1. Cardiac Arrhythmia Center, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
2. Baystate Medical Center, Springfield, MA 01199, USA
3. Department of Cardiology, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 9190400, Israel
4. Cardiac Arrhythmia Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA