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.