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If your typically-lively dog is acting sluggish and getting out of breath more easily, it isn’t something to ignore. One serious cause of breathing problems in dogs is pulmonary hypertension. While the signs of high blood pressure in the arteries of the lungs can mimic other diseases, early diagnosis and targeted treatments can significantly improve the prognosis in many cases.
By learning more about pulmonary hypertension in dogs and working closely with your veterinarian, you can give your pet the best chance at a longer, more comfortable life.
What Is Pulmonary Hypertension in Dogs?
Pulmonary hypertension is a condition where the blood pressure in your dog’s lungs becomes abnormally high. It shouldn’t be confused with systemic hypertension (commonly referred to as high blood pressure).
Dr. Amelia Sinkin is a board-certified veterinary cardiologist at ACCESS Specialty Animal Hospitals – San Fernando Valley, a Thrive Pet Healthcare partner. She explains the body has two circulatory systems that function very differently. One delivers oxygen around your body, and the other is specific to the lungs.
“The circulatory system in the lungs is supposed to be very low pressure — it should be very easy for blood to move through the lungs —” whereas the one in your body is much higher,” Dr. Sinkin says. “The normal blood pressure in your lungs is about 25 millimeters of mercury or less, and normal blood pressure in your body is about 120 millimeters of mercury.”
When the pressure in the arteries of the lungs rises, it makes it harder for your dog’s heart to pump blood through the lungs to pick up oxygen. Over time, this can lead to right-sided heart enlargement or even heart failure.
Causes and Classification of Pulmonary Hypertension in Dogs
Pulmonary hypertension in dogs is usually caused by an underlying condition and can be classified in several ways. Your veterinarian may refer to one of two overarching categories: pre-capillary or post-capillary pulmonary hypertension. This depends on where the increased pressure originates relative to the tiny blood vessels (capillaries) in the lungs.
Dr. Sinkin explains that pre-capillary pulmonary hypertension has numerous causes, most relating to a primary disease of the lungs or a problem with the respiratory system. Post-capillary pulmonary hypertension is most often caused by heart disease in dogs.
Some of the most common reasons your dog can develop pulmonary hypertension include:
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Left-sided heart disease (especially mitral valve disease): Common in older, small breed dogs, this condition causes blood to leak back into the heart, causing fluid to build up in the lungs.
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Congenital heart defects: Conditions like patent ductus arteriosus (PDA) or ventricular septal defect (VSD) can increase blood flow into the lungs.
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Chronic lung issues: Conditions like chronic dog bronchitis or airway collapse (common in toy breeds) can increase lung pressure.
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Blood clots (pulmonary thromboembolism): These block lung blood vessels and are often secondary to other health conditions.
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Heartworm disease: Dr. Sinkin emphasizes the importance of administering regular heartworm protection treatments for this 100% preventable cause of pulmonary hypertension.
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Idiopathic: Your veterinarian may refer to pulmonary hypertension this way when they cannot identify a cause.
Signs and Symptoms of Pulmonary Hypertension in Dogs
The signs of pulmonary hypertension in dogs vary depending on the condition’s severity and the underlying cause. In the early stages, your dog may not show any outward symptoms and will receive a diagnosis during evaluation for another condition. As the disease progresses, symptoms tend to become more noticeable.
“I think the most common way that dogs with primary pulmonary hypertension (not secondary to heart disease) are diagnosed is because they experience episodes of fainting, especially with excitement,” Dr. Sinkin says. “They can’t get the oxygen that they need because the blood can’t get through their lungs easily.”
Other signs you may notice as the condition progresses include:
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Rapid or labored breathing, even when your dog is resting
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Reduced energy (your dog may slow down on walks or avoid play)
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Coughing, especially when your dog has an underlying respiratory issue
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Swollen belly, due to fluid buildup (ascites)
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Blue or purple gums or tongue (a sign of low oxygen)
If you see any of these signs, don’t delay in contacting your vet.
Diagnosis of Pulmonary Hypertension in Dogs
Diagnosing high blood pressure in the arteries of the lungs can be challenging because the signs mimic other dog diseases. For example, congestive heart failure in dogs looks almost exactly the same as advanced pulmonary hypertension on chest X-rays.
“For a definitive diagnosis, you need an echocardiogram, and it generally should be performed by a board-certified veterinary cardiologist,” says Dr. Sinkin. This non-invasive, advanced ultrasound examination can estimate the pressure in your dog’s lungs, evaluate heart size, and identify other problems such as heartworm or blood clots.
In many general veterinary practices, the equipment or expertise to perform a full echocardiogram isn’t available, though some may be able to perform a preliminary scan. In rural areas without cardiologists, veterinarians may make a suspected diagnosis based on available evidence and begin treatment.
Other tests to establish underlying causes may include chest X-rays, bloodwork, urinalysis, and screening for heartworms or lung disease.
Treatment of Pulmonary Hypertension in Dogs
Treatment depends on the underlying cause and the severity of your dog’s pulmonary hypertension. Sometimes, eliminating or improving the underlying condition, such as heartworm disease, can resolve your dog’s lung-related problems. In many cases, your veterinarian will provide ongoing treatment for both the underlying condition and the high blood pressure in your dog’s lungs. When it’s not possible to identify the underlying cause, long-term treatment of the pulmonary hypertension is the only option.
Dr. Sinkin explains that the primary treatment for pulmonary hypertension in dogs is the administration of pulmonary vasodilators. “They specifically target the blood vessels in the lungs to dilate them,” she says. These drugs are generally very effective, fast-acting and well-tolerated. The one that veterinarians most commonly prescribe is sildenafil (Viagra®). However, longer-lasting but more expensive tadalafil (Cialis®) may also be used.
While Dr. Sinkin points out that any dog can have a reaction to any drug, she says side effects for either of these medications are rare. Mild symptoms like skin flushing have occasionally been reported.
For dogs in acute distress, oxygen therapy is often used. “Oxygen is a very potent dilator of the blood vessels in the lungs,” Dr. Sinkin says. “We can’t realistically use it long term, but often dogs with pulmonary hypertension will initially spend two to three days in an oxygen cage while the sildenafil begins working.”
Pimobendan (Vetmedin®), a drug that improves heart function, can be helpful in cases related to left-sided heart failure. Your veterinarian may also advise on appropriate supportive care, including avoiding strenuous exercise until stable.
Prognosis and Management of Pulmonary Hypertension in Dogs
The outlook for dogs with pulmonary hypertension depends on the underlying cause and its severity. Dogs with pulmonary hypertension secondary to advanced heart disease or aggressive lung disorders have a more guarded prognosis. In contrast, dogs with treatable underlying conditions and a good response to medication can live for years with a high quality of life. “The majority of dogs that I see with pulmonary hypertension do pretty well once they’re on their drugs,” Dr. Sinkin says. “I check them every three to six months, and very rarely do I have to adjust medications.”
Most dogs don’t need major lifestyle changes once on treatment, but avoid taking them climbing up big mountains or on a plane. This can trigger dangerous increases in pulmonary pressure. “Oxygen at higher altitude is decreased, and oxygen is one of the primary things that dilates the blood vessels in the lungs,” Dr. Sinkin explains.
Dr. Sinkin explains that there shouldn’t be any signs of pulmonary hypertension once your dog is stable. “They should be able to get excited and breathe normally,” she says. “If you ever notice their breathing is getting fast, or they’re fainting or have exercise intolerance, reach out, as that means we probably need to adjust their medication.”
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