Serum Serotonin Concentrat ions in Dogs with Degenerative Mitral Valve Disease

Background: Increased serotonin (5HT) signaling has been implicated in valvular disease of humans and animals, including canine degenerative mitral valve disease (DMVD). High circulating 5HT concentration is a potential source of increased sig-naling, and serum 5HT concentrations have not been previously reported in dogs with DMVD. Hypothesis: Dogs with DMVD and small breed dogs predisposed to DMVD have higher serum 5HT concentrations than large breed controls. Animals: Fifty dogs affected with DMVD, 34 dogs predisposed to DMVD but without cardiac murmur or echocardio-graphic evidence of DMVD, and 36 healthy large breed control dogs. Methods: Prospective analysis. Serum 5HT concentration was measured by an ELISA test. Results: Median serum 5HT concentration was significantly higher in dogs with DMVD and in dogs predisposed to DMVD as compared with controls (DMVD, 765.5 ng/mL [interquartile range, 561.3–944.4]; predisposed, 774.9 ng/mL [528.3–1,026]; control, 509.8 ng/mL [320.8–708.8]; P 5.0001). Subgroup analysis of predisposed dogs indicated significantly higher serum 5HT concentrations in Cavalier King Charles Spaniel (CKCS) dogs than in other breeds (CKCS, 855.0 ng/mL [635.8–1,088]; non-CKCS, 554.2 ng/mL [380.6–648.4]; P5.0023). Age, platelet count, and platelet morphology were not correlated with 5HT concentration in any group. Conclusions and Clinical Importance: Dogs with DMVD had significantly higher serum 5HT concentrations when com