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Pericardial effusions may be idiopathic, neoplastic, infectious, traumatic, toxic or may result from atrial rupture in dogs with myxomatous mitral valve disease (MMVD).
Pericardial effusions may be idiopathic, neoplastic, infectious, traumatic, toxic or may result from atrial rupture in dogs with myxomatous mitral valve disease (MMVD).
'''Neoplasia''' affecting the heart, heart base or pericardium is the '''most common''' cause of pericardial effusion in dogs.
'''Neoplasia''' affecting the heart, heart base or pericardium is the '''most common''' cause of pericardial effusion in '''dogs'''.
'''Idiopathic''' pericardial effusions are the second most common cause of pericardial effusion in the dog. Effusions are usually '''haemorrhagic''' and the cause is unknown. One study has demonstrated progression of idiopathic pericardial effusion to mesothelioma over time in a series of Golden Retrievers.
'''Idiopathic''' pericardial effusions are the second most common cause of pericardial effusion in the dog. Effusions are usually '''haemorrhagic''' and the cause is unknown. One study has demonstrated progression of idiopathic pericardial effusion to mesothelioma over time in a series of Golden Retrievers.
Hypoproteinaemia can cause pericardial effusion in both the dog and cat.
Hypoproteinaemia can cause pericardial effusion in both the dog and cat.
In cats, the majority of pericardial effusions are secondary to congestive heart failure caused by cardiomyopathy. However, cardiac lymphoma, heart based tumours and a variety of metastatic tumours have been reported as causes of pericardial effusion. Additionally, feline infectious peritonitis virus (FIP) may cause pericardial effusions.
In '''cats''', the majority of pericardial effusions are secondary to '''congestive heart failure''' caused by cardiomyopathy. However, cardiac lymphoma, heart based tumours and a variety of metastatic tumours have been reported as causes of pericardial effusion. Additionally, feline infectious peritonitis virus (FIP) may cause pericardial effusions.
===Signalment===
===Signalment===
====Echocardiography====
====Echocardiography====
Pericardial effusion is visible as a hypoechoic (black) area surrounding the heart. Cardiac tamponade is characterized by collapse of the right atrium +/- the right ventricle during diastole or systole. In severe cases, there is also underfilling of the left ventricle which gives it the appearance of being thickened ('''pseudohypertrophy''').
Pericardial effusion is visible as a hypoechoic (black) area surrounding the heart. Cardiac '''tamponade''' is characterized by collapse of the right atrium +/- the right ventricle during diastole or systole. In severe cases, there is also underfilling of the left ventricle which gives it the appearance of being thickened ('''pseudohypertrophy''').
Echocardiography is also useful to establish the cause of the pericardial effusion. Mass lesions may be small and difficult to distinguish in some cases, but may be very easily identified in others. Haemangiosarcomas can be seen infiltrating the right atrium, whereas heart base tumours typically surround the aorta and pulmonary artery.
Echocardiography is also useful to establish the cause of the pericardial effusion. Mass lesions may be small and difficult to distinguish in some cases, but may be very easily identified in others. Haemangiosarcomas can be seen infiltrating the right atrium, whereas heart base tumours typically surround the aorta and pulmonary artery.
===Pericardial Fluid Analysis===
Fluid should always be sent for further analysis, including total and differential cell counts, packed cell volume, specific gravity, cytology, bacterial culture and sensitivity. Pericardial effusions can be classified as haemorrhagic, transudate, modified transudate and exudate and the classification informs the likely underlying cause. Differentiating reactive mesothelial cells from neoplastic mesothelial cells can be incredibly difficult, sometimes a diagnosis can only be made following histopathological and immunohistochemical examination of the excised pericardium.
Differentials are as follows:
- Haemorrhagic: idiopathic, neoplastic (Haemangiosarcoma, heart base tumour, lymphoma, mesothelioma), trauma, coagulopathy, ruptured left atrium
- Transudate: hypoproteinaemia
- Modified transudate: right-sided congestive heart failure, neoplasia
- Exudate: feline infectious peritonitis (FIP), infection (bacterial, fungal), foreign body
===Treatment===
===Treatment===
====Pericardiocentesis====
'''Pericardiocentesis''' is a useful diagnostic test as well as treatment. This is the only effective treatment for cardiac tamponade. Diuretics should '''not''' be given prior to pericardiocentesis, as they will reduce circulating fluid volume and therefore preload. This will further decrease cardiac pressures, cardiac output and exacerbate tamponade. It is advisable to have continuous ECG monitoring throughout the procedure, as any contact with the myocardium may result in arrhythmias.
The effusion frequently has a haemorrhagic appearance, regardless of underlying aetiology. It is possible to inadvertently sample blood from the right ventricle during attempted pericardiocentesis. The effusion sample can be differentiated from right ventricular blood by the fact it does not clot.
-Pericardiectomy (recurrent idiopathic effusion)
Removal of large volumes of pericardial effusion can result in a dramatic improvement in preload and a sudden increase in the size of the right atrium. In some cases, this results in a transient atrial fibrillation which lasts 24-72 hours and does require treatment.
-Surgical Removal (foreign bodies)
Risks of the procedure include:
- Haemorrhage
- Ventricular arrhythmias
- Accidental puncture of the right ventricle and removal of right ventricular blood, resulting in hypovolaemic shock
- Coronary laceration (reduce risk by using the right side for pericardiocentesis)
- Tumour laceration
- Infection
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===Prognosis===
===Prognosis===