Page 148 - Problem-Based Feline Medicine

140 PART 3 CAT WITH SIGNS OF HEART DISEASE

Vomiting, lethargy, anorexia and syncope are seen in Blood examination and serologic findings
symptomatic cases. Microfilaremia is rare in cats and transient (possibly
about 1 month). If present, the number of microfilaria
Respiratory signs such as cough or dyspnea are common.
is small.
Respiratory signs may be quite similar to feline
Serologic testing should include both an antibody and
chronic bronchitis or asthma.
antigen test.
Some cats can present for evaluation of pneumotho-
A positive antibody test is consistent with exposure
rax/chylothorax.
with or without current infestation. It is a useful screen-
Occasionally aberrant larval migration results in neuro- ing test and cats with a positive test should be followed
logical signs such as seizures, collapse, blindness and up with antigen test.
vestibular signs.
A positive antigen test may be consistent with cur-
See main reference page 104 (The Coughing Cat). rent infestation. The sensitivity of the current antigen
tests is considerably less than the antibody test.
Diagnosis
Combining results from serum Ab and Ag tests
Radiographic findings achieves higher sensitivities than using serum Ab and
Ag test results alone.
Enlarged and tortuous caudal pulmonary arteries
are visible on both projections of the chest, but espe- Negative serologic findings do not absolutely rule out
cially the DV/VD views. heartworm infestation. If clinical signs are compatible,
repeat Ab and Ag testing by a different method, evalu-
Diffuse pulmonary infiltrates characterized by a
ate chest radiographs and consider echocardio-
mixed interstitial and peribronchial pattern.
graphic examination.
Electrocardiographic findings
The ECG is generally not useful in diagnosis of feline Treatment
heartworm disease.
Adulticide treatment is not usually recommended in
Sinus tachycardia (HR > 220 bpm) cats because of severe side effects. Infestation is
small (1–2 worms) and their lifespan is short (average
Right heart enlargement in advanced cases. The MEA
2 years).
is usually beyond +180 degrees clockwise.
Surgical removal of the worms through a jugular
Echocardiographic findings approach can be attempted in severe cases.
Main pulmonary artery may be normal or enlarged.
Medical treatment is mainly symptomatic.
Linear parallel densities may present in the main pul-
monary artery or the main branches.
VENTRICULAR SEPTAL DEFECT*
Dilatation of the right ventricle is seen in advanced
cases; RV internal dimension in diastole > 6 mm.
Classical signs
Echocardiography has high specificity for the diagno-
● Systolic murmur loudest over the right
sis of feline heartworm disease, but sensitivity is highly
sternal border.
dependent on the experience of the ultrasonographer.
Cardiac catheterization findings
Pathogenesis
Non-selective angiography may show:
● Linear filling defects within the pulmonary arterial tree. The shunting of blood depends on the size of the defect
● Dilated and tortuous pulmonary arteries. and the relative resistance of the systemic and pul-
● Dilated right ventricle. monary circulations.