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Systemic Hypertension (High Blood Pressure)

What is systemic hypertension (high blood pressure)?

The body has complex control systems that maintain blood pressure within a normal range. When the overall pressure within the blood vessels becomes high, it is called "systemic hypertension," or "high blood pressure." High blood pressure usually develops gradually. The word "systemic" means that the problem is affecting the whole body. "Hyper-" comes from Greek, and means excessive, or above. Tension (derived from Greek "tonos") refers to the pressure in the blood vessels. Your veterinarian may refer to diastolic and systolic pressure. These two values represent the peak (systolic) and trough (diastolic) of the pressure levels that occur with each contraction and relaxation of the heart.

What causes systemic hypertension?

No cause of systemic hypertension is clearly identified. It often is associated with an underlying problem such as kidney disease, or hormone imbalances caused by diseases of the thyroid glands or adrenal glands. Any control system imbalance that has an effect on the blood vessel capacity or heart pump efficiency can upset the delicate balance. No inherited factors (genetic predisposition) are known.

What are the signs of systemic hypertension?

The circulatory system reaches every square inch of the body, so the effects of the pressure buildup in the blood vessels are far-reaching. Signs may include:

How is systemic hypertension diagnosed?

The diagnosis of systemic hypertension may require an in-depth evaluation of your animal's internal health status. Many animals with high blood pressure have no signs of it. Signs noted during the physical examination (such as bloody nose or urine or changes in the eyes) often will lead to suspicions of systemic hypertension. However, the only way to diagnose it definitely is to measure the pressure in the circulation system. Special equipment is required to measure blood pressure in dogs and cats.

One of the big problems with diagnosing high blood pressure in cats and dogs is obtaining an accurate blood pressure measurement. Many people get nervous at the doctor's office, where blood pressure measurements reflect stress rather than their normal levels. The same phenomenon occurs in many dogs and cats when they see the veterinarian, and sometimes leads to falsely elevated blood pressure readings.

The veterinarian may perform diagnostic tests, such as blood work, urinalysis, and hormone assays (for example, thyroid hormone). Imaging studies, such as radiographs (X-rays) or ultrasound (visualization of deep body tissues by recording ultrasonic waves) of the chest and abdomen may identify related problems.

How is systemic hypertension treated?

The treatment for systemic hypertension depends on the severity of the high blood pressure and the clinical signs. The animal usually is managed on an outpatient basis unless the condition has progressed to the point where serious complications, such as eye damage, are identified. Reducing salt intake may be recommended as part of the therapy. Most animals with systemic hypertension require medication to lower their blood pressures. Medications commonly used include vasodilators that expand (dilate) the blood vessels and diuretics to remove excess body fluids. Sometimes a combination of medications may be needed in order to control the blood pressure adequately and to minimize the any side effects.

What is the prognosis for animals with systemic hypertension?

High blood pressure generally can be controlled with medications and if possible, correction of the underlying cause. As with most conditions, the prognosis (outcome) for animals with systemic hypertension ultimately depends on the underlying reason for the high blood pressure. The prognosis for animals with hypertension due to kidney failure is generally poor. The prognosis is fair in animals with adrenal gland disease and generally good with thyroid disease. The most important aspect affecting the animal's future is that the problem be identified before serious organ damage occurs. Once the elevated blood pressure produces wear and tear on the delicate blood vessels of the eye and kidney permanent tissue damage is a concern.

Larry Tilley's Recommended Info site (www.VetMedCenter.com)