High Blood Pressure in Cats: A Silent Danger in Old Age

High blood pressure in cats is one of those problems I never thought about until Biscuit's kidney disease put it on the table. At one of her rechecks, the vet wrapped a tiny cuff around her front leg, and I learned that hypertension is not just a human worry. In cats it is common in old age, it usually rides on the back of another illness, and it is dangerous for a reason that took me by surprise: the first sign an owner tends to notice is a cat who has suddenly gone blind. The same pressure can also inflame the eye, and high blood pressure is one of the causes of uveitis.

This explains what feline hypertension is, why it so often travels with kidney disease and thyroid trouble, and how it is caught and managed. Whether your own cat has it is a question for your vet and a blood pressure reading, not something you can judge from the outside.

What is high blood pressure in a cat?

Blood pressure is the force of blood pushing against the vessel walls, and when it stays too high, it slowly damages the organs those vessels feed. Cornell describes hypertension, or persistent elevation in blood pressure, as a relatively common and potentially serious threat to feline health. The numbers put it in focus. VCA defines systemic hypertension as high blood pressure throughout the body: a sustained elevation in systolic pressure of 140mmHg or greater, in diastolic pressure of 90mmHg or greater, or both. What makes it dangerous is its quiet. A cat can carry high blood pressure for a long time with nothing to show for it, until the pressure has already done real harm.

Why it usually comes from another disease

In people, high blood pressure is often its own condition. In cats, it is usually a passenger on something else. Cornell notes that secondary hypertension, which is related to an underlying systemic disease process, is the most common form. Two familiar diseases of old age drive most of it. The first is kidney disease: Cornell reports that at least 60% of cats diagnosed with hypertension also have signs of CKD. The second is an overactive thyroid, since about 20% of cats diagnosed with hyperthyroidism, another common disease of older felines, are diagnosed with hypertension as well. This is why the two conditions at the center of so many senior cats' lives, chronic kidney disease and hyperthyroidism, come with a blood pressure check attached. VCA rounds out the list of culprits with kidney disease, thyroid disease, diabetes mellitus (less common) and a few rarer causes, which is one more reason a diabetic cat needs a close eye.

The damage it does before you notice

High blood pressure earns its danger by working out of sight, on the organs with the most delicate vessels. The eyes come first. Cornell says ocular problems are the most common target organ injury seen in cats with hypertension, ranging from retinal detachment causing blindness to more subtle signs such as bleeding or swelling in the back of the eye. That is the cruel part: for many families, the first they know of it is a cat bumping into furniture or staring blankly, her sight already gone. The heart is strained too, because with systemic hypertension, the heart has to beat against higher pressure, which can lead to cardiac changes in up to 60% of cats. The kidneys, already often the source of the problem, take further damage from it, and the brain is not spared: Cornell notes neurologic changes can be seen in between 15-40% of cats with hypertension. VCA lists the worst of these plainly, from congestive heart failure and retinal detachment causing acute blindness to stroke.

How high blood pressure is found

Because you cannot see it, the only way to catch hypertension early is to measure it, the same way your own doctor does. Cornell explains that blood pressure is measured in the veterinary clinic or hospital using either a Doppler ultrasound device or an oscillometric device attached to a cuff placed on a cat's front leg or tail. It is quick and does not hurt. What matters most is who should be checked: any older cat with kidney disease or a thyroid problem, and ideally any senior cat as part of a routine check, since a reading now is the only thing that tells you whether the damage is being prevented or is already underway.

How high blood pressure is treated

Once it is found, hypertension is very treatable. Cornell notes that the first-line medication for treating feline hypertension is generally a calcium channel blocker called amlodipine, available as a small pill given once daily. The aim is a specific target: according to VCA, the treatment goal for a cat with hypertension is a systolic pressure of 160mmHg or less. Because the pressure usually rises from an underlying disease, that disease is treated in tandem. As Cornell describes it, treatment generally involves medication and monitoring for the remainder of a cat's life, in conjunction with treatment for any underlying medical conditions such as CKD or hyperthyroidism. A daily pill and regular rechecks are a small price for organs kept safe.

When to see the vet

Any sudden change in your cat's vision is an emergency, not a wait-and-see. A cat whose pupils are widely dilated in normal light, who bumps into things, or who seems abruptly disoriented needs to be seen the same day, because a detached retina caught quickly is sometimes reversible. Short of an emergency, the useful move is preventive: if your senior cat has kidney disease, an overactive thyroid, or has simply never had it done, ask for a blood pressure reading at her next visit. It takes a few minutes and can save her sight.

Biscuit's blood pressure gets checked now at every kidney recheck, the little cuff going on while she grumbles about the indignity of it. I used to think of it as one more thing on an already long list. I think of it differently since I learned what silent damage it heads off, and how much a cat depends on eyes that still work to navigate the small world she has left. That is the whole case for taking high blood pressure in cats seriously: it is quiet, it is common, and it is one of the treatable ones.

Sources

• Cornell Feline Health Center, Hypertension
• VCA Animal Hospitals, Systemic Hypertension (High Blood Pressure) in Cats