[1] Duke Univ, Med Ctr, Duke Clin Res Inst, Ctr Clin & Genet Econ, Durham, NC 27705 USA
[2] Yale New Haven Med Ctr, Div Cardiol, New Haven, CT USA
[3] Georgetown Univ, Med Ctr, Inst Cardiovasc Sci, Div Cardiol, Washington, DC USA
[4] Mayo Clin, Cardiovasc Dis Div, Rochester, MN USA
[5] US Hlth Resources & Serv Adm, Natl Nursing Workforce Unit, US Dept HHS, Rockville, MD USA
[6] Delmarva Fdn Med Care Inc, Easton, MD USA
[7] Maryland HealthCare Associates LLC, Clinton, MD USA
[8] Hlth Care Financing Adm, Baltimore, MD USA