Causes and Treatment of High Blood Pressure in Cats
High blood pressure, also called hypertension, is a serious problem in senior cats. Feline hypertension may be primary (without any underlying medical problem) or secondary (caused by another underlying disease). Secondary hypertension in cats is more common and often associated with chronic kidney disease, hyperthyroidism, heart disease, and other diseases. Continue reading to learn more about the causes and treatment options for cats with high blood pressure.
What is hypertension?
A cat is said to have hypertension when its systolic blood pressure (SBP) is greater than 160 mmHg or if the SBP is greater than 150 mmHg and accompanied by symptoms of hypertension-associated organ damage.
Since high blood pressure in cats often goes unnoticed until significant organ damage has occurred, the International Society of Feline Medicine (ISFM) recommends routine blood pressure screening for cats. Healthy senior cats that are 7-10 years old should be checked yearly. Healthy senior cats that are 11 years and older should have their blood pressure checked every 6-12 months. Cats with chronic kidney disease, ongoing high blood pressure, or other diseases that increase the risk of hypertension should be checked every 3-6 months.
Causes of High Blood Pressure in Cats
The two most common predisposing factors for the development of high blood pressure in cats are kidney failure and hyperthyroidism. There are also certain diseases of the heart, like hypertrophic cardiomyopathy, that cause hypertension.
In kidney disease, there appear to be several mechanisms that can pave the way for hypertension to develop in cats. One popular theory is age-related changes in the kidneys, particularly the formation of scar tissue over time that makes blood harder to filter through. When this happens, blood backflows into the arteries and leads to an increase in blood pressure.
Hyperthyroidism can affect various organs of the body, including the heart. When there is an excess production of thyroid hormone, the heart becomes overloaded and overworked. Its pumping action becomes faster and more forceful. This increased demand for blood circulation can eventually lead to an enlargement of the heart.
In cats with hypertrophic cardiomyopathy, the abnormally thick walls of the heart prevent it from efficiently performing its job of pumping blood. The decrease in blood volume within the chambers of the heart can eventually lead to an increase in pressure. With less blood pumped by the heart, there is an increase in the demand for blood flow throughout the body. An increase in blood pressure is the body’s way of attempting to meet this demand.
Symptoms of High Blood Pressure in Cats
In the early stages of high blood pressure, the symptoms often go unnoticed by many cat parents. The problem may only be noted during a routine measurement of the cat’s blood pressure.
Sustained or chronic high blood pressure causes damage to various organs of the body. These include the following:
Eyes - Vision problems are the most common findings associated with hypertension in cats. High blood pressure can cause bleeding into the eyes. Swelling and detachment of the retina can also occur. These conditions can eventually lead to vision problems in cats. Blindness can often be permanent if prompt and aggressive treatment is not given. Blindness is usually suspected when a cat keeps bumping into objects in their immediate environment. Other symptoms include blood in the clear part of the eye and dilated pupils.
Nervous System - Bleeding in the brain and other parts of the nervous system caused by hypertension can cause the display of neurological symptoms, such as seizures, strange behavior, wobbly gait, dementia, fainting episodes, and coma.
Heart - When a cat has high blood pressure, the muscles of the heart’s left ventricle need to work harder to pump blood. Being overworked eventually causes the heart’s walls to become thick. Once this happens, the heart’s ability to pump blood becomes greatly compromised and without appropriate medical intervention, congestive heart failure (CHF) may eventually develop. The symptoms exhibited by affected cats are associated with CHF - difficulty breathing, lethargy, or even sudden death. Heart murmurs (abnormal heart sounds) may also be observed during a veterinary exam.
Kidneys - High blood pressure that remains uncorrected can lead to kidney damage and may increase a cat’s risk of developing kidney failure. If there is already an existing kidney disease, hypertension is likely to worsen the disease significantly over time. Affected cats show increased water intake and/or frequent urination, vomiting, lethargy, and there is unexplained weight loss.
Treatment of High Blood Pressure in Cats
The treatment protocol for hypertension in cats is three-pronged. First, the target organs, such as the kidneys and eyes, should be protected from serious damage and complications. Second, left ventricular hypertrophy that is associated with chronic hypertension should be reversed. Third, treatment is aimed at protecting the kidneys, especially the remaining functioning nephrons, lowering the pressure in the glomerular capillaries, and decreasing the severity of proteinuria.
In primary hypertension, complications can be prevented if hypertension is managed. In cases of secondary high blood pressure, the long-term success depends to a large extent on the nature and severity of the underlying disease. If hypertension is caused by hyperthyroidism, heart disease, or kidney disease, aggressive treatment of these conditions must be done, if possible.
Early diagnosis and appropriate treatment are very important to a successful outcome and to prevent the development of irreversible complications. The importance of accurately monitoring hypertension regularly can never be overemphasized.
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