DISCUSSION
This case report characterizes the morphology of a DAA diagnosed during fetal life and complicated by a non-obstructive thrombus. Clinical and echocardiographic follow-up demonstrated a total resolution with an excellent outcome.
Echocardiography is the standard imaging modality used to demonstrate DAA anatomy. In fetal life, the three-vessel view is useful to recognize this entity (8). Typically, a dilated vascular structure is identified protruding leftward of the aortic arch. Color flow Doppler, power Doppler, and pulsed-wave Doppler will help to confirm the diagnosis, to notice the presence of turbulence and to rule out the existence of thrombosis. 3-D and 4-D STIC ultrasound can be useful to verify the entire aneurysm and the ductus shape and contour. (Figure 1B)
Usually, isolated DAA is related to a good fetal and neonatal outcome. However, in some cases, severe complications may be associated with this anomaly (2-7). Thrombosis is one of the potential problems that has been reported in the literature (9,10). It seems to be related to turbulent flow or endothelial injury in the narrowed segment of the ductus (6, 11). The formation of a thrombus at that level with obstruction of fetal circulation can lead to hemodynamic decompensation with hydrops and death (2). In infants, the major complications are mass effect with compression of adjacent structures and thromboembolism with fatal consequences (5-7).
Management of fetuses and neonates with DAA thrombosis is controversial and there is no clear consensus regarding surgical treatment. The indications for anticoagulation and antiplatelet therapy remain unclear (12, 13). Otherwise, the majority of DAA regress spontaneously without ever been diagnosed, some by thrombus and others by constriction and reduction in size (14). Thus, some authors state that obliteration is preceded by thrombus formation, in contrast to other authors who have shown that thrombosis is not necessary for the DA closure in most of the cases (11, 15).
The identification of a small thrombus within the aneurysm during fetal life is challenging. Even though a big clot could be detected as an intravascular echogenic structure, color Doppler and pulsed-wave Doppler are essential to suspect a small thrombus. The diagnosis is based on the detection of incomplete filling of the vascular lumen by color Doppler. In addition, a restrictive pattern of the ductus could be found by pulsed-wave Doppler.
In our case, the transthoracic echocardiogram after birth evidenced a non-obstructive thrombus inside the ductal aneurysm (Figure 2). We speculate that the thrombus formation could be initiated antenatally. Fetal echocardiogram at 37 weeks showed complete filling of the aneurysm, no signs of restrictive ductal flow and stable duct dimensions compared to previous exams (Figure 1C). Unfortunately, the patient did not attend the planned follow up during the last weeks of pregnancy and the possibility of thrombi formation over the last weeks cannot be confirmed. However, thrombi formation could well explain the presence of significant right ventricle hypertrophy at birth secondary to the blood flow obstruction across the arterial duct. Serial echocardiograms after birth demonstrated the quick constriction of the ductus that led to a spontaneous regression without complications. Follow-up echocardiogram at 3 months of life showed a normalization of the right ventricle.
Considering that serious complications have been described after a late diagnosis because of the progression of the anomaly (7), we think that is important to assure a continued echocardiographic follow-up in patients with DAA.
In conclusion, ultrasound plays a key role in the diagnosis and management of DAA. Recognition of this anomaly and surveillance of thrombus development in pregnancy and neonatal period is important to avoid complications. Thus, serial echocardiographic examinations to control the aneurysm size, as well as the blood flow pattern in the ductus arteriosus aneurysm, are critical in follow up.