The aim of the study was to evaluate the correlation between the degree of QT dispersion (QTd) and ventricular tachycardia (VT) or fibrillation (VF) in patients (Pts) with acute myocardial infarction (AMI) and particularly to verify the potential correlation between QTd and the onset of VT/VF. For this purpose we evaluated 97 PTs, 78 male and 19 female, with mean age 63 +/- 10, admitted consecutively to the CCU because of AMI. 44 Pts (45.3%) were treated with fibrinolythic therapy. In every PT we estimated through a computerized system (HP M1700A) the duration of the QT interval in each of the 12 standard leads of the surface ECG. The value of QTd was estimated by subtracting the lowest value of QT from the highest. In order to avoid miscalculation due to artefacts or low amplitude T waves, we estimated the value of QTd by analyzing ten leads excluding the highest and lowest value of 12 leads and those values with a T wave less than 0.15 mvolt. QTd was calculated daily for the first 4 days. We excluded from the study PTs with arrhythmias, or large QRS complex at the ECG or contemporary therapy with drugs that can change the QT and PTs over 80 years in age. Results: 13 Pts (13%) had VT/VF during AMI (group 1) and 84 PTs (86%) did not have VT/VF (group 2). The average value of QTd in groups 1 and 2 respectively was: admission 67 ms vs. 43 ms (p < 0.0001), 1st day 76 ms vs. 59 ms (p < 0.01), 2nd day 56 ms vs. 49 ms (p = ns), 3rd day 59 ms vs. 44 ms (P < 0.5) 4th day 52 ms vs 42 ms (P < 0.5). No significant difference in Qtc duration was observed between the two groups of PTs. The correlation between the occurrences of the arrhythmia episodes and QTd is shown in the figure.Discussion: high values of QTd appear to be linked to high rate of occurrence of VT/VF during AMI considering that PTs of group 1 had significantly higher value of QTd than Pts of group 2. We observed 92% of the total VT/VF episodes during days 1 and 2, the days in which QTd was greatest. Conclusion: Elevated values of QTd are correlated with high incidence of VT/VF during AMI.