This simulation models the behavior of a cardiac myocyte (heart muscle cell) according to the work by Saucerman and Bers . The model integrates cardiac myocyte electrical activity with the calcineurin pathway, which is a key aspect of the development of heart failure. The model spans large number of temporal scales to reflect how changes in heart rate as observed during exercise or stress contribute to calcineurin pathway activation, which ultimately leads to the expression of numerous genes that remodel the heart’s structure. It can be used to identify potential therapeutic targets that may be useful for the treatment of heart failure. Biochemical reactions, ion transport and electrical activity in the cell are modeled with 91 ordinary differential equations (ODEs) that are determined by more than 200 experimentally validated parameters. The application feeds differential equations into the solver to obtain results for a specified time interval (5 s for the simulation described here). Since the ODEs are stiff (exhibit fast rate of change within short time intervals), they need to be simulated at small time scales with an adaptive step size solver.