Page 119 - Feline Cardiology

118 Section D: Cardiomyopathies

purebred families as well as in the general feline popula- sudden cardiac death may be the first clinical complaint
tion in an echocardiographic screening study (Wagner in some cats with severe disease that were never
et al. 2010; Ferasin et al. 2003; Rush et al. 2002; Atkins previously clinically detected and are diagnosed with
et al. 1992). Despite several purebred predilections for HCM on necropsy. The diagnosis of HCM in these
HCM, the most common type of cat diagnosed is the sudden-death cases may occur at any age, but appears
domestic shorthair cat (42–65% of cases), followed by more common in the younger cat (<5 years of age).
the domestic longhair cat (22–42%) (Ferasin et al. 2003; Respiratory difficulty due to congestive heart failure
Rush et al. 2002; Atkins et al. 1992). Of purebred cats, is the most common presenting clinical complaint,
the Persian is the most common breed (3–15% of cats occurring in 32–46% of cats diagnosed with HCM
with HCM), followed by Himalayan, Maine coon, (Rush et al. 2002; Atkins et al. 1992). A precipitating
Cardiomyopathies 2002; Atkins et al. 1992). Other predisposed breeds nosed with CHF in one study (Rush et al. 2002). The
event was identified in approximately half of cats diag-
Ragdoll, and Birman (Ferasin et al. 2003; Rush et al.
most common precipitating event was fluid administra-
include the American shorthair cat, British shorthair cat,
tion (28%), followed by anesthesia/surgery (25%), and
Sphynx, Bengal, Siberian, and Scottish fold. Cats with
HCM were found to have a larger body somatotype (i.e.,
recent corticosteroid administration (21%) with meth-
larger vertebrae, longer radial bone length, larger skull
amcinolone (30% of cats) given 1–2 weeks prior to
size) than control cats; however there is not one patho- ylprednisolone (70% of cats) or injectable form of tri-
gnomic characteristic that distinguishes an abnormal diagnosis of heart failure (Rush et al. 2002). Ketamine
somatotype from normal. Although cats with HCM had was the most common anesthetic administered (89%)
larger somatotype, there was no difference in serum in anesthetized cats that developed CHF, which may be
insulin growth factor-I between normal cats and cats explained by the popularity of ketamine in feline prac-
with HCM, making acromegaly an unlikely link (Yang tices, the potential for adverse cardiac effects of ket-
et al. 2008). One potential explanation for a larger amine in cats with HCM, or a combination of both
somatotype in cats with HCM is the high representation factors. Typical presenting complaints of cats with heart
of Maine coon cats and Maine coon cross cats in the failure include respiratory difficulty, lethargy, anorexia,
feline population, and these cats require only one copy vomiting, or weight loss. Often, owners may confuse
of the MYBPC3 mutation to develop HCM. There is no vomiting with coughing or wheezing, particularly if a
known link between HCM and other physical traits or coughing fit ends with a terminal retch that produces
concurrent heritable defects in cats. mucus or a hairball. It is important when a client
describes vomiting or hairballs in a cat with pulmonary,
airway, pleural, or cardiac disease that the clinician
HISTORY AND CHIEF COMPLAINT
inquire about the connection between coughing and
vomiting. If the vomiting/hairball evacuation occurs
• Approximately half of cats with HCM are diagnosed only at the end of coughing fits, a gastrointestinal disor-
incidentally and are asymptomatic. The most common
reason asymptomatic cats are clinically evaluated for der may not be the patient’s dominant concern, even
cardiac disease is the presence of a heart murmur or though it can be the most noticeable, and therefore wor-
gallop heart sound on routine physical examination. risome, abnormality in the eyes of the owner. Syncope
• Approximately half of cats diagnosed with heart failure is an uncommon presenting complaint (occurring in 10
secondary to HCM had an identifiable precipitating of 260 cats, 4%), and it may occur secondary to an
event; the most common include fluid administration, arrhythmia, severe CHF, or an intracardiac thrombus
anesthesia and surgery, and corticosteroid (Rush et al. 2002). Lameness, paresis, and pain may be
(methylprednisolone) administration. chief complaints in cats affected with arterial thrombo-
embolism (ATE) secondary to HCM, which occurs in
A large number of cats (at least 33–55%) diagnosed with 12–17% of cats diagnosed with HCM (Rush et al. 2002;
HCM are asymptomatic and have no abnormal history or Atkins et al. 1992). Therefore, part of the history should
chief complaint (Rush et al. 2002; Atkins et al. 1992). By involve specific inquiries regarding prior acute onset of
far the most common clinical context for incidental dis- lameness, which may have been transient, or much less
covery of HCM in cats is during routine examination for commonly acute changes in mentation or gastrointesti-
other purposes (annual health exam, or medical concern nal signs in cats suffering from embolization of the brain
not related to the heart), in which a heart murmur or or gastrointestinal tract, respectively. Age, breed, and sex
gallop heart sound is noted (see Chapter 1). Alternatively, were not significantly different among cats that were
HCM is sometimes first suspected during diagnostic asymptomatic, or had CHF or ATE in the largest study
imaging for other purposes such as the incidental detec- that compared these variables (Rush et al. 2002). Other
tion of cardiomegaly on thoracic radiographs. Finally, basic inquiries during the history-taking process should