Interactive simulation of the activation sequence: Replacing effect by cause

Electrocardiographic wave forms during the QRS interval reflect the activation sequence of the heart. This can be demonstrated in ECGSIM, an interactive software package aimed to support ECG education and research. When using this package, the timing of activation may be changed interactively, either locally or globally. The resulting QRS changes are displayed instantaneously. We describe a new feature which permits the user to interactively change of the spatial distribution of the propagation velocity. This new feature enhances the teaching and research capabilities of ECGSIM, e.g. for simulating the activation under ischemic circumstances or during ectopic activation, and investigate the interaction between the Purkinje system and the myocardial tissue.