[1] Boston Univ, Div Cardiol, Boston, MA 02215 USA
[2] Emory Univ, Div Cardiol, Atlanta, GA 30322 USA
[3] Univ Calif San Francisco, San Francisco, CA 94143 USA
[4] Univ Pittsburgh, Pittsburgh, PA USA
[5] NIA, Lab Epidemiol Demog & Biometry, NIH, Bethesda, MD 20892 USA
[6] Wake Forest Univ, Winston Salem, NC 27109 USA
[7] Cleveland Clin Fdn, Div Cardiol, Cleveland, OH 44195 USA