The invention relates to a computer-implemented medical data processing method for determining a heartbeat signal describing the heartbeat of a patient in the time domain, the method comprising executing, on a processor of a computer, steps of: a) acquiring, at the processor, acceleration measurement data describing an acceleration in the time domain of an anatomical body part measured on an external surface of the anatomical body part； b) determining, by the processor, component analysis data describing a result of an independent component analysis in the time domain of the acceleration measurement data； c) acquiring, at the processor, heartbeat template data describing template shapes of heartbeat in the time domain； d) determining, by the processor and based on the component analysis data and the heartbeat template data, recurrent shape data describing a recurrence of certain signal shapes in the component analysis data； e) determining, based on the recurrent shape data, heartbeat signal data describing a time series of the heartbeat.
