Value of analysis of the evolution of the pattern of the ST segment in exercise electrocardiograms.

We analysed retrospectively the exercise electrocardiogram records of all patients with positive exercise tests which, on subsequent coronary angiography, proved to be "false positives". The exercise records of 10 "false positive" patients were compared with the records of 10 patients with true positive tests in the setting of single vessel disease and 20 patients with true positive tests and multivessel disease. Patients proving to be false positives did not differ from those with true positive tests in respect to either the slope of the ST segment, the number and site of leads showing shift of the ST segment, or the peak exercise double product. The total duration of exercise, however, was significantly longer in patients having false positive tests (7.93 minutes SD 1.34) as compared to true positive results (5.95 minutes SD 1.9 in single vessel disease, and 4.4 minutes SD 2.2 in multivessel disease, P = less than 0.05). Eight of 10 patients having a false positive test showed an atypical evolution of the pattern of the ST segment. Seven had rapid normalization of depression of the ST segment immediately after cessation of exercise, while one showed shift of the ST segment only during the period of recovery. In contrast, 28 of 30 patients with true positive tests showed gradual normalization of the depressed ST segment during the period of recovery. We conclude that shifts in the ST segment that normalize rapidly on cessation of exercise are frequently a false positive finding.