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.