Diagnostic performance and partition values of exercise electrocardiographic variables in the detection of coronary artery disease – improved accuracy by using ST/HR hysteresis

Exercise electrocardiography is widely used for initial identification of patients with coronary artery disease (CAD). This study compares the measurements of ST-segment changes during exercise and during early postexercise recovery in terms of diagnostic discrimination capacity and optimal partition values. Data from 1876 patients undergoing a routine bicycle exercise test were analysed. CAD was angiographically verified in 668 patients, and excluded by angiography (n = 119), myocardial scintigraphy (n = 250), and on clinical grounds (n = 839) in 1208 patients. Postexercise ST/HR hysteresis was calculated as normalized for heart rate (HR) ST/HR loop area during the first 3 min of recovery. ST/HR index was obtained by dividing the overall ST amplitude change during exercise by exercise-induced HR change, and ST/HR slope was calculated using linear regression analysis of ST/HR data pairs during exercise. ST-segment depression was measured during, and for 3 min after the exercise. Discriminating capacity of the methods was evaluated in terms of receiver operating characteristic areas and optimal partition values providing the combination of the best sensitivity and specificity were established. The best diagnostic discrimination was provided by ST/HR hysteresis at optimal partition value of -15 microV, followed by postexercise ST amplitude measurements at gender-specific partition values of -10 to -90 microV, ST/HR slope [partition value 2.4 microV (beats/min)(-1)], ST/HR index [partition value 1.6 microV (beats/min)(-1)], and ST-segment depression during exercise (partition value 70 microV in men and 90 microV in women). The results demonstrate that analysis of postexercise ST/HR hysteresis offers the most accurate and gender indifferent identification of patients with CAD.