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Issue Sixty-Two – December 2012
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CLINICAL CASE MANAGEMENT NEWSLETTER
The Calgary Animal Referral & Emergency Centre Animal Hospital
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Issue Sixty-Two – December 2012
Pericardial Effusion: Diagnosis and Stabilization
John Murray, DVM
Pericardial effusion is an abnormal accumulation of fluid within the pericardial sac. There
are a multitude of differential diagnoses for this condition, including neoplastic, infectious,
metabolic, toxic, cardiovascular, traumatic, and idiopathic. Regardless of the cause, the
hemodynamic consequences of pericardial effusion can range from relatively mild or nonexistent (if the pericardium has expanded; typically only occurs with chronic effusions) to
severe and life-threatening. In the latter scenario, there is a marked increase in intrapericardial
pressure resulting in greatly decreased ventricular filling during diastole (cardiac tamponade).
This in turn results in decreased cardiac output and hypotension. Death can occur if the
pericardial effusion is not resolved, making rapid diagnosis and treatment of this condition
critical to case management.
For neoplastic and idiopathic pericardial effusions, the typical signalment is older large breed
dogs, though these conditions do occur in small breed dogs as well. Toxic, infectious, and
traumatic pericardial effusions can occur in any breed, sex, or age of cat or dog. Cats or dogs
with congestive heart failure may have a relatively insignificant degree of pericardial effusion.
Older small breed dogs with severe degenerative mitral valve disease may experience left
atrial rupture and subsequent pericardial effusion.
Historical complaints are similar to those seen with right-sided heart failure, including lethargy,
anorexia, syncope, weakness, vomiting, dyspnea, and exercise intolerance. Abdominal
distension may occur due to ascites and hepatic congestion.
Common physical examination findings include muffled heart sounds, weak femoral pulses
/ arterial hypotension, sinus tachycardia, pale mucus membranes, and jugular venous
distension. Pulsus paradoxus (an exaggerated decline greater than 10 mm Hg in systemic
arterial pressure during inspiration) is highly suggestive of cardiac tamponade and can be
detected on palpation of femoral pulse quality.
Though pericardial effusion can be highly suspected based on historical and physical
examination findings, additional diagnostics are required to confirm the diagnosis. Thoracic
radiographs will typically reveal an enlarged and globoid cardiac silhouette. However, with
peracute and small volume pericardial effusions, the degree of change seen may be mild
and the diagnosis may be uncertain. Elevation of the trachea and distension of the caudal
vena cava may also be seen. Pleural effusion may be seen and can obscure the cardiac
silhouette, making the diagnosis difficult. Electrocardiography may reveal ventricular or
supraventricular arrhythmias, in addition to sinus tachycardia. If present, electrical alternans
(beat-to-beat variations in the contour and amplitude of the QRS complex, ST segment, and T
wave) is highly suggestive of pericardial effusion. However, this is only seen in a small number of
cases. With relatively little training, echocardiography can be used to confirm the diagnosis of
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Issue Sixty-Two – December 2012
pericardial effusion by identifying a hypoechoic or anechoic space between the epicardium
and pericardium. The lack of readily available ultrasound should not preclude therapeutic
intervention in the form of pericardiocentesis and other supportive measures if the patient is
unstable and pericardial effusion is suspected.
Intravenous crystalloid fluids can be used to improve diastolic filling and help alleviate a shock
state if indicated. Fluids must be used judiciously and with careful monitoring as patients
may not tolerate excessive volumes of IV fluids. It is important that pericardial effusion not
be confused with heart failure, as the use of arterial or venodilators, diuretics, or positive
inotropes may be harmful. Pericardiocentesis is necessary to relieve the state of cardiac
tamponade. Light sedation may be necessary to perform the pericardiocentesis safely.
Opiates (eg. butorphanol) with or without a benzodiazepine are the safest choices as they
have minimal cardiovascular side effects. In more severely compromised patients, local
anesthesia including the skin, intercostal musculature, and parietal pleura at the intended site
of pericardiocentesis may be sufficient. The procedure is performed with the patient in either
left lateral or sternal recumbency. The right thorax is clipped and aseptically prepared from
the second to eighth intercostal space. Pericardiocentesis is performed at either the fourth
or fifth intercostal space, cranial to the rib to avoid lacerating the intercostal vasculature. A
22g (cat) or up to 14g IV catheter (large dog) of appropriate length is selected. The catheter
is slowly advanced into the pericardium until fluid is retrieved, at which point the catheter is
advanced over the needle and into the pericardial space. The catheter is then connected
to a closed collection system and fluid slowly withdrawn. A needle can be used instead of
a catheter, but may be associated with greater risk of cardiac puncture. The character of
the fluid is often hemorrhagic, however it can certainly vary. Samples of the fluid should be
collected for later analysis. If pleural effusion is present secondary to cardiac tamponade, this
fluid will be encountered before entering the pericardial space and will typically appear grossly
as a transudate or modified transudate. The catheter will need to be advanced further until a
more characteristic pericardial effusion is retrieved. If uncertain, then fluid can be withdrawn
and the patient monitored for clinical improvement. Sinus tachycardia will typically improve
at least to some degree with removal of the pericardial fluid. If a clinical improvement is not
appreciated, then the fluid being collected is likely pleural.
When performed carefully, serious complications associated with pericardiocentesis are rare.
Electrocardiographic monitoring is ideally available during pericardiocentesis as arrhythmias
may be noted if the catheter is advanced too far and contacts the heart. Arrhythmias will
typically resolve if the catheter is withdrawn. If not, then appropriate medical intervention
should be considered. As with ultrasound, the lack of available ECG monitoring should not
preclude pericardiocentesis in a patient that is severely unstable as death may be imminent.
Cardiac puncture may occur if the catheter is inadvertently advanced into the heart. In most
instances of cardiac puncture, the hemorrhagic fluid collected will be seen to clot. Typically,
pericardial effusion will not clot after collection, even when hemorrhagic in nature. However,
in the event of peracute or active hemorrhage into the pericardial space, the pericardial fluid
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may still clot after collection. If cardiac puncture is suspected, then the catheter should be
withdrawn. Further and potentially significant hemorrhage into the pericardial space may
occur if a tumor or coronary sinus is lacerated.
Signs of shock and right sided heart failure typically improve rapidly after pericardiocentesis is
performed and cardiac tamponade resolved. In the case of hemorrhagic pericardial effusions,
the patient may be anemic and clinical signs related to anemia or hemorrhage may persist.
Depending on the etiology, recurrence of pericardial effusion and cardiac tamponade may
occur rapidly and continued patient monitoring is recommended.
Once the patient is stabilized, further diagnostic evaluation is necessary to determine the
etiology of the pericardial effusion. Echocardiography is useful to evaluate for a neoplastic
source. Submission of pericardial fluid for cytology and culture may be beneficial. Cytology
alone cannot rule out a neoplastic cause for the effusion, as neoplastic cells may not exfoliate
and even if they do they may be difficult to identify within a vastly hemorrhagic effusion. A
coagulation profile should be performed if a coagulopathy is suspected. Pericardial effusion
secondary to uremia or cholesterol-based pericardial effusion associated with hypothyroidism
can be ruled in or out with basic bloodwork. Idiopathic pericardial effusion is a diagnosis
of exclusion. This can be a difficult diagnosis to make, as the lack of a visible tumor on
echocardiography does not definitively exclude the possibility of a neoplastic cause for the
effusion.
In summary, a number of inciting causes may result in pericardial effusion. The severity of
clinical signs can vary greatly depending on the magnitude of the increase in intrapericardial
pressure and presence of cardiac tamponade. A diagnosis of pericardial effusion can be
highly suspected based on historical and physical examination findings, as well as readily
available diagnostics such as thoracic radiography. Even in the absence of confirmed
pericardial effusion on echocardiography, life-saving pericardiocentesis can be performed
with relatively little risk if pericardial effusion is suspected and the patient is in critical condition.
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