Page 91 - Problem-Based Feline Medicine

6 – THE CAT WITH HYDROTHORAX 83

separated from queens at 4–6 weeks of age had monary venous hypertension leads to pleural effu-
0% positive titer, 0% died of FIP. sion. This is suspected, but not proved, in cats.
● The recommendation from this study was to wean
Pleural fluid tends to be a modified transudate or chy-
early and separate kittens from the queen before
lous in nature with congestive heart failure.
the maternal antibodies are lost.
Cardiomyopathies such as hypertrophic, dilated or inter-
Vaccination
mediate forms are most often associated with pleural
● A heat-sensitive modified-live intranasal vac-
effusions. Dilated cardiomyopathy is more often associ-
cine was tested for efficacy. In this study, of 550
ated with pleural effusion than the other forms of car-
cats arriving at shelter, half were vaccinated and
diomyopathy, but it is now a rare disease following
2/254 developed clinical FIP, where 8/246 unvac-
taurine supplementation of commercial pet food.
cinated controls developed FIP. However, an
experimental study using a different challenge Rarely heartworm disease has been associated with
strain to the vaccine strain found no protection pleural effusion.
and antibody-dependent enhancement occurred
resulting in accelerated disease. Clinical signs
Dyspnea varies from mild and associated with
CONGESTIVE HEART FAILURE reduced activity levels and reluctance to play, to
(CARDIOMYOPATHY) acute, fulminant air-starvation with open-mouth breath-
ing and cyanosis.
Classical signs
Abnormal heart sounds (murmurs, gallops, arrhyth-
● Muffled heart and/or lung sounds ventrally. mias) may be present, or may be difficult to assess in
● Exaggerated chest excursions/poor airflow. the distressed patient.
● Orthopnea (positional dyspnea – reluctance
Signs of pleural effusion include increased chest
to lay in lateral recumbency).
excursions with little airflow (can be detected by lis-
● Dyspnea ranging from mild to acute and
tening close to muzzle during breathing).
severe with cyanosis.
● Abnormal heart sounds (murmurs, gallops, The cat may present with signs of aorto-iliac throm-
arrhythmias). boembolism, such as paresis of one or more limb, nail
bed cyanosis, cool anesthetic limb, firm cramping of
See main reference on page 128 for details (The Cat With the gastrocnemius muscle, vocalization and tachypinea
Abnormal Heart Sounds and/or an Enlarged Heart). or dyspnea.

Orthopnea (worsened dyspnea in lateral recumbancy)
or reluctance of the patient to lay in lateral recumbency
Pathogenesis
may be reported.
Mechanism of pleural effusion in cats with congestive
Muffled heart and lung sounds are audible ventrally,
heart failure is currently unknown, but there are two
with harsh breathing sounds dorsally in the standing or
leading theories:
sternal recumbency positions. Dull percussion of the
● Left-sided failure results in pulmonary venous and
chest wall is evident ventrally.
capillary hypertension, which leads to reflex pul-
monary vasoconstriction. The resultant pulmonary The liver may be displaced caudally due to fluid pres-
hypertension leads to right-sided heart failure and sure exerted on the diaphragm.
pleural effusion. Evidence against this theory is that
other signs attributed to right heart failure (right Diagnosis
heart enlargement, hepatic venous distention, etc.)
Typically there are clinical signs of pleural effusion
are rarely found in cats with congestive heart failure
together with abnormal heart sounds.
and pleural effusion.
● The visceral pleural veins in cats drain into the Thoracocentesis is indicated in the dyspneic patient
pulmonary veins (as seen in humans), and pul- with clinical signs of effusion.