Signal-averaged electrocardiography in normal newborn infants.

Signal-averaged electrocardiograms (SAECGs) were recorded with bipolar orthogonal and standard 12-lead settings in 29 term healthy newborn infants. SAECGs performed with the two lead configurations were similar in quality and quantity. For the duration of the QRS complex (QRSD), the upper limit of normality for newborn infants can be set to 100 ms. It is similar in individual bipolar orthogonal and individual standard 12-lead recordings as well as in filtered QRSD in the vectorcardiograms (the vector magnitude, VM, and the sum of extremity leads). In individual leads of bipolar orthogonal and standard 12-lead recordings, root-mean-square voltage of the terminal 40 ms of the QRS complex (RMS40) is widely scattered and unsuitable as discriminant variable. For VM and the sum of the extremity leads, the same reference values for RMS40 and duration of low-amplitude signal can be used as applied in adults. Individual lead recordings provide complementary information in addition to vectorcardiograms. There are practical advantages using standard 12-lead compared to conventional bipolar orthogonal configurations. The widespread use of standard 12-lead ECG in routine medical practice makes its utility advantageous also in performing signal-averaged electrocardiography.