RESPONSES OF PLASMA NOREPINEPHRINE AND HEART-RATE DURING EXERCISE IN PATIENTS AFTER FONTAN OPERATION AND PATIENTS WITH RESIDUAL RIGHT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION AFTER DEFINITIVE RECONSTRUCTION

To determine the exercise responses of patients with congenital heart disease, 20 patients-5 who had undergone a right ventricular outflow t ract reconstruction (group R; age, 15 +/- 2 years), eight who had unde rgone a Fontan operation (group F; age, 13 +/- 2 years), and seven who had a history of Kawasaki disease (group C; age, 15 +/- 1 years)-perf ormed a treadmill exercise test. Patients of group R had a significant residual right ventricular outflow obstruction. Oxygen uptake ((V)ove r dot O-2), heart rate (HR), and plasma norepinephrine (NE) concentrat ions were measured at rest, during warm-up, at ventilatory threshold ( VT), and at peak exercise. Exercise capacity was determined as a perce ntage of the predicted normal peak (V)over dot O-2 (%p(V)over dot O-2) . The %p(V)over dot O-2 for groups R and F was 65 +/- 10 and 56 +/- 11 , respectively. Peak HR for groups R and F was 171 +/- 4 and 155 +/- 5 , which were lower than the HR for group C (p < 0.001). Although NE co ncentrations at rest, during warm-up, and at VT were significantly gre ater in groups R and F (p < 0.05), there were no significant differenc es in the NE concentrations at peak exercise. Peak HR correlated with %p(V)over dot O-2 (p < 0.001). The ratio of the increase in HR to NE f rom rest to VT was significantly lower in groups R and F than in group C (p < 0.001) and correlated with %p(V)over dot O-2 (r = 0.80; p < 0. 001). These data suggest that sympathetic nervous activity in groups R and F is increased at rest and during mild to moderate exercises, and reduced sinus node sensitivity to NE may be partly responsible for th e abnormal HR response during exercise of patients with uncorrected co ngenital heart disease.