This study aimed to assess the potential role and safety of dobutamine stress echocardiography (DSE) in the evaluation of cardiac reserve in asymptomatic patients several years after a Fontan operation.We studied 10 asymptomatic patients, 28 +/- 5 years old, 14 +/- 6 years after their Fontan operation. All patients and 10 healthy, matched controls underwent two-dimensional and Doppler echocardiography at baseline and throughout dobutamine infusion (given in 3-minute increments of 5, 10, 20, 30, and 40 microg/kg/min). Multivariate analysis for repeated measurements was used to detect differences between patients and controls.There were no adverse events during dobutamine infusion. Heart rate increased appropriately in both patients and controls. Patients reached peak stroke volume at infusion rates of 20 microg/kg/min, whereas controls peaked at 10 microg/kg/min. Mean stroke volume, cardiac output and cardiac index were significantly different between the two groups only up to infusion rates of 10 microg/kg/min. The velocity time integral of the left ventricular outflow tract flow was significantly lower in patients than controls throughout the study.DSE is a safe method of stress testing for the assessment of adult Fontan patients and provides insights into the pathophysiology of their cardiac performance. Cardiac reserve in these patients is impaired compared to healthy controls.