Usefulness of the QTc interval in predicting myocardial ischemia in patients undergoing exercise stress testing

Most recently, there has been great interest in the role of QT dispersion, a measure of interlead variations of the QT interval duration in the surfac e electrocardiogram. These variations are believed to reflect regional diff erences in repolarization heterogeneity and thus may provide an indirect ma rker of the potential for arrhythmia.(1,2) However, more basic contribution s to changes in PR segments or QT intervals during ischemia are less well c haracterized. Nonetheless, it seems reasonable to propose the use of the QT interval as a possible candidate for the assessment of ischemia, because i t reflects, within limits, the duration of depolarization and repolarizatio n. Furthermore, ischemia is known to prolong the QT interval due to its rel ation to the calcium flux during the cardiac action potential.(3) According ly, in this study we sought to address variations in the QTc segment in pat ients undergoing exercise stress testing for the diagnosis of coronary arte ry disease in an attempt to assess the sensitivity and specificity of this electrocardiographic variable in the detection of ischemia.