Shaan Khurshid1,2, Alan Hanley3. 1. Cardiovascular Research Center, Massachusetts General Hospital, 55 Fruit Street, Yawkey 5B, Boston, MA, 02114, USA. skhurshid@partners.org. 2. Demoulas Center for Cardiac Arrhythmias, Massachusetts General Hospital, Boston, MA, USA. skhurshid@partners.org. 3. Demoulas Center for Cardiac Arrhythmias, Massachusetts General Hospital, Boston, MA, USA.