Interpretation of the Master "2-Step" Exercise Electrocardiogram by Quantitative Analysis of RS-T Segment

Abstract

1) There is a statistically valid difference in the nature of depressed RST segment after the “2-Step” test, among functional cases vs. those with ischemic heart disease. In presence of coronary heart disease, the depression persists for greater portion of ventricular complex than in functional cases. The QX/QT ratio is a simple and convenient expression of this characteristic of the RS-T segment and corrects for changes in heart rate. 2) A QX/QT ratio of 50% appears the optimal point at which to separate organic from functional cases. In 100 patients with known coronary heart disease, 99% demonstrate QX/QT ratios of 50% or more. Using this criterion, total incidence of false positive responses is 12% but with only 4.7% false reactors occurring among men. The overall accuracy of the criterion in both organic and functional cases with RS-T depression is 92.8% in our series. 3) It is suggested that criteria of an abnormal “2-Step” test should henceforth include a QX/QT ratio of 50% or more.