title: Repolarization Lability Measured by Spatial TT' Angle.
abstract: OBJECTIVE
  Increased T peaks cloud volume is associated with increased risk of ventricular arrhythmias (VA) in cardiomyopathy (CM) patients. T peaks cloud volume is formed, as a result, of (1) the angle between consecutive T-vectors and (2) temporal variability in T-vector amplitude. This study compares association of these two factors with VA.
  
  
  METHODS
  Baseline orthogonal ECGs were recorded during 5 min at rest in 414 patients with structural heart disease [mean age 59.4±12.0; 68% whites; 73% men; 45% non-ischemic CM] before implantation of implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death. The spatial TT' angle between consecutive spatial T vectors was calculated using the definition of the inner product.
  
  
  RESULTS
  During a median 14 months of follow-up, 61 patients experienced sustained VA with appropriate ICD therapies. In a multivariable Cox regression model after adjustment for age, sex, race, spatial TT' angle was associated with VA (HR 1.03; 95%CI 1.0-1.05; P=0.034). Interaction with CM type was found: TT' angle was strongly associated with polymorphic VT/VF in non-ischemic CM (HR 1.04; 95%CI 1.0-1.05; P=0.033).
  
  
  CONCLUSIONS
  Increased spatial TT' angle is associated with increased risk of VA.
authors.affiliation: Oregon Health and Science University, Knight Cardiovascular Institute, Portland, Oregon, USA.|Johns Hopkins University School of Medicine, Cardiovascular Division, Baltimore, Maryland, USA.
authors.forename: Larisa G
authors.initials: LG
authors.lastname: Tereshchenko