R-wave amplitude responses to rapid atrial pacing: A marker for myocardial ischemia☆

Abstract Atrial pacing-induced changes in the sum of R-wave amplitude were measured in leads V 5 , X, Y, and Z at rates of 100 bpm (phase I), 150 bpm (phase II), and immediately after pacing (phase III) in 33 patients undergoing cardiac catheterization for evaluation of chest pain. Seventeen (51%) patients showed evidence of ischemia during atrial pacing (typical anginal pain and/or at least a 1 mm ST-segment depression) and 16 (49%) showed no evidence of ischemia. Mean R-wave amplitude changes from baseline in the ischemic patients were: phase I; −8% ( p = not significant), phase II: +3% ( p = not significant), and phase III: +13% ( p p p p = not significant). These two distinct patterns of R-wave amplitude changes were highly sensitive (85%), specific (92%), and predictive (92%) for identifying patients with myocardial ischemia but did not correlate ( p = not significant) with either the angiographically determined extent of coronary artery obstructive disease (CAD), resting left ventricular function, or the dynamic, atrial pacing-induced changes in left ventricular dimensions determined by M-mode and two-dimensional echocardiography. Thus, R-wave amplitude changes induced by atrial pacing can be used to identify patients with myocardial ischemia independent of coronary anatomy or resting left ventricular function. In addition, it appears that R-wave amplitude variations during atrial pacing-induced myocardial ischemia are not directly related to left ventricular volume changes.