New Clarity DDDR pacemaker system (Vitatron Medical B.V.) Clarity DDDR, provides an option for recognizing sudden rate drop and responding by intervention pacing until it detects the recovering. In patients in whom syncopal episodes are mainly caused by occasional drops in heart rate, Sudden Rate Drop Intervention feature intends to provide high rate intervention pacing. We have implanted 10 of these devices in our Centre, 2 of which in patients with hypersensitive carotid sinus syndrome. In patients with carotid sinus syndrome it is possible to provoke this situation by sinus caroticus massage. In both patients, we activated Sudden Rate Drop Intervention on DDD mode pacing and used protocol for testing the necessary level of sudden Rate Drop Intervention Rate. Both patients gave their informed consent to be submitted to this testing. Pacemaker software assumes rate intervention level of 110 bpm. We tested our patients for rate levels of 90 and 110 bpm. Massaging the carotid sinus during 5 seconds, we provoked sudden Rate Drop Intervention 10 times, in each patient, 5 times at intervention rate of 90 and 5 times at 110 bpm. Patients were unaware of the programmed intervention rate and were merely expected to report any different sensations experienced during the testing. In all 20 tests, pacemaker responded to sudden rate drop elicited by carotid sinus massage (100%), that was verified by selected event recordings. After the massage, no patient experienced any sensation at sudden rate drop intervention rate level of 90 bpm in a total od 10 tests (100%), while 8 of 10 messages at 110 bpm intervention rate provoked palpitations (80%). We concluded that lowering of Sudden Rate Drop Intervention Rate Level from 110 BPM to 90 BPM did not affect the reliability of system reaction, but changes of patient's awareness of heart beats. As a final conclusion, it should be said that basic prerogatives of a pacing system are: safety and efficacy with minimal energy consumption, and in this case, quality of life option that a patient practically does not feel intervention when it occurs, are all met.