Abstract: A method is provided for characterizing autonomic nervous system activity of a patient based on heart rate variability analysis using electrocardiographic data from the patient. In addition, a computer-readable medium is provided tangibly embodying a program of instructions executable by a computer to perform a method for characterizing autonomic nervous system activity of a patient based on heart rate variability analysis using electrocardiographic data from the patient. Also, a system is provided for characterizing autonomic nervous system activity of a patient comprising a processor and a machine-readable medium tangibly embodying a program of instructions executable by the processor.