Hypertension (high blood pressure)
What is hypertension?
Hypertension (high blood pressure) is common in older cats and dogs. It can be caused by several underlying conditions but can also occur on its own. If left untreated, chronic hypertension causes damage around the body, known as target organ damage. This includes, but isn’t limited to, the eyes, kidneys, heart and central nervous system.
Hypertension alone can occur completely without symptoms. If symptoms are shown, they are more likely due to an underlying condition, such as kidney disease, hyperthyroidism, or heart disease. Depending on the cause, symptoms may include increased thirst, weight loss, vomiting or weakness. Investigation of these symptoms will lead to a diagnosis and alert us that the patient is at risk of hypertension.
For some patients, the first sign of hypertension is damage to the target organs. This can include vision changes or blindness, neurological signs (such as confusion or seizures) or heart problems (such as trouble breathing or collapse).
Since hypertension often has no primary symptoms, regular blood pressure checks are recommended in older animals to prevent secondary damage occurring. Yearly checks are advised from 7 years old in both cats and dogs.
Blood pressure can be measured quickly and easily in a conscious patient, if they are cooperative. A cuff is placed around the limb or tail, and a small probe is used to listen to the pulse below this. The cuff is gently inflated to block the blood vessel, then gradually deflated to allow blood flow to return. By watching the pressure gauge and listening to when the pulse becomes audible again, systolic blood pressure can be assessed. An average of five readings is recommended.
A blood pressure of over 140mmHg is considered high, with values over 180mmHg considered severe. Blood pressure is measured in millimetres of mercury, written as mmHg.
Like in people, our pets’ blood pressure will increase due to stress. Recording blood pressure before doing other procedures (such as blood samples) can help, as can having you present with your pet. Sometimes your pet may be admitted, so they can settle in for an hour or so and get used to the environment. If “white coat syndrome” is suspected, blood pressure checks should be repeated 1-2 weeks later. Most pets do not have persistently high blood pressure due to fear, and if readings remain consistently high, they are likely true.
If hypertension is found on a routine check, investigations such as blood tests and urine analysis may be recommended to check for underlying conditions.
If hypertension is due to an underlying condition, this will be treated primarily. This alone may resolve your pets’ high blood pressure. If hypertension is severe, antihypertensive treatment will be started straight away to prevent secondary target organ damage.
If no underlying disease is identified, or treatment of the underlying disease doesn’t resolve your pet’s high blood pressure, antihypertensive medications will be recommended. Treatment is using tablets, given once or twice daily. Blood pressure will need regular monitoring and checks are advisable 7-14 days after dose changes, to ensure blood pressure doesn’t drop too low. Once your pet is stable, frequency can reduce.
The prognosis for animals with hypertension is fairly good. Hypertension itself can usually be managed well with medication, though treatment is life-long and early diagnosis can prevent secondary damage occurring. Due to the high likelihood that hypertension is due to other disease processes, the prognosis for this must also be considered.