From the Departments of Medicine and Radiology (J.M.C., J.C.W.), Bioengineering (G.L.M.), and Genetics (M.P.S.), Stanford Cardiovascular Institute (J.M.C., J.C.W.), Institute of Stem Cell Biology and Regenerative Medicine (J.M.C., G.L.M., J.C.W.), Stanford University School of Medicine, Stanford, CA. (At 2013-06-07)