Abstract: Methods and apparatus for providing a single, accurate indicator of a patient's autonomic nervous system function are described. The indicator is a combination of results of a plurality of different autonomic nervous system tests performed on the patient and referenced to a cross-sectional population. In one embodiment, the results of the different autonomic nervous system tests are referenced to a limited age group of the cross-sectional population. A method according to the invention includes generating a mathematical expression for each of the autonomic nervous system tests as a function of physiological data of the cross-sectional population, inserting measured physiological data of the patient into the mathematical expressions to compute output values for each of the tests, and combining the output values to provide the autonomic function indicator.

Abstract: A method and apparatus for arrhythmia detection comprise steps and means for acquiring at least one continuous analog signal produced by an ECG system, producing at least one digital signal based on the analog signal, producing a plurality of scalar signals from the at least one digital signal, extracting features from the scalar signal, and plotting the extracted features in a feature space having a number of dimensions equal to the number of extracted features. A normal QRS complex is identified based on the population of QRS complexes located within clusters of QRS features within the feature space. Subsequent QRS complexes acquired after identification of the normal QRS complex are labeled based on a plurality of rules and the location of each subsequent QRS complex with respect to both prior and subsequent normal QRS complexes.

Abstract: Myocardial electrical stability is assessed by sampling an ECG waveform at corresponding fiducial locations for a plurality of beats and creating a scatter plot of the i.sup.th sample versus the (i- 1)th sample. A parameter .lambda. is determined which minimizes the sum of the total distances of the points of the scatter plot to an equation x(i)= 4.lambda.x(i- 1)[ 1-x(i- 1)]. The value of the parameter .lambda. is related to the electrical stability of the heart.