EFFECTS OF NATURALLY ACQUIRED DECOMPENSATED MITRAL-VALVE REGURGITATION ON THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM AND ATRIAL-NATRIURETIC-PEPTIDE CONCENTRATION IN DOGS

Objective-To investigate activity of the renin-angiotensin-aldosterone system and N-terminal pro-atrial natriuretic peptide (NT-proANP) duri ng development of clinical signs of decompensated mitral valve regurgi tation (MR). Animals-11 Cavalier King Charles Spaniels with advanced M R attributable to chronic valvular disease. Procedure-Dogs were subjec ted to repeated examinations at 6-month intervals until signs of decom pensation had developed (end point). Data acquired at end point were c ompared with data obtained from examinations 1 year and 1 to 6 months before decompensation. Each examination included physical examination, collection of venous blood, thoracic radiography, and echocardiograph y. Results-Echocardiographic measurements of left atrial-to-aortic roo t ratio and left ventricular end diastolic diameter increased consider ably during the study, whereas left ventricular end systolic diameter remained unchanged. The increase in cardiac size was associated with i ncreased plasma concentration of NT-proANP. In contrast, plasma concen trations of aldosterone and angiotensin II were reduced al decompensat ion (aldosterone compared with the 2 earlier examinations and angioten sin II compared with values obtained 1 to 6 months before), despite de creased plasma protein concentration and hematocrit, suggesting fluid retention. The urine-to-plasma creatinine ratio was reduced at end poi nt. Conclusion and Clinical implications-Early decompensated MR in dog s was not associated with increased circulating renin-angiotensin-aldo sterone system activity, which may be caused by increased activity of ANP, and may be important for future therapeutic strategies of MR.