Short-term effects of denopamine on anaerobic threshold and related parameters in patients with chronic heart failure: a double-blind crossover study.
The short-term effects of denopamine, an orally available beta-stimulant, on exercise capacity were studied in patients with chronic heart failure. Nineteen patients entered the study. Three patients had ischemic heart disease, 13 had dilated cardiomyopathy, and three had valvular disease; 16 patients were in New York Heart Association class II, and three patients were in New York Heart Association class III. Symptom-limited exercise testing (ramp protocol) on a bicycle ergometer with gas exchange analysis was conducted 1 hour after oral administration of either 20 mg denopamine or placebo. Drug administration sequence was randomly assigned in a double-blind crossover method, with 1 week between drugs. Peak VO2 was 20.4 +/- 3.2 and 21.2 +/- 3.1 ml/min/kg, respectively, for those administered the placebo and the drug, and anaerobic threshold was 13.1 +/- 2.1 and 14.0 +/- 2.0 ml/min/kg. There was a significant increase in peak VO2 (p < 0.05) and anaerobic threshold (p < 0.01) with denopamine, whereas no significant change was observed in peak work rate or exercise time. Denopamine increased heart rate in patients with atrial fibrillation but had little effect on heart rate in patients with sinus rhythm. Data obtained from gas exchange analysis are more sensitive and potentially more useful in the detection of short-term changes in exercise capacity than data obtained from either exercise time or peak work rate, indexes that are commonly used to assess drug therapy. Patients with mild-to-moderate heart failure with sinus rhythm, but not those with atrial fibrillation because of its frequent induction of tachycardia, may be good candidates for denopamine therapy.