Vet Speak By Alison Laurie-Chalmers: Distressing blood clot trauma needs immediate action
Minty was a lovely black and white striped cat. He was rushed in and admitted urgently as an emergency case to the main surgery. He was in shock and in severe pain, and he couldn’t stand up on either of his hind legs. He was admitted for immediate pain relief and tests which revealed that “Minty” had a saddle thromboembolism, blocking the blood supply to his back legs.
“Saddle thromboembolism” is a life-threatening condition that occurs when a blood clot, or embolus, breaks away from a larger clot, a thrombus, within the heart and travels down the aorta. It then lodges itself at the junction of the iliac arteries of the hind legs, blocking blood flow to one or both hind limbs.
In some cases, if the clot is small, it may travel past this junction and lodge in a smaller back-leg artery. In this case, symptoms can appear in just one leg. Blood clots can also travel to other parts of the body.
The most common underlying cause of a saddle thrombus is a known, or an undiagnosed, heart disease. Studies show that between 69-90 per cent of cats with thromboembolism have an underlying heart disease.
Saddle thrombosis can develop in cats of any age or breed; one study found the mean age was 12 years..
Saddle thromboembolism is a distressing and devastating condition, as often there is little or no warning.
The symptoms are: sudden and acute, severe pain, with distressed howling and vocalisation noted; frantic licking or chewing at the affected legs; paralysis or weakness of the hind limbs, being unable to stand or dragging one or both back legs; firm, painful hind limb muscles; loss of a pulse in the affected limbs; cold hind limbs; blueish tinged skin and pads noted on the affected limbs; and pale gums, as these patients are in severe shock.
Once blocked, blood can no longer pass into the iliac arteries, depriving the hind legs of oxygen. A cascade of biochemical reactions within the cells follows, leading to toxic by-products that are released back into the circulatory system.
Aortic thromboembolism is a critical medical emergency and requires immediate veterinary attention.
Blood tests will reveal any blood abnormalities, and an ultrasound scan an abdominal doppler ultrasound may reveal the embolism and visualise the lack of blood flow. A cardiac scan may reveal cardiac abnormalities.
These are really distressing cases, and sadly, many cats don’t survive a saddle thromboembolism. The required blood thinners and thrombolytics run the risk of causing other bleeding. Often the underlying problem is a thrombus within the heart which splits off further emboli, and so any invasive surgery is usually not advised, or possible.
Even if the cat recovers from the initial event, the risk of another clot forming is then extremely high. On top of that there is usually an underlying severe heart condition. Many owners elect to euthanise cats due to the severe shock and pain that they go through, and the poor outcome and prognosis for these cases.
Minty was 13, and it was found during his tests that he also had a severe, underlying cardiac condition. After hearing this, his owners decided it was kinder to give him a gentle release from this condition, rather than risk him having further clots and go through this trauma again. Minty was quietly put to rest. It was very sad, however, his owners were relieved that he would not go through any further pain and suffering, and they remembered the many happy years they had with him.
• Alison Laurie-Chalmers is a senior consultant at Crown Vets
