title: Spatial QRS-T angle predicts cardiac death in a clinical population.
abstract: OBJECTIVE
  The purpose of this study was to validate the prognostic value of computer-derived measurements of the spatial alignment of ventricular depolarization and repolarization from the standard 12-lead ECG in a general medical population.
  
  
  METHODS
  Analyses were performed on the first ECG digitally recorded from 46,573 consecutive patients since 1987. QRS and T vector were synthesized by deriving XYZ leads from the 12 leads using the inverse Dower weighting matrix. Subset analyses were considered in patients with and those without standard ECG diagnoses (i.e., atrial fibrillation, Q waves, left ventricular hypertrophy, prolonged QRS duration). The main outcome measure was cardiovascular mortality.
  
  
  RESULTS
  During a mean follow-up of 6 years, 4,127 cardiovascular deaths occurred. After adjusting for age, heart rate, and gender in a Cox regression analysis, spatial QRS-T angle was the most significant predictor of cardiovascular mortality, outperforming all other ECG measurements and diagnostic statements. In the subset with ECGs free of any standard diagnoses, annual cardiovascular mortality was 0.8% for normal (0-50 degrees ), 2.3% for borderline (50-100 degrees ), and 5.1% for abnormal (100-180 degrees ) QRS-T angle groups. The borderline and abnormal angle groups had 1.5- and 1.9-fold higher risk, respectively, relative to the normal QRS-T angle group after adjustment for age, gender, and heart rate. Similar results were found when patients with standard ECG diagnosis were included or compared.
  
  
  CONCLUSIONS
  Spatial QRS-T angle is a significant and independent predictor of cardiovascular mortality that provides greater prognostic discrimination than any of the commonly utilized ECG diagnostic classifications.
authors.affiliation: Division of Cardiovascular Medicine, Stanford University Medical Center and Veterans Affairs Health Care System, Palo Alto, California 94304, USA. takuya22@rnac.ne.jp
authors.forename: Takuya
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Victor F
authors.initials: VF
authors.lastname: Froelicher
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.forename: Sung
authors.initials: S
authors.lastname: Chun
authors.forename: Paul
authors.initials: P
authors.lastname: Wang
mesh_terms: D002318:Cardiovascular Diseases / Q000401:mortality*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D016019:Survival Analysis; D013997:Time Factors