CLINICAL PROGRESS The Electrocardiogram during Exercise Its Value in the Diagnosis of Angina Pectoris

though fairly simple in the characteristic case, may not be made with certainty under a variety of conditions. In approximately 50 per cent of cases the diagnosis is made chiefly from the history, since objective evidence of myocardial abnormality may be lacking in the early stage. In the absence of a characteristic history, the difficulty in diagnosis may arise from atypical location of pain and simulation or association of angina with functional or extracardiac conditions. To make a definite diagnosis, we often need all the aids at our disposal. The purpose of this communication is to discuss critically the value of the electrocardiogram in diagno-sis and particularly to evaluate the informa-tion obtained during as well as after exercise. We have performed exercise tests both during and after exercise in nearly 4,500 normal subjects and patients with various cardiac abnormalities in the past 4 years (table 1). Many improvements in the record-ing technics have been made during this period, e.g., in the type of electrodes, electrode placement, the transmitter, and the receiving apparatus. Variations in results have been reported because of differences in apparatus employed, in electrode placement, and in the criteria of positive findings