The product has a function element (5) e.g. rotation pump or stent, inserted into a body of a patient, and a main sensor (6) staying in fixed connection with the function element. A processing device receives signals of the main sensor and determines a parameter representing position of the function element from the signals of the main sensor under consideration of electrophysiological signals of heart or brain. The processing device is connected with auxiliary sensors (7-11) and provided with a memory device for storing electrophysiological heart signals of the patient. An independent claim is also included for a method for operating a function element in a body of a patient.
