Early and late preeclampsia are characterized by high cardiac output, but in the presence of fetal growth restriction, cardiac output is low: insights from a prospective study

Abstract

Background: Preeclampsia and fetal growth restriction are considered to be placentally mediated disorders. The clinical manifestations are widely held to relate to gestation age at onset with early- and late-onset preeclampsia considered to be phenotypically distinct. Recent studies have reported conflicting findings in relation to cardiovascular function, and in particular cardiac output, in preeclampsia and fetal growth restriction.

Objective: We conducted this study to examine the possible relation between cardiac output and peripheral vascular resistance in preeclampsia and fetal growth restriction.

Study design: We investigated maternal cardiovascular function in relation to clinical subtype in 45 pathological pregnancies (14 preeclampsia only, 16 fetal growth restriction only, 15 preeclampsia and fetal growth restriction) and compared these with 107 healthy person observations. Cardiac output was the primary outcome measure and was assessed using an inert gas-rebreathing method (Innocor), from which peripheral vascular resistance was derived; arterial function was assessed by Vicorder, a cuff-based oscillometric device. Cardiovascular parameters were normalized for gestational age in relation to healthy pregnancies using Z scores, thus allowing for comparison across the gestational range of 24-40 weeks.

Results: Compared with healthy control pregnancies, women with preeclampsia had higher cardiac output Z scores (1.87 ± 1.35; P = .0001) and lower peripheral vascular resistance Z scores (-0.76 ± 0.89; P = .025); those with fetal growth restriction had higher peripheral vascular resistance Z scores (0.57 ± 1.18; P = .04) and those with both preeclampsia and fetal growth restriction had lower cardiac output Z scores (-0.80 ± 1.3 P = .007) and higher peripheral vascular resistance Z scores (2.16 ± 1.96; P = .0001). These changes were not related to gestational age of onset. All those affected by preeclampsia and/or fetal growth restriction had abnormally raised augmentation index and pulse wave velocity. Furthermore, in preeclampsia, low cardiac output was associated with low birthweight and high cardiac output with high birthweight (r = 0.42, P = .03).

Conclusion: Preeclampsia is associated with high cardiac output, but if preeclampsia presents with fetal growth restriction, the opposite is true; both conditions are nevertheless defined by hypertension. Fetal growth restriction without preeclampsia is associated with high peripheral vascular resistance. Although early and late gestation preeclampsias are considered to be different diseases, we show that the hemodynamic characteristics of preeclampsia were unrelated to gestational age at onset but were strongly associated with the presence or absence of fetal growth restriction. Fetal growth restriction more commonly coexists with preeclampsia at early gestation, thus explaining the conflicting results of previous studies. Furthermore, antihypertensive agents act by reducing cardiac output or peripheral vascular resistance and are administered without reference to cardiovascular function in preeclampsia. The underlying pathology (preeclampsia, fetal growth restriction, preeclampsia and fetal growth restriction) defines cardiovascular phenotype, providing a rational basis for choice of therapy in which high or low cardiac output or peripheral vascular resistance is the predominant feature.

Keywords: arterial function; cardiac output; hypertension; pregnancy; vascular resistance.