Page 146 - Problem-Based Feline Medicine

138 PART 3 CAT WITH SIGNS OF HEART DISEASE

Diagnosis For hyperthyroid heart disease refer to page 131.

Radiographic findings
Clinical signs
Soft tissue density seen within the cranial mediastinum.
A systolic blowing murmur louder at the heart base is
Elevated trachea.
usually present.
Pleural effusion. A gallop rhythm may be present.
Electrocardiographic findings Sinus tachycardia is usually present, with heart rates
Normal. above 220 bpm.
Displaced and/or muffled heart sounds are heard sec-
Echocardiographic findings ondary to intrathoracic masses displacing the heart. In
Normal cardiac function unless concurrent heart dis- some cases, this finding may be due to the presence of
ease is present. pleural effusion.
A cardiac mass may be seen (rare). Other systemic signs:
● Pale mucus membranes, prolonged capillary refill
Ultrasound of the cranial mediastinum may reveal a
time, petechiae, anorexia, ravenous appetite, weight
mass.
loss and palpable thyroid glands bilaterally.
Pleural effusion may be seen.
Diagnosis

HIGH CARDIAC OUTPUT HEART DISEASE* Anemia is present if the hematocrit is less than 0.24
L/L (PCV = 24%).
Classical signs Secondary cardiac changes are not usually present
● Heart murmur. unless a chronic anemia with a hematocrit less than
● Gallop rhythm. 0.15 L/L (PCV ≤ 15%) is present.
● Tachycardia.
Hyperthyroidism is considered present if total thyrox-
ine is increased and there are consistent clinical signs.
Pathogenesis Refer to page 304 (The Cat With Weight Loss and a Good
Appetite).
High cardiac output heart disease in cats is secondary to
hyperthyroidism or chronic anemia. Radiographic findings
Heart size ranges from normal to severe enlargement.
High cardiac output heart disease is uncommon.
Pulmonary edema may be present in rare cases.
Etiologies of chronic anemia are infectious (feline
leukemia virus, feline immunodeficiency virus), neo- Electrocardiographic findings
plastic (lymphoma, thymoma), and metabolic diseases
Tachycardia (>220 bpm) and increased R wave ampli-
(chronic renal failure). Refer to page 526, (The Anemic
tude in lead II (>0.9 mV).
Cat) for a more detailed description of anemia.
Echocardiographic findings
In chronic anemia, increased cardiac output results
from decreased blood viscosity and systemic arteriolar In anemia, a normal to moderate increase in left ventric-
tone augmenting stroke volume. ular dimension (LVIDd > 18 mm) with hyperkinetic (FS
> 55%) cardiac function is found. Left atrial size is usu-
Anemia causes high cardiac output, which increases
ally normal to mildly increased.
cardiac work and results in congestive heart failure
when a co-existing cardiac disease or a hyperkinetic In rare cases, findings similar to dilated cardiomyopa-
state is present. thy are present.
In chronic anemia, the heart rate may be normal or only Refer to page 132 for echocardiographic findings in
mildly increased. hyperthyroidism.