A method and apparatus for analyzing a physiological waveform. The apparatus comprising an input terminal for connection to a patient to acquire the physiological waveform from a patient, an instrumentation amplifier connected to the input terminal to filter the physiological waveform, and an analysis module including a processor and software for operating the processor to detect cyclic artifact in the physiological waveform. The method comprising the acts of obtaining the physiological waveform and determining whether there is more than one independent complex rhythm within the digital physiological waveform.