title: A simple procedure for estimation of the spatial QRS/T angle from the standard 12-lead electrocardiogram.
abstract: The spatial QRS/T angle has been identified as a strong predictor of adverse cardiac events. Mean QRS and T amplitudes from X, Y, and Z leads generated by a matrix transformation method are often used to calculate the QRS/T angle (QRS/T(matrix)). Many investigators find this procedure cumbersome. We used electrocardiographic data files of 14881 men and women aged 45 to 65 years from the Atherosclerosis in Communities study to derive a simple formula for estimated spatial QRS/T angle (QRS/T(simple)). QRS/T(simple) is calculated as the inverse cosine between the mean QRS and T vectors, which are approximated by 3 QRS(net) and T(net) amplitudes for each vector. QRS/T(simple) explained 79% of the variance of QRS/T(matrix) (r = 0.89). Using sex-specific thresholds, QRS/T(simple) detected abnormally wide QRS/T(matrix) values with a sensitivity of 91% and specificity of 88%. It is concluded that this simple method may provide a satisfactory substitute for QRS/T from the matrix transformation method.
authors.affiliation: Epicare Center, Division of Public Health Sciences, Wake Forest University School of Medicine, Winston Salem, NC, USA. penttir@bellsouth.net
authors.forename: Pentti M
authors.initials: PM
authors.lastname: Rautaharju
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Prineas
authors.forename: Zhu-Ming
authors.initials: ZM
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000465:Algorithms; D018780:Body Surface Potential Mapping / Q000379:methods*; D003324:Coronary Artery Disease / Q000175:diagnosis*; D016208:Databases, Factual; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D016247:Information Storage and Retrieval / Q000379:methods; D008297:Male; D008875:Middle Aged; D011785:Quality Assurance, Health Care / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity