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Chapter 22: Pericardial Effusion and Other Disorders 347

pericardiocentesis from the left or right precordium, but
the ideal location can be best assessed via echocardiog-
raphy (which allows one to choose the space with the
largest fluid pocket). The patient should be restrained in
lateral recumbency and the intercostal space should be
LV
blocked with 1 cc lidocaine using a 25–27 gauge needle.
LA Some cats may need sedation in addition to the local
lidocaine block. The catheter/butterfly should be
PE
attached to a 3-way stopcock as described for thoraco-
centesis (see discussion regarding pleural effusion
removal in Chapter 3). An electrocardiogram should be
placed to evaluate for new ventricular arrhythmias that
may occur if the ventricle is contacted. Complications
secondary to pericardiocentesis are rare, but they include
Figure 22.4. Long-axis echocardiogram obtained at the right cardiac puncture, cardiac arrhythmias, and/or laceration
parasternum of a cat with pericardial effusion (PE). Note the of the tumor or coronary artery. If the catheter is rapidly
anechoic fluid surrounding the heart. LA = left atrium; LV = left withdrawn and repositioned, the patient is often not
ventricle.
clinically compromised by these possible problems
(Gidlewski and Petrie 2005). See Box 22.1 for a more
dence of underlying primary heart disease, such as specific description of the pericardiocentesis procedure.
hypertrophic cardiomyopathy; however, in some indi- The gross character of pericardial effusion in cats often
viduals the heart is normal and another underlying differs from dogs; it rarely appears hemorrhagic in cats
cause may be found, such as neoplasia. With some neo- and can be difficult to differentiate from pleural effusion,
plasms, the mass will be evident in association with the which is also often concurrently present. If this dilemma
heart or great vessel(s); however, myocardial infiltration arises, a few ml of agitated (microbubbled) sterile saline
is a common presentation for cardiac lymphoma, the may be injected into the centesis catheter, and ultra-
best-recognized cardiac tumor in the cat (Meurs et al. sound is used for identifying whether the contrast
1994). See Chapter 16 for further discussion regarding appears in the pleural or pericardial fluid, confirming the Pericardial Diseases
cardiac neoplasia. location of the catheter tip. Cytologic analysis of PE
Although rare, evidence of cardiac tamponade should should be performed if infectious or neoplastic etiolo-
be sought if PE is present on echocardiography. The gies are possible (i.e., most cases of PE causing cardiac
right atrial free wall is normally rounded throughout the tamponade in cats). Malignant lymphocytes generally
cardiac cycle. Evidence of right atrial inversion or col- exfoliate readily in feline PE caused by lymphoma
lapse during the cardiac cycle suggests elevated intra- (Brummer and Moïse 1989).
pericardial pressure. If present, inversion usually occurs
in late diastole and extends variably into ventricular CONSTRICTIVE PERICARDITIS
systole. Similarly, if more advanced right ventricular
tamponade is present, the right ventricular free wall will Pericardial constrictive disease occurs when the visceral
move inward or collapse during diastole. and parietal pericardial layers become fused or fibrotic
When echocardiographic evidence of cardiac tam- (Figure 22.5). The pericardial space may be totally oblit-
ponade is noted, pericardiocentesis is essential for thera- erated or may contain a small amount of PE. Constrictive
peutic purposes as well as diagnostic purposes. pericarditis is a difficult diagnosis to make by echocar-
Tamponade rarely develops with PE secondary to con- diography, but if clinical signs and echocardiographic
gestive heart failure, but it has been recognized in several findings are consistent with the diagnosis, cardiac cath-
cases in which PE was caused by neoplasia (Zoia et al. eterization for intracardiac pressure assessment is diag-
2004; Hall et al. 2007). Therefore, a subset of cats with nostic. Since early ventricular relaxation is often normal,
pericardial effusion will have cardiac tamponade and ventricular diastolic pressure drops normally; however,
require pericardiocentesis. Pericar diocentesis with cyto- ventricular pressure rapidly increases with early filling
logic fluid analysis is also important for the diagnosis of because the limit of ventricular distensibility is met very
infectious etiologies. Pericar diocentesis can be achieved early in diastole. This phenomenon will appear as a
with an 18–20 gauge catheter or a butterfly needle con- “square root sign” on a right ventricular pressure
nected to a three-way stop cock (depending on the size trace obtained through cardiac catheterization. Other
of the cat). Cardiologists may preferentially perform hemodynamic abnormalities include elevation and