Detection of atrial fibrillation during sinus tachycardia induced by exercise in patients with implantable atrial defibrillators

Accurate detection of atrial fibrillation (AF) is essential for appropriate operation of an implantable atrial defibrillator (IAD). However, during ep isodes of sinus tachycardia, distinction between AF and sin us rhythm ISR) using the "quiet interval" and "baseline crossing" analysis in the detectio n algorithm of the IAD may be difficult. The efficacy of this AF detection algorithm was tested in five patients implanted with an IAD (METRIX: Model 3000 or 3020, InControl Inc.) during treadmill exercise testing. The IADs w ere programmed to Monitor Mode with a wake up cycle of 1 minute for AF dete ction using the device nominal parameters or modified parameters, and to ma rk rhythms appropriate for shock delivery. A mean peak heart rate of 137 +/ - 26 beats/min was reached during maximum exercise, and one patient develop ed transient AF. Seventy-eight (75 in SR, 3 in AF) and 91 (89 in SR, 2 in A F) runs of AF detection were performed using the nominal and modified param eters, respectively. The IAD detected AF and SR accurately except for one e pisode of false-positive AF detection during sinus tachycardia at the nomin al settings, but inappropriate shocks were prevented by minimum RR interval criteria that limited discharge at high heart rate. These results indicate that the AF detection algorithm in the IAD may become more vulnerable to f alse-positive AF detection during sinus tachycardia, which were avoided by reprogramming the Quiet Interval and minimum RR interval criteria for AF de tection. Exercise testing appeared useful to program optimal settings of th e IAD in preparation for daily activities.