[1] Stanford Univ, Dept Med, Sch Med, Div Cardiovasc Med, HRP Redwood Bldg,T150A,150 Governors Lane, Stanford, CA 94305 USA
[2] Stanford Univ, Ctr Hlth Policy, Stanford, CA 94305 USA
[3] Stanford Univ, Dept Med, Ctr Primary Care & Outcomes Res, Stanford, CA 94305 USA
[4] Vet Affairs Palo Alto Hlth Care Syst, Palo Alto, CA USA