Myocardial fiber deformation measurements have been reported to be associated with adverse outcomes in patients with acute heart failure and those with myocardial infarction.However,few studies have addressed the prognostic value of global circumferential strain(GCS)in dilated cardiomyopathy(DCM)patients with severely impaired systolic function.This study aimed to evaluate the prognostic value of cardiac magnetic resonance(CMR)-derived GCS in DCM patients with severely reduced ejection.Consecutive DCM patients with severely reduced ejection fraction(EF ＜35％)who underwent CMR were included.GCS was calculated from CMR cine images.The clinical endpoint was a composite of all-cause mortality,heart transplantation,implantable cardioverter defibrillator(ICD)implantation and aborted sudden cardiac death(SCD).A total of 129 patients with a mean EF of 15.33％(11.36％-22.27％)were included.During a median follow-up of 518 days,endpoint events occurred in 50 patients.Patients with GCS ≥ the median(-5.17％)had significantly reduced event-free survival as compared with those with GCS＜ the median(P＜0.01).GCS was independently associated with adverse events after adjusting for clinical and imaging risk factors including extent of late gadolinium enhancement(LGE)(P＜0.05).Adding GCS into the model including the extent of LGE resulted in significant improvements in the C-statistic(from 0.706 to 0.742;P＜0.05)with a continuous net reclassification improvement(NRI)of 29.71％.It was concluded that GCS derived from CMR could be useful for risk stratification in DCM patients with severely reduced EF,which may increase common imaging risk factors including LGE.