Poster No. 53
Title:
What Determines Myocardial Velocities in the Fetus? A Color Tissue Doppler Study Comparing Fetuses
and Premature Infants of Similar Size
Authors:
Linda Pauliks, Susan Miller, Anirban Banerjee
Presented by:
Linda Pauliks
Department(s):
Department of Pediatric Cardiology, Floating Hospital for Children, Tufts–New England Medical Center
Abstract:
Background: Myocardial velocities derived from tissue Doppler imaging could potentially be very useful
to quantitate cardiac function in the fetus since tricuspid ring velocities reflect right ventricular function in
children and adults. However, previous studies found that myocardial velocities in the fetus are much lower
and more variable than postnatally limiting their clinical utility. It is unclear whether these differences are
due to hemodynamic conditions or somatic growth. We therefore compared tissue Doppler parameters in
similar-sized subjects with fetal and newborn circulation patterns using this as a model to assess the
determinants of myocardial velocities.
Methods: The study included matched groups of 12 premature infants (gestational age 28±5 weeks) and
13 healthy fetuses (25±5 weeks; n. s.). Infants were 4.5±5.2d old and weighed 1.25±0.86 kg. Color
myocardial Doppler imaging was performed from apical 4-chamber views at high frame rates (>100/s,
mean 204±79/s). Peak systolic (S) velocity in the basal septum, diastolic septal length and mid-septum peak
systolic strain rate (SR) were measured.
Results: Despite the significant hemodynamic changes after birth, the fetal group and premature group had
similar S velocities with 2.2±0.6 cm/s in the newborn vs. 2.0±0.5 cm/s in the fetus (n. s.). S velocities
correlated with gestational age and septal length. However, the correlation between septal length and
S velocities was strongest (R=0.89; p<0.001). Infants had slightly higher heart rates (156±15/min vs. fetus
142±15/min; p<0.05) but heart rate did not correlate with S velocities. In contrast to velocities, SR did not
correlate with gestational age and was similar in both groups (newborn -1.7±0.4/s vs. fetus -1.7±0.3/s; n. s).
Conclusions: 1. Our data suggest that somatic growth is a major determinant of myocardial velocities early
in life. Longitudinal growth of the walls adds more contractile elements (with similar strain rate) thereby
building up basal velocities. 2. This could be useful to assess velocities in those cases where dates are
uncertain or in the presence of intrauterine growth retardation. We present a simple method to correct
myocardial ring velocities for these descrepancies in fetal size by measuring the length of the
interventricular septum.
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