Although fetal echocardiography has been used successfully for many years in the diagnosis of fetal congenital cardiovascular abnormalities, there is a need at times for additional information without limitation to the acoustic windows [2]. FCMR avoids exposure to ionizing radiation and no clinical or experimental evidence has indicated that CMR has any adverse effects on the human fetus [3].
The mean gestational age in our studied cases was 30.81 ± 4.30 ranged from 24 to 39 contrary to the results of the study of Tavares de Sousa et al. [6] who mentioned that the mean gestational age at MRI was 34 weeks (range 28 to 36 weeks). Zhu [5] stated that the mean gestational age in their study group was 27 weeks (range 17 to 39 weeks).
Zhu [5] found that 280 cases of CHD including ventricular septal defect (VSD), coarctation of aorta (CoA), interrupted aortic arch (IAA), double aortic arch, tetralogy of fallot (TOF), D type transposition of great arteries (D-TGA), L-TGA, pulmonary atresia (PA)/VSD, double outlet right ventricle (DORV), hypoplastic left ventricle syndrome (HLVS), tricuspid atresia (TA) and others, MRI provided additional important information to fetal echocardiography at 51(18%) cases while in our present study the 52 cases of CHD included VSD, atrial septal defect (ASD), right-sided dilatation, atrioventricular (AV) – ventriculoarterial (VA) discordance, right hypoplastic, HLVS, TGA, right side aortic arch (RAA), and others. MRI provided additional information at 32 cases (61%). Four chamber view still is the most important view. The fetal MR imaging of the transverse view of aortic arch just like the “three vessels view” in fetal echo also is very important [5].
In the present study, there was statistically significant agreement between FCMRI and fetal echo regarding VSD, right hypoplastic ventricle (RHV) & double inlet left ventricle (DILV), (ASD), apparent cardiomegaly, Pericardial effusion, right side dilatation & thick tricuspid valve (TV), AV&VA discordance, TGA & RAA and Ebstien anomaly that agrees with the study done by Tavares de Sousa et al. [6] who stated that There was full agreement (κ = 1) between fetal echocardiography and cardiac MRI in evaluating the cardiac situs, descending aorta, transverse cardiac diameter, foramen ovale, relationship between tricuspid and mitral valve planes and ventricular contraction patterns.
Gorincour et al. [7] added the assessment of ventricular looping by MRI as being possible in all fetuses as well which agreed with our study in a case of positional mesocardia, anterior chest wall defect causing ectopia cordis and small liver herniation with omphalocele Fig. 2. In particular, all the morpho-volumetric abnormalities of the heart and the cardiac chambers as well as the abnormalities of rotation were visualized by direct signs: cardiomegaly through the measurement of a cardio/thorax ratio (C/T ratio) over 1/3; hypoplastic left heart syndrome through the reduction in size of the left chambers; pericardial effusion through the detection of a high signal intensity fluid which agrees with 6 cases of our study.
In Manganaro et al. [8] as regards extra cardiac abnormalities, MRI detected a CNS pathology in 6 fetuses, a non-CNS pathology in 13 fetuses which agree with our study which detect extra cardiac anomalies in 15 fetuses (CNS in 4 fetuses, non-CNS in 11 fetuses) Fig. 3.
Saleem [9] study including 20 fetuses concluded that cardiac MRI can be used to determine the cardiac parameters outlined by Gorincour et al. [7], Manganaro et al. [8] which include visceroatrial situs, cardiac position, cardiac size, cardiac axis, cardiac chambers, ventricular looping, inflow veins, outflow vessels, ventriculoarterial concordance, side of the aortic arch and all cardiac anatomic components were classified into one of two categories: well visualized or poorly or non-visualized. In our study there was statistically fair agreement comparing post-natal gold standard echo & fetal echo and fetal MRI in diagnosis of right-side dilatation & TV thickening, right hypoplastic &DILV, AV&AV discordance and Ebstien anomaly.
Strength of our study, that there was statistically significant higher accuracy of diagnostic agreement with Fetal MRI (95.5%) compared to Fetal Echo (86.4%), with p value < 0.001 which agrees with the results of Dong et al. [3] study which found that Fetal MRI diagnostic accuracy rate was (79%) is significantly higher than the routine obstetric US (46%) in their study.
Finally, it should also be noted that the MRI studies provided several important complementary imaging that could directly or indirectly impact the cardiac prognosis, for example describing the devastating extent of pulmonary compression from a very large diaphragmatic hernia in a fetus that did not survive to term [10]. Fetal MRI can also be used to assess lung parenchymal lesions and airway compromise in CHD and demonstrate the presence of pulmonary lymphangiectasia in a fetus with hypoplastic left heart syndrome [11]. Limperopoulos et al. [12], Brossard-Racine et al. [13] studies agreed with our conclusion and stated that MRI of the fetal brain may provide crucial information to clinicians and parents regarding medium-term and long-term prognoses, which may have a profound effect on both prenatal and postnatal management independent of the underlying cardiac diagnosis. Our study is unique in describing extracardiac anomalies with follow up confirmation postnatally.