1. From the Departments of Clinical Physiology (O.T.R.), Medicine (T.R., J.S.A.V.), Research Centre of Applied and Preventive Cardiovascular Medicine (M.J.J, T.K, I.V., K.K., H.L.), and Pediatrics (H.N., O.S.), University of Turku, Turku, Finland, and Hospital for Children and Adolescents (E.J.), University of Helsinki, Helsinki, Finland.