The QT interval
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QTc dispersion is emerging as an important ECG measure. It represents the difference between the longest and shortest QTc interval in the different leads of an ECG. It is simple but time consuming to calculate manually. Increased QTc dispersion reflects inhomogeneity in ventricular repolarization. QTc dispersion of >60 ms has been reported to have a 92% sensitivity and 81% specificity of predicting cardiac death in patients following a heart attack or those with chronic heart failure.