Background Potentially lethal ventricular arrhythmias (PLVAs) occur frequently in survivors after acute myocardial infarction and are increasingly recognized in other forms of structural heart diseases.This study investigated the prevalence and prognostic significance of PLVAs in patients with chronic heart failure (CHF).Methods Data concing demographics,etiology of heart failure,NYHA functional class,biochemical variables,electrocardiographic and echocardiographic findings,and medical treatments were collected by reviewing hospital medical records from 1080 patients with NYHA Ⅱ-Ⅳ and a left ventricular (LV) ejection fraction ≤45％.PLVAs were defined as multi-focal ventricular ectopy (＞30 beats/h on Holter monitoring),bursts of ventricular premature beats,and nonsustained ventricular tachycardia.All-cause mortality,sudden death,and rehospitalization due to worsening heart failure,or cardiac transplantation during 5-year follow-up after discharge were recorded.Results The occurrence rate of PLVAs in CHF was 30.2％,and increased with age; 23.4％ in patients ＜45 years old,27.8％ in those between 45-65 years old,and 33.5％ in patients ＞65 years old (P=0.033).Patients with PLVAs had larger LV size and lower ejection fraction (both P ＜0.01) and higher all-cause mortality (P=0.014) during 5-year follow-up than those without PLVAs.Age (OR 1.041,95％ Cl 1.004-1.079,P=0.03) and LV end-diastolic dimension (OR 1.068,95％ Cl 1.013-1.126,P=0.015) independently predicted the occurrence of PLVAs.And PLVA was an independent factor for all-cause mortality (RR 1.702,95％ Cl 1.017-2.848,P=0.031) and sudden death (RR 1.937,95％ CI 1.068-3.516,P=0.030) in patients with CHF.Conclusion PLVAs are common and exert a negative impact on Iona-term clinical outcome in patients with CHF.