Objective: To study the fetal cardiac isovolumetric contraction time in normal and complicated pregnancies with placental vascular disease using a newly developed digital Doppler cardiography system.
Design: A preliminary case-control study.
Setting: Tertiary referral hospital.
Sample: One hundred and sixteen normal fetuses (20 to 40 weeks) and 55 complicated pregnancies with placental vascular disease as documented by a high systolic: diastolic ratio in the umbilical artery Doppler flow study.
Method: A digital Doppler cardiography system with a high sampling rate (4,000 Hz) was used to detect the fetal cardiac valvular movements. The isovolumetric contraction time was measured as the interval between the mitral valve closing and the aortic valve opening with a built-in scale device.
Results: In normal pregnancy the isovolumetric contraction time remained remarkably constant with gestation and fetal heart rate. Comparison between clinical outcome and the isovolumetric contraction time of the complicated fetuses who were born within a week after the last determination of the isovolumetric contraction time revealed a strong correlation between prolonged isovolumetric contraction time duration and abnormalities in the perinatal course (non-reactive fetal heart rate pattern, low pulsatility index in the fetal middle cerebral artery Doppler flow and low birthweight infant).
Conclusions: The isovolumetric contraction time is constant with gestation and fetal heart rate in normal pregnancy. In the presence of placental vascular disease a prolonged fetal isovolumetric contraction time predicts adverse outcome.