Relationship between different natriuretic peptides and severity of naturally acquired mitral regurgitation in dogs with chronic myxomatous valve disease.

OBJECTIVE: To study the responses of atrial natriuretic peptide (ANP), N-terminal fragment of pro-atrial natriuretic peptide (NT-proANP) and brain natriuretic peptide (BNP) to varying severity of mitral regurgitation (MR) in dogs with myxomatous valve disease (MVD).
DESIGN: Case-control. DOGS: 103 Cavalier King Charles Spaniels, 27 normal individuals and 76 with varying degree of MR. PROCEDURE: Dogs were evaluated by physical examination, collection of venous blood, thoracic radiography and echocardiography. NT-proANP, ANP and BNP were measured in plasma using radio immunoassay (RIA).
RESULTS: The mean concentrations of NT-proANP were 37.4 and 83.5 times higher than ANP and BNP, respectively. The mean ANP to BNP molar ratio was 2.6. Plasma concentrations of NT-proANP and ANP were slightly increased in asymptomatic dogs with increased cardiac dimensions; those with signs of decompensated heart failure (HF) had mean concentrations of NT-proANP and ANP 3 to 7 times higher than normal dogs. The BNP concentrations were increased only in dogs with decompensated HF and the levels were approximately twice as high in these dogs as in normal individuals. Univariate and multiple regression analysis showed that primarily left atrial and ventricular size influenced the plasma concentrations of all 3 peptides (increased with increasing measurement). Analyses of response operating characteristic (ROC) curves indicated that NT-proANP and ANP were more discriminating than BNP for either cardiomegaly of HF. CLINICAL IMPLICATIONS: Natriuretic peptides, particularly NT-proANP and ANP, may be of benefit in the overall assessment of dogs with naturally occurring MR. Analysis of NT-proANP may be more useful than ANP owing to easier handling of the samples and less laborious assay.