1. Department of Cardiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands;
2. Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands;
3. Department of Medicine, Division of Cardiovascular Diseases, University of Alabama at Birmingham, Birmingham, Alabama; and
4. Interuniversity Cardiology Institute of the Netherlands, Utrecht, The Netherlands