QT dynamicity, microvolt T-wave alternans, and heart rate variability during 24-hour ambulatory electrocardiogram monitoring in the healthy newborn of first to fourth day of life.

Background: Twenty-four hour ambulatory electrocardiogram (AECG) monitoring is an established technique for integrated assessment of heart rhythm; however, comprehensive description of serial changes in cardiac electrophysiology over the first days of life in humans is lacking. The aim of this study was to determine the patterns of circadian heart rhythm based on AECG evaluation in newborns.

Methods: Twenty healthy newborns (14 boys and 6 girls) were serially examined with AECG at days 1, 2, and 4 after birth.