Quantitative cardiovascular magnetic resonance in pregnant women: cross-sectional analysis of physiological parameters throughout pregnancy and the impact of the supine position

Abstract

BackgroundThere are physiological reasons for the effects of positioning on hemodynamic variables and cardiac dimensions related to altered intra-abdominal and intra-thoracic pressures. This problem is especially evident in pregnant women due to the additional aorto-caval compression by the enlarged uterus. The purpose of this study was to investigate the effect of postural changes on cardiac dimensions and function during mid and late pregnancy using cardiovascular magnetic resonance (CMR).MethodsHealthy non-pregnant women, pregnant women at 20th week of gestation and at 32nd week of gestation without history of cardiac disease were recruited to the study and underwent CMR in supine and left lateral positions. Cardiac hemodynamic parameters and dimensions were measured and compared between both positions.ResultsFive non-pregnant women, 6 healthy pregnant women at mid pregnancy and 8 healthy pregnant women at late pregnancy were enrolled in the study. In the group of non-pregnant women left ventricular (LV) cardiac output (CO) significantly decreased by 9% (p = 0.043) and right ventricular (RV) end-diastolic volume (EDV) significantly increased by 5% (p = 0.043) from the supine to the left lateral position. During mid pregnancy LV ejection fraction (EF), stroke volume (SV), left atrium lateral diameter and left atrial supero-inferior diameter increased significantly from the supine position to the left lateral position: 8%, 27%, 5% and 11%, respectively (p < 0.05). RV EDV, SV and right atrium supero-inferior diameter significantly increased from the supine to the left lateral position: 25%, 31% and 13% (p < 0.05), respectively. During late pregnancy a significant increment of LV EF, EDV, SV and CO was observed in the left lateral position: 11%, 21%, 35% and 24% (p < 0.05), respectively. Left atrial diameters were significantly larger in the left lateral position compared to the supine position (p < 0.05). RV CO was significantly increased in the left lateral position compared to the supine position (p < 0.05).ConclusionsDuring pregnancy positional changes affect significantly cardiac hemodynamic parameters and dimensions. Pregnant women who need serial studies by CMR should be imaged in a consistent position. From as early as 20 weeks the left lateral position should be preferred on the supine position because it positively affects venous return, SV and CO.

Left Recumbent Position Decreases Heart Rate without Alterations in Cardiac Autonomic Nervous System Activity in Healthy Young Adults

“…Besides, we demonstrated that there were no alterations in SV, CO, E, or E/A between the supine and the left recumbent positions. Our findings support Rossi's report, in which cardiovascular magnetic resonance failed to show any significant differences in left ventricular end-systolic or end-diastolic volumes in 5 non-pregnant women during the left recumbent position compared to the supine position (Rossi et al 2011). Therefore, in healthy young adults, a decrease in HR in the left recumbent position could be a physiological phenomenon that is not accompanied by changes in the circulation of the blood.…”

Typical sleep positions in pregnant women

“…In particular, during the supine position the gravid uterus compresses the inferior vena cava resulting in restriction of venous return 1 , reduced ejection fraction, reduced cardiac output, and consequently impaired uterine perfusion. 2 Failure to prevent this compression can lead to maternal supine hypotensive syndrome (also known as inferior vena cava compression syndrome) 3–5 and ultimately to an adverse effect on gas exchange between mother and fetus with consequent fetal heart rate decelerations. 6 Since the 1950's it has been standard of care to place laboring pregnant women in the left lateral tilt position to displace the uterus from the inferior vena cava and thus improve maternal hemodynamics and gas exchange.…”

Methods and considerations concerning cardiac output measurement in pregnant women: recommendations of the International Working Group on Maternal Hemodynamics

“…Third-trimester Doppler studies in normal pregnant subjects showed no difference between CO measurements obtained in the lateral and those obtained in the supine position near term 31,32 . However, cardiovascular magnetic resonance (CMR) imaging showed a significant increment in left ventricle ejection fraction, SV and CO in the left lateral position in third-trimester pregnant subjects 33,34 . Therefore, it is strongly recommended that CO-related assessments are performed in the left lateral position from as early as 20 weeks' gestation.…”

“…CMR imaging has been evaluated in comparison with transthoracic echocardiography (TTE) in 34 pregnant women, and was shown to have higher reproducibility and smaller intra-and interobserver variability than TTE 80 . As with other methods, it is essential to position pregnant women in a left lateral position from as early as 20 weeks' gestation, as CMR studies have shown clearly the effect of caval compression by the pregnant uterus on CO 33,34 . A retrospective study by Romagano et al 81 showed that CMR findings, in addition to the findings by TTE, can alter the clinical management of pregnant women with complex cardiac disease or suspected aortic pathology.…”