Contemporary management of patients with heart failure (HF) includes treatment with cardiac resynchronisation therapy (CRT). The benefit of CRT results from several mechanisms, predominantly correction of dyssynchrony. The development of a novel method of measuring left ventricular global dyssynchrony using cardiovascular magnetic resonance (CMR), termed CMR-tissue synchronisation index (CMR-TSI) is described. A study of 225 patients with HF who underwent CMR-TSI found that HF appears synonymous with dyssynchrony. The importance of myocardial scar is illustrated in a study of 95 patients which revealed a significantly higher mortality in patients undergoing CRT who had postero-lateral (PL) scar on CMR. A study into the effects of a combination of CMR-TSI and scar imaging found that presence of either CMR-TSI >110ms or PL scar resulted in a worse outcome, whilst the presence of both was associated with the highest mortality. A final study in 148 patients allowed the development of a risk score to predict mortality from CRT on the basis of 16 candidate variables. PL scar, dyssynchrony and creatine discriminated between survivors and non-survivors and were used to derive the score. The score is discussed in the context of data derived from echocardiography and clinical studies.