The slope of ST segment/heart rate relationship during exercise in the prediction of severity of coronary artery disease

The results of a new excercise electrocardiography test werecompared with those of coronary arteriography in 120 patients.Thirty patients were under beta-blocker therapy and 90 patientswere not. In each patient the rate of progression of ST segmentdepression with respect to increases in heart rate was measuredin 13 electrocardiographic leads; the steepest slope of regressionlines relating ST segment depression to heart rate (maximalST/HR slope) was used as an index of myocardial ischaemia. Theresults of coronary angiography revealed 105 patients with significantcoronary artery disease (> 75% luminal narrowing); 32 patientshad single-vessel disease, 43 patients had double-vessel diseaseand 30 patients had triple-vessel disease. Significant coronaryartery disease could not be demonstrated in 15 patients. Theranges of the maximal ST/HR slope were different in the fourgroups of patients and the differences between the means werestatistically significant (P<0.0005); these differences weremaintained irrespective of beta-blocker therapy and there wereno false results or indeterminate test results. In contrastusing usual exercise criteria a definitive test result couldnot be obtained in 20 patients and there was an overlap betweenthe four groups. It is concluded that the maximal ST/HR slope can be used reliablyto predict the presence or absence and the severity of coronaryartery disease in individual patients with anginal pain, whetherthey are on beta-blocker therapy or not.