ENHANCED DETECTION CRITERIA IN IMPLANTABLE DEFIBRILLATORS

Enhanced Tachycardia Detection Algorithm. Introduction: Enhanced detec tion criteria in third-generation implantable defibrillators have been implemented to avoid inappropriate therapy of fast supraventricular a rrhythmias, We prospectively analyzed the use of these criteria in pat ients with an implantable defibrillator with electrogram storing capab ility. Methods and Results: In 82 consecutive patients with a Guidant- CPI implantable defibrillator, sudden onset > 9% and stability < 40 ms ec were systematically programmed in zone 1 of therapy together with a sustained rate duration security mechanism. All detected tachycardia episodes were analyzed, The study population consisted of 59 patients who had at least one episode of tachycardia detected in zone 1 during follow-up. The tachycardia rate in zone 1 never exceeded 210 beats/min , Twenty patients had no episodes during follow-up, and three patients had episodes detected exclusively in zone 2 of therapy, Supraventricu lar arrhythmias were detected frequently in the ventricular tachycardi a zone (193 of 690 tachycardia episodes in 23 of 59 patients), Use of sudden onset was very effective in detecting sinus tachycardias (65 of 67 episodes), and stability was very useful in detecting atrial fibri llation (31 of 32 episodes), However, sensitivity in detecting ventric ular tachycardia was only 90% (451 of 497 episodes), Application of th e sustained rate duration criterion allowed appropriate treatment of a ll ventricular tachycardia episodes, increasing sensitivity to 100%; h owever, specificity in appropriate nontreatment of supraventricular de creased from 96% to 83%, Subsequent analysis of different algorithms a pplied to our data showed that sudden onset > 9% and stability < 40 ms ec was the algorithm with the best specificity and sensitivity. Conclu sion: Programming sudden onset and stability detection criteria with a sustained irate duration safety net for triggering tachycardia therap y results in appropriate device management in most patients with supra ventricular and slow (< 210 beats/min) ventricular tachycardias.