Automatic adaptation of the basic pacing rate in response to minute ventilation. Chorum French Investigational Group

Rate responsive pacing based on minute ventilation (VE) correlates highly with metabolic demand. This type of sensing also recognizes extended periods of rest. The Chorum pacemaker includes a rate responsive algorithm that modulates the basic rate according to phases of activity versus sleep. Forty-six patients (mean age 78 +/- 15), received a Chorum pacemaker for atrioventricular block in 17 cases, sick sinus syndrome in 25, and mixed disorders in 4. Holter monitoring was performed to analyze to heart rate and to examine the circadian adaptation of the minimal pacing rate. The mean basic rate was programmed at 63 +/- 5 beats/min, and the sleep rate at 52 +/- 4 beats/min. Seventeen patients had spontaneous heart rates consistently above the programmed basic rate, and 6 had sustained supraventricular tachyarrhythmias. One-half of the patients had periods of pacing at the programmed sleep rate. The mean diurnal pacing rate was 68 +/- 5 beats/min compared to a mean nocturnal rate of 60 +/- 4 beats/min (P < 0.0001). The average time spent at the basic rate was 37 +/- 30 min (0-110) during daytime (4%), versus 242 +/- 153 min (20-477) at night (45%, P < 0.0001). No adverse effect was observed in this patient population. VE allows a reliable detection of the sleeping periods as well as an adjustment of the basic rate in accordance. Caution is advised in cases of bradycardia dependent tachyarrhythmias.