1. Keele Cardiovascular Research Group, Center for Prognosis Research, Institute of Primary Care and Health Sciences, University of Keele, Stoke-on-Trent, United Kingdom.
2. Academic Unit of Obstetrics and Gynecology, University Hospital of North Midlands, Stoke-on-Trent, United Kingdom.
3. Academic Department of Cardiology, University Hospital of North Midlands, Stoke-on-Trent, United Kingdom.
4. Division of Cardiology, University of Arizona, Phoenix, Arizona.