1 Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA. Electronic address: hubert.haywoood@duke.edu.
2 Division of Cardiology, Ahmanson-UCLA Cardiomyopathy Center, University of California Los Angeles Medical Center, Los Angeles, California, USA.
3 Division of Cardiology, Duke University Medical Center, Durham, North Carolina, USA.
4 Department of Medicine, University of Mississippi, Jackson, Mississippi, USA.
5 Saint Luke's Mid America Heart Institute, University of Missouri-Kansas City, Kansas City, Missouri, USA; Baylor Scott and White Research Institute, Dallas, Texas, USA.
6 Division of Cardiology, Duke University Medical Center, Durham, North Carolina, USA; Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA. Electronic address: stephen.greene@duke.edu.