We have previously shown in a double-blind crossover study that digitalis could be discountinued for three months without adverse clinical effect and only minor changes in cardiac size and function in 30 subjects with stable congestive heart failure (CHF) and sinus rhythm. To assess the ability of maintenance digoxin therapy to improve exercise tolerance in patients with stable CHF, systolic dysfunction and sinus rhythm, we performed maximal treadmill exercise tests in 12 such individuals while monitoring respiratory gas exchange. No difference in exercise duratin, maximal oxygen consumption (VO2max), maximal heart rate, or ventilation was found after 4 weeks of digoxin versus 4 weeks of placebo in a randomized crossover study. During maximal upright bicycle exercise, however, digoxin increased ejection fraction of .26 to .31 despite identical exercise tolerance. Our group has initiated the development of a questionnaire in conjunction with experts in cardiology at different universities to sample representative groups of academic and practicing physicians in their current use and understanding of the effectiveness and toxicity of digitalis glycosides. Among 2704 questionnaire respondents diuretics alone were considered the best initial therapy for CHF in 50%, digitalis alone by 8% and the combination in 33%. Two thirds of the sample felt that digitalis improved exercise tolerance. Thus, despite growing evidence that digitalis glycosides can be successfully withdrawn from patients with chronic stable CHF, there is widespread belief that these drugs are effective in most CHF patients.
