Page 309 - Clinical Small Animal Internal Medicine

28 Pericardial Disease 277

pericardial cysts, with repair of a PPDH when present, bifurcation of the carotid artery near the base of the heart.
VetBooks.ir has been reported. The chemoreceptor system responds to changes in pH
and the partial pressure of arterial oxygen and carbon
Prognosis dioxide in the blood. These tumors tend to be slow grow-
ing and locally invasive, causing compression or infiltra-
The majority of animals with clinical signs will improve tion of adjacent structures. Chemodectomas can occur in
following surgical correction. The mortality rate follow- any breed but brachycephalic breeds appear predisposed
ing surgery for PPDH varies between 5.1% and 14%. The (boxer, bulldog, Boston terrier). Mean age at presentation
mortality rate following surgical repair of PPDH is higher is 10 years. Heart base tumors are intimately associated
if reexpansion pulmonary edema or hemorrhage occurs, with vascular structures, making complete surgical exci-
although improvements in anesthesia and postoperative sion and radiation therapy problematic. In dogs with
management have most likely improved the prognosis. heart base tumors assumed to be chemodectomas and
clinically significant pericardial effusion, palliation with
pericardiectomy significantly extends survival. In the
Pericardial Effusion absence of significant pericardial effusion, these tumors
can be an incidental finding in dogs undergoing an
echocardiogram for another indication.
Etiology/Pathophysiology
Mesothelioma is a neoplasm of the pericardium and
Accumulation of fluid within the pericardial space can serosal surfaces. It is relatively uncommon and is not
cause hemodynamic abnormalities depending on the characterized by an easily identifiable discrete mass,
volume and rate of fluid accumulation as well as intra- making it difficult to diagnose. Diagnosis of mesotheli-
cardiac filling pressures and compliance. The resulting oma requires histopathology of the pericardium and is
hemodynamic changes and decrease in cardiac output therefore difficult to distinguish from idiopathic disease.
create a clinical syndrome called cardiac tamponade, Mesothelioma can develop secondary to chronic effu-
where increased intrapericardial pressure equals or sions. The mean age at diagnosis is 9.5 years.
exceeds intracardiac pressure, with the right side of the
heart most susceptible to compromise. Idiopathic
The most common causes of pericardial effusion in A cause for pericardial effusion cannot be identified in
dogs are neoplastic and idiopathic with rare cases of up to 23% of cases. Therefore, idiopathic is a diagnosis of
infectious pericarditis (bacterial, fungal), coagulopathy, exclusion. Affected dogs are typically medium to large
left atrial tear, heart failure, foreign body, and uremia. breed and middle aged. The reported mean age is slightly
The most common causes of pericardial effusion in cats less than that reported for dogs with a neoplastic etiol-
are heart failure, neoplastic and infectious (viral) with rare ogy. Of note, reports have identified small tumors on
cases of coagulopathy, foreign body, and uremia. necropsy and confirmed mesothelioma on histopathol-
ogy of pericardial tissue in dogs initially diagnosed with
Dogs idiopathic effusions.
Neoplastic
Primary or metastatic neoplasia is the most commonly Infectious
reported cause of pericardial effusion in dogs. The inci- Rare reports of systemic fungal disease (Coccidioides
dence of hemangiosarcoma and aortic body tumors immitis, Aspergillus niger), bacterial pericarditis (various
(chemodectoma) is higher than mesothelioma with infre- bacteria including botryomycosis) and protozoal infec-
quent reports of thyroid carcinoma, myxoma, and others. tion with Leishmania chagasi have been associated with
Hemangiosarcoma has a 10‐fold greater incidence pericardial effusion. In some cases, long‐term survival
than aortic body tumors in dogs. They are typically can be achieved with a combination of surgical manage-
located in the right atrium/auricle and are highly malig- ment and long‐term antibiotic or fungal therapy.
nant. The mean age at presentation is 9.8 years and mean
weight is 32 kg. Golden retrievers are overrepresented. Other
Survival times with combinations of pericardiocentesis, A left atrial tear can occur in dogs with degenerative
pericardiectomy, tumor resection, and/or chemotherapy mitral valve disease, most often resulting in acute clinical
are short. decompensation. An echocardiogram performed at the
Heart base tumors, most often chemodectoma or thy- time may document evidence of a thrombus in the peri-
roid carcinoma, are located near the aorta and main cardial space. Pericardial effusion secondary to heart
pulmonary artery. Chemoreceptor cells are found in failure is uncommon in dogs with heart disease and if it
groups at the ventrolateral surface of the aorta and the does occur, the effusion is typically scant and does not