Exercise Tolerance as a Guide to Therapeutic Efficacy for Heart Failure

he early trials of efficacy of therapy for heart failure focused on exercise tolerance as a guide to symptom relief. Patients with heart failure usually seek medical help because of an impairment of their exercise capacity, and it seemed reasonable to use quantitative assessment of this capacity to guide our therapeutic efforts. Indeed, early studies of nitrates1 and of captopril2,3 suggested a significant im- provement in peak exercise capacity when these drugs were added to conventional therapy. The duration of these studies, which were designed to demonstrate short-term improve- ment, was usually 3 to 6 months.