Feline arterial thromboembolism (ATE) is a serious complication typically associated with cardiac disease in cats. A 5-17% incidence has been reported in cats with cardiac disease. It is believed that an enlarged left atrium is a risk factor for ATE, however the disease has also been reported in cats without cardiac disease.
Common signs resulting from ATE include acute onset paralysis and pain. Most commonly the hind limbs are affected, however thrombembolism can also affect the forelimbs, and in some cases, result in neurological signs.
The prognosis for cats with ATE is guarded, with a mortality rate of 61-67%. Prognosis is largely dependent on the severity of signs at presentation and at least 50% of patients are euthanized. Typically ATE is associated with a high rate of recurrence of 35-50% within one year. Long term survival has been reported to be between 51 to 471 days.
Recently, a study conducted by veterinary cardiologists at Purdue University evaluated the efficacy of two medications, clopidogrel (Plavix) and aspirin, in preventing the recurrence of ATE. Clopidogrel is an antithrombotic drug that specifically targets platelets. Cats previously diagnosed with a thromboembolic event were administered 18.75mg of clopidogrel once daily, or 81mg of aspirin every 3 days. The study evaluated whether a thromboembolic event had occurred within one year and whether the patient had any adverse effects from the medication. The study found that there was a significant improvement in survival in patients receiving clopidogrel, with these cats surviving 8 months longer than cats receiving aspirin. Elevated liver enzymes were appreciated in one cat receiving clopidogrel, otherwise the medication was well tolerated.
Overall, this study is strongly supportive of the use of clopidogrel over aspirin for prevention of recurrence of feline ATE. However, the study did not evaluate the use of clopidogrel with other medications such as low molecular weight heparin, and whether this treatment modality may provide further improved benefits without complications from excessive anticoagulation. These studies are currently ongoing.
The following update was a summary from the ACVIM 2013 proceedings. All statistical data reported was obtained from the proceedings report and oral presentation.
Hogan, D et al. Analysis of the Feline Arterial Thromboembolism: Clopidogrel vs Aspirin Trial (Fat Cat). Proceedings, ACVIM 2013.