The Safety and Efficacy of Optimising Pacemaker Heart Rate for Contractility: Effects on Walk Time, Cardiac Remodelling and Quality of Life.

Design: This will be a randomised, double-blind 'placebo' controlled trial of optimised programming versus standard rate-response settings, aiming to determine whether the short term improvements translate into longer term benefits.

Study participants: 60 adult patients (>18years) aiming for 50 matched datasets (25 in each arm).

Study Procedures: Patients attending the heart failure clinic, the pacemaker clinic or previous participants in the acute cross-over study (pilot data 2) will be approached with a standard letter and information sheet and then a telephone call to make sure any remaining questions are answered.

Patients agreeing to participate will attend the clinical research facility (CRF) and will be asked to sign a consent form. Each patient will have a standard device check, check of their demographic data, and co-morbidities. The investigators will record a resting cardiac ultrasound, and, in those who did not participate in the pilot study (or did so more than six months previously), we will measure the force frequency relationship (FFR) as described to determine critical heart rate (HR), and the optimal range of HR rise. All images will be stored for offline analysis. Participants will then be asked to do a symptom-limited walk test on the treadmill (until they cannot do any more). At this first visit, participants will also complete a quality of life questionnaire. All of these activities will take place in the Clinical Research Facility at Leeds General Infirmary.

Randomisation: Each patient will then be randomised to either optimised programming (n=30) as predicted by their force-frequency curve or standard settings (n=30). In the optimised group, programming will keep heart rates below the critical HR. Randomisation will be by a random number generator and programming will be undertaken by one of my colleagues to maintain blinding.