title: Frontal-plane QRS axis revisited: accuracy of current approximations and reappraisal of their merit in the diagnosis of right ventricular hypertrophy.
abstract: The frontal-plane mean QRS vector orientation (AQRSxy)--the so-called electrical axis--is an ECG feature commonly used for the diagnosis of right ventricular hypertrophy and is correctly measured by calculating the areas subtended by QRS deflections in two different leads. To overcome the drawbacks of doing this by hand, two alleged approximations of AQRSxy have become popular and are in current use: one is based on the measurement of QRS component wave peak amplitudes and the other on the estimation of the half-area vector of the frontal plane loop. The values obtained with the correct and the two more practical methods are compared and their diagnostic efficiency is assessed by means of a procedure for ECG criteria optimization based on the receiver operating characteristics (ROC) curve analyzed in terms of information theory. The authors conclude that the two more popular methods for AQRSxy determination provide similar values that, although correlated with the true measure of the parameter are statistically different from it. On the other hand, the diagnostic efficiency of AQRSxy alone, regardless of the method by which it is computed, is only as good as, if not bettered by, other much more easily measurable frontal-plane parameters (ie, left to rightward forces amplitude ratio in adults and rightward forces amplitude in pediatric patients).
authors.affiliation: University of Oporto, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Abreu-Lima
authors.forename: J P
authors.initials: JP
authors.lastname: Marques de Sa
authors.forename: G
authors.initials: G
authors.lastname: Coelho
authors.forename: J
authors.initials: J
authors.lastname: Almeida
authors.forename: F
authors.initials: F
authors.lastname: Silva-Carvalho
authors.forename: C
authors.initials: C
authors.lastname: Hernandez
mesh_terms: D000293:Adolescent; D000328:Adult; D006332:Cardiomegaly / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D008875:Middle Aged