To determine the characteristics of QT interval dispersion using orthogonal
ECG leads with high paper speed (100 mm/s) and high voltage gain (10 cm/mV
) as compared to conventional 12-lead EGG, we measured the QT dispersion in
57 patients at rest and directly after exercise using these two techniques
. The measurements were repeated by the same observer and by an independent
observer in 29 patients to assess reproducibility. QT dispersion was found
to be significantly lower in orthogonal leads than standard lead tracings
(24 +/- 20 ms versus 44 +/- 17 ms at rest, P < 0.001; 29 <plus/minus> 21 ms
versus 53 +/- 27 ms after exercise, P < 0.001, respectively). The intrasub
ject and interobserver reproducibility was better for the orthogonal lead t
racings, making this technique a potentially useful tool for future researc
h. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.