Praecordial ECG mapping in acute anterior myocardial infarction. The evolution of ST segment and Q and R waves

Praecordial ECG mapping (42 leads) was carried out in 16 patients with anterior myocardial infarction, admitted up to 3 hours after the onset of symptoms. The mappings were performed according to a set time schedule throughout the acute phase and one year after the infarction. For each ECG map the number of leads with ST elevation greater than or equal to 1.5 mm (NST) and the sum of these (epsilon ST) were calculated. In addition, the sum of Q amplitudes (epsilon Q) and R amplitudes (epsilon R) were determined. On average, the initial epsilon ST elevation decreased from 2 to 8 hours. A secondary increase, occurring in 14 patients, was maximal during days 2-5. Based on the appearance function of creatine kinase in plasma and the QRS alterations, it is suggested that this re-elevation of the St segment was due to infarct extension (5 pats.) or expansion (9 pats.). The course of the average NST was similar to epsilon ST. epsilon Q began to develop at 3 hours, the maximum deflection being reached after about 24 hours (range 8-45). epsilon R was falling at 2 hours; the maximum rate of decrease occurred, on average, within the first 24 hours (range 12-54). One year after the infarction, both epsilon Q and epsilon R had the same level as at 8 hours. The ST elevation at 4 hours was related to the development of Q and R waves within 24 hours, but only a weak or no correlation was found. Thus, there was very little value in predicting the development of QR changes from the ST elevation at 4 hours.