A quantitative understanding of the heart function is crucial for several cardiac therapies, ranging from ablation or resynchronization therapy to valve replacement. The electrical myocard excitation is described by the mono- or bidomain equations, a set of reaction-diffusion equations for the transmembrane voltage and a set of pointwise ODEs for the ion concentrations and ion channels. Due to very different temporal and spatial scales involved, the numerical simulation is rather expensive. In this project we develop different structure-exploiting integration methods for mono- and bidomain equations, in order to reduce the computational effort while controlling the discretization error.