How is COGNItive Function Affected by Cardiac Resynchronisation Therapy?

The primary objective of COGNI-CRT is to assess whether Cardiac Resynchronisation Therapy (CRT) can improve cognitive function in patients with systolic HF (LVEF ≤35%), when compared to a control group of patients implanted with an Implantable Cardioverter-Defibrillator (ICD) or a permanent pacemaker (PPM) with systolic HF (LVEF ≤35%). This clinical investigation is a prospective, single-centre cohort study. Each participant will be followed for 6 months. The study will collect data over 3 years; 2.5 years for enrolment and 6 months until the last participant completes the last 6-month follow-up visit. N.B: COGNI-CRT does NOT affect the patient's care pathway - the patients who will be selected for participation are those who have already been referred for the device implant. The ONLY difference to the patient's care pathway caused by COGNI-CRT is the addition of a battery of cognitive function tests, which involves asking the patient questions and asking them to complete questionnaire-like cognitive tests. NTpro-BNP levels, NYHA classification and LVEF will be measured prior to device implantation and at 6-months post-implant to assess the device's impact on the participant's heart failure (and CRT response). N.B: NT-proBNP, NYHA classification and LVEF are all parts of the patient's standard care pathway, COGNI-CRT is just utilising the data collected as part of the investigation. The main study arm and control group allows COGNI-CRT to assess 3 potential outcomes for patients with severe HF (LVEF \<35%): 1. Cognitive function is not improved by CRT, ICDs or PPMs 2. Cognitive function can be improved by the assurance of rate control offered by CRT, ICDs and PPMs 3. Cognitive function can be improved by the assurance of ventricular synchronisation and rate control provided by the additional left ventricular lead in CRT devices.