Page 203 - Feline Cardiology

206 Section E: Other Forms of Structural Heart Disease

Signalment Treatment
There is no specific signalment or breed predisposition Treatment is dependent on the suspected etiology of the
for myocarditis. myocarditis. If heart failure is present, treatment should
be as described (see Chapter 19).
History and Chief Complaint
The history may be vague and include such findings as Outcome and Prognosis
inappetence and lethargy. However, some cats may Outcome and prognosis is dependent on the underlying
present with more advanced signs of cardiac involve- etiology and the response to therapy. A case report
ment, including signs of heart failure (dyspnea, tachy- of suspected Toxoplasma myocarditis demonstrates a
pnea) or an arrhythmia (syncope).
good response to medical therapy with clindamycin
(Simpson et al. 2005). In contrast, two reports of cats
Physical Examination with a myocarditis associated with Streptococcus canis
Misc. Heart Diseases may have a heart murmur if the myocarditis has resulted et al. 2008).
Affected cats may be dyspneic or tachypneic. Some cats
described a grave prognosis (Matsuu et al. 2007; Sura
in ventricular dilation or if the infectious agent has
involved a heart valve. A bradyarrhythmia or tachyar-
ENDOCARDIAL FIBROELASTOSIS
rhythmia may be detected.
Endocardial fibroelastosis is a rare cardiac disease
Diagnostic Testing
defined as diffuse thickening of the left ventricular
Electrocardiography endocardium secondary to proliferation of fibrous and
Cardiac arrhythmias may be observed depending on the elastic tissue.
location and diffuseness of the inflammation.
Supraventricular and ventricular tachyarrhythmias may Etiology, Pathophysiology, and Pathology
be observed as well as bradyarrhythmias including atrio- Etiology
ventricular block.
The etiology of endocardial fibroelastosis is poorly
Radiography understood. It appears to be inherited (primary endo-
Radiographs may be within normal limits or may dem- cardiofibroelastosis) in some breeds including Siamese,
onstrate atrial or ventricular dilation and evidence of Burmese, and some domestic shorthair cats (Rozengurt
heart failure (pulmonary edema, pleural effusion). 1994; Bonagura and Lehmkuhl 1999). Primary endocar-
dial fibroelastosis is best described in the Burmese cat,
Echocardiography where the heritable form has been observed to be a rapid
Echocardiography may demonstrate ventricular or atrial progression from normal histology at birth to symp-
dilation. The inflammation may affect the right and/or tomatic fibroelastosis by 2 months of age (Zook and
left side of the heart. Cardiac function may be impacted Paasch 1982).
by the inflammation and may include systolic and/or
diastolic dysfunction. In many cases, alterations in echo- Pathophysiology
genicity may be observed. Most frequently this is a Excessive fibroblast proliferation occurs in the left ven-
hyperechogenicity. In some cases a nodular or granular tricular endocardium, which produces collagen and
appearance of the myocardium may be observed.
elastin fibers. Marked lymphatic dilation and accumula-
Diagnosis tion of edema within the endocardium are other fea-
tures of the disease and may occur secondary to impaired
Myocarditis is an uncommon cause of myocardial
disease in the cat. Diagnosis would depend on consider- cardiac lymphatic drainage. The end result is left or
ation of a number of factors, including history, physical biventricular heart failure, which develops secondary to
examination, and—importantly—echocardiogram to myocardial failure and ventricular dilation. Pulmonary
look for alterations in echogenicity, ventricular mor- edema and pleural effusion may be observed. When the
phology, and cardiac function. Serum cardiac troponin right ventricular endocardium is involved, hepatic con-
-I concentrations would be expected to be high, based gestion and ascites may develop.
on human, equine, and canine myocarditis (see Chapter
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nosis that is confirmed only at time of death with a Detailed comparative pathologic studies have been
necropsy. done in a colony of Burmese cats that were bred for this