Phonocardiograms were recorded in a population of normal children and adolescents (116 subjects) in order to evaluate variables which might affect splitting of the second heart sound. Tracings were recorded during normal respiration in supine and sitting positions.
Position was the major variable affecting splitting. Eighty-five percent of this population exhibited greater variation in splitting when sitting than while supine. In the remainder of the subjects, the splitting variation was greater in the supine position.
Heart rate, sex, age, height, and weight had little or no effect on the splitting pattern of the second sound; 15% of the subjects exhibited fixed splitting of the second sound in either, but not both, the supine and upright positions. This was defined as less than 10 msec variation in splitting during normal respiration. This observation indicates the necessity of assessing the second sound in both supine and upright positions before a judgment is made concerning the existence of an abnormal splitting pattern.
Pubertal growth in normal Thai children: a longitudinal study