PLASMA-CONCENTRATION OF ATRIAL-NATRIURETIC-PEPTIDE IN RELATION TO SEVERITY OF MITRAL REGURGITATION IN CAVALIER-KING-CHARLES-SPANIELS

Plasma concentration of immunoreactive atrial natriuretic peptide (ir- ANP) was investigated in 83 Cavalier King Charles Spaniels with variab le severity of mitral regurgitation caused by chronic valvular disease (CVD). Severity of mitral incompetence was assessed by echocardiograp hy. Significant differences in plasma concentrations of ir-ANP were no t found between clinically normal dogs (New York Heart Association fun ctional class O), dogs with only cardiac murmur (class I), and dogs wi th echocardiographic evidence of slight to moderate left atrial and ve ntricular dilatation (class II), Dogs with severe left atrial and vent ricular dilatation and clinical signs of congestion (classes III and I V) were found to have significantly (P < 0.001) increased plasma conce ntration of ir-ANP. Overall, moderate degree of association was found between plasma concentration of ir-ANP and left atrial and left ventri cular diameters (Pearson's r 0.65, 0.60, respectively, P < 0.001), as well as heart rate (r = 0.47, P < 0.01). However, left atrial enlargem ent was found to have the predominant effect on plasma ir-ANP concentr ation. It is concluded that the plasma concentration of ir-ANP did not become markedly increased before decompensation of chronic mitral reg urgitation associated with severe enlargement of the left atrium and v entricle in Cavalier King Charles Spaniels.