1. From the Departments of Cardiology (M.B.T., S.C.V., M.S., J.D.M.B., G.d.P., J.v.O., P.G.A.V., M.A.V.), Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands, and Medical Physiology (M.B.T., M.S., J.D.M.B., M.A.V.), University Medical Center Utrecht, University of Utrecht, Utrecht, Netherlands.