An uncommon but important condition is a left atrial tumor, most
frequently a myxoma, which partially bocks the mitral orifice
and can, therefore, be indistinguishable from mitral stenosis
on clinical examination.
 |
| Fig. 9 |
In most cases, M-mode recordings are diagnostic of this condition.
As (Fig.
9) shows, the tumor produces an amorphous cloud of echoes
that appears behind the mitral valve leaflet shortly after the
valve opens. Depending on the mobility of the tumor, other recordings
will show it in the left atrium during systole, and descending
into the body of the left ventricle later in diastole. The anterior
mitral leaflet is usually normal in thickness in this situation.
The opening of the normal mitral leaflet in diastole, followed
by the appearance of the mass lesion an instant later serves to
differentiate the M-mode appearance of mitral stenosis and atrial
myxoma.
 |
| Fig. 10 |
The spatial presentation of echocardiographic data offered by
two-dimensional echocardiography makes the diagnosis of left atrial
myxoma quite easy in most cases (Fig.
10). The size, mobility, and point of attachment of the tumor
can be determined with some accuracy. Its motion exhibits a "rocking"
action about the point of attachment, normally to the interatrial
septum just behind the anterior mitral leaflet. Indeed, if it
appears to be attached elsewhere it is more likely to be a malignant
myosarcoma or lymphoma.
 |
| Fig. 11 |
Additional two-dimensional short-axis and four-chamber views
(Fig.
11) not only provide further graphic evidence of the tumor,
but also greatly reduce the chance of accidentally missing the
diagnosis because of small tumor size, lack of mobility, or abnormal
attachment point. As a result, echocardiography obviates the need
for invasive and dangerous techniques such as angiography.
 |
| Fig. 12 |
Such left atrial tumors have, infrequently, been reported to
the bilateral. The usual mechanism for extension into the right
atrium is growth of the tumor through the fossa ovalis (Fig.
12).
 |
| Fig. 13 |
Careful examination of both the left and right atria as well
as the interatrial septum are required in such patients as it
gives useful information to the surgeon in planning the surgical
approach. Surgical removal of atrial myxoma requires resection
of the atrial septum at the point of attachment to prevent regrowth
of the myxoma (Fig.
13).
 |
| Fig. 14 |
Myxomas may occur in any cardiac chamber and on any cardiac valve.
The second most common area of occurrence after the left atrium
is the right atrium
(Fig. 14).
 |
| Fig. 15 |
As with left atrial locations such tumors often prolapse into
the valve orifice in diastole, impeding forward flow of blood
through the heart (Fig.
15). Wherever their location, the echocardiographic identification
of such mass lesions is indication for surgical removal in suitable
surgical candidates due to their propensity for obstruction to
flow and the high rates of embolization of such tumors.
2004
