Heart Rate < 50 and >100bpm PR Interval <120 and > 220ms QRS duration < 70 and >120ms QTC Interval (Bazett) > 450ms Or, has clinically significant rhythm abnormalities identified during 24-hour screening Holter assessment. Subjects with left bundle branch block are excluded from the study. Subjects with partial right bundle branch block may be considered for inclusion following consultation with the GlaxoSmithKline (GSK) Medical Monitor. Subjects with Wolf-Parkinson-White (WPW) syndrome are excluded from the study.