Systems and methods that improving the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia are provided that examine frequency content and baseline information of the EGM as discriminatory signatures. Particular algorithms of the present invention that...http://www.google.com/patents/US7076289?utm_source=gb-gplus-sharePatent US7076289 - Methods and apparatus for discriminating polymorphic tachyarrhythmias from monomorphic tachyarrhythmias facilitating detection of fibrillation