Page 141 - Problem-Based Feline Medicine

9 – THE CAT WITH ABNORMAL HEART SOUNDS AND/OR AN ENLARGED HEART 133

If congestive heart failure is present refer to the sec- ● The vascular beds most sensitive to chronic
tion on hypertrophic cardiomyopathy for therapeutic hypertension are the ocular, renal, cerebrovascular
options (page 128). and cardiac vessels.

HYPERTENSIVE HEART DISEASE*** Clinical signs

Classical signs Signs directly related to the systemic hypertension are
not common.
● Heart murmur.
● Gallop rhythm. Ocular changes (retinal hemorrhages, hyphema,
● Tachycardia. arterial tortuosity and retinal detachments) are the
● Blindness due to retinal hemorrhage or most common clinical signs seen in hypertensive cats.
detachment. ● Most cats initially present for blindness secondary
● Hyphema. to retinal detachment and hemorrhages.
● Retinal examinations should be done in all cats
diagnosed with systemic hypertension.
Pathogenesis ● Retinal examination is a good way to evaluate the organ
damage resulting from systemic hypertension.
Hypertension is defined as systemic arterial pressure
higher than 180/100 mmHg (systolic/ diastolic).
Weight loss, polyuria and polydipsia seen in hyper-
Hypertension is most commonly secondary to an tensive cats are secondary to the underlying disease
underlying etiology. (CRF or hyperthyroidism) and are not directly referable
● The two most common causes in cats are hyper- to the hypertension.
thyroidism and chronic renal failure (CRF).
Seizures and syncope are rare neurological abnormal-
● The mechanism for development of hypertension
ities seen in hyertensive cats.
in hyperthyroidism is the increased number and
● They are the results of cerebrovascular accidents
sensitivity of adrenergic receptors coupled with
from the hypertension.
an increase in cardiac output.
● The mechanism for development of hypertension in
CRF is renal hypertension with retention of salt and Diagnosis
activation of the renin-angiotensin aldosterone system.
Retinal vascular changes with evidence of retinal
● The hypertension of hyperthyroidism is
hemorrhage and detached retinas are commonly seen
reversible upon control of the thyroid state while
in hypertensive cats on ocular examination.
the hypertension secondary to CRF requires con-
● Indirect and direct ophthalmoscopy should be done
tinued therapy and monitoring.
on all hypertensive cats.
● There is no correlation between the degree of
● Cats are often presented blind with dilated non-
renal disease and the severity of hypertension.
responsive pupils. Aged cats with a sudden
● Essential hypertension is an exclusion diagnosis
onset of blindness should be evaluated for hyper-
when diagnostic tests failed to identify a specific
tension.
cause.
● Common findings are retinal hemorrhages,
Chronic untreated hypertension has several long- hyphema, retinal edema and partial or complete
term adverse effects. retinal detachments.
The increase in systemic vascular resistance results in Elevated systemic arterial pressure (higher than 180
increased afterload and development of left mmHg systolic pressure) is seen.
ventricular hypertrophy.
Hyperthyroidism or chronic renal disease are com-
Chronic elevation of arterial pressure results in mon underlying etiologies.
dysregulation of endothelial homeostasis leading ● Hyperthyroidism is diagnosed with an increased
to hypertensive vasculopathy. total thyroxine greater than 51 mmol/L (4 μg/dl) and