Atrial fibrillation detection and R-wave synchronization by Metrix implantable atrial defibrillator - Implications for long-term efficacy and safety

Background-The long-term efficacy of atrial fibrillation (AF) detection and R-wave synchronization are critical safety requirements for the developmen t of an implantable atrial defibrillator (LAD) for treatment of AF. Methods and Results The long-term efficacy of the Metrix IAD for AF detecti on and R-wave synchronization was tested in 51 patients. The mean duration of follow-up was 259 +/- 138 days (72 to 613 days), AF detection tests were performed 2240 times during observed operation with 100% specificity and 9 2.3% sensitivity for differentiation between sinus rhythm and AF; 2219 epis odes and their electrograms stored in the device during AF detection were a nalyzed. The positive predictive value of the AF detection algorithm was 97 .4% (lower 95% confidence limit [CL], 94.5%) in the out-of-hospital setting . A total of 242 435 R waves were analyzed for R-wave synchronization. Of t hese, 49% were marked for synchronized shock delivery, 82% of sinus rhythm and 36% of AF R waves, respectively. All shock markers were properly synchr onized and within the R wave (overall synchronization accuracy, 100%; lower 95% CL, 99.999%). Overall, 3719 shocks have been delivered via the LAD wit h no instance of unsynchronized shock delivery or any episode of proarrhyth mia. The observed proarrhythmic risk was 0%, with an estimated maximum proa rrhythmic risk of 0.084% per shock (95% upper CL). Conclusions-The Metrix IAD can appropriately detect AF with a high specific ity and sensitivity and reliably synchronize within a suitable R wave for s hock delivery to minimize the risk of ventricular proarrhythmia.