Page 121 - Problem-Based Feline Medicine

8 – THE CYANOTIC CAT 113

Clinical signs great vessels and an obstruction to pulmonary
blood flow.
Many cats are asymptomatic.
This leads to right-to-left shunting and results in mix-
Sudden death occurs in 30–40% of cats with clinical
ing of unsaturated and saturated blood which is then
signs from dirofilaria.
ejected into the systemic circulation.
Most cats are presented with non-specific signs such as
Tetralogy of Fallot, reversed shunting (R–L), patent duc-
lethargy, anorexia, vomiting, coughing, dyspnea and
tus arteriosus, tricuspid valve atresia, Eisenmenger’s syn-
syncope.
drome, endocardial cushion defect and transposition of
Acute dyspnea may result from acute thromboembolism. the great arteries can all cause cyanosis.
Right-sided heart failure is rare. Clinical signs

Cyanosis in a young cat or kitten frequently is sug-
Diagnosis
gestive of a congenital heart anomaly.
Thoracic radiography may show prominent blunted
They may present with lethargy, exercise intolerance,
or tortuous caudal lobar arteries and right heart enlarge-
syncope and tachypnea.
ment.
Signs of congestive heart failure or abnormal heart
Laboratory tests reveal eosinophilia and a non-
sounds may be present.
regenerative anemia in 33% of cases. Adult antigen
tests detect only about 25% of infected cats because Diagnosis
of low worm numbers. Tests for circulating anti-
body to heartworm are more sensitive, but there are Dorsoventral thoracic radiographs may show
problems with false positives and negatives. enlargement of the right atrium at the 8–11 o’clock
Antibodies may persist for up to 18 months after position, right ventricular enlargement at the 5–9
worms have died, so a positive test does not neces- o’clock position or post-stenotic dilation of the pul-
sarily indicate current infection. monary artery at the 1–2 o’clock position.
Echocardiography may reveal worms in the pul- Lateral thoracic radiographs may show rounding of the
monary artery, right heart or vena cava. cranial border of the heart with increased sternal contact
and elevation of the trachea in the cranial thorax. On both
Non-selective angiography may show linear filling
views the pulmonary vessels may be underperfused.
defects associated with the presence of worms.
Echocardiography is useful for visualizing the abnor-
mal cardiac and vascular shunts. Doppler studies will
CONGENITAL HEART ANOMALY
help to identify the presence and direction of shunts.
Classical signs Hematological examination may indicate a poly-
cythemia with a PCV often in excess of 75%.
● Stunting.
● Cyanosis.
● Signs of congestive heart failure. HEART BASE TUMORS
● Abnormal heart sounds.
Classical signs
See main reference on page 140 for details (The Cat
● Muffled heart sounds.
With Abnormal Heart Sounds and/or an Enlarged Heart).
● Right heart failure.
● Pale mucous membranes.
Pathogenesis
● Weak arterial pulses.
Congenital cardiac anomalies causing cyanosis
result from defects in the partitions of the heart or See main reference on page 137 for details.