Neurovegetative tests to evaluate rate responsive pace-makers

We have designed a procedure to evaluate rate-responsive pacemakers featuring rate adaptation through autonomic inputs. The proposed procedure is based on a set of neurovegetative stressors and on the analysis of the heart rate variability (HRV). The selected stressors include: controlled respiration in the supine position and during active standing, mental stress, hand grip, and non-invasive sinusoidal stimulation of carotid baroreceptors. Each test lasted five minutes. Completely or partially incompetent patients implanted with INOS/sup 2+/-CLS pacemakers (from Biotronik) were studied one month after the start of the rate-modulating program. ECG, respiration activity and non-invasive blood pressure (Finapres) were monitored. We found that the most effective stressors were active standing and hand grip. Spectral analysis was of limited value due to the distortion introduced by spontaneous beats. In conclusion, a procedure based on HRV analysis in response to selected neurovegetative stressors is able to quantify the rate adaptation of pacemakers.