PP and PR interval variations in pediatric subjects being evaluated for obstructive sleep apnea

This work considers measures of RR, as a surrogate to the PP inrerval, and PR intervals in pediatric subjects with mildkevere obstructive sleep apnea, and control subjects. Analysis is carried out in a total of 50 subjects (ages 1-16 y, mean 8.7), of which 22 are control (AH1 0.06 +/-a. I3), I7 are mild, and I I are severe. A range of time domain features of RR and PR intervals were considered, with six measures showing statistical diyerences between control and apneic subjects. Spectral features (low frequency component of RR, and high frequency component of PR) also provided statistically significant differences between classes. Further time domain analysis was carried out by calculating the average RR and PR interval sequences in response to an obstructive event. The average RR sequence contained the well-known bradycardidtachycardia swing. However, in most obstructive sleep apnea subjects (2 I out of 28), the average PR sequence was out of phase with the RR pattern, indicative of a predominance of refractory effects in setting the AV condu.ction time in these subjects.