Keywords
TEI Index - intrahepatic cholestasis of pregnancy - bile acids - ursodeoxycholic acid
- transaminitis
Intrahepatic cholestasis of pregnancy (ICP) is the most common disease of the liver
during pregnancy and is characterized by predominantly nocturnal itching on the palms
of the hands and soles of the feet, the onset is typically during the third trimester
of pregnancy. The prevalence varies between 1 and 5%, depending on the geographic
area, Chile has one of the highest prevalences of ICP. Has associated, depending on
severity, 1 to 4% of unexplained fetal deaths. This is why multiple hypotheses have
been investigated, the most recent of which suggests that there is a change in the
fetal cardiac rhythm or function.
In recent years, the impact of bile acids on the fetal heart has received particular
attention. This is primarily due to evidence showing alterations in myocardial conductivity.
Studies in both animal models and recent human research have demonstrated that bile
acids can modify myocardial functionality.
As early as 1987, Binah et al[1] demonstrated in their study that an increase in bile acid levels decreases the duration
of the action potential in rat cardiomyocytes. This study also established that the
effects of bile acids on cardiac function can be direct or indirect. The direct effects
include alteration of calcium channels, reduction of intracellular adenosine monophosphate
(cAMP), and increased apoptosis through the interaction of bile acids with muscarinic
receptors. Indirect effects are related to bile acids and cholesterol metabolism,
regulation of blood cholesterol levels, atherosclerotic plaque formation, and myocardial
function. Years later, around 2002, another study conducted by Gorelik and colleagues[2] in experimental rat models demonstrated that elevated levels of bile acids were
associated with a decrease in contraction amplitude, a reduction in cardiomyocyte
synchronization, and a shorter action potential duration. In 2009, Zhang et al[3] studied the correlation between bile acid levels and cardiac dysfunction in neonates.
They found that left ventricular TEI index and cardiac troponins were significantly
higher in female infants with cholestasis compared to those of the control group.
Subsequent studies, which will be discussed in more detail later, have concluded that
there are structural and functional changes present in the myocardium of fetuses from
pregnant women affected by the condition when compared with fetuses of healthy pregnant
women.
Our study had three objectives: First, to explore the difference in fetal cardiac
function in patients with and without ICP by comparing TEI index; second, to explore
a potential correlation between TEI index and bile acid levels in pregnant women with
ICP; and finally, to study changes in TEI index in fetuses of pregnant women with
ICP after administration of UDCA.
Materials and Methods
Study Design and Ethics Committee Approval
This was a prospective observational case-control study conducted in Hospital Clínico
San José, and Clínica RedSalud Vitacura, both in Santiago, Chile, between April 2018
and October 2020.
The study was approved by the “Comité de ética de la Investigación del Servicio de
Salud Metropolitano Norte” on July 19, 2018 (Carta No 052/2018). Written consent was
obtained from all participating women.
Study Population
The study population included pregnant women attending the aforementioned hospitals.
Inclusion criteria were mothers aged 18 years or older, cases diagnosed with ICP during
pregnancy, and controls without ICP symptoms. For these cases, ICP was defined as
palmoplantar itching lasting more than a week, mainly at night, and was associated
with total bile acid levels greater than 10 μmol/L.[4] Control cases were pregnant women scheduled for induction of labor or elective cesarean
delivery between 38 and 40 weeks of gestation according to the current protocol. Exclusion
criteria were twin or multiple pregnancies, fetal malformation, fetal growth restriction,
maternal viral infection altering maternal liver function, drug therapy affecting
maternal liver function or fetal heart function, fetal structural heart abnormality
or arrhythmia, and the presence of anti-Ro or anti-La antibodies.
Clinical Protocol
-
Informed consent
During the informed consent process, all pregnant women participating in the study,
whether in the ICP group or the control group, received written information on the
pathology and the diagnostic methods used.
-
Bile Acid Measurements
In the ICP group, bile acid measurements were performed when patients were clinically
diagnosed with ICP. In severe forms of the disease, this measurement was taken weekly
until the end of pregnancy, and in mild form every 2 weeks. Severity criteria were
set for this purpose as TBA > 40 µmol/L and/or total bilirubin > 1.8 md/dL and/or
transaminases greater than twice the upper cut-off value established by the clinical
laboratory.
In the control group, bile acid measurements were performed at preoperative examination
or on admission.
-
Measurement of TEI index
Fetal functional echocardiography was performed at diagnosis and repeated weekly in
the severe cholestasis group, at 34 to 36 weeks of gestation in the mild cholestasis
group, and at the time of preoperative test or hospital admission in the control group.
The TEI Index was obtained from the Left Ventricular outflow tract plane. In this
projection, the mitral and aortic valves can be visualized simultaneously, thus, the
isovolumic contraction time, isovolumic relaxation time, and ejection time (ET) can
be measured in the same cardiac cycle. This avoids the inaccuracies resulting from
measuring time intervals in different cardiac cycles. To do this, the pulsed Doppler
sample is placed in the LV at the junction of the anterior leaflet of the mitral valve
and the LV outflow tract.
TEI index was measured as follows: from the end of the A-wave to the onset of the
aortic pulsed Doppler tracing (ICT), from the onset to the end of the aortic pulsed
Doppler tracing (ET), and from the end of the ET to the onset of the E-wave. A single-blinded
operator assessed the fetal hearts in the absence of fetal and/or breathing movements.
The TEI Index was calculated from an average of the three successive measurements
of each of the intervals measured including fetal heart rate.[5]
-
Use and control of ursodeoxycholic acid (UDCA)
UDCA at 15 mg/kg/day divided into 3 to 4 doses was given to all patients diagnosed
with ICP. Dosing began after samples were collected for bile acid measurements and
fetal echocardiography was performed. Fetal echocardiography was performed again before
delivery in this group.
-
Monitoring and end of gestation
In addition, in the mild ICP group, weekly monitoring with cardiotocography (CTG)
and liver tests was planned according to the current protocol. In the severe cholestasis
group, patients were hospitalized, differential diagnosis was performed, CTG and liver
tests were monitored every 48 hours, and bile acids and PR intervals were measured
weekly (as previously described). According to the national protocol, pregnancy was
terminated at 36 weeks in cases of severe ICP and at 38 weeks in cases of mild ICP.
Study Size
The sample size necessary to achieve our primary outcome (difference in TEI interval)
was calculated, and the results of the Henry and Welsh study were taken into consideration,
in which the difference in the TEI index between the high bile acid group and the
low bile acid group was 0.04 ms. Accepting an α risk of 0.05 and a β risk of 0.2 in
a bilateral contrast test, 45 subjects in the first group and 45 subjects in the second
group were required to detect a difference equal to or greater than 0.04 units. The
common standard deviation was assumed to be 0.06. A loss to follow-up rate of 20%
was estimated.
Outcomes
The main outcome is the TEI index, defined as (isovolumetric contraction time [ICT] + isovolumetric
relaxation time [IRT])/ET ([Fig. 1]).[6]
Fig. 1 Measurement of TEI index at the mitral-aortic valves, in a 5-chamber view.
Bile acids were measured from maternal plasma and reported in μmol/L.
Statistical Analysis
First, maternal demographic data were analyzed. The distribution of continuous data
was tested by the Shapiro test. Normally distributed data were reported as the mean
and standard deviation (SD), and nonparametric data were reported as the median and
interquartile range (IQR). Categorical data were reported as absolute and relative
frequencies (percentages).
Second, demographic, cardiac, and delivery data were compared between cases and controls.
Continuous data were compared using the independent samples t-test or the Wilcoxon test, depending on whether the distribution was normal or not.
Categorical data were compared using the chi-squared test or Fisher's exact test,
as appropriate.
The correlation between the TEI index and bile acid levels was investigated using
the Spearman correlation test.
Changes in TEI index before and after administration of UDCA were analyzed using the
paired samples Wilcoxon test.
Gestational age as a confounder. Gestational age at the time of measurement of the
TEI index was examined as a confounding variable. Multiple regression analysis was
planned to adjust for the effect of gestational age.
Results
A total of 182 women were included in the study: 110 cases and 72 controls. One hundred
and sixty-four (90.1%) women were recruited in Hospital San José, and 18 (9.9%) in
Clínica RedSalud Vitacura. All controls were recruited in Hospital San José. The TEI
index could not be assessed in one of the fetuses and was excluded. One hundred and
eighty-one women were included in the analysis, 109 cases and 72 controls. Bile acid
levels were measured in all 181 patients.
Maternal Demographic Data
The median maternal age was 28 years old (IQR, 23–34). Median body mass index (BMI)
was 28 kg/m2 (IQR, 24–31). Regarding nationality, 169 (93.4%) women were Chilean, 8 (4.4%) women
were Peruvian, 2 (1.1%) women were Bolivian, and 2 (1.1%) women were Venezuelan. Median
gestational age at inclusion was 35.9 weeks (IQR, 33.0–38.9). The demographic characteristics
of cases and controls are summarized in [Table 1].
Table 1
Maternal demographic characteristics in intrahepatic cholestasis of pregnancy and
controls
|
Intrahepatic cholestasis of pregnancy (n = 109)
|
Controls (n = 72)
|
p-Value
|
|
Maternal age (y)
|
28.0 (23–34)
|
28.5 (23–38)
|
0.197
|
|
Body mass index (kg/m2)
|
28 (25–31)
|
27 (23–31)
|
0.412
|
|
Nationality
|
|
Chile
|
102 (93.6%)
|
67 (93.1%)
|
0.313
|
|
Bolivia
|
2 (1.8%)
|
0
|
|
Peru
|
5 (4.6%)
|
3 (4.2%)
|
|
Venezuela
|
0
|
2 (2.8%)
|
|
Gestational age at inclusion (wk)
|
33.7 (31.5–35.6)
|
39.0 (38.6–39.4)
|
<0.001
|
Note: Continuous data are reported as the median and interquartile range. Categorical
data are reported as absolute values and percentages. Comparison between groups was
performed using the Wilcoxon test for continuous data and the Fisher's exact test
for categorical data.
Primary Outcome
The median TEI index was 0.31 (IQR, 0.29–0.36), and it was significantly larger in
fetuses of women with ICP (0.34, IQR, 0.30–0.38) as compared with controls (0.30,
IQR, 0.28–0.31; p < 0.001).
Secondary Outcome 1
In the ICP group, there was a significant correlation between bile acid levels and
TEI index (rho = 0.584, p < 0.001; [Fig. 2]).
Fig. 2 Correlation between fetal TEI index and maternal bile acid levels in women with intrahepaticc
holestasis of pregnancy.
Additionally, in the ICP group, there was a significant correlation between the TEI
index and aspartate aminotransferase (AST; rho = 0.236, p = 0.013) and between PR interval and alanine aminotransferase (ALT; rho = 0.195,
p = 0.042).
Secondary Outcome 2
In 21 fetuses, the TEI index was measured a second time, 2 weeks apart, following
UDCA administration. The median TEI index decreased significantly following UDCA administration
(0.40 ms before treatment (IQR, 0.36–0.42) vs. 0.33 after treatment (IQR, 0.32–0.38,
p = 0.001; [Fig. 3]).
Fig. 3 TEI index before and after treatment with ursodeoxycholic acid.
Delivery
In this study, the median gestational age at birth was 38 weeks (IQR, 37.1–38.9).
One hundred and twenty-four (68.5%) women underwent a vaginal delivery, and 57 (31.5%)
women had a cesarean section. Median birthweight was 3,029 g (IQR, 2,870–3,400). One
hundred and seven (59.1%) fetuses were male and 74 (40.9%) fetuses were female. Median
Apgar score at 1 minute was 9 (IQR, 8–9), and at 5 minutes was 9 (IQR, 9–9). Perinatal
outcomes in women with ICP and controls are compared in [Table 2]. Women with ICP delivered significantly earlier and had babies with a lower birth
weight.
Table 2
Obstetric outcome in women with intrahepatic cholestasis of pregnancy and controls
|
Intrahepatic cholestasis of pregnancy (n = 109)
|
Controls (n = 72)
|
p-Value
|
|
Gestational age at delivery
|
38.0 (37.1–38.9)
|
39.0 (38.6–39.4)
|
<0.001
|
|
Mode of delivery
|
|
Vaginal
|
76 (69.7%)
|
48 (33.3%)
|
0.787
|
|
Cesarean section
|
33 (30.3%)
|
24 (66.7%)
|
|
Birth weight
|
2,915 (2,703–3,090)
|
3,400 (3,076–3,577)
|
<0.001
|
|
Gender
|
|
Female
|
46 (42.2%)
|
28 (38.9%)
|
0.772
|
|
Male
|
63 (57.8%)
|
44 (61.1%)
|
|
Apgar at 1 min
|
9 (8–9)
|
9 (8–9)
|
0.897
|
|
Apgar at 5 min
|
9 (9–9)
|
9 (9–9)
|
0.893
|
Notes: Continuous data are reported as the median and interquartile range. Categorical
data are reported as absolute values and percentages. Comparison between groups was
performed using the Wilcoxon test for continuous data and the Fisher's exact test
for categorical data.
Discussion
Main Findings
In this study, we found that the TEI index is significantly greater in fetuses of
women with ICP as compared with controls. There was also a significant correlation
between the TEI index and bile acid levels. Moreover, the TEI index was shorter following
the UDCA administration in women with ICP.
Comparison with Previous Studies
A search for human fetus studies on cholestasis and the TEI index yielded limited
results. In the first study published in 2014, Fan et al[7] did a case-control study in humans to investigate eventual fetal myocardial deformation
in patients with cholestasis (40 with ICP, and 40 controls). In this study, a decrease
in left ventricular overload was demonstrated in direct correlation with the level
of bile acids. Fetal myocardial deformation is impaired in severe ICP. In our study,
we decided to use the TEI index as the most clinically reproducible in our local environment.
This index also showed a direct relationship with bile acid levels, as did myocardial
deformation. In 2016, Ataalla et al[8] published another study in humans showing that women with cholestasis and high levels
of bile acids (>40 mmol/L) present fetal cardiac dysfunction, using tissue Doppler
at the fetal myocardium level. In the same year, Henry et al[6] demonstrated that the fetuses of pregnant women with cholestasis present a significant
increase in ventricular isovolumetric contraction and relaxation times compared with
the control group. Comparing these two studies with our own findings, a clear correlation
has been established between fetal myocardial functionality and total bile acid levels.
In 2022, Rodriguez et al[9] demonstrated that fetuses affected by maternal ICP are associated with electrical
and diastolic myocardial dysfunction. Forty-nine patients were included in each group
and ICT, ET, and IRT for electrical, systolic, and diastolic function, respectively
were measured. IRT was significantly higher in ICP, with no differences in ICT and
ET. While it is true that the results are similar to those obtained in our study,
the work of Rodriguez does not consider the association with bile acid levels.
Finally, the PROSPERO study,[10] a meta-analysis aimed at correlating adverse perinatal outcomes with biochemical
markers, concluded that bile acid levels above 100 μmol/L correlate with adverse perinatal
outcomes. These elevated bile acid levels were not obtained in our sample group. However,
the PROSPERO study does not specify the causes of adverse perinatal outcomes, which
is one of the findings of our study.
Clinical Implications
Clinical implications are related mainly to the management of patients with ICP and
complement what was published by this same group last year about the evaluation of
the PR interval in these patients.[11]
On the one hand, we have observed that in the fetus, the TEI index is greater when
maternal bile acid levels are higher. Therefore, cases with high levels of bile acids
may be at a higher risk for adverse perinatal outcomes and should be monitored more
closely.
On the other hand, we have observed that treatment with UDCA reduces the TEI index
in the fetus, which may potentially imply a reduction in the risk of adverse perinatal
outcomes.
Strengths and Limitations
Strengths and Limitations
In our study, we did not observe bile acid levels above 100 μmol/L. Based on the latest
reviews, higher values of bile acid levels are associated with very poor outcomes.
Increasing sample size with multicenter studies and correlating the TEI index with
the different parameters mentioned in this study may help to identify a correlation
between TEI Index/myocardial function and poor obstetric outcomes.
Conclusion
Our study confirms that the TEI index is greater in fetuses of women with ICP. Even
more interestingly, the findings of our study show that the TEI index is significantly
correlated with bile acid levels. In addition, the administration of UDCA reduced
the TEI index significantly.
