The Impending ATE in Cats – Is Rivaroxaban the answer?

Arterial thromboembolism (ATE) is one of the most devastating complications of feline cardiomyopathy. It can develop suddenly, even in cats with previously unrecognised heart disease, and often carries a poor prognosis.

Clopidogrel remains a mainstay of feline thromboprophylaxis, with good evidence supporting its use over aspirin for preventing recurrent ATE. But what about cats at particularly high risk, or those that develop a thrombus despite treatment? Could rivaroxaban have a role?

Refer a case

A quick recap: clopidogrel versus rivaroxaban

Although both drugs help reduce thrombotic risk, they work in different ways.

Clopidogrel is an antiplatelet drug that inhibits platelet aggregation by blocking the P2Y12 receptor. In the FAT CAT trial, cats receiving clopidogrel had a longer median time to recurrent ATE than those receiving aspirin (443 versus 192 days).

Rivaroxaban is an oral anticoagulant that directly inhibits factor Xa, reducing thrombin generation and the formation of fibrin, which helps stabilise a blood clot.

In simple terms, they target different parts of the clotting process. Combining them may therefore offer a more comprehensive approach in selected high-risk cats, although the benefits must be balanced against the increased risk of spontaneous bleeding.

When might we consider rivaroxaban?

The main scenarios are cats at particularly high risk of thrombosis and those with an established thrombus or previous ATE.

Risk factors include moderate to severe left atrial enlargement, reduced left atrial function, reduced left atrial appendage blood flow and spontaneous echocardiographic contrast (SEC), sometimes described as ‘smoke’ on echocardiography.

Clopidogrel remains an important first-line option for thromboprophylaxis. However, it does not eliminate risk, and rivaroxaban may be added in selected cats with particularly concerning findings or a history of thromboembolism.

It is important to distinguish prevention from treatment of an acute event. Rivaroxaban helps limit further clot formation; it does not rapidly dissolve an established thrombus. Acute ATE still requires prompt assessment, pain relief and supportive care, alongside management of any concurrent congestive heart failure.

What does the evidence tell us?

The evidence for rivaroxaban in cats is promising, but still limited. A retrospective study of 32 cats receiving clopidogrel and rivaroxaban reported an ATE recurrence rate of 16.7% in cats treated following an ATE event. No new ATE events were reported in cats receiving the combination because of SEC or intracardiac thrombi. However, five cats experienced potential bleeding-related adverse effects, and the study was too small with no control group to establish whether combination treatment was more effective than clopidogrel alone.

A larger 2025 retrospective study examined rivaroxaban use in 66 hospitalised cats. Most received it for confirmed or suspected thrombosis, and cardiac disease was the most common underlying risk factor. Rivaroxaban was generally well tolerated, although potential adverse effects included gastrointestinal bleeding and haemorrhagic pleural effusion.

These findings support further investigation, but they do not establish an optimal protocol or show that every high-risk cat benefits from combination treatment.

Practical considerations: dosing, administration and monitoring

There are a few important points to consider before adding rivaroxaban to the treatment plan.

• Dose: Published guidelines vary suggesting a rivaroxaban dose range of 0.5–1 mg/kg every 24 hours. The SUPERCAT trial used a fixed dose of 2.5mg/cat every 24 hours, which eases compliance as the smallest available tablet size is 2.5mg.
• Palatability: Anyone who has tried to medicate a cat with clopidogrel will appreciate that administration can be a challenge! Rivaroxaban offers a different option, but its tablet formulation can also be difficult to administer. There is currently insufficient evidence to say that cats find it more palatable, but it may be an option for patients who refuse clopidogrel.
• Bleeding risk: Combining an antiplatelet drug with an anticoagulant may increase bleeding risk. Consider concurrent medication, underlying disease and the individual cat’s clinical status.
• Monitoring: Monitor for signs of bleeding, including unexplained bruising, blood in the urine or gastrointestinal bleeding, and reassess the underlying cardiac disease as appropriate. Routine coagulation tests do not reliably quantify rivaroxaban’s effect in every clinical setting.
• Owner communication: Explain that antithrombotic treatment reduces risk but cannot guarantee that a thromboembolic event will not occur. Consistent administration and prompt reporting of potential adverse effects are important.

The take-home message

Rivaroxaban is a useful addition to the feline antithrombotic toolkit, particularly for selected cats at very high risk of thrombosis or those with established thromboembolic disease.

Clopidogrel remains central to our approach, supported by stronger clinical evidence than rivaroxaban monotherapy. For selected patients, combining the two drugs may offer additional protection, but the evidence is still developing and bleeding risk must be considered.

As ever, the aim is to tailor treatment to the individual cat – balancing thrombotic risk, potential adverse effects and what is realistically achievable for the cat and their owner.

References:

Hogan D.F, Fox P.R, Jacob K, et al. (2015). Secondary prevention of cardiogenic arterial thromboembolism in the cat: the double-blind, randomized, positive-controlled feline arterial thromboembolism; clopidogrel vs. aspirin trial (FAT CAT). Journal of Veterinary Cardiology, 17(Suppl 1), S306–S317.

Lo S.T, Walker A.L, Georges C.J, Li R.H.L, Stern JA. (2022). Dual therapy with clopidogrel and rivaroxaban in cats with thromboembolic disease. Journal of Feline Medicine and Surgery, 24(2), 91–100.

Brainard B.M, Coleman A.E, Kurosawa A, et al. (2024). Therapy with clopidogrel or rivaroxaban has equivalent impacts on recurrence of thromboembolism and survival in cats following cardiogenic thromboembolism: the SUPERCAT study. J Am Vet Med Assoc. 2024;263(4):1-10.

Yarsley E, Sharp C.R, Boyd C.J, Seo J, Mooney E. (2025). Indications and outcomes of rivaroxaban use in cats. Frontiers in Veterinary Science, 12, 1561003.

Luis Fuentes V, Abbott J, Chetboul V, et al. (2020). ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. Journal of Veterinary Internal Medicine, 34(3), 1062–1077.

Arcuri, G, Bresolin, P, & Guglielmini, C. (2025). Treatment and Prevention of Cardiogenic Arterial Thromboembolism in the Cat: A Systematic Review. Animals : an open access journal from MDPI, 15(24), 3539.