QT-interval dispersion in acute myocardial infarction is only shortened by thrombolysis in myocardial infarction grade 2/3 reperfusion

BACKGROUND: Increased QT interval dispersion (QTd) has been found in patients with acute myocardial infarction (AMI). In previous studies this has been shown to decrease with thrombolysis. HYPOTHESIS: The aim of this study was to compare the effects of reperfusion by primary percutaneous transluminal coronary angioplasty (PTCA) and by thrombolysis on QTd and correlate these results with the degree of reperfusion. METHODS: We studied 60 patients with a first AMI. The study cohort included 40 consecutive patients who had received thrombolysis (streptokinase or rt-PA); 20 additional consecutive patients with successful primary PTCA, all with preselected Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow by predefined selection criteria (12 stents); and 20 controls. A 12-lead ECG for QTd calculation was recorded before thrombolysis or PTCA and immediately after the procedure. All values were corrected according to Bazett's formula (QTcd). QTd and QTcd values before and after each procedure in three groups and the respective percent changes of deltaQTd and deltaQTcd were compared separately. RESULTS: QTd and QTcd were significantly increased before thrombolysis/PTCA versus normals. An angiogram performed after thrombolysis showed adequate reperfusion (TIMI grade 2/3) in 20 patients, while in the other 20 only TIMI 0/1 reperfusion was achieved. Thrombolysis-TIMI flow 2/3 and PTCA significantly reduced QTd (from 68 +/- 10 to 35 +/- 8 ms, p < 0.001, deltaQTd = 48 +/- 11%, in the Thr-TIMI flow 2/3 group,and from 79 +/- 11 to 38 +/- 9 ms, p < 0.001, deltaQTd = 52 +/- 9%, in the PTCA group), while in the Thr-TIMI flow 0/1 group no significant changes were recorded. A percent QTd decrease > 30 s had 96% sensitivity, 85% specificity, and 93% positive and 94% negative predictive value, respectively, for TIMI 2/3 flow. CONCLUSIONS: A significant decrease in QT dispersion may provide an additional electrocardiographic index for successful (TIMI 2/3) reperfusion.