Design and preliminary data of the Metrix (TM) Atrioverter Expanded Indication Trial

The Metrix(TM) Atrioverter Expanded Indication Trial evaluates the safety a nd efficacy of an implantable atrial defibrillator in patients with symptom atic, recurrent and drug refractory atrial fibrillation who also have struc tural heart disease. In this ongoing multicenter study, all patients are an ticoagulated and concomitant antiarrhythmic drug treatment is left to the p reference of the physician. Holter monitoring is performed prior to enrollm ent in the study. Spontaneous episodes of atrial fibrillation (AF) are trea ted under physician observation and when patients are ambulatory, the devic e is programmed in a monitoring mode. The atrial defibrillation threshold i s measured at implantation and at 3, 6 and 12 months thereafter. The perfor mance of the AF detection and R-wave synchronization algorithm is assessed at implantation, at regular follow-up intervals, and each time the patient visits the hospital for treatment of a spontaneous episode of AF. An echoca rdiogram is performed prior to implantation, at 3 and 6 month follow-up and for patients with an implanted heart valve, after 20 and 50 atrial defibri llation shocks have been delivered. The study started on October 1997 and w ill end after the last patient enrolled completes his/her six-month post-im plantation follow-up, unless a safety issue arises. As of September 1998, 6 patients (2 patients with tachycardia induced cardiomyopathy, 1 patient wi th a mitral valve prosthesis, 2 patients with hypertrophic cardiomyopathy a nd 1 patient with congenital heart disease) have been enrolled in the study . Over 350 shocks have been delivered for atrial defibrillation testing or termination of spontaneous AF episodes. There have been no reported cases o f ventricular proarrhythmia or inaccurately synchronized shocks and no comp lications of device therapy in this population.