The “anoxemia test” in the diagnosis of coronary insufficiency

Abstract 1. 1. Using an apparatus and a technique previously described, anoxemia tests were performed on 115 normal persons and 147 patients with suspected or manifest cardiac disease. In all, 326 tests have been carried out on 262 subjects, in the course of which 2,316 electrocardiograms were taken. 2. 2. In normal persons, the changes in the form of the electrocardiogram during anoxemia are relatively slight. There is usually lowering of the amplitude of the T waves in all of the four leads. There may be inversion of the T wave in Leads II and III. 3. 3. Criteria have been established for an abnormal response. These criteria are sufficiently rigid to exclude alterations in the form of the electrocardiogram which may occur as the result of emotion or other spontaneous variables. 4. 4. The test was positive in 18 per cent of 33 patients with suspected coronary sclerosis; in 31 per cent of twenty-two patients with coronary sclerosis but no history of anginal attacks; in 55 per cent of seventy-three patients with coronary sclerosis and a history of anginal attacks; and in only 5 per cent (one casc) of nineteen patients with hypertension without symptoms or signs of coronary sclerosis. Patients whose control electrocardiogram was abnormal showed a higher percentage of positive tests than those with a normal control tracing. The highest incidence of positive tests was obtained in a group of forty-nine patients with anginal pain caused by coronary sclerosis and abnormal control electrocardiograms; in 69 per cent of these an abnormal response was obtained. 5. 5. There was no relationship between the size of the heart and the incidence of positive tests. 6. 6. There was no constant effect on pulse rate and blood pressure. 7. 7. There was no constant relationship between the occurrence of a positive test and the appearance of pain during anoxemia. 8. 8. No serious untoward effects were observed, provided the test was not carried out when congestive failure was present, was not done more than once on the same patient within twenty-four hours, and was not made before the lapse of four months after an attack of coronary occlusion. 9. 9. Unpleasant reactions were encountered twenty-four times in seventeen cases. These were classified as vasovagal attacks, convulsions, hyperventilation, dyspnea, and mental confusion. None of these reactions was serious or harmful. 10. 10. Nine of the patients in the group died at varying intervals following the test. Necropsies were performed on two. In one case in which the test had been positive, narrowing of the circumflex branch of the left coronary artery and widespread fibrosis of the posterior wall of the left ventricle were found. The heart of the second patient, who had had an attack of coronary thrombosis 5 years before his death from post-operative peritonitis, showed old occlusion of the anterior descending and circumflex branches of the left coronary artery, with healed infarcts of the heart. In this case, the anoxemia test, done eight months before death, was negative. 11. 11. A negative test does not rule out the possibility of early coronary lesions or of healed cardiac infarction. Some of the reasons for the high incidence of negative tests in cases of suspected or known coronary sclerosis have been discussed. 12. 12. The test is simple and safe. When positive, it is a sign of coronary insufficiency and indicates a diminished coronary reserve. 13. 13. The test has proved to be of diagnostic value in distinguishing pain of coronary origin from that due to other causes. It has been useful in affording a graphic record of the efficiency of the coronary circulation at varying intervals following coronary occlusion. It has afforded a method for studying, in patients, the effect of various drugs on the coronary circulation. 14. 14. It is suggested that it may be employed as a measure of the effectiveness of the establishment of collaterals in the coronary bed following surgical operations designed to promote their formation. 15. 15. It may prove useful in cases in which disability is claimed because of anginal pain, and also in insurance examinations when coronary sclerosis is suspected. 16. 16. Only a positive result should be regarded as significant.