Experience with the “anoxemia test” in patients with angina pectoris and in those with atypical chest pain

Abstract 1. 1. It should be emphasized again that the presence of a normal electrocardiogram does not rule out angina pectoris. 2. 2. Using the apparatus and technique described by Levy and associates, anoxemia tests were carried out on twenty-six normal subjects, forty patients suffering from typical angina pectoris, forty-six patients with “atypical pain”, and six other subjects. 3. 3. In none of the twenty-six normal subjects was a positive electrocardiographic response recorded. 4. 4. The anoxemia test gave electrocardiographic evidence of coronary insufficiency in 45 per cent of the group with typical angina, compared with 13 per cent of the group with atypical pain. 5. 5. When pain was included, the test gave evidence of coronary insufficiency in 73 per cent of the group with angina, and in only 40 per cent of the group with atypical pain. 6. 6. Although only 13 per cent of the atypical cases had positive electrocardiographic changes with anoxemia, 27 per cent experienced pain, which was approximately the same as the pain in those with typical angina; this suggests the possibility that pain of an origin other than coronary disease may be aggravated by anoxemia. 7. 7. In 32 per cent of the patients with symptomatically and therapeutically typical angina pectoris, this test failed to elicit changes under the prevailing conditions, and in 71 per cent of the group with atypical pain the results were equivocal. 8. 8. If a patient has typical angina pectoris clinically, our experience leads us to accept the clinical impression, although the anoxemia test is negative. 9. 9. Hypertension had no apparent effect in statistically increasing the incidence of coronary insufficiency in the group with typical pain, but in the group with atypical pain the reverse was true. 10. 10. The presence of enlargement of the heart in patients with atypical pain increased the likelihood of a cardiac origin of the discomfort. 11. 11. The presence of both hypertension and cardiac enlargement in the group with atypical pain increased the incidence of positive tests, which was the opposite of the results in the group with typical angina. 12. 12. The anoxemia test when electrocardiographically positive can be used as a means of substantiating the diagnosis of coronary insufficiency, and in certain cases, is useful in the differential diagnosis of atypical pain. 13. 13. When patients experience pain during the test but do not have an electrocardiographically positive test, the following factors should be considered in evaluating the weight to be given this manifestation: The similarity of the pain to the spontaneous pain, its prompt occurrence within a short time after beginning of the test, and the nature and reality of the pain as determined by observation of the patient during the occurrence of the pain. Under certain circumstances weight might be given to pain as presumptive evidence of coronary insufficiency. A positive electrocardiographic test, however, is more significant than a negative one, and more significant than the occurrence of pain. We agree with Levy and his associates that weight should not be given to pain alone in instances when the payment of insurance is involved. 14. 14. The anoxemia test can be used as a method of studying the effect of drugs on the coronary circulation. 15. 15. In certain instances when the anoxemia test is negative, the exercise test may be positive. Great care must be used in subjecting patients to exercise to the point of inducing pain. 16. 16. There were no serious reactions from the judicious use of the test. However, it should not be performed in every patient. Contraindications to the test are congenital heart disease, rheumatic heart disease with valvular damage, pregnancy, myxedema, epilepsy, marked emphysema or other pulmonary disease, severe anemia, and a recent coronary occlusion (within six months). If there is any evidence of congestive failure the test is definitely contraindicated. 17. 17. Our experience with the anoxemia test has paralleled that of others.