DIAGNOSTIC-ACCURACY OF HEART RATE-ADJUSTED ST SEGMENTS COMPARED WITH STANDARD ST-SEGMENT CRITERIA

We compared the accuracy of ST segment/heart rate (ST/HR) index with t hat of standard criteria (greater than or equal to 0.1 mV horizontal/d ownsloping ST depression 80 ms after the J point) in 121 patients who had undergone angiography (49 with greater than or equal to 1 lesion w ith greater than or equal to 50% stenosis) and 50 clinically normal su bjects. All exercise tests used the Cornell protocol and computer meas urements of maximal ST depression 80 ms after the J point, Thresholds with equal specificity to standard criteria were determined for ST/HR index using each of the 2 normal groups (those who were normal by angi ography and those who were clinically normal). In using only patients who underwent angiography, we found that the ST/HR index had a sensiti vity that was not significantly greater than that of standard criteria (standard criteria 51%, ST/HR index 59%; p = 0.21), However, the rece iver-operating characteristic curve area increased from 64 +/- 4 to 68 +/- 4 (p < 0.02). When clinically normal subjects were used instead o f patients without angiographic disease, there was a clearly discernib le improvement in sensitivity of ST/HR index over standard criteria (s tandard criteria 51%, ST/HR index 69%; p < 0.05). The associated curve areas were 69 +/- 4 and 79 +/- 3 (p < 0.001), Therefore, accuracy of the ST/HR index was marginally better than standard criteria only in p atients who underwent angiography. When clinically normal subjects wer e used, the accuracy of the ST/HR index was definitely better than sta ndard criteria. We conclude that the demonstration of improved accurac y of the ST/HR index depends on the population being tested.