Time-interval between maternal electrocardiogram and venous Doppler waves in normal pregnancy and pre-eclampsia: a pilot study.

Abstract

Purpose: To evaluate the time-interval between maternal electrocardiogram (ECG) and venous Doppler waves at different stages of uncomplicated pregnancy (UP) and in pre-eclampsia (PE). Materials and Methods: Cross-sectional pilot study in 40 uncomplicated singleton pregnancies, categorized in four groups of ten according to gestational age: 10-14 weeks (UP1), 18–23 weeks (UP2), 28-33 weeks (UP3) and  37 weeks (UP4) of gestation. A fifth group of ten women with PE was also included. A Doppler flow examination at the level or renal interlobar veins (RIV) and hepatic veins (HV) was performed according to a standard protocol, in association with a maternal ECG. The time-interval between the ECG P-wave and the corresponding A-deflection of the venous Doppler waves was measured (PA), expressed relative to the duration of the cardiac cycle (RR), and labelled PA/RR. Results: In hepatic veins, PA/RR is longer in UP4 than in UP1 (0.48 ± 0.15 versus 0.29 ± 0.09, p ≤ 0.001). When all UP groups were compared, PA/RR increased gradually with gestational age. In PE, HV PA/RR is shorter than in UP3 (0.25 ± 0.09 versus 0.42 ± 0.14, p < 0.01) and this difference persisted under anti-hypertensive treatment (0.28 ± 0.06 versus 0.42 ± 0.14, p ≤ 0.01, n = 6). Similar results were found in both kidneys. In UP1 but not in UP3 or UP4, HV PA/RR is shorter in liver than in left and right kidney (0.29 ± 0.09 versus 0.38 ± 0.12, p < 0.01, and versus 0.36 ± 0.09, p ≤ 0.01). Conclusion: PA/RR is organ-specific and gestation-dependent, and is considered to relate to venous vascular tone and/or intravascular filling. Increased values in advanced gestational stages are consistent with known features of maternal cardiovascular adaptation. Shorter values in pre-eclampsia are consistent with maternal cardiovascular maladaptation mechanisms. Our pilot study invites for more research into the relevance of the time-interval between maternal ECG and venous Doppler waves as a new parameter to study gestational cardiovascular (patho)physiology of the maternal venous compartment by Duplex sonography.