 |
| Fig. 60 |
Echocardiographic images of the great arteries can often be obtained
by positioning the transducer in the suprasternal notch. As shown
in Fig. 60,
the subject lies supine, with the head tilted back over a pillow.
If the transducer is positioned so that the scan plane is aligned
with the aortic arch, it may be possible to see the ascending aorta
passing posteriorly and turning downward, with some of the arteries
that supply the head and arms arising from it (Figs.
61-63). Within the loop of the aortic arch, the right pulmonary
artery may be seen as a pulsating circular structure.
If the scan plane is rotated through 90 degrees, the aorta will
be seen in cross-section, with the right pulmonary artery forming
two parallel lines below it. Slight adjustments in scan direction
may reveal part of the roof of the left atrium and, if sufficient
depth range is available, the mitral valve annulus.
Recordings of the aortic arch can be used to diagnose coarctation
and to determine both the site of the stricture relative to the
subclavian artery and its approximate extent. In patients whose
parasternal recordings reveal aortic root aneurysms, knowing whether
the enlarged region extends to the origins of the arterial branches
can be very helpful as an adjunct to angiography in assessing suitability
for surgery.
Although it is not always easy to identify the relevant structures
on M-mode recordings, the smaller transducer size and greater depth
of penetration allow tracings showing the aorta, right pulmonary
artery, and part of the left atrium to be made in the majority of
subjects. These are useful in congenital disease for showing the
relative sizes of the vessels as a means of assessing severity of
shunts, and also in conjunction with contrast injections for identifying
the great vessels in patients in whom the combination of transposition
and a shunt makes identification from the parasternal position difficult.
2004