Objectives To investigate the prognostic value of circulating levels of asymmetric dimethylarginine (ADMA) in patients with acute decompensation of (New York Heart Association (NYHA) class III/IV) chronic heart failure and reduced left ventricular ejection fraction.

Design Single-centre prospective observational study.

Setting Tertiary referral centre.

Patients A total of 651 consecutive and eligible hospitalised patients were studied. Patients were divided into four groups according to the quartiles of circulating levels of ADMA upon presentation.

Main outcome measures Incidence of in-hospital (or 7-day in the case of prolonged hospitalisation), 31-day and 1-year cardiac mortality were the pre-specified study end points.

Results Cumulative rates of in-hospital, 31-day and 1-year cardiac mortality were 10.6%, 18.7% and 36.4%, respectively. There was a gradual increased risk of in-hospital (p_{for trend}=0.011), 31-day (p_{for trend}=0.044) and 1-year (p_{for trend}<0.001) mortality with increasing ADMA quartiles. After adjustment for possible confounders, patients at the highest ADMA quartile were at significantly higher risk for in-hospital (p=0.042), 31-day (p=0.032) and 1-year (p<0.001) mortality than those in the lowest quartile.

Conclusions According to the present results, an elevated circulating level of ADMA is a strong independent predictor of short-term and long-term mortality in patients with acute decompensation of NYHA class III/IV chronic heart failure and reduced left ventricular ejection fraction. ADMA levels upon presentation may confer enhanced risk stratification in this setting.