Document Detail

Logistic time constant of isovolumic relaxation pressure-time curve in the canine left ventricle. Better alternative to exponential time constant.
MedLine Citation:
PMID:  7554217     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The time constant of left ventricular (LV) relaxation derived from a monoexponential model has been widely used as an index of LV relaxation rate or lusitropism, although this model has several well-recognized problems. In the present study, we proposed a logistic model and derived a "logistic" time constant (TL) as a better alternative to the conventional "exponential" time constant (TE). METHODS AND RESULTS: A total of 189 beats (147 isovolumic and 42 ejecting beats) were investigated in seven canine excised cross-circulated heart preparations. We found that the logistic model fitted much more precisely all the observed LV isovolumic relaxation pressure-time [P(t)] curves than the monoexponential model (P < .05). The logistic model also fitted well both the time curve of the first derivative of the observed P(t) (dP/dt) and the dP/dt-P(t) phase-plane curve. Like TE, TL indicated that volume loading depressed LV lusitropism and that increasing heart rate and ejection fraction augmented it. TL was independent of the choice of cutoff point defining the end of isovolumic relaxation; TE was dependent on that choice. CONCLUSIONS: We conclude that the logistic model better fits LV isovolumic relaxation P(t) than the monoexponential model in the present heart preparation. We therefore propose TL as a better alternative to TE for evaluating LV lusitropism.
H Matsubara; M Takaki; S Yasuhara; J Araki; H Suga
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Circulation     Volume:  92     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1995 Oct 
Date Detail:
Created Date:  1995-11-14     Completed Date:  1995-11-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2318-26     Citation Subset:  AIM; IM    
Department of Physiology II, Okayama University Medical School, Japan.
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MeSH Terms
Diastole / physiology*
Logistic Models
Models, Cardiovascular*
Time Factors
Ventricular Function, Left / physiology*
Ventricular Pressure / physiology

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