1. Department of Medicine, Ziauddin Medical University, Karachi, Pakistan
2. Department of Medicine, Duke University Medical Center, Durham, North Carolina; Duke Clinical Research Institute, Durham, NC, USA
3. Division of Cardiology, Duke University School of Medicine, Durham, NC, USA
4. Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA
5. Department of Medicine, University of Mississippi, Jackson, Mississippi, USA; Baylor Scott and White Research Institute, Dallas, Tx, USA