Systematic Review of the Antiplatelet Effects of Acetylsalicylic Acid and Clopidogrel in Cats with Hypertrophic Cardiomyopathy

Cats with underlying heart disease have a significant increased risk of developing an arterial thromboembolism (atE). Especially cats with hypertrophic cardiomyopathy (HCM) are at risk to develop an atE. acetylsalicylic acid (aspirin ®) therapy has been advised as thromboprophylaxis for many years. More recently however, the prophylac- tic use of clopidogrel has gained more scientific interest.

The aim of this literature study was to evaluate the epidemiology of atE and the in vitro and in vivo effects of thromboprophylactic therapy with acetylsalicylic acid and clopi- dogrel in feline HCM patients.

The true incidence of atE in cats with HCM is unknown. over the past decades, acetylsali- cylic acid has been given as a prophylactic therapy in high (up to 25 mg/kg/q72h) and low dosages (as low as 5 mg/kg/q72h). Studies showed recurrence rates between 25 and 75 % and no significant difference in recurrence rate between low and high dose aspirin therapy. in high dosages (≥25mg/kg/q72h), aspirin can give toxic side effects in cats and therefore high dose aspirin therapy is no longer advised. platelet aggregation studies, reveal that a dose of at least 25 mg/kg is needed to inhibit in vitro arachidonic acid dependent and col- lagen induced platelet aggregation. aDp and thrombin induced platelet aggregation were not inhibited in this high dose. the recurrence rate in cats treated with clopidogrel is still unknown. recently, a small platelet aggregation study showed good in vitro antiplatelet effects of clopidogrel in healthy cats. in a dose of 18,75 mg/kg/day clopidogrel showed sig- nificant reduction of platelet aggregation in response to aDp and collagen.

The results of this literature study support the conclusion that prophylactic low dose acetylsalicylic acid therapy (5 mg/kg/q72h) will not prevent intra-cardiac thrombus for- mation or atE in feline HCM patients. Clopidogrel® seems a promising prophylactic antiplatelet drug, but further research is warranted.