Focus on … high blood pressure

Just like us, our feline friends can suffer from high blood pressure (also known as hypertension) and this can lead to a number of different issues with their general health.  High blood pressure in cats often occurs secondary to other diseases – kidney disease and an overactive thyroid gland are the most commonly linked to hypertension – although it can occur without any concurrent disease (primary hypertension).

Cats’ normal blood pressure ranges from 120 – 160mmHg and in general if your cat’s blood pressure is consistently over 180mmHg it is likely to start causing harm to their internal organs.

The most commonly affected organs are the eyes – high blood pressure can cause bleeding into the eyes and can lead to the eyes becoming swollen and, in some cases, the retina at the back of the eye detaching. This will lead to blindness and is often the first thing an owner of a cat with high blood pressure will notice. 

Other organs that can be affected include the heart – over time parts of the heart’s chambers become thickened and this can reduce how effectively the heart can pump blood around the body and in some cases, this can lead to heart failure.

The brain and the nervous system can also be affected; and cats may behave oddly, become wobbly when moving around and may also have seizures.  The function of the kidneys and blood pressure are intrinsically linked.  If kidney disease is already present, as is the case in many cats with high blood pressure, the disease is likely to deteriorate quicker if the blood pressure is left untreated.  In cats without kidney disease, hypertension is likely to put pressure on the kidneys and increase the chances of disease.

Quite often high blood pressure will go undetected until it is quite advanced. As mentioned above, the most common symptoms relate to the eye and often the first thing an owner will notice is that their cat has gone blind.  Often if other disease is present alongside high blood pressure, the symptoms of these can be present and are noticed first.  These include, for example, weigh loss despite an increase in appetite in cats with an overactive thyroid, or an increase in thirst and urination in cats with kidney disease.  More generally, cats may be quiet and less active, and they might seem depressed.  In people, it is known to cause quite bad headaches and it is likely that cats may suffer the same.

Vets will diagnose high blood pressure in a similar way to how it is measured and monitored in people. The equipment used involves placing an inflatable cuff around the cat’s leg (or sometimes, its tail) and is generally very well tolerated by feline patients. Vets will take a number of readings to ensure the blood pressure that they get is correct – in some cases, they may do several readings throughout the day.

The reason for this is cats can get stressed going to the vets, and this can increase the blood pressure falsely.  By repeating measurements, the vets can be certain the level they have is accurate and not influenced by what is called the ‘white coat effect’.

Treatment for high blood pressure involves giving medication in tablet form – the most common of which is called amlodipine.  It would also involve treating any underlying disease such as kidney disease or an overactive thyroid.

Because high blood pressure can go unnoticed until it is fairly advanced, and the effects it can have can be quite wide ranging, you r vet may recommend that cats over seven years of age have regular blood pressure checks – generally once or twice a year, although they may recommend more frequent checks in cats with underlying disease such as kidney disease.  If you think that your cat could be suffering from high blood pressure, or any of the related diseases, we could recommend getting your checked over by your vet.

Dr Alison Richards, BVSc MRCVS       

This article first appeared in the Winter 2018 issue of The Cat magazine.  My thanks to Editor, Francesca Watson for her kind permission in allowing me to publish it on the TDM website.

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