Changes in QT dispersion during adenosine infusion

Background: QT dispersion (QTd) measurement during treadmill stress testing has been to shown to improve the accuracy of exercise electrocardiogram (E CG) in the detection of significant coronary artery disease (CAD). Hypothesis: The aim of this study was to determine whether adenosine-induce d changes in QTd could predict significant CAD and to assess its efficacy a s a diagnostic index in patients undergoing adenosine stress test. Methods: QT interval measurements were made in 57 consecutive patients unde rgoing adenosine sestamibi stress test. Patients with an abnormal stress te st underwent coronary angiography. Patients with significant disease by cor onary angiography (> 70% stenosis) were classified as having CAD (Group 1), and those with normal stress images and/or normal coronaries by angiograph y were classified as having no CAD (Group 2). Results: QT dispersion increased from 28.2 +/- 4.5 to 43.8 +/- 4.5 ms with a Delta QTd of 15.53 +/- 3.68 in Group 1 (p = 0.001) and from 28.9 +/- 2.6 to 34.8 +/- 2.8 ms with a Delta QTd of 6.58 +/- 2.21 ms in Group 2 (p = 0.0 06). Patients in Group 1 had a significantly higher increase in QTd (Delta QTd) than the patients in Group 2 (p < 0.03). Addition of Delta QTd (> 10 m s) to the ST depression during adenosine infusion would increase the sensit ivity of the ECG from 23 to 65% and decrease the specificity from 91 to 70% for diagnosis of significant CAD. Conclusions: Delta QTd is significantly more prolonged in patients with CAD during adenosine infusion. It increases the sensitivity of the stress ECG in diagnosis of CAD during adenosine infusion when used as an adjuvant inde x.