ST changes in relation to heart rate during bicycle exercise in patients with coronary artery disease

Exercise test on cycle ergometer and coronary angiography were performed on 190 patients with chest pain. Volunteers with a normal thallium scintigraphy (n = 47) served as controls. The load started at 20 W and increased at a rate of 10 W min-1 until exhaustion or symptoms. Conventional 12-lead ECGs were recorded by means of computer before, during and after exercise. Minimum ST amplitude 60 ms after the STJ point (ST60) at end of work with a cut-off level of -1.10 mm had a sensitivity of 69% (52/75) and a specificity of 89% (37/42) when individuals with a normal resting ECG were considered. ST80 and sum of ST60 in left ventricular leads had slightly lower values of sensitivity and specificity. Changes in ST60 during exercise discriminated less well between the groups. Final heart rate during exercise (less than 148 min-1) had a sensitivity of 88% (53/60) and a specificity of 89% (42/47). The change in heart rate during exercise (less than 66 min-1) had a sensitivity of 50/60 (only patients without beta-blockers were considered). The best discrimination was obtained by defining a test score (TS) according to the linear equation TS = 2.95-0.23 x HRE-0.301 X ST60 where a positive value indicates a positive test and a negative value a negative test. Sensitivity and specificity were 21/23 (91%) and 40/42 (95%), respectively. The test score was also calculated in those patients having significant coronary disease and an abnormal resting ECG (no bundle branch block, no beta-blockers) and this yielded a sensitivity of 30/34.