title: Comparison between ventricular gradient and a new descriptor of the wavefront direction of ventricular activation and recovery.
abstract: BACKGROUND
  Total R T cosine (TCRT) is a new descriptor of repolarization heterogeneity that quantifies the deviation between the directions of ventricular depolarization and repolarization. It revives the old concept of ventricular gradient (VG).
  
  
  OBJECTIVE
  Our goal was to examine whether TCRT and VG contain nonredundant information by comparing their reaction to autonomic tests, namely, postural changes and Valsalva maneuver.
  
  
  METHODS
  Digital 12-lead electrocardiograms were recorded in 16 patients with cardiovascular syndrome X (SX, chest pain, exercise-induced ST-depression, normal coronary arteries, 3 men, age 60 +/- 9 years) and 40 healthy volunteers (31 men, age 33 +/- 7 years) during postural changes and Valsalva maneuver. The angle (VGA) [degrees] and magnitude (VGM) [ms.mV] of VG in reconstructed XYZ leads and TCRT (average cosine of the angles between the QRS and T vectors in mathematically reconstructed three-dimensional space) were calculated.
  
  
  RESULTS
  (mean +/- standard of the mean): In healthy subjects, VGM and TCRT decreased, whereas VGA increased in the sitting and standing compared with supine position (TCRT: 0.61 +/- 0.05,0.47 +/- 0.06,0.29 +/- 0.08, supine, sitting, and standing, p < 0.05) and during phase II Valsalva (TCRT: 0.47 +/- 0.06 vs. 0.61 +/- 0.05, p < 0.01 in supine, 0.24 +/- 0.08 vs. 0.37 +/- 0.07, p < 0.01 in standing). In patients with SX, VGM decreased in the standing position, VGA did not change significantly, while TCRT decreased only in patients without T-wave abnormalities (n = 9) (TCRT in standing and supine: 0.55 +/- 0.09 vs. 0.68 +/- 0.08, p < 0.05). VG(M) increased during Valsalva in patients with SX. Total R T cosine correlated strongly with VGA (r = -0.84, p < 0.00001) and, unlike VGM, did not correlate with heart rate.
  
  
  CONCLUSIONS
  Ventricular gradient and TCRT contain nonredundant information. In healthy subjects, they react sensitively to autonomic provocation. In patients with SX, their reaction is attenuated, which suggests disturbance of the autonomic control of repolarization.
authors.affiliation: Department of Cardiological Sciences, St George's Hospital Medical School, London, UK. vbatchva@sghms.ac.uk
authors.forename: Velislav
authors.initials: V
authors.lastname: Batchvarov
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Kaski
authors.forename: Nikhil
authors.initials: N
authors.lastname: Parchure
authors.forename: Polychronis
authors.initials: P
authors.lastname: Dilaveris
authors.forename: Sue
authors.initials: S
authors.lastname: Brown
authors.forename: Azad
authors.initials: A
authors.lastname: Ghuran
authors.forename: Patrik
authors.initials: P
authors.lastname: Färbom
authors.forename: Katerina
authors.initials: K
authors.lastname: Hnatkova
authors.forename: A John
authors.initials: AJ
authors.lastname: Camm
authors.forename: Marek
authors.initials: M
authors.lastname: Malik
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D017566:Microvascular Angina / Q000503:physiopathology*; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014636:Valsalva Maneuver / Q000502:physiology