| Objective (1)To investigate the effect of brief episodes of myocardial ischemia during the balloon inflation on QT dispersion(QTd) and their relationship with ventricular arrhythmias, and to evaluate if QTd may be improved in patients with coronary artery disease(CAD) by successful percutaneous transluminal coronary angioplasty (PTCA).(2)Serum cardiac troponin I (cTnI) and creatine kinase MB (CK.-MB) levels were monitored before and after PTCA to evaluate the effect of myocardial damage in the procedure on the recovery of QTd.Methods Fifty-one patients who have been diagnosed as CAD or suspectable CAD clinically underwent continuous 24 hours monitoring with 12-leads ambulatory electrocardiography during the day of PTCA or coromary angiography (CAG). QT and RR intervals were measured at baseline, during and instant after the first balloon inflation and 2 hours, 12 hours after successful PTCA. While with those who were not ungoing PTCA, QT and RR intervals were measured before. 2 hours and 12 hours after CAG. QTd was then calculated as the difference between the maximum and minimum QT interval (QTd = QTmax - QTmin).Serum cTnl and CK-MB were measured in all patients before and 12 hours after PTCA or CAG respectively.Result (1) QTd in the group of patients with CAD was significantly greater than that in the group of patients with normal coronary arteries at baseline(61.0± 12.0ms VS 28.7 ± 5.8ms.P<0.001).(2) In CAD patients, QTd decreased from 61.3 ± 11.6ms at baseline to 49.8 ± 9.5ms 2 hours after PTCA(P<0.001) and to 43.0 ± 7.6ms 12 hours after PTCA(P<0.001VS baseline). And there was significant difference between QTd determined 2 and 12 hours after PTCA(P<0.01). QTmin increased from 321.7 ± 28.4ms at baseline to 335.0 ±26.3ms2 hours after PTCA(P<0.001)and to 340.2 ± 25.7ms 12 hours after PTCA(P<0.001 VS baseline).But there was no significant difference between the groups with single-vessel and multivessel disease in QTd at baseline(57.7± 7.9ms VS 65.6 + 14.2ms, P>0.05).after 2 hours(49.1 ± 10.1ms VS 50.6 ± 9.3ms. P>0.05) or 12 hours(43.8±5.8ms VS 42.0±9.7ms, P>0.05). There was no significant difference in QTd before, 2 hours and 12 hours after CAG in non-PTCA group(60.3 + 13.8 VS 60.9 +13.0 VS 57.9+14.3,P>0.05).(3) During the first balloon inflation, QTd increased(61.3 +11.6ms to 72.8 + 14.3ms, P<0.05) and QTmin decreased(321.7 ±28.4ms to 309.3 +26.8ms, P<0.05) significantly.(4)There were no malignant ventricular arrhythmias during occlusion,except in two patients with ventricular extrasystole and one patient with ventricular extrasystoles in bigeminy out of 22 patients.(5) cTnl increased from 0.085± 0.087ug/L at baseline to 0.112 ± 0.108μg/L 12 hours after PTCA(P<0.01). There was significant difference in ΔQTd(ΔQTd = baseline QTd - QTd at 12 hours) between patients with or without cTnl increasing(13.1 ± 9.1 VS 27.4 ± 17.5ms, P<0.05).Conclusion (1) QTd increase in patients with CAD.but there is no significant difference between the groups with single-vessel and multivessel disease.(2) QTd would be improved by successful PTCA in patient with single-vessel or multivessel disease.The improvement is the result of a increase in QTmin.(3)Acute transient myocardial ischemia provoked by intracoronary balloon inflation during PTCA increases QTd by reducing the Qtmin which could produce ventricular arrhythmia, but malignant ventricular arrhythmia was rarely occurred.
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