Vol. 277, Issue 5, H1940-H1945, November 1999
Weibull distribution function for cardiac contraction:
integrative analysis
Junichi
Araki1,
Hiromi
Matsubara1,2,
Juichiro
Shimizu1,
Takeshi
Mikane1,3,
Satoshi
Mohri1,2,
Ju
Mizuno1,3,
Miyako
Takaki4,
Tohru
Ohe2,
Masahisa
Hirakawa3, and
Hiroyuki
Suga1
Departments of 1 Physiology II,
2 Cardiovascular Medicine, and
3 Anesthesiology and
Resuscitology, Okayama University Medical School, Okayama 700-8558; and
4 Department of Physiology II,
Nara University Medical School, Kashihara, Nara 634-8521, Japan
The Weibull
distribution is widely used to analyze the cumulative loss of
performance, i.e., breakdown, of a complex system in systems
engineering. We found for the first time that the difference curve of
two Weibull distribution functions almost identically fitted the
isovolumically contracting left ventricular (LV) pressure-time curve
[P(t)] in all 345 beats
(3 beats at each of 5 volumes in 23 canine hearts;
r = 0.999953 ± 0.000027; mean ± SD). The first derivative of the difference curve also closely
fitted the first derivative of the
P(t) curve. These results suggest
the possibility that the LV isovolumic
P(t) curve may be characterized by
two counteracting cumulative breakdown systems. Of these, the first breakdown system causes a gradual pressure rise and the second breakdown system causes a gradual pressure fall. This Weibull-function model of the heart seems to give a new systems engineering or integrative physiological view of the logic underlying LV isovolumic pressure generation.
systems engineering; weakest-link principle; ventricular pressure; curve fitting; integrative physiology
