Hypertension is the medical term for high blood pressure. In cats, hypertension usually develops as a secondary complication to other medical conditions, such as chronic kidney disease and hyperthyroidism (overactive thyroid gland). Less commonly, primary or essential hypertension (hypertension without any underlying disease) may also occur.
Effects of hypertension
Since hypertension is often associated with an underlying medical condition, cats may display clinical signs attributable to their underlying problem, such as increased thirst (chronic kidney disease) or weight loss (hyperthyroidism). In many cats, no specific clinical signs will be seen until the hypertension is quite advanced.
Hypertension typically results in damage to vulnerable organs, such as the eyes, brain and nervous system, heart and kidneys.
- Eyes: Bleeding into the eyes, retinal swelling and detachment, can occur resulting in often permanent blindness.
- Brain and nervous system: Bleeding into the brain or nervous system can result in neurological signs, such as altered behaviour, wobbly gait, head tilt, seizures, or even coma.
- Heart: Over time, the muscle of one of the heart chambers (the left ventricle) becomes thickened, which may in severe cases lead to the development of congestive heart failure. Affected cats may show signs of laboured breathing and lethargy.
- Kidneys: Over time, high blood pressure damages the filtering mechanism within the kidney and may increase the risk of developing kidney failure.
Early recognition and treatment of hypertension is therefore important in order to minimise the severe and often permanently damaging effects of persistently high blood pressure.
Diagnosis of hypertension is made following measurement of blood pressure. The equipment used is similar to that used in people, with an inflatable cuff placed around one of the front legs or tail. Measuring blood pressure only takes a few minutes and is extremely well tolerated by most cats. A detailed eye examination is also essential since changes within the eye are common in hypertensive cats. Routine blood and urine tests are often performed to search for underlying disease, such as chronic kidney disease, hyperthyroidism or heart disease, which may have caused the hypertension.
Treatment has two main aims:
1. To reduce blood pressure using an anti-hypertensive drug, such as amlodipine (Norvasc), which is typically administered for life.
2. To manage underlying disease, such as chronic kidney disease or hyperthyroidism.
It is very important that cats with hypertension be monitored on a regular basis in order to prevent damage to vulnerable organs, such as the eyes, brain, heart and kidneys. Affected cats may live for several years with a good quality of life