Implantable device for diagnosing and distinguishing supraventricular and ventricular tachycardias

An implantable device for diagnosing and distinguishing supraventricular and ventricular tachycardias, comprising:

• electrodes for the electrical stimulation of parasympathetic nerves which innervate the atrioventricular and/or sinus node;
• electrodes for the electrical stimulation of the atria and ventricles and/or for ventricular cardioversion/defibrillation;
• a device for producing electrical parasympathetic stimulation pulses which are passed to the electrodes;
• a detector for detecting the atrial and/or ventricular rate, by ascertaining a time interval between atrial and/or ventricular depolarization;
• a device for programming a frequency limit above which a rate of the ventricles is recognized as tachycardia;
• a device to start parasympathetic stimulation by sending a stimulation signal to the parasympathetic pulse producing device as long as the detector detects a ventricular rate above the tachycardia frequency limit;
• a comparison device, activated in the presence of a stimulation signal, for comparing a heart rate measured by the detector during parasympathetic stimulation to the heart rate prior to or without parasympathetic stimulation and/or to the frequency limit, the comparison device delivering an output signal of a first type when the heart rate does not fall below a comparison value by more than a predetermined amount and delivering an output signal of a second type when the heart rate falls below the comparison value by more than the predetermined amount, and
• an inhibition unit that responds to the output signal from the comparison device by initiating ventricular myocardial over-stimulation therapy and/or cardioversion/defibrillation therapy when the output signal of the first type is present and inhibiting ventricular myocardial over-stimulation therapy and/or cardioversion/defibrillation therepy when the output signal of the second type is present.