R-wave Amplitude Changes During Exercise and Diagnosis of Coronary Artery Disease

To investigate the diagnostic value of exercise-related R wave amplitude changes, the responses of 88 asymptomatic healthy subjects and 40 patients with chest pain and no significant coronary artery diease (CAD) were compared with those of 143 patients with CAD 63 of whom had a previous myocardial infarction. All underwent maximal, multistaged treadmill exercise testing. Of 128 normal subjects 94 (73%) had a decrease in R wave amplitude, 20 (16%) had an increase in amplitude, and 14 (11 %) had no change. Among 143 patients with significant CAD, R wave amplitude increased in 64 (45 %), decreased in 47 (33%) and did not change in 32 (22 %). When an increase or no change in R wave was taken as evidence of an abnormal response, the sensitivity was 67 % and specificity 68 %. The sensitivity and specificity of ST segment criterion was 68% and 80 %, respectively. When both criteria were combined, the sensitivity increased to 89.5% while the specificity decreased to 58 %. With respect to abnormal response in R wave amplitude, the difference between patient groups with one-two-or three-vessel disease was not significant. R wave amplitude increased or did not change in 77% of patients with left ventricular hypokinesia, while 59% of patients with normal function had an increase or no change in R wave (p<0.05). It is concluded that the sensitivity and diagnotic accuracy of R wave criterion is as much as that of ST segment's but its specificity is lower. The combination of both criteria may increase the sensitivity, decrease the specificity with respect to ST segment criterion without a significant change in diagnostic accuracy. Thus R wave response to exercise is not considered contributory to the ST segment criterion in the diagnosis of CAD.