Sluggish Upstroke of Signal-Averaged QRS Complex. An Arrhythmogenic Sign in Patients with Anteroseptal Myocardial Infarction

Abstract

Non-invasive recording of the late potential (LP) by signal-averaging technique is useful in predicting ventricular tachycardia (VT), especially in patients with myocardial infarction (MI). However, the rate of positive LP is much lower in anterior or anteroseptal MI than inferior MI since the LP is sometimes masked by QRS complex. The purpose of the present study is firstly, to detect local conduction delay in initial portion of QRS complex and secondarily, to evaluate the clinical significance of the initial delay in patients with MI. Eighty patients with MI were analyzed in 4 groups as follows: AS: anteroseptal, n = 18, including 6 VT; A: anterior, n = 22, 7 VT; I: inferior, n = 28, 9 VT; and P: posterior, n = 12, noVT. Twenty non-MI patients were used as normal controls (N). A signal processor (NEC 7T 18) was used to record signal-averaged electrocardiograms and each 10 msec integral value of filtered QRS complex from the initial upstroke to the 60 msec point was automatically measured. The integral values of groups AS and A were lower than those of groups I, P, and N. AS patients with VT showed a lower integral value than AS patients without VT, but no differences were observed between A patients with VT and A patients without VT. We conclude that there is a much more sluggish upstroke in the signal-averaged initial QRS complex in anteroseptal MI patients with VT, suggesting that the local conduction delay at the ventricular septum plays an important role in the mechanism of VT in these patients.

Keywords

• Signal-averaged electrocardiogram
• Late potential
• Initial delay
• Acute myocardial infarction
• Ventricular tachycardia