Non-invasive Cardiac Monitoring in Pregnancy: Impedance Cardiography versus Echocardiography

OBJECTIVES: The objective of this study was to report thoracic impedance cardiography (ICG) measurements and compare them to echocardiography (echo) measurements throughout pregnancy and in varied maternal positions. METHODS: A prospective cohort study involving 28 healthy parturients was performed using ICG and echo at three time points and in two maternal positions. Pearson correlations, Bland-Altman plots and paired t-tests were used for statistical analysis. RESULTS: Significant agreements between many but not all ICG and echo contractility, flow and resistance measurements were demonstrated. Differences in stroke volume due to maternal position were also detected by ICG in the antepartum period. Significant trends were observed by ICG for cardiac output and thoracic fluid content (TFC) (p < 0.025) with advancing pregnancy stages. CONCLUSIONS: ICG and echo demonstrate significant correlations in some but not all measurements of cardiac function. ICG has the ability to detect small changes in SV associated with maternal position change. ICG measurements reflected maximal cardiac contractility in the antepartum period yet reflected a decrease in contractility and an increase in TFC in the postpartum period.