This study investigates the predictive value of short-term heart rate variability (HRV) in chronic heart failure (CHF) patients for sudden cardiac death. A multivariate survival model was developed using data from 202 patients with moderate to severe CHF, and validated in a separate group of 242 patients. The model identified low-frequency power (LFP) of HRV during controlled breathing ≤ 13 ms² and left ventricular end-diastolic diameter ≥ 77 mm as independent predictors of sudden death. In the validation sample, LFP ≤ 11 ms² and ≥ 83 ventricular premature contractions per hour on Holter monitoring were also significant predictors. These findings suggest that reduced short-term LFP during controlled breathing is a powerful predictor of sudden death in CHF patients, independent of other clinical and functional variables. This information can help identify patients who may benefit from prophylactic implantation of a cardiac defibrillator.This study investigates the predictive value of short-term heart rate variability (HRV) in chronic heart failure (CHF) patients for sudden cardiac death. A multivariate survival model was developed using data from 202 patients with moderate to severe CHF, and validated in a separate group of 242 patients. The model identified low-frequency power (LFP) of HRV during controlled breathing ≤ 13 ms² and left ventricular end-diastolic diameter ≥ 77 mm as independent predictors of sudden death. In the validation sample, LFP ≤ 11 ms² and ≥ 83 ventricular premature contractions per hour on Holter monitoring were also significant predictors. These findings suggest that reduced short-term LFP during controlled breathing is a powerful predictor of sudden death in CHF patients, independent of other clinical and functional variables. This information can help identify patients who may benefit from prophylactic implantation of a cardiac defibrillator.