Digital computer analysis of the vectorcardiogram of the newborn infant. Quantitative and comparative measurement of three orthogonal lead systems.

Data derived from digital computer analysis of three corrected lead recordings for each of 13 term, normal newborn infants obtained on the first day of life are reported. The Frank, Schmitt SVEC-III, and McFee axial systems recorded the time sequence of ventricular depolarization force orientation in an almost identical manner. The following electrocardiographic measurements are reported for each of the three lead systems: heart rate, P-R interval, QRS and S-T intervals, planar and spatial mean P vectors, successive planar mean instantaneous QRS vectors, maximum QRS spatial vector, maximal rightward and leftward QRS spatial vectors, mean and maximum planar and spatial T vectors, and planar and spatial ventricular gradients. In general, vector quantities during this period of life are of lesser magnitude and more variable in orientation than for older infants and children. Although newborn infant ventricular depolarization forces for the majority are directed anteriorly, to the right, and inferiorly, posterior and superior orientation is not uncommon.