EFFECT OF DIGOXIN ON EXERCISE PERFORMANCE IN MILDLY SYMPTOMATIC PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY AND SINUS RHYTHM

The purpose of this investigation was to evaluate the effect of digoxi n on aerobic performance in mildly symptomatic patients with congestiv e heart failure and sinus rhythm. Ten patients (8 men and 2 women) wit h idiopathic dilated cardiomyopathy (ejection fraction 17 to 33%, mean 27 +/- 4%) who were stable and mildly symptomatic with maintenance di goxin and diuretic therapy were studied. All patients underwent maxima l symptom-limited ergometer exercise with analysis of respiratory gase s during maintenance digoxin therapy, 4 weeks after digoxin withdrawal , and 4 weeks after digoxin readministration. Exercise capacity was as sessed by peak oxygen uptake and anaerobic threshold. Serum digoxin co ncentration was 1.0 to 1.8 mean 1.3 +/- 0.2) ng/ml during digoxin ther apy, and less than the detectable level after digoxin withdrawal. No p atients showed clinical deterioration after digoxin withdrawal. Peak o xygen uptake after digoxin withdrawal (23.7 +/- 3.0 ml/kg/min) did not differ significantly from that during maintenance digoxin therapy (23 .8 +/- 2.5 ml/kg/min) or after digoxin readministration (24.1 +/- 2.9 ml/kg/min). The anaerobic threshold after digoxin withdrawal (14.9 +/- 2.5 ml/kg/min) did not differ significantly from that during, mainten ance digoxin therapy (15.0 +/- 2.1 ml/kg/min) or after digoxin readmin istration (14.9 +/- 2.2 ml/kg/min). No differences in heart rate and d iastolic blood pressure were observed during exercise, but systolic bl ood pressure during exercise was significantly higher with digoxin the rapy (p < 0.05). These results suggest that digoxin has no effect on a erobic performance in mildly symptomatic patients with idiopathic dila ted cardiomyopathy and sinus rhythm.