Systemic hypertension, the persistent elevation of systemic arterial blood pressure, is a significant health concern in the feline population, particularly among older cats. This condition is often described as a silent disease because cats rarely show overt signs until the high pressure has begun to damage internal organs. Undetected and untreated, this elevated pressure can lead to severe and sometimes irreversible consequences in a cat’s eyes, brain, kidneys, and heart. For senior cats, regular monitoring is an important part of proactive veterinary care to identify this condition early.
Understanding the Causes and Risk Factors
Unlike in humans, high blood pressure in cats is nearly always a secondary condition, meaning it is caused by another underlying disease process. This secondary form is the most common type of feline hypertension, making it a complication rather than a standalone illness. Identifying and managing the primary disease is therefore a fundamental part of the overall treatment plan.
The two diseases most frequently linked to feline hypertension are Chronic Kidney Disease (CKD) and hyperthyroidism. A large percentage of cats diagnosed with CKD will also exhibit high blood pressure, with estimates suggesting this occurs in 20% to 60% of affected patients. The damaged kidneys struggle to regulate fluid balance and hormones, which contributes to the rise in arterial pressure.
Hyperthyroidism, an overproduction of thyroid hormone common in older felines, is another significant risk factor. The excess thyroid hormone increases the cat’s metabolic rate and heart output, which can lead to hypertension in approximately 10% to 20% of hyperthyroid cats. In a smaller percentage of cases, primary hypertension occurs where no underlying cause can be identified, but this form is rare, potentially accounting for less than 20% of cases.
Recognizing the Visible Signs of High Blood Pressure
High blood pressure often causes damage to sensitive structures in the body, known as target organs, before an owner notices any symptoms. The eyes are particularly vulnerable, and ocular changes are often the first visible signs that lead to a diagnosis. Acute blindness, which can appear suddenly, is a common presentation caused by the retina detaching or hemorrhaging due to the high pressure.
Owners might observe signs like dilated pupils that do not constrict in bright light, or a cat bumping into furniture. Subtle ocular signs, such as bleeding or swelling in the back of the eye, can be detected by a veterinarian during an examination. Neurological signs may also manifest in 15% to 40% of hypertensive cats, including disorientation, seizures, and unusual behavioral changes like excessive vocalizing or restlessness.
The sustained pressure also impacts the kidneys and heart, though these signs are often less obvious to the owner. Subtle signs like a decrease in appetite or unexplained weight loss may be related to underlying organ changes accelerated by the hypertension.
How Vets Measure Feline Blood Pressure
Measuring blood pressure in cats is a non-invasive procedure, but it presents a unique challenge due to the cat’s natural reaction to a veterinary visit. The stress of being handled in an unfamiliar environment can cause “situational hypertension” or the “white coat effect,” leading to temporarily elevated readings that do not reflect the cat’s true pressure. To mitigate this, veterinary staff typically allow the cat a period of acclimatization in a quiet room before taking measurements.
Veterinarians use indirect methods, most commonly the Doppler or oscillometric techniques. The Doppler method involves placing a small cuff, sized appropriately for the cat’s limb or tail, and using an ultrasound probe to listen for the return of blood flow as the cuff is deflated. This technique is reliable for determining the systolic arterial pressure (SAP).
Multiple readings are taken, usually between five and seven, and the first few are often discarded to account for initial stress. A cat is considered to have a normal SAP below 140 mmHg. An SAP consistently between 160 and 179 mmHg is classified as moderate hypertension, indicating a need for intervention to prevent serious organ damage. Readings at or above 180 mmHg represent severe hypertension and require immediate treatment.
Treatment and Long-Term Management
The management of feline hypertension involves a two-pronged strategy: treating the underlying disease and directly lowering the blood pressure. Addressing the primary condition, such as managing CKD or treating hyperthyroidism, can sometimes help control the blood pressure. However, specific antihypertensive medication is also required to protect the vulnerable target organs from further damage.
Amlodipine, a calcium channel blocker, is the most frequently recommended medication for reducing high blood pressure in cats. This drug works by relaxing the blood vessel walls, which eases the pressure within the arteries and lowers the overall systemic pressure. The dose is carefully titrated by the veterinarian, often starting low and increasing until the cat’s SAP is reduced to a safer target range, ideally below 160 mmHg.
Long-term management requires frequent rechecks to ensure the medication is effective and that the blood pressure remains controlled. Regular monitoring includes blood pressure measurements, repeat blood work to check kidney function, and eye examinations to look for any signs of damage or progression. While untreated feline hypertension carries a poor prognosis with a high risk of blindness and stroke, consistent treatment and monitoring can significantly improve the cat’s quality of life and longevity.