Effects of atrial pacing on QT dispersion in patients with coronary arterydisease without angina pectoris and ST segment depression

The aim of this study was to investigate QT dispersion during atrial pacing in patients with coronary artery disease (CAD) without clinical ischemia, such as angina pectoris and ST segment depression. Thirteen patients with n ormal coronary arteries and 42 patients with CAD (12 with single-vessel, 16 with two-vessel and 14 with three-vessel disease) having no angina pectori s or ST segment depression during atrial pacing with maximum rate of 120/mi nute were enrolled in the study. Twelve-lead surface ECGs were recorded at 100 mm/second paper speed before pacing, at maximum pacing rate, and during the recovery period for measurement of QT interval parameters. Corrected QTd (QTcd) increased from 43.4 +/- 8.1 to 49.3 +/-9.5 ms (p<0.05) in the control group, from 46.1<plus/minus>8.1 to 74.3 +/-7.7 ms (p< 0.000 1) in the single-vessel disease group, from 48.5 +10.4 to 93.8<plus/minus>2 2.1 ms in the two-vessel disease group (p < 0.0001), and from 49.7<plus/min us>13.6 to 128.5 +/- 31 ms (p< 0.0001) in the three-vessel disease group at peak atrial pacing period. A positive correlation was found between the se verity of CAD and QTcd (r= 0.49, p < 0.0001). It was found that pacing-indu ced QTc dispersion identifies coronary disease extent, even when there is n o ST depression or T wave inversion during pacing.