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Developmental changes in infant heart rate responses to head-up tilting.

Myers MM, Gomez-Gribben E, Smith KS, Tseng A, Fifer WP

Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, USA. mmm3@columbia.edu

AIM: Newborn infants produce significant heart rate responses to both head-up and head-down tilting: heart rate increases with head-up tilting and decreases with head-down tilting. However, previously we found that, at 2-4 mo of age, heart rate increases were no longer significant following slow head-up tilting. This study was designed to determine if 2-4-mo-old infants have significant increases in heart rate when tilted rapidly. METHODS: Fifty-four infants were tested as newborns or at 2-4 mo of age. Heart rate was measured while infants were tilted to a 30 degrees head-up angle either slowly over a period of 30 s or rapidly in 5 s. RESULTS: Newborns exhibited increases in heart rate using both tilt speeds; however, at 2-4 mo of age, heart rate did not change significantly using either speed of tilting. CONCLUSION: There are significant early developmental changes in cardiac responses to hypotensive challenge. Newborns react like adults, mounting sustained increases in heart rate in response to head-up tilting, but at 2-4 mo of age sustained heart rate responses are no longer significant. Tilt tests may provide a standardized method for assessing autonomic competence during the period of maximum vulnerability to sudden infant death syndrome.

Published 23 December 2005 in Acta Paediatr, 95(1): 77-81.
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