Measurement variables for optimal performance of the ST integral
PM Okin,
G Bergman,
and
P Kligfield
Department of Medicine, New York Hospital-Cornell Medical Center, New York 10021.
OBJECTIVES. This study examined the effect of varied onset and offset of ST measurement on performance of the ST integral for the detection of coronary artery disease. BACKGROUND. The J point and other early ST segment measurements may significantly reduce the accuracy of ST segment depression criteria. METHODS. The exercise electrocardiograms (ECGs) from 112 normal subjects and 163 patients with known or likely coronary disease were analyzed, using the J point or 20 ms after the J point onset and 60 or 80 ms after the J point offset of ST integral calculation. RESULTS. At a matched specificity of 97%, incorporation of J point measurements into the ST integral significantly reduced test performance. The ST integrals measured from the J point to 80 and to 60 ms after the J point were significantly less sensitive (31% and 25%, respectively) than those measured from 20 to 80 ms and 20 to 60 ms after the J point (39% and 31%, p < 0.001 and p < 0.01, respectively). For either J point or 20 ms after the J point onset of the ST integral measurement, the sensitivity was higher using 80 ms than 60 ms after the J point offset (31% vs. 25%, p < 0.01 and 39% vs. 31%, respectively, p < 0.001). Comparison of areas under receiver operating characteristic curves confirmed the superior performance of the ST integral measured from 20 to 80 ms after the J point relative to the other measurement intervals. CONCLUSIONS. These findings demonstrate that J point and early repolarization phase time-voltage measurements reduce performance of the ST integral for the identification of coronary artery disease and provide further evidence that optimal signal to noise content of repolarization for the identification of ischemia can be localized to later phases of the ST segment.
