QT dispersion and early arrhythmic risk in acute myocardial infarction.

ABSTRACT

BACKGROUND: This study sought to find out QT dispersion in healthy individuals and patients of acute myocardial infarction and to find correlation, if any, between QT dispersion and the incidence of ventricular arrhythmias in acute myocardial infarction. METHODS AND RESULTS: QT dispersion was calculated from a 12-lead electrocardiogram in 100 patients of acute myocardial infarction admitted in intensive coronary care unit and 100 age- and sex-matched healthy individuals. In patients of acute myocardial infarction, QT dispersion was calculated on admission, 24 hours after admission and at the time of discharge from intensive coronary care unit. Average QT dispersion in acute myocardial infarction was found to be significantly higher on admission (76.4 +/- 18.3 ms), 24 hours after admission (62.88 +/- 17.52 ms) and at the time of discharge from intensive coronary care unit (51.79 +/- 16.79 ms) than in healthy individuals (29.76 +/- 6.06 ms; p<0.05). QT dispersion was found to be significantly increased in patients of acute myocardial infarction with ventricular arrhythmias (82.06 +/- 16.86 ms) than in those without (66.75 +/- 16.28 ms; p<0.01). Patients of acute myocardial infarction with ventricular tachycardia or ventricular fibrillation had significantly increased QT dispersion (96.25 +/- 15.97 ms) than those who had only ventricular premature beats (80 +/- 15.04 ms; p<0.01). QT dispersion was found to be significantly greater in patients with anterior wall acute myocardial infarction (79.80 +/- 18.19 ms) than in those with inferior wall acute myocardial infarction (71.9 +/- 17.48 ms; p<0.05). At the time of discharge from intensive coronary care unit no statistically significant difference was found in QT dispersion in those who received thrombolysis (51.58 +/- 16.05 ms) and those who did not (48.18 +/- 14.68 ms; p>0.05). QT dispersion was found to be significantly higher in those who died (88.66 +/- 15.97 ms) than in those who survived (74.23 +/- 17.91 ms; p<0.05). QT dispersion was significantly higher in ventricular arrhythmic deaths (97.14 +/- 17.04 ms) than those who had non-arrhythmiac deaths (81.25 +/- 11.25 ms; p<0.05). CONCLUSIONS: Interlead QT variation and its measure as QT dispersion challenges our current approach to the electrocardiographic assessment of arrhythmic risk. QT dispersion may provide a potentially simple, cheap, non-invasive method of measuring underlying dispersion of ventricular excitability.