1. Department of Medicine, University of Mississippi, Jackson, MS 39216, USA
2. Department of Medicine, Dow University of Health Sciences, Karachi, 74200, Pakistan
3. Department of Medicine, Ziauddin Medical University, Karachi, 7500, Pakistan
4. Medical College, Aga Khan University, Karachi, 74800, Pakistan
5. Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA