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.