[The electrocardiographic signal of the initial potential detected by signal averaged electrocardiogram]

Non invasive recording of late potential (LP) by signal-averaged electrocardiogram (SAE) is useful in predicting ventricular tachycardia (VT) especially in patients with myocardial infarction (MI). However, the rate of positive LP is not high enough to get clinical significance in anterior or anteroseptal MI, since the LP has been masked by QRS complex. The purpose of the present study is, to evaluate the clinical significance of the initial delay in patients with MI. 80 patients of MI were divided into four groups: AS (anteroseptal, n = 18, including 6 VT), A: (anterior, n = 22.7 VT), I: (inferior, n = 28.9 VT) and P: (posterior, n = 12, no VT). 20 non-MI patients were used for normal control (N). NEC7T18 was used to record SAE and each 5 msec integral values of filtered QRS complex from the initial upstroke to 60 msec point was measured. Integral values of AS and A were significantly lower than that of group I, P, and N. In patients with VT, AS shows more delay than A. In addition, AS with VT shows lower integral value than AS without VT, however no differences were observed between A with VT and without VT. We conclude that slow upstroke of signal-averaged QRS complex was mainly observed in patients of anteroseptal MI with VT, suggesting the initial conduction delay at ventricular septum may play an important role in the mechanism of VT.