The Two-Step Exercise Electrocardiogram
A Double-Blind Evaluation of Its Use in the Diagnosis of Angina Pectoris
A double-blind study was made to evaluate the two-step exercise electrocardiographic test (Master) as a means of differentiating between anginal and nonanginal chest pain in 100 consecutive patients.
A high percentage of false-positive results in nonanginal cases and a number of false negatives in anginal cases greatly impaired the usefulness of the test for this purpose.
When Master's criterion of an ST depression of 0.5 mm. or more was employed, there were 39 per cent false positives and 12 per cent false negatives.
Stricter criteria progressively diminished the number of false positives, but resulted in increasing numbers of false negatives. Even if 1 mm. or more of ST depression was required, there were 8 per cent false positives and 43 per cent false negatives. There were no false positives only when the ST segment was depressed 2 mm. or more.
Although an ischemic type of ST depression may be more significant for angina pectoris than the J type, in our series ischemic ST depressions also occurred more frequently than the J type in false-positive tests in nonanginal patients.
The new criteria of Master and Rosenfeld were not more satisfactory than the previous criteria recommended.
There are relatively few cases in which an objective two-step test is necessary to aid in the differentiation of anginal and nonanginal pain, since an unequivocal diagnosis of angina pectoris or nonanginal pain was made in 86 per cent of cases independently by at least two observers, on the basis of a single interview, and since this percentage could undoubtedly have been increased by further interviews concerning the effect of effort and of nitroglycerin.
Insofar as confirmation of a clinical diagnosis of angina pectoris by an objective exercise test is desirable, an ST-segment depression of at least 1 mm. usually offers such confirmation. However, this degree of ST-segment depression is often absent in unequivocal cases of angina pectoris and conversely may be occasionally present in patients with nonanginal pain.
- © 1962 American Heart Association, Inc.