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 nitrotyrosine concentration in dogs with myxomatous mitral valve disease

“…In another study, platelet counts were significantly higher in the moderate to severe MMVD group than in the mild MMVD group [20]. Those results are similar to our results in which a significant negative correlation was observed between platelet count and serum nitrotyrosine concentrations.…”

Assessment of hemostatic changes in a model of acute hemorrhage in dogs

“…While platelet dysfunction has been described previously in dogs with chronic valvular disease, this is the first description of platelet dysfunction associated with acute hemorrhage . In dogs with cardiac disease secondary to valvular insufficiency, chronic stress, and stimulation of platelets associated with the cardiac disease is thought to lead to platelet exhaustion .…”

Serum Serotonin Concentrations in Dogs with Degenerative Mitral Valve Disease

“…Thus, the hypothesis that canine valve injury may attract circulating platelets, which subsequently release 5HT and increase local 5HT signaling warrants further investigation. 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 33–38 . 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.…”