Hypertension is the medical term for high blood pressure, which has recently beenrecognised as an important condition in cats. Both primary (‘essential’) and secondary hypertension are seen in cats, as in people. With primary hypertension, the disease occurs independently but, in secondary hypertension, the high blood pressure is due to another underlying disease. The most common causes of secondary hypertension in cats are chronic kidney failure and hyperthyroidism (an overactive thyroid gland).
Effects of hypertension
Hypertension is damaging to the body, but the effects are most serious in certain vulnerable organs, namely:
• the eyes (where it can cause bleeding, visual impairment and even full blindness);
• the brain and nervous system (where it can cause spontaneous bleeding and neurological disturbances);
• the heart (where over time it can cause thickening of the wall of the heart and compromise heart function);
• the kidneys (where it may increase the risk of kidney failure developing, or result in significant worsening of existing kidney
Because hypertension is often an effect of other diseases, cats with high blood pressure may simply show signs attributable to their underlying problem. In many patients, no specific signs of hypertension will be seen until the condition advances to the point where there is spontaneous bleeding into the eye or retinal detachment - these cats often develop noticeable ocular abnormalities or sudden blindness. However, early recognition of hypertension to avoid these severe and often permanently damaging effects is obviously desirable. Some cats with hypertension do appear depressed, lethargic and withdrawn. Although these signs may be subtle, many owners notice an improvement in their cat’s behaviour once hypertension has been managed successfully.
Hypertension should be suspected as a possibility in any cat with chronic renal failure, hyperthyroidism or heart disease. In addition, it
is important to consider hypertension in any cat that develops sudden-onset blindness or other ocular signs consistent with hypertension.
Older cats are more likely to develop hypertension, and it is desirable, therefore, to include blood pressure assessment in the routine clinical examination of these cats.
Diagnosis of hypertension is made by measurement of blood pressure, and equipment is available to do this simply and easily, using techniques very similar to those used in human medicine. Measuring blood pressure only takes a few minutes, is completely pain-free and is extremely well tolerated by most cats. A detailed eye examination is also essential because ocular disease is common in hypertensive cats.
Management of hypertensive cats
Management of hypertension has two broad aims: reducing the blood pressure using antihypertensive drugs (this is usually very successful in cats, and most cats just have to be treated once daily), and searching for an underlying disease (such as kidney failure) that has caused the hypertension. There is considerable individual variation in response to anti-hypertensive therapy and careful monitoring of blood pressure and ocular abnormalities is required (along with monitoring any underlying disease) to ensure optimum therapy.
In primary hypertension (where no underlying disease is present) it is usually possible to manage the hypertension and prevent future complications such as damage to the eyes. In cases of secondary hypertension, the longterm outlook is dependent on the nature and severity of the disease that has caused the high blood pressure. Although the hypertension can usually be managed, the underlying disease is not always curable (as in cases of kidney failure). Even in cats where blindness has occurred as an effect of their hypertension, control of the blood pressure is still extremely important. In most affected cats a good quality of life can be restored andfurther damage halted through appropriate therapy.
Information taken from: http://www.aht.org.uk/pdf/feline_hypertension.pdf
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