Aortic thromboembolism (ATE) is a devastating complication of cardiomyopathy in cats. It is one of the most distressing diseases seen in veterinary medicine and often results in euthanasia due to its poor prognosis.    

Thrombus formation is the result of a combination of blood stasis in a dilated left atrium, hypercoagulability and/or endothelial dysfunction. Thrombus most commonly embolises to the terminal aorta, and cats then present with the classic signs of “saddle thrombus”.

Diagnosis of an ATE at the distal aorta can usually be made by physical examination. The 5 P’s of pain, paralysis, pulselessness, poikilothermy and pallor are common findings suggestive of an ATE.

Median survival times of cats that have experienced an acute distal aortic ATE have been reported to be as long as four months. There is a critical need for studies investigating the best therapeutic options for cats to delay or prevent this often-fatal complication in cats with myocardial disease.

It is not yet known whether the best treatment for prevention of ATE in cats is an anti-platelet drug or an anticoagulant. Rivaroxaban is an orally administered anticoagulant that is a direct inhibitor of activated Factor X (FXa) and unlike heparin, it does not require interaction with antithrombin for FXa inhibition.

In addition, rivaroxaban is administered orally once daily, improving owner compliance over anticoagulants like heparin that require frequent injection. Preliminary data on the safety of orally administered rivaroxaban in healthy cats show that it is well-tolerated with minimal side effects.

SUPER-CAT study

The RVC is now recruiting cats for the UK arm of the SUPER-CAT study that is currently ongoing in the United States. The SUPER-CAT study aims to investigate the efficacy of a rivaroxaban compared to clopidogrel (an anti-platelet drug) in preventing the recurrence of ATE.

We are enrolling cats that have experienced one ATE episode and have recovered from the acute syndrome. The goal is to start the study drug between one and four weeks after the initial event. Cats will be randomised to receive one of the two anti-thrombotic medications (clopidogrel or rivaroxaban) and the patient may be prescribed cardiac medications as needed.

Once the acute clinical syndrome has resolved, each cat will require an echocardiogram by a board-certified veterinary cardiologist who will confirm the presence of cardiomyopathy. A re-examination will be required at two, six and twelve months post-enrollment where a full echocardiogram should be repeated.

The owner will receive (free of charge) either rivaroxaban (2.5mg/cat PO q24h) or clopidogrel (18.75mg/cat PO q24h) at two-month intervals by post upon completion of an online survey. All cats will receive the study drug for up to two years as part of this study. The primary endpoint for evaluation is the recurrence of ATE. Please visit cvccr.com for more information about the SUPER-CAT study.

If you have an owner that would be willing to enrol their cat to participate in this study, please contact QMHreception@rvc.ac.uk for the attention of Anne Kurosawa.

SUPER-CAT study inclusion criteria

• One to four weeks after recovery from first episode of ATE
• Body weight ≥2.5 kg
• No significant comorbidities
• Ability to administer regular oral medications