RESUMO
OBJECTIVES: QT dispersion(QTd) is defined as the difference between the maximum and minimum average QT interval in any of the 12 leads of the surface ECG. QTd has been shown to reflect regional variations in ventricular repolarization. It was reported previously that QTd was dependent on the degree of reperfusion in myocardial infarction. The purpose of this study is to investigate the effects of percutaneous transluminal coronary angioplasty(PTCA) on QTd. METHODS: We studied in 21 patients(15 men and 6 women: mean age, 53 +/- 7.5 years: 14 acute myocardial infaction, 4 angina pectoris and 3 unstable angina). All standard 12-lead ECGs were recorded at a paper speed of 25mm/sec and examined retrospectively by single observer. QT interval was measured from 11.3 +/- 1.1 leads using a computerized program interfaced with digitizer. QTd corrected for heart rate(QTcd) was calculated by Bazett`s formula. Each cases were divided to 2 stages, before and after PTCA(mean obsevation duration, 16.8 +/- 9.7 days vs. 22.5 +/- 21.9 hours). The difference of QT dispersions was assessed by comparing by paired t-test. RESULTS: There were significant difference in QTd (mean 110.2 +/- 37.4 vs. 90.4 +/- 37.6 msec, p<0.05). Results did not change when Bazett`s QTc was substituted for QT(QTcd: mean 125.5 +/- 38.3 vs. 97.9 +/- 29.8 msec, p<0.05). CONCLUSION: Successful PTCA is associated with less QTd after PTGA. The results are equally significant when either QT or QTc is used for analysis. In our limited study, measurement of QT dispersion, an easily accessible, resonably accurate, noninvasive method, may be a valuable tool in assessment of patients before and after PTCA. However, this study must be confirmed in prospective trial.