Maximum Treadmill Exercise Test in Patients with Abnormal Control Electrocardiograms

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Abstract
To determine the validity and safety of exercise induced ST changes (1 mm ischemic depression or further depression in ECG lead V5) as an indication of coronary artery disease (CAD) in patients with abnormal control electrocardiograms (ECG), 121 such patients were compared to 57 patients with a normal control ECG. All underwent a maximum graded treadmill exercise test and coronary arteriography. Among those patients with normal control ECGs, there were no false positives and five false negatives (sensitivity-85%, specificity-100%). In 61 patients with abnormal ECG (no drug therapy except nitrates) there were four false positives and nine false negatives (sensitivity-76%, specificity-79%). In this group of patients T waves reverted from negative to positive in four patients with CAD and 10 patients with no CAD, but T inversion during exercise only occurred in those with CAD (6 patients). Three of 12 patients (25%) with ECG evidence of old infarction and four of eight with single vessel disease had false negative tests. In 60 patients with abnormal ECG on drug therapy there were 10 false positives (17%) and 15 false negatives (sensitivity-55%, specificity-63%). Not helpful in differentiation were resting T vs ST changes, induction of arrhythmias or exercise induced chest pain. The validity of exercise induced ST changes in differentiating CAD is excellent when the control ECG is normal and is only slightly reduced with control ST-T wave abnormalities. When the latter occur in association with cardiovascular drug therapy, other than nitrates, the exercise ECG is of no use in differential diagnosis although still valid and safe for the determination of exercise tolerance.