Heart rate modifications related to spontaneous body movements in sleeping premature and full-term newborns

Heart rate (HR) acceleration is an essential mechanism for adaptation to changes in hemodynamic and energetic needs resulting from body movements. To evaluate age-related development of coupling between spontaneous movement and HR changes, we performed polysomnographic recordings in 20 clinically and neurologically normal newborns including 10 premature (31- to 36-wk gestational age, wGA) and 10 full-term (38- to 41-wk gestational age) infants. Recordings were sampled at 286 Hz and processed using a signal-to-noise ratio algorithm for QRS complex detection. Movements were automatically detected and the logical signal obtained was sampled at QRS fiducial points and written in the attributes of each QRS. The study included the 402 movements that were less than 30 s in duration and were neither preceded nor followed by another movement or by a respiratory event (pause, sigh). The amplitude of movement-induced HR acceleration was significantly lower in premature compared with full-term newborns (p < 0.01). This difference persisted when the other factors influencing the HR response (basal HR, movement duration, and amplitude) were taken into consideration. Our data identify HR acceleration induced by spontaneous body movements as a fundamental reflex response that develops with gestational age from premature to full-term newborns.