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Objective: To investigate the changes and diagnostic value of QT dispersion (QTd) for patients with coronary artery disease during cardiac stress testing (CST) by transesophageal atrial pacing (TEAP). Methods: Forty two consecutive inpatients underwent CST by TEAP firstly, then accepted selective coronary atreriography (SCA) by Judkins method. Patients were divided into two groups according the results of SCA, i.e. 24 cases in coronary artery disease group (CAD) and 18 cases with normal coronary artery (NCA). Measurements of QTd in two groups before and after CST were analyzed in and between groups. Applying the results of SCA as the golden standard, we compared the diagnostic efficiency for CAD between ST-segment depression~O.1mV criteria and QTd~6Oms criteria. Results: CAD group had a higher QTd than NCA group at baseline or every stages after CST (P<O.05-O.O1); in CAD group, QTd immediately and 2mm after CST was significantly greater than before CST (P<O.O1, respectively), but QTd 4mm and 6mm after CST dropped by the baseline (P~O.O5, respectively). In NCA group, there were no differences of QTd measurements to be observed before and every stages after CST (P~O.O5, respectively). CAD group was subdivided into groups (three-, two-, single-vessel group) according to the numbers of their stenosed vessels~ and no significant differences in QTd measurements were observed compared among the three subgroups both before and after CST(P>O.05, 3 respectively),but each subgroup had a greater QTd immediately or 2mm after CST than that before(P<O.O1,respectively).The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of ST- segment depression criteria for diagnosis of CAD were 5Q昋O/~, 77.80/o, 75.O0/o, 53.8%, and 6 1.9%, respectively; measurement of QTd immediately or 2mm after CST ( ~ 6Oms: positive)with the sensitivity (87.5%), specificity(94.4%), positive predictive va I ue(95. 5%), negative predictive value(85.O%) and accuracy(90.5%). But compared with the ST-segment depression criteria, QTd ~ 6Oms criteria significantly elevated the sensitivity (p=O.0114),negative predictive value ( P=O.0314) and accuracy (P=O.0041). Conclusion: Patients with CAD have greater QTd than normal subjects; and QTd increased further in CAD during CST by TEAP, whereas, NCA with no significant change. But QTd has no definite correlation with the numbers of stenosed coronary arteria. Measurements of QTd can elevate the sensitivity, decrease the false negative rate, and improve accuracy of CST by TEAP for diagnosis of CAD. QTd may be an effective index for myocardial ischemia during the test.
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