Pulmonary Thromboembolism (PTE) in Dogs and Cats

Sad dog laying down

Pulmonary thromboembolism, often abbreviated “PTE” in veterinary medicine, is a life-threatening, acute blood clot that develops within the lungs. Pulmonary thromboembolism results in difficulty breathing and can occur in both dogs and cats. While rare, PTE can be fatal and result in sudden death.

What causes a pulmonary thromboembolism?
In human medicine, pulmonary thromboembolism is often the result of a deep vein thrombus (often abbreviated “DVT”) that develops somewhere in the blood vessels (veins) of the body. This is one of the reasons why medical doctors will tell you to walk around or use compression socks when you are on a long plane ride. If you develop a DVT, you are at a significantly higher risk of this clot “blowing off” and getting stuck in your lungs, causing a pulmonary embolism.

In veterinary medicine, DVT is less of a common occurrence. That said, we can still see the development of PTE secondary to certain problems within the body.

Animals that are more likely to clot (called a “hypercoagulable”) are predisposed to developing PTE. Typically, this occurs under the following conditions:

  • Animals with heart disease
  • Abnormal blood flow (called “blood stasis”) in the heart vessels
  • Animals on chronic steroids (e.g., prednisone, prednisolone, dexamethasone, etc.)
  • Underlying red blood cell injury (secondary to diseases like immune-mediated hemolytic anemia, etc.)
  • Metabolic problems where there is an abnormally low protein in the body (due to loss through the kidneys, liver, or gastrointestinal tract)
  • Cancer
  • Pancreatitis (i.e., inflammation of the pancreas)
  • Severe inflammation in the body
  • Severe trauma
  • Surgery
  • Numerous other causes

Symptoms of a pulmonary thromboembolism include:

  • Acute, sudden difficulty breathing
  • Constant panting
  • Anxiety, restlessness, pacing
  • An increased respiratory rate > 40 breaths per minute (bpm)
  • Open mouth breathing
  • Blue-tinged gums (which indicates severe difficulty and possibly death if not treated immediately)
  • Stretching the neck out to breathe
  • Sitting up to breathe, with the front legs/elbows spread out (like a English bulldog)
  • Using the abdomen to breathe better (you’ll notice the sides of the belly heaving in and out more)
  • Sudden death

If you notice any of these signs, an immediate trip to the veterinarian or emergency veterinarian is imperative, or death may be imminent.

Diagnosing a pulmonary thromboembolism
Once your pet is at the veterinarian, she’ll probably stabilize your dog or cat with oxygen therapy immediately. Then, diagnostic tests can be run to find out what is going on (as there are numerous causes of difficulty breathing). Some of these tests may include:

  • Blood work (to evaluate the white and red blood cells, platelets, kidney and liver function, electrolytes, and clotting ability)
  • A clotting test (called a d-dimer or FDP/FSP) to look for evidence of a clot somewhere in the body
  • Chest x-rays (to look at the appearance of the trachea, ribs, lungs, diaphragm, etc.). Chest x-rays can range from appearing normal to very abnormal (including small amounts of pleural effusion, abnormal fluid in the lungs, abnormal vessels within the pulmonary vessels, etc.)
  • Abdominal x-rays (to rule out other underlying problems in the abdomen)
  • Monitoring the blood oxygen levels (e.g., with a pulse oximetry [a device that non-invasively monitors how much oxygen is being carried by the red blood cells] or an arterial blood gas sample [taken from the artery])
  • An echocardiogram (an ultrasound of the heart) to rule out congestive heart failure or elevated blood pressure within the lungs
  • CT angiography, which is a dye study performed under anesthesia. This helps highlight where the clot is. However, due to the requirement for anesthesia, it is often a high-risk procedure.

Treatment of a pulmonary thromboembolism
Treatment of PTE includes:

  • Oxygen therapy
  • Supportive care
  • Treating the underlying problem
  • While blood “thinners” such as warfarin, coumadin, or heparin have been used, their successful use is limited in veterinary medicine. Likewise, “clot busting” medication (such as streptokinase or tPA) can also be considered, but life-threatening complications (e.g., severe changes in potassium levels) and costs, limit the use of these medications in veterinary medicine. Currently, the use of low-dose aspirin therapy is commonly used for prevention and treatment.

Recovering from a pulmonary thromboembolism
Ultimately, the prognosis of pulmonary thromboembolism is poor. Unfortunately, even with 24/7 care, animals can succumb and die from PTE. For this reason, it’s important to focus on prevention of the disease. If you notice any clinical signs of breathing problems, seek immediate veterinary attention. The sooner we can diagnose a problem, the sooner we can treat it.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.

Reviewed on: 
Monday, May 19, 2014