Methods: We studied 15 patients (11 men and 4 women; mean [+/-SD] age, 69+/-9 years) with central or obstructive sleep apnea who had received permanent atrial-synchronous ventricular pacemakers for symptomatic sinus bradycardia. All patients underwent three polysomnographic evaluations on consecutive nights, the first night for base-line evaluation and then, in random order, one night in spontaneous rhythm and one in dual-chamber pacing mode with atrial overdrive (basic rate, 15 beats per minute faster than the mean nocturnal sinus rate). The total duration and number of episodes of central or obstructive sleep apnea or hypopnea were analyzed and compared.

Results: The mean 24-hour sinus rate during spontaneous rhythm was 57+/-5 beats per minute at base line, as compared with 72+/-3 beats per minute with atrial overdrive pacing (P<0.001). The total duration of sleep was 321&PLUSMN;49 minutes in spontaneous rhythm, as compared with 331&PLUSMN;46 minutes with atrial overdrive pacing (P=0.48). The hypopnea index (the total number of episodes of hypopnea divided by the number of hours of sleep) was reduced from 9&PLUSMN;4 in spontaneous rhythm to 3&PLUSMN;3 with atrial overdrive pacing (P<0.001). For both apnea and hypopnea, the value for the index was 28+/-22 in spontaneous rhythm, as compared with 11+/-14 with atrial overdrive pacing (P<0.001).

Conclusions: In patients with sleep apnea syndrome, atrial overdrive pacing significantly reduces the number of episodes of central or obstructive sleep apnea without reducing the total sleep time.