Currently the main selection tool for Cardiac Resynchronisation Therapy (CRT) is the QRS duration on the surface echocardiography (ECG) which has been shown to be a poor predictor of response. We sought to evaluate the use of tissue Doppler (TDI) assessment of dyssynchrony in prediction of response to CRT.

The hypothesis is that the presence of mechanical dyssynchrony (measured using TDI echocardiography) successfully identifies heart failure patients who will respond to CRT. Conversely, the absence of mechanical dyssynchrony is associated with a low/no response to CRT.

This is a three arm study. Group 1 comprises patients with dyssynchrony on TDI who are implanted with a biventricular ICD whereas Group 2 patients comprise patients who have no dyssynchrony. Group 2 patients are randomised 1:1 to either receive a biventricular ICD (2a) or an ICD (2b). All patients undergo a NYHA class assessment, a cardiopulmonary exercise test, and an echocardiogram at baseline and at 6 months follow up. Baseline and 6 months findings will be compared in all three groups.

Inclusion Criteria:

1. Patients must have an indication for ICD therapy
2. Heart failure of any aetiology with evidence of left ventricular (LV) systolic dysfunction with LV ejection fraction < 35% and LV cavity dilatation (end diastolic dimension > 55 mm)
3. NYHA Class III/IV symptoms of heart failure despite optimal medical therapy
4. QRS duration ≥120ms

Exclusion Criteria:

1. Reversible cause of heart failure such as ongoing ischaemia amenable to revascularisation or treatable valvular disease
2. Requirement for ventricular pacing due to atrioventricular block.
3. Limited life expectancy (< 6 months)