Effect of long-term administration of digoxin on exercise performance in chronic airflow obstruction.

We have studied the effect of long-term digoxin on exercise performance in 15 patients with pulmonary heart disease due to severe chronic airflow obstruction (FEV1/VC ratio 29 +/- 6%: mean +/- SD). Digoxin (0.25 mg/day) was given for 8 weeks in a randomized, double-blind crossover, placebo-controlled trial. All patients were ambulatory and had clinical features of right ventricular dysfunction but no clinical evidence of left ventricular dysfunction. Assessments included progressive and steady-state exercise, pulmonary function studies and evaluation of right and left ventricular function. In all patients the right ventricular ejection fraction was reduced; in 4 patients the left ventricular ejection fraction was also reduced. In patients whose left ventricular ejection fraction was initially abnormal, 8 weeks of digoxin increased left ventricular ejection fraction to normal. In spite of the improvement in resting ventricular function, exercise performance, the cardiopulmonary response to exercise, pulmonary function and general health status did not improve. We conclude that in patients with pulmonary heart disease: 1) digoxin improves ventricular function only if left ventricular function is reduced, and 2) despite the improvement in ventricular function digoxin does not improve pulmonary function, cardiopulmonary response to exercise or general feeling of well being.