Aims
This study aimed to compare the association between measures of left atrial (LA) structure and function, derived from cardiovascular magnetic resonance (CMR), with cardiovascular death or non-fatal heart failure events in patients with non-ischaemic dilated cardiomyopathy (DCM).

Methods and results
CMR studies of 580 prospectively recruited patients with DCM in sinus rhythm [median age 54 (interquartile range 44–64) years, 61% men, median left ventricular ejection fraction 42% (30–51%)] were analysed for measures of LA structure [LA maximum volume index (LAVImax) and LA minimum volume index (LAVImin)] and function (LA emptying fraction, LA reservoir strain, LA conduit strain (LACS), and LA booster strain]. Over a median follow-up of 7.4 years, 103 patients (18%) met the primary endpoint. Apart from LACS, each measure of LA structure and function was associated with the primary endpoint after adjusting for other important prognostic variables. The addition of each LA metric to a baseline model containing the same important prognostic covariates improved model discrimination, with LAVImin providing the greatest improvement [C-statistic improvement: 0.702–0.738; χ2 test comparing likelihood ratio P < 0.0001; categorical net reclassification index: 0.210 (95% CI 0.023–0.392)]. Patients in the highest tercile of LAVImin had similar event rates to those with persistent atrial fibrillation. Measures of LA strain did not enhance model discrimination above LA volumetric measures.

Conclusion
Measures of LA structure and function offer important prognostic information in patients with DCM and enhance the prediction of adverse outcomes. LA strain was not incremental to volumetric analysis for risk prediction.