Precordial ST—Segment mapping: 6. Evaluation of serial changes in ST‐segment elevations and QRS complexes of precordial maps and standard ECGs in patients with acute myocardial infarction

A total of 21 patients, 10 with anterior and 11 with inferior myocardial infarction (MI) had serial precordial 49‐lead ECG maps or standard ECGs on admission, and 2, 6, 12, 24 hours, and 7 days thereafter, to evaluate the natural course of ST‐segment elevation (index of ischemic injury) and QRS changes (index of necrosis), and their relationship. ECG parameters used included the sum of ST‐segment elevations, number of sites showing such changes, the sum of R waves from all leads with ST‐segment elevations, and a QRS score of all leads showing ischemic injury on admission. Sums of ST‐segment elevations either did not show statistically significant change throughout the study or showed unexplained re‐elevation (anterior MI), or completed their downward course in 6 hours (inferior MI). The number of sites showing ST‐segment elevations either remained unchanged (inferior MI), or declined at 2 hours without further change. However changes in the sum of R waves or QRS scores were gradual and completed most of their overall course within 24 hours. Decline of sums of R waves correlated well with sums of ST‐segment elevations on admission (inferior MI), and the number of sites showing changes (anterior MI). The course of changes in QRS complexes is more reliable than the alterations of ST‐segment elevations for the monitoring of evolution of MI. The former, assessed frequently in the first 24 hours, should be useful in the evaluation of therapies for patients with MI.