If your older cat suffers from chronic kidney disease or hyperthyroidism, there’s a good chance he or she may also have high blood pressure. Hypertension, or high blood pressure, is common in older cats and these diseases are two of the most frequent predisposing factors. Studies have shown that about 60% of cats with chronic kidney failure and 25% of cats with hyperthyroidism have hypertension. Other conditions that can be associated with hypertension in senior cats include heart disease and endocrine (hormonal) disorders such as diabetes mellitus, while some cases appear to have no identifiable cause (idiopathic). Primary or essential hypertension, which accounts for 95% of all cases of hypertension identified in people, is rare in cats.
The outward signs of hypertension are not specific and the condition can be challenging to diagnose without an exam by your veterinarian. Clinical signs of hypertension in cats include:
- Behavioral changes
- Visual abnormalities such as dilated pupils, blood within the chamber of the eye, and sudden blindness, which may first be noticed when the cat is observed walking into furniture or objects
- Increased volumes of urine production
- Symptoms of the underlying disease indicating that it is not adequately controlled
Diagnosis of hypertension starts with a complete medical history and physical exam. Your veterinarian will pay particular attention to any changes in the organs targeted by hypertension—the eyes, brain, heart, and kidneys.
Next, your cat’s arterial blood pressure will be measured by wrapping an inflatable cuff around one of the limbs or tail and connecting it to a device that estimates the pressure within an artery beneath the cuff. The procedure only takes a few minutes, causes no pain, and is well tolerated by most cats. A systolic arterial blood pressure that is consistently greater than 180 mmHg is considered high in cats. Blood pressure readings between 160 and 180 mmHg are also considered too high, but your veterinarian will need to consider the effect of your cat’s temperament and the stress of being in the hospital. The “white coat effect” experienced by people also occurs in cats, and an artificially high reading may be obtained if the cat is frightened or too excited.
Left untreated, the consequences of hypertension can be severe. Cats with very high blood pressure can develop sudden blindness, damage to their kidneys, or seizures and will need to be hospitalized and treated with emergency drugs to lower blood pressure. Extreme hypertension is a medical emergency. Blood pressure must be lowered as soon as possible to preserve remaining function in the damaged organ. Left untreated, the more likely it is that the damage may be permanent.
In chronic cases, treatment is first directed to controlling the underlying disease causing the hypertension. Effective treatments for hyperthyroidism are available. Chronic kidney failure and many heart diseases are not curable but can be medically managed. Your veterinarian may also prescribe an antihypertensive drug. Weight reduction, exercise programs, and low-sodium diets are effective initial therapy in people with hypertension but these measures alone have not been shown to control hypertension in cats.
Regular follow-up visits with your veterinarian to monitor your senior cat’s blood pressure and blood work are a must to prevent serious complications. Ongoing veterinary care for hypertension and the other chronic conditions that may be associated with it, along with a extra little love and attention from you, can brighten your cat’s golden years and help your old friend live and love longer!