Feline hypertension, or high blood pressure, is a frequent and serious health concern, particularly in older cats. This condition is defined by a sustained elevation in systemic arterial blood pressure, typically a systolic reading consistently above 160 millimeters of mercury (mmHg). Hypertension is often considered a silent condition because affected cats rarely show outward signs until the disease has progressed significantly and caused damage to delicate organs. Routine blood pressure checks are the only way to detect this disorder in its early, manageable stages. Appropriate management is important to prevent irreversible complications, such as sudden blindness or stroke.
The Conditions Driving Feline Hypertension
Unlike in humans, where most cases are primary hypertension with no identifiable underlying cause, feline hypertension is overwhelmingly a secondary condition. This means the high blood pressure is a consequence of another existing medical problem. The most common conditions responsible are Chronic Kidney Disease (CKD) and hyperthyroidism.
Chronic Kidney Disease is present in a substantial percentage of hypertensive cats, ranging from 60% up to 100% in some studies of cats presenting with ocular damage. Impaired kidney function disrupts the body’s complex systems for regulating blood volume and arterial constriction. This disruption leads to fluid retention and increased resistance in the blood vessels, resulting in elevated pressure.
Hyperthyroidism, an overproduction of thyroid hormone, is the second most common underlying cause, affecting about 20% of diagnosed hypertensive cats. Thyroid hormones directly increase the heart’s rate and force of contraction, which increases the amount of blood pumped with each beat. This heightened cardiac output and increased metabolic demand contribute to the development of hypertension. Even after successful treatment of hyperthyroidism, blood pressure must still be monitored, as hypertension can sometimes persist or develop later.
Recognizing the Observable Symptoms
Symptoms often become apparent only after sustained high pressure has begun to inflict damage on the body’s most vulnerable tissues. The most dramatic and frequent sign is the acute onset of vision problems. Owners may notice their cat suddenly bumping into furniture, hesitating to jump, or showing signs of disorientation.
The eyes may appear abnormal, presenting with pupils that are fixed and widely dilated, even in bright light. This change is often accompanied by signs of bleeding inside the eye or a detached retina, which is the direct cause of sudden blindness. Prompt veterinary attention is necessary because vision loss due to retinal detachment can be reversed if treated quickly, but the damage can become permanent if left unaddressed for too long.
Other signs can indicate damage to the central nervous system or other organs. Neurological symptoms include disorientation, circling, or loss of balance (ataxia). In more severe cases, a cat may exhibit seizures or subtle behavioral changes, such as excessive restlessness or vocalization. Owners might also notice signs related to the underlying disease, such as increased thirst and urination, common with both kidney disease and hyperthyroidism.
Target Organ Damage
Sustained high blood pressure damages the delicate blood vessels in specific, highly vascularized organs, a consequence referred to as Target Organ Damage (TOD). The four primary areas affected are the eyes, kidneys, brain, and heart. The small arteries in these organs are constantly subjected to immense force, compromising their structure and function.
In the eyes, this leads to hypertensive retinopathy, where the vessels leak fluid and blood into the retina. The most serious ocular consequence is retinal detachment, caused by fluid accumulation or hemorrhage. This detachment leads to acute blindness and is a sign of severe, uncontrolled hypertension.
In the kidneys, chronic hypertension accelerates the progression of existing kidney disease. The high pressure damages the glomeruli, the kidney’s filtering units, leading to the loss of protein into the urine, known as proteinuria. This further compromises kidney function and is associated with a shorter survival time in cats with CKD.
Hypertension can also affect the brain, causing neurological signs ranging from subtle behavioral changes to cerebrovascular accidents, similar to a stroke in humans. The high pressure can cause blood vessels to rupture or block, resulting in localized tissue damage and neurological deficits.
The heart is affected because it must continually pump against the elevated pressure in the systemic circulation. This increased workload causes the muscle wall of the left ventricle to thicken, a condition called left ventricular hypertrophy. While heart failure is less common in cats than in humans, this structural change can lead to abnormal heart sounds, such as murmurs, detectable during an examination.
Treatment and Long-Term Monitoring
The diagnosis relies on accurate blood pressure measurement, typically performed using non-invasive methods like the Doppler or oscillometric devices. Because cats often experience a temporary rise in blood pressure due to stress in a veterinary setting—the “white coat effect”—multiple readings are taken in a quiet environment to ensure a reliable diagnosis. A sustained systolic blood pressure reading above 160 mmHg usually warrants therapeutic intervention.
Treatment involves a two-part strategy: managing the underlying condition and administering anti-hypertensive medication. The first-line medication for lowering blood pressure in cats is commonly a calcium channel blocker, such as amlodipine.
Another medication option, sometimes used in conjunction with amlodipine or as an alternative, is an angiotensin receptor blocker. The goal of therapy is to reduce the systolic pressure to below 160 mmHg initially, with a long-term goal of less than 150 mmHg, to prevent further organ damage. Hypertension is generally a lifelong condition, requiring continuous medication and frequent re-checks, typically every three months once stable, to monitor the cat’s blood pressure and assess for signs of TOD.