Digoxin serum levels in patients with Chagas' cardiomyopathy and heart failure.

INTRODUCTION The purpose of this study was to determine digoxin serum concentrations in patients with Chagas' cardiomyopathy with chronic heart failure, because little is known concerning this laboratory test in patients with this condition. METHODS This study focuses on 29 (29%) out of 101 patients with chronic heart failure secondary to Chagas' cardiomyopathy receiving digoxin therapy. Digoxin was measured by the immune-enzymatic method. RESULTS New York Heart Association Functional Class III/IV was noted in 13 (45%) patients. The mean potassium serum level was 4.3 ± 0.5 mEq/L, mean creatinine serum levels 1.4± 0.3dg/100ml, and left ventricular ejection fraction 34.7 ± 13.8%. The median digoxin serum level was 1.27 (0.55; 1.79)ng/ml. Sixteen (55%) patients had digoxin serum levels higher than 1.0 ng/ml. Abnormal digoxin serum levels were verified in 13 (45%) patients. Digoxin serum levels correlated moderately with creatinine serum levels (r = 0.39; p < 0.03) and negatively with sodium serum levels (r= -0.38; p= 0.03). CONCLUSIONS Digoxin serum concentration should be measured in patients with Chagas' cardiomyopathy with chronic heart failure receiving digoxin therapy due to the potential for digoxin toxicity.