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Comparison of the spatial QRS-T angle derived from digital ECGs recorded using conventional electrode placement with
Vaibhav Salvi1, Elaine Clark2, Dilip R Karnad1
1Quintiles Cardiac Safety Services, Mumbai, India.
Background:
The 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 Results:
Orthogonal 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.
Conclusion:
Mean 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.
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