In its most
severe form, loss of structural strength in the aortic walls leads
to aneurismal dilation and/or dissection of the intima. The dilation
is at best documented by two-dimensional echocardiography, using
the parasternal long-axis view to visualize the ascending aorta
and the suprasternal position to see the aortic arch.
In cases where there is gross dilation at the valve level, the aortic
cusps may show a pattern of early partial closure and fluttering
indistinguishable from that characteristic of subvalvar aortic stenosis.
This is probably caused by turbulent eddies of blood in the sinuses
of valsalva produced by the high ejection velocity into the dilated
aorta. With careful technique and good apparatus, high success has
been reported in detecting dissection by two-dimensional echocardiography
and in classifying it according to the DeBakey criteria.
The use of M-mode alone, however, leads to many false positives
because of the difficulty in obtaining correct beam angulation and
an inability to distinguish, for example, a true dissection from
a double echo generated by the bulbous sinuses of valsalva or the
transverse sinus of the pericardium posteriorly.
 |
| Fig. 56 |
Even more productive is the use of transesophageal echocardiography
where a small transducer, mounted on a flexible endoscope is inserted
into the esophagus. Using this approach provides superior images
of the ascending aorta and proximal transverse aortic arch in almost
all patients. (Fig. 56) shows a short-axis transesophageal image
of the proximal aorta where true and false lumens are easily visualized.
2004
