Comparison of the spatial QRS-T angle derived from digital ECGs recorded using conventional electrode placement with that derived from Mason-Likar electrode position

• Holter ECGs are increasingly used in clinical research studies to evaluate ECG parameters, such as spatial QRS-T angle.
• Spatial QRS-T angle derived from orthogonal leads reconstructed from two lead systems (digital 12-lead ECGs and digital Holter ECGs recorded with Mason-Likar electrode positions) has been compared.
• Small but statistically significant difference was found in the mean spatial QRS-T angles derived from the two lead systems.
• This difference needs to be considered while assessing individuals with abnormally high QRS-T angles.

BackgroundThe spatial QRS-T angle is ideally derived from orthogonal leads. We compared the spatial QRS-T angle derived from orthogonal leads reconstructed from digital 12-lead ECGs and from digital Holter ECGs recorded with the Mason-Likar (M-L) electrode positions.Methods and resultsOrthogonal leads were constructed by the inverse Dower method and used to calculate spatial QRS-T angle by (1) a vector method and (2) a net amplitude method, in 100 volunteers.Spatial QRS-T angles from standard and M-L ECGs differed significantly (57° ± 18° vs 48° ± 20° respectively using net amplitude method and 53° ± 28° vs 48° ± 23° respectively by vector method; p < 0.001). Difference in amplitudes in leads V4–V6 was also observed between Holter and standard ECGs, probably due to a difference in electrical potential at the central terminal.ConclusionMean spatial QRS-T angles derived from standard and M-L lead systems differed by 5°–9°. Though statistically significant, these differences may not be clinically significant.