Abstract
The interaction between cardiomyocyte contraction and organ level dynamics was investigated to assess the physiological significance of the length-dependent force generation. We developed a simple hypothetical circulation model consisting of 3 components, a single ventricle, a preload and an afterload. The Kyoto model of a single cardiomyocyte was combined with the circulation model and we implemented the contraction process using the NL model (Negroni & Lascano, 1996). A thin-walled spheric geometry is used as a rough estimate of the left ventricle. We employed the Laplace law to convert the wall tension to the intraventricular pressure assuming uniform wall tension in all direction. Using this model, the relationship between the contraction of cardiomyocyte and the ventricular ejection-fraction (EF) was investigated. Computational results suggested that the EF value obtained by using the original NL model was less than 30% because the force generation during systole was strongly inhibited by the cell shortening. An improved result of the EF > 60% was achieved by a slight modification in the length-dependency on force generation. It was also shown that the EF could be increased assuming the dead space occupied by the papillary muscles within a ventricular cavity. [Jpn J Physiol 55 Suppl:S94 (2005)]
