Comparison of the diagnostic accuracy of different methods of measurement of heart rate-adjusted ST-segment depression during exercise testing for identification of coronary artery disease

Within a population of 160 consecutive symptomatic patients who all had undergone catheterization (80 with ≥1 stenosis ≥50%), we compared the accuracy of different computerized measurements of the exercise-induced changes in ST-segment: (1) the standard criterion (≥0.l mV flat/downsloping ST depression or ≥0.15 mV upsloping depression, both 60 ms after the J point); (2) heart rate (HR)-adjusted ST-segment depression (ST/HR index measured at 0, 20, 40, 60, and 80 ms from the J point); (3) the HR-adjusted ST integral (ST/HR integral measured from 0 to 40 ms and from 40 to 80 ms after the J point). None of the ST/HR indexes or integrals were found to have a significantly greater sensitivity than the standard criterion. On the contrary, all ST/HR indexes and integrals showed a higher specificity (0.78 to 0.89) than did the standard criterion (0.65); moreover, the earlier the measurement within the repolarization phase, the better the overall accuracy: 0.71 for the standard criterion, 0.83 (p < 0.001), 0.80 (p < 0.01), 0.78 (p < 0.02), 0.78 (p < 0.02), 0.74 (p = NS) for the ST/HR indexes at 0, 20, 40, 60, and 80 ms, respectively; 0.81 (p < 0.001) and 0.78 (p < 0.02) for the ST/HR integrals calculated from 0 to 40 and from 40 to 80 ms, respectively. Consistently, the receiver-operating characteristic curve areas of ST/HR at 0, 20, and 40 ms were greater than those of ST/HR at both 60 and 80 ms. These findings are divergent from some other results given in published reports. We conclude that the accuracy of all exercise criteria is influenced by the population analyzed: our patients were representative of those currently seen by clinicians.