EFFICACY OF A TIERED THERAPY DEFIBRILLATOR SYSTEM USED TO TREAT RECURRENT VENTRICULAR ARRHYTHMIAS REFRACTORY TO DRUGS

Objective-To evaluate an implantable tiered therapy defibrillator syst em that delivered antitachycardia pacing treatment for slower well tol erated ventricular tachycardias and cardioversion or defibrillation fo r fast tachycardias or ventricular fibrillation. Methods-A tiered trea tment device (Ventritex Cadence V-100) was implanted in 30 patients wi th ventricular tachycardia that was refractory to drugs. Efficacy was evaluated by the responses of induced or spontaneous arrhythmias to th e treatments delivered. Results-Antitachycardia pacing successfully te rminated 80% of episodes of ventricular tachycardia induced by non-inv asive programmed stimulation, but acceleration was brought about by pa cing in six patients in 10% of episodes. During a follow up of two to 17 (mean seven) months, 18 patients (60%) had recurrence of ventricula r arrhythmias. Antitachycardia pacing terminated ventricular tachycard ia in 17 of 18 patients in 87% of episodes. Twelve patients received s hocks for ventricular tachycardia or fibrillation. Failure of pacing, with subsequent cardioversion, occurred in nine patients (50%) in one or more episodes. Acceleration of tachycardia by pacing occurred in 10 patients in 5% of episodes. Only two of these patients had experience d acceleration of previously induced arrhythmia. Five patients had spo ntaneous fast ventricular tachycardia or fibrillation treated by cardi oversion or defibrillation. Spurious treatment was delivered in nine p atients (30%), during atrial fibrillation in five, sinus tachycardia i n two, and because of fracture of the sensing lead system in two patie nts. The retrieval of stored intracardiac electrograms was of clinical value in assessing spurious treatment. Conclusions-Tiered treatment w as effective in terminating recurrent ventricular arrhythmias in these selected patients. Most episodes were treated successfully by pacing, and resistant tachycardias, pacing induced acceleration, or haemodyna mically compromising arrhythmias were treated by shocks.