RANDOMISATION AND FOLLOW UP. Following pacemaker implant, pressure studies, and Ultrasound assessment, participants will be randomized in a double blind fashion to have their pacemaker programmed to either one of the following (1) Pacemaker Off mode, ( 2 ) Left and Right Heart chamber pacemaker mode. The Participants will be paced in that specific mode for four months before repeat Clinical and Cardiac Ultrasound assessments. The mode of pacing will then be changed, and maintained for a further four months, before repeat Clinical and Ultrasound assessment. The pacing mode will be randomly selected, but no pacing mode will be repeated in any one participant. The participant and the member of the research team performing the Clinical and Ultrasound assessment of the participant, shall be blinded to the pacemaker mode.