title: Role of the vectorcardiogram-derived spatial QRS-T angle in diagnosing left ventricular hypertrophy.
abstract: BACKGROUND
  Current criteria for electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH) have a low diagnostic accuracy. Addition of demographic, anthropomorphic, and additional ECG variables may improve accuracy. As hypertrophy affects action potential morphology and intraventricular conduction, QRS prolongation and T-wave morphology may occur and become manifest in the vectorcardiographic variables spatial QRS-T angle (SA) and spatial ventricular gradient. In this study, we attempted to improve the diagnostic accuracy for LVH by using a combination of demographic, anthropomorphic, ECG, and vectorcardiographic variables.
  
  
  METHODS
  The study group (n = 196) was divided in 4 subgroups with, on one hand, echocardiographically diagnosed LVH or a normal echocardiogram and, on the other hand, with any of the conventional ECG signs for LVH or with normal ECGs. Each subgroup was randomly split into halves, yielding 2 equally-sized (n = 98) data sets A and B. Age, sex, height, weight, body mass index, body surface area (BSA), frontal QRS axis, QRS duration, QT duration, maximal QRS vector magnitude, SA, and ventricular gradient magnitude and orientation were univariate studied by receiver operating characteristic analysis and were used to build a stepwise linear discriminant model using P < .05 as entry and P > .10 as removal criterion. The discriminant model was built in set A (model A) and tested on set B. Stability checks were done by building a discriminant model on set B and testing on set A and by cross-validation analysis in the complete study group.
  
  
  RESULTS
  The discriminant model equation was D = 5.130 × BSA - 0.014 × SA - 8.74, wherein D greater than or equal to 0 predicts a normal echocardiogram and D less than 0 predicts LVH. The diagnostic accuracy (79%) was better than the diagnostic accuracy of conventional ECG criteria for LVH (57%).
  
  
  CONCLUSIONS
  The combination of BSA and SA yields a diagnostic accuracy of LVH that is superior to that of the conventional ECG criteria.
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Sumche
authors.initials: S
authors.lastname: Man
authors.forename: Chinar
authors.initials: C
authors.lastname: Rahmattulla
authors.forename: Arie C
authors.initials: AC
authors.lastname: Maan
authors.forename: Eduard
authors.initials: E
authors.lastname: Holman
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
authors.forename: Ernst E
authors.initials: EE
authors.lastname: van der Wall
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schalij
authors.forename: Cees A
authors.initials: CA
authors.lastname: Swenne
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D016002:Discriminant Analysis; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D012372:ROC Curve; D014672:Vectorcardiography / Q000379:methods*