SCD-HeFT: Use of R-R interval statistics for long-term risk stratification for arrhythmic sudden cardiac death

Heart Rhythm. 2015 Oct;12(10):2058-66. doi: 10.1016/j.hrthm.2015.06.030. Epub 2015 Jun 19.


Background: In the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), a significant fraction of the patients with congestive heart failure ultimately did not die suddenly of arrhythmic causes. Patients with CHF will benefit from better tools to identify if implantable cardioverter-defibrillator (ICD) therapy is needed.

Objectives: We aimed to identify predictor variables from baseline SCD-HeFT patients' R-R intervals that correlate to arrhythmic sudden cardiac death (SCD) and mortality and to design an ICD therapy screening test.

Methods: Ten predictor variables were extracted from prerandomization Holter data from 475 patients enrolled in the ICD arm of the SCD-HeFT by using novel and traditional heart rate variability methods. All variables were correlated to SCD using the Mann-Whitney-Wilcoxon test and receiver operating characteristic analysis. ICD therapy screening tests were designed by minimizing the cost of false classifications. Survival analysis, including log-rank test and Cox models, was also performed.

Results: A short-term fractal exponent, α1, and a long-term fractal exponent, α2, from detrended fluctuation analysis, the ratio of low- to high-frequency power, the number of premature ventricular contractions per hour, and the heart rate turbulence slope are all statistically significant for predicting the occurrences of SCD (P < .001) and survival (log-rank, P < .01). The most powerful multivariate predictor tool using the Cox proportional hazards regression model was α2 with a hazard ratio of 0.0465 (95% confidence interval 0.00528-0.409; P < .01).

Conclusion: Predictor variables extracted from R-R intervals correlate to the occurrences of SCD and distinguish survival functions among patients with ICDs in SCD-HeFT. We believe that SCD prediction models should incorporate Holter-based R-R interval analysis to refine ICD patient selection, especially to exclude patients who are unlikely to benefit from ICD therapy.

Keywords: Detrended fluctuation analysis; Heart failure; Heart rate turbulence; Heart rate variability; Implantable cardioverter-defibrillators; Nonlinear dynamics; Sudden cardiac death.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Amiodarone / therapeutic use*
  • Anti-Arrhythmia Agents / therapeutic use
  • Arrhythmias, Cardiac / complications*
  • Arrhythmias, Cardiac / physiopathology
  • Arrhythmias, Cardiac / therapy
  • Death, Sudden, Cardiac / epidemiology*
  • Death, Sudden, Cardiac / etiology
  • Death, Sudden, Cardiac / prevention & control
  • Defibrillators, Implantable
  • Electrocardiography, Ambulatory*
  • Female
  • Follow-Up Studies
  • Heart Failure / complications*
  • Heart Failure / mortality
  • Heart Failure / physiopathology
  • Heart Rate / physiology*
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Risk Assessment / methods*
  • Risk Factors
  • Survival Rate / trends
  • Time Factors
  • United States / epidemiology
  • Young Adult


  • Anti-Arrhythmia Agents
  • Amiodarone