1. From the Cardiovascular Engineering, Inc (G.F.M.), Waltham, Mass; Louis Stokes Veterans Affairs Medical Center (M.E.D.), Cleveland, Ohio; Foothills Hospital (W.W.), Calgary, Alberta, Canada; Montreal Heart Institute (A.D., J.-C.T.), Montreal, Quebec, Canada; London Health Sciences Centre (J.M.O.A.), London, Ontario, Canada; Brigham and Women’s Hospital (S.D.S., M.A.P.), Boston, Mass; National Heart, Lung, and Blood Institute (M.J.D.), Bethesda, Md; and Biostatistics Center (K.A.J., M.M.R.), George...