Overview of Feline Hypertension
Elevated blood pressure – properly called systemic arterial hypertension – is an increase in the systolic or diastolic arterial blood pressure (ABP). Blood pressure has two values: the systolic pressure, which is the high value that develops as the heart contracts and pumps blood, and the diastolic pressure, the low value that occurs as the heart relaxes and fills. For example, 120/80 means a systolic pressure = 120 mm Hg and diastolic pressure = 80 mm Hg.
Below is an overview of Hypertension in Cats followed by in-depth information on the diagnosis and treatment of this condition.
A systolic ABP consistently exceeding greater than 160 mm Hg in the cat is considered high. Diastolic pressure in cats should not exceed the 100 to 110 mm Hg range provided it is recorded when the pet is relaxed.
Causes of High Blood Pressure in Cats
Chronic kidney disease
Diseases of the endocrine system such as Cushing’s disease
Tumors of the adrenal gland, such as pheochromocytoma, which is an adrenocortical tumor causing Cushing’s disease or Conn’s disease
Central nervous system disorders.
Some cases of hypertension are idiopathic or essential, which means that they have no known cause.
A cat predisposed to kidney disease is more likely to develop hypertension.
Hypertension can affect your cat by causing injury to the following “target” organs including: brain, eyes, heart, kidneys and blood vessels. Hypertension can be suspected by symptoms and clinical examination but can only be diagnosed by repeated measurements of the ABP.
What to Watch For
Symptoms related to underlying diseases (such as endocrine disorders)
Diagnosis of Hypertension in Cats
Diagnostic tests are needed to recognize hypertension, to help deterine its cause, and exclude other diseases. Tests may include:
Complete medical history and physical examination. Examination should be directed towards the target organs of hypertension. Careful inspection of the eyes, nervous system, heart and kidneys should be completed.
Diagnosis requires measurement of arterial blood pressure. This is generally done using a cuff, similar to that used in children, and a blood pressure device. The stethoscope or auscultatory method used in people cannot be used in cats; instead, the pressure must be determined with either a Doppler flow device or an oscillometric device. Cats can have an “artificially” elevated blood pressure if they become excited. Accordingly, the veterinarian should make repeated measurements of blood pressure before making a diagnosis of hypertension. This may require a brief hospitalization in order to allow repeated measurements in a calm patient.
The underlying cause of hypertension must be identified and this may require blood tests of endocrine function, X-rays or ultrasound examination of abdominal organs.
Treatment of Hypertension in Cats
Treatments for hypertension may include one or more of the following:
The underlying cause of hypertension should be treated. This treatment should be individualized for the patient and the associated problems.
A hypertensive crisis (very high blood pressure with severe clinical signs or evidence of a stroke) should be treated aggressively. This requires hospital treatment with drugs that lower blood pressure. These may include sodium nitroprusside, diuretics, amlodipine or other vasodilator drugs.
Chronic treatment of hypertension in cats usually begins with a calcium channel blocker, amlodipine.
In most cases, a reduction in weight and in dietary sodium will be recommended; however, without drug therapy, these measures will be ineffective in controlling hypertension in cats.
Home Care and Prevention
Administer all treatments as prescribed. Schedule regular follow-up visits to ensure that treatment is successfully controlling the blood pressure. Monitor your cat’s activity, alertness, appetite and general quality of life on a regular basis.
Hypertension develops in association with diseases that, at this time, are not preventable.
In-depth Information on Hypertension in Cats
Hypertension can be difficult to diagnose in cats. The stethoscope (listening) method used to diagnose hypertension in people cannot be used in cats. A Doppler device is needed to detect blood flow or a special instrument that measures oscillations in the blood vessels must be used. Excitement can artificially raise blood pressure, just as it does in people (white coat effect).
The diagnosis of hypertension requires close attention to the technical aspects of blood pressure measurement such as selection of the appropriate cuff size and assuring uniform compression of the artery.
When there are associative clinical signs or diseases related to hypertension, a high blood pressure measurement is of great significance. In the otherwise healthy cat, diagnosis should be approached cautiously so as not to label a healthy, but perhaps excited, pet as hypertensive.
The underlying cause of hypertension must be addressed. Known causes include: chronic kidney diseases, hyperadrenocorticism (Cushing’s disease), hyperthyroidism, tumors of the adrenal gland (pheochromocytoma/adrenocortical tumor), drugs such as those used to treat urinary incontinence in cats and central nervous system disorders.
Hypertension can also develop from diseases of the endocrine organs. Diseases of the adrenal gland are particularly common in cats and have been associated with hypertension. One example is Cushing’s disease, which may be controlled by medication.
Some cases of hypertension are idiopathic or essential, which means they have no known cause.
Hypertension can cause serious injury to target organs including the brain, eyes, heart, kidneys and blood vessels in these and other organs. These changes can include:
Cerebral or brainstem vascular injury can cause swelling (edema) or the bleeding into the brain that is also called a stroke. Clinical symptoms include abnormal behavior, depression, neurological deficits, head tilt, seizures and coma.
Retinal edema (swelling) or hemorrhage and retinal detachments (separation of the layers) can lead to sudden blindness. Sudden blindness may also develop consequent to bleeding into the eye, known as intraocular hemorrhage or hyphema.
Elevated blood pressure increases the work of the heart. Frequently, a murmur or extra heart sound, an atrial gallop, will be heard with the stethoscope in cats with hypertensive heart disease. Left ventricular thickening (hypertrophy) and heart enlargement (cardiomegaly) are indications of chronic hypertension. These changes can be identified by an echocardiogram (most sensitive), electrocardiogram or thoracic radiograph (least sensitive). Coronary arteries also are injured from high arterial pressures. Heart failure stemming from hypertensive heart disease is exceedingly rare. In cats with chronic valvular heart disease, hypertension increases the risk for development of congestive heart failure.
Kidney disease is one of the most common reasons for high blood pressure. Glomerular disease is especially associated with hypertension. High blood pressure continues to injure the kidneys creating a vicious cycle.
Injury to blood vessels or direct transmission of pressure across the microscopic blood vessels and capillaries is responsible for many of the clinical signs of hypertension.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnostic tests are needed to recognize hypertension and exclude other diseases. Tests may include:
Repeated measurements of arterial blood pressure using a Doppler flow device or an oscillometric device
Complete medical history and physical examination
Examination directed to the potential causes of hypertension and to the organs injured by high blood pressure
A neurological examination
Examination of the heart to include physical diagnosis using a stethoscope, chest X-rays or an echocardiogram (ultrasound of the heart).
Kidney exam, including physical examination, blood tests, urinalysis and diagnostic imaging, X-rays or ultrasound
Additional diagnostic tests may be recommended on an individual basis, including:
Identification of the underlying cause of hypertension. This may require a variety of laboratory tests including blood tests of endocrine function, specialized X-rays or ultrasound examination of abdominal organs.
Detailed urine analyses for identification of some forms of kidney disease.
Treatments for hypertension may include one or more of the following:
The principles of therapy include management of the underlying cause of hypertension and lowering of the arterial blood pressure. Treatment must be individualized for the patient and the associated problems and may include one or more of the following:
Hypertensive crisis (very high blood pressure with severe clinical signs such as stroke, impaired consciousness or blindness) should be treated aggressively in the hospital with drugs that lower blood pressure. The potent intravenous vasodilator drug, sodium nitroprusside, may be used for this purpose. Sodium nitroprusside must be carefully administered and this may require transfer to an emergency hospital. Diuretics, amlodipine or other vasodilator drugs (hydralazine) can also be used in a hypertensive crisis.
Hypertension in cats is relatively common. The best therapy at this time appears to be the calcium channel blocker, amlodipine. This pill is given once or twice daily and must be broken to achieve correct the dose. If this is ineffective, other treatments such as those used in dogs may be considered.
Most people are familiar with treating hypertension initially using weight reduction and exercise programs and decreases in dietary sodium intake. Unfortunately, these measures are rarely, if ever, effective in controlling hypertension in cats. Certainly, a reduction in dietary sodium (salt) is appropriate for most patients, but diet alone will not be enough.
Management of hypertension may never be completely successful unless the underlying cause can be managed. This can be difficult with certain diseases or tumors of the adrenal gland.
Organs injured by hypertension may recover in some cases once the blood pressure is controlled. In other situations, the prognosis for neurologic function, sight and cardiac function depends on the duration of clinical symptoms.
Follow-up Care for Cats with Hypertension
Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up can be critical. Administer prescribed medication(s) as directed, and be certain to alert your veterinarian if you are experiencing problems treating your cat.
Rechecking your cat’s arterial blood pressure value is important. Failure to follow-up with repeated blood pressure checks is one of the most common causes of treatment failure. Medication dosage often must be adjusted over time.
Most cats are obviously improved once their blood pressure is brought into the normal range. You should see increased activity and often an improvement in appetite and general “quality of life.”
Alert your veterinarian to any new or changing symptoms.