(Circulation. 1999;99:1446-1451.)
© 1999 American Heart Association, Inc.
Clinical Investigation and Reports |
Atrial Fibrillation Detection and R-Wave Synchronization by Metrix Implantable Atrial Defibrillator
Implications for Long-Term Efficacy and Safety
From Queen Mary Hospital, the University of Hong Kong, Hong Kong, China (H-F.T., C-P.L.); St Luke's Medical Center, Milwaukee, Wis (J.S.); Academic Hospital Groningen, Groningen, Netherlands (H.C.); Sahlgrenska Sjukhuset, Göteborg, Sweden (N.E.); Hôpital Cardiologique, Lille Cedex, France (S.K.); and University of Calgary, Calgary, Alberta, Canada (D.G.W.).
Background—The long-term efficacy of atrial fibrillation (AF) detection and R-wave synchronization are critical safety requirements for the development of an implantable atrial defibrillator (IAD) for treatment of AF.
Methods and Results—The long-term efficacy of the Metrix IAD for AF detection 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 92.3% sensitivity for differentiation between sinus rhythm and AF; 2219 episodes and their electrograms stored in the device during AF detection were analyzed. 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 these, 49% were marked for synchronized shock delivery, 82% of sinus rhythm and 36% of AF R waves, respectively. All shock markers were properly synchronized and within the R wave (overall synchronization accuracy, 100%; lower 95% CL, 99.999%). Overall, 3719 shocks have been delivered via the IAD with no instance of unsynchronized shock delivery or any episode of proarrhythmia. The observed proarrhythmic risk was 0%, with an estimated maximum proarrhythmic risk of 0.084% per shock (95% upper CL).
Conclusions—The Metrix IAD can appropriately detect AF with a high specificity and sensitivity and reliably synchronize within a suitable R wave for shock delivery to minimize the risk of ventricular proarrhythmia.
Key Words: fibrillation • atrium • heart-assist device • defibrillation
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