Weibull distribution function for cardiac contraction: integrative analysis

• Published in: American journal of physiology. Heart and circulatory physiology 1999-11, Vol.277 (5), p.H1940-H1945
• Main Authors: Araki, Junichi, Matsubara, Hiromi, Shimizu, Juichiro, Mikane, Takeshi, Mohri, Satoshi, Mizuno, Ju, Takaki, Miyako, Ohe, Tohru, Hirakawa, Masahisa, Suga, Hiroyuki
• Format: Article
• Language: English
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.1999.277.5.h1940

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