Document Detail

Spatio-temporal attributes of left ventricular pressure decay rate during isovolumic relaxation.
MedLine Citation:
PMID:  22210748     Owner:  NLM     Status:  MEDLINE    
Global left ventricular (LV) isovolumic relaxation rate has been characterized: 1) via the time constant of isovolumic relaxation τ or 2) via the logistic time constant τ(L). An alternate kinematic method, characterizes isovolumic relaxation (IVR) in accordance with Newton's Second Law. The model's parameters, stiffness E(k), and damping/relaxation μ result from best fit of model-predicted pressure to in vivo data. All three models (exponential, logistic, and kinematic) characterize global relaxation in terms of pressure decay rates. However, IVR is inhomogeneous and anisotropic. Apical and basal LV wall segments untwist at different times and rates, and transmural strain and strain rates differ due to the helically variable pitch of myocytes and sheets. Accordingly, we hypothesized that the exponential model (τ) or kinematic model (μ and E(k)) parameters will elucidate the spatiotemporal variation of IVR rate. Left ventricular pressures in 20 subjects were recorded using a high-fidelity, multipressure transducer (3 cm apart) catheter. Simultaneous, dual-channel pressure data was plotted in the pressure phase-plane (dP/dt vs. P) and τ, μ, and E(k) were computed in 1631 beats (average: 82 beats per subject). Tau differed significantly between the two channels (P < 0.05) in 16 of 20 subjects, whereas μ and E(k) differed significantly (P < 0.05) in all 20 subjects. These results show that quantifying the relaxation rate from data recorded at a single location has limitations. Moreover, kinematic model based analysis allows characterization of restoring (recoil) forces and resistive (crossbridge uncoupling) forces during IVR and their spatio-temporal dependence, thereby elucidating the relative roles of stiffness vs. relaxation as IVR rate determinants.
Erina Ghosh; Sándor J Kovács
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-12-30
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  302     ISSN:  1522-1539     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-02-24     Completed Date:  2012-04-19     Revised Date:  2012-05-23    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H1094-101     Citation Subset:  IM    
Cardiovascular Biophysics Laboratory, Washington Univ. Medical Center, 660 South Euclid Ave Box 8086, St. Louis, MO. 63110, USA.
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MeSH Terms
Heart Rate / physiology
Middle Aged
Models, Cardiovascular
Myocardial Contraction / physiology
Stroke Volume / physiology
Ventricular Function, Left / physiology*
Ventricular Pressure / physiology*

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