Does expressing QT dispersion as a percentage of cycle length (QT dispersion ratio) improve the identification of patients who develop ventricular fibrillation compared to standard rate correction in patients with myocardial infarction?
Expressing QT dispersion as a ratio of cycle length may offer a better method than standard rate correction for predicting ventricular fibrillation in acute myocardial infarction.
QT dispersion is increased after myocardial infarction and levels are higher in patients with ventricular fibrillation. The changes in QT dispersion are dynamic and may reflect the changing pattern of underlying ventricular recovery of ventricular excitability, which is profoundly disturbed in the earliest phase of acute infarction. Expressing QT dispersion as a percentage of cycle length (QT dispersion ratio) rather than using standard rate correction may be superior in identifying patients who develop ventricular fibrillation.
Higham et al. (Sun,) studied this question.