The invention relates to a device for a medical intervention in or on moving tissue of a living being, said device having a medical instrument provided for the intervention, a position detection system by means of which the position of the medical instrument in the body of the living being can be determined, and at least one acceleration sensor for recording at least one movement of the instrument caused by the moving tissue. The invention also relates to a medical instrument for a medical intervention in or on moving tissue of a living being, said medical instrument having at least one acceleration sensor and a sensor of a position detection system, as well as to an operating method for the device.