Approximately 40% of resynchronization therapy recipients do not appear to clearly benefit. These patients are termed 'non-responders'. This study will assess whether a heart ultrasound (echo) technique called 'torsion imaging' can be used to increase the likelihood of benefit from resynchronization therapy.

Background: Despite advances in pharmacotherapy, patients with heart failure (HF) are at high risk for death and hospitalization. Over 25% of patients with systolic HF have dyssynchronous ventricular contraction that impairs left ventricular (LV) function and results in HF progression. Cardiac resynchronization therapy (CRT) is designed to synchronize ventricular mechanical activity, improving cardiac output and reducing HF symptoms. As shown in our pilot data, at least 40% of patients do not respond to CRT despite pre-screening for the presence of longitudinal (long axis) mechanical (velocity) dyssynchrony and targeting LV lead placement to the latest site of latest velocity. Methods to improve the rates of response to CRT are required. Torsion imaging guided optimization of CRT timing is a promising approach and will be tested in this study.

Primary hypothesis: Optimization of inter-ventricular (VV) timing, guided by torsion imaging, will increase functional capacity and reduce LV end systolic volume [ESV] in CRT in patients who have not responded after ≥ 6 months. CRT response will be defined by a ≥ 1 functional class improvement and either a ≥ 10% reduction in LV ESV or a ≥ 5% increase in EF at follow-up versus baseline.

Secondary aims: To compare the following in torsion-guided vs usual care patients: a) echo parameters (intra-LV and VV dyssynchrony and torsion, and mitral regurgitation), b) N-terminal BNP levels, and c) generic / disease-specific quality of life.

Methods: Randomized study of patients who have not responded to CRT after ≥ 6 months.

Inclusion Criteria:

• non-response to CRT as indicated,
• stable doses of ACE I / ARB and beta-blocker for ≥ 2 months, &
• controlled heart rate if in atrial fibrillation.

Exclusion Criteria:

• inadequate images to assess torsion
• no significant augmentation in torsion with optimization
• unable or unwilling to provide informed consent,
• medical condition other than HF likely to cause death within 6 months,
• cardiac transplant planned,
• myocardial infarction or revascularization since CRT implant.