Quantitative evaluation of exercise-induced ST-segment depression for estimation of degree of coronary artery disease.

Comparative analysis of coronary arteriography and exercise ECG recordings of 33 patients with ischaemic heart disease is presented. Linear regression was found between the increase of heart rate (HR) as well as increase of systolic blood pressure-heart rate product (SBP X HR) and the level of ST-segment depression developing during exercise. A significant correlation was established between the slope of the regression line (i.e. 'm' coefficient of y = mx + b) expressing the rate of change of ST-segment depression and the degree of coronary artery disease confirmed by arteriography. The average value of 'm' coefficients differed significantly according to the number of diseased vessels (P less than 0.01-0.001). The ratio of maximal ST depression and maximal HR (STmax/HRmax) measured at the end of the exercise indicated reliably the severity of coronary artery disease and is suggested for everyday practice.