Left ventricular function after myocardial infarction: Relation between systolic time intervals and quantitative ischaemic ECG changes

Twentyfour male patients with sustained myocardial infarction (MI) were studied with 12‐lead ECG and systolic time intervals (STI) 5 months after the acute episode. From the ECGs were calculated the summed voltages of the R wave (σR), the Q wave (σQ), and the ST segment deviation (σST). These ischaemic ECG variables were correlated with the STI parameters of left ventricular function: LVETI, PEP and PEP/LVET. Statistically significant regression equations relating the ECG changes to the STI variables were found in anterior MI, for σST in the entire series, but not in inferior MI. Thus a simple and rapid inspection of the resting 12‐lead ECG gives an indirect but reliable quantitative estimate of left ventricular function in patients with a sustained myocardial infarction. Experimental studies have shown a relation between QRS changes in the ECG and the size of myocardial infarction (MI) (11, 21). As the extent of myocardial damage after MI determines the impairment of left ventricular (LV) function (14, 20, 25), a correlation between QRS changes and the LV performance would be expected. Linear correlation between the summed R wave voltages (σR) and the number of Q waves (Q index), and the angiographically determined LV ejection fraction has been reported in patients with chronic ischaemic heart disease (2, 4). This study looked for a quantitative correlation between the LV performance, as reflected by various systolic time intervals (STI), and ischaemic ECG changes (σR, σQ, and σST) in a group of patients with previous MI.