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Echocardiography
in Practice
A Case Oriented Approach
by Susan Wiegers, Ted Plappert, and Martin St. John Sutton
Right Atrial Thrombus
Susan E. Wiegers, MD
A 60-year-old man with a history of lung carcinoma treatcd with
surgery and radiation developed sick sinus svndrome and had a permanent
pacemaker placed. Several months later he was admitted with pleuritic
chest pain and mild shortness of breath. A lung ventilation and
perfusion scan was positive for multiple subsegmental defects.
Due to the high probability of a pulmonary embolus, an echocardiogram
was done to assess right ventricular function.
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Figure 16.1
(a) Apical four-chamber view in systole
demonstrates a moderately dilated left ventricle (LV) and left
atrium (LA). The right ventricular cavity size (RV) is normal.
A pacemaker wire is seen in the right ventricular cavity. There
is a large mass (arrow) at the level ot the tricuspid valve
which appears to fill the tricuspid valve orifice. (b) In diastole
a magnified image of the same view shows apparent attachment
of the right atrial mass to the interatrial septum. The posterior
and lateral walls of the right atium are not normal
and contain tissue with an echodensity similar to that of
the mass. |
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Figure 16.2
An off-axis subcostal view demonstrates
an intact interatrial septum without definite attachment of
the mass (arrow) to the septum. This image is obtained by angulation
of the transducer from the standard sub-xiphoid position. |
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Figure 16.3
A close-up of the right atrium in the previous
view demonstrates that the inferior vena cava (IVC) is widely
patent and contains no masses. The nature of the mass (arrow)
is not clearly defined |
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Figure 16.4
Transesophageal echocardiogram in the longitudinal
axis (90°) in the mid-esophagus. The pacemaker (small arrow)
is seen the superior vena cava entering the right atrium (RA).
The pacemaker acoustic shadow is thickened and in real time
demonstrated chaotic motion at its edge. This finding is highly
suggestive of thrombus or vegetation associated with the pacemaker
wire. The right atrial mass (large arrow) does not appear to
be attached to the pacemaker in this view. However, rotation
of the transducer demonstrated the attachment of the large
mass to the pacemaker wire at the level of the tricuspid annulus. |
Discussion
The differential diagnosis of the
right atrial mass in this case includes myxoma, metastatic tumor,
thrombus and vegetation. Initial images suggested the attachment
of the mass to the interatrial septum, raising the question of atrial
myxoma. However, additional views demonstrated that this was not
the case. Off-axis images are especially important in evaluation
of the interatrial septum since the septum is parallel to the ultrasound
beam in the standard apical and parasternal short-axis views.
Dropout of the image may occur in these views because optimal two
dimensional imaging requires structures to be perpendicular
to the ultrasound beam. While chamber size cannot be accurately
determined from off-axis views, certain anatomic information may
be reliably obtained. A myxoma would almost certainly have an
attachment to the interatrial septum, thus excluding this diagnosis.
In addition, the mass was not present on the echocardiogram performed
3 months earlier, prior to the pacemaker placement. While a metastatic
tumor might demonstrate such rapid growth, it is unlikely that
this large, intracardiac mass represents a neoplasm.
It is clear
from Figure 16.a and b that the mass is not attached to the tricuspid
valve leaflets, since it does not exhibit any motion between the
systolic and diastolic frames. The mass is very large to be a vegetation,
particularly in an afebrile patient with little history to suggest
the diagnosis. Vegetations may be associated with pacemakers rather
than valve leaflets. In this case, the presence of an additional
mass along the posterior wall of the right atrium is highly suggestive
of thrombus. The nature of the mass was confirmed by the transesophageal
echocardiogram which demonstrated attachment of the thrombus to
the pacemaker in the superior vena cava and the right atrium. Both
transthoracic and transesophgeal echocardiography nave occasionally
demonstrated the presence of a right atrial clot in patients with
acute pulmonary embolism1,2 Treatment must be
individually tailored.
In this casae, the patient was pacemaker dependant but had a limited
life expectancy, owing to the presence of recurrent lung carcinoma. Thrombolysis
was contraindicated because it was feared that partial lysis of
the clot would result in embolism of a large mass leading to acute
compromise. He was treated with heparin followed by oral
anticoagulation with partial resoltion of the atrial mass and no
further clinical sequelae.
References
1. Redberg RF, Hect SR, Berver M. Echocardiographic detection
of transient right heart thrombus: now you see it, now you don't
[see comments]. Am Heart J 1991;122:862-4.
2. Adamick R, Zoneraich S. Echocardiographic visualization
of a large mobile right atrial thrombus with sudden embolization
during real-time scanning. Am Heart J 1990;120:699-701.
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