Agreement between preload reserve measured by impedance cardiography and echocardiography during pregnancy

Abstract

PurposeAccurate assessment of cardiac function is important during pregnancy. Echocardiography and impedance cardiography (ICG) are commonly used noninvasive methods to measure stroke volume (SV) and cardiac output (CO). The difference in stroke volume (ΔSV) or cardiac output (ΔCO) measured at baseline and after passive leg raising (PLR) is a measure of preload reserve that predicts volume responsiveness. However, the agreement between these two methods in measuring preload reserve during pregnancy is unclear. The aim of our study was to investigate the correlation and the agreement between Doppler echocardiography and ICG in assessing preload reserve in pregnant women.MethodsIn this prospective observational cross-sectional study, preload reserve was assessed by measuring the SV and CO during baseline and 90 s after PLR simultaneously by Doppler echocardiography and ICG in healthy pregnant women during the second and third trimesters. Bland–Altman analysis was used to determine the agreement between the two methods. Bias was calculated as the mean difference between two methods and precision as 1.96 SD of the difference.ResultsA total of 53 pregnant women were included. We found a statistically significant correlation between ΔSV (R = 0.56, p < 0.0001) and ΔCO (R = 0.39, p = 0.004) measured by ICG and Doppler echocardiography. The mean bias for ΔSV was 2.52 ml, with a precision of 18.19 ml. The mean bias for ΔCO was 0.21 l/min, with a precision of 1.51 l/min.ConclusionThere was a good agreement and a statistically significant correlation between ICG and Doppler echocardiography for measuring preload reserve.

Maternal functional hemodynamics in uncomplicated twin pregnancies: A longitudinal study using impedance cardiography

“…Although a reduction in myocardial contractility might represent one of the underlying mechanisms leading to myocardial inability to increase SV in response to PLR, compromised venous return due to caval compression and fluid shifts, including positioning of breast tissue, with the postural change could be another reason for the lack of positive response to PLR, as well as the small sample size. Indeed, Guy et al demonstrated a significant increase of only 3% in cardiac index and SI with PLR starting from the left lateral decubitus in 2764 singleton pregnancies near term In contrast, Liang et al reported no difference starting from a semi‐recumbent position in 53 singleton pregnancies in the second and third trimester …”

“…Although its use has been controversial and it is not interchangeable with echocardiography, Burlingame et al demonstrated a significant correlation between ICG and echocardiography during pregnancy. In addition, modest agreement and significant correlation with echocardiography in measuring SV and CO variation after PLR have been demonstrated in singleton pregnancies . Compared with echocardiography, ICG is able directly to evaluate myocardial pump function, SV and thoracic fluid content, and changes can be measured instantaneously and monitored continuously.…”

“…Moreover, the study cohort did not consist of a homogeneous ethnic population. The accuracy of measuring hemodynamics using ICG has been questioned, but this technique has been validated in pregnant populations and significantly correlates with echocardiography, also during PLR . Moreover, a new generation of ICG devices and recent updates in the ICG signal analysis software have improved ICG measurement accuracy .…”

“…At each visit, baseline measurements were performed after 5 minutes of rest with the participant lying in a 45° supine semi‐recumbent position (semi Fowler's position) on a bed that could change maternal position without any active movement by the study participant herself. This starting position was chosen to let the woman's leg be raised in a standardized manner to elicit effects of auto‐fluid challenge as recently validated . Women were instructed to remain quiet during ICG measurements.…”

“…PLR has been described as a method to induce a reversible “autotransfusion” offering a reversible and thus attractive tool to augment cardiac preload without affecting blood pressure and heart rate . So, PLR can be considered as a substitute for the classic fluid challenge without the risk of fluid overload and it has been recently validated against echocardiography in singleton pregnancies . However, functional hemodynamic response to PLR in twin pregnancies has not been previously reported, nor whether differences in chorionicity exist.…”