Measuring and Modelling the Effect of Inorganic Phosphate on Cross-bridge Mechanics in Human Cardiac Muscle.

Many common chronic diseases operate at the intersection of metabolic and cardiovascular dysfunction. In order to model the effects of these diseases and investigate underlying causes we are developing a cardiomyocyte model which incorporates both the mechanics and metabolic factors that underlie work done by the heart. In this paper we present the first experimental results from our study measuring mechanical properties in human cardiac trabeculae, including the effect of inorganic phosphate (Pi) on the complex modulus at 37 °C. Extending our previous mathematical model, we have developed a computationally efficient model of cardiac cross-bridge mechanics which is sensitive to changes in cellular Pi. This extended model was parameterised with human cardiac complex modulus data. It captured the changes to cardiac mechanics following an increase in Pi concentration that we measured experimentally, including a reduced elastic modulus and a right-shift in frequency. The human cardiac trabecula we studied had a low sensitivity to Pi compared to what has been previously reported in mammalian cardiac tissue, which suggests that the muscle may have cellular compensatory mechanisms to cope with elevated Pi levels. This study demonstrates the feasibility of our experimental-modelling pipeline for future investigation of mechanical and metabolic effects in the diseased human heart.Clinical Relevance- This study presents the first measurement of the effect of Pi on the stiffness frequency response of human cardiac tissue and extends an experimental-modelling framework appropriate for investigating effects of disease on the human heart.