Spatial parameters and shape factors of the normal atrial vectorcardiogram and its scalar components

New quantitative norms for clinical evaluation of the atrial vectorcardiogram are presented. Real-time computer processing digitizes atrial electrocardiograms, reduces random noise content, rectifies base-line configuration, and corrects preamplifier distortion. Axial-system leads of 106 normal persons were so treated. The basic information derived includes spatial distribution and magnitudes of P, T P , and polar P vectors; length, width, and planarity of P loops; spatial P-T P angles; and the Eulerian angles of P-loop normalization. Normal P vectors show predominant leftward, inferior, and anterior orientation, with opposing T P direction. Polar P vectors show predominant superior, anterior, and leftward clustering. The scatter of parameters in the orthogonallead frontal plane is about the same as for the tetrahedral system. Similarly, the atrial deflections of normals show equally rich notching in both systems. Resolution of the P-wave population into uncorrelated components, followed by resynthesis from these principal factor wave forms, revealed a fairly continuous "spectrum" of signal configurations. This technique, and extensive attempts by alternate means, failed to support the view that normal P waves can be separated into distinctive right and left atrial components.