1. Department of Medicine (Cardiology), University of Pittsburgh , Pittsburgh, PA 15261, United States
2. University of Pittsburgh Medical Center , Pittsburgh, PA 15213, United States
3. Pittsburgh VA Medical Center , Pittsburgh, PA 15240, United States
4. Department of Physiology, University of Toronto , Toronto, ON M5S 1A8, Canada
5. Toronto General Research Institute (Advanced Diagnostics) , Toronto, ON M5G 2C4, Canada
6. Division of Research, Kaiser Permanente Northern California , Oakland, CA 94612, United States
7. Kaiser Permanente Bernard J. Tyson School of Medicine , Pasadena, CA 91101, United States
8. Department of Obstetrics and Gynaecology, University of Toronto , ON M5G 1E2, Canada