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Page 24 of 43 Rao. Vessel Plus 2022;6:26 https://dx.doi.org/10.20517/2574-1209.2021.93

open mitral valve, the LV diameter is minute. Fibroelastosis of the endocardium is frequently seen. Stenosis
of the aortic valve is present or it is atretic. The ascending portion of the aorta is frequently hypoplastic and
its diameter may be between 2 and 3 mm and serves as a channel to perfuse the coronary arterial system
retrogradely. Aortic coarctation is seen in a large percentage of cases with this anomaly; however, an
interrupted aortic arch is uncommon. The right side of the heart, namely, RA, RV, and PAs, are markedly
dilated. A PFO with a left to right shunting is commonly present. Sometimes, it is small and restrictive. On
rare occasions, the PFO is fully closed (intact atrial septum). VSD is not usually seen, and it is generally
thought to be not an important part of HLHS; however, it has been found in patients with mitral valve
atresia with normal aortic root. PDA is seen immediately following birth; however, it is likely to constrict as
the baby ages. Markedly hypoplastic LV can be seen in babies with DORV and unbalanced AV septal defect
(AVSD); such variants constitute nearly 25% of all hypoplastic left hearts.

Echocardiographic features of HLHS are hypoplasia of the LV [Figures 44-46] and ascending aorta
[Figures 44 and 47]. In addition, there may be hypoplasia, stenosis or atresia of either the aortic [Figures 44
and 47] and/or mitral [Figure 45] valves. The LA is generally small [Figures 44 and 45].

The RA, RV [Figures 44-48], and main PA [Figures 44, 48 and 49] are dilated and are easily seen on 2D
imaging. The degree of patency of the PDA should be assessed [Figures 49]. Evaluation of the arch of the
aorta and descending aorta should be undertaken to confirm or exclude coarctation of the aorta.

Hemodynamic information may be appraised by a combination of pulsed and CW Doppler and color flow
imaging. Doppler examination of the transverse aortic arch reveals retrograde flow [Figures 50 and 51],
which identifies systemic circulation that is ductal dependent and that the LV is not adequate for going with
a biventricular type of repair. High Doppler velocity through the PFO indicates restriction of the inter-atrial
defect [Figure 52].

The dimension of the LV differs from one patient to the next, as shown in [Figures 53 and 54]; but all of
them have similar physiology and require the same type of Norwood palliation. Similarly, the diameters of
the ascending aorta also vary [Figure 55], and again all these patients require similar Norwood surgery, but
some studies indicate a very small ascending aorta (< 1 mm) may put them at an increased risk for poor
prognosis after the Norwood palliation.

DOUBLE-OUTLET RIGHT VENTRICLE
DORV is an uncommon CHD; in this anomaly, both the PA and aorta originate from the morphological
RV [22,38,39] and comprise close to 1% of all congenital cardiac defects. Several definitions to describe this
anomaly have been proposed; most common of these are: (1) both great vessels arise from the RV and none
of the great vessels have fibrous continuity with the AV valves; and (2) one whole great artery and larger
than one-half of the remaining great artery come off of the RV. A large VSD is typically seen and is the only
exit from the LV. The size and location of the VSD establish the pathophysiology. In the most common
type, the ventricular defect is perimembranous and sub-aortic in location, directing the LV blood into the
aorta and this type constitutes 50% of all DORV cases. In the absence of PS, the clinical features are akin to
those of the usual VSD. In patients with significant PS, the clinical presentation is similar to those of
tetralogy. In cases with the VSD in the sub-pulmonary region, the LV output is mostly directed into the PA;
this will result in physiology similar to that of TGA, and such a defect is commonly called as Taussig-Bing
malformation. This variety comprises 25% of all DORV cases. In the leftover 25% of patients, the ventricular
defect is either non-aligned with either great artery or is doubly committed equally to both arteries [22,38,39] .
The VSD is typically large; however, it may be absent in very rare cases causing LV hypoplasia. In some