The change in QT dispersion (QTd) immediately after balloon angioplasty reflects the immediate impact of ischemia. We intended to analyze the immediate impact of ischemia on myocardial repolarization.

Forty-six patients who underwent percutaneous coronary intervention were enrolled. The standard 12-lead electrocardiogram (ECG) was recorded just before, during, and 1 minute, 5 minutes and 10 minutes after ballooning. QTd was determined by the difference between the maximum and minimum QT interval (QTi). We then calculated the corrected QTi (QTc) using Bazett's formula. QTd and QTi were compared according to the site of the ballooned vessel, number of ballooned vessels and history of acute myocardial infarction.

QTd just before, during, and 1 minute, 5 minutes and 10 minutes after ballooning were 35.21±10.36 msec, 54.56±16.89 msec, 50.91±14.20 msec, 45.52±9.6 msec and 38.56±10.89 msec, respectively. QTd increased markedly during ballooning, but after myocardial ischemia was relieved, decreased rapidly. Ten minutes after ballooning, QTd was reduced to a similar level as that of baseline. There were no significant differences between the AMI and non-myocardial infarction groups, single-vessel and multi-vessel groups, and the location of the stenosed artery. There was no significant difference in QTi according to different stenosed vessel.

QT (QTc) dispersion increased rapidly with myocardial ischemia and reduced rapidly after the myocardial ischemia was resolved. Therefore, increased QTd can be used as an early clue of myocardial ischemia.