Assessment of changes in hemostatic markers in Cavalier King Charles Spaniels with myxomatous mitral valve disease.

Objective: To evaluate markers of hemostasis and their relationship to the degree of mitral regurgitation (MR) and platelet function in Cavalier King Charles Spaniels (CKCSs) with myxomatous mitral valve disease.
Animals: 76 clinically healthy CKCSs and 24 control dogs.
Procedure: All dogs underwent echocardiographic examination; various hemostatic, hematologic, and biochemical variables were evaluated in blood. The CKCSs were allocated to 1 of 3 groups on the basis of MR severity. In 8 control dogs and 8 CKCSs, plasma von Willebrand factor (vWF) multimer analysis was performed.
Results: Compared with control dogs, plasma fibrinogen concentration was higher in all CKCSs and related to left ventricular end diastolic diameter and left atrial-to-aortic root ratio among all CKCSs. The activated partial thromboplastin times and plasma D-dimer concentration were similar among the 4 groups. Plasma vWF concentration was lower in CKCSs with moderate to severe MR, compared with that of CKCSs with no MR and control dogs. There was a relationship between plasma vWF concentration and platelet function in CKCSs but not in control dogs. In 4 CKCSs with moderate to severe MR and low plasma vWF concentration, amounts of vWF high-molecular-weight multimers (HMWMs) were low.
Conclusions and Clinical Relevance: In CKCSs, MR appeared to be associated with a low plasma vWF concentration and likely a loss of vWF HMWMs (possibly through their destruction via shear stress to the blood). The importance of the changes in plasma fibrinogen concentration and the thromboembolic risk in dogs with MR remain to be investigated.