Article

Myocardial twitch duration and the dependence of oxygen consumption on pressure-volume area: experiments and modelling.

D. Loiselle: Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand. .
The Journal of Physiology (impact factor: 4.72). 05/2012; 590(Pt 18):4603-22. DOI:10.1113/jphysiol.2012.228965
Source: PubMed

ABSTRACT Key points  The energy expenditure of the heart is linearly related to its work performance, as measured by its development of pressure-volume area.  We have explored the basis of this phenomenon both experimentally (by measuring the heat production of isolated ventricular tissue undergoing cyclic contraction and relaxation) and theoretically (using mathematical modelling).  We provide the first evidence that the heat production of isolated trabeculae undergoing fixed-end contractions varies linearly with force-length area, and confirm that twitch duration increases progressively with muscle length.  Mathematical modelling reveals that length-dependent prolongation of the twitch reflects length- (or, equivalently, force-) dependent binding of Ca(2+) to troponin-C, together with Ca(2+)-dependent crossbridge cooperativity.  Mathematical modelling further reveals that the apparent linear dependence of heat production on force-length area is remarkably robust against departures from the linearity of length-dependent twitch duration.

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Keywords

apparent linear dependence
 
Ca(2+)-dependent crossbridge cooperativity
 
equivalently
 
force-
 
force-length area
 
heat production
 
length-
 
length-dependent prolongation
 
length-dependent twitch duration
 
linearity
 
Mathematical modelling
 
muscle length
 
pressure-volume area
 
theoretically
 
trabeculae undergoing fixed-end contractions varies linearly
 
ventricular tissue undergoing cyclic contraction
 
work performance