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Systemic Hypertension in Cats: Fundic Changes & Potential for Early Intervention

Alison Clode, DVM, DACVO, Port City Veterinary Referral Hospital, Portsmouth, New Hampshire


November/December 2021

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In the Literature

Cirla A, Drigo M, Andreani V, Barsotti G. Ocular fundus abnormalities in cats affected by systemic hypertension: prevalence, characterization, and outcome of treatment. Vet Ophthalmol. 2021;24(2):185-194.


This study presented a prospective evaluation of ocular fundus changes in 225 cats diagnosed with systemic hypertension (SHP), defined as systolic blood pressure (BP) >160 mm Hg and diastolic BP >100 mm Hg. Ophthalmic examinations were performed on cats with fundic abnormalities from days 7 to 365 postdiagnosis. Amlodipine besylate (0.625-1.25 mg/cat PO once daily) was administered as antihypertensive therapy. 

A grading scale was used to characterize the severity of ocular fundus lesions. Grade 0 indicated no abnormalities. Grades 1 to 3 involved progressively increasing retinal vascular changes (ie, tortuosity, narrowing) with increasing degrees of retinal and vitreal hemorrhage and subretinal exudation. Grade 4 included the grade 1 to 3 abnormalities as well as the subtotal or total retinal detachment. 

Of the 225 cats, 93 (41.4%) had no observed abnormalities on fundic examination at the time of SHP diagnosis. Of the 132 cats with abnormalities, 28 (21.2%) were grade 1, 24 (18.2%) were grade 2, 48 (36.4%) were grade 3, and 32 (24.2%) were grade 4. Although no visible ophthalmoscopic abnormalities were present on examination of grade 0 cats, a computer imaging software program used in 35 cats confirmed presence of early vascular changes indicative of hypertensive target organ damage. A positive correlation was present in all cats between systolic BP values and severity of fundic examination abnormalities.

Following initiation of amlodipine therapy, the average time for improvement was approximately one month, with 91.6% of cats demonstrating significant improvement in one year. Retinal degeneration, however, was present in many cats, with 61 out of 132 showing uncertain or no vision one year after diagnosis.

Associated systemic disease conditions included chronic kidney disease in 136 cats, hyperthyroidism in 65 cats, chronic kidney disease and hyperthyroidism in 17 cats, and hypertrophic cardiomyopathy in 7 cats.


Key pearls to put into practice:


Although most cats with SHP have fundic changes observable on examination alone, all cats typically have subclinical changes to the retinal vasculature indicative of target organ damage. Appropriate and aggressive antihypertensive therapy is necessary to minimize further damage to the eye and other organs (ie, kidney, heart, brain).


The severity of the lesions observed is correlated with the severity of SHP; thus, regular monitoring should include BP evaluation and fundic examinations, as worsening fundic lesions may indicate a poor response to antihypertensive therapy that may not be identified on a single BP reading.


Pet owners should be given an expected time frame for improvement of vision (approximately one month); however, owners should also be advised that retinal degeneration may occur, which might adversely impact long-term visual ability.

For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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