Introduction: Maternal vascular adaptation to pregnancy involves the coordinated augmentation of both systemic and uteroplacental circulations, with the concomitant development of a new fetoplacental circuit. Disturbances of maternal hemodynamic adaptation in early pregnancy are often associated with compromise in the other circulations, although the assessment of maternal vascular function by conventional means is cumbersome and expensive.
Objectives: We sought to assess maternal hemodynamic function with a noninvasive cardiographic monitor, and to correlate the findings to both uteroplacental and fetoplacental vascular resistance.
Methods: We measured cardiac output and index (CO,CI), systemic vascular resistance (SVR), mean arterial pressure (MAP) and an index of contractility (ICON) with a novel electrical impedance cardiograph (Aesculon EIC System, Cardiotronic, USA) that provides a volume independent estimate of cyclical blood flow velocity. We enrolled high-risk subjects between 22 and 25weeks who were referred for assessment of fetal growth and uterine artery Dopplers due to abnormalities of serum screening analytes or other risk factors for preeclampsia. Doppler measurements of blood flow in the uterine arteries (pulsatility index, PI) and umbilical artery (systolic: diastolic ratio, S/D) were obtained by ultrasound (Voluson E8, GE Healthcare, Inc.), along with the fetal weight percentile (FW%). Data were expressed as medians (+/- range), and analyzed with Spearman's correlation coefficient, R. Statistical significance was set to p=0.05.
Results: Electrical impedance cardiography (EIC) data was collected from seventeen subjects. There were no measurement failures. The median gestational age was 24.3weeks and the BMI was 26.4 (21-47). The median PI, S/D and FW% were 0.96 (0.47-2.1), 3.3 (2.6-7.1), and 53% (6-82%). EIC results and their relationship to uterine and umbilical Dopplers and fetal growth are shown in Table 1. There were no significant correlations between maternal systemic hemodynamic parameters and uterine artery PI. On the other hand, maternal cardiac function was strongly related to the umbilical artery S/D ratio, and SVR was uniquely related to the FW%.
Conclusion: Maternal systemic hemodynamics can be conveniently acquired by EIC at the same time as routine obstetrical imaging. Our data suggest that maternal cardiovascular adaptation more closely reflects the fetoplacental circulation than the uteroplacental circulation in women at moderate risk of preeclampsia. EIC may be a useful adjunct in assessing risk of fetal compromise.
Copyright © 2012. Published by Elsevier B.V.