Clinical experience with implantable atrial and combined atrioventricular defibrillators

The high prevalence of atrial fibrillation (AF) and its clinical complicati ons, the poor efficacy of medical therapy for preventing recurrences, and d issatisfaction with alternative modes of therapy stimulated interest in imp lantable atrial and combined atrioventricular defibrillators. In a multicenter study, the safety and efficacy of a stand alone implantabl e atrial defibrillator, the Metrix system, were evaluated. The device was i mplanted in 51 patients with highly symptomatic episodes of AF refractory t o pharmacological treatment. During a follow-up of 9 months, 96% of 227 spo ntaneous AF episodes were successfully converted to sinus rhythm in 41 pati ents. In 62 episodes (27%), several shocks and/or additional drug treatment were required to maintain stable sinus rhythm because of early recurrences of AF. A total of 3719 shocks were delivered and no induction of ventricul ar proarrhythmia or inaccurately synchronized shocks occurred. The AF detec tion algorithm exhibited a 100% specificity for the recognition of sinus rh ythm and a 92.3% sensitivity for the detection of AF. The combined atrioventricular defibrillator, Jewel AF 7250, was evaluated i n a multicenter, randomized, cross-over trial. The primary study objectives included: overall safety as determined by complications-free survival at 6 months, efficacy of tiered atrial pacing and defibrillation therapies for termination of spontaneous atrial tachycardias (AT) and AF, and relative se nsitivity of a new dual-chamber detection algorithm. The device was implant ed in 211 patients with either a history of ventricular tachyarrhythmias (V T/VF) alone or with a history of both AT/AF and VT/VF. During a mean follow -up of 4.5 months, it has been shown that the Jewel AF is safe and effectiv e in treating atrial and ventricular tachyarrhythmias. Pace termination of 85% of AT episodes were achieved with painless delivery of antitachycardia pacing; additional 35% of AT episodes were terminated by high frequency bur st pacing. Conclusions: The stand alone implantable atrial defibrillator may be safe a nd clinically useful in selected patients for the treatment of highly sympt omatic, drug resistant recurrences of AF. The combined atrioventricular def ibrillator may be particularly indicated in patients presenting with both a history of atrial and ventricular tachyarrhythmias.