Dynamics of QT dispersion in acute myocardial infarction

We studied the dynamics of QT dispersion in patients with acute myocardial infarction, and compared them with those in controls.

Serial electrocardiograms of patients admitted to our institute with acute myocardial infarction were analyzed for QT dispersion, and compared with those of healthy age- and sex-matched controls. QT dispersion from 12 leads was measured as maximum QT minus minimum QT interval in ms. The mean QT dispersion of 114 +/- 29.6 ms was significantly higher in patients with acute myocardial infarction on admission as compared to 51.45 +/- 5.56 ms in controls (p < 0.001). QT dispersion showed a dynamic change in patients with acute myocardial infarction who were thrombolyzed, being 109.11 +/- 5.77 ms, 87.59 +/- 5.88 ms, 75.89 +/- 18.33 ms, and 68.20 +/- 12.66 ms on admission, post-thrombolysis, and on days 3 and 7, respectively. During a similar time period, nonthrombolyzed patients showed a QT dispersion of 132.38 +/- 36.04 ms, 130.47 +/- 34.42 ms, 111.11 +/- 24.94 ms, and 106.25 +/- 27.64 ms, respectively: the difference between the 2 groups at all periods was significant (p < 0.01). Mean QT dispersion values in patients who developed ventricular tachycardia or ventricular fibrillation were significantly higher than in patients who did not develop ventricular tachycardia or ventricular fibrillation (p < 0.01).

Mean QT dispersion is significantly increased after acute myocardial infarction, and shows a dynamic decrease with time, the difference being more marked in thrombolyzed patients. Mean QT dispersion levels are higher in patients with ventricular tachycardia and ventricular fibrillation compared to patients with acute myocardial infarction without these arrhythmias. The changes in QT dispersion are dynamic, and it may serve as a non-invasive marker of susceptibility to malignant ventricular arrhythmias.