Doppler study of the embryonic heart in normal pregnant women

To describe normal fetal cardiac and hemodynamic development in normal early first trimester pregnancies.

Eighty-eight women with singleton, uncomplicated pregnancies were prospectively studied with transvaginal ultrasound, pulsed and color Doppler. Heart diameter, heart rate, and inflow and outflow waveforms with valve signals were documented. The proportion of the cardiac cycle of isovolumetric relaxation time (IRT%) and isovolumetric contraction time (ICT%) as well as Tei index were calculated.

Ninety-one percent of studies were successful. Heart diameter and the fetal heart rate showed a positive correlation with increasing gestational age: R = 0.80 (p < 0.000001), R = 0.76 (p < 0.000001), respectively. Mean heart diameter at 6 weeks was 1.28 +/- 0.26 mm and mean fetal heart rate was 117 +/- 6 bpm compared to 3.88 +/- 0.54 mm and 171 +/- 6 bpm at 10 weeks. The inflow waveform was monophasic (atrial contraction) in all cases from 6 to 9 weeks. Eight pregnancies (9%) miscarried between 6 and 12 weeks of gestation and the heart exams were characterized by increased IRT% compared with the survivors. In survivors, IRT% decreased between 7 and 8 weeks, from 32.9 +/- 10.7% to 20.8 +/- 5.7% (p < 0.0001). ICT% decreased from 18.6 +/- 4.4% of the cardiac cycle at 8 weeks to 12.6 +/- 4.4% at 9 weeks (p < 0.0008) (after heart development period).

Doppler examination of the fetal cardiac function is possible after 5 weeks of gestation. After 8 weeks of gestation, the fetal heart is morphologically mature but has not yet achieved effective myocardial compliance. The embryonic human heart is dependent on the atrial contraction for ventricular filling throughout the period of cardiac development. Non-survivors manifest myocardial dysfunction.