OBJECTIVES

Atrial Natriuretic Peptide (ANP) is mainly released from atrial myocytes in response to an increase in right or left atrial pressure. Brain Natriuretic Peptide (BNP) is secreted predominantly by left ventricular myocytes secondary to volume expansion or pressure overload. The aim of this study was to evaluate the diagnostic accuracy of plasma level of both cardiac natriuretic peptides to detect asymptomatic left ventricular alterations in a dog model of dilated cardiomyopathy, i.e., the Golden Retriever Muscular Dystrophy (GRMD). GRMD cardiomyopathy is related to a spontaneous X-linked mutation of dystrophin gene, and is characterized by myocardial necrosis, mineralization and fibrosis, leading to late progressive left ventricular dysfunction and then heart failure.

MATERIALS

50 dogs (12 ± 2 months old, 17 ± 1 kg), including 17 controls with a normal genotype and 33 animals with proven X-linked muscular dystrophy but without any sign of heart failure, were studied. The levels of plasma BNP and ANP were determined by radioimmunoassay. Left ventricular end-diastolic diameter (LVDD), left ventricular end-systolic diameter (LVSD), left ventricular ejection fraction (EF), left ventricular free-wall (LVFW%) and interventricular septal (IVS%) thickening were determined by conventional echocardiography using 2D-guided M-mode. Cardiac peptide plasma levels and echographic parameters were compared between GRMD and control dogs using a t-student test. A p value < 0.05 was considered as statistically significant.

RESULTS

GRMD and controls were comparable regarding conventional echographic parameters: left ventricular diameters (LVDD: 36±2 vs 38±2 mm and LVSD: 25±2 vs 23±2 mm respectively, p=ns), EF (64±3 vs 71±2 %, p=ns), LVFW% (57±5 vs 66±5 %, p=ns) and IVS% (63±6 vs 60±8 %, p=ns). No significant difference between GRMD and controls was observed on ANP plasma level (76±7 vs 76±10 pg/mL respectively, p<0.05). Conversely, BNP plasma level was significantly higher in the GRMD group than in the control group (80±15 vs 31±3 pg/mL respectively, p<0.05), and BNP plasma level was significantly increased in older (over 6 months) than in younger (under 6 months) dystrophin mutant dogs (100±20 vs 45±21 pg/mL respectively, p<0.05).

CONCLUSION

These results show that BNP, and not ANP plasma level, may be a useful biochemical marker of asymptomatic left ventricular dysfunction in GRMD dogs despite preserved conventional indices of myocardial function.