Fetal cardiac time intervals determined by Doppler echocardiography

Abstract

One-hundred and eleven Doppler echocardiographic examinations were performed on 88 normal fetuses, ranging from 16 to 41 weeks of gestation. Aortic and pulmonary maximal velocity (MV), acceleration time (AT), ejection time (ET), MV/AT (acceleration velocity: AV) and AT/ET ratio in systole were assessed on each blood flow velocity waveform. Aortic MV and pulmonary MV correlated well with gestational age, respectively. Good correlations between aortic AT, pulmonary AT and gestational age were evident. There were correlations between aortic AT/ET ratio, pulmonary AT/ET ratio and gestational age, respectively. However, there was no correlation between aortic AV, aortic ET, pulmonary AV, pulmonary ET and gestational age, respectively. These findings may relate to alterations in pulmonary and placental vascular resistance with advance in gestation.

Doppler echocardiography of the main stems of the pulmonary arteries in the normal human fetus

“…These changes are similar to the decrease in vascular resistance and arterial pressure in the lung vascular bed. The values of AT and AT/ET in the proximal pulmonary arteries were always lower than the values in the pulmonary trunk reported by other authors 15,16,33 . A possible explanation is that the pressure in the pulmonary trunk is the result of the higher pressure found in both lung arteries and the lower pressure in the peripheral circulation reflected in the ductus arteriosus.…”

“…These results were confirmed by other authors 32 and it is now generally assumed that a short AT (or an AT/ET ratio of < 0.4) correlates with a high arterial pressure and vice versa. This Doppler analysis was also used in the human fetus under normal and pathological conditions in order indirectly to determine aterial pressures in both the pulmonary trunk and the aorta 15,16,33 . Data collected serially on humans before and after delivery 34 , or from newborns from the first hours of life to 1 month of age, showed a lengthening of the AT after 6 h of life and an increase in the AT/ET ratio, which was explained by the abrupt decrease in the high vascular resistance in the pulmonary vascular bed after birth.…”

Sonographische Untersuchung des fetalen Lungenkreislaufs

“…20-40 ms im Verlauf der 2. Schwangerschaftshälfte [29], während die AT über der Pulmonalklappe in diesem Zeitraum 30-50 ms [14] und im Ductus arteriosus 55-75 ms [3] beträgt. Es ist aus der Kardiologie bekannt, daß die AT in umgekehrter Relation zum mittleren arteriellen Druck steht [19,20], d. h. eine kurze AT spricht für einen hohen Druck und vice versa.…”