Animals suffering from PTE will often appear to be distressed and have sudden difficulty breathing. This condition is rare, but can be life threatening. Owners who suspect that their cat may be suffering from a blood clot in the lung should seek veterinary help immediately.

The clinical name for blood clots in the lung is pulmonary thromboembolism (PTE). When a blood clot becomes lodged in the arterial network leading to the lungs, it prevents oxygenated blood from reaching the lung. The severity of the condition often depends on the size of the clot.

Affected cats may behave normally until they suddenly experience respiratory difficulty. Blockages are often very painful, and the animal may vocalize its discomfort or collapse. Other symptoms include:

Although it is not a common condition, blood clots in the lungs can affect cats of any age. Studies have shown that it is more common in cats under four years of age and over ten years of age, and less common in middle-aged cats. The condition has an equal chance of occurring in both males and females. It is usually secondary to another severe disease such as:

Blood clots can also be caused by chronic use of steroids such as prednisone.

Initial diagnosis is typically done through a thorough physical exam by a veterinarian. He or she will listen for abnormal sounds such as a heart murmur and examine the cat for other signs of heart failure. It will be important for owners to provide a thorough history of the animal’s health and discuss with the veterinarian any previous symptoms and circumstances that may have led to the onset of the condition.

Laboratory tests including a blood profile, blood count analysis, urinalysis, or electrolyte panel will often be performed in an effort to diagnose the condition. One or more imaging tests may also be performed to make a visual diagnosis. X-rays may be used to check for heart enlargement, accumulation of fluid in the chest, or indicators of decreased blood flow to affected areas. X-rays or ultrasound images may also show bleeding in the lungs, tissue damage, or other abnormalities. 

An echocardiogram is currently the standard test for evaluating heart function in cats. Unfortunately, the test can take up to 30 minutes to complete and the cat must be manually restrained during the procedure. The stress and anxiety that this causes can often exacerbate the condition. Studies are currently underway to determine whether CT scans are effective for diagnosis. This test takes around 5 minutes and is much less stressful for pets.

Once a cat has experienced blood clots in the lungs, treatment is typically limited to supportive care.

The first thing that a vet will typically do is provide the cat with oxygen therapy to relieve the immediate symptoms. Affected animals will likely receive pain control treatments and be placed in a cage so that they receive the physical rest needed. The minimization of stress will also be critical to the chances for recovery.

It’s very rare for a cat to present with a blood clot in the lungs without suffering from other diseases. Diagnosing and treating the underlying cause is necessary for a chance at recovery. 

In some cases, blood-thinning medications may be used to treat and prevent additional clotting. The use of anticoagulant drugs can be dangerous as blood may become too thin and cause new health problems. The drug heparin has been used with limited success. It is safer than some other medications but is also much more expensive. 

In rare cases, surgery may be performed to remove the clot. This is not a common treatment due to the limited chance of success and high risk of fatality.

Unfortunately, blood clots in the lung are often fatal in cats. The condition is often extremely painful and has a poor prognosis. For this reason, 90% of affected cats are euthanized. Those that are hospitalized and receive medical treatments usually have a 30 to 40 percent survival rate.

If a cat survives a blood clot in the lung, it is likely that the condition will reoccur unless the underlying cause is discovered and corrected. Weekly monitoring check-ups with a qualified veterinarian will be necessary to monitor the cat’s health and quickly address any issues of reoccurrence. In some cases, physical therapy or vet-recommended exercise may help to increase blood flow and avoid additional blood clots.