Maternal Cardiovascular Hemodynamics in Normal and Preeclamptic Pregnancies Using Echocardiography

Background: Preeclampsia is associated with higher prevalence of abnormal global left ventricular function. So, present study was designed to compare these changes in normal and preeclamptic pregnancies using echocardiography. Methods: In present study, 25 patients with pre-eclampsia with singleton pregnancy between 20-30 years (study group) were compared with 25 age matched healthy pregnant women (control group). They were non-invasively analyzed for cardiovascular hemodynamics using echocardiography. The data was analyzed using student’s ttest. P value <0.05 was considered to be significant. Results: Mean stroke volume in pre-eclampsia group was 72.4±5.1 ml v/s 67.7±5.6 ml in control group and the difference was statistically significant. Mean Cardiac output in preeclampsia group was64.2±3.4 lit/min v/s 5.69±0.47 lit/min in control group which is statistically significant. Mean Systemic vascular resistance (dyne.sec cm-5) in pre-eclampsia group was 1468.22±5.7 v/s 957.7±131 in control group which is statistically significant. Mean Ejection fraction (%) in pre-eclampsia group was 68.31±5.1 v/s 66.54±4.7 in control group which is statistically significant. Conclusions: Doppler echocardiography provides an excellent non-invasive method for evaluation of hemodynamic changes during pregnancy. Therefore if it is introduced into antenatal protocol, could help to identify subset of pre-eclamptic women who are at high risk to developing complications and thereby can do early intervention.


Introduction
Pregnancy is a physiological phenomenon. It produces both anatomical and physiological changes in all the organs including reproductive organs, cardiovascular system, hemopoietic system, respiratory system and excretory system etc. It is associated with volume overload producing significant vascular and hemodynamic adaptations in cardiovascular physiology [1].They are necessary for successful pregnancy, but they impose further load on the heart. Preeclampsia is a multisystem disorder that occurs after 20 wks of pregnancy. Acute preeclampsia is associated with significantly higher prevalence of asymptomatic abnormal global left ventricular (LV) abnormal function/geometry and myocardial injury [2]. It is also associated with significantly higher risk of subsequent heart failure, ischemic and hypertensive heart diseases and related mortality in later life [3,4]. Many studies of women with preeclampsia have revealed diverse hemodynamic findings such as elevated cardiac output (CO), high vascular resistance, and reduced CO and myocardial contractility [5]. Impairment of LV diastolic function as well as systolic function appear very early in the course of heart disease [6]. Early detection and its treatment at an asymptomatic phase can help in improving the prognosis. In earlier days, gas exchange techniques were used to determine cardiac output. With development of cardiac catheterization, it was used to study right heart hemodynamics. The advent of echocardiography enabled serial noninvasive cardiovascular monitoring throughout pregnancy. Initially, investigators used M-mode but perhaps due to its limitations, results were not uniform [7]. Recently, Doppler echocardiography has been used which is reproducible and noninvasive technique suitable for pregnant Women [8].
Therefore echocardiography if introduced into the routine antenatal protocol, could help to identify women who are at high risk to develop cardiovascular complications and there by early intervention.
Nalgonda District, Telangana. It was prospective case controlled study conducted in 50 subjects during September 2015 to August 2016 over a period of 12months. In present study, 25 patients with pre-eclampsia with singleton pregnancy between 20-30 years (study group) were compared with 25age matched healthy pregnant women (control group). Patients who refused to participate; those suffering from cardiovascular disease, diabetes mellitus, thyroid disorder, anaemia and multiple gestations were excluded. All subjects were informed in detail about aim and procedure of study; and written consent was taken for conduct of study.
A detailed obstetric history and thorough examination was done in all subjects. Age, Height, Weight were noted. Blood pressure was measured by sphygmomanometer in right arm in left lateral position after 10minutes of rest by auscultator method. Onset of tapping sound was taken as systolic and muffling of Korotkoff sound was taken as diastolic blood pressure. An obstetric ultrasound scan was performed to confirm singleton pregnancy and gestational age. All subjects were subjected to echocardiography using Philips ANVISER-C model. Standard parasternal two dimensional long axis images were recorded and left ventricular diameters were measured in M mode (American Society of Echocardiography guidelines) [9]. Doppler Echocardiography was used to calculate stroke volume [10]. Simultaneously heart rate per minute was recorded. Cardiac output, Systemic vascular resistance and ejection fraction were calculated.

Statistical Analysis
The data was expressed as Mean±S.D and was analyzed using student's t-test P-value <0.05 was considered to be significant. Mean weight was more in study group which was statistically significant.

Discussion
Pregnancy is a condition of primary peripheral arterial vasodilatation, associated with hyperdynamic circulation with high CO and low SVR [11]. Preeclampsia is a disease unique to pregnancy that contributes substantially to maternal and fetal morbidity and mortality, and is associated with increased vascular resistance and hypertension [12]. Hypertension produces structural changes in the left ventricle usually accompanied by functional alterations and in majority of cases; these alterations precede clinical manifestations [13]. In normal pregnancy, an increased preload and a decreased after load favor an improved emptying of the left ventricle during systole and a reduction of the end-systolic pressure [14]. In preeclamptic women, the elevated after load is linked with a reduced emptying of the left ventricle and elevated end-systolic pressure. Rizwana Solanki et al found a statistically significant difference in mean SV between pre eclamptics and normotensive women groups' studied [5].
Results of present study were also comparable to study done by Dennis et al. [15]. They observed cardiac output was higher in PIH group as compared to the controls . They stated that cardiac output is increased in women with untreated pre eclampsia due to an increase in stroke volume. Solanki et al. [4]. Found cardiac output was significantly higher in pre eclamptic patients5 our results were comparable to their. In present study, systemic vascular resistance was more in pre eclimptic patients .This is in accordance with study of Solanki et al. [5].

Conclusion
Doppler echocardiography provides an excellent non-invasive method for the evaluation and serial analysis of hemodynamic changes during pregnancy. They help in distinguishing abnormal changes from maternal physiologic changes. Preeclampsia still contributes to a majority of maternal mortality and morbidity. Therefore echocardiography if introduced into the antenatal protocol, could help to identify subset of preeclamptic women who are at high risk to develop cardiovascular complications and thereby can do early intervention.

Limitation
It was performed in a single hospital therefore sample may not be representative of all Indian women. Therefore we recommend a cross-sectional multicentric study to confirm results.

Future
Further studies can be made by 3D echocardiography which is based on direct volumetric quantification, which is independent of geometric assumption of Left Ventricle