Page 335 - Feline Cardiology

346 Section J: Pericardial Diseases

primary cardiac rhabdomyosarcoma with PE and cardiac
tamponade has been reported (Venco et al. 2001).
Pericardial effusion can also be infectious in origin. Feline
infective pericarditis has been associated with Esherichia
coli, Staphylococus aureus, Streptococcus, Enterococcus,
and Actinomyces infections (Reed 1988). PE has been
associated with feline infectious peritonitis (FIP) and
with toxoplasmosis, although the fluid is usually a sterile
inflammatory effusion. One case report describes a cat
with presumptive disseminated toxoplasmosis present-
ing with myocarditis and PE (Simpson et al. 2004). FIP A
PE typically has a high protein content, which appears as
a granular eosinophilic background on cytology. Finally,
feline pericardial effusion has been recognized to occur
secondary to uremia and coagulopathies.
Historically it was thought that FIP was the most
common cause of PE in cats, but two retrospective
studies later demonstrated that PE occurs most often
secondary to congestive heart failure (36–75% of cases)
(Davidson et al. 2008; Hall et al. 2007). The second most
common cause of PE in both studies was neoplasia (5–
19%) with lymphoma and adenocarcinoma occurring
most frequently. Both studies were retrospective and did
not assess the frequency of cardiac tamponade in these
cases. One report included only those cats with an ante-
Pericardial Diseases included those cats with pericardial effusion diagnosed B
mortem diagnosis (Hall et al. 2007), while the other

antemortem or on postmortem (Davidson et al. 2008).
In the authors’ experience, mild PE is a common finding
in cats with severe structural cardiac changes associated
with diseases such as cardiomyopathy. However, collapse
a moderate to marked amount of pericardial effusion. Note the
of the RA or RV (echocardiographic evidence of cardiac Figure 22.3. Lateral (A) and VD (B) radiographs from a cat with
tamponade) is rarely appreciated. This important obser- round, globoid cardiac silhouette, especially on the VD view.
vation highlights the difference between PE as an inci-
dental finding (e.g., in congestive heart failure, uremia,
others), where the volume of PE is usually small and no Findings on thoracic radiographs are also frequently
intervention specifically aims to quickly evacuate it, and less dramatic since the amount of effusion is often
PE as the principal cause of hemodynamic dysfunction smaller in cats with PE compared to dogs (Rush et al.
(cardiac tamponade) requiring pericardiocentesis. PE 1990). The cardiac silhouette may be generally enlarged
alone is an insufficient descriptor for the clinician; the and rounded and the edge of the cardiac silhouette is
amount of effusion, and most importantly, its effect on usually sharp owing to the lack of systolic and diastolic
the circulation, allow the clinician to decide whether motion associated with a distended pericardial sac
conservative treatment is sufficient or whether pericar- (Figure 22.3). The pulmonary vasculature and lung
diocentesis is needed. fields may be consistent with congestive heart failure
Electrocardiography will most often reveal a normal since CHF is a common cause of PE in the cat.
sinus rhythm or sinus tachycardia. If the volume of PE Echocardiography is the most sensitive and noninva-
is significant, the QRS complexes are often low in ampli- sive tool to confirm the presence of PE. With two-
tude. Electrical alternans, the beat-to-beat variation in dimensional echocardiography, PE appears as anechoic
amplitude of the QRS complexes, is rarely appreciated (black) to hypoechoic (grey) space surrounding the
in cats because the volume of PE is almost never large heart (Figure 22.4). If the cat also has pleural effusion,
enough to allow the swinging of the heart within the the pericardial sac can be visualized as an echogenic
pericardial sac, which produces this finding, and because (white) thin structure attaching to the base of the heart
feline QRS complexes are often small even in health. (see Figure 3.3). In most cats with PE, there will be evi-