Relation Between the Initial Portion of the Signal-Averaged QRS Complex and Cardiac Function and Infarct Size in Patients With Myocardial Infarction

We analyzed signal-averaged electrocardiograms (ECG) obtained in 50 patients with recent myocardial infarction (RMI: 25 anterior and 25 inferior) and 20 normal subjects to determine the relationship between the initial portion of the signal-averaged QRS complex and cardiac function and infarct size. We examined (1) the root mean square voltage (RMS10-40, μV), (2) the integration (A10-40, μV·msec) at 10-msec intervals over the first 40 msec of the signal-averaged QRS complex, and (3) the intervals (T) of the magnitude of the signal-averaged ECG achieved at 10-μV intervals over the first 40 μV (T10-40, msec). The mean RMS10-40 (p<0.01) and A10-40 (A10, p<0.05; A20-40, p<0.01) were significantly lower and the T10-40 (p<0.01) was significantly longer in RMI patients than in normal subjects. The RMS10-40 (p<0.01) and A10-40 (p<0.05) were significantly lower and the T10-40 (T10,20, p <0.01; T30,40, p<0.05) was significantly longer in patients with anterior RMI patients than in patients with inferior RMI. The A30 Was correlated with the ejection fraction and total creatine kinase (CK) release in all patients (r=0.73, and -0.78, respectively, p<0.001). These results suggest that the A30 may be an important predictor of ventricular dysfunction and infarct size in patients with RMI. (Jpn Circ J 1997; 61: 292 - 298)