Page 88 - Feline Cardiology

86 Section C: Congenital Heart Disease

Innocent Murmurs or as a result of medications. Periodic (2 weeks after
Young kittens (<16 weeks) can have “innocent” murmurs. starting medication, 6 weeks, 3 months) renal profiles to
These murmurs are generally soft (≤3/6), are usually monitor BUN, serum creatinine, and serum electrolyte
heard best at the left base of the heart (rib spaces 3–4) levels are also helpful for cats receiving furosemide and
and may increase or decrease in intensity or tone with an angiotensin converting enzyme inhibitor. Owners
the position of the kitten or an increase in heart rate. should be instructed to watch for the development of
depression, anorexia, or vomiting, which may suggest
Congenital Heart Disease tive of a congenital heart malformation, and additional heart failure.
The presence of loud heart murmurs or heart
complications with the medications or progression of
murmurs that persist beyond 16 weeks of age is sugges-
Once a diagnosis is made, echocardiography is usually
diagnostic tests are recommended to identify the cause
necessary only annually or if the patient’s clinical status
of the heart murmur and the severity of the defect if one
changes dramatically and there is concern for the status
is present. Although information about the presence or
of myocardial function or development of an embolus.
absence of congestive heart failure can be obtained from
thoracic radiographs, echocardiography is typically
needed to identify the actual defect. Circulating bio- ATRIOVENTRICULAR VALVE MALFORMATIONS:
markers may help in this respect: a series of 10 cats with TRICUSPID VALVE MALFORMATION
congenital heart malformations uniformly had elevated Characteristics of tricuspid valve malformation include
plasma NT-proBNP levels compared to healthy controls a spectrum of tricuspid valve abnormalities made up of
(Ettinger 2010). If an arrhythmia is present, an electro- focal or diffuse thickening of the valve leaflets, underde-
cardiogram is indicated to determine the type of velopment of the chordae tendinae and papillary
arrhythmia.
muscles, incomplete separation of the valve components
from the ventricular wall, and focal agenesis of the valve
COMPLICATIONS AND MONITORING tissue (Liu and Tilley 1976).
Some patients can remain asymptomatic and live com- Tricuspid valve dysplasia (TVD) has been recognized
fortably for years with their particular malformation. in cats both as a primary abnormality and commonly in
However, the outcome of many malformations is the coexistance with mitral valve dysplasia or ventricular
development of left and/or right heart failure (e.g., pul- septal defects in the cat (Liu 1977; Chetboul et al. 2004)
monary edema, pleural effusion, or both). Pulmonic stenosis, aortic stenosis, and endocardial
Once the initial diagnosis is made, the best method cushion defect have also been noted in some affected
for long-term monitoring of these patients with cardiac cats (Liu 1977; Kornreich and Moïse 1997; Chetboul
malformations should be carefully considered. Repeated et al. 2004).
visits to the veterinary clinic likely result in more stress
for the cat with cardiac disease (as well as the owner); Etiology, Pathophysiology, and
therefore, it is useful to limit repeated visits to when they Gross Pathology
are most needed. Some follow-up can be done with Etiology
simple phone communication with an owner regarding The etiology of tricuspid valve dysplasia is unknown.
the cat’s behavior at home and the owner’s records of Although there is no conclusive evidence that it is famil-
the at-rest respiratory rate. Owners may be instructed to ial, a retrospective study identified that tricuspid valve
monitor the respiratory rate at home once a day when malformations occurred significantly more frequently
the cat is in a resting state. Most resting cats have a in European short-haired cats (odds ratio = 11.37) and
respiratory rate well below 20 breaths/minute. An Chartreux cats (odds ratio = 27.24) compared to the
increase in respiratory rate may be a sign of the develop- general feline hospital population (Chetboul et al. 2004).
ment of or recurrence of pulmonary edema or pleural
effusion and may indicate the need for thoracic radio- Pathophysiology
graphs or an alteration in dosage of medication. The malformation results primarily in tricuspid valve
Some aspects of cardiac disease do require at least a regurgitation, which leads to right atrial and right ven-
brief visit to the hospital for monitoring even in the tricular dilation. Right-sided heart failure (e.g., pleural
absence of overt clinical signs. Cats with tachyarrhyth- effusion) may develop secondary to the dilated right
mias may require physical examination or an electrocar- atrium and elevated right atrial pressure. Supraven-
diogram to be sure that the heart rate is well controlled. tricular arrhythmias may develop and thromboemboli
Blood pressure monitoring may be helpful to make sure may form in the right atrium secondary to the atrial
that the patient is not hypotensive, either spontaneously dilation.