RT Journal Article SR Electronic T1 Upgrading from right ventricular pacing to biventricular pacing in pacemaker patients with chronic heart failure JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 102 OP 107 DO 10.1136/hrt.2005.065094 VO 94 IS 1 A1 Leclercq, Christophe YR 2008 UL http://heart.bmj.com/content/94/1/102.abstract AB