Discussion
In our study, we aimed to investigate whether or not the inflammatory
process associated with maternal asthma affects fetal cardiac functions.
Fetal cardiac function measurements from pregnant women with asthma in
the asymptomatic period of the disease and with uncomplicated
pregnancies were compared with those from healthy pregnancies. Fetal
right and left ventricular functions were studied using different
ultrasound techniques such as pulse wave Doppler, spectral TDI, and
M-mode. Using the pulse wave Doppler technique, we found that the
tricuspid E wave velocity and tricuspid E/A ratio were lower in the
fetuses of mothers with asthma compared with the control group. This
finding showed us that an early diastolic change began in the fetuses of
pregnant women with asthma. While MPI and LCO parameters, which are
indicators of global cardiac function, did not change, it was observed
that the left ventricular IVRT value, which is one of the MPI
parameters, was prolonged in the asthma group, which is another marker
of diastolic change in the heart. In the study performed with the M-mode
technique, we found significantly lower MAPSE and TAPSE values in
fetuses of pregnant women with asthma. A significant difference was
found between an asthma diagnosis duration of 12 years or more and a
duration of less than 12 years in both atrioventricular valves E and A
wave velocities. We found that the duration of maternal asthma was
negatively correlated with the tricuspid A wave velocity and positively
correlated with the mitral E wave velocity and A wave velocity.
In adult cardiac dysfunction cases, diastolic functions are affected in
the early phase and systolic functions in the later phase. The E/A ratio
reflects the ventricular inflow pattern, and this ratio is used to
assess diastolic function or ventricular relaxation. Parameters such as
annular displacement or velocities, which indicate longitudinal
function, are typically impaired in the very early stages of fetal
cardiac dysfunction compared with radial function parameters such as
ejection fraction and cardiac output. Similarly, diastolic parameters
such as IVRT are the first to be altered to reflect impaired relaxation15. The E/A ratio partly reflects cardiac preload,
whereas the outflow tract reflects cardiac afterload and is often
considered together. MPI is an early and reliable marker that indicates
global myocardial function 16 and provides data on
different periods during the systolic phase of the cardiac cycle. IVRT
is the most important parameter of MPI affected in complicated
pregnancies. In general, impaired ventricular dysfunction is associated
with higher MPI values, which is due to the prolongation of IVRT.
Increased IVRT is associated with decreased ET. IVCT is the most stable
parameter of MPI 10. Reduced E/A ratios and increased
MPI values in IUGR fetuses have been demonstrated in the literature17-19. Interestingly, some studies found higher left
ventricular MPI values and higher E/A ratios in fetuses with PPROM with
microbial invasion of the amniotic cavity and with signs of fetal
inflammatory response syndrome 20, 21. In another
study investigating fetal heart functions in maternal familial
Mediterranean fever (FMF) associated with chronic inflammation, it was
found that fetal diastolic functions might be altered in fetuses of
mothers with FMF. As the duration of maternal FMF increases, systolic
functions may also change 14. In our study, we found
that MPI and LCO parameters did not change, but E wave and E/A ratio
values were lower in the asthma group. We also found a prolongation of
IVRT in the asthma group.
TDI is a method of estimating early preclinical cardiac dysfunction by
measuring the velocity of myocardial movement. Comas et al. suggested
that TDI may be a more sensitive method than conventional
echocardiographic techniques for assessing fetal cardiac dysfunction11. TDI also allows measurement of MPI similar to
pulsed Doppler. The E/E’ ratio, the ratio of early tricuspid annular
velocity (E’) to early peak filling velocity of the tricuspid valve (E),
is one of the echocardiographic parameters of diastolic function in the
prenatal period 7. Some studies have investigated
fetal cardiac functional changes in fetuses with IUGR using the s-TDI
technique 18, 22. Our study did not find any
difference between the groups in the parameters examined by the TDI
method.
The M-mode method can be used to assess the longitudinal motion of the
heart. This approach is best suited for the examination of the right
ventricle. Longitudinal cardiac function, which is driven by
longitudinal myocardial fibers, is considered the first function to be
affected in the presence of hypoxia. In a study, it was found that all
annular parameters indicative of subclinical cardiac dysfunction
decreased significantly in the IUGR group. In this study, it was found
that M-mode examination showed the same performance as a classifier
compared with TDI examination, especially in the tricuspid annulus23. In our study, we found that MAPSE and TAPSE levels
were decreased in the maternal asthma group compared with the control
group. However, asthma duration did not affect MAPSE and TAPSE scores.