Detection of atrial fibrillation and flutter by a dual-chamber implantablecardioverter-defibrillator

Background-To distinguish prolonged episodes of atrial fibrillation (AF) th at require cardioversion from self-terminating episodes that do not, an atr ial implantable cardioverter-defibrillator (ICD) must be able to detect AF continuously for extended periods, The ICD should discriminate between atri al tnc tachycardia/flutter (AT), which may be terminated by antitachycardia pacing, and AF, which requires cardioversion. Methods and Results-We studied 80 patients with AT/AF and ventricular arrhy thmias who were treated with a new atrial/dual-chamber ICD. During a follow -up period lasting 6 +/- 2 months, we validated spontaneous, device-defined AT/AF episodes by stored electrograms in all patients, In 58 patients, we performed 80 Holter recordings with telemetered atrial electrograms, both t o validate the continuous detection of AT/AF and to determine the sensitivi ty of the detection of AT/AF. Detection was appropriate in 98% of 132 AF ep isodes and 88% of 190 AT episodes (98% of 128 AT episodes with an atrial cy cle length <300 ms). Intermittent sensing of far-field R waves during sinus tachycardia caused 27 inappropriate AT/AF detections: these detections las ted 2.6 +/- 2.0 minutes. AT/AF was detected continuously in 27 of 28 patien ts who had spontaneous episodes of AT/AF (96%). The device memory recorded 90 appropriate AT/AF episodes lasting >1 hour, for a total of 2697 hours of continuous detection of AT/AF. During Holter monitoring, the sensitivity o f the detection of AT/AF (116 hours) was 100%; the specificity of the detec tion of non-AT/AF rhythms (1290 hours) was 99.99%. Of 166 appropriate episo des detected as AT, 45% were terminated by antitachycardia pacing. Conclusions-A new ICD detects AT/AF accurately and continuously. Therapy ma y be programmed for long-duration AT/AF, with a low risk of underdetecrion. Discrimination of AT from AF permits successful pacing therapy for a signi ficant fraction of AT.