Hypertension (high blood pressure) is a relatively common and potentially severe threat to feline health. The condition can be dangerous in itself, responsible for a variety of disorders adversely affecting, for example, a cat’s eyesight, kidney activity, or cardiac function. It can also indicate the presence of a potentially deadly underlying systemic disease. Fortunately, with timely and appropriate veterinary monitoring and treatment, feline hypertension—whatever its cause—is almost always manageable.
Blood pressure is measured in cats by the same method that is used for humans. That is, two values are taken into account, the higher one being the blood pressure in the arteries that is recorded when the heart beats (systolic pressure), the lower value when the heart rests between beats (diastolic pressure). In cats, as in humans, these two values are recorded one above the other, separated by a slash mark. Normal human blood pressure is 120/80 mmHg (which stands for millimeters of mercury), while in cats, normal blood pressure is typically higher than that.
“In general,” says Richard Goldstein, DVM, an associate professor of small animal medicine at Cornell University’s College of Veterinary Medicine, “we like to see a cat’s systolic pressure below 160” Although cats are likely to be excited and “never really normal” when they are having their blood pressure measured in a veterinary clinic, Dr. Goldstein notes, “anything above that can be worrisome.”
In rare cases, a cat’s elevated blood pressure has no discernible cause. This is known as primary—or “essential”—hypertension. Although primary hypertension is commonly diagnosed in humans, it is relatively rare in cats. On the other hand, veterinarians frequently diagnose “secondary” hypertension, which is a consequence of an underlying primary disease. Occasionally, the condition can stem from the presence of a heart ailment or a tumor that is producing excessive amounts of corticosteroids or of certain hormones, such as epinephrine. It is also possible for some medications to cause a temporary rise in a cat’s blood pressure. But in the great majority of cases, secondary feline hypertension is a consequence of kidney disease or, less often, hyperthyroidism or diabetes. There is no recognized predisposal for feline hypertension in terms of gender or breed, but an animal’s age does seem to be relevant. That is, the risk for hypertension rises as a cat grows older.
Cats with advanced secondary hypertension will typically exhibit problems associated with the systems that are affected by the condition: the ocular system (sudden blindness or retinal hemorrhaging); the renal system (poor appetite, weight loss, increased drinking and urination); the neurologic system (seizures, disorientation); and the cardiovascular system (difficulty in breathing).
Dr. Goldstein advises cat owners to have their animals undergo frequent veterinary evaluations that include blood pressure measurement so that problems such as kidney disease and hyperthyroidism can be identified early and appropriate therapy can be initiated. When a cat is diagnosed with hypertension, thorough bloodwork will be done in an effort to identify the cause. Treatment for the condition currently centers on two types of medications: calcium channel blockers (such as amlodipine) and angiotensin-converting enzyme (ACE) inhibitors (such as benazepril), both of which work by relaxing and dilating an animal’s blood vessels. With these medications, feline hypertension is frequently controllable and even reversible, especially when the underlying disease is successfully treated.