Blood pressure is a measurement of the pressure inside the arteries during the heart's contractions, as well as the pressure in the arteries during the pause between heartbeats. The pressure during the heart's contraction is called systolic pressure. This is the higher, or upper, number on a typical blood pressure reading. The pressure during the pauses between beats is called diastolic pressure, and is the lower number of a blood pressure reading.
Hypertension, commonly called high blood pressure, means that one, or most often both, of these numbers are abnormally high. Just like people, dogs can get hypertension for a variety of reasons. Also like humans, hypertension in dogs does not have direct symptoms of its own, but left untreated, can lead to a variety of damage throughout the body. In some dogs, the first indication of high blood pressure is sudden blindness due to damage to the delicate retina of the eye. Hypertension can also damage the kidneys and heart.
The majority of dogs with high blood pressure are older pets with some type of underlying health issue. That's why it's so important for your senior pet to have regular checkups where the vet can check blood pressure and recommend treatment for both the hypertension and the condition causing it.
What Is Hypertension?
Your vet may refer to it as systemic arterial hypertension, but the condition is more often referred to simply as hypertension or high blood pressure. Hypertension is a common condition in older dogs, but you are unlikely to know your pet has it unless the condition is revealed at a veterinary checkup during a blood pressure check.
Blood pressure is measured in millimeters of mercury, abbreviated as mmHg. Blood pressure results are read as systolic over diastolic. For example, if the systolic is 140 and diastolic is 80, the reading would be 140/80 mmHg. When measuring blood pressure in pets, however, most veterinarians are only interested in the systolic pressure, as it can be difficult to get a reading of diastolic pressure in animals.
The normal systolic blood pressure for dogs is in the 120 mmHg to 130 mmHg range, but because dogs typically are stressed or frightened at the veterinarian's office, many vets don't consider blood pressure to be truly elevated unless the number is above 160 mmHg. The American College of Veterinary Medicine considers systolic blood pressure that's between 150 mmHg and 159 mmHg to be mildly elevated, while readings of 180 mmHg or above indicate a high risk of damage to internal organs.
Symptoms of Hypertension in Dogs
Hypertension itself does not usually cause specific signs in dogs. However, the harmful effects of high blood pressure can cause bleeding in small blood vessels throughout the body, particularly in the delicate blood vessels within the eyes, kidneys, and brain. The heart can also be damaged by the abnormally high pressures within the arteries, which forces the heart to work harder to pump blood effectively. The following signs might be seen in conjunction with hypertension in dogs:
Blood-vessel bleeds caused by hypertension can lead to blood clot formations, called embolisms, which can become lodged within smaller blood vessels throughout the body. If one becomes lodged in an artery in the brain, it can cause stroke symptoms, such as a wobbly gait, head tilt, seizures, disorientation, collapse, abnormal eye movements, or paralysis.
More often, however, hypertension in dogs damages the eyes, leading to partial or complete blindness which may develop slowly or come on suddenly. Kidney damage is also a frequent companion of high blood pressure.
Causes of Hypertension
Hypertension is often divided into two categories: primary and secondary. Primary hypertension is the most common form of hypertension in humans: Around 95 percent of people with high blood pressure have this form of the condition. With primary hypertension, the direct cause is unknown, although there are risk factors, including smoking, lack of exercise, being overweight, and poor diet, that contribute to the development of this common problem.
Dogs, however, are far more likely to have secondary hypertension. With this form, the hypertension is caused by another health issue or disease. The following are the most common health conditions that underlie canine hypertension.
- Kidney disease: Kidney disease, including chronic renal failure where the kidneys lose the ability to thoroughly filter the blood, is the most common cause of hypertension in dogs, with studies showing that the majority of dogs with renal failure have hypertension.
- Glomerular disease: This is another type of kidney disease that involves excessive loss of protein through the urine due to "leaks" in the kidney's filtering system.
- Cushing's disease: This is a disorder of the adrenal glands that leads to overproduction of the hormone cortisol.
- Diabetes: Diabetic dogs do not produce enough insulin, leading to excessive glucose in their blood.
- Pheochromocytoma: This rare adrenal gland tumor secretes excessive adrenaline.
Diagnosing Hypertension in Dogs
Your veterinarian will run blood and urine tests to identify the underlying disease causing the hypertension. However, the hypertension itself is diagnosed by checking the dog's blood pressure directly. Most often, the vet will check the blood pressure several times during the visit, and then average the results.
It can be difficult to obtain an accurate blood pressure measurement on a dog in a clinical setting. First, nervousness or excitement can artificially raise blood pressure. Second, dogs are not as likely to sit still for the measurement. Veterinary professionals work to keep dogs relaxed and calm so they can properly measure blood pressure.
The process of measuring blood pressure in dogs is similar to that used on humans. The veterinarian fits a cuff around the dog's upper front leg, lower rear leg, or base of the tail. Vets typically have a variety of cuffs in different sizes to suit their patients.
The cuff is inflated to apply pressure to the underlying blood vessels, and then slowly released while the vet uses an ultrasonic probe placed over the artery to produce an audible sound. The point at which blood pressure is sufficient to push blood through the partially occluded blood vessel is the systolic pressure.
If your dog's blood pressure averages out to 160 mmHg, most veterinarians will diagnose it as having hypertension.
Treatment & Prevention
Once your veterinarian has diagnosed hypertension in your dog, the first step is to treat the underlying cause, whether that's kidney disease, diabetes, or another illness. Managing the primary disease can help reduce blood pressure. However, most dogs will still need medication specifically formulated to lower blood pressure.
Veterinarians usually prescribe vasodilators, a group of drugs that open the blood vessels and reduce blood pressure. Most hypertensive dogs will need to remain on medication for the remainder of their lives. Common medications used for hypertension include the following:
Lowering dietary sodium intake is sometimes recommended in dogs, but this is not as prevalent as it is in humans. Your vet can recommend special foods for your dog if a low-sodium diet is recommended.
Be sure to follow your vet's treatment plan precisely and go back for follow-up visits as recommended. Contact your vet if your dog is not responding well to treatment or if there are changes in your dog's condition. Never adjust medications or other treatments without talking to your vet first.
Because hypertension in dogs is usually caused by an underlying illness, it is difficult to prevent entirely. However, you can help ward off the development of this health issue by having your vet regularly check your senior dog's blood pressure at annual visits and managing any chronic illnesses, particularly kidney disease and diabetes, as effectively as possible.
Prognosis for Dogs With High Blood Pressure
Your dog's prognosis greatly depends on the underlying condition causing the hypertension, as well as symptoms that develop. For dogs with end-stage kidney disease, dogs that have suffered stroke or heart issues, or dogs with poorly controlled diabetes, the prognosis is guarded. However, if the underlying issue is well managed and the hypertension treated, your dog may enjoy its golden years happily with you.
High Blood Pressure in Pets. Mar Vista Animal Medical Center.
Systemic Hypertension (High Blood Pressure) in Dogs. VCA Animal Hospitals.
Systemic Hypertension. Chesapeake Veterinary Cardiology Associates.
The Difference Between Primary and Secondary Hypertension. Beth and Howard Braver, MD.