Cardiac excitation mechanisms, wavefront dynamics and strength-interval curves predicted by 3D orthotropic bidomain simulations

► We compute anodal and cathodal strength-interval curves by 3D bidomain simulations. ► The results show detailed excitation patterns elicited by break and make responses. ► We identify novel excitation mechanisms at the break/make transition of the S-I curves. ► The model includes intramural fiber rotation and orthotropic anisotropy. ► The LRd model is augmented with the electroporation, outward, and funny currents.