DISCUSSION
Our study shows that fetal echocardiography can accurately identify the
origin of pulmonary vascular supply. Accuracy in defining the anatomy of
the pulmonary vasculature and the source of pulmonary blood supply was
82.3% and 88.2%, respectively. Previously published studies report
lower rates5,6. Zhoi J et al. and Naimi I et al.
reported similar rates with us in recent studies7,8.
The improvement seems to be related to the advanced ultrasound
technology. Besides, we have been intensely searching for MAPCAs and the
origin of pulmonary blood supply since the beginning of the study
period. We have no false negative MAPCA-dependent PAVSDs in our study.
Therefore, we suggest that cases with MAPCAs can be diagnosed with 100%
sensitivity with a meticulous search, including sagittal and coronary
planes of the aortic arch and descendent aorta. MAPCAs mostly originate
from the descending aorta (Figure 4b,4c, Figure 5c). They can also arise
from the aortic arch (Figure 4a, Figure 5a), subclavian arteries,
brachiocephalic trunk, internal mammarian artery, and left coronary
artery9.
We detected MAPCA originating from the coronary artery in one of the
cases (Figure 3a). MPA and the confluence of central PAs were absent on
fetal echocardiography. Postnatal angiography (Figure 3c,3d) and surgery
(Figure 3e,3f) confirmed the prenatal diagnosis. According to the
intraoperative assessment, MPA was absent. The LPA originated from
patent DA. The RPA was supplied by a collateral from the left main
coronary artery (LMCA) (Figure 3e,3f). There was no confluence of PAs.
Coronary to pulmonary collaterals are rare and can be detected in
1.3%-10% of the cases with PAVSD10,11. To our
knowledge, this was the first case in the literature diagnosed
prenatally and confirmed surgically. It was expected that cardiac
ischemia could have occurred due to increased coronary to pulmonary
steal secondary to decreased pulmonary vascular resistance after birth.
Thanks to the prenatal diagnosis, the newborn was immediately referred
to the collaborated cardiovascular clinic on prostaglandin infusion and
underwent early surgery to avoid coronary stealing. Therefore, we
suggest that the aortic root should also be carefully searched in axial
and longitudinal planes in PAVSD cases to detect any collaterals arising
from coronary arteries. These newborns may not present cyanosis due to
the high flow from coronary arteries to the lungs; however, they may
develop acute cardiac failure based on cardiac ischemia.
The impact of MAPCAs on perinatal and postnatal outcomes is debatable in
the literature3,7. MAPCA-dependent newborns can
present cyanosis in case of narrow collaterals, or those with adequate
collaterals may be acyanotic with subtle symptoms for months until
stenosis of the collaterals occurs. Multiple, dilated collaterals may
lead to pulmonary hypertension, congestive heart failure, or pulmonary
parenchymal bleeding. MAPCA-dependent cases usually have non-confluent
PAs with arborization abnormalities or no central PAs at all, while
DA-supplied cases usually have confluent PAs with complete
intrapulmonary arborization8. Consistently, in our
study, except the one with DA arising from the 1stbranch of the aortic arch (Figure 6a, 6b), all DA-dependent cases had
unifocal, confluent PAs. On the other hand, only 28.5 % of the MAPCA
group had confluent PAs. The presence or absence of confluent PAs
transforms the method of surgery. Non-confluent PAs have narrow RPA,
LPA, and larger MAPCAs which may lead to pulmonary parenchymal disease
secondary to incomplete intrapulmonary arborization7.
Therefore, assessment of the confluence of PAs and the size and anatomy
of PAs on fetal echocardiography is as necessary as identifying the
origin of pulmonary blood supply for proper prenatal counseling.
Considering the smaller PAs and impaired PA arborization, worse outcomes
could have been expected in the MAPCA group compared with the DA group.
However, we found that the existence of MAPCAs did not significantly
impact postnatal survival. This may be related to the relatively higher
accompanying anomalies in the DA group in our study. Moreover,
DA-dependent cases needed surgical intervention to prevent desaturation
secondary to the stenosis of DA within the first two weeks of life. In
contrast, MAPCAs were operated on in later weeks as the stenosis
occurred later.
The overall survival was too low compared with the other studies in the
literature3,7. Survival was highly disrupted by
extracardiac anomalies, particularly in the DA group. Among the babies
who survived until the operation, postoperative survival rates for MAPCA
and DA groups were 60% and 66.6%, respectively. These rates are also
lower than the other studies3,9. Both postoperative
deaths were related to extracardiac anomalies in the DA group.
Therefore, while counseling the parents, it should be emphasized that
extracardiac malformations may prohibit surgery or lead to postoperative
mortality. Postnatal surgical series report rather promising
outcomes12,13. However, many newborns like the ones in
our study do not survive until the operation.
One of the weaknesses of our study is the small sample size. We
restricted the study period to the last five years as we have had a
dedicated fetal echocardiography clinic since 2017. Another consequence
of this short study period is that we could not compare the long-term
prognosis between the groups. The strength of the study is that it was
conducted in a single center, and the fetal echocardiographies were
performed by the same operator. All of the angiographies and the
majority of the surgeries were performed by the associate cardiovascular
surgery clinic.