Standard Care Versus Triventricular Pacing in Heart Failure

100 patients with QRS duration (120-150ms LBBB) for device insertion as per ESC guidelines 2013 will be recruited to the study from 10 centres. Patients will undergo the pre-operative work up that is typical of their institution (for example at the GSTT site this will include cardiac MRI, cardiopulmonary exercise testing (CPET), 6 minute walk test , bloods including Nt pro BNP, Minnesota living with heart failure questionnaire (MLWHFQ), 2D/3D echocardiogram and the collection of demographic data.) Patients will then be randomised in a 1:1 fashion to receive either the Triventricular device or the conventional biventricular device. Participants will then be followed up as per the implanting institution's typical follow up. (for example at GSTT this will include 6 week atrio-ventricular and ventricular-ventricular optimisation (if patients have a device that does not autooptimise) and review by a clinician as well as a 6 month follow up at which point the CPET, 6 minute walk test , MLWHFQ, bloods including Nt pro BNP, 2D/3D echocardiogram and the collection of demographic data will be repeated.) Regardless of the institution's own follow up, a 6 week (4-8 week) and 6 month (5-9month) follow up appointment will form part of the study protocol. The 6 week check will be take the form of a standard clinical pacing check with physician input if it is deemed necessary as per the host institution's usual standard of care/ (usually one would imagine if a problem of therapy delivery is noted) The 6 month follow up will allow for patient and device follow up. This will require 2D echocardiography, 6 min walk test, MLWHFQ and NtproBNP measurement. Where possible institutions will be encouraged to perform CPET and 3D echocardiography pre implant and at 6 months. For determining the " response rate", a positive response will be defined as an absolute reduction of LVESV by 15%. In order to determine the magnitude of response then the change in LVESV will be assessed as a continuous variable.