Cardiovascular evaluation of hypertensive disorders of pregnancy by echocardiography.
Desai, Dushyant K.
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Background: Preliminary observations suggest that aberrations in maternal central hemodynamics and uterine artery Doppler velocimetry reflect the severity of hypertensive disorders of pregnancy. In addition, the precise changes of cardiac output in normal pregnancy, particularly in the third trimester, have remained controversial. Aims and Objective: To measure concomitantly Doppler echocardiographic maternal central hemodynamics and uterine artery Doppler velocimetry and evaluate their association with adverse feto-neonatal outcome in hypertensive pregnant women. To evaluate cardiac output longitudinally in the latter half of pregnancy in normal healthy women. Design and Setting: Prospective study conducted at the Obstetric Unit, King Edward VIII Hospital, Durban, South Africa. Study sample: forty (40) pregnant hypertensives without any prior therapy and a further group of pre-eclamptic women (n=22) treated with stat dose sodium gardinal and alpha-methyldopa were studied. Results: i) A trend to a higher cardiac output was seen in the hypertensives compared to the normotensives. Hypertensive women were of larger stature; there was no difference in cardiac index. Fetal birthweight correlated poorly with cardiac index in pre-eclamptic women (r =0.21). A better correlation was seen with uterine artery resistance index (r = - 0.65) and systemic vascular resistance index (r = -0.49). Critical values for cardiac index and systemic vascular resistance index to predict poor adverse feto-neonatal outcome with good predictive values were not identified. ii) Pre-eclamptics treated with stat dose of sodium gardinal and/or methyldopa prior to echocardiography had a significantly lower systemic vascular resistance index and uterine artery resistance index compared to the untreated group. The lower systemic vascular resistance index in this treated cohort occurred from a combination of non-significant lower blood pressure and higher cardiac index. iii) Compared to normotensive women, untreated pre-eclamptics had a significantly lower heart rate (p< 0.001), a higher stroke index (p=0.018) and no difference in resultant cardiac index (p=0.452). iv) In gestational apoteinuric hypertensives presenting after 34 weeks gestation, maternal hemodynamics and uterine artery resistance index did not help define a higher risk group. v) In chronic hypertensives pregnancies, left ventricular hypertrophy correlated with severity of blood pressure. Higher risk chronic hypertensives were better selected by proteinuria than maternal central hemodynamics or uterine artery resistance index. vi) In normal pregnancy, maternal cardiac output peaked in early to mid third trimester and was maintained till term. Significant correlations were observed among maternal cardiac output, maternal body surface area and fetal birth weight. Discussion: i) This study shows that cardiac index and systemic vascular resistance index measured in the latter part of the second and third trimesters in hypertensive pregnant women were not associated with adverse fetal outcome. Large variations in cardiac index values were observed that restricted detection of satisfactory critical values for cardiac index and systemic vascular resistance index to predict adverse outcome. ii) An improved correlation of uterine artery resistance index with maternal hemodynamics and fetal birthweight in pre-eclampsia supports the hypothesis that poor placentation does not allow for a normal increase in uterine blood flow. iii) The poor correlation between uterine artery resistance index and maternal central hemodynamics, does not support the hypothesis that elevated cardiac output in hypertensive pregnancies (hyperdynamic disease model) occurs as a compensatory response to maintain adequate perfusion in a utero-placental bed with high resistance that did not decrease.