Background:Current risk stratification of idiopathic dilated cardiomyopathy (IDC) lacks sufficient sensitivity and specificity.The objective of this study was to investigate the predictive role of frontal QRS-T angles in IDC.Methods:A prospective study with 509 IDC patients was performed from February 2008 to December 2013 in the Affiliated Drum Tower Hospital,Nanjing University School of Medicine.Baseline values and changes in QRS-T angles were recorded.Follow-up was conducted every 6 months.Analyses by Cox Proportional Hazards model were performed to evaluate the association between QRS-T angle and outcomes.The primary outcome of interest was all-cause mortality.Results:During a median follow-up of 34 months,90 of 316 patients with QRS-T angles ＞90° died compared to 31 of 193 patients with QRS-T angles ≤90° (hazard ratio [HR] =2.4,P ＜ 0.001).Cardiac death was more prevalent in patients with a wide QRS-T angle (HR =2.4,P ＜ 0.001),similar to heart failure rehospitalization (HR =2.5,P ＜ 0.001).After adjustment for potential prognostic factors,the QRS-T angle was independently associated with all-cause mortality (HR =2.5,P ＜ 0.05),cardiac mortality (HR =1.9,P ＜ 0.05),and heart failure rehospitalization (HR =2.3,P ＜ 0.01).Optimized therapy significantly narrowed the frontal QRS-T angle (100.9 ±4 53.4° vs.107.2 + 54.4°,P ＜ 0.001).The frontal QRS-T angle correlated well with established risk factors,such as left ventricular ejection fraction,brain natriuretic peptide,and New York Heart Association functional class.Conclusions:The frontal QRS-T angle is a powerful predictor of all-cause mortality,cardiac mortality,and worsening heart failure in IDC patients,independent of well-established prognostic factors.Optimized therapy significantly narrows the QRS-T angle,which might be an indicator of medication compliance,but this requires further investigation.