[Body surface distribution of the signal-averaged ECG in patients with previous myocardial infarction].

Signal-averaged electrocardiograms (SAEs) were recorded from 28 unipolar leads placed on the upper body in patients with previous myocardial infarction (MI). We measured the filtered QRS duration (fQRSd) for each lead to obtain a new parameter, called a "departure ratio (DR)". The DR was the standardized difference between the fQRSd of a patient and the mean fQRSd obtained in the healthy controls in each of the 28 leads. A DR map was then constructed using the DR. Patients with sustained ventricular tachycardia (VT) demonstrated a small negative area surrounded by dense, positive iso-DR lines and/or a large maximum. These features were located on the left anterior chest through the left back in patients with anterior MI and on the right lateral to the right anterior chest in patients with inferior MI. Both of these characteristic patterns in the area corresponding to the infarct site were present in few patients without VT. These characteristic patterns were highly correlated with the occurrence of sustained VT, suggesting that the characteristics of the DR map represent the body surface manifestation of delayed excitation conduction which can be a sustained VT substrate. Our results indicate that the DR map based on the fQRSd on SAE provides useful information that could not be obtained from vector magnitude analysis.