Page 302 - Clinical Small Animal Internal Medicine

270 Section 3 Cardiovascular Disease

whether RCM is a separate form of cardiomyopathy or an HCM, RCM, and UCM requires a high level of echocar-
VetBooks.ir advanced stage variant of HCM. diographic skill and experience. A precise diagnosis can
be challenging even for experienced cardiologists unless
Signalment a cat has a classic HCM or ARVC phenotype, due to poor
consensus on the definitions of each cardiomyopathy
type. Moreover, the labels “end‐stage HCM,” “RCM,” and
There is a male predominance in cats with HCM. Most “UCM” might not actually reflect distinct disease entities
cats with HCM are domestic nonpedigree cats, but a num- but rather different stages of a single condition. Instead,
ber of pedigree breeds are said to be predisposed, including diagnostic tests should be focused on confirming the
the Maine Coon, ragdoll, Persian, British shorthair, sphynx, presence of heart disease; identifying any underlying
Cornish rex, and Norwegian forest cat. Siamese and systemic cause of cardiomyopathy that should be treated;
Oriental cats may be predisposed towards eRCM. Age at and identifying cats at high risk of CHF and ATE.
diagnosis varies widely, as any age of cat can be affected
with HCM, including kittens and geriatric cats, but the
prevalence of LV hypertrophy increases with age. Is Heart Disease Present?
In practical terms, the clinician’s first priority when pre-
sented with a cat with clinical findings suggestive of heart
History and Clinical Signs disease is to establish whether or not cardiac disease is
present. The approach will be different for cats with
Cats with advanced myocardial disease are often perceived respiratory distress versus those that are asymptomatic.
by their owner to be healthy until shortly before the onset
of CHF, ATE, syncope or sudden death. Typical presenting Tachypneic Cats
signs for CHF include respiratory distress and tachypnea, Heart disease should always be considered in cats with
whereas acute limb paralysis/paresis is the most common tachypnea, and the presence of a murmur, gallop or
presentation with ATE. Some cats may develop open‐ arrhythmia should increase this suspicion (Figure 27.2).
mouth breathing only with stress or exertion, and may be Differentiation of congestive heart failure from other
found to have dynamic LV outflow tract obstruction. causes of respiratory distress may require diagnostic
Physical examination findings are varied. Murmurs are imaging, but the potential value of radiography or echo-
common in cats with HCM but also in healthy cats with cardiography must be weighed against the possible risk
normal hearts, so a murmur should not always be of subjecting the patient to further stress that could
assumed to indicate heart disease. Murmurs are less prove fatal. Ultrasound is generally better tolerated than
common in the more severe forms of cardiomyopathy radiography, and has the advantage that patient posi-
than in well‐compensated HCM. A minority of cats with tioning is less critical. Thoracic ultrasound can demon-
cardiomyopathy have an audible gallop or arrhythmia, strate pleural effusion and can even be used to indicate
and these auscultation findings are more likely to indi- pulmonary parenchymal changes as with pulmonary
cate advanced disease, though can also be detected in edema (B‐line artifacts). If sufficient expertise is availa-
some geriatric cats with only mild abnormalities. ble, the most useful way to increase confidence of a car-
A prominent apical impulse may be apparent in cats with diac cause of respiratory distress is to demonstrate LA
cardiomegaly or a hyperdynamic LV. enlargement with echocardiography. Thoracic radiogra-
Physical exam findings in cats with congestive heart phy can be used to identify pleural effusion, pulmonary
failure will include tachypnea with increased respiratory infiltrates, and assess cardiac size, but must be obtained
effort, crackles on pulmonary auscultation with severe with great care to avoid compromising patient safety. A
pulmonary edema, or absent breath sounds ventrally point‐of‐care test is available to measure plasma NT‐
with a pleural effusion. The presence of a gallop sound in proBNP, providing a simple way to help differentiate
a cat with tachypnea and respiratory distress should cats with respiratory distress due to heart failure versus
prompt treatment for congestive heart failure until fur- noncardiac causes.
ther confirmatory tests are possible.
Asymptomatic Cats
Myocardial disease should be considered in an otherwise
Diagnosis healthy cat when a murmur is detected, and should be
strongly suspected when a gallop or arrhythmia is aus-
From the above descriptions, it is clear that establishing cultated (Figure 27.3). A very loud murmur (i.e., with a
a diagnosis of a particular type of cardiomyopathy in an precordial thrill) is usually associated with congenital
individual cat is challenging. To differentiate end‐stage heart disease.