Patients are randomised to receive ongoing optimised device and medical therapy or triple ventricular site resynchronisation. The hypothesis states that patients receiving triple-site resynchronization will exhibit a better response.

Inclusion Criteria:

• Implanted with a CRT device > 6 months previously according to current and conventional CRT indications
• Device optimization > 1 months previously
• Aged 18yrs or older
• Able to attend outpatient follow up

Exclusion Criteria:

• Recent MI (<2 months)
• Women who are pregnant or planning pregnancy
• Severe co morbid illness (where patients are not expected to survive duration of follow up period or where repeated outpatient visits may not be in best interest of patients)
• Upgrade procedure is contraindicated for safety reasons.
• Class IV inotropic agents
• Patient unwilling to comply with required follow-up protocol including randomization scheme