1. A method of analysing a biomedical signal having a repetitive signal feature, comprising the steps of segmenting each of a plurality of said repetitive signal features in the biomedical signal, analysing one or more of the segments to find the values of a plurality of parameters describing the shape of said one or more of the segments, said plurality of parameters constituting components of a shape descriptor vector for that segment, recording the values, and tracking changes in the said values through the biomedical signal; the method further comprising the step of defining normality for said shape descriptor vector, and calculating for each of said plurality of repetitive signal features the difference between its shape descriptor vector and normality.