EFFECTS OF INCREASING MAINTENANCE DOSE OF DIGOXIN ON LEFT-VENTRICULAR FUNCTION AND NEUROHORMONES IN PATIENTS WITH CHRONIC HEART-FAILURE TREATED WITH DIURETICS AND ANGIOTENSIN-CONVERTING ENZYME-INHIBITORS

Background Despite almost three centuries of use, the appropriate dosage of digitalis in patients with chronic heart failure and normal sinus rhythm has not been well studied. Methods and Results We studied 22 patients with heart failure who were receiving constant daily doses of digoxin, diuretics; and angiotensin-converting enzyme (ACE) inhibitors. In 18 patients, the oral daily dose of digoxin was increased from a mean of 0.20+/-0.07 to 0.39+/-0.11 mg/day corresponding to an increase in the serum digoxin concentration from 0.67+/-0.22 to 1.22+/-0.35 ng/mL. Radionuclide and echocardiographic left ventricular ejection fraction; maximal treadmill time; heart failure score; serum concentrations df norepinephrine, aldosterone, atrial natriuretic factor, and antidiuretic hormone; and plasma renin activity were obtained before and after the increase in digoxin dose. Subsequently, 9 patients were randomized to receive digoxin and 9 to receive placebo and radionuclide ejection fraction measured after 12 weeks. With the higher dose of digoxin compared with the lower dose, there was a significant increase in radionuclide ejection fraction from 23.7+/-9.6% to 27.1+/-11.8% (P=.007). No significant changes were noted in heart failure score exercise tolerance; serum concentrations of norepinephrine, atrial natriuretic factor, and antidiuretic hormone; and plasma renin activity. There was, however, an increase in serum aldosterone concentration. Twelve weeks after the patients were randomized to receive digoxin or placebo, there was a significant decrease in ejection fraction (from 29.4+/-10.4% to 23.7+/-8.9%) in the placebo group but not in patients who continued to receive digoxin (P=.002). Conclusions The increase in maintenance digoxin dose, while maintaining serum concentrations Within therapeutic range, resulted in a significant increase in left ventricular ejection fraction that was not associated with significant changes in heart failure score, exercise tolerance, and neurohumoral profile.