ABSTRACT
This study examines the circadian variation of aortic blood flow velocity, acceleration,
and distance of stroke, assessed every 4 hours for 24 hours by Doppler ultrasound
in 88 human newborns. Groups 1 and 2 involve neonates with a negative family history
of high blood pressure or myocardial infarction monitored during the first day or
between the second and tenth days postpartum, respectively; groups 3 to 6 are 2- to
10-day-old babies with a positive family history of high blood pressure (group 3)
or of myocardial infarction (group 4) or with a negative family history and intrauterine
growth retardation (group 5) or born prematurely (group 6). Cosinor analyses demonstrate
a circadian rhythm for all variables in groups 2 and 5 (p <0.001), with overall high
values occurring around 17:40. In group 2, a circadian rhythm remains demonstrable
in boys and girls considered separately, and mostly so in arbitrary subgroups of different
sizes, with only slight differences in rhythm parameters among them. These results
show that, with relatively small samples, reproducible circadian rhythms of cardiac
function can be detected shortly after birth in neonates with a negative family history
of high blood pressure or myocardial infarction.
