Efficacy and tolerability of automatic nighttime atrial fibrillation shocks in patients with permanent internal atrial defibrillators

Recent technologic advances have resulted in the addition of the implantable atrial defibrillator (IAD) to the therapeutic armamentarium for treatment of recurrent, symptomatic atrial fibrillation (AF). Early clinical investigations with a first-generation, stand-alone atrioverter, with a maximum 6 J output, demonstrated the efficacy of relatively low-energy shocks for terminating AF in humans. 1,2 Its applicability was limited, however, because approximately 33% of patients could not be defibrillated at less than or equal to6 J during preimplant screening.(1,2) The introduction of the atrioventricular defibrillator or arrhythmia management device (AMD) capable of automatically delivering up to 27 J to either the atria or ventricles eliminated the need for prescreening, and its backup ventricular defibrillator simultaneously addressed the concern of ventricular proarrhythmia from poorly timed atrial shocks. Despite its widespread applicability and availability, however, prescription of the AMD remains somewhat limited because patient tolerability of AF shocks remains a concern. Prior investigations have demonstrated that severe discomfort can result from internal defibrillation energies of <3 J.(3-6) This study was aimed at understanding whether nocturnal AF defibrillation shocks delivered via the AMD, using a therapy scheduling option, provides an effective and acceptable treatment strategy for patients with recurrent, symptomatic AF.