title: Changes of the T-wave amplitude and angle: an early marker of altered ventricular repolarization in hypertension.
abstract: BACKGROUND
  The heterogeneity of ventricular repolarization is an important proarrhythmic factor. QT dispersion has been proposed to reflect the inhomogeneity of ventricular repolarization, but a poor reproducibility limits its clinical applicability. Reliable noninvasive methods to quantify abnormalities in ventricular repolarization are still lacking. The T-loop morphology analysis is a novel method aimed at quantifying ventricular repolarization.
  
  
  OBJECTIVE
  To test the ability of the T-loop morphology analysis to discriminate between hypertensive patients and healthy subjects, 105 hypertensive patients (mean age 63.6 +/- 12.3 years) and 110 healthy controls (mean age 49.7 +/- 14.3 years) were evaluated.
  
  
  METHODS
  The maximum QT interval (QT maximum), the minimum QT interval (QT minimum), and their difference (QT dispersion) were calculated from a digitally recorded 12-lead electrocardiogram (ECG) in both study groups. X, Y, and Z leads were reconstructed from the 12-lead ECG, and the amplitude of the maximum T vector (T amplitude) and the angle between the maximum T vector and X axis (T angle) were calculated from the projection of the T loop in the frontal plane.
  
  
  RESULTS
  T amplitude (p < 0.001), T angle (p = 0.05), and QT dispersion (p = 0.04) were significantly different between hypertensive patients and controls, while QT maximum (p = 0.14) and QT minimum (p = 0.35) did not differ between the groups. T amplitude was the only marker which differed between hypertensive patients without ECG criteria for left ventricular hypertrophy and controls (p = 0.002).
  
  
  CONCLUSIONS
  T-loop features and particularly T amplitude are significantly different between hypertensive patients and healthy controls and may serve as early markers of repolarization abnormalities in a hypertensive population.
authors.affiliation: Department of Cardiological Sciences, St. George's Hospital Medical School, London, England.
authors.forename: P
authors.initials: P
authors.lastname: Dilaveris
authors.forename: E
authors.initials: E
authors.lastname: Gialafos
authors.forename: J
authors.initials: J
authors.lastname: Poloniecki
authors.forename: K
authors.initials: K
authors.lastname: Hnatkova
authors.forename: D
authors.initials: D
authors.lastname: Richter
authors.forename: G
authors.initials: G
authors.lastname: Andrikopoulos
authors.forename: E
authors.initials: E
authors.lastname: Lazaki
authors.forename: J
authors.initials: J
authors.lastname: Gialafos
authors.forename: M
authors.initials: M
authors.lastname: Malik
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results