1 University Medical Center Groningen, University of Groningen, Department of Cardiology, PO Box 30.001, 9700, RB, Groningen, The Netherlands.
2 University Medical Center Groningen, University of Groningen, Department of Cardiology, PO Box 30.001, 9700, RB, Groningen, The Netherlands. r.a.de.boer@umcg.nl.
3 Massachusetts General Hospital, Cardiovascular Research Center, Boston, MA, USA.