QT Dispersion Does Not Predict Early Ventricular Fibrillation After Acute Myocardial Infarction

Ventricular arrhythmias may be associated with increased QT dispersion (difference between maximum and minimum QT on standard 12-lead ECG). We performed a case control study to determine if QT dispersion on the admission ECG could predict early VF after acute myocardial infarction. The cases were 24 patients with acute myocardial infarction (14 inferior, 8 anterior, and 2 lateral) with VF within 12 hours of admission. There were 24 control patients without VF matched for site of infarction and ST segment score (sum of ST segment elevation). VF occurred a median of 153 minutes (interquartile range 93-245) after onset of chest pain and 33 minutes (range 7-104) after initial ECG. QT (399 +/- 37 and 394 +/- 37), QT corrected (440 +/- 38 and 429 +/- 29), and QT dispersion (68 +/- 20 and 66 +/- 27) were similar in patients and controls. By design, ST score was similar (11 +/- 9 vs 9 +/- 5 mV), although a good match could not be obtained for three patients with extreme ST elevation. Patients with VF presented to the hospital earlier after the onset of chest pain (median 95 min range 65-188 compared to 150 min range 80-270, P = 0.05) and had a lower serum sodium (138 +/- 2.4 vs 140 +/- 2.5, P = 0.05) than controls. Thus, QT interval and QT dispersion, measured on the presenting ECG, did not predict early VF after myocardial infarction.