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Page 6 of 43 Rao. Vessel Plus 2022;6:26 https://dx.doi.org/10.20517/2574-1209.2021.93

Figure 7. Selected video frames from color flow mapping images in suprasternal notch views demonstrating collateral vessels marked
[5]
with arrows both in (A) and (B). Reproduced from Ref. . Ao: Aorta; DAo: descending aorta.
interrogation may illustrate where the large collateral vessels may arise, but where they empty into the PAs
is difficult to demonstrate. In addition, small-sized collateral vessels may be difficult to see. Most usually,
echocardiography by itself is not adequate to reveal important aspects of the anatomy of the PAs and how
the blood supply to all segments of the lungs is distributed in these cases of TOF with MAPCAs. Computed
tomography and/or selective cine-angiography are often necessary to demonstrate these abnormalities .
[5,6]

Type IV. TOF with syndrome of absent pulmonary valve
Syndrome of absent pulmonary valve is an uncommon heart defect and makes up 3% to 5% of all cases of
TOF. It comprises of: (1) rudimentary leaflets of the pulmonary valve, with consequent pulmonary
insufficiency; (2) pulmonary valve annular hypoplasia, producing PS; and (3) marked dilatation
(aneurismal) of the main and major branch PAs, producing variable amounts of tracheo-bronchial tree
compromise. Inner cardiac structure is reasonably akin to that found with Types I, II, and III TOFs
described in the preceding sections of this paper. However, infundibular obstruction is rare. Also, the
ductus arteriosus is absent in the majority of cases. This syndrome is typically seen in association with TOF,
even though it may infrequently be found as a sole abnormality. Other defects may also be encountered
with this syndrome: ASD, VSD, atrioventricular septal defect, and double outlet right ventricle
(DORV) [5,6,11] .

An echocardiogram shows a large VSD and over-riding aorta; such findings are similar to those seen with
the preceding three types of TOF [Figures 1 and 2]. Rudimentary or absent leaflets of the pulmonary valve
and hypoplasia of the pulmonary valve ring may also be detected [Figure 8]. Color flow imaging
demonstrates turbulent flow through the pulmonary valve [Figure 9A] with pulmonary insufficiency
[Figure 9B]. CW Doppler studies demonstrate an increased Doppler flow velocity indicative of a high
pulmonary valve peak systolic pressure gradient and evidence for pulmonary insufficiency [Figure 10]. The
main and branch PAs are aneurismally dilated; this can be documented on 2D echocardiograms [Figure 8].

TRANSPOSITION OF THE GREAT ARTERIES
Transposition of the great arteries (TGA) comprises 5% of all heart defects and accounts for 10% of all
cyanotic neonates. Indeed, TGA is the utmost frequent cyanotic heart defect in neonates [3,4,12,13] . In TGA, the
PA arises from the morphologic left ventricle (LV) while the aorta comes off of the morphologic RV. In the
utmost common variety - called complete TGA - normal position of the atria (atrial situs solitus) is present,
the right atrium (RA) is connected to the RV and the left atrium (LA) is connected to the LV
[atrioventricular (AV) concordance], the RV is on the right and the LV on the left (d-loop of the ventricles),
and the aorta arises from the RV and the PA from the LV (ventriculo-arterial discordance). Most