QT Dispersion: Comparison of Orthogonal, Quasi-orthogonal, and 12-Lead Configurations

Background Full standardization of QT dispersion has not yet been established; the influence of lead combination is still disputed. This study evaluates the respective value of automated QTc dispersion in orthogonal (XYZ), quasi-orthogonal I-aVF-V2 (IF2), and 12-lead ECG configurations. Methods 15-lead digitized ECG recordings were collected in 92 normal subjects and in 71 patients following myocardial infarction. Each lead was processed by an automatic algorithm. QT dispersion was assessed by the range of individual QT intervals, both corrected by Bazett's formula. QTc durations from all configurations were comparable (post-MI: 412 ± 27 vs 407 ± 29 msec for 12-lead and XYZ). Whatever the set of leads, QTc interval was longer in post-MI (in 12-lead, 412 ± 27 vs 397 ± 19 ms in normals, P < 0.001). QTc dispersion was larger on 12-lead (post-MI: 51 ± 19, 21 ± 13 and 28 ± 20 ms with 12-lead, XYZ and IF2); however, it was significantly larger in post-MI with all sets of leads (in XYZ, 21 ± 13 vs 9 ± 7 ms in normal subjects, P < 0.0001). Conclusion In conclusion, magnitude of QT dispersion depends on the set of leads considered; orthogonal configurations may still contain valuable prognostic information.