.org
16 Citations
Background Citations
1
Methods Citations
5

Figures and Tables from this paper

16 Citations

Citation Type

Citation Type

Noninvasive Estimation of the Rate of Relaxation by the Analysis of Intraventricular Pressure Gradients
TLDR
The Doppler-derived REIVPD provides a sensitive, reliable, reproducible, and relatively load-independent index of the rate of LV relaxation, and improves noninvasive assessment ofLV relaxation in the clinical setting.
Diastolic chamber properties of the left ventricle assessed by global fitting of pressure-volume data: improving the gold standard of diastolic function.
TLDR
In clinical and preclinical research, global optimization algorithms provide the most complete, accurate, and reproducible assessment of global left ventricular diastolic chamber properties from PV data.
Regional Differences in Relaxation Time (τ): Its Relationship to Intraventricular Pressure Gradients in a Canine and Hydraulic Model
TLDR
Assessment of IVPG, now available noninvasively, could provide useful clinical insight into cardiac ischemia and diastolic dysfunction and suggest that higher LV compliance is associated with increased IVPG.
Effects of mechanical limitation of apical rotation on left ventricular relaxation and end-diastolic pressure.
TLDR
Diastolic function was impaired with reduced apical rotation and UR(IVR) when the apex of the heart was immobilized using an apical suction device, and LV systolic pressure and stroke volume were not changed.
Pattern of right ventricular pressure fall and its modulation by afterload.
TLDR
In the RV, dP/dt(min), tau and the proportional contribution of accelerative and decelerative phases for ventricular pressure fall are afterload-dependent, Consequently, tau evaluates a relatively much shorter segment of RVP than LVP fall.
Lymphatic vessels transition to state of summation above a critical contraction frequency.
TLDR
It is hypothesized that lymphatic vessels transition to a state of summation when lymphatic vessel contraction frequency exceeds a critical value, and the convergence of beat-to-beat period and contraction cycle duration predicted a critical transition value, beyond which the vessel does not have time to fully relax.
Impact of acute moderate elevation in left ventricular afterload on diastolic transmitral flow efficiency: analysis by vortex formation time.
Possible Mechanisms Underlying Aging-Related Changes in Early Diastolic Filling and Long Axis Motion—Left Ventricular Length and Blood Pressure
TLDR
It is suggested that slowing of myocyte relaxation is unlikely to be the sole, and may not be the main, mechanism underlying age-related decreases in E and e` and shortening of LVEDL.
A critical contraction frequency in lymphatic vessels: transition to a state of partial summation
TLDR
A Critical Contraction Frequency in Lymphatic Vessels: Transition to a State of Partial Summation hypothesized that above a critical contraction frequency there is significant summation, evidenced by significantly increased diastolic active tension (i.e. basal tone).
Cardiac biomechanics and heart dysfunction
TLDR
This chapter discusses the many parameters used to quantify cardiac function, how the parameters are assessed, and how they change during cardiac ischemia and infarction.
...
1
2
...

References

SHOWING 1-10 OF 20 REFERENCES
Estimation of time constant of left ventricular relaxation.
TLDR
It is concluded that isovolumic pressure fall approximates closely to a monoexponential in a wide variety of circumstances, and it is legitimate, therefore, to describe the rate of relaxation by a time constant.
Time constant of isovolumic pressure fall: new numerical approaches and significance.
TLDR
It is found that the upward or downward translation of the LVP curve had an important effect on the value of TL calculated by the semilogarithmic method, and the values of TL and the -dP/dt values extrapolated to 15 mmHg from a model with PB, were much more sensitive to beta-agonist or antagonist drugs than to others whose action was through load alteration.
Variation in Tau, the time constant for isovolumic relaxation, along the left ventricular base-to-apex axis
TLDR
The purpose of this study was to determine if the method of τ calculation effects the results when left ventricular pressure (LVP) is measured at different positions along the base-to-apex axis and to conclude that the method used to calculate τ will effect the results and, thus, conclusions drawn from τ data.
Logistic time constant of isovolumic relaxation pressure-time curve in the canine left ventricle. Better alternative to exponential time constant.
TLDR
It is concluded that the logistic model better fits LV isovolumic relaxation P(t) than the monoexponential model in the present heart preparation and is proposed as a better alternative to TE for evaluating LV lusitropism.
Modeling the isovolumic relaxation period.
TLDR
It was found that the isovolumic relaxation period approximates an exponential, that the theoretic asymptote is variable, and that the Levenburg-Marquardt algorithm can be used efficiently to model this period.
Time constant of isovolumic pressure fall in the intact canine left ventricle.
TLDR
The two standard methods of computation of the time constant of the isovolumic single exponential decay of the left ventricular pressure were compared in anaesthetised, artificially ventilated, closed chest dogs and indicated the dependence of relaxation on afterload but the independence on preload or ejection timing.
A comparison of two exponential models of the time constant during left ventricular isovolumic pressure decay in coronary artery disease.
TLDR
The relaxation rate can be evaluated more reliably by Tc than by Tw, irrespective of associated pressure changes during ischemia in CADpts, and the changes in Tw may be due to an increase in LVPmin rather than to any direct effect of ischemIA on the relaxation rate.
Comparison of ventricular pressure relaxation assessments in human heart failure: quantitative influence on load and drug sensitivity analysis.
Effects of aging on left ventricular relaxation in humans. Analysis of left ventricular isovolumic pressure decay.
TLDR
In the absence of coronary artery disease, systemic hypertension, left ventricular systolic dysfunction,Left ventricular relaxation assessed by the time constant of isovolumic pressure decay remains essentially unchanged with normal adult aging, at least until the eighth decade.
Left ventricular relaxation in the filling and nonfilling intact canine heart.
TLDR
Left ventricular relaxation in the filling and transiently nonfilling working hearts of seven open-chest pentobarbital-anesthetized dogs is studied by totally occluding the mitral annulus during one systole to evaluate the validity of a monoexponential characterization of relaxation.
...
1
2
...