Objectives: This study was conducted to assess the effectiveness of antitachycardia pacing modes and detection algorithms in patients with a new third-generation implantable cardioverter-defibrillator.
Methods: Twenty-three of 42 consecutive patients had coronary artery disease, 14 had dilated cardiomyopathy, 2 had prior valve replacement and 3 had arrhythmogenic right ventricular dysplasia. The mean ejection fraction was 41 +/- 14%; there were 31 men (74%) and 11 women, with a mean age of 53 years. On the basis of preoperative and postoperative electrophysiologic studies, in 28 patients antitachycardia pacing was postoperatively programmed randomly as "burst" (66%) or autodecremental "ramp" (34%) stimulation with a first coupling interval of 81% of tachycardia cycle length and up to 8 sequences with 3 to 10 stimuli.
Results: During a follow-up interval of 6.3 +/- 2.2 months, 15 patients were treated by antitachycardia pacing for a median of 6 (range 1 to 59) hemodynamically stable ventricular tachycardias (175 +/- 12 beats/min). In 5 patients, 22 ventricular tachycardias (9%) were not terminated by antitachycardia pacing but by cardioversion. Seven (3%) of these episodes accelerated (> 50 ms) during antitachycardia pacing. Syncope did not occur during these episodes. In seven patients initial antitachycardia pacing in cases of supraventricular tachycardias delayed charging and redetection prevented inappropriate discharges. Additional detection algorithms were programmed only after inappropriate therapy. The sudden "onset" and "sustained rate duration" criteria were programmed in three patients and the cycle length "stability" criteria in six patients, respectively. After activation of these detection algorithms only two of the seven patients had further inappropriate device discharges.
Conclusions: Thus, antitachycardia pacing by this implantable cardioverter-defibrillator effectively and appropriately terminated 91% of hemodynamically stable ventricular tachycardias. Inappropriate device discharges were prevented in some patients by antitachycardia pacing and additional detection algorithms.