Atrial natriuretic peptide levels in rheumatic mitral regurgitation and response to angiotensin-converting enzyme inhibitors

BACKGROUND: Rheumatic mitral regurgitation (MR) causes heart failure by volume overload and an increase in atrial natriuretic peptide (ANP) levels by atrial stretching. Symptoms of heart failure improve with ANP treatment. Angiotensin-converting enzyme inhibitors (ACEI) and ANP have similar effects, such as vasodilation, natriuresis and diuresis. OBJECTIVE: To determine ANP levels and response to ACEI treatment in children with rheumatic MR. PATIENTS AND METHODS: Patients with rheumatic MR were divided into two groups: the digoxin group (10 girls, two boys; age range 10 to 18 years, mean 14 +/- 0.72 years; taking digoxin for at least one year) and the control group (eight girls, four boys; age range eight to 17 years, mean 13.5 +/- 0.81 years). None of the patients in either group had symptoms of heart failure. Serum ANP levels, left ventricular systolic functions, and mitral and aortic stroke volumes of both groups were evaluated on admission. The digoxin group was given ACEI and re-evaluated on the 20th day of treatment. RESULTS: At baseline, ANP levels were higher in the digoxin group (27.3 +/- 6.5 pg/100 muL) than in the control group (6.9 +/- 0.9 pg/100 muL) (P<0.05). On the 20th day of treatment, there were no significant differences in the ANP levels of the digoxin (13.2 +/- 6.1 pg/100 mu L) and control groups. There was a significant decrease in ANP levels in the digoxin group between baseline and the 20th day of therapy. Mitral stroke volumes (510.4 +/- 92.8 mL/m(2)) and left ventricular diastolic volume (108 +/- 12 mL/m(2)) in the digoxin group at baseline were higher than those in the control group (315.3 +/- 59.9 mL/m(2) and 82 6.5 mL/m(2), respectively) on admission; on the 20th day of treatment, there were no significant differences in these values. At baseline, aortic stroke volume in the digoxin and control groups were 86.9 +/- 59.1 and 82.9 +/- 28.3 mL/m(2), respectively (P>0.05). On the 20th day of therapy, the aortic stroke volume of digoxin group had increased to 104.7 +/- 70.1 mL/m(2), significantly higher than that of the control group. CONCLUSION: ANP levels are a good indicator of volume overload. ACEI should be introduced at an early stage of rheumatic MR because, even if patients are taking digoxin, their heart failure may progress silently.