Page 142 - Problem-Based Feline Medicine

134 PART 3 CAT WITH SIGNS OF HEART DISEASE

consistent clinical signs (weight loss, ravenous ● Cats with cardiomyopathy usually do not have
appetite, palpable thyroid nodules, polyuria, poly- weight loss but may show dyspnea secondary to
dipsia). congestive heart failure.
● Chronic renal disease is diagnosed with an increased
Cats with coagulopathy, optic neuritis, systemic
urea of greater than 11.6 mmol/L (32.5 mg/dl),
infectious disease and neoplasia may have similar
increased creatinine greater than 163 μmol/L (1.84
ocular signs (retinal hemorrhages, hyphema and
mg/dl) with a decreased urine specific gravity less
detached retinas) as hypertensive cats.
than 1.035.
Documentation of hypertension is needed to help dif-
ferentiate these diseases from hypertensive cats.
Radiographic findings
Cerebrovascular accidents in cats with hypertension are
Heart size varies from normal to marked generalized rare.
cardiomegaly.
Cats with cerebrovascular accidents are usually sec-
Enlarged aortic arch is seen in chronic cases. ondary to an underlying neurological disease.
Undulation of the caudal aorta is suggestive of hyper-
Treatment
tension.
Beta-blockers – refer to page 306 on hyperthyroidism.
Electrocardiographic findings
Amlodipine is the drug of choice if the etiology is
Tachycardia with a heart rate greater than 220 bpm is CRF or unknown. The dose is 0.625 mg (cat < 5 kg)
usually present with hyperthyroidism. to 1.25 mg (cat ≥ 5 kg) orally once a day for hyper-
Electrocardiogram is usually normal but evidence of tension caused by diseases other than hyperthy-
left ventricular hypertrophy (R wave > 9 mm on lead II) roidism.
may be seen. ACE inhibitors (Enalapril or Benazepril) can be used
as adjuvant therapy.
Echocardiographic findings
● ACE inhibitors can be used carefully in cases with
Mild to moderate left ventricular hypertrophy may concurrent chronic renal failure. Close follow-up of
be seen. Left atrial size is usually normal. renal function is mandatory.

Transmitral inflow velocity Doppler profile may show ● If serum creatinine is higher than 265 μmol/L (3.0
evidence of impaired relaxation (small E and tall A mg/dl) at baseline, ACE inhibitors should not be used.
wave). ● Start at 0.25–0.5 mg/kg once a day for Benazepril
OR Enalapril.
Enlarged aortic arch equal or greater than 11 mm is ● Obtain baseline renal values and recheck at 5 and
seen in chronic cases. 10 days after starting medications.
For findings in hyperthyroidism see page 132 In refractory cases, multiple drug therapy may be required
(Hyperthyroid heart disease). (amlodipine, beta-blockers, diuretics, ACE inhibitors).

Low-salt diets may be used in refractory cases.
Differential diagnosis
The goal of therapy is to decrease systolic blood pres-
Cats with either hypertension or cardiomyopathy com- sure to 140–160 mmHg.
monly have murmurs. ● Drugs should be titrated to effect.
● However, cats with hypertension most commonly
present with ocular signs. Prognosis
● Most hypertensive cats have polyuria, polydipsia or
weight loss consistent with chronic renal disease or Hypertension caused by hyperthyroidism is usually
hyperthyroidism. reversible with normalization of the serum thyroid levels.