AIMS In patients with heart failure (HF), the association between sudden death and arrhythmic pattern at 24-h Holter monitoring [number of ventricular premature contractions per hour (VPCs/h) and presence of non-sustained ventricular tachycardia (NSVT)] has previously been investigated with conflicting results. Since both VPCs/h and NSVT disregard the time course of arrhythmic events, we developed a new index based on the short-term peak rate of ectopies and investigated its prognostic power in HF patients. METHODS AND RESULTS We studied 200 HF patients in sinus rhythm [age: [median (interquartile range)] 54 years [47-58], left ventricular ejection fraction (LVEF): 23% [19-28], New York Heart Association (NYHA) class II-III: 88%]. For each patient, the Holter recording was automatically scanned shifting a 30 beat window one beat at a time, and the maximum number of ectopic beats found in a window was named peak ectopy rate (PEAK_ER). The association between PEAK_ER and sudden death was assessed by Cox proportional hazards regression analysis. Survival analysis was also carried out adjusting for NYHA class, aetiology, LVEF, left ventricular end diastolic diameter, blood urea nitrogen, amiodarone, Digoxin, beta-blockers, NSVT, VPCs/h, and the standard deviation of all normal-to-normal beats. During a 5-year follow-up [31 (12-60) months], 23 patients died of sudden death. Out of the arrhythmic markers, PEAK_ER but not VPCs/h and NSVT was significantly associated with sudden death in univariable analysis (RR: 1.08, 95% CI: 1.02-1.14, P = 0.005) and after adjustment for covariates (RR: 1.09, 95% CI: 1.03-1.15, P = 0.004). CONCLUSIONS The investigation of the time course of arrhythmic events provides independent information in the identification of patients at increased risk of sudden death and may therefore be considered in the development of treatment strategies in HF patients.