Heart Failure Clinical Trials

The goal of this clinical trial is to find out which type of specialist pacemaker-known as cardiac resynchronisation therapy (CRT)-works best for people with heart failure and a delay in how the lower chambers of the heart beat together (called electrical dyssynchrony). The main aims of the study are: To compare the effects of conventional biventricular pacing (BVP), conduction system pacing (CSP) and left-bundle optimised CRT (LOT-CRT) on heart failure symptoms and heart rhythm problems over six months. To explore how these pacing methods affect heart muscle strength, electrical activity, and overall heart function. Participants will: Attend four hospital visits over a six-month period. At Visit 1, meet a member of the research team to discuss the study and have screening tests to check eligibility. Participants will also have a smartphone app installed and receive training on how to record their daily heart failure symptoms. At Visit 2, have a CRT pacemaker implanted. The type of pacemaker will be chosen at random, with a 1 in 3 chance of receiving: * Biventricular pacing (BVP); the current standard treatment * Conduction system pacing (CSP) * LOT-CRT (Left-bundle optimised CRT); a combination of both At Visit 3 (around 12 weeks after implantation) and Visit 4 (6 months after implantation), take part in routine follow-up assessments to check the pacemaker and heart function. At Visits 2 and 4, also undergo non-invasive electrical mapping tests, including wearing a specialised vest and having a low-dose CT scan of the chest. These tests help researchers understand how the heart's electrical system responds to different pacing methods.