Heart failure patients may benefit from having a special pacemaker implanted that can make the heart pump in a more coordinated and efficient way Cardiac Resynchronisation Therapy (CRT). For the heart to pump well it is necessary for the pacing wires to be placed in optimal positions. Only two thirds of people respond to CRT and this may be because of non-ideal pacing wire position. A potential marker for response is the change in heart pump pressure change over time. The aim of this study is to use a specialised wire in the main pumping chamber of the heart to record the pressure changes with the pacing lead in various positions to determine the optimal position. It is postulated that the improved pressure changes will increase the proportion of responders.

Pilot study work has shown that the work is technically feasible and safe. The initial data has been published in a highly regarded scientific journal. This main study will be a multicentre randomised controlled trial whereby patients will be randomised to either standard treatment or pressure wireguided treatment. The patients in the pressurewire guided arm will have a specialised wire implanted into the main pumping chamber of their heart via a blood vessel at the top of the leg (or less commonly a blood vessel in the wrist). This will measure acute pressure changes over time and the pacing lead will be positioned in the site that gives the greatest change in pressure.

If the patients in the pressurewire guided arm fare better than those receiving standard treatment it may alter how a large proportion of heart failure patients are treated around the world. The study requires 282 patients and is likely to take two years to complete.

Inclusion Criteria:

• Patients fulfilling standard criteria for CRT
• Ischaemic or non-ischaemic heart failure

Exclusion Criteria:

• Contraindication to pressure wire assessment including:
• Severe aortic valve disease
• Mechanical aortic valve replacement
• Severe peripheral vascular disease
• LV thrombus