ELECTROCARDIOGRAPHIC CHANGES AFTER ANOXAeMIA AND EXERCISE IN ANGINA OF EFFORT

Significant changes in the four lead electrocardiogram occur in two-thirds of all cases with angina of effort.This investigation shows that anoxaemia or exercise causes a temporary abnormal change in the electrocardiogram and reduces the number of those with effort angina but with no electrocardiographic abnormality to about 18 per cent.Details of the Anoxacmia Test.-The subject reclines on a couch and a four lead electrocardiogram is taken, using chest leads IV R and IV F. A close- fitting mask, having inlet and outlet valves and tubes, is strapped to the face.10 per cent oxygen is inhaled from a rubber bag for three to five minutes.In some of the earlier experiments we used 12 per cent oxygen for ten or fifteen minutes, but it was found that 12 per cent oxygen did not produce anoxemia sufficiently quickly.After inhalation for two and a half minutes the tracing was taken with the inhalation continuing; it usually needed two minutes to take, and it was an advantage to have two operators, one to take the tracing and one to regulate the oxygen apparatus and change the leads.100 per cent oxygen was then given for a minute and the mask removed; fifteen to twenty minutes later another tracing was taken.The Exercise Test.-The subject walked rapidly up and down a long passage and, in many cases, a short flight of stairs was included.After five or ten minutes of this exercise, a tracing was taken.Usually in the anginal cases the exercise was continued until chest pain occurred.Very much more severe exercise was given to the control cases. RESULTS ControlGroup.-Ten controls consisted of seven normal, healthy medical students, two cases of well-compensated valvular disease, and one case of left mammary pain without organic heart disease.They showed no RS-T changes or T wave inversion.A diphasic T3 developed in one and the voltage of the T waves was reduced in five.The details were as follows:69