Oculocardiac reflex in near miss for sudden infant death syndrome infants.

To gain insight into the role of the vagus nerve in sudden infant death syndrome (SIDS), 180 infants ranging in age from 1 to 66 weeks were examined with respect to cardiac response to ocular compression. There were 35 near-miss infants, 76 normal siblings of SIDS victims, and 69 normal control infants. Asystoles within the control group ranged from 0.3 to 1.8 seconds. Ten of 35 (28%) near-miss infants and 10/76 (13%) siblings had asystoles greater than 2.0 seconds when first tested. When statistically compared, the near-miss infants were significantly different from both the control infants and the siblings (Kruskal-Wallis procedure: P less than .01, and P less than .05, respectively). It is concluded that in the first year of life a significant number of near-miss infants have an exaggerated cardiac response to ocular compression. Furthermore, the presence of prolonged asystoles in certain siblings indicates that vagal hypersensitivity, as manifested by ocular compression, may be, in part, hereditary.