[1] Brigham & Womens Hosp, Div Cardiovasc, Boston, MA 02115 USA
[2] Harvard Univ, Sch Med, Dept Med, Boston, MA 02115 USA
[3] George Washington Univ, Rockville, MD USA
[4] George Washington Univ, Washington, DC 20052 USA
[5] Univ Calgary, Dept Cardiac Sci, Calgary, AB T2N 1N4, Canada
[6] NHLBI, Bethesda, MD 20892 USA
[7] Mayo Clin & Mayo Fdn, Rochester, MN 55905 USA
[8] Childrens Hosp, Dept Lab Med & Pathol, Boston, MA 02115 USA