Pacing in Heart Failure With Preserved LVEF

A random-order cross-over pilot trial of a CE marked device (pacemaker) outside its current intended purposes. The study will comprise 10 patients. Recruitment of patients will take place from The University Hospital of Wales (Cardiff \& Vale University Health Board \[CVUHB\]). All patients recruited will have septal flattening during exercise demonstrated using contrast stress (exercise) echocardiography. All 10 patients will be implanted with a CRT-pacemaker device and will be tested on all three of the following settings on separate visits (with a gap of up to 5 days between visits) in random order: Routine Medical Therapy Routine Medical Therapy + LVP Routine Medical Therapy + BiVP