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Figure 5 Agreement between automatic and manual measurement of QT dispersion in patients with hypertrophic cardiomyopathy. The differences between the measurements are plotted against the mean value from the two measurements. Most of the differences are within 2 SD from the mean differences (dashed line), which is approximately ±60 ms, obviously an unacceptably high measurement error. There is also no correlation between the two sets of measurements (r₂ = 0.00). (Reproduced with permission from Savelieva I, et al. Agreement and reproducibility of automatic versus manual measurement of QT interval and QT dispersion. Am J Cardiol 1998;81:471–7).