Qualitative and quantitative evaluation of the exercise electrocardiogram in assessing the degree of coronary heart disease.

Exercise-induced changes in the ST segments of the electrocardiogram were compared with the results of coronary arteriography in 73 consecutive patients referred for preoperative evaluation of coronary artery disease. Eighteen patients had single-, 25 double-, and 30 triple-vessel disease. Thirteen were taking digitalis alone, 28 were taking beta blockers alone, 21 had beta blockers and digitalis and 11 had no cardiac drugs. Exercise induced elevation of the ST segment in 11 patients, all with a predominant lesion in the left anterior descending coronary artery. ST depression with an upsloping ST segment was observed in patients with one-, two-, and three-vessel disease and it was the most common type of ST change in patients with single-vessel disease. Horizontal ST depression was most common in two-vessel disease and downsloping ST segment in three-vessel disease. There was a good correlation between the number of stenosed vessels and ST changes caused by exercise, expressed as the sum of ST segment displacements in twelve leads recorded immediately after the end of exercise (sigma/ST/) or as ST depression per unit increase in heart rate during exercise ("m" (ST/HR]. The latter was obtained by linear regression of ST displacement and heart rate measured at three or four different workloads in the lead with the greatest displacement of the ST segment. The mean values of sigma/ST/ were 0.58 +- 0.030 mV in single-vessel, 0.97 +- 0.41 mV in double-vessel and 1.58 +- 0. 46 mV in triple-vessel disease. The mean values of "m" (ST/HR) were 0.0024 +- 0.0013 mV X min-1 X beat-1 in single-vessel, 0.0042 +- 0.0012 in double-vessel, and 0.0078 +- 0.0033 in triple-vessel disease. These differences were highly significant (p less than 0.01 - 0.001) and there was only minimal overlap between the single- and triple-vessel groups. Digitalis caused a slight (statistically nonsignificant) increase in sigma/ST/ but not in "m" (ST/HR).