Background: Arterial thromboembolism (ATE) is a common complication of feline cardiomyopathy; however, the pathogenesis of ATE is unknown.
Hypothesis: Systemic activation of the coagulation cascade (hypercoagulability) and endothelial injury promote ATE in cardiomyopathic cats.
Animals: Healthy cats (n = 30) and 3 groups of cardiomyopathic cats: Group (1) left atrial enlargement only (LAE [n = 11]), ie, left atrial to aortic ratio >1.4; Group (2) LAE with spontaneous echocardiographic contrast, atrial thrombi or both (SEC-T [n = 16]); and Group (3) acute ATE with LAE (n = 16).
Methods: Hypercoagulability was defined by 2 or more laboratory abnormalities reflecting coagulation factor excess (high fibrinogen concentration or Factor VIII coagulant activity), inhibitor deficiency (low antithrombin activity), or thrombin generation (high thrombin-antithrombin complex [TAT] and d-dimer concentrations). High von Willebrand factor antigen concentration (vWF : Ag) was considered a marker of endothelial injury. Data were analyzed using nonparametric statistics.
Results: The 3 groups of cats with cardiac disease had higher median fibrinogen concentrations than did the healthy cats. Criteria of hypercoagulability were found exclusively in cats with SEC-T (50%) and ATE (56%). Hypercoagulability was not associated with left atrial size or congestive heart failure (CHF). ATE cats had significantly higher median vWF : Ag concentration than did the other groups.
Conclusion and clinical importance: Systemic hypercoagulability is evident in many cardiomyopathic cats, often without concurrent CHF or overt ATE. Hypercoagulabilty may represent a risk factor for ATE. High vWF : Ag in ATE cats was attributed to downstream endothelial injury from the occlusive thrombus.