Decreased Platelet Function in Cavalier King Charles Spaniels with Mitral Valve Regurgitation

Abstract

With aggregometry, increased platelet activity has been reported in Cavalier King Charles Spaniels (CKCS) without mitral regurgitation (MR). In contrast, dogs with MR have been found to have decreased platelet activity. The purpose of this study was to test an easy bedside test of platelet function (the Platelet Function Analyzer [PFA-100]) to see if it could detect an increase in platelet activity in CKCS without MR and a decrease in platelet activity in CKCS with MR. This study included 101 clinically healthy dogs > 1 year of age: 15 control dogs of different breeds and 86 CKCS. None of the dogs received medication or had a history of bleeding. The PFA-100 evaluates platelet function in anticoagulated whole blood under high shear stress. Results are given as closure times (CT): the time it takes before a platelet plug occludes a hole in a membrane coated by agonists. The CT with collagen and adenosine-diphosphate as agonists was similar in control dogs (median 62 seconds; interquartile interval 55-66 seconds) and CKCS with no or minimal MR (55; 52-64 seconds). The CT was higher in CKCS with mild MR (regurgitant jet occupying 15-50% of the left atrial area) (75; 60-84 seconds; P = .0007) and in CKCS with moderate to severe MR (jet > 50%) (87: 66-102 seconds; P < .0001). CKCS with mild, moderate, and severe, clinically inapparent MR have decreased platelet function. The previous finding of increased platelet reactivity in nonthrombocytopenic CKCS without MR could not be reproduced with the PFA-100 device.

Serum Serotonin Concentrations in Dogs with Degenerative Mitral Valve Disease

“…Also, approximately one-third of CKCS possess macrothrombocytes, 33 and several complex alterations in platelet and hemostatic function have been described in dogs with DMVD. [33][34][35][36][37][38] In CKCS, the ultrastructure of the giant platelets appears normal by electron microscopy, 33 but the actual 5HT content in the dense granules is unknown. Previous studies failed to find a correlation between the presence of macrothrombocytes and DMVD, 37,39 which is consistent with our results indicating that serum 5HT was similarly increased in CKCS regardless of the presence of macrothrombocytes.…”

Computed tomography diagnosis of eight dogs with brain infarction

“…Underlying causes, such as Chiari malformation, altered platelet morphology and heart disease, have been proposed to explain the overrepresentation of CKCS with cerebellar infarction. 10,23,24 MRI is required to diagnose Chiari-like malformations and further investigation of a potential pathophysiological link with these conditions remains to be done. Cerebellar infarction is a reported potential sequela to both meningioma and heart disease, which were found in two dogs.…”

Results of Diagnostic Investigations and Long-Term Outcome of 33 Dogs with Brain Infarction (2000-2004)

“…The reasons for overrepresentation of CKCS are unclear but may be due to the prevalence of heart disease, alterations in coagulation and platelet morphology, connective tissue pathology, or anatomic variation (ie, Chiari malformation) recognized in this breed. CKCS have a high prevalence of mitral valve regurgitation, as well as platelet abnormalities, 40 which might predispose them to cardioembolic infarction. Cavalier King Charles Spaniels also have a high prevalence of Chiari type malformation, 41 which may alter vertebral-basilar blood flow and predispose them to strokes.…”