Page 100 - Read Online

Page 10 of 41 Rao. Vessel Plus 2022;6:25 https://dx.doi.org/10.20517/2574-1209.2021.92

2
Peak instantaneous gradient = 4V
V, maximum peak velocity via the pulmonary valve in m/s.

Other varieties of RV obstructions may also occur; these are: infundibular pulmonary stenosis, double-
chambered RV, PA narrowing above the pulmonary valve (supravalvar) either isolated or in association
with Williams syndrome, and distinct sub-pulmonary membranous stenosis (or other types of obstruction)
in the morphological LV (positioned on the right) of congenital corrected transposition of the great
arteries ; but these are relatively rare and will not be reviewed. However, branch PA stenosis is relatively
[15]
frequent and will be briefly reviewed.

The utility of echo-Doppler studies in evaluating immediate [Figures 14-17] and follow-up [Figures 16-18]
results after balloon pulmonary valvuloplasty [17-20] and surgery is well established.

Branch pulmonary artery stenosis
In utero, most of the RV output is ejected into the Ao through the ductus arteriosus [21-24] . Only 7% of the
output from both the ventricles is pumped into the lungs. Consequently, the PA branches are small in
diameter. After the baby is born, the pulmonary vascular resistance decreases and the ductus arteriosus
closes; these changes will result in augmented pulmonary blood flow. In an attempt to adapt to this
augmented pulmonary blood flow, the flow velocity in the branch PAs increases, which in turn causes
turbulence in the PA branches. These flow dynamics produce cardiac murmurs. As the infant grows, the
branch PAs become larger in diameter and the physiologic branch PA stenosis disappears.

Neonates with branch PA stenosis generally exhibit cardiac murmurs that are auscultated at the left upper
sternal border. This murmur radiates into the axillae and back. Alternatively, the branch PA stenosis may be
identified during echocardiograms performed for some other indication. These babies have no other
symptoms and generally have no other abnormal heart findings. Echo-Doppler studies show fairly small
branch PAs [Figure 19] and elevated Doppler flow velocities across the branch PAs [Figure 19C-E].

LEFT-TO-RIGHT SHUNT LESIONS
Atrial septal defect
There are several varieties of atrial septal defects (ASDs), and these are: ostium secundum, ostium primum,
sinus venosus, and coronary sinus ASDs [24,25] . Another atrial defect is the patent foramen ovale (PFO) [24,25] .
Ostium secundum ASDs are the most frequent among ASDs and comprise 8% to 13% of all CHDs. In
subjects with ostium secundum ASD, a lack of atrial septal material in the fossa ovalis area is seen. The atrial
defects range from small to large in size. These are usually single defects, although, on occasion, fenestrated
or multiple defects are present. Shunting across the ASD [from the left atrium (LA) to the right] produces
dilation of the right atrium (RA) and RV. The PAs are similarly dilated. Pulmonary hypertensive changes do
not generally occur until late adult life [24,25] .

Echo-Doppler examination shows dilated RA, RV and PAs [Figure 20] with paradoxical ventricular septal
movement, well demonstrated on M-mode tracings [Figure 21A]. By 2D echo, the ASD can be clearly seen
[Figures 21B, 22A, 23A and 24A], and shunting from the LA to RA via the ASD [Figures 22B, 23B and 24B]
is demonstrated by color flow Doppler. These are best illustrated in subcostal views. In some subjects,
pulmonary venous or systemic venous anomalies may coexist with ASD and therefore, the normalcy of
pulmonary and systemic venous return should be established in each case. In adolescents and adults with
poor subcostal acoustic windows, trans-esophageal (TEE) or intra-cardiac (ICE) echocardiography may
become necessary to clearly discern the presence of an ASD and the hemodynamic significance of the