Abstract
The tentative conclusions below are based upon a study of the electrocardiograms in 56 cases of coronary thrombosis, in 17 of which a post-mortem examination of the heart was made.
The electrocardiogram is of great value in the diagnosis of this condition, particularly when it is possible to obtain a series of curves.
The most important feature of the abnormal T-deflections (described by Smith, 1 Pardee 2 and others) that occur in cardiac infarction is the characteristic and progressive change in form which they undergo. These changes in the T-deflection are usually accompanied by changes in the form of the initial deflections (QRS) which have not been fully described although the large Q-waves that frequently occur in lead III have received considerable attention (W. J. Wilson, 3 Parkinson and Bedford, 4 Levine and Brown, 5 Pardee 6 ). The curves may be divided into 2 groups:
(a) In typical curves of the first group the initial ventricular deflections of lead I are usually of small or medium amplitude, and there is a broad and conspicuous Q-deflection in this lead. In leads II and III the first initial deflection is upward and is followed by an S-wave, often of large amplitude. These changes in QRS occur early and commonly outlast the T-wave changes that accompany them. In the early stages of cardiac infarction there is, in curves belonging to this group, an elevation of the S-T segment in lead I and a depression of this segment in lead III. This partial fusion of R and T in the first lead and of S and T in the third often gives rise to curves which resemble in general outline the monophasic responses yielded by injured heart muscle, as Clarke and Smith 7 have pointed out.
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