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accumulation of
fluid in the pericardial sac. A large effusion inducing a
rise of
intrapericardial pressure causes cardiac compression and
symptoms of
pericardial
tamponade. There are many aetologies for effusion
including: pericarditis,
pericardial infection, pericardial tumours, postpericardiotomy
syndrome, radiation, collagen vascular diseases,
uraemia, heart
failure, chylopericardium
and myxoedema. The effusion may be loculated, especially
after
cardiac surgery. Chest X-ray suggests the diagnosis when
there is
enlargement of the cardiac silhouette over a short time
interval
especially in the absence of pulmonary venous hypertension
or
oedema. The lateral view may show the fat pad sign
consisting of
separation of the parietal and epicardial fat layers by more
than
3 mm. Echocardiography
is usually employed for definitive diagnosis. Computed
tomography
and MRI are very sensitive techniques for demonstrating
effusions
(Fig.1).
Haemorrhagic effusions are characterized by high density on
CT and
high signal intensity on T1-weighted spin echo MRI (Fig.2).
CBH
The
Encyclopaedia
of Medical Imaging Volume V:2 |
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Pericardial
effusion, Fig. 1
ECG-gated
spin-echo image shows a large pericardial effusion. This
transudative effusion has low signal intensity.
Pericardial
effusion, Fig. 2
ECG-gated
spin-echo image demonstrates a loculated pericardial
effusion. This
haemorrhagic effusion has high signal intensity.
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