Reduced Plasma Cardiac Myosin-Binding Protein-C Concentrations in Cats with Hypertrophic Cardiomyopathy: Evidence from Chronic, Treated Disease

Hypertrophic cardiomyopathy (HCM), the most common cardiac disease in cats, is associated with genetic variants, including MYBPC3, which encodes cardiac myosin-binding protein C (cMyBP-C), a key sarcomeric protein involved in myocardial contractility. Although circulating cMyBP-C has emerged as a biomarker of myocardial injury in humans, its clinical relevance in feline HCM remains unclear. This study characterized plasma cMyBP-C and N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations across different stages of feline HCM, evaluated their diagnostic performance, and assessed their associations with echocardiographic parameters. A cross-sectional study included 65 cats: 25 healthy cats, 25 with subclinical HCM, and 15 with clinical HCM (chronic and treated). Plasma NT-proBNP was significantly higher in clinical HCM than in healthy cats (p = 0.0117), whereas plasma cMyBP-C was lower in clinical HCM than in subclinical HCM (p = 0.0462) and healthy cats (p = 0.001). At a cut-off of <1.270 ng/mL, plasma cMyBP-C showed 76.19% sensitivity and 65.38% specificity for distinguishing HCM. NT-proBNP alone showed higher overall diagnostic accuracy (76.67%) than the combined use of cMyBP-C and NT-proBNP. Neither plasma NT-proBNP nor cMyBP-C correlated significantly with echocardiographic parameters. Reduced circulating cMyBP-C concentrations in cats with chronic, treated HCM suggest a biomarker pattern distinct from that reported in acute myocardial injury and warrant further investigation.