Prediction of severity of coronary artery disease using slope of submaximal ST segment/heart rate relationship

Abstract

A new exercise electrocardiography test has been examined in patients with angina pectoris; the rate of development of ST segment depression with respect to increases in heart rate during exercise on a bicycle ergometer was measured during exercise using 13 leads in 64 patients. The steepest slope of regression lines relating displacement of ST segment to increases in heart rate (maximal ST/HR slope) was used as an index of myocardial ischaemia and was compared with the results of coronary angiography which were determined by the radiologists and the cardiologist responsible for the management of these patients. The maximal ST/HR slope could be derived consistently from a linear ST/HR relationship (r greater than 0.95) only in 50 patients with significant coronary artery disease (greater than or equal to 75% liminal narrowing). The ranges of the maximal ST/HR slope in 17 patients with single-vessel disease, in 18 patients with double-vessel disease and in 15 patients with triple-vessel disease were different from each other and the differences between the means were statistically significant (P less than 0.0005). The maximal ST/HR slopes for the patients with single-vessel disease were also different from those in the 14 patients in whom significant coronary disease could not be demonstrated. In contrast, the criteria of heart rate at which ST segment depression began, maximum ST segment depression, rate-pressure product and heart rate attained at the end of the test showed an overlap between the groups of the patients studied; using the usual exercise test criteria in the same population, there were three false negative results, one false positive result and the results in eight of the patients were indeterminate. It is concluded that the maximal ST/HR slope, used as an index of myocardial ischaemia, reliably predicted the presence and severity of coronary artery disease, as determined by coronary arteriography in each of the patients with anginal pain.

Recovery-phase patterns of ST segment depression in the heart rate domain. Identification of coronary artery disease by the rate-recovery loop.

“…Sensitivity of the rate-recovery loop appears to be relatively independent of the extent of coronary artery disease (Table 3), unlike the performance of standard ST segment criteria2,9,10 and heart rate-adjusted ST segment criteria that are derived from exercise-phase data alone. 15 Although our data show that the counterclockwise rate-recovery loop is a sensitive marker for coronary artery disease, the relation of these findings to prognostically important myocardial ischemia remains to be clarified. Because we did not measure myocardial ischemia per se, the mechanisms governing the direction of rate-recovery loops in our patients with angina32-36 can only be speculated.…”

Exercise Electrocardiogram Testing

“…Methodologies of the linear regression-based ST segment/heart rate (ST/HR) slope and the simpler ST/HR index have been detailed elsewhere. 18,23,[32][33][34][35] Much of the improved sensitivity results from correct classification of threshold levels of upsloping ST-segment depression that is classified as "equivocal" because upsloping depression is common in normal subjects. 18,36 Heart rate adjustment of subthreshold ST depression Ͻ0.1 mV also results in correct classification of "false-negative" tests, but this will only occur when STsegment measurement is precise.…”

Heart rate adjustment of ST segment depression for improved detection of coronary artery disease.

“…By normalizing ST segment depression for corresponding changes in myocardial workload at peak exercise, the ST segment/heart rate (ST/HR) slope has been shown to markedly improve the accuracy of bicycle exercise testing for identifying and quantifying coronary disease. [7][8][9][10][11][12] Indeed, several retro-entered into one of four clinical groups, which included two groups with a low likelihood of coronary disease and two with a high (or certain) likelihood of disease. ST/HR slope and zAST/HR index partitions defining the upper 95th percentile limits of normal were determined in normal subjects and were further tested in subjects with nonanginal chest pain.…”