Cor pulmonale is a complex condition in dogs. ‘Cor’ is the Latin word for ‘heart’, and ‘pulmonale’ refers to the lungs; it describes the situation when disease of the lungs goes on to cause heart failure. Having both these vital organs compromised sounds serious, and it is. So why does it develop and what does this diagnosis actually mean for your dog?
What is cor pulmonale?
Cor pulmonale is a term used to describe changes in the right side of the heart that result from diseases affecting the lungs or the blood vessels within the lungs. In dogs, this usually means the right side of the heart has to work much harder than normal to pump blood through damaged or constricted lung tissue or blood vessels. Over time, this extra work can cause the right side of the heart to become enlarged and weakened, ultimately ending in right sided heart failure.
How does cor pulmonale develop?
Cor pulmonale starts with lung disease. This is usually a chronic disease (something that develops over a long time) such as bronchitis, heartworm disease, pneumonia, laryngeal paralysis or tracheal collapse. These conditions reduce the amount of oxygen that can get into the lungs and ultimately cause high blood pressure within the lungs (also known as pulmonary hypertension). As the pressure in the lungs increases, the right side of the heart must work harder and harder to pump blood into the lungs against this pressure. Like any muscle that works hard for a long time, eventually the heart muscle will get ‘tired’ and weaker so its ability to pump blood reduces and the right side of the heart begins to fail.
The changes to the heart and lungs generally happen slowly with cor pulmonale, but occasionally an acute (rapidly developing) lung disease such as a pulmonary embolism (a blood clot in the lungs) can cause it to develop suddenly.
How will I know if my dog has cor pulmonale?
Cor pulmonale can be tricky to diagnose because of the complex combination of causes. Your dog may have lung disease for a long time but never go on to develop cor pulmonale. But, if the pressure in the lungs is too high for too long, the right side of the heart starts to fail and you will see cardiac related signs as well as respiratory signs.
Possible signs of cor pulmonale in your dog:
- Coughing
- General tiredness (lethargy)
- Fainting episodes (syncope)
- A visible pulse in the jugular vein in the neck
- A swollen abdomen due to fluid build-up (ascites)
- Distressed breathing (dyspnoea)
- A bluish gum colour (cyanosis)
- Collapse
These signs usually develop very gradually and can be subtle and hard to notice until a lot of damage to the lungs and heart is done. The only exception is in the case of a pulmonary thromboembolism which will cause severe respiratory distress ‘out of the blue’.
While each dog may show a slightly different combination of symptoms, the underlying cause is the same: the right side of the heart is struggling to pump blood efficiently due to high pressure in the lungs.
What might my vet do?
Imagine your 9-year-old dog, Max. Over the past few months, you notice he becomes tired more easily on walks, has started to cough frequently and sometimes has difficulty breathing, especially after exercise. You have planned a check-up at the vets next week, but Max got very excited today and fainted, so you rush him straight into the practice. By the time you arrive he has made a seemingly full recovery, but the vet checks him over and finds a few concerning signs – some abnormal heart sounds, an irregular pulse and blue-tinged gums. They are suspicious of cor pulmonale but need to run some further tests to confirm it:
- Chest X-rays – these can reveal changes in the size of the heart and show evidence of lung disease or fluid build-up.
- Echocardiogram (an ultrasound scan of the heart) – this allows the vet to visualise the chambers of the heart, assess their size and how well they are pumping blood, and measure any enlargement, especially on the right side.
- Blood tests – these help identify underlying diseases such as heartworm or other systemic illnesses.
- Electrocardiogram (ECG) – this records the electrical activity of the heart and can show abnormal rhythms or other abnormalities associated with cor pulmonale.
- Specific additional tests may also be recommended to pinpoint the underlying cause such as advanced imaging to look for tumours or other lung conditions.
Can it be treated?
Treatment of cor pulmonale focuses on managing both the symptoms of the heart failure and the underlying cause of the lung disease. The main goal is to reduce the blood pressure in the lungs and the workload on the right side of the heart. If this can be achieved, it can improve your dog’s quality of life.
If an underlying condition (e.g. heartworm or bronchitis) is identified, a specific treatment protocol to treat this will be started. Medications to treat the lung disease such as antibiotics, anti-parasiticides, anti-inflammatories or drugs to open up the airways may be prescribed as needed. Thankfully in the UK, heartworm (Dirofilaria immitis) is very rare; it is currently only found in dogs that have travelled abroad.
For dogs with significant symptoms of heart failure, your vet may also recommend:
- Diuretics – these help remove excess fluid from the body, easing the strain on the heart.
- Medications to lower pulmonary hypertension – drugs such as sildenafil are sometimes used to reduce the blood pressure in the lungs.
- Oxygen therapy – providing extra oxygen can help dogs breathe more easily and improve their comfort.
- Exercise restriction – limiting strenuous activity can prevent further stress on the heart.
It’s important to note that while treatment can help control symptoms and slow progression, once cor pulmonale has developed, it is typically a chronic condition that requires ongoing management. Regular checkups and monitoring are essential to catch any changes early and make adjustments to therapy as needed.
What is the prognosis?
The outlook for dogs with cor pulmonale is variable. It depends largely on the underlying cause, how early the condition is detected, and how well it responds to treatment. In some cases – such as mild disease caught early and with a treatable underlying cause – dogs can live comfortably for months or even years with appropriate management.
However, when cor pulmonale is severe or associated with advanced heart or lung disease, the prognosis becomes more guarded. Dogs with advanced disease may experience persistent symptoms like difficulty breathing, fainting, or fluid build-up, and may require more intensive management. Quality of life is always a priority, so your veterinarian will work with you to ensure your dog is comfortable and happy for as long as possible, but euthanasia sometimes becomes the kindest option as symptoms worsen.
Conclusion – what dog owners should know
Cor pulmonale is a serious condition, but understanding what it is and how it affects your dog can help you recognise the signs early and get prompt veterinary care. If your dog is diagnosed with a chronic lung condition, be mindful that early treatment of this may slow down or stop the development of cor pulmonale. However, be vigilant for signs getting worse as it may indicate that cor pulmonale has developed. If you notice changes in your dog’s breathing, exercise tolerance, or behaviour, don’t hesitate to reach out to your vet. Early intervention can make a significant difference in both quality of life and the long-term prognosis for dogs with cor pulmonale.
Discussion