Abnormal heart rate response to hypercapnia in boys with an apparent life-threatening event.
OBJECTIVE
To determine instantaneous cardiac variability responses to increased carbon dioxide (CO2) during quiet sleep in infants who may be at risk for the Sudden Infant Death syndrome (SIDS).


METHODS
The cardiac rate variability before, during and after a CO2 challenge was examined in 41 infants who had experienced an apparent life-threatening event (ALTE) and 41 gender- and age-matched control infants.


RESULTS
The ALTE infants responded to CO2 breathing with a significant increase in R-R intervals, i.e. decreases in heart rate, compared to the controls (45.1% increase in R-R intervals vs. 41.4%; p = 0.005). The differences between ALTE infants and controls depended primarily on the boys' responses.


CONCLUSIONS
ALTE infants, particularly ALTE boys, have an autonomic dysfunction-lower sympathetic stimulation and/or inhibited vagal withdrawal when stressed with CO2. The outcome might provide clues to the mechanisms underlying the cardiovascular processes contributing to the terminal event in SIDS.
Edner
A
A
Department of Woman & Child, Karolinska Institute, Stockholm, Sweden. Ann.Edner@kbh.ki.se
Ericson
M
M
Milerad
J
J
Katz-Salamon
M
M
D001341:Autonomic Nervous System / Q000503:physiopathology*; D002319:Cardiovascular System / Q000503:physiopathology; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012815:Signal Processing, Computer-Assisted; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D013398:Sudden Infant Death