title: Multilead template-derived residua of surface ECGS for quantitative assessment of arrhythmia risk.
abstract: BACKGROUND
  Contemporary electrocardiographic (ECG) markers including ventricular ectopy and arrhythmias have not proved reliable in risk assessment for life-threatening arrhythmias.
  
  
  METHODS
  We developed the "Multilead ECG Template-Derived Residua" approach to remove intrinsic morphologic differences and allow calculation of pathologic ECG heterogeneities among spatially separated leads. Prediction by R-wave and T-wave heterogeneity (RWH, TWH) analysis was tested in simulated and clinical ECGs.
  
  
  RESULTS
  An enabling description of the Residua algorithm is provided. Simulated ECGs with but not without Residua produced a linear relationship (correlation coefficient r(2) = 0.999) between input and output RWH and TWH values. In heart failure patients, Residua disclosed a marked crescendo in RWH from 164.1 ± 33.1 at baseline to 299.8 ± 54.5 μV and TWH from 134.5 ± 20.6 at baseline to 239.2 ± 37.0 μV at 30-45 minutes before the arrhythmia (both, P < 0.05), which remained elevated until arrhythmia onset. Without Residua, mean RWH and TWH were elevated at 1061.0 ± 222.9 and 882.5 ± 375.2 μV, respectively, throughout the recording and were not different prior to ventricular tachycardia onset.
  
  
  CONCLUSIONS
  Calculation of ECG-template derived Residua provides a highly accurate means for assessing arrhythmia risk from standard ECGs. Potential widespread applications include resting diagnostic 12-lead, ambulatory, and exercise ECGs, electrophysiologic study laboratory recordings, and implantable devices.
authors.affiliation: Division of Cardiovascular Medicine,  Department of Medicine,  Beth Israel Deaconess Medical Center,  Harvard-Thorndike Electrophysiology Institute, Harvard Medical School, Boston, MA.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Nearing
authors.affiliation: Division of Cardiovascular Medicine,  Department of Medicine,  Beth Israel Deaconess Medical Center,  Harvard-Thorndike Electrophysiology Institute, Harvard Medical School, Boston, MA.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
mesh_terms: D001145:Arrhythmias, Cardiac / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology; D006801:Humans; D015203:Reproducibility of Results; D018570:Risk Assessment
keywords: depolarization; heterogeneity; repolarization; risk stratification; ventricular fibrillation; ventricular tachycardia