What is high blood pressure?
High blood pressure (hypertension) is something that most people associate with humans. It is also described as 'the silent killer' as often high blood pressure may be present for a long time without any symptoms, and the problem may only be discovered when a doctor (or veterinarian) checks the blood pressure.
The heart pumps blood around the body via the arteries. Blood pressure is the force in which the pumping blood is exerted against the walls of these arteries. Think of your arteries as a pipe, in high blood pressure, the blood is pumped through these 'pipes' at a higher pressure than normal.
Most of us have had our blood pressure routinely taken by a doctor, and will be aware that there are two readings. The first number (the highest one) is known as systolic pressure, and is the pressure in the arteries as the heart contracts and sends the blood into the circulation. The second number (the lower one) is known as diastolic pressure and occurs as the heart relaxes and fills with blood.
Primary hypertension (essential hypertension) is extremely rare in cats. Most hypertensive cats have secondary hypertension, which is a result of an underlying disease. Common causes of high blood pressure in cats are hyperthyroidism, Cushing's disease, and kidney disease.
What are the effects of high blood pressure?
Eyes: Swelling and bleeding into the eyes can result in blindness. A detachment of the retina can also occur and cause blindness.
Kidneys: The kidneys act as filters to rid the body of wastes. Over time, high blood pressure can narrow and thicken the blood vessels of the kidneys. The kidneys filter less fluid, and waste builds up in the blood. The kidneys may fail altogether.
Arteries: Over time, the arteries may harden, this, in turn, causes the heart and kidneys to work harder.
Brain: High pressure can cause a break in a weakened blood vessel, which then bleeds in the brain. This can cause seizures, stroke or coma. If a blood clot blocks one of the narrowed arteries, it can also cause a stroke.
Heart: The heart has to pump harder and over time this can cause the heart muscle to become enlarged and thickening of the left ventricle, and increase the risks of developing congestive heart failure.
What are the symptoms of high blood pressure in cats?
As stated above, often there are no signs your cat has hight blood pressure. If your cat is suffering from an underlying condition such as hyperthyroidism, for example, regular blood pressure monitoring should be performed.
- Visual impairment or blindness are usually the first sign of high blood pressure. The pupils are often dilated and fixed.
- Other symptoms may include, lethargy, depression, heart murmur and seizures.
- Symptoms relating to an underlying disease such as hyperthyroidism and kidney disease.
How to test for high blood pressure in cats?
High blood pressure should be suspected in any cat who has a predisposing condition such as kidney disease or hyperthyroidism.
As is used on humans, in cats an inflatable cuff is placed on the cat's front leg or tail. In humans, a stethoscope is also used, this isn't possible in cats and a Doppler or oscillometric device is used instead.
Your veterinarian will also do a complete physical exam to determine how much damage has been done to the organs as a result of this condition. This will involve examining the eyes, the heart, neurological system, and the kidneys.
How is high blood pressure in cats treated?
- Identifying and controlling the underlying disease which is causing high blood pressure such as hyperthyroidism or kidney disease.
- Medication which helps reduce blood pressure, these are usually calcium channel blockers, beta blockers, ACE inhibitors, and diuretics. The calcium channel blocker amlodipine is most often prescribed. Medications won't cure high blood pressure, but will assist in controlling it.
- Your veterinarian may also recommend a low sodium diet.
- Your cat will have to have it's blood pressure regularly monitored by a veterinarian.
If the underlying condition which has caused the high blood pressure can be identified and brought under control some of the damage caused may be reversed. It is possible to cure hyperthyroidism, however, kidney disease is progressive and cannot be cured. However, it can be managed.
Close monitoring is vital, and even when the blood pressure has been stabilised it should be regularly checked. If you notice any changes in your cat seek medical assistance immediately.